Bagotronix Tech Support wrote:

I can solder 0.5mm (19.685 mil) SMT IC's by hand no problem. BGAs are a

different story...

I can do that too. And my hand can slip, causing a solder bridge to an
adjacent pin. It's a PITA to clear away that solder bridge from those small

I have developed manual techniques to do these, and they work quite well. I'm
still fine tuning it, but I'm doing pretty well with it.

What I do is manually squeeze out a VERY fine line of solder paste with standard
syringe and a fine needle with the point ground off. I lay this line around the
outer perimiter of the component pads. I then place the chip with tweezers, and
solder 2 diagonal corner pads. I then inspect the alignment on all 4 sides, and walk
the chip, if needed, one pad at a time. When all 4 sides have their pads aligned,
I just slide the soldering iron down the rows of leads, at a rate of about 2 pads a
second. If the right amount of solder has been deposited, there are NO bridges.
If too much solder paste was applied, you will get bridges. The best way to fix
them is to remove some solder with fine desoldering braid that has been dipped
in liquid rosin flux. Then, you heat both leads at the same time, and the rest of
the solder will pull into the pad/lead area, breaking the bridge. (If the bridge is
small, reheating the two leads simultaneously may clear it without the braid.)

I then apply isopropyl alcohol to an old toothbrosh, and brush the leads vigorously,
and wash in water from a sink sprayer nozzle. It looks professional, like mass-
produced boards.

Oh, how I long for DIP and 50mil SMT packages.  I figured it out - it is
possible to put an ethernet chip into a 28-pin package (with an 8-bit wide
uP interface).  So why doesn't anyone do it?  They have 100+ pins.  Phooey!

Yup, but the old days had entire boards covered with DIPs to do what I can do now
with ONE very pedestrian Xilinx Spartan chip. And, if there is an error (there is
ALWAYS an error or two) I can fix it in the configuration of the FPGA, and don't
have to even hack a trace on the board, most of the time!

(Of course, there was that one time I used a Protel PCB library part without checking
it, and found out that Xilinx used a different convention with regard to pin 1 being on
a corner or center of the side. That one I couldn't fix with even a complete config.


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