Graham,

I'm getting in this a little late but this is my 2 cents...

We sometimes have problems with SMD pads because the PCBs we get seem to have an organic or foreign material on them after they are processed...
This generates weaker bonds which fail at lower stresses...They can literally pop off the PCB...

Do any of the PCB fabricators have a way of guaranteeing that SM residues are 100% removed from the pad surfaces?

Paul

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kirk, Graham (GE EntSol, Intelligent Platforms)
Sent: Tuesday, March 18, 2008 3:18 AM
To: [log in to unmask]
Subject: [TN] Solder Mask Defined Pad BGA Reliability

Hi All,







Can anybody tell me what the actual mechanism is that propagates cracks
in the device to ball joint on plastic BGA's (Leaded balls) with SMD
pads under thermal cycling?







Graham Kirk



Senior Technologist



GE Fanuc Intelligent Platforms Ltd




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