Steve,
Surface finish does cause issues with ENIPIG, as far as I'm concerned, but
there really is very little you can do about it (up to a point).
Bonding to ENIPEG on a mirror smooth surface is always easier... It is just
getting there that is the $$ problem.
The platings are so thin, they will always reflect the underlying surface
finish.
This is another factor in your qualification matrix. Not to trivialize it,
but this ultimately becomes something you have to live with/work around.
With electrolytic gold you masked many of the asperities with a nice cushy
layer of gold and didn’t even think about it.
Can surface roughness cause an issue? Yes, but I see it more along the
lines of abrasion caused during packing and shipping. If no interleaf paper
is placed between the panels [and sometimes even if there is], the panels
rubbing back and forth tend to polish off the gold and palladium, exposing
the underlying Ni at the peaks. The nickel oxidizes and affects
solderability and wire bondability. No amount of realistic plasma cleaning
remedies that!
But with proper handling and storage even slightly 'rough' surfaces are
quite bondable - provided you don’t have the nickel oxide problem.
My two bits
Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
616 834 1883
-----Original Message-----
From: Steven Kelly [mailto:[log in to unmask]]
Sent: Monday, January 19, 2015 12:18 PM
To: TechNet E-Mail Forum; Steven Creswick
Subject: Re: [TN] ENEPIG & Gold wire bond
Thanks Steve,
I have had one complaint that the nickel is too rough - looks like surface
co-planarity is +/- 2 microns which too me is nothing and from further
analysis follows the contour of the copper underneath which easily meets the
IPC spec - should this cause an issue? Regards Steve
On 2015-01-19, 11:56 AM, "Steven Creswick" <[log in to unmask]>
wrote:
>Steve,
>
>The short answer is not too much.
>
>You should be able to develop a robust bond schedule to the ENEPIG (but
>I guarantee you that it will be at least somewhat different than your
>bond schedule to soft gold). Under no circumstances should you assume
>that it is a plug and play alternate.
>
>You should not have to spec any differences in wire properties.
>
>You may look into changing the face angle of your capillary and inner
>chamfer as part of your qualification testing. Depending upon your
>current bonding tool, you may also take a look at increasing the outer
>radius of the tool.
>
>ENEPIG is 'hard' in comparison to pure soft gold, so if currently
>running with a 15° face angle, look at 8°. If you have problems with
>tail formation, you may look into a 120° inner chamfer instead of a
>90°. If you are getting a lot of heel breaks at the second bond,
>increase the outer radius ..... all stuff you most likely are already
>looking into.
>
>Final comments - ENEPIG is not totally without issues. Some days, some
>lots, just plain sucked! There is no other way to say it. Get a
>reliable plater. Work with them. Stay with them. Don't let
>accounting take you to the cheapest place in town - you will regret the
>grief you will have.
>
>NOTHING bonds like clean, pure, soft gold!!! It IS the Cadillac!
>
>
>Steve Creswick
>Sr Associate - Balanced Enterprise Solutions
>http://www.linkedin.com/in/stevencreswick
> 616 834 1883
>
>
>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Kelly
>Sent: Monday, January 19, 2015 11:22 AM
>To: [log in to unmask]
>Subject: [TN] ENEPIG & Gold wire bond
>
>Hi All,
>When wire bonding with 1 mil gold wire is their any difference in wire
>bonding technique on ENEPIG versus electroplated soft gold?
>Thanks. Steve Kelly
>
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