Roughness on a "micro-" scale could help wire bonding strengths, but 
     you aren't likely to have enough gold to withstand a pumice scrubbing 
     operation. 
     
     
     Matt
______________________________ Reply Separator _________________________________
Subject: Re[2]: FAB:Wire Bonding
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    10/16/96 08:25 PM


     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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