soldering surface mount components

Any tips on soldering surface mount components? have some BC847 PNP/NPN transistors to solder and they are about the size of a gnats butt with
six pins, only need to solder three pins but even this is a micro-surgery job,
regards, Terry
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Terence Lynock (MSW) wrote:

Good luck., Magnifying glass and fine tip and position with a tack of glue first, and use solder paste I believe.
Beyond me mate!
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| | | Any tips on soldering surface mount components? have some BC847 PNP/NPN | transistors to solder and they are about the size of a gnats butt with | six pins, only need to solder three pins but even this is a | micro-surgery job, | | regards, Terry
Use a small 25 watt iron, Tin the pads with a good rosin core solder, ditto for the leads and then you don't have to put too much heat into the circuit board. A touch will do it.
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snipped-for-privacy@zetnet.co.uk says...

Usually what I do, when we are hand stuffing a prototype, is to pick a leg, presolder that spot on the PCB, move the part over the pads and reflow that one spot. You are basically tacking the part down by one leg. If the part shifts, reheat and move. I use a very sharp pick to press down the center of the part. Then VERY carefully solder the other legs. If you short anything out (look at it with a magnifier) use some desoldering braid to pull off the excess solder. I have done some pretty small stuff that way. Solder paste is only really useful if you have a part stencil and are going to use an oven. Otherwise, you are just blobbing the paste on and hoping for the best, so you might as well use some liquid flux and REALLY thin solder. I use .020" which is still kinda' big for some things, but I get by.
Jim
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On Wed, 11 Apr 2007 12:04:44 +0100, Terence Lynock (MSW)

Dead easy, I now MUCH prefer them to leaded comps. What you do need is:
A fine pair of tweezers. A magnifying glass. Good light. A fine tipped iron. Good flux. I use Ersin RMA. Fine solder, I like Alpha .020" Practice.
The process is:
Pre-tin the copper pads with a little solder. With the tweezers, pick up the part and smear a little flux on the leads ( I put a tiny drop on an old microscope slide for this) Position the part on the pads. Tack down one lead to the board. Push it about as required (but just a little !) to centralise it on the rest of the pads Then go around and solder down the rest of the pads, and reflow the first pad. Clean off surplus flux and inspect under the light and magnifying glass
Barry
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