Re:Off Topic: How to manually solder SMD chips?

[Dig <turbodig@yahoo.com>]

---
From: "Jose Carlos Felicio Rublescki"
<rublesck@portoweb.com.br>
Subject: Off Topic: How to manually solder SMD chips?
Hi. Sorry this is off-topic.
Does anyone have experience in manually soldering SMD
chips?
How can I solder without inadvertedly connecting
several pins together?
Jose Carlos
----


Way back in the old days (before I entered the the
dark world of tech support) I did a lot of SMD 
soldering on prototype PCBs. 50 mil pitch was exotic
back then, so YMMV.

Once you cleaned the padfield, I squeezed a little
rosin flux onto the pads. Let that sit for a while,
so it gets a bit sticky.

Place the part carefully, using a tweezers or a 
suction cup device. Make sure the 4 corner pins are 
aligned. The stickiness of the rosin will help hold
the part down, but if you have repeated trouble, a
little dab of rubber cement on the device will hold
it in place.

The parts we bought all had solder tape on the leads,
which made a *world* of difference. Not sure if you
can get them that way in really small quantity, but
you might be able to. 

Anyway, once the part was aligned and stuck down, we
took a full-size heat gun, and shot it through a 
directed nozzle at the whole part. After a few
seconds,
the solder would reflow, go after the flux on the
pads,
and you were done. It was perfect every time, as long
as you aligned the part carefully.

The first time I saw this, I figured the part wouldn't
work once it was done. It never happened that way. If
you think about it, this is pretty much the same
pinciple as the wave machines, only more localized.

It (the heat gun) also works great for removal. Just
blast the part for a few seconds, and it comes loose.
You need to be careful to allow all the pins to flow,
otherwise you'll lift the pads with the pins. You also
have to be careful not to get any unintended parts. :)

We had many nice SMD irons, Pace hot-air stations,
and the like, but none of them beat the heat gun.

Also, if you have the $$, Metcal irons are the nicest
thing you'll ever use. Turn the switch on, and they're
hot... seconds 'til you're ready to solder.


Later,

Dig
turbodig@yahoo.com
(formerly sbarthol@cca.rockwell.com)


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