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Date 10/7/97
Subject HASL Finish
From Maurice Dore
To Technet
HASL Finish
Hi all,
I've experienced extreme cases of non-filling of small vias in a wave
soldering operation.Microsectioning some soldered PCA's reveals voids in the
vias, with copper exposed on the barrel of the PTH at the rear of the void.
Microsectioning of the bare boards show large areas of exposed Copper in the
barrel of the PTH. All through-hole components and larger vias are
unaffected in the process but the bare boards show the same quality of HASL
in their plated through-holes.
Has anyone seen this, any process improvement hints(I'm using low-solids and
this can't be changed???). I've tweaked dwell times to reduce the quantity
of defective vias but I am getting PWBs in which are over 5-6 months old and
the problems are aggravated with their age. Oh.... prebaking improves
quality dramatically, but I ain't got the resources to prebake such high
quantity.
Any suggestions or hints appreciated.
Moss
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