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December 1997

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Subject:
From:
Greg Finlay <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Thu, 18 Dec 1997 14:55:34 -0500
Content-Type:
text/plain
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text/plain (36 lines)
What if any are the repercussions of clearing solder out of via holes
with a laser?
Would there be barrel damage due to localized heating effects? (6
layer,1.59mm thick pcb, 0.343mm via hole)
What should we be looking for?
Any test results documented?


Background-

Solder mask openings for the vias were added for prototypes by their cam
operator, but when moved to the production facility, this procedure was
not transferred. First shipments (thousands) had no solderball problems
even though vias had no openings for the LPI soldermask (Enthone DSR3241
I believe).
Pcb's were reflowed with no components or paste to ascertain if it was
an assembly issue. Many large solder balls appeared.
There are approximately 800 vias on the board and apparently, it takes
about a minute to clear the via holes out each board with the laser.

Cheers,

[log in to unmask]

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