David,
I can
not say that I have bonded to immersion silver (yet), but have begun to consider
it.
Getting down to only 6 microinches sounds a
little questionable - especially if the boards have experienced reflow, and
have possibly sat around prior to die attach (another bake/cure) and wire
bonding. Are you sure you are getting 6 microinches?? At 6, you
might just as well ask for a "flash" and keep your fingers and toes crossed that
everything will work - and that you did not get 2, 3 , maybe 4 microinches
instead.
With
thin gold, I would expect to see lifted wedges at the bonder (no sticks), and
low second bond pull strengths at wire pull. I would expect virgin boards
to give better results than those boards subjected to any
elevated temperatures and/or staging times prior to wire bonding.
I begin to get really nervous if my 1
mil wires began to have bond failures at <6-9 grams
(depending upon the tensile strength of the wire). Wire
breaks I can sleep with, but the bond lifts scare
me!
Lastly, you have not indicated whether this is the
"first time" you have bonded to these boards (and may still be seeking the
optimium bond schedule and capillary face style/angle), or you have been running
them all along, and just now have begun to have a problem.
Is
your laminate capable of handling the temperature at which you are
bonding?
The
"fifth degree", not intended. :-)
Steven
Creswick
Gentex
Corporation - A Smarter Vision
Hi,
Can anyone share his experience on gold ball
bonding on COB with immersion silver finishings. What sort of silver thickness
to ensure a good bonding strength of min 3.5 gf?
We are using a 1 mil thick gold wire on a 6 to 20
microinch silver thickness and encountered difficulty in achieving the min
bonding strength in wire pull.
Thanks for all inputs.
Best regards,
David.
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