Forgot to tell you my primitive way of in-room-check-when-operator-is-waiting. I give the surface
or one or two strikes with a cottonpin dipped in aceton. If that changed the bondability significantly,
then I suspect a contamination. If that doesn't change, I'll give the surface some good strikes with a hard
rubber (the kind you used for machinewriting), if that helped, I have a mechanical problem, namely the
asperity or the hardness of the surface, which are both oftenly overlooked. These two stoneaged methods were given to me by a guy at Honeywell (he served 40 autobonders).
Regards / Ingemar
-----Original Message-----
From: Ingemar Hernefjord (KC/EMW)
Sent: den 12 augusti 2004 10:25
To: 'TechNet E-Mail Forum'; [log in to unmask]
Subject: RE: [TN] Hard Gold Plating/Contaminate Question
Dave,
we had a messy situation with goldplated boards some years back. You and a number of
TNs assisted me then, and got my 190 page report on CDROM. Now, we asked ourself same
as you do now, and to make long story short, we used TOFSIMS to get a good map of
all ions present on and in the gold plate. We found a lot, man! My illusion of pure
gold became..just another illusion. But, on the other hand, I also realize what is
quite normal. Hydrocarbons and other carbons were present everywhere!
Can send you some pages offline, just to give you an idea. Refer to
my 292/15961-FCK 115 17.
But, to become a serious 'lubricant' (as Harman names it)that disturbs the wirebonding, is
oftenly not the real disaster, as the pressure per/microunit is high enough to create those
numerous microbonds. Compare with anisotropically adhesive bonded BGAs. The metal particles,
that are members for the electrical connection, are literally swimming in 'hydrocarbons', but
after curing, you have milliohm resistance from BGA ball to PWB.
We saw 'CH' ghosts everywhere, now we feel that such nanolayers are oftenly unavoidable, and
that they are not the primary source of failure. Growing to micron-thickness, the situation
is, of course, changing, but with growing thickness you need no advanced equipment for the
analysis.
(Maybe you can borrow the CD from some of them who got it: David D, Werner E, William C,
Jack C, Ryan G, Kathy K, Georg W, Steven C, whoever is closest to you.)
Ingemar
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of David D. Hillman
Sent: den 11 augusti 2004 22:01
To: [log in to unmask]
Subject: [TN] Hard Gold Plating/Contaminate Question
Hi TechNet! Hey, looking for some help (Rudy, Frank, Gerard, plating
folks). Background: I have a test board which with approximately 80
uinches of wirebondable hard gold plating that is having gold wirebond
process problems. An XPS (xray photoelectron spectroscopy) analysis of a
"good" versus "bad" test board revealed that the "bad" has significant
organic surface contamination for carbon and oxygen in the form of a
hydrocarbon (lots of C-C and C-H bonds). Now the question: can/will a
hydrocarbon species be codeposited into the gold plating thickness? I
understand the surface process/issues but the codeposit question came up.
Dave Hillman
Rockwell Collins
[log in to unmask]
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