Dear Technetters:

I have a customer processing a double sided .040 panel with SMT pads on
both sides and limited through holes, which fails the plated through
solderability test after HAL.   The process is as follows:

1.  homemade sodium persulfate microetch with 2-3% Alpa Metal "Copper
Brite",
the immersion time is modified based upon the etch rate to achieve 30
microinch copper removal.

2.  City water rinse, tripple cascading.

3.  Warm air dry.

4.  HAL Flux

5.  Teledyne horizontal HAL, 3-6 seconds at 490 F.

6.  7-8 second delay on horizontal air-bed to a 120 F water rinse, then
dry.

After HAL the copper coverage and appearance is good, but upon solder
float testing, random pads will not accept solder. Additionally, after
solder float testing a small number of pads that did not accept solder
also appeared to pull back from the edge expsoing the underlying copper.

Any thoughts would be appreciated.

Regards,
Ted Stern

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