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Besides hardness, our customer has indicated that underlying copper
surface topography (i.e., roughness) is a key factor - that, for
example, different surface prep methods prior to Ni/Au electroplate
(e.g., peroxide-sulfuric u-etch, persulfate u-etch, pumice w/ brushes,
pumice w/out brushes, even panel orientation relative to the
brushes!!) will affect wire bond yields. Can anyone corroborate
this?? And if this theory holds, wouldn't a final pumice of the
plated gold surface itself improve things further? Is there a
softness threshold below which an abrasive slurry could contaminate
the gold??
J.Felts
PC World, Toronto
______________________________ Reply Separator _________________________________
Subject: Re: Wire Bonding
Author: [log in to unmask] at INET
Date: 10/16/96 3:06 PM
We also monitor Knoop hardness of the plated deposit from our soft
gold bath on a monthly basis. Knoop hardness should be under 80 knoop
for gold wire bonding.
Kim
Hadco Ca.
______________________________ Reply Separator _________________________________
Subject: Wire Bonding
Author: [log in to unmask] at SMTPLINK-HADCO
Date: 10/15/96 7:08 PM
Advice please !
Is there a quantitative test that can be carried out on soft gold electroplate
to qualify its suitability for wire bonding ?
Gold thickness and purity already to customers spec.
Note in this instance gold is on a nickel undercoat.
Jim Douglas
Kam Circuits
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