Cheryl,

To add my 2 cent's in addition to Paul's obliterative tactic, you don't
wanna increase spraying pressure. It has tendency to do the opposite of
what you're trying to accomplish. High velocity water tends to bounce
off from board and skips cleaning tight spaces under and around
components. Try and apply a low pressure and flood boards.

Adding a 5% saponifier in your washing tank will do a wonderful job of
cleaning off chloride, bromide, weak organic acid, sulfate.... In my
previous life, a DOE was performed to prove that just using DI water
will not clean off chemical elements that cause electro migration. We
concluded that min. of 3% saponifier is needed to remove all
contaminants.

What the heck, if nothing goes your way, it's not a bad idea trying
Paul's serious tactic, just equip yourself with a full Ninja armor.

Matthew.


>>> [log in to unmask] 2/10/2004 3:20:04 PM >>>
I've been working on a tough but challenging contamination problem.
The
contamination causes electrical leakage fails on a precision test
instrument. Ion chromatography analysis points to an incoming
cleanliness
problem on a SOT-23 component. Elevated choride and sulfate levels
were
found on the components (5x - 10x greater ug/in2 levels than anything
found elsewhere on the boards). High levels were found even on our
"good"
boards.

We are trying to work with our supplier to identify and fix the
problem
long term but are looking for some short term fixes as well. Repeated
water washing of the boards (high pressure spray cleaning) improves
the
situation but does not fix it. Alcohol scrubs in the area further
improve
it but don't eliminate the problem entirely.

We have a only a DI water wash process (no surfactant/saponifier
capability).Does anyone have any board or component cleaning
recommendations?

Are there any parts makers out there willing to tell me a little more
about parts cleaning after the lead plating process?

What tool(s) do part makers use to verify cleanliness of parts?

I don't have a tool capable of measuring what was found on the part so
I
don't know where to go.

Thanks, Cheryl Tulkoff

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