Hi Werner,

Have you ever seen a case of head-on pillow not in the middle (which is
a relatively easy case :-)) but in an outer row? I have and not just
once (the last one was just a couple of weeks ago). So, I think the
insufficient peak temperature isn't always the one to blame :-)

Regards,

Vladimir

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Friday, January 18, 2008 3:43 PM
To: [log in to unmask]
Subject: Re: [TN] SV: [TN] SV: [TN] Solderability of Tin-Gold
Intermetallic

Hi Bev & All,
I do not know why nobody responded to my e-mail. I said:
"Just like George, I am struggling getting an understanding of you
problem.
To me, 'head-on-pillow' solder defects are almost always caused by 
insufficient peak temperature.
If these HOP's occurred essentially near the center of the BGA, you have
your 
answer,
If the HOP's are distributed over the whole array, than the root cause
is not 
insufficient peak temperature unless the whole reflow process is too
low."

I am still betting on insufficient peak temperature. HOP implies a large

pasty range; thus your solder(s) are not near eutectic. Whatever alloy
they 
actually are, the insufficient peak temperature was too low to get them
fully liquid 
to join up.

Werner



**************
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