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devel / comp.arch.fpga / PCB Layout for BGAs

SubjectAuthor
* PCB Layout for BGAsgnuarm.del...@gmail.com
+* Re: PCB Layout for BGAsDavid Brown
|`* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
| `* Re: PCB Layout for BGAsDavid Brown
|  `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|   `* Re: PCB Layout for BGAsDavid Brown
|    `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     +* Re: PCB Layout for BGAsStef
|     |`* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     | +* Re: PCB Layout for BGAsStef
|     | |`* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     | | `* Re: PCB Layout for BGAsjan Coombs
|     | |  `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     | |   `* Re: PCB Layout for BGAsDavid Brown
|     | |    `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     | |     `- Re: PCB Layout for BGAsDavid Brown
|     | `* Re: PCB Layout for BGAsMichael Schwingen
|     |  `- Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     `* Re: PCB Layout for BGAsMichael Schwingen
|      `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|       +* Re: PCB Layout for BGAsDavid Brown
|       |`* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|       | `- Re: PCB Layout for BGAsDavid Brown
|       `* Re: PCB Layout for BGAsMichael Schwingen
|        `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|         `* Re: PCB Layout for BGAsMichael Schwingen
|          `- Re: PCB Layout for BGAsDavid Brown
+- Re: PCB Layout for BGAsTheo
+* Re: PCB Layout for BGAsJohn Larkin
|`* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
| `* Re: PCB Layout for BGAsJohn Larkin
|  `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|   `* Re: PCB Layout for BGAsJohn Larkin
|    `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     +* Re: PCB Layout for BGAsRichard Damon
|     |`* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|     | `- Re: PCB Layout for BGAsRichard Damon
|     `* Re: PCB Layout for BGAsJohn Larkin
|      `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|       `* Re: PCB Layout for BGAsJohn Larkin
|        `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|         `* Re: PCB Layout for BGAsJohn Larkin
|          `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|           `* Re: PCB Layout for BGAsJohn Larkin
|            `* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
|             `- Re: PCB Layout for BGAsJohn Larkin
`* Re: PCB Layout for BGAsMike Randelzhofer
 +* Re: PCB Layout for BGAsgnuarm.del...@gmail.com
 |`- Re: PCB Layout for BGAsgnuarm.del...@gmail.com
 `- Re: PCB Layout for BGAsDavid Brown

Pages:12
PCB Layout for BGAs

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Subject: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
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 by: gnuarm.del...@gmail. - Sat, 7 Jan 2023 17:49 UTC

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said "no" to the 100% Chinese brand... US government customers, ya know!

So now I'm looking at a BGA. I don't want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don't know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I'd rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory..

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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From: david.br...@hesbynett.no (David Brown)
Newsgroups: comp.arch.fpga
Subject: Re: PCB Layout for BGAs
Date: Sun, 8 Jan 2023 13:51:57 +0100
Organization: A noiseless patient Spider
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 by: David Brown - Sun, 8 Jan 2023 12:51 UTC

On 07/01/2023 18:49, gnuarm.del...@gmail.com wrote:
> A small board with a 100QFP is being redesigned for a new FPGA due to
> obsolescence. Gowin makes a 100QFP device that would be a good fit,
> but my customer has said "no" to the 100% Chinese brand... US
> government customers, ya know!
>
> So now I'm looking at a BGA. I don't want to get into fine PCB
> design rules, so 1.0 mm ball pitch is my preference. The only
> devices I can find that fit on the board have 196 or 256 pins. But
> the real problem is availability.
>
> Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for
> delivery in April. Add in the various speed and temperature flavors
> trickling in (mostly in April) and I should be ok for the initial
> delivery in August... if I can get my hands on those. I don't know
> if Digikey factors in the backlog orders in these counts.
>
> Mouser shows great inventory of Efinix parts, particularly the T13
> and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I'd
> rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part
> numbers, but zero inventory.
>
> Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you
> use? Did this impact the PWB cost?
>

It's difficult to know the impact without knowing details of the board
you have at the moment. It is also somewhat dependent on the layout of
the balls on the part - some BGA's have missing balls, or their central
balls all connected to ground to make layout easier.

In general, 0.8 mm pitch should be doable in four layers, but you might
need finer tracks and clearances than you used before. In a recent
board we did, the 0.8 mm pitch BGA was fine with four layers and normal
vias. We did not need to switch to 6 layers with advanced vias until we
moved to the 0.65 mm version.

Re: PCB Layout for BGAs

<5e48c6c1-a947-4457-830c-2275917af70en@googlegroups.com>

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
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 by: gnuarm.del...@gmail. - Sun, 8 Jan 2023 19:01 UTC

On Sunday, January 8, 2023 at 7:52:02 AM UTC-5, David Brown wrote:
> On 07/01/2023 18:49, gnuarm.del...@gmail.com wrote:
> > A small board with a 100QFP is being redesigned for a new FPGA due to
> > obsolescence. Gowin makes a 100QFP device that would be a good fit,
> > but my customer has said "no" to the 100% Chinese brand... US
> > government customers, ya know!
> >
> > So now I'm looking at a BGA. I don't want to get into fine PCB
> > design rules, so 1.0 mm ball pitch is my preference. The only
> > devices I can find that fit on the board have 196 or 256 pins. But
> > the real problem is availability.
> >
> > Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for
> > delivery in April. Add in the various speed and temperature flavors
> > trickling in (mostly in April) and I should be ok for the initial
> > delivery in August... if I can get my hands on those. I don't know
> > if Digikey factors in the backlog orders in these counts.
> >
> > Mouser shows great inventory of Efinix parts, particularly the T13
> > and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I'd
> > rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part
> > numbers, but zero inventory.
> >
> > Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you
> > use? Did this impact the PWB cost?
> >
> It's difficult to know the impact without knowing details of the board
> you have at the moment. It is also somewhat dependent on the layout of
> the balls on the part - some BGA's have missing balls, or their central
> balls all connected to ground to make layout easier.
>
> In general, 0.8 mm pitch should be doable in four layers, but you might
> need finer tracks and clearances than you used before. In a recent
> board we did, the 0.8 mm pitch BGA was fine with four layers and normal
> vias. We did not need to switch to 6 layers with advanced vias until we
> moved to the 0.65 mm version.

What are "normal" vias and track/space widths? All of the BGAs I'm looking at are solid arrays. I'd give you identifiers of the packages, but I've never found standard terms. Everyone has unique identifiers and more than one! Packaging is insane! I especially love how TI adds it to their data sheets with the reel packing and boxing data ahead of the package mechanical data. I'm sure that stuff is important to someone, but they could have a separate data sheet with all that. Some companies do that with the package mechanical data. Gotta love diversity... or not.

My board is already 6 layers because of the high density and narrow width, 23 mm x 115 mm. One layer is pretty much nothing but lengthwise routing and it's still very congested. Surface layers are hard to route on. Between the parts and the vias, there's no room left. In the new layout, a couple of larger chips are going bye bye, so maybe that will improve things a bit.. But they are asking for some new features that will add some chips, so it may be an even swap.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

<tpgl7e$4tjo$1@dont-email.me>

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From: david.br...@hesbynett.no (David Brown)
Newsgroups: comp.arch.fpga
Subject: Re: PCB Layout for BGAs
Date: Mon, 9 Jan 2023 10:02:38 +0100
Organization: A noiseless patient Spider
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References: <d12cac42-059f-4a0c-8b2e-ebe8488defe3n@googlegroups.com>
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 by: David Brown - Mon, 9 Jan 2023 09:02 UTC

On 08/01/2023 20:01, gnuarm.del...@gmail.com wrote:
> On Sunday, January 8, 2023 at 7:52:02 AM UTC-5, David Brown wrote:
>> On 07/01/2023 18:49, gnuarm.del...@gmail.com wrote:
>>> A small board with a 100QFP is being redesigned for a new FPGA
>>> due to obsolescence. Gowin makes a 100QFP device that would be a
>>> good fit, but my customer has said "no" to the 100% Chinese
>>> brand... US government customers, ya know!
>>>
>>> So now I'm looking at a BGA. I don't want to get into fine PCB
>>> design rules, so 1.0 mm ball pitch is my preference. The only
>>> devices I can find that fit on the board have 196 or 256 pins.
>>> But the real problem is availability.
>>>
>>> Digikey has a few of the XC7S15-1FTGB196I and more a scheduled
>>> for delivery in April. Add in the various speed and temperature
>>> flavors trickling in (mostly in April) and I should be ok for the
>>> initial delivery in August... if I can get my hands on those. I
>>> don't know if Digikey factors in the backlog orders in these
>>> counts.
>>>
>>> Mouser shows great inventory of Efinix parts, particularly the
>>> T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock.
>>> But I'd rather work with a 1.0 mm BGA. Oddly enough, LCSC shows
>>> part numbers, but zero inventory.
>>>
>>> Anyone work with 0.8 mm BGAs? What PWB feature dimensions did
>>> you use? Did this impact the PWB cost?
>>>
>> It's difficult to know the impact without knowing details of the
>> board you have at the moment. It is also somewhat dependent on the
>> layout of the balls on the part - some BGA's have missing balls, or
>> their central balls all connected to ground to make layout easier.
>>
>> In general, 0.8 mm pitch should be doable in four layers, but you
>> might need finer tracks and clearances than you used before. In a
>> recent board we did, the 0.8 mm pitch BGA was fine with four layers
>> and normal vias. We did not need to switch to 6 layers with
>> advanced vias until we moved to the 0.65 mm version.
>
> What are "normal" vias and track/space widths? All of the BGAs I'm
> looking at are solid arrays. I'd give you identifiers of the
> packages, but I've never found standard terms. Everyone has unique
> identifiers and more than one! Packaging is insane! I especially
> love how TI adds it to their data sheets with the reel packing and
> boxing data ahead of the package mechanical data. I'm sure that
> stuff is important to someone, but they could have a separate data
> sheet with all that. Some companies do that with the package
> mechanical data. Gotta love diversity... or not.
>
> My board is already 6 layers because of the high density and narrow
> width, 23 mm x 115 mm. One layer is pretty much nothing but
> lengthwise routing and it's still very congested. Surface layers are
> hard to route on. Between the parts and the vias, there's no room
> left. In the new layout, a couple of larger chips are going bye bye,
> so maybe that will improve things a bit. But they are asking for
> some new features that will add some chips, so it may be an even
> swap.
>

By "normal" vias I mean through-hole, without plugging or tenting - the
cheap ones. And by "normal" track widths and spacing, I mean the
perhaps 6 mil - cheap sizes that any pcb manufacturer can make without
extra charge. Basically, at 0.8 mm BGA we didn't need to do anything
special or consider it an especially high-density card. It was still an
effort to route, as there are a lot of connections in a small area. But
it didn't need extra cost for the pcb.

If you are already congested at 6 layers on the board, then you will
might have to go for beyond that. The first step is to talk to your pcb
and board manufacturers about via-in-pad, using tented or plugged vias.
If you can put the vias on the pads themselves, without causing voids
or blowouts during soldering, you can save a /lot/ of space. Next step
beyond that is microvias from outer layers to layers 2 and 5. We had to
do that for the 0.65 mm package BGA.

Re: PCB Layout for BGAs

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
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 by: gnuarm.del...@gmail. - Mon, 9 Jan 2023 10:42 UTC

On Monday, January 9, 2023 at 4:02:43 AM UTC-5, David Brown wrote:
> On 08/01/2023 20:01, gnuarm.del...@gmail.com wrote:
> > On Sunday, January 8, 2023 at 7:52:02 AM UTC-5, David Brown wrote:
> >> On 07/01/2023 18:49, gnuarm.del...@gmail.com wrote:
> >>> A small board with a 100QFP is being redesigned for a new FPGA
> >>> due to obsolescence. Gowin makes a 100QFP device that would be a
> >>> good fit, but my customer has said "no" to the 100% Chinese
> >>> brand... US government customers, ya know!
> >>>
> >>> So now I'm looking at a BGA. I don't want to get into fine PCB
> >>> design rules, so 1.0 mm ball pitch is my preference. The only
> >>> devices I can find that fit on the board have 196 or 256 pins.
> >>> But the real problem is availability.
> >>>
> >>> Digikey has a few of the XC7S15-1FTGB196I and more a scheduled
> >>> for delivery in April. Add in the various speed and temperature
> >>> flavors trickling in (mostly in April) and I should be ok for the
> >>> initial delivery in August... if I can get my hands on those. I
> >>> don't know if Digikey factors in the backlog orders in these
> >>> counts.
> >>>
> >>> Mouser shows great inventory of Efinix parts, particularly the
> >>> T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock.
> >>> But I'd rather work with a 1.0 mm BGA. Oddly enough, LCSC shows
> >>> part numbers, but zero inventory.
> >>>
> >>> Anyone work with 0.8 mm BGAs? What PWB feature dimensions did
> >>> you use? Did this impact the PWB cost?
> >>>
> >> It's difficult to know the impact without knowing details of the
> >> board you have at the moment. It is also somewhat dependent on the
> >> layout of the balls on the part - some BGA's have missing balls, or
> >> their central balls all connected to ground to make layout easier.
> >>
> >> In general, 0.8 mm pitch should be doable in four layers, but you
> >> might need finer tracks and clearances than you used before. In a
> >> recent board we did, the 0.8 mm pitch BGA was fine with four layers
> >> and normal vias. We did not need to switch to 6 layers with
> >> advanced vias until we moved to the 0.65 mm version.
> >
> > What are "normal" vias and track/space widths? All of the BGAs I'm
> > looking at are solid arrays. I'd give you identifiers of the
> > packages, but I've never found standard terms. Everyone has unique
> > identifiers and more than one! Packaging is insane! I especially
> > love how TI adds it to their data sheets with the reel packing and
> > boxing data ahead of the package mechanical data. I'm sure that
> > stuff is important to someone, but they could have a separate data
> > sheet with all that. Some companies do that with the package
> > mechanical data. Gotta love diversity... or not.
> >
> > My board is already 6 layers because of the high density and narrow
> > width, 23 mm x 115 mm. One layer is pretty much nothing but
> > lengthwise routing and it's still very congested. Surface layers are
> > hard to route on. Between the parts and the vias, there's no room
> > left. In the new layout, a couple of larger chips are going bye bye,
> > so maybe that will improve things a bit. But they are asking for
> > some new features that will add some chips, so it may be an even
> > swap.
> >
> By "normal" vias I mean through-hole, without plugging or tenting - the
> cheap ones. And by "normal" track widths and spacing, I mean the
> perhaps 6 mil - cheap sizes that any pcb manufacturer can make without
> extra charge. Basically, at 0.8 mm BGA we didn't need to do anything
> special or consider it an especially high-density card. It was still an
> effort to route, as there are a lot of connections in a small area. But
> it didn't need extra cost for the pcb.

So you don't know what size ball pad, via pad/drill and trace/space you actually used? I'm finding it a bit harder than I expected to figure out dimensions that work. I'd love to use the Xilinx 196 ball, 1.0 mm pitch part, but they are still pretty hard to get. Efinix has nothing but smaller pitch BGAs. 256 ball, 0.8 mm pitch, or 169 ball, 0.65 mm pitch. 0.65 mm pitch just won't work for me.

> If you are already congested at 6 layers on the board, then you will
> might have to go for beyond that. The first step is to talk to your pcb
> and board manufacturers about via-in-pad, using tented or plugged vias.
> If you can put the vias on the pads themselves, without causing voids
> or blowouts during soldering, you can save a /lot/ of space. Next step
> beyond that is microvias from outer layers to layers 2 and 5. We had to
> do that for the 0.65 mm package BGA.

Absolutely not interested in 0.65 mm pitch, or any of the high density techniques like via in pad.

I can get away with nearly no vias, if I can route two traces between pins. That works at 1.0 mm, but at 0.8 mm, the trace/space has to be pretty small.

JLCPCB lists 0.2 mm drill (8 mil) and 0.45 mm via pads (18 mil). Assuming BGA lands of 0.4 mm means you can route 2 traces between pads only with 0.08 mm (3.2 mil) trace/space. Routing between the via holes is also tight, with trace/space of 0.08 mm (3.2 mil) and 0.13 mm (5.1 mil) (according to Xilinx). I've read elsewhere that the space to the via drill should be 0.2 mm (8 mil) minimum for lower cost boards, so this doesn't sound good for routing two traces. With that restriction, I could only route two rows of pins without vias. Adding vias to escape the BGA makes the entire section of the board a difficult for routing.

Yeah, I'd much prefer to go with a 1.0 mm part like the Xilinx 196 ball Spartan 7 parts. I just don't know if I'll be able to get them.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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From: david.br...@hesbynett.no (David Brown)
Newsgroups: comp.arch.fpga
Subject: Re: PCB Layout for BGAs
Date: Mon, 9 Jan 2023 13:42:14 +0100
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 by: David Brown - Mon, 9 Jan 2023 12:42 UTC

On 09/01/2023 11:42, gnuarm.del...@gmail.com wrote:
> On Monday, January 9, 2023 at 4:02:43 AM UTC-5, David Brown wrote:
>> On 08/01/2023 20:01, gnuarm.del...@gmail.com wrote:
>>> On Sunday, January 8, 2023 at 7:52:02 AM UTC-5, David Brown
>>> wrote:
>>>> On 07/01/2023 18:49, gnuarm.del...@gmail.com wrote:
>>>>> A small board with a 100QFP is being redesigned for a new
>>>>> FPGA due to obsolescence. Gowin makes a 100QFP device that
>>>>> would be a good fit, but my customer has said "no" to the
>>>>> 100% Chinese brand... US government customers, ya know!
>>>>>
>>>>> So now I'm looking at a BGA. I don't want to get into fine
>>>>> PCB design rules, so 1.0 mm ball pitch is my preference. The
>>>>> only devices I can find that fit on the board have 196 or 256
>>>>> pins. But the real problem is availability.
>>>>>
>>>>> Digikey has a few of the XC7S15-1FTGB196I and more a
>>>>> scheduled for delivery in April. Add in the various speed and
>>>>> temperature flavors trickling in (mostly in April) and I
>>>>> should be ok for the initial delivery in August... if I can
>>>>> get my hands on those. I don't know if Digikey factors in the
>>>>> backlog orders in these counts.
>>>>>
>>>>> Mouser shows great inventory of Efinix parts, particularly
>>>>> the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in
>>>>> stock. But I'd rather work with a 1.0 mm BGA. Oddly enough,
>>>>> LCSC shows part numbers, but zero inventory.
>>>>>
>>>>> Anyone work with 0.8 mm BGAs? What PWB feature dimensions
>>>>> did you use? Did this impact the PWB cost?
>>>>>
>>>> It's difficult to know the impact without knowing details of
>>>> the board you have at the moment. It is also somewhat dependent
>>>> on the layout of the balls on the part - some BGA's have
>>>> missing balls, or their central balls all connected to ground
>>>> to make layout easier.
>>>>
>>>> In general, 0.8 mm pitch should be doable in four layers, but
>>>> you might need finer tracks and clearances than you used
>>>> before. In a recent board we did, the 0.8 mm pitch BGA was fine
>>>> with four layers and normal vias. We did not need to switch to
>>>> 6 layers with advanced vias until we moved to the 0.65 mm
>>>> version.
>>>
>>> What are "normal" vias and track/space widths? All of the BGAs
>>> I'm looking at are solid arrays. I'd give you identifiers of the
>>> packages, but I've never found standard terms. Everyone has
>>> unique identifiers and more than one! Packaging is insane! I
>>> especially love how TI adds it to their data sheets with the reel
>>> packing and boxing data ahead of the package mechanical data. I'm
>>> sure that stuff is important to someone, but they could have a
>>> separate data sheet with all that. Some companies do that with
>>> the package mechanical data. Gotta love diversity... or not.
>>>
>>> My board is already 6 layers because of the high density and
>>> narrow width, 23 mm x 115 mm. One layer is pretty much nothing
>>> but lengthwise routing and it's still very congested. Surface
>>> layers are hard to route on. Between the parts and the vias,
>>> there's no room left. In the new layout, a couple of larger chips
>>> are going bye bye, so maybe that will improve things a bit. But
>>> they are asking for some new features that will add some chips,
>>> so it may be an even swap.
>>>
>> By "normal" vias I mean through-hole, without plugging or tenting -
>> the cheap ones. And by "normal" track widths and spacing, I mean
>> the perhaps 6 mil - cheap sizes that any pcb manufacturer can make
>> without extra charge. Basically, at 0.8 mm BGA we didn't need to do
>> anything special or consider it an especially high-density card. It
>> was still an effort to route, as there are a lot of connections in
>> a small area. But it didn't need extra cost for the pcb.
>
> So you don't know what size ball pad, via pad/drill and trace/space
> you actually used? I'm finding it a bit harder than I expected to
> figure out dimensions that work. I'd love to use the Xilinx 196
> ball, 1.0 mm pitch part, but they are still pretty hard to get.
> Efinix has nothing but smaller pitch BGAs. 256 ball, 0.8 mm pitch,
> or 169 ball, 0.65 mm pitch. 0.65 mm pitch just won't work for me.
>

I'm afraid I don't remember the sizes used - I was not directly involved
in the layout and routing. (I've done fine-pitched BGA layout, but it's
probably 15 years since I did a pcb design myself.)

Is it the routing you see as a problem for 0.65 mm pitch, or the cost of
boards with high density features, or the production of them? We have
found that while the 0.65 mm pitch parts were harder for the layout and
a little more expensive for the boards, parts in these packages can be a
lot easier to get hold of. The choice of 0.65 mm or 0.8 mm was forced
by component availability, rather than as a preference by our layout
folk. (Our production people have no qualms about mounting small pitch
BGAs.)

>
>> If you are already congested at 6 layers on the board, then you
>> will might have to go for beyond that. The first step is to talk to
>> your pcb and board manufacturers about via-in-pad, using tented or
>> plugged vias. If you can put the vias on the pads themselves,
>> without causing voids or blowouts during soldering, you can save a
>> /lot/ of space. Next step beyond that is microvias from outer
>> layers to layers 2 and 5. We had to do that for the 0.65 mm package
>> BGA.
>
> Absolutely not interested in 0.65 mm pitch, or any of the high
> density techniques like via in pad.
>
> I can get away with nearly no vias, if I can route two traces between
> pins. That works at 1.0 mm, but at 0.8 mm, the trace/space has to be
> pretty small.
>
> JLCPCB lists 0.2 mm drill (8 mil) and 0.45 mm via pads (18 mil).
> Assuming BGA lands of 0.4 mm means you can route 2 traces between
> pads only with 0.08 mm (3.2 mil) trace/space. Routing between the
> via holes is also tight, with trace/space of 0.08 mm (3.2 mil) and
> 0.13 mm (5.1 mil) (according to Xilinx). I've read elsewhere that
> the space to the via drill should be 0.2 mm (8 mil) minimum for lower
> cost boards, so this doesn't sound good for routing two traces. With
> that restriction, I could only route two rows of pins without vias.
> Adding vias to escape the BGA makes the entire section of the board a
> difficult for routing.
>

Mechanical drilling has a lot bigger tolerances than laser drilling, so
you do need to have extra space between the via hole and tracks on the
internal layers to account for the inaccuracies. Some manufacturers
will give you tighter specifications - in particular, some use lasers
for 0.2 mm holes. (And some, on the other hand, use mechanical drills
and charge extra for 0.2 mm holes due to extra breakage of the small
drill bits.)

> Yeah, I'd much prefer to go with a 1.0 mm part like the Xilinx 196
> ball Spartan 7 parts. I just don't know if I'll be able to get
> them.
>

That's always the big problem these days. I'm afraid I can't give much
advice there (at least, nothing that you won't already have thought of
yourself) - we are all in the same boat.

Re: PCB Layout for BGAs

<DRz*XPW7y@news.chiark.greenend.org.uk>

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From: theom+n...@chiark.greenend.org.uk (Theo)
Newsgroups: comp.arch.fpga
Subject: Re: PCB Layout for BGAs
Date: 09 Jan 2023 14:50:45 +0000 (GMT)
Organization: University of Cambridge, England
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 by: Theo - Mon, 9 Jan 2023 14:50 UTC

gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:
> Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use?
> Did this impact the PWB cost?

I've not done this for real, but I did a bit of playing around with PCB
routing such BGA FPGAs. I was trying to see if it was feasible to use them
on cheap PCB processes with basic soldering (I never actually made any
boards to test it). One of the limitations of cheap processes is the
tolerances can be quite slack: eg 6mil track width/spacing, which makes
doing the BGA escapes hard.

An interesting (to me) observation was that you may be able to make PCB
routing easier by choosing your pinout wisely - eg don't route signals from
inner or adjacent balls where you don't need them. That means it wasn't
such a headache to have more pins because you can ignore many of them. For
some of them, it was fine to short adjacent pins to (safe) power rails if it
wasn't possible to separate them.

Another observation was that it might be fine to have a net route through
unused pins if they're all high impedance in the FPGA config. I'd not do
this for fast signals, but maybe OK for slow/static ones.

Not ideal, but a couple of tricks where FPGAs offer a little bit more PCB
routing flexibility compared with off the shelf parts.

Theo

Re: PCB Layout for BGAs

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 by: gnuarm.del...@gmail. - Mon, 9 Jan 2023 22:46 UTC

On Monday, January 9, 2023 at 7:42:20 AM UTC-5, David Brown wrote:
> On 09/01/2023 11:42, gnuarm.del...@gmail.com wrote:
> > On Monday, January 9, 2023 at 4:02:43 AM UTC-5, David Brown wrote:
> >> On 08/01/2023 20:01, gnuarm.del...@gmail.com wrote:
> >>> On Sunday, January 8, 2023 at 7:52:02 AM UTC-5, David Brown
> >>> wrote:
> >>>> On 07/01/2023 18:49, gnuarm.del...@gmail.com wrote:
> >>>>> A small board with a 100QFP is being redesigned for a new
> >>>>> FPGA due to obsolescence. Gowin makes a 100QFP device that
> >>>>> would be a good fit, but my customer has said "no" to the
> >>>>> 100% Chinese brand... US government customers, ya know!
> >>>>>
> >>>>> So now I'm looking at a BGA. I don't want to get into fine
> >>>>> PCB design rules, so 1.0 mm ball pitch is my preference. The
> >>>>> only devices I can find that fit on the board have 196 or 256
> >>>>> pins. But the real problem is availability.
> >>>>>
> >>>>> Digikey has a few of the XC7S15-1FTGB196I and more a
> >>>>> scheduled for delivery in April. Add in the various speed and
> >>>>> temperature flavors trickling in (mostly in April) and I
> >>>>> should be ok for the initial delivery in August... if I can
> >>>>> get my hands on those. I don't know if Digikey factors in the
> >>>>> backlog orders in these counts.
> >>>>>
> >>>>> Mouser shows great inventory of Efinix parts, particularly
> >>>>> the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in
> >>>>> stock. But I'd rather work with a 1.0 mm BGA. Oddly enough,
> >>>>> LCSC shows part numbers, but zero inventory.
> >>>>>
> >>>>> Anyone work with 0.8 mm BGAs? What PWB feature dimensions
> >>>>> did you use? Did this impact the PWB cost?
> >>>>>
> >>>> It's difficult to know the impact without knowing details of
> >>>> the board you have at the moment. It is also somewhat dependent
> >>>> on the layout of the balls on the part - some BGA's have
> >>>> missing balls, or their central balls all connected to ground
> >>>> to make layout easier.
> >>>>
> >>>> In general, 0.8 mm pitch should be doable in four layers, but
> >>>> you might need finer tracks and clearances than you used
> >>>> before. In a recent board we did, the 0.8 mm pitch BGA was fine
> >>>> with four layers and normal vias. We did not need to switch to
> >>>> 6 layers with advanced vias until we moved to the 0.65 mm
> >>>> version.
> >>>
> >>> What are "normal" vias and track/space widths? All of the BGAs
> >>> I'm looking at are solid arrays. I'd give you identifiers of the
> >>> packages, but I've never found standard terms. Everyone has
> >>> unique identifiers and more than one! Packaging is insane! I
> >>> especially love how TI adds it to their data sheets with the reel
> >>> packing and boxing data ahead of the package mechanical data. I'm
> >>> sure that stuff is important to someone, but they could have a
> >>> separate data sheet with all that. Some companies do that with
> >>> the package mechanical data. Gotta love diversity... or not.
> >>>
> >>> My board is already 6 layers because of the high density and
> >>> narrow width, 23 mm x 115 mm. One layer is pretty much nothing
> >>> but lengthwise routing and it's still very congested. Surface
> >>> layers are hard to route on. Between the parts and the vias,
> >>> there's no room left. In the new layout, a couple of larger chips
> >>> are going bye bye, so maybe that will improve things a bit. But
> >>> they are asking for some new features that will add some chips,
> >>> so it may be an even swap.
> >>>
> >> By "normal" vias I mean through-hole, without plugging or tenting -
> >> the cheap ones. And by "normal" track widths and spacing, I mean
> >> the perhaps 6 mil - cheap sizes that any pcb manufacturer can make
> >> without extra charge. Basically, at 0.8 mm BGA we didn't need to do
> >> anything special or consider it an especially high-density card. It
> >> was still an effort to route, as there are a lot of connections in
> >> a small area. But it didn't need extra cost for the pcb.
> >
> > So you don't know what size ball pad, via pad/drill and trace/space
> > you actually used? I'm finding it a bit harder than I expected to
> > figure out dimensions that work. I'd love to use the Xilinx 196
> > ball, 1.0 mm pitch part, but they are still pretty hard to get.
> > Efinix has nothing but smaller pitch BGAs. 256 ball, 0.8 mm pitch,
> > or 169 ball, 0.65 mm pitch. 0.65 mm pitch just won't work for me.
> >
> I'm afraid I don't remember the sizes used - I was not directly involved
> in the layout and routing. (I've done fine-pitched BGA layout, but it's
> probably 15 years since I did a pcb design myself.)
>
> Is it the routing you see as a problem for 0.65 mm pitch, or the cost of
> boards with high density features, or the production of them? We have
> found that while the 0.65 mm pitch parts were harder for the layout and
> a little more expensive for the boards, parts in these packages can be a
> lot easier to get hold of. The choice of 0.65 mm or 0.8 mm was forced
> by component availability, rather than as a preference by our layout
> folk. (Our production people have no qualms about mounting small pitch
> BGAs.)

I'm trying to be as conservative as possible. I'd rather not use BGAs at all, but the only QFPs I can find that fit on the board are Gowin, which is not on the approved vendor list with my customer. They are too Chinese.

I'm concerned about adding cost for the boards, cost for the assembly and just an easy road forward. I spend the last two years building 8,000 units when the CODEC factory burnt down. The customer knows about this issue, but the previous CM turned flaky on me and all but stopped delivering product..

I have a new CM, but I don't want to go through production problems again.

> >> If you are already congested at 6 layers on the board, then you
> >> will might have to go for beyond that. The first step is to talk to
> >> your pcb and board manufacturers about via-in-pad, using tented or
> >> plugged vias. If you can put the vias on the pads themselves,
> >> without causing voids or blowouts during soldering, you can save a
> >> /lot/ of space. Next step beyond that is microvias from outer
> >> layers to layers 2 and 5. We had to do that for the 0.65 mm package
> >> BGA.
> >
> > Absolutely not interested in 0.65 mm pitch, or any of the high
> > density techniques like via in pad.
> >
> > I can get away with nearly no vias, if I can route two traces between
> > pins. That works at 1.0 mm, but at 0.8 mm, the trace/space has to be
> > pretty small.
> >
> > JLCPCB lists 0.2 mm drill (8 mil) and 0.45 mm via pads (18 mil).
> > Assuming BGA lands of 0.4 mm means you can route 2 traces between
> > pads only with 0.08 mm (3.2 mil) trace/space. Routing between the
> > via holes is also tight, with trace/space of 0.08 mm (3.2 mil) and
> > 0.13 mm (5.1 mil) (according to Xilinx). I've read elsewhere that
> > the space to the via drill should be 0.2 mm (8 mil) minimum for lower
> > cost boards, so this doesn't sound good for routing two traces. With
> > that restriction, I could only route two rows of pins without vias.
> > Adding vias to escape the BGA makes the entire section of the board a
> > difficult for routing.
> >
> Mechanical drilling has a lot bigger tolerances than laser drilling, so
> you do need to have extra space between the via hole and tracks on the
> internal layers to account for the inaccuracies. Some manufacturers
> will give you tighter specifications - in particular, some use lasers
> for 0.2 mm holes. (And some, on the other hand, use mechanical drills
> and charge extra for 0.2 mm holes due to extra breakage of the small
> drill bits.)

JLCPCB does 0.2 mm holes without extra charge, along with 0.45 mm via pads. They charge a bit extra for 0.4 mm pads. I guess it makes for a smaller target. I look at various PCB maker's pages to see what they state they can do.


Click here to read the complete article
Re: PCB Layout for BGAs

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 by: Stef - Tue, 10 Jan 2023 00:30 UTC

On 2023-01-09 gnuarm.del...@gmail.com wrote in comp.arch.fpga:
>
> I'm trying to be as conservative as possible. I'd rather not use BGAs at all, but the only QFPs I can find that fit on the board are Gowin, which is not on the approved vendor list with my customer. They are too Chinese.
>

Digikey has a number of FPGAs in QFP100/144 in stock. Efinix,
Microchip, Lattice, Xilinx. Nothing that suits your needs?

--
Stef

Kinkler's First Law:
Responsibility always exceeds authority.

Kinkler's Second Law:
All the easy problems have been solved.

Re: PCB Layout for BGAs

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
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 by: gnuarm.del...@gmail. - Tue, 10 Jan 2023 01:59 UTC

On Monday, January 9, 2023 at 7:30:34 PM UTC-5, Stef wrote:
> On 2023-01-09 gnuarm.del...@gmail.com wrote in comp.arch.fpga:
> >
> > I'm trying to be as conservative as possible. I'd rather not use BGAs at all, but the only QFPs I can find that fit on the board are Gowin, which is not on the approved vendor list with my customer. They are too Chinese.
> >
> Digikey has a number of FPGAs in QFP100/144 in stock. Efinix,
> Microchip, Lattice, Xilinx. Nothing that suits your needs?

The QFP144 is far too large. Efinix has no QFP100 parts. Lattice has no QFP100 parts that I've seen since the LFXP parts revision 2.0 of my board used. Xilinx has not had any in decades, unless you mean the very small, yet expensive CPLD thing they sell. Microchip might have some QFP100 parts in one of their older lines that I'm not so familiar with. I believe their logic cells can be either logic, or FFs, but not both. So you need roughly double the count, if not more. They are very expensive too. I've never been inclined to research such an old product, much like the Spartan 3. I get that in a QFP100, but how long will they continue to make Spartan 3 devices... which have also climbed significantly in price. It's what is called NRND. Gowin would have been perfect, but at one point they were put on a US list of CCMC (Communist Chinese Military Companies). Even though they were taken off, my customer sells a lot to the US government, so they don't like the "optics".

Did I miss any?

Trust me, I've been traveling this road for the last eight years from when Lattice first announced the end of the line for the LFXP parts. Surprisingly, I noticed the other day that Arrow, who invested heavily in the line when Lattice announced EOL, still has almost 30,000 of them. In theory, I could continue to use those, but I do expect to sell more than 30,000 over the next 10 years. In fact, I am going to turn this over to a CM, who will in turn, pay me a royalty for every unit shipped. Other than consulting, I will be out of the business, but still receive payments for everything sold.. I won't be the guy worrying about where to find what part!

At this point, I'd be happy with the Xilinx XC7S15-1FTGB196I. Digikey has over 800 in stock which is more than half of what I need. They claim they will have the rest by April. I just don't know how to get on the list to receive them. I guess the fact that they have inventory, means no one is in line to get the April lot. I really need to talk to someone who can give me straight answers about the future availability though. It would not help to design in a part that let's me ship the first order, then not receive any parts for the next year!

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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 by: Stef - Tue, 10 Jan 2023 08:52 UTC

On 2023-01-10 gnuarm.del...@gmail.com wrote in comp.arch.fpga:
> On Monday, January 9, 2023 at 7:30:34 PM UTC-5, Stef wrote:
>> On 2023-01-09 gnuarm.del...@gmail.com wrote in comp.arch.fpga:
>> >
>> > I'm trying to be as conservative as possible. I'd rather not use BGAs at all, but the only QFPs I can find that fit on the board are Gowin, which is not on the approved vendor list with my customer. They are too Chinese.
>> >
>> Digikey has a number of FPGAs in QFP100/144 in stock. Efinix,
>> Microchip, Lattice, Xilinx. Nothing that suits your needs?
>
> The QFP144 is far too large. Efinix has no QFP100 parts. Lattice has no QFP100 parts that I've seen since the LFXP parts revision 2.0 of my board used. Xilinx has not had any in decades, unless you mean the very small, yet expensive CPLD thing they sell. Microchip might have some QFP100 parts in one of their older lines that I'm not so familiar with. I believe their logic cells can be either logic, or FFs, but not both. So you need roughly double the count, if not more. They are very expensive too. I've never been inclined to research such an old product, much like the Spartan 3. I get that in a QFP100, but how long will they continue to make Spartan 3 devices... which have also climbed significantly in price. It's what is called NRND. Gowin would have been perfect, but at one point they were put on a US list of CCMC (Communist Chinese Military Companies). Even though they were taken off, my customer sells a lot to the US government, so they don't like the "optics".
>
> Did I miss any?

Okay, QFP144 is too large, that severily limits the QFP options, but
Lattice does have a QFP100: ICE40HX1K-VQ100. But this one may not have
enough logic for you, its the smallest in the series.

--
Stef

Rube Walker: "Hey, Yogi, what time is it?"
Yogi Berra: "You mean now?"

Re: PCB Layout for BGAs

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
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 by: gnuarm.del...@gmail. - Tue, 10 Jan 2023 14:19 UTC

On Tuesday, January 10, 2023 at 3:52:54 AM UTC-5, Stef wrote:
> On 2023-01-10 gnuarm.del...@gmail.com wrote in comp.arch.fpga:
> > On Monday, January 9, 2023 at 7:30:34 PM UTC-5, Stef wrote:
> >> On 2023-01-09 gnuarm.del...@gmail.com wrote in comp.arch.fpga:
> >> >
> >> > I'm trying to be as conservative as possible. I'd rather not use BGAs at all, but the only QFPs I can find that fit on the board are Gowin, which is not on the approved vendor list with my customer. They are too Chinese.
> >> >
> >> Digikey has a number of FPGAs in QFP100/144 in stock. Efinix,
> >> Microchip, Lattice, Xilinx. Nothing that suits your needs?
> >
> > The QFP144 is far too large. Efinix has no QFP100 parts. Lattice has no QFP100 parts that I've seen since the LFXP parts revision 2.0 of my board used. Xilinx has not had any in decades, unless you mean the very small, yet expensive CPLD thing they sell. Microchip might have some QFP100 parts in one of their older lines that I'm not so familiar with. I believe their logic cells can be either logic, or FFs, but not both. So you need roughly double the count, if not more. They are very expensive too. I've never been inclined to research such an old product, much like the Spartan 3. I get that in a QFP100, but how long will they continue to make Spartan 3 devices... which have also climbed significantly in price. It's what is called NRND. Gowin would have been perfect, but at one point they were put on a US list of CCMC (Communist Chinese Military Companies). Even though they were taken off, my customer sells a lot to the US government, so they don't like the "optics".
> >
> > Did I miss any?
> Okay, QFP144 is too large, that severily limits the QFP options, but
> Lattice does have a QFP100: ICE40HX1K-VQ100. But this one may not have
> enough logic for you, its the smallest in the series.

No, that is too small. They also have a QFN84, which unfortunately is two rows, requiring finer than 0.1 mm trace/space. Again, only supporting the 1K size, and oddly enough, no support for the PLL.

The current design is 3 kLUTs at 90% utilization. I was surprised it fit. I don't want to squeeze a new design so tightly, and I need to add some logic, so I'm shooting for at least a 5 kLUT part and prefer larger. The current design has uLaw and I'd like to be able to add Alaw, not that it's a lot of logic, but it's something more than a couple of LUTs. Then there's the multipliers... the current design uses one multiply, done using LUTs. I've been asked to provide gain controls, requiring two more multipliers, 16 x 8 minimum. This could be done by shift and add, so not horribly large. But built in multipliers would help with the size and the iCE40 line has none.

Oddly enough, many of the Lattice lines (even relatively modern ones) have no multipliers. The entire XO3 line has no multipliers. The MachXO3D has a couple of parts in an QFN72 with enough I/Os (barely), but not much availability. Hmmm... this may have improved. The MachXO3D-9400 has enough inventory in various configurations to do the initial order. But the I/O count on the QFN72 probably won't be enough with the added features. Ignoring that, the current inventory might get me through the current order, but 53 weeks for any further inventory. Digikey tells you more are coming in April. When you enter a number, it's always available in April, even a million..

--

Rick C.

++ Get 1,000 miles of free Supercharging
++ Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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From: jan4comp...@murray-microft.co.uk (jan Coombs)
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Subject: Re: PCB Layout for BGAs
Date: Tue, 10 Jan 2023 17:33:50 +0000
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 by: jan Coombs - Tue, 10 Jan 2023 17:33 UTC

On Tue, 10 Jan 2023 06:19:58 -0800 (PST)
"gnuarm.del...@gmail.com" <gnuarm.deletethisbit@gmail.com> wrote:

> But built in multipliers would help with the size and the iCE40 line has none.

Just four or eight multipliers, and many more on-chip goodies:
https://www.latticesemi.com/en/Products/FPGAandCPLD/iCE40UltraPlus

dev board
https://tinyvision.ai/collections/kits/products/upduino-v3-1

Jan Coombs
--

Re: PCB Layout for BGAs

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 by: Michael Schwingen - Tue, 10 Jan 2023 18:35 UTC

On 2023-01-09, gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:
>
> I'm concerned about adding cost for the boards, cost for the assembly and
> just an easy road forward. I spend the last two years building 8,000
> units when the CODEC factory burnt down. The customer knows about this
> issue, but the previous CM turned flaky on me and all but stopped
> delivering product.
>
> I have a new CM, but I don't want to go through production problems again.

0.8mm BGA should be no problem for any reputable CM - fine-pitch QFP is
usually more trouble.

> JLCPCB does 0.2 mm holes without extra charge, along with 0.45 mm via
> pads. They charge a bit extra for 0.4 mm pads. I guess it makes for a
> smaller target. I look at various PCB maker's pages to see what they
> state they can do.

That should be enough to fit a via between the 0.8mm-BGA pads - that's what
we do regulary. If you want blocking caps underneath the BGA, you will
probably require plugged/plated vias. You will have to look at the pinout
and do the fanout routing to see how many layers you need.

Talk to your PCB manufacturer about the details before doing the final
layout - there is some fine tuning (eg. drill size, annular ring, spacing)
where different PCB manufacturers have different preferences regarding which
rules will yield good results - when doing do, 0.8mm BGA should be possible
at modest PCB costs.

cu
Michael
--
Some people have no respect of age unless it is bottled.

Re: PCB Layout for BGAs

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 by: Michael Schwingen - Tue, 10 Jan 2023 18:38 UTC

On 2023-01-10, gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:
>
> The QFP144 is far too large. Efinix has no QFP100 parts. Lattice has no
> QFP100 parts that I've seen since the LFXP parts revision 2.0 of my board
> used.

We have used Lattice MachXO2 in TQFP100 in the past - not sure if these fit
your needs.

> At this point, I'd be happy with the Xilinx XC7S15-1FTGB196I.

Okay, this sounds like the MXO2 might be two sizes to small for you.

cu
Michael
--
Some people have no respect of age unless it is bottled.

Re: PCB Layout for BGAs

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 by: gnuarm.del...@gmail. - Tue, 10 Jan 2023 22:17 UTC

On Tuesday, January 10, 2023 at 12:33:54 PM UTC-5, jan Coombs wrote:
> On Tue, 10 Jan 2023 06:19:58 -0800 (PST)
> "gnuarm.del...@gmail.com" <gnuarm.del...@gmail.com> wrote:
>
> > But built in multipliers would help with the size and the iCE40 line has none.
> Just four or eight multipliers, and many more on-chip goodies:
>
> https://www.latticesemi.com/en/Products/FPGAandCPLD/iCE40UltraPlus
>
> dev board
> https://tinyvision.ai/collections/kits/products/upduino-v3-1

Yes, sorry, they do make a few multiplier chips with FPGA tiles. I was referring to parts that I might be able to use. They have a couple of 8 kLUT parts, only one in a package that I could use. I can pick between a 0.8 mm ball pitch, or 0.65 mm. Not really excited about either, even though there's a bit of inventory of the 256 ball, 0.8 mm part. But no insight into future deliveries.

This looking for usable parts gets old fast, and I've been doing it for over a year now. When I find the guy responsible for this shortage, I'm going to give him a piece of my mind!

--

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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 by: gnuarm.del...@gmail. - Tue, 10 Jan 2023 22:44 UTC

On Tuesday, January 10, 2023 at 1:35:24 PM UTC-5, Michael Schwingen wrote:
> On 2023-01-09, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com> wrote:
> >
> > I'm concerned about adding cost for the boards, cost for the assembly and
> > just an easy road forward. I spend the last two years building 8,000
> > units when the CODEC factory burnt down. The customer knows about this
> > issue, but the previous CM turned flaky on me and all but stopped
> > delivering product.
> >
> > I have a new CM, but I don't want to go through production problems again.
> 0.8mm BGA should be no problem for any reputable CM - fine-pitch QFP is
> usually more trouble.

Part of my problem is a lack of having designed with BGAs before. I can find footprint recommendations, but they are different for every manufacturer.. It didn't occur to me that this might be because even though they have the same pitch and ball count, they may not have the same ball size.

The two primary choices right now are a 196 ball, 1.0 mm pitch and 256 ball, 0.8 mm pitch. Can you share the design rules you used for these parts?

> > JLCPCB does 0.2 mm holes without extra charge, along with 0.45 mm via
> > pads. They charge a bit extra for 0.4 mm pads. I guess it makes for a
> > smaller target. I look at various PCB maker's pages to see what they
> > state they can do.
> That should be enough to fit a via between the 0.8mm-BGA pads - that's what
> we do regulary. If you want blocking caps underneath the BGA, you will
> probably require plugged/plated vias. You will have to look at the pinout
> and do the fanout routing to see how many layers you need.
>
> Talk to your PCB manufacturer about the details before doing the final
> layout - there is some fine tuning (eg. drill size, annular ring, spacing)
> where different PCB manufacturers have different preferences regarding which
> rules will yield good results - when doing do, 0.8mm BGA should be possible
> at modest PCB costs.

You mean my CM who orders the PWBs? Yeah, I've tried asking before and they say they would need a design so they could get a quote. I know, that sounds lame, but I used four different CMs over the last decade and they have all said the same thing. They don't have design rules, that's for me to know.

--

Rick C.

--+ Get 1,000 miles of free Supercharging
--+ Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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 by: gnuarm.del...@gmail. - Tue, 10 Jan 2023 23:48 UTC

On Tuesday, January 10, 2023 at 1:39:43 PM UTC-5, Michael Schwingen wrote:
> On 2023-01-10, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com> wrote:
> >
> > The QFP144 is far too large. Efinix has no QFP100 parts. Lattice has no
> > QFP100 parts that I've seen since the LFXP parts revision 2.0 of my board
> > used.
> We have used Lattice MachXO2 in TQFP100 in the past - not sure if these fit
> your needs.
> > At this point, I'd be happy with the Xilinx XC7S15-1FTGB196I.
> Okay, this sounds like the MXO2 might be two sizes to small for you.

I have the Lattice selection guide, the Lattice package guide, Lattice data sheets and have marked all the packages I might use on all the parts I might use.

No, the MXO2 parts are pretty limited for this. The existing design is shoehorned into the 3 kLUT XP part. I was surprised it routed. I have to add some logic and I don't have the same confidence in routing, so I want plenty of room in this part. 5 kLUTs should do the job, but I'd like to have a bit more. The Xilinx part has 6000 LCs, but there is no such thing as a LC in a Xilinx part, that's a marketing term. The XC7S6 has 3,752 6LUTs and twice that many FFs, so it should be about like an 8 kLUT device, but who knows if the routing is up to it. The only one in stock is the XC7S15, so that's the one I would use, at least to start. But I need a better price than the $25, and some expectation of getting more parts.

Anyone see signs of the shortages easing?

--

Rick C.

-+- Get 1,000 miles of free Supercharging
-+- Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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From: david.br...@hesbynett.no (David Brown)
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Subject: Re: PCB Layout for BGAs
Date: Wed, 11 Jan 2023 11:26:42 +0100
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 by: David Brown - Wed, 11 Jan 2023 10:26 UTC

On 10/01/2023 23:17, gnuarm.del...@gmail.com wrote:
>
> Yes, sorry, they do make a few multiplier chips with FPGA tiles. I
> was referring to parts that I might be able to use. They have a
> couple of 8 kLUT parts, only one in a package that I could use. I
> can pick between a 0.8 mm ball pitch, or 0.65 mm. Not really excited
> about either, even though there's a bit of inventory of the 256 ball,
> 0.8 mm part. But no insight into future deliveries.
>
> This looking for usable parts gets old fast, and I've been doing it
> for over a year now. When I find the guy responsible for this
> shortage, I'm going to give him a piece of my mind!
>

The reason you can parts in high-density packages, but not low-density
packages, is that there are lots of people such as yourself who are so
reluctant to use the small pitch devices. (This is not criticism - you
have solid reasons for preferring larger pitch devices, as do many
others.) Big manufacturers often prefer smaller pitch and higher
density, as it can lead to lower overall costs for their products, even
if design is more costly and the pcbs are more expensive.

There have been component supply issues for several years now, with only
gradual improvement in many areas. But there is a general pattern of
somewhat higher availability in smaller pitch parts.

Re: PCB Layout for BGAs

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 by: David Brown - Wed, 11 Jan 2023 10:42 UTC

On 10/01/2023 23:44, gnuarm.del...@gmail.com wrote:
> On Tuesday, January 10, 2023 at 1:35:24 PM UTC-5, Michael Schwingen
> wrote:
>> On 2023-01-09, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com>
>> wrote:
>>>
>>> I'm concerned about adding cost for the boards, cost for the
>>> assembly and just an easy road forward. I spend the last two
>>> years building 8,000 units when the CODEC factory burnt down. The
>>> customer knows about this issue, but the previous CM turned flaky
>>> on me and all but stopped delivering product.
>>>
>>> I have a new CM, but I don't want to go through production
>>> problems again.
>> 0.8mm BGA should be no problem for any reputable CM - fine-pitch
>> QFP is usually more trouble.
>
> Part of my problem is a lack of having designed with BGAs before. I
> can find footprint recommendations, but they are different for every
> manufacturer. It didn't occur to me that this might be because even
> though they have the same pitch and ball count, they may not have the
> same ball size.
>
> The two primary choices right now are a 196 ball, 1.0 mm pitch and
> 256 ball, 0.8 mm pitch. Can you share the design rules you used for
> these parts?
>

The board stackup, routing and bypassing recommendations from FPGA
manufacturers are basically bollocks. I believe it is primarily a
matter of being able to fob off complaints and support requests by
saying "Did you follow our layout application notes, impossible though
they may be? If not, it's not /our/ fault that you have problems."

OK, that's a bit of an exaggeration, but you can ignore the suggestions
of 16 layers with 8 different power planes and a dozen different
capacitor sizes mounted directly below the device.

Yes, there are complications for BGA layouts. And I'm afraid you are
going to have to do some research, some learning, and some discussions
with both PCB manufacturers (or their proxies) and board builders.

For the same pitch of BGA, there can be different sized balls, and
different sized pads on the underside of the BGA device which will
affect the shape of the ball after soldering. Pad size on the pcb has
different options. You have a key decision between solder mask defined
and non-solder mask defined pads, which affects mechanical strength,
thermal stability, solder paste masks, routeability, and manufacturing
requirements. And BGA soldering has different requirements in
production than non-BGA devices.

I have no doubt that this is something you can master quite quickly -
it's not /that/ hard. But it's not something you can learn just by a
thread on a newsgroup.

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
Injection-Date: Wed, 11 Jan 2023 12:42:42 +0000
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 by: gnuarm.del...@gmail. - Wed, 11 Jan 2023 12:42 UTC

On Wednesday, January 11, 2023 at 5:26:48 AM UTC-5, David Brown wrote:
> On 10/01/2023 23:17, gnuarm.del...@gmail.com wrote:
> >
> > Yes, sorry, they do make a few multiplier chips with FPGA tiles. I
> > was referring to parts that I might be able to use. They have a
> > couple of 8 kLUT parts, only one in a package that I could use. I
> > can pick between a 0.8 mm ball pitch, or 0.65 mm. Not really excited
> > about either, even though there's a bit of inventory of the 256 ball,
> > 0.8 mm part. But no insight into future deliveries.
> >
> > This looking for usable parts gets old fast, and I've been doing it
> > for over a year now. When I find the guy responsible for this
> > shortage, I'm going to give him a piece of my mind!
> >
> The reason you can parts in high-density packages, but not low-density
> packages, is that there are lots of people such as yourself who are so
> reluctant to use the small pitch devices. (This is not criticism - you
> have solid reasons for preferring larger pitch devices, as do many
> others.) Big manufacturers often prefer smaller pitch and higher
> density, as it can lead to lower overall costs for their products, even
> if design is more costly and the pcbs are more expensive.
>
> There have been component supply issues for several years now, with only
> gradual improvement in many areas. But there is a general pattern of
> somewhat higher availability in smaller pitch parts.

The very fine pitch parts are used to save space on the board. Some applications, like cell phones, simply require it. Not sure it saves any money, really. If you save on board size, you pay that back for finer pitch and laser drilled holes.

--

Rick C.

-++ Get 1,000 miles of free Supercharging
-++ Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
Injection-Date: Wed, 11 Jan 2023 12:49:35 +0000
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 by: gnuarm.del...@gmail. - Wed, 11 Jan 2023 12:49 UTC

On Wednesday, January 11, 2023 at 5:42:23 AM UTC-5, David Brown wrote:
> On 10/01/2023 23:44, gnuarm.del...@gmail.com wrote:
> > On Tuesday, January 10, 2023 at 1:35:24 PM UTC-5, Michael Schwingen
> > wrote:
> >> On 2023-01-09, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com>
> >> wrote:
> >>>
> >>> I'm concerned about adding cost for the boards, cost for the
> >>> assembly and just an easy road forward. I spend the last two
> >>> years building 8,000 units when the CODEC factory burnt down. The
> >>> customer knows about this issue, but the previous CM turned flaky
> >>> on me and all but stopped delivering product.
> >>>
> >>> I have a new CM, but I don't want to go through production
> >>> problems again.
> >> 0.8mm BGA should be no problem for any reputable CM - fine-pitch
> >> QFP is usually more trouble.
> >
> > Part of my problem is a lack of having designed with BGAs before. I
> > can find footprint recommendations, but they are different for every
> > manufacturer. It didn't occur to me that this might be because even
> > though they have the same pitch and ball count, they may not have the
> > same ball size.
> >
> > The two primary choices right now are a 196 ball, 1.0 mm pitch and
> > 256 ball, 0.8 mm pitch. Can you share the design rules you used for
> > these parts?
> >
> The board stackup, routing and bypassing recommendations from FPGA
> manufacturers are basically bollocks. I believe it is primarily a
> matter of being able to fob off complaints and support requests by
> saying "Did you follow our layout application notes, impossible though
> they may be? If not, it's not /our/ fault that you have problems."
>
> OK, that's a bit of an exaggeration, but you can ignore the suggestions
> of 16 layers with 8 different power planes and a dozen different
> capacitor sizes mounted directly below the device.

I see the opposite. When FPGA makers offer routing suggestions, they often provide one for routing of 100% of I/O pins, and another, using fewer layers, routing a portion of the I/O pins. So clearly they are trying to optimize cost of the boards for the user. No sign of CYA.

> Yes, there are complications for BGA layouts. And I'm afraid you are
> going to have to do some research, some learning, and some discussions
> with both PCB manufacturers (or their proxies) and board builders.
>
> For the same pitch of BGA, there can be different sized balls, and
> different sized pads on the underside of the BGA device which will
> affect the shape of the ball after soldering.

I haven't done a survey to check this yet. Do you know this for a fact?

> Pad size on the pcb has
> different options. You have a key decision between solder mask defined
> and non-solder mask defined pads, which affects mechanical strength,
> thermal stability, solder paste masks, routeability, and manufacturing
> requirements. And BGA soldering has different requirements in
> production than non-BGA devices.
>
>
> I have no doubt that this is something you can master quite quickly -
> it's not /that/ hard. But it's not something you can learn just by a
> thread on a newsgroup.

It's not "hard", it's "hard" to find the information for layout recommendations from each FPGA vendor. I'm going to need to put together a compendium of layout information, before I can compare vendors. The vendors may make it easy for me, based on availability and pricing. Xilinx is not in the running unless I can get someone there to give assurance of better supply in six months. Right now I'll have to buy every part in inventory of several combinations of speed and temperature, to build the order I have coming.

--

Rick C.

+-- Get 1,000 miles of free Supercharging
+-- Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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From: news-151...@discworld.dascon.de (Michael Schwingen)
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Subject: Re: PCB Layout for BGAs
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 by: Michael Schwingen - Wed, 11 Jan 2023 17:05 UTC

On 2023-01-10, gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:
>
> Part of my problem is a lack of having designed with BGAs before. I can
> find footprint recommendations, but they are different for every
> manufacturer. It didn't occur to me that this might be because even
> though they have the same pitch and ball count, they may not have the same
> ball size.

> The two primary choices right now are a 196 ball, 1.0 mm pitch and 256
> ball, 0.8 mm pitch. Can you share the design rules you used for these
> parts?

I have a 529 pin BGA with 0.8mm pitch. SMD pads for the BGA are 0.4mm, vias
are also 0.4mm with 0.2mm drill. Using these rules, a via fits nicely
between 4 BGA pads.

I have plugged/plated vias in order to put 0402/0201 capacitors underneath
the BGA, but if you can place the capacitors outside the BGA area, normal
vias should do.

>> Talk to your PCB manufacturer about the details before doing the final
>> layout - there is some fine tuning (eg. drill size, annular ring, spacing)
>> where different PCB manufacturers have different preferences regarding which
>> rules will yield good results - when doing do, 0.8mm BGA should be possible
>> at modest PCB costs.
>
> You mean my CM who orders the PWBs? Yeah, I've tried asking before and
> they say they would need a design so they could get a quote. I know, that
> sounds lame, but I used four different CMs over the last decade and they
> have all said the same thing. They don't have design rules, that's for me
> to know.

OK, if you do not order the PCBs yourself, you have to forward this through
your CM. You will probably have to prepare a sample design (just the BGA
area with fanout), produce gerbers, and have them ask for feedback. Same
about the layer stackup if you need controlled impedances.

cu
Michael
--
Some people have no respect of age unless it is bottled.

Re: PCB Layout for BGAs

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Subject: Re: PCB Layout for BGAs
From: gnuarm.d...@gmail.com (gnuarm.del...@gmail.com)
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 by: gnuarm.del...@gmail. - Thu, 12 Jan 2023 03:29 UTC

On Wednesday, January 11, 2023 at 1:06:01 PM UTC-4, Michael Schwingen wrote:
> On 2023-01-10, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com> wrote:
> >
> > Part of my problem is a lack of having designed with BGAs before. I can
> > find footprint recommendations, but they are different for every
> > manufacturer. It didn't occur to me that this might be because even
> > though they have the same pitch and ball count, they may not have the same
> > ball size.
>
> > The two primary choices right now are a 196 ball, 1.0 mm pitch and 256
> > ball, 0.8 mm pitch. Can you share the design rules you used for these
> > parts?
> I have a 529 pin BGA with 0.8mm pitch. SMD pads for the BGA are 0.4mm, vias
> are also 0.4mm with 0.2mm drill. Using these rules, a via fits nicely
> between 4 BGA pads.

You would need to use 5 mil trace and space to get between the pads. That doesn't sound too bad. Via to pad is 6.5 mil, again good.

Where did you get your pad size numbers? Your via pad only gives you 4 mil annular ring. That sounds a bit tight. To make that a 5 mil annular ring would shorten the 6.5 mil via to pad space to 5.5 mil, still good. Why did you choose a 0.4 mm pad?

> I have plugged/plated vias in order to put 0402/0201 capacitors underneath
> the BGA, but if you can place the capacitors outside the BGA area, normal
> vias should do.
> >> Talk to your PCB manufacturer about the details before doing the final
> >> layout - there is some fine tuning (eg. drill size, annular ring, spacing)
> >> where different PCB manufacturers have different preferences regarding which
> >> rules will yield good results - when doing do, 0.8mm BGA should be possible
> >> at modest PCB costs.
> >
> > You mean my CM who orders the PWBs? Yeah, I've tried asking before and
> > they say they would need a design so they could get a quote. I know, that
> > sounds lame, but I used four different CMs over the last decade and they
> > have all said the same thing. They don't have design rules, that's for me
> > to know.
> OK, if you do not order the PCBs yourself, you have to forward this through
> your CM. You will probably have to prepare a sample design (just the BGA
> area with fanout), produce gerbers, and have them ask for feedback. Same
> about the layer stackup if you need controlled impedances.

I asked my CM the general question of their BGA assembly experience and an estimated cost increment for going from a 100QFP to the 196 ball, 1.0 mm pitch BGA and 256 ball, 0.8 mm BGA. We'll see what they come up with. If they can give me a dollar figure, they should be able to give me dimensions they are comfortable working with.

Thanks for discussing this with me.

--

Rick C.

+-+ Get 1,000 miles of free Supercharging
+-+ Tesla referral code - https://ts.la/richard11209

Re: PCB Layout for BGAs

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From: david.br...@hesbynett.no (David Brown)
Newsgroups: comp.arch.fpga
Subject: Re: PCB Layout for BGAs
Date: Thu, 12 Jan 2023 08:45:08 +0100
Organization: A noiseless patient Spider
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 by: David Brown - Thu, 12 Jan 2023 07:45 UTC

On 11/01/2023 13:42, gnuarm.del...@gmail.com wrote:
> On Wednesday, January 11, 2023 at 5:26:48 AM UTC-5, David Brown
> wrote:

>> The reason you can parts in high-density packages, but not
>> low-density packages, is that there are lots of people such as
>> yourself who are so reluctant to use the small pitch devices. (This
>> is not criticism - you have solid reasons for preferring larger
>> pitch devices, as do many others.) Big manufacturers often prefer
>> smaller pitch and higher density, as it can lead to lower overall
>> costs for their products, even if design is more costly and the
>> pcbs are more expensive.
>>
>> There have been component supply issues for several years now, with
>> only gradual improvement in many areas. But there is a general
>> pattern of somewhat higher availability in smaller pitch parts.
>
> The very fine pitch parts are used to save space on the board. Some
> applications, like cell phones, simply require it. Not sure it saves
> any money, really. If you save on board size, you pay that back for
> finer pitch and laser drilled holes.
>

A great many boards are built into products. It's not just on cell
phones or other consumer gadgets that saving space is important. If the
device you are making can be smaller, then it uses less material
(plastic, aluminium, whatever), weighs less, can go in a smaller box,
costs less to deliver, smaller storage space, etc. For most people who
only see one part of a system, it can be surprising how these things add
up in the complete price of many products. Shave off a percent or two
of the price at each step, and it all adds up (actually, it all
/multiplies/ up!) to lower cost overall even if the board is more
expensive. Of course you have to be dealing with large quantities
(bigger numbers than anything we make) for these things to be important
- but it's the big buyers that buy most of the parts!

Even if we just stick to the pcb itself, pcbs cost per square
centimetre. Using smaller packages can mean higher cost per unit area,
but can also mean lower total area if the package size is the driving
factor (rather than mechanics, connectors, etc.). Reduced total area
can lead to more boards per panel for part placement and soldering, and
lower manufacturing costs.


devel / comp.arch.fpga / PCB Layout for BGAs

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