Hi Colin-

I agree that ENIG isn't great to bond to using either aluminum or gold.  I've done it, but there is normally rework required.

ANY "bondable" surface needs to be qualified.  For PCB's the industry consensus is at least 4microns nickel and 1 micron of soft gold (too much for small solder joints!)

I have bonded to immersion silver with aluminum too (not a great coupling from a reliability point of view).  My gut reaction was that ENIG was better, but that probably varies with supplier.  I've also bonded to bare copper with aluminum (although with ANY oxide on it you get no-sticks).

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of colin mcvean
Sent: Thursday, March 11, 2010 6:51 PM
To: [log in to unmask]
Subject: [TN] Aluminium wire bonding

We have an application which is asking for a ENIG finish with Ni spec of 2-4 um and Au of 0.05-0.1um.

What is the industry expectation of NI specification for Aluminium wirebonding? I think 2-4 is a little on the low side, and am worried about possible Nickel corrosion and poor bonding adhesion, especially if the Nickel is towards the lower side of the 2-4um.

Colin McVean




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