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View Full Version : Vaguely OT: Need some SMT soldering help



swinokur
09-14-2003, 04:36 PM
Hey there,

I have a piece of computer equipment that i'm trying to repair. I've narrowed down the problem to one chip, but it's a surface mount - and I don't have the eqipment (or experience) to rework the board properly.

Is there anyone who can point me to someone in the SF Bay area who can do this?

(I woudln't mind learning how to do this sort of soldering, it just seems that the tools necessary to do it right are quite expensive. If someone knows of a cheaper alternative to a $1200 hot air rework station, please tell me! :) )

thanks!

cali
09-18-2003, 07:31 PM
How many pins are there?
There are workarounds depending on size.

swinokur
09-18-2003, 09:39 PM
its a 48 pin qfp, about 9 mm square. Off isn't as much of a problem as on again :)

cosmicpossum
10-12-2003, 10:36 PM
For some general help on surface mount soldering see:

http://www.pegasustech.com/gems/sm.htm

A low cost way of removing an SM IC is to use a butane hot air pen which can be had for < $100. Get some stainless steel shim stock (~ 3 mill) and put it in an X-Acto knife handle.

Heat the IC gently while pushing the shim under the leads. As the solder melts, walk the shim under the row of pens until the whole side is unsoldered. Then go on to the next side and repeat.

Use a flux pen ("no clean" preferably) to coat the area and reheat with the butane pen. This will reflow the solder and leave a nice bed for the new IC.

More flux, then place the new chip and carefully align. Solder in place with a fine tip conventional iron or the hot air tool.

Some people advocate throwing lots of solder down and not worring about bridges, then going back and removing the excess with solder wick. I prefer to avoid bridges but usually end up using solder wick to clean up my mistakes anyway :).

Of course this all works better if you have a stereo binocular microscope.

swinokur
10-13-2003, 01:18 AM
Hey CP: thanks for the tips!

I've already had a friend (of a friend) resolder the offending chip using a SMT rework station. It's *amazing* how much easier a job this is with the right gear sitting on the lab bench.