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May 2008

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Fri, 2 May 2008 13:05:53 +0000
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OK - I don't know much about this FPC - it is 3-4 suppliers back in the chain, still working my way back...
I do now know that there is actually a Ni Layer (3microns thick) with 3microns of Au on top.  The copper is 34microns and the crack on one part (as I have received it) goes through the Ni and about 25% of the way through the Cu.
I will try to get a photo to Steve.
Neil&gt;----Original Message----&gt; From: [log in to unmask]&gt; Date: May 2, 2008 11:41:12 AM&gt; To: [log in to unmask], [log in to unmask]&gt; Subj: Re: [TN] Fw: [TN] Brittle FPC Tracks&gt; &gt; Hi Neil,&gt; Indeed, Au over Ni will result in diffusion. However, while AuSn IMC is indeed brittle and weak and weakens the solder structure, I do not know whether Cu-Au is particularly brittle. it would also be very thin. Ni barrier would stop the Au diffusion, but brings with it a whole new set of problems, among which are a thicker possibly equally brittle Ni layer, Black Pad with too muc P, Ni 'hyper-galvanic' corrosion with too little P, etc.&gt; My question about your problem is—have you determined whether the Cu is not brittle itself. If you use un-annealed rolled Cu, it will be brittle in the cross-rolling direction.&gt; &gt; &gt; &gt; Werner&gt; &gt;&gt;&gt;**************&gt;Wondering what's for Dinner Tonight? Get new twists on family favorites at AOL Food.&gt; (http://food.aol.com/dinner-tonight?NCID=aolfod00030000000001)

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