Well, finally, here is the process of soldering the 240pin FPGA in pictures. Sorry about the quality, but all I've got ATM is my mobile phone camera.
Step 1:
Using 0.3mm solder and a fine iron tip, the FPGA is tacked in place by hand soldering a pair of diagonally opposite (outer) pins. At this stage it is critically important to get the pin-pad alignment on all four sides correct.
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Step 2:
The first row of pins to be soldered are drenched in flux. This is very important. Plenty of flux means little chances of bridging.
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Here is the "bucket" iron tip I was talking about earlier. This a a 'Pace' brand iron and tip; the tip marketed under the TM "miniwave".
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Step 3.
The bucket tip is filled with solder, placed flat onto the PCB at the top of the first row of pins to be soldered. It is then gently and slowly swiped down the row, with the edge of the bucket just overlapping the ends of the solder pads. It is important not to rub against the pins as they are very easilly bent.
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Step 4
The freshly soldered row of pins is given a good wash and clean up with isopropyl alcohol.
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Step 5
Finally, the solder joints are inspected under a microscope. In this case they all look very well done
;with good solder wicking around each pad foot and no evidence of bridging or spluttering.
If there is a little splutter or bridging between pins, the fix is just a simple matter of re-applying flux and reflowing the individual pads/pins under the microscope with the fine iron tip initially used to tack the IC into place.
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Finished:
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