Jim Williams

Jim Williams has submitted responses to the following questions.

Glued SMT Components Falling Off
I would be suspicious of the capacitors' surface properties, i.e. contamination. Has your vendor changed ANYTHING in his manufacturing process? ...

Dewetting of Acrylic Conformal Coating
Even though you are using "no clean" fluxes, best practice is still to clean the board. Any residue (even trace ...

What is Causing Oxidation?
I would also be very suspicious of sulfur. For example from a coal fired power plant nearby, and even automobile ...

ESD Protection
I'll equivocate a little bit with my answer. First, I'd like to know what you mean as "ESD compliant bags" ...

Is Rework Unacceptable?
In my opinion, rework can be acceptable for products which perform non-critical functions, or are part of a non-critical system. ...

Delay Before Washing Water Soluble Flux
This is a difficult question to answer, without knowing the chemical makeup of the flux. Oxidation-reduction and/or acid/base chemistry can ...

SMT Adhesive Turning Black
I need a little more info before I can help. What is the adhesive? Who makes it? I can't answer ...

SMT Adhesive Turning Black
I need a little more info before I can help. What is the adhesive? Who makes it? I can't answer ...

Conformal Coating Over No-Clean Flux
I would not recommend that any coating be applied over any surface, without that surface being cleaned to remove possible ...

Laminate Glass Transition Change
The answer is "it depends". Tg is the point at which the polymers become "less solid". Molecular movement increases above ...

Conformal Coating Cross Contamination
I would cure the silicone coating LAST and in its own oven. Urethane and acrylic are fine in the same ...

Conformal Coating and Moisture Absorption
It depends on the relative humidity of the environment,..drier is better. The board surface will absorb water relatively quickly (minutes ...

Abrupt Decrease in DI Water Resistivity
Without more info this is a hard one. I would immediately suspect either equipment malfunction (detectors) or more than likely, ...

Pros and Cons of Cleaning No-clean
In my opinion, "no clean" is a myth, at least the cases I have encountered. There are still oxidation residues ...

Solder Mask Contributing To Solder Balls
From my perspective as a chemist, the solder balls form when the surface tension of the solder mask will allow ...

Flux Residue Causing Test Issues
"No Clean" is a complete misnomer. If you want solid test results you will need to clean off the residue. ...

Gold Plated Lead Discoloration
Can the discoloration be removed by cleaning with a solvent (such as acetone), i.e. dip a 'Q-tip' in acetone and ...

Can Water be Harmful to Electronics Components?
As usual, the answer to a broad, all encompassing question starts out with "...It depends..". Water is an excellent solvent ...

Organic Flux Residue Concerns
My answer begins with "It depends..." Flux residues can contain relatively benign carbon-based materials( i.e. organics left behind or resulting ...

How To Mask Areas During Conformal Coating
Masking is still the best option. But the masking can also be done with precision placement of a UV cured ...

APEX Trade Show Feedback
Cautious optimism is the general feeling I got. ...

Cause of Pin Hole Rejects
Without knowing the chemistry, it's hard to be certain. However, pinholes are caused by outgassing of volatile materials. These are ...

Cleaning No-Clean Solder Paste
A question back. If it is truly no-clean, then why clean it? I would suggest talking with the manufacturer of ...

Problems with Bubbles in Conformal Coating
Without knowing specifics it I shard to solve the problem. However, here are a few 'tips':Is there any chemistry in ...

Contamination Prior to Conformal Coating
It all depends on what the "pink material" is, and how it was manufactured and stored. The only way the ...

Contact Pin Corrosion Problems
I guess I need more data... What kinds of environments are the boards in during the 2 years... Also, it ...

Cause of Unusual Contamination?
It is impossible to figure out what this is without more data. It looks like moldew or mold, or corrosion ...

Concerns Using Aluminum Flux Tank
It is possible for contamination to occur, very much so. Aluminum is an active metal. It will react under both ...

Epoxy Bonding Problems on RoHS Boards
It all depends on the composition of the new board material vs. the old, as well as the surface tension ...

Concerns Using Hand Sanitizers
Absolutely you should be concerned. Oils, both natural and those in various sanitizers can easily cause surface contamination on sensitive/delicate ...

Hot or Cold DI Water Rinse
The answer is "It depends"... Hot water will dissolve residues more quickly than cold water. In a time-critical process step, ...

Hard Water Contamination
If it is from hard water, it can be restored by using a solution of pure water with a chelating ...

Delamination dilemma
I'd be very suspicious of defects in either the adhesive or the surface it's being laminated to. The adhesive defects ...

Defective solder joints on HASL boards
I would be very worried about either a surface contamination, or a change in surface tension at or around the ...

Can adhesive residues from tapes contaminate a cleaning solution?
The answer is an unequivocal "maybe." It depends on why the tapes fell off in the first place. For example, ...

How to eliminate micro solder balls?
Try a different flux. We have seen similar effects on such mundane things as barcode labels on the board surface. ...