We typically specify "minimum finished 1 oz" weight, which is easily obtained starting at 0.5 oz foil plus normal surface plating, like Jack said.  That allows the fabricator to choose the starting foil weight they want - our designs don't usually get into fine lines/spaces.  When going below .5 oz foil then adhesion to the surface laminate can become a concern due to the smaller tooth.  Also, I believe that 1/8 oz foil is a special-order & costs a bit more.  

If we need extra copper then we'll specify it & hopefully not need 4 mil lines!


Matt Byrne

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Pete
Sent: Wednesday, December 07, 2011 4:49 PM
To: [log in to unmask]
Subject: Re: [DC] Specifying Copper thickness

Jack, that does help,  I have to think of this from another POV.

We don't do heavy copper, 2 oz at the very most, usually 1/2 - 1.  Where I run into questions is when I have 4 mil lines for my BGA but also have some higher current requirements.  Specifying 2 oz foil makes 4 mil lines tricky.  But all I really need is 2oz, I don't care how they get to that - for traces.  But if they start with 2 oz, and I get absolute minimum plating in a high current via, I may have a problem.

So maybe I'm back to the idea of specifying the foil as a 1/8 oz minimum with the final copper weight I actually need, and the plating in holes as another minimum.

I think you may have gotten me to my answer.

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