You are right FR4 should not be punched.  You will see the cracking of the
edges but mostly what I believe you are seeing is the first 100 or so panels
probably looked OK.  After that, the glass content in FR4 dulled the tool
and this is where you get the cracking of the edge.

        Joe J.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of cguitar
Sent: Wednesday, February 16, 2005 11:09 PM
To: [log in to unmask]
Subject: Re: [TN] Cracking FR4

FR4 should never be punched, I believe

At 11:54 AM 2/17/2005, you wrote:
>Hopefully someone in the forum may have had experience with cracking
>along edge of FR4 as per attached photo. The profile of this pcb was
>punched and subsequently the edge has fine cracks through the
>soldermask and glass. We have had a large quantity of this part made in
>China and are concerned that this cracking could compromise the board
function.
>
>
>
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