Agree with PWB. I thought we were talking about PWA. My mistake.
Joyce Koo
Materials Researcher - Materials Interconnect Lab
Research In Motion Limited
Office:
(519) 888-7465 x79945
Mobile:
(226) 220-4760
[cid:[log in to unmask]]
________________________________
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, January 09, 2012 10:54 PM
To: TechNet E-Mail Forum; Joyce Koo
Cc: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble fluxþ
Hi Joyce - you can accurately measure the amount of moisture in a pwb using a Mettler or equivalent 4 digit accuracy balance. The procedure to do so must be very very controlled and rigidly followed. The IPC-1601 standard lists the protocol for the procedure. We use have used this protocol successfully for many years producing data we use in our production facilities on a daily basis. I would love to have 6 digit sensitivity for the task but that isn't always available or completely necessary.
On a separate note - the cleaning debate shouldn't be about if there is water left on a pwa after blowing it off. As Terry and others have detailed, the real issue is what contaminates are left in the laminate or the soldermask after the tap water or cleaning solution has been removed. There is an immense amount of published data on the subject so there is no need to run another test.
Dave Hillman
Rockwell Collins
[log in to unmask]
Joyce Koo <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
01/09/2012 09:31 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Joyce Koo <[log in to unmask]>
To
<[log in to unmask]>
cc
Subject
Re: [TN] Cleaning water soluble fluxþ
No. the weight of PWA is significantly higher as base weight. You hardly get a good reading on the water retaining on the PWA alone. Your balance is possibly not the 6 digit sensitivity micro balance you can use (the one you required for testing moisture absorption). Most likely, you got 3 digit - 4 digit accuracy balance. Not sufficient. If it is flex, you might have a case (someone still going to say polyimide absorb moisture, so the measurement is not accurate, etc.etc.). my 1.85 cents after 2nd cup of coffee.
Joyce Koo
Materials Researcher - Materials Interconnect Lab
Research In Motion Limited
Office: (519) 888-7465 79945
Mobile: (226) 220-4760
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Monday, January 09, 2012 9:50 AM
To: 'TechNet E-Mail Forum'; Joyce Koo
Subject: RE: [TN] Cleaning water soluble fluxþ
Joyce,
Has anyone else looked into max allowed dissolved contents for public water
systems?
I did look into that, 500mg / L is the max so I used that as a suggest
value in a water weight experiment. There might be some higher but most will
be lower.
Does ANYONE have a scale out there? We can just MEASURE the water retained
on a PCB after a blow off.
Simple enough? Yes, No?
Got Scale?
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Monday, January 09, 2012 8:50 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble fluxþ
Not all of the tap water are the same. Cl smell is significantly higher in
some of the Asia city compare to the north America. The warning sign of
"not drinkable" in the hotel room may indicated more bacteria present in the
tap water. Are you specifying which "tap water" in what IPC specification?
Or location specified? (too complicated for Monday morning before 2nd cup
of coffee. I can't think).
Joyce Koo
Materials Researcher - Materials Interconnect Lab Research In Motion Limited
Office: (519) 888-7465 79945
Mobile: (226) 220-4760
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Monday, January 09, 2012 8:35 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble fluxþ
Terry,
You pooh-pooh tap water but failed to state two important parameters:
1. Dissolved content in tap water. Let's assume it is all ionic in nature.
(500mg / L Seems like worst case)
2. Amount of water that remains on a board (average per sq. inch) after
blow off.
I would love to see the results of a test as you propose. Let us not argue
like CAD Monkeys, let us do an experiment.
I would ask that you weight the PCB after the final blow off of tap water
and then after a hot air dry, the difference being retained tap water
residue. I am very curious as to the weight of tap water contained on a
board after blow off. That should directly relate to final ionic residue and
water ionic content.
I do not have a scale here that is sensitive to where I can measure the
difference. I hope you do.
Does ANYONE on this list have a PCB, water, air gun, oven and sensitive
scale?
Can anyone suggest a sensitive scale I can buy for not too much money? Is
so I will buy one and test.
Thanks,
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry Munso
Sent: Sunday, January 08, 2012 10:51 PM
To: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble fluxþ
I find it interesting that the use of tap water is still being proposed.
Let's look at the residues in tap water in industrial regions. High levels
of chloride, sulfate and and sodium and processing through sand filtration
creating soluble silica globules that hold concentrated pockets of
contaminants. This approached worked with rosin based fluxes in the 90s.
But lets look at the level of circuit sensitivity of today's hardware (where
a half meg ohm drift will shut down a critical circuit and maybe the entire
system) and the effect of residues that are moisture absorbing and
conductive are creating performance problems. I propose that we run a series
of evaluations comparing tap water, to RO water to DI water. Then i propose
that we evaluate the results by ion chromatography using both the C3
localized extractions and bag extractions of our Umpire 2 SIR test board.
Using the IPC SIR conditions of 40C/93% with continuous monitoring to assess
the residue effects. Oh yes it's true that the resistivity drops to nothing
but not due ionic contamination that is found in tap water but the
absorption of CO2 that has no residual effect on the active circuitry. Oh
and if you paid attention I suggested the the board be rinsed with DI water
steam and not tested in my lab so how much simpler can that be.
Terry Munson
Foresite Inc
765-457-8095
On Jan 8, 2012, at 8:11 PM, "Robert Kondner" <[log in to unmask]>
wrote:
> Before you go through the expense and effort of doing DI to clean and
> rinse try doing a tap clean and rinse WITH a blow off cycle. Have some
> ionic contamination tests run afterwards, they will be very clean if
> you have a good blow off.
>
> Washing with Di water is kind of silly, how long does Di water remain
> DI after a wash of dirty boards start? Maybe 100 ms? Wash with tap.
>
> Rinse in DI might help but a blow off of tap water leaves only tiny
> amounts of material even with very hard tap water. It really depends
> on water entrapment issues and then even a rinse is questionable.
>
> Try something simple and measure.
>
> Bob K.
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry Munson
> Sent: Saturday, January 07, 2012 7:44 PM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning water soluble fluxþ
>
> They should look at DI water steam to clean and rinse. We have
> effectively cleaned 2331-ZX flux. With stop steam cleaning. Call me at
765-457-8095.
>
> Terry Munson
> Foresite
> 765-457-8095
>
>
> On Jan 7, 2012, at 6:36 PM, Gary Bremer <[log in to unmask]> wrote:
>
>> I am presently working as an contractor for the next few months then
>> back
> to unemployment, last place I worked was Jet Propulsion Laboratory on
> the Mars Science Laboratory. These are lighted panels for various
> aircraft and the company policy is for J-STD-001/IPC-A-610 Class 3 The
> failure is with miniature T-1 lamps that stop working after going through
an baking process.
> Other boards that use these lamps but use RMA flux do not have this
> problem, I suspect the cleaning process and the flux. They do not
> check ionic contamination and handle the boards with bare hands and
> the operators even know when components are ESD sensitive or not. I
> have recommended they change the cleaning process to an Aqueous type
> batch cleaner but this cost money which they do not wish to spend.
> Their process person believes that their process is fine and something
> else is causing the problem (bad lamps, forming lamp leads, etc.). This
goes against all my knowledge and training.
>>
|
