Sam,

	Did anything else change. HASL equipment, like horizontal vs 
vertical.
How do you cool them down after HASL? Warm water / cold water <quench>, 
scrub,
stage for cooling slowly? Baking temps? Material supplier glass source? 
Material supplier press pressure or cycle? Dimensional Stability issues 
are 
always something that plagues us. Generally, we can characterise the 
<I like this word> behaviour and compensate for it accordingly. The 
numbers 
your listing are gross. I'd expect that from a .005" doublesided that 
gets 
relaminated <Not .062">. One thing I do suggest is to try to keep as 
much 
solid copper on the panel as possible. Like breakaways, between parts, 
and 
copper thieve all open laminate areas. This acts as a compliant feature 
and 
helps decrease the movement once the panel is subjected to thermal
excursions. (Tom....is this similar to the solid copper leaders on the 
PWA's?)

My thoughts anyways.

Groovy
  
sam mccorkel wrote:
> 
> My previous posting did not yield any suggestions. I'm submitting again and
> hope to have responses.
> 
> >Date: Fri, 07 Feb 1997 10:25:09 -0500
> >To: TECHNET
> >From: sam mccorkel <[log in to unmask]>
> >Subject: FR-4 material movement
> >
> >We experience up to .020" material movement on FR-4 materials.We ran some
> tests and measured after each operation and found that it began to move
> after etch, and moved a lot more after screen bakes and hot air leveling.We
> have not seperated panels by grain direction in our tests so far. We've
> tried baking before drilling and have not seen a significant difference from
> those not baked. The movement we experience causes major problems when we
> rout or score. We have to internally pin each piece to hold a ± .005"
> tolerance between a drilled hole and the edge of the part.We used to be able
> to pin externally with 4 pins to rout our boards and had no problems.
> Internally pinning adds a lot of labor with panels that have many parts on
> them. This problem cropped up on us about 10 months ago. Before that it
> wasn't a problem. Are other fabricators out there experiencing this same
> problem? Is there anything we can do to reduce the amount of movement?
> Should the material move this much with "normal" processing of 2-sided
> boards that are .062" thick? Do you have to internally pin each part on your
> panels?
> >
> 
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