Another option would be to utilize a dry soldering (no flux) technique
such as the PADS (plasma assisted dry soldering).  The nice thing about
this process is that it can be done on a "closed" container with no
outgassing as there's no flux to react.  Contact Glenn Rinne at MCNC
(919-248-1941 or [log in to unmask]) for more info.


> ----------
> From:         Guenter Grossmann[SMTP:[log in to unmask]]
> Reply To:     TechNet Mail Forum.;Guenter Grossmann
> Sent:         Monday, September 08, 1997 12:39 AM
> To:   [log in to unmask]
> Subject:      Re: [TECHNET] Soldering of cap to a cylinder
>
> Dr. Isaak Baber wrote about a problem with soldering a cap to a
> cylinder
> hermetically.
>
> Unfortunately the text doesn't make any statements about the size and
> mechanical stability of the assembly but I think, the best way is to
> get
> rid of the flux. One possibility I could imagine to work is to have
> tinned
> ( or tin-leaded don't know how to say in English) surfaces and having
> the
> two parts produced with mechanical tolerances to form a slight
> press-fit.
> After assembling the two parts a pass through a reflow oven should be
> sufficient to form a solder joint. This will still leave the problem
> of
> oxidized tin. One solution would be to assemble the parts in a
> reducing
> atmosphere or in nitrogen after having the parts held in a reducing
> atmosphere for a while ( complicated ).
> A weird idea I had would be to cover the leaded surfaces with gold.
> One has
> to care about the thickness of the gold compared to the solder volume
> though. I know, this does mean that the parts have to be assembled
> within
> reasonable time after plating (growth of intermetallics to the surface
> which will make soldering difficult) but I think there would be enough
> time. Thanks to Phil. I know now how to spell intermetallics. Maybe he
> could give a comment about the growth-rate of the intermetallics.
> Or maybe, it is sufficient to simply press the two parts together
> since
> while doing so both surfaces will be deformed cracking the tin-oxide
> layer.
>
> Best regards
>
> Guenter Grossmann
>