Soldering SMD's

[Rob Zero]

Yes.. just heat the thing up to a point somewhere below the melting point of
the solder (oh, say, 600 degrees F)

Then, take it out, and you will probably have aprox 5-10 minutes to work
with it before it loses so much heat you cant get a decent solder flow.

Solder it by hand and let the solder iron make up the difference, which will
no longer be as much now, since the whole unit will be pre-heated and less
prone to cracking from thermal shock.. 100 degrees F shouldnt be enough to
crack it, which would be the difference between the ceramic and the tip of
your iron..

Rob


----- Original Message -----
From: terry michaels <104065.2340 at compuserve.com>
To: Synth-DIY <synth-diy at node12b53.a2000.nl>
Sent: Saturday, April 15, 2000 2:13 PM
Subject: RE: Soldering SMD's


> I would like to request suggestions on the following problem.  Lately I
> have been working on microwave circuitry, typically replacing a transistor
> or other component.  This type of circuitry is built on an aluminum oxide
> ceramic substrate with parts soldered to metallized traces on the ceramic.
>  The ceramic substrate conducts heat like crazy, so it is nearly
impossible
> to get enough heat into a small solder connection to melt the solder with
a
> small iron.  I can't use a large, high wattage iron to solder very small
> SMD microwave components, it is physically too big.
>
> These circuits were originally assembled by placing all of the components
> on the pre-tinned substrate, and then heating the whole thing in an oven
> until the solder melts.  This is not practical now that the substrate is
> attached to a machined aluminum baseplate.  In some cases the entire
> backside of the substrate is soldered to a metal baseplate.   I have heard
> of people trying to heat it with the concentrated airflow from a heat gun
> to remelt solder connections, but if the substrate is not heated evenly,
it
> might crack.
>
> Any ideas?
>
> Terry Michaels
>
>