[R-390] Silver solder

[Dan Merz]

Hi,  in case anyone was confused by the term "silver solder",  as I was,  I
might offer some clarifcation.  In my work experience,  which was largely
metallurgy,  the term "silver solder" referred to a high melting copper-zinc +
some silver, a brazing alloy, that melts above 1100 deg F.  So I wondered where
this discussion was going to go.  I think this would be entirely out of the
question for radio wiring connections done in place on a chassis.  However,  I
now remember that there is an electronic "silver solder" which is basically
62/36/2 lead-tin-silver,  which I assume is the beast being discussed here.  It
has a slightly higher melting temperature, about  372 degrees F,  higher than
ordinary 63/37 lead-tin which is designed to have the  lowest melting point
(eutectic)  of 361 F for any lead-tin alloy.   Minor addition of silver doesn't
raise the ultimate melting temperature much and is still in the realm of
temperatures that can be tolerated for on-chassis wiring.  One of the cited
advantages of this silver solder is better strength and less tendency to
dissolve silver off  contacts when a connection is made to silver-coated
metal.   Because it is off the eutectec composition (where everything melts at
once)  it will tend to exhibit a mushy melting characteristic and may be more
difficult to start melting because  very silver-rich regions may have formed
within it depending on how slowly it was solidified the last time it was
melted.    For what it's worth........ Dan.

Jim Brannigan wrote:

> The only time I used Silver Solder in a radio was to connect a BNC to a
> circuit board in an HT.
> Flexing of the antenna kept breaking the tin/lead connection, silver fixed
> it.
> With a good mechanical connection the strength of silver is
> unnecessary.....and the additional heat to solder it undesirable.
>
> Jim
>
> > Is silver solder recomennded for any of the joints?
> >
> > I have just re-capped the AF module.  There are so many mechanical grounds
> > in this set!!  What makes it worse is the fact that the chassis is
> aluminum.
> > Aluminum oxidizes and makes for poor connections.  Aluminum wiring in a
> > building is an electricians dream--lots of service work.  A special
> compound
> > is now required for aluminum connections.  Why should this radio be
> > different??  Boy it just looks like a lot of intermittent and hard to
> trace
> > problems in the making.  I am loosening all pertinent
> > connections....applying Deoxit....then re-tightening.  Would seem foolish
> > not to while each module is on the workbench getting rebuilt.
> >
> >
> > Scott
>
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