Hi,

 

I don't fab bare PCB and I know little about the processes. I have a
customer that is a little more "Quality Conscious" so I figured I would ask
around about a few things. Most of what I do is prototype related so I
started asking question at various proto shops.

 

I could not get very good answers about Desmear and Etch back processes. In
fact, it almost sounds like some board houses do not have desmear processes.

 

So, 3 Questions:

 

1.       Is no Desmear possible? Is the copper contact area on interlayer
connections sufficiently clean to where reliable interlayer connections can
be made without a desmear process?



2.       Plasma etch back. Sounds like this is a specialized and highly
improved way for treating holes so plated through barrels make good
interlayer connections. How Much Better is it? Cost?



3.       Drill to Copper spacing is important as copper wicks into glass
weave spaces. Seems like my existing houses demand 12 mil. Some new places
say "We can do 10mil". If I am assuming generic FR4 (it that exists) then
how can someone just kiss away 2 mils out of 12? Should I disregard anyone
with such a light approach to rules? I assume they are using the same drill
bits, material and copper plating techniques. Is that a reasonable approach?

The board in question is 5/5 rules, 8 layer, 8 mil via in 18 mil pad.
Material is .062 FR4 or Equiv. 

 

Thanks,

Bob K.



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