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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