Hi,
The solder on the Gold boards looks dull and grainy because it is an alloy
with a solution of Gold. It should not look like HASL or OSP boards. There
are guys on this forum who can give you more detail on this.
You had issues with HASL finish PCBs. I'm amazed you changed technologies
for the reasons stated. I personnally would go the other way. The HASL
(solder) finish should take to solder without any difficulty. The only way I
can think of there being issues is if the coating of solder is less than 0.5
micron thick and intermetalic growth takes place during an earlier thermal
cycle to the extent that it reaches the surface and is thus unsolderable.
This has taken place once in my career but the incident was a one off. The
thickness of solder was low due to the supplier trying to be too high tech.
The levelling system was Horizontal and in an attempt to give a flat finish
the thickness was low. I don't have an issue with HASL dome (20 thou pitch
is standard here, including connectors on large dense assemblies), so I
rather a decent thickness of solder to maintain solderability.
Try changing supplier of HASL PCBs for improved reliability. Are you sure
your problems are down to PCB finish? It is more difficult to solder and
handle OSPs.

Regards

Eddie Brunker
Tadpole Tech,
Ditton Walk,
Cambridge,
CB5 8FN

+44 1223 278200


At 07:53 20/02/98 -0800, you wrote:
>Technetters,
>
>My $.02.
>
>We use fine pitch parts and have a very dense board (12" x 15") and had
>some solderability issues with HASL.  We went to "immersion gold" and it
>got a little better, but the solder looked grainy and dull.  We have since
>gone to OSP and are expecting more improvement.  I have not received any
>
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