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Subject:	Re: Lead trimming, BGA rework, and Nortel - I'm baack!
From:	Earl Moon <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Tue, 6 Feb 2001 19:33:25 -0600
Content-Type:	text/plain
Parts/Attachments:	text/plain (43 lines)

Bev,

You are back. Damn good to see from you again and gainfully employed whether
self or otherwise.

Not much data difference to 500 thermal and/or mechanical cycles to failure
concerning solder paste or paste flux. We know the closer we get to columns
instead of balls/pumpkins the better the long term reliabilty. CCGA's go on
forever as IBM would put it and as evidenced by our testing at
Celestica/Cray. Don't have good/much data concerning solder paste as
"bigger" solder globs.

Other factors come back to haunt. Voiding, or not, and where/how many, in
what locations still out for comment but not of too much concern when
surface solderability conditions right together with all other factors (the
same drill as profiles, paste, solder termination area coating/plating,
wetting, TCE, IMC, etc.)

Had no reported field failures at HP with BGA's of all pitches, CSP's,
uBGA's. Ho internal rejects for CCGA's at Celestica/Cray/SGI but no reliable
field data concerning returns. Some data from HAST/HALT but must be
considered as a function of stand still super computer stuff with little
environmental change, thermal differences, or mechanical shock. Still,
columns approximate wires and are very compliant absorbing most CTE mismatch
unlike BGA's. And on it goes.

Keep the cards, CD's, and letters coming. If exceeding 1600, I'll just pace
myself over the next 1600 days, weeks, months, or years as required but no
worries so far.

Earl Moon
Proof Of Design

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