We designed a test board to measure surface leakage vs various
no-clean fluxes, both reflow and selective solder.

https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0

I'm just doing some baseline tests on two as-received boards. The
Keithley electrometer has settling time constants in the 10s of
minutes on the higher ranges, above 1e12 ohms. If I walk around the
room, even 10 feet away, the meter swings all over the scale. The
"fast" mode doesn't work in my meter.

If I hold a grounded wire (actually a long USBc cable plugged in to my
PC) it's a lot better.

My production people will solder a bunch of boards and we'll test
them. I've decided that a good humidity-soak test chamber is a toilet
tank.

John Larkin wrote:
> We designed a test board to measure surface leakage vs various
> no-clean fluxes, both reflow and selective solder.
>
> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>
> I'm just doing some baseline tests on two as-received boards. The
> Keithley electrometer has settling time constants in the 10s of
> minutes on the higher ranges, above 1e12 ohms. If I walk around the
> room, even 10 feet away, the meter swings all over the scale. The
> "fast" mode doesn't work in my meter.
>
> If I hold a grounded wire (actually a long USBc cable plugged in to my
> PC) it's a lot better.
>
> My production people will solder a bunch of boards and we'll test
> them. I've decided that a good humidity-soak test chamber is a toilet
> tank.
>

Boiling them in the pasta pot will work too. ;) It'll make the pasta
taste a bit like balsamic vinegar too!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 16/07/2021 18:33, Phil Hobbs wrote:
> John Larkin wrote:
>> We designed a test board to measure surface leakage vs various
>> no-clean fluxes, both reflow and selective solder.
>>
>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>
>> I'm just doing some baseline tests on two as-received boards. The
>> Keithley electrometer has settling time constants in the 10s of
>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>> room, even 10 feet away, the meter swings all over the scale. The
>> "fast" mode doesn't work in my meter.
>>
>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>> PC) it's a lot better.
>>
>> My production people will solder a bunch of boards and we'll test
>> them. I've decided that a good humidity-soak test chamber is a toilet
>> tank.
>>
>
> Boiling them in the pasta pot will work too. ;)  It'll make the pasta
> taste a bit like balsamic vinegar too!
>
> Cheers
>
> Phil Hobbs
>
Pease said to use a domestic dishwasher! I tried that and it seemed to
work visually well but I didn't measure leakage resistivity.

piglet

Piglet wrote:
> On 16/07/2021 18:33, Phil Hobbs wrote:
>> John Larkin wrote:
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The
>>> "fast" mode doesn't work in my meter.
>>>
>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>> PC) it's a lot better.
>>>
>>> My production people will solder a bunch of boards and we'll test
>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>> tank.
>>>
>>
>> Boiling them in the pasta pot will work too. ;)  It'll make the pasta
>> taste a bit like balsamic vinegar too!
>>
>> Cheers
>>
>> Phil Hobbs
>>
> Pease said to use a domestic dishwasher! I tried that and it seemed to
> work visually well but I didn't measure leakage resistivity.
>
> piglet
>
He was writing back in the phosphate days, though--I doubt the newer
detergents will work well. Alconox maybe?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Fri, 16 Jul 2021 20:28:49 +0100, Piglet <erichpwagner@hotmail.com>
wrote:

>On 16/07/2021 18:33, Phil Hobbs wrote:
>> John Larkin wrote:
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The
>>> "fast" mode doesn't work in my meter.
>>>
>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>> PC) it's a lot better.
>>>
>>> My production people will solder a bunch of boards and we'll test
>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>> tank.
>>>
>>
>> Boiling them in the pasta pot will work too. ;)  It'll make the pasta
>> taste a bit like balsamic vinegar too!
>>
>> Cheers
>>
>> Phil Hobbs
>>
>Pease said to use a domestic dishwasher! I tried that and it seemed to
>work visually well but I didn't measure leakage resistivity.
>
>piglet

That was for cleaning. I want to take a bunch of soldered boards (with
various no-clean fluxes) and expose them to 100% humidity for a couple
of days, and re-measure leakage.

On a D25 connector layout, leakage between rows of alternate pins is
very roughly 3e13 ohms. If I rub it with greasy and salty fingerprints
(many Fritos died for science) and stash at 100% humidity overnight,
it drops to about 1e12. Cleaning with qtips and acetone gets it back
to 3e13 range.

On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>We designed a test board to measure surface leakage vs various
>no-clean fluxes, both reflow and selective solder.
>
>https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>
>I'm just doing some baseline tests on two as-received boards. The
>Keithley electrometer has settling time constants in the 10s of
>minutes on the higher ranges, above 1e12 ohms. If I walk around the
>room, even 10 feet away, the meter swings all over the scale. The
>"fast" mode doesn't work in my meter.
>
>If I hold a grounded wire (actually a long USBc cable plugged in to my
>PC) it's a lot better.
>
>My production people will solder a bunch of boards and we'll test
>them. I've decided that a good humidity-soak test chamber is a toilet
>tank.

Add saltpeter to a cup of water till it won't absorb any more. Stick
in airtight container with your sample.

RL

In article <c243ac9e-b54d-dd4b-721d-530b448a0b7c@electrooptical.net>,
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

>> Pease said to use a domestic dishwasher! I tried that and it seemed to
>> work visually well but I didn't measure leakage resistivity.
>>
>> piglet
>>
>He was writing back in the phosphate days, though--I doubt the newer
>detergents will work well. Alconox maybe?

He specifically mentioned Calgonite. One MSDS I see for it lists
surfactants, sodium carbonate, and sodium silicate - no phosphates
(although I imagine there could have been some, pre-2010... seems
likely in fact).

Since Alconox still contains tetrasodium diphosphate it might well
work better than today's commercial automatic dishwasher detergents.

On Fri, 16 Jul 2021 14:25:26 -0700, dplatt@coop.radagast.org (Dave
Platt) wrote:

>In article <c243ac9e-b54d-dd4b-721d-530b448a0b7c@electrooptical.net>,
>Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>>> Pease said to use a domestic dishwasher! I tried that and it seemed to
>>> work visually well but I didn't measure leakage resistivity.
>>>
>>> piglet
>>>
>>He was writing back in the phosphate days, though--I doubt the newer
>>detergents will work well. Alconox maybe?
>
>He specifically mentioned Calgonite. One MSDS I see for it lists
>surfactants, sodium carbonate, and sodium silicate - no phosphates
>(although I imagine there could have been some, pre-2010... seems
>likely in fact).
>
>Since Alconox still contains tetrasodium diphosphate it might well
>work better than today's commercial automatic dishwasher detergents.

Bubble Bandit: "All the phosphates."

On Fri, 16 Jul 2021 18:04:10 -0400, legg <legg@nospam.magma.ca> wrote:

>On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
><jlarkin@highland_atwork_technology.com> wrote:
>
>>We designed a test board to measure surface leakage vs various
>>no-clean fluxes, both reflow and selective solder.
>>
>>https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>
>>I'm just doing some baseline tests on two as-received boards. The
>>Keithley electrometer has settling time constants in the 10s of
>>minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>room, even 10 feet away, the meter swings all over the scale. The
>>"fast" mode doesn't work in my meter.
>>
>>If I hold a grounded wire (actually a long USBc cable plugged in to my
>>PC) it's a lot better.
>>
>>My production people will solder a bunch of boards and we'll test
>>them. I've decided that a good humidity-soak test chamber is a toilet
>>tank.
>
>
>Add saltpeter to a cup of water till it won't absorb any more. Stick
>in airtight container with your sample.
>
>RL

Seems like a puddle of water in the bottom of a bucket will get to
100% humidity. What does potassium nitrate do?

John Larkin <jlarkin@highland_atwork_technology.com> wrote:

> We designed a test board to measure surface leakage vs various
> no-clean fluxes, both reflow and selective solder.
>
> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>
> I'm just doing some baseline tests on two as-received boards. The
> Keithley electrometer has settling time constants in the 10s of
> minutes on the higher ranges, above 1e12 ohms. If I walk around the
> room, even 10 feet away, the meter swings all over the scale. The
> "fast" mode doesn't work in my meter.

You have too much capacitance in the connecting cable. Use the J105 Unity
Gain output on the back panel as a guard. It follows the input signal to
within 10ppm, cancelling the cable capacitance.

Connect the cable shield to the J105 output and the test circuit ground,
and the center conductor to the test point.

Current time:

I = C * dv/dt
dt = (C * dv)/I
set I = 1e-14 Amp, C = 10 pf, dv = 1 V
dt = (10e-12 * 1) / 1e-14 = 1,000 seconds = 16.66 minutes

with dv = 0, dt = 0

See X1 Output (J105) on page 10:

https://labmecanica.files.wordpress.com/2016/02/manual-
electrometromodel610c610cr.pdf

[...]

--
The best designs occur in the theta state. - sw

On Fri, 16 Jul 2021 22:21:48 -0000 (UTC), Steve Wilson
<spamme@not.com> wrote:

>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>
>> We designed a test board to measure surface leakage vs various
>> no-clean fluxes, both reflow and selective solder.
>>
>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>
>> I'm just doing some baseline tests on two as-received boards. The
>> Keithley electrometer has settling time constants in the 10s of
>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>> room, even 10 feet away, the meter swings all over the scale. The
>> "fast" mode doesn't work in my meter.
>
>You have too much capacitance in the connecting cable.

It's about an inch long, a 1/4 w resistor in free air actually. The
capacitance is mostly the pads on the PCB, and likely stuff inside the
meter. There's about 6 pF between the test points on the D25 pattern.

Our main use for leaded 1/4 w resistors is as a source for short bits
of wire.

> Use the J105 Unity
>Gain output on the back panel as a guard. It follows the input signal to
>within 10ppm, cancelling the cable capacitance.
>
>Connect the cable shield to the J105 output and the test circuit ground,
>and the center conductor to the test point.

Possibly I could bootstrap the PCB ground plane. But just the meter
(Keithley 610C) with nothing connected looks like it will take a good
chunk of an hour to pin the needle at 1e14 ohms full scale.

Cool instrument, though.

On 17/7/21 8:14 am, John Larkin wrote:
> On Fri, 16 Jul 2021 18:04:10 -0400, legg <legg@nospam.magma.ca> wrote:
>
>> On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
>> <jlarkin@highland_atwork_technology.com> wrote:
>>
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The
>>> "fast" mode doesn't work in my meter.
>>>
>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>> PC) it's a lot better.
>>>
>>> My production people will solder a bunch of boards and we'll test
>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>> tank.
>>
>>
>> Add saltpeter to a cup of water till it won't absorb any more. Stick
>> in airtight container with your sample.
>>
>> RL
>
> Seems like a puddle of water in the bottom of a bucket will get to
> 100% humidity. What does potassium nitrate do?

A lot of seals that will last forever in clean water start to leak as
soon as there is an osmotic gradient involved.

CH

On Fri, 16 Jul 2021 15:33:18 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Piglet wrote:
>> On 16/07/2021 18:33, Phil Hobbs wrote:
>>> John Larkin wrote:
>>>> We designed a test board to measure surface leakage vs various
>>>> no-clean fluxes, both reflow and selective solder.
>>>>
>>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>>
>>>>
>>>> I'm just doing some baseline tests on two as-received boards. The
>>>> Keithley electrometer has settling time constants in the 10s of
>>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>>> room, even 10 feet away, the meter swings all over the scale. The
>>>> "fast" mode doesn't work in my meter.
>>>>
>>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>>> PC) it's a lot better.
>>>>
>>>> My production people will solder a bunch of boards and we'll test
>>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>>> tank.
>>>>
>>>
>>> Boiling them in the pasta pot will work too. ;)  It'll make the pasta
>>> taste a bit like balsamic vinegar too!
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>>
>> Pease said to use a domestic dishwasher! I tried that and it seemed to
>> work visually well but I didn't measure leakage resistivity.
>>
>> piglet
>>
>He was writing back in the phosphate days, though--I doubt the newer
>detergents will work well. Alconox maybe?

Yes.

Alconox if by hand, but AlcoJet if a dishwasher is used. Alconox
foams too much.

One can also still get phosphate detergents - they are now sold for
boiling deep fat fryers out.

..<https://pgpro.com/en-us/brands/cascade-professional/fryer-boil-out>

Available on Amazon.

Joe Gwinn

John Larkin wrote:
> On Fri, 16 Jul 2021 22:21:48 -0000 (UTC), Steve Wilson
> <spamme@not.com> wrote:
>
>> John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The
>>> "fast" mode doesn't work in my meter.
>>
>> You have too much capacitance in the connecting cable.
>
> It's about an inch long, a 1/4 w resistor in free air actually. The
> capacitance is mostly the pads on the PCB, and likely stuff inside the
> meter. There's about 6 pF between the test points on the D25 pattern.
>
> Our main use for leaded 1/4 w resistors is as a source for short bits
> of wire.
>
>
>> Use the J105 Unity
>> Gain output on the back panel as a guard. It follows the input signal to
>> within 10ppm, cancelling the cable capacitance.
>>
>> Connect the cable shield to the J105 output and the test circuit ground,
>> and the center conductor to the test point.
>
> Possibly I could bootstrap the PCB ground plane. But just the meter
> (Keithley 610C) with nothing connected looks like it will take a good
> chunk of an hour to pin the needle at 1e14 ohms full scale.
>
> Cool instrument, though.
>
Mine is much faster than that. You might hit eBay for another unit.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 7/16/21 6:14 PM, John Larkin wrote:
> On Fri, 16 Jul 2021 18:04:10 -0400, legg <legg@nospam.magma.ca> wrote:
>
>> On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
>> <jlarkin@highland_atwork_technology.com> wrote:
>>
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The
>>> "fast" mode doesn't work in my meter.
>>>
>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>> PC) it's a lot better.
>>>
>>> My production people will solder a bunch of boards and we'll test
>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>> tank.
>>
>>
>> Add saltpeter to a cup of water till it won't absorb any more. Stick
>> in airtight container with your sample.
>>
>> RL
>
> Seems like a puddle of water in the bottom of a bucket will get to
> 100% humidity. What does potassium nitrate do?
>

Dissolving stuff (usually some salt) in water changes the vapor pressure
and thus the relative humidity in the air above the water. Making the
solution saturated makes it easy to make, you just dump in enough so
some doesn't dissolve, and there are tables of salt solutions to
maintain most any desired relative humidity. These are useful to
directly maintain some relative humidity, and to check the calibration
of a humidity meter (sodium chloride results in 75% which is popular for
meter calibration). At 25C a saturated solution of potassium nitrate
will result in a relative humidity of about 94%. The problem with these
and with pure water is how long they take to reach equilibrium. I'm
assuming the benefit over pure water is that the humidity will be more
constant over small temperature changes which would make your
measurements more precise. One TLDR reference is:
https://nvlpubs.nist.gov/nistpubs/jres/81A/jresv81An1p89_A1b.pdf .

--
Regards,
Carl

John Larkin <jlarkin@highland_atwork_technology.com> wrote:

> On Fri, 16 Jul 2021 22:21:48 -0000 (UTC), Steve Wilson
> <spamme@not.com> wrote:
>
>>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The "fast"
>>> mode doesn't work in my meter.
>>
>>You have too much capacitance in the connecting cable.
>
> It's about an inch long, a 1/4 w resistor in free air actually. The
> capacitance is mostly the pads on the PCB, and likely stuff inside the
> meter. There's about 6 pF between the test points on the D25 pattern.

There's your problem. I estimated 10pf, but 6pf is reasonable. The stuff
inside the meter is cancelled with the J105 output. dv=0, so dt=0.

Just enclose the stray capacitance in the shielded guard, and your test time
will go down proportionally.

> Our main use for leaded 1/4 w resistors is as a source for short bits
> of wire.
>
>
>> Use the J105 Unity
>>Gain output on the back panel as a guard. It follows the input signal to
>>within 10ppm, cancelling the cable capacitance.
>>
>>Connect the cable shield to the J105 output and the test circuit ground,
>>and the center conductor to the test point.
>
> Possibly I could bootstrap the PCB ground plane. But just the meter
> (Keithley 610C) with nothing connected looks like it will take a good
> chunk of an hour to pin the needle at 1e14 ohms full scale.

RTFM. J105 is provided to set this time to zero.

> Cool instrument, though.
>

--
The best designs occur in the theta state. - sw

On Fri, 16 Jul 2021 21:42:53 -0400, Carl <carl.ijamesXX@YYverizon.net>
wrote:

>On 7/16/21 6:14 PM, John Larkin wrote:
>> On Fri, 16 Jul 2021 18:04:10 -0400, legg <legg@nospam.magma.ca> wrote:
>>
>>> On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
>>> <jlarkin@highland_atwork_technology.com> wrote:
>>>
>>>> We designed a test board to measure surface leakage vs various
>>>> no-clean fluxes, both reflow and selective solder.
>>>>
>>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>>
>>>> I'm just doing some baseline tests on two as-received boards. The
>>>> Keithley electrometer has settling time constants in the 10s of
>>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>>> room, even 10 feet away, the meter swings all over the scale. The
>>>> "fast" mode doesn't work in my meter.
>>>>
>>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>>> PC) it's a lot better.
>>>>
>>>> My production people will solder a bunch of boards and we'll test
>>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>>> tank.
>>>
>>>
>>> Add saltpeter to a cup of water till it won't absorb any more. Stick
>>> in airtight container with your sample.
>>>
>>> RL
>>
>> Seems like a puddle of water in the bottom of a bucket will get to
>> 100% humidity. What does potassium nitrate do?
>>
>
>Dissolving stuff (usually some salt) in water changes the vapor pressure
>and thus the relative humidity in the air above the water. Making the
>solution saturated makes it easy to make, you just dump in enough so
>some doesn't dissolve, and there are tables of salt solutions to
>maintain most any desired relative humidity. These are useful to
>directly maintain some relative humidity, and to check the calibration
>of a humidity meter (sodium chloride results in 75% which is popular for
>meter calibration). At 25C a saturated solution of potassium nitrate
>will result in a relative humidity of about 94%. The problem with these
>and with pure water is how long they take to reach equilibrium. I'm
>assuming the benefit over pure water is that the humidity will be more
>constant over small temperature changes which would make your
>measurements more precise. One TLDR reference is:
>https://nvlpubs.nist.gov/nistpubs/jres/81A/jresv81An1p89_A1b.pdf .

I looked it up. At high humidity, the salt mixture will suck water out
of the air, namely reduce humidity. I want maximum humidity, like
100%.

An inch of water in a bucket is sure easy.

--

John Larkin Highland Technology, Inc

The best designs are necessarily accidental.

On 7/16/21 10:26 PM, jlarkin@highlandsniptechnology.com wrote:
> On Fri, 16 Jul 2021 21:42:53 -0400, Carl <carl.ijamesXX@YYverizon.net>
> wrote:
>
>> On 7/16/21 6:14 PM, John Larkin wrote:
>>> On Fri, 16 Jul 2021 18:04:10 -0400, legg <legg@nospam.magma.ca> wrote:
>>>
>>>> On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
>>>> <jlarkin@highland_atwork_technology.com> wrote:
>>>>
>>>>> We designed a test board to measure surface leakage vs various
>>>>> no-clean fluxes, both reflow and selective solder.
>>>>>
>>>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>>>
>>>>> I'm just doing some baseline tests on two as-received boards. The
>>>>> Keithley electrometer has settling time constants in the 10s of
>>>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>>>> room, even 10 feet away, the meter swings all over the scale. The
>>>>> "fast" mode doesn't work in my meter.
>>>>>
>>>>> If I hold a grounded wire (actually a long USBc cable plugged in to my
>>>>> PC) it's a lot better.
>>>>>
>>>>> My production people will solder a bunch of boards and we'll test
>>>>> them. I've decided that a good humidity-soak test chamber is a toilet
>>>>> tank.
>>>>
>>>>
>>>> Add saltpeter to a cup of water till it won't absorb any more. Stick
>>>> in airtight container with your sample.
>>>>
>>>> RL
>>>
>>> Seems like a puddle of water in the bottom of a bucket will get to
>>> 100% humidity. What does potassium nitrate do?
>>>
>>
>> Dissolving stuff (usually some salt) in water changes the vapor pressure
>> and thus the relative humidity in the air above the water. Making the
>> solution saturated makes it easy to make, you just dump in enough so
>> some doesn't dissolve, and there are tables of salt solutions to
>> maintain most any desired relative humidity. These are useful to
>> directly maintain some relative humidity, and to check the calibration
>> of a humidity meter (sodium chloride results in 75% which is popular for
>> meter calibration). At 25C a saturated solution of potassium nitrate
>> will result in a relative humidity of about 94%. The problem with these
>> and with pure water is how long they take to reach equilibrium. I'm
>> assuming the benefit over pure water is that the humidity will be more
>> constant over small temperature changes which would make your
>> measurements more precise. One TLDR reference is:
>> https://nvlpubs.nist.gov/nistpubs/jres/81A/jresv81An1p89_A1b.pdf .
>
> I looked it up. At high humidity, the salt mixture will suck water out
> of the air, namely reduce humidity. I want maximum humidity, like
> 100%.
>
> An inch of water in a bucket is sure easy.
>
>
>

But it doesn't give you the thrill and risk of spattering salt water on
your board and ruining your test :-). I wasn't advocating for using a
saturated salt solution, just explaining what they do. Stand some large
sponges up in the bucket so the bottom part is submerged and the rest is
exposed to air to maximize your evaporation surface area. Starting with
hot water will speed things up, too.

--
Regards,
Carl

On Fri, 16 Jul 2021 15:14:11 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

>On Fri, 16 Jul 2021 18:04:10 -0400, legg <legg@nospam.magma.ca> wrote:
>
>>On Fri, 16 Jul 2021 10:11:24 -0700, John Larkin
>><jlarkin@highland_atwork_technology.com> wrote:
>>
>>>We designed a test board to measure surface leakage vs various
>>>no-clean fluxes, both reflow and selective solder.
>>>
>>>https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>>I'm just doing some baseline tests on two as-received boards. The
>>>Keithley electrometer has settling time constants in the 10s of
>>>minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>>room, even 10 feet away, the meter swings all over the scale. The
>>>"fast" mode doesn't work in my meter.
>>>
>>>If I hold a grounded wire (actually a long USBc cable plugged in to my
>>>PC) it's a lot better.
>>>
>>>My production people will solder a bunch of boards and we'll test
>>>them. I've decided that a good humidity-soak test chamber is a toilet
>>>tank.
>>
>>
>>Add saltpeter to a cup of water till it won't absorb any more. Stick
>>in airtight container with your sample.
>>
>>RL
>
>Seems like a puddle of water in the bottom of a bucket will get to
>100% humidity. What does potassium nitrate do?

As other posters have pointed out, it's relatively easy to
perform reproducable tests at a controlled RH.

If you use a shallow glass container, in the bottom of your
sealed environment. you'll get a good surface area and easy
visual confirmation of both liquids and solids in the saturated
solution, through whatever peep-hole is available.

You want a high humidity, non-condensing environment. Condensation
will spoil your test.

Having spent thousands of dollars on environmental chambers,
it is a pleasure to find one test that anyone can do, yes?

RL

John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> We designed a test board to measure surface leakage vs various
> no-clean fluxes, both reflow and selective solder.
>
> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>
> I'm just doing some baseline tests on two as-received boards. The
> Keithley electrometer has settling time constants in the 10s of
> minutes on the higher ranges, above 1e12 ohms. If I walk around the
> room, even 10 feet away, the meter swings all over the scale. The
> "fast" mode doesn't work in my meter.

Is there a tube in that thing? I use a Hiportronics teraohm meter, and
it's uh real sensitive to everything. I get the feeling even the binding
posts hurt the sensitivity some too. The whole ground vs guard planes
on the PCB and terminals are weird too.

On Tue, 20 Jul 2021 17:40:09 -0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> We designed a test board to measure surface leakage vs various
>> no-clean fluxes, both reflow and selective solder.
>>
>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>
>> I'm just doing some baseline tests on two as-received boards. The
>> Keithley electrometer has settling time constants in the 10s of
>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>> room, even 10 feet away, the meter swings all over the scale. The
>> "fast" mode doesn't work in my meter.
>
>Is there a tube in that thing?

No, the key part is an old small-signal mosfet.

>I use a Hiportronics teraohm meter, and
>it's uh real sensitive to everything. I get the feeling even the binding
>posts hurt the sensitivity some too. The whole ground vs guard planes
>on the PCB and terminals are weird too.

I built a home-made picoamp meter and the Radio Shack binding posts
leaked like anything. I had to mount them on a slab of polycarb.

https://www.dropbox.com/sh/o6pomayvpoi2r84/AACGPXNj4qf3eG33sbSOGPRra?dl=0

Cydrome Leader wrote:
> John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> We designed a test board to measure surface leakage vs various
>> no-clean fluxes, both reflow and selective solder.
>>
>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>
>> I'm just doing some baseline tests on two as-received boards. The
>> Keithley electrometer has settling time constants in the 10s of
>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>> room, even 10 feet away, the meter swings all over the scale. The
>> "fast" mode doesn't work in my meter.
>
> Is there a tube in that thing? I use a Hiportronics teraohm meter, and
> it's uh real sensitive to everything. I get the feeling even the binding
> posts hurt the sensitivity some too. The whole ground vs guard planes
> on the PCB and terminals are weird too.
>

Nah, a discrete FET diff pair. My Keithley 405 Micro-Micro-Ammeter uses
a tube and has a 10 fA full-scale range. It takes a good couple of
hours' warm-up time to get there.

$5 on eBay (plus probably $35 in shipping), back in the palmy days of
2009ish when you could get good boat anchors for 2 cents on the dollar,
as opposed to the current 5-cents-ish.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Wednesday, July 21, 2021 at 5:30:47 AM UTC+10, John Larkin wrote:
> On Tue, 20 Jul 2021 17:40:09 -0000 (UTC), Cydrome Leader <pres...@MUNGEpanix.com> wrote:
> >John Larkin <jlarkin@highland_atwork_technology.com> wrote:

<snip>

> I built a home-made picoamp meter and the Radio Shack binding posts
> leaked like anything. I had to mount them on a slab of polycarb.
>
> https://www.dropbox.com/sh/o6pomayvpoi2r84/AACGPXNj4qf3eG33sbSOGPRra?dl=0

Teflon (PTFE) works better. It's less mechanically stable and prone to cold-flow.

A Cambridge Instruments we bought pins that came with a PTFE standoff which we could plug int a circular hole in a printed circuit board.

Putting the dynode chain for a photo-multiplier tube onto a printed circuit board would have been impractical without them. We did have one small printed circuit board made with an alumina-loaded Teflon substrate, but that was for a half-nanosecond-wide -pulse generator.

--
Bill Sloman, Sydney

John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> On Tue, 20 Jul 2021 17:40:09 -0000 (UTC), Cydrome Leader
> <presence@MUNGEpanix.com> wrote:
>
>>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>> We designed a test board to measure surface leakage vs various
>>> no-clean fluxes, both reflow and selective solder.
>>>
>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>
>>> I'm just doing some baseline tests on two as-received boards. The
>>> Keithley electrometer has settling time constants in the 10s of
>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>> room, even 10 feet away, the meter swings all over the scale. The
>>> "fast" mode doesn't work in my meter.
>>
>>Is there a tube in that thing?
>
> No, the key part is an old small-signal mosfet.

Did they "nail it" with the first small signal FETs and mosfets? Are there
new ones that are any more sensitive or would subbing a modern version
cause problems in old test equipment that expects olden-day
characteristic?

>>I use a Hiportronics teraohm meter, and
>>it's uh real sensitive to everything. I get the feeling even the binding
>>posts hurt the sensitivity some too. The whole ground vs guard planes
>>on the PCB and terminals are weird too.
>
> I built a home-made picoamp meter and the Radio Shack binding posts
> leaked like anything. I had to mount them on a slab of polycarb.
>
> https://www.dropbox.com/sh/o6pomayvpoi2r84/AACGPXNj4qf3eG33sbSOGPRra?dl=0

Ha!

What's the white material the components trapeze off? I was expecting the
old nylon posts, not the "fancy" two-toned ones.

On Wed, 21 Jul 2021 04:18:37 -0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> On Tue, 20 Jul 2021 17:40:09 -0000 (UTC), Cydrome Leader
>> <presence@MUNGEpanix.com> wrote:
>>
>>>John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>>> We designed a test board to measure surface leakage vs various
>>>> no-clean fluxes, both reflow and selective solder.
>>>>
>>>> https://www.dropbox.com/sh/d6j3k0g3vykgfyq/AAAVDwv9MTo6l1Vo47NxLl7Ea?dl=0
>>>>
>>>> I'm just doing some baseline tests on two as-received boards. The
>>>> Keithley electrometer has settling time constants in the 10s of
>>>> minutes on the higher ranges, above 1e12 ohms. If I walk around the
>>>> room, even 10 feet away, the meter swings all over the scale. The
>>>> "fast" mode doesn't work in my meter.
>>>
>>>Is there a tube in that thing?
>>
>> No, the key part is an old small-signal mosfet.
>
>Did they "nail it" with the first small signal FETs and mosfets? Are there
>new ones that are any more sensitive or would subbing a modern version
>cause problems in old test equipment that expects olden-day
>characteristic?
>
>
>>>I use a Hiportronics teraohm meter, and
>>>it's uh real sensitive to everything. I get the feeling even the binding
>>>posts hurt the sensitivity some too. The whole ground vs guard planes
>>>on the PCB and terminals are weird too.
>>
>> I built a home-made picoamp meter and the Radio Shack binding posts
>> leaked like anything. I had to mount them on a slab of polycarb.
>>
>> https://www.dropbox.com/sh/o6pomayvpoi2r84/AACGPXNj4qf3eG33sbSOGPRra?dl=0
>
>Ha!
>
>What's the white material the components trapeze off? I was expecting the
>old nylon posts, not the "fancy" two-toned ones.

Ceramic terminal strips that were used in the 500-series tube
Tektronix scopes. I scored a box of them at a flea market.

Google for Tektronix 545.

--

John Larkin Highland Technology, Inc

The best designs are necessarily accidental.