Are the ball pad lands defined by the solder resist or is there
clearance between resist and pad?

i.e. x-sectionally

resist              resist
       padpadpad
pcbpcbpcbpcbpcbpcbpcb

or



ressist  padpadpad  resist
pcbpcbpcbpcbpcbpcbpcb


If the former then the step caused by the resist can result in
solderability problems on the smaller grid BGA's.

Chris

-----Original Message-----
From: Russ Winslow [mailto:[log in to unmask]]
Sent: Monday, February 08, 1999 8:50 PM
To: [log in to unmask]
Subject: Re: [TN] Defective BGAs?


Jim,
We are seeing it only on plastic BGAs with 63/37 solder balls (so far).
We
too saw it in isolated cases but now we see it all the time.  These are
pads
with no (zero) solder on them and/or pads with a small icicle in the
very
center.  We even see pads with a ring of solder surrounding a non-wetted
center.  The problem is, we now see it on nearly every lot we receive
for
reballing.  Kinda makes ya wonder?


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jim Marsico
516-595-5879
Sent: Monday, February 08, 1999 12:01 PM
To: [log in to unmask]
Subject: Re: [TN] Defective BGAs?

Dear Russ...

This is something I've noticed in the past... I thought it was an
isolated
case.  Could you tell me the types of BGAs you see this phenomenon on?
Are
they predominantly ceramic?  Plastic?  Both?  If ceramic, are the
component
pads on the same level as the ceramic or are they recessed?  What solder
alloy?
Any information you can provide may be helpful.

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