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April 2000

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 28 Apr 2000 14:57:56 +0300
Content-Type:
text/plain
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text/plain (148 lines)
Walter

Thanks for the explanation. However, it does lead to a question: if organic compounds such as
oxyfluorocarbons are deposited on conductors and can deteriorate the solderability, would this not also
destroy the "bondability"? I can also see that reducing gases could deoxidise metals, but they would
possibly not break down the F-C bond???

Brian

"Dr.Walter Schmidt" wrote:

> Brian
>
> Plasma can also be used with desoxidizing gases, like hydrogen, methane
> and others. In addition inert gases like argon can be used to "sputter"
> off the surface and clean it. In some special cases, even the short UV
> photons, generated within the plasma when He is used as a gas, can help
> to modify a surface.
>
> Plasma cleaning is widely used in the hybrid world to improve
> bondability of metal surfaces.
>
> Solderability is adversely affected by plasma, when organic molecules
> are formed within the chamber and they deposit on the surface. When CF4
> is used, for instance, together with organic substrates and water is
> released from the organic material in vacuum, very stable C-F-O
> molecules may be formed.
>
> Walter
>
> Brian Ellis schrieb:
> >
> > Mike
> >
> > Was this gold-on-gold bonding, aluminium or what? I'm not an expert on plasma cleaning, but I was
> > given to understand that an oxidising gas is used which converts organics to CO2 and H2O. As O, as
> > opposed to non-ionised O2, is a violently reactive substance, this reaction occurs easily, but,
> > equally, M + O > MO (where M is a base metal). Or am I up the pole?
> >
> > Brian
> >
> > Michael Fenner wrote:
> >
> > > I was peripherally involved in this some years ago with a company looking to improve wire
> > > bonding and cleanliness generally. A half an eye was kept on solderability "just in case."
> > > They noted that the type of plasma cleaning, had a noticeable effect on whether surfaces became
> > > more or less wirebondable, but where the work became more bondable there was no change in
> > > solderability. We put this down to the  fact that whether there  was a little oxide, non or a
> > > lot the flux had more than adequate capability to remove it anyway. However if the plasma type
> > > chosen made wirebonding worse it also screwed solderability. We put this down to the fact that
> > > the plasma was chewing off organics and then allowing them to be re-deposited. As this was a
> > > side issue and not the object of the exercise it was not investigated and remained a surmised
> > > comment in the footnotes.
> > >
> > > Hope this helps.
> > >
> > > Mike
> > >
> > > ----- Original Message -----
> > > From: Brian Ellis <[log in to unmask]>
> > > To: <[log in to unmask]>
> > > Sent: Thursday, April 27, 2000 11:41 AM
> > > Subject: Re: [TN] Solderability
> > >
> > > > Raj
> > > >
> > > > No, but it's an interesting thought. I should imagine that some types of
> > > > plasma could be quite active towards oxidising base metals.
> > > >
> > > > Brian
> > > >
> > > > Rajkumar wrote:
> > > >
> > > > > Hello everyone Hope everyone had a good easter break. I need to know,
> > > > > if anyone is working on solderability degradation after plasma
> > > > > cleaning? RegardsRajkumar
> > > >
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