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July 1998

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Subject:
From:
"Lamond, Doug" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 7 Jul 1998 08:43:59 -0500
Content-Type:
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Would anyone have a good idea as to the source of copper stains on gold
fingers?
History:
No clean wave and paste flux is used in the process.
Gold fingers were cleaned using Bio-Act SC-10
Nickel thickness under stain is ~ 150 micro inches
Gold plate thickness under stain is ~30 micro inches
Gold porosity test is normal
Stain is copper (EDS and ESCA verified)
Stain seems to migrate from the exposed copper beveled edge although seen on
back row of high density fingers
Stain appears to have a heat induced appearance (brown-red in color)
Sub-K  states PCBs were not stained incoming (???)
PCBs were cleaned then stored in warehouse ~ 3 months
Stain can be removed with eraser, but process not well enough controlled and
potential for contamination in memory slots from eraser.

Thanks

Doug Lamond
Reliability Engineer
Compaq Computer Corp.
281.518.3657
[log in to unmask]

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