piclist 1997\09\08\010215a >
Thread: SMT soldering
www.piclist.com/techref/pcbs.htm?key=smt
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face BY : tjaart@spamBeGonewasp.co.za



Mike Keitz wrote:

> If your hands are steady and your eyesight reasonably acute, you can
> solder typical "coarse" SMT parts such as SOICs, 1206 and 0805 chip
> parts, SOT-23 transistors, etc. one at a time by hand using conventional
> soldering techniques.  I haven't tried it and probably would not
> reccomend it for parts with lead spacing smaller than .04" like QFPs,
> etc.

There is a way... You can solder any SMD IC like this:
1) Solder (sOLDER for mIGUEL) two opposite pins onto the pads to lock
the
  IC into place.
2) Wet all the pins with flux to ensure good joints (not the Jamaican
  type, man).
3) Roll a big blob of solder to and fro accross the pins.
4) Clear all the bridges with solder braid

> The minimum and usually adequate equipment includes: a pencil soldering
> iron with a reasonably small tip (1/16 or 3/32 chisel), a roll of
> small-diameter wire solder, a pair of tweezers, and some desoldering
> braid.  Liquid rosin flux and a magnifying glass are also useful
> sometimes.  If the board or parts have become a little corroded, apply
> liquid flux to all the pads so they will take solder readily.

If you use the above method, you don't even need any special tips. (You
should see mine...)

{Quote hidden}

I fully agree here...

> To remove chip components, the best technique is to use two soldering
> irons to melt both ends at once and lift the component away, Clean all
> the solder from one end using solder braid, leaving the other end
> "blobbed" to install the replacement component.  Advice is not to reuse
> parts that have been removed.  You'll probably lose them in the carpet
> anyway.

And here...

>
> Removal of ICs is difficult.  Start by using solder braid to remove as
> much solder as possible.  If the IC is under 20 pins it may be possible
> to use two soldering irons and braid to distribute the heat to melt all
> the pins free at once.  If not, heat each pin and use a dental pick or
> large sewing needle to bend it slightly so it is clear of the board.
> When the part is off, clean the remaining little bumps of solder off the
> pads.

If you are going to scrap the PCB, there is a fast and safe (for the IC)
way. Turn the board upside down (IC facing down). Heat the top of the
PCB with a really hot heat gun and watch your undamaged drop onto your
desk. Gasp and run to open all the windows (PCB's are generally not made
to smell good at high temperatures.)

--
Friendly Regards

Tjaart van der Walt
RemoveMEtjaartRemoveMEspamwasp.co.za
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