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April 1999

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Subject:
From:
"Au Po Lam, Benny" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 9 Apr 1999 08:40:20 +0800
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Hi everyone,

I am studying the tool life of capillaries in the thermosonic gold wire bond
process. The PCBs I used are low-end FR-4 or tetrafunctional for MCM
packages and therefore the bonding temperature is kept at 120 degC max. The
gold plating thickness varies from 0.5 to 1um or even less and the nickel is
above 3um. The capillary has a matte finish. No matter which plating finish
is used, I found that under the same bond schedule, a break-in is required
for the stitch pull force to stabilize. I also found a layer of metal
build-up at the tool tip and suspect that this build-up should enhance the
reaction of the wire with the substrate metallization.  I've asked the
capillary vendor and he also realized this phenomenon as reported by his
customers.

Do you have the same experience? What is your observation and explanation
for this?

Regards, Benny.

Wire Bonder Process Eng'g
ASM Assembly Automation
Tel    :852-26192844
Fax   :852-26192159
Email :[log in to unmask]

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