I thought I'd try the cheap toaster oven I bought some months ago. I had a
couple of spare PCBs (solder mask and HASL tinning) for my LPC2106 Philips
ARM system (48 pin 0.5 mm lead pitch) so I put a thin strip of solder paste
along each row of pads, positioned the chip on top, getting it as square as
possible, and put the PCB in the oven. I set it for maximum heat (both top
and bottom elements) and left it until I saw the solder start to flow. I
then switched it off and opened the door. About half the pins looked very
good, there were blobs of solder on the others where the paste had been
applied too thickly. Cleaning the blobs up with desolder braid and then
using a fine-tip on my soldering iron with plenty of gel flux to remove the
remaining small bridges didn't take very long. The chip has centred itself
properly on the pads via surface tension, and it looks quite neat. I managed
to lift one pad with the desoldering braid but the pin isn't connected so it
doesn't matter. If I can apply a consistent thin line of solder paste with
the syringe, I should be able to get very good results. Some practise will
probably help or I might be able to get a smaller nozzle.
Leon
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Leon Heller, G1HSM
leon.heller@...http://www.geocities.com/leon_heller