Hi Roger,
I don't remember if I went back to you or not, anyway, thanks a lot for
your experienced answer. I save your adress in a box named 'qualified
people and gurus' in case I need your seemingly deep knowhow.
Best CRT regards
Ericsson Microwave Systems
/ Ingemar
> Ingemar
>
> I thought you said you were working with heavy wire? 500uM,
now
> thats heavy! OK, assuming you accept that 100uM is heavy wire,
you
> should have little problem bonding onto chemical Ni (I guess you
take
> chemical to mean electroless?) We currently auto bond onto
> electroless Ni-P under Au. Admittedly, we use an OE machine, and
8mil
> wire (200uM) but it works fine, and foot lifts are extremely
rare.
> You are right in that the high %P can lead to problems due to
> hardness, but using a Au layer can give its own problems. "In
> theory", a well controlled process does not need the protection
of Au
> (and personally I try and keep the Au of any bond pads where ever
> possible)
>
> If you are experiencing a lot of foot lifts at bonding, are
they
> 1st or 2nd bond?, also, look closely at the bond site, and check
that
> you are scrubbing through the Au, it can act as a lubricant and
> actually inhibit bonding .
>
> If the foot lifts occur after heat treatment, make sure that
you
> are forming the Al-Ni intermetallics and not the Al-Au, if the Au
is
> too thick, and the total bonding energy is low, you may just give
> Al-Au bonding, which will decrease in strength over time at
elevated
> temps (due to consumption of the Au layer, and small diffusion at
the
> Al-Ni interface after that)
>
> You say that Delvotec perform reference bonding on galvanic
Ni, is
> it a comparable plating to what you are trying in production?
could
> be its 10 micron thick and nice and soft, could be they are
bonding to
> the Al substrate, and leading you up a blind alley.(sorry any
Delvotec
> reps listening) From experience I have always found that an
> electroless 4-6micron mid phos layer is fine, with or without Au,
this
> has been on both FR4 and ceramic based substrates, with an OE
machine
> for 5N wire 6-500uM diameter.
>
> More detail on the nature of the problem may help, but good
luck
> what ever way you go!
>
> Roger
>
>
>
> Roger Massey
> Materials Technologist
> Motorola AIEG
> Stotfold - UK
> email [log in to unmask]
>
>
> ______________________________ Reply Separator
_________________________________
>
> Subject: [TN] Heavy wire Al-bonding on FR4
> Author: "TechNet E-Mail Forum." <[log in to unmask]> at #email
> Date: 15/04/99 17:52
>
>
> Hi, all 1577 brains (most of them in UK?).
> What a noise this will cause, and hopefully one or two answers will
bang
> into my briefcase.
> Now, we bond 100um Al on Cu/Ni/Pd/Au or on Cu/Ni/Au. Different bath
> suppliers, different makers. Different schools. Some say 10-12% P will
> cause a too hard Nickel, and there will be problems, bond lifts, which
> we also get. Delvotec (bond machine maker, good one)make all their
ref.
> bonding on galvanic nickelplated aluminium plates, and it works fine.
>
> So, electrolytic and pure Nickel is wanted, but the board suppliers
> don't love that, because they have to connect every single bond pad on
> the FR4 board, on which the rest of pads are made for ordinary SMT
> soldering. Anyone who has autobonded on chemnickel (plus Pd/Au or only
> Au)? And are you then satisfied?
>
> Ingemar Hernefjord
> Ericsson Microwave Systems
>
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