Steve,
Additonal 2 cents - Back in the olden days of electrolytic plating, it was
not uncommon to see dumbbell shaped pads/traces due to the increase in
current density at the sharp edges of the pads. We did not discuss plating
methods.
My comments with respect to rounded shoulders of the pads seems more like
etchant undercutting the resist. This would lead to less of a flat area to
bond to [that will really hurt the ball bonding wedge]. I've seen this on
many boards once one starts to push line and space minimums to the extreme.
This is also a problem with stamped leads as the metal draws a bit, before
actually being sheared - although certainly not 2 mil wide leads :-) !!!
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Kelly
Sent: Tuesday, August 04, 2009 1:02 PM
To: [log in to unmask]
Subject: Re: [TN] Wire bond
Hi Joyce,
Do not understand your response - why would a .002 etched pad be flatter in
the centre - I have done thousands of x-sections and SEMS - never seen this.
Why would I have exposed copper at an edge- never built a wire bond circuit
that would have that issue. Regards Steve
Steve Kelly
PFC Flexible Circuits Limited
PH: (416) 750-8433
Fax: (416) 750-0016
Cell: (416) 577-8433
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Tuesday, August 04, 2009 12:56 PM
To: [log in to unmask]
Subject: Re: [TN] Wire bond
Yap. The flatness of the center pads is better than the edge, just in case
you have some exposed copper at the edge, that will harden the gold locally.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Tue Aug 04 11:36:30 2009
Subject: [TN] Wire bond
Good Morning,
Does the size of a wire bond pad (in this case with a perfect etch .002
wide) have any effect on whether the wire bonder does Al wedge or
Thermosonic gold( I know the gold plating is different) - just asking about
the process. Thanks. Steve Kelly
Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS)
(416) 750-8433 (work)
(416) 750-0016 (fax)
(416) 577-8433 (cell)
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