In SX Microcontrollers, SX/B Compiler and SX-Key Tool, robotworkshop wrote:

Hello,

The tip doesn't need to be as fine as the pitch of the CPU.  You'll find that the method of soldering all the pins and then going back afterward to clear off the excess with solder wick gives excellent results.  Below are a few paragraphs from the assembly manual for the SX48 40-pin module:

"One of the most important aspects of assembly is the proper alignment of the components.  Some people prefer to use a small dot of glue to hold each component in place while soldering.  If this works out well for you, by all means use that method.  Otherwise the following techniques give excellent results!

Before installing a surface mount component apply a small amount of solder to one of the pads on the PCB where the part is going to be installed.  Then while warming the solder on that pad use the tweezers to set the part in place.  You can do adjustments while the solder is still molten.  If it takes too long, let the solder cool to ensure the part is not damaged by excessive heat.  Once cool the joint can be warmed up again and the alignment can be adjusted until it is perfect.  Before soldering any other joints on the part use the magnifying glass to verify that the alignment is ok.

Components installed on the top of the PCB:

Install the Parallax SX48BD/TQ CPU near the center of the PCB at location U1.  Pin one of the CPU should be orientated toward the upper left of the board.  There is a small mark on the silkscreen, which shows the location. The alignment of this part is critical.  First, tin the iron and tack the CPU in place.  Do not worry about solder bridges at the moment.  Once it is aligned solder one of the pins on the opposite corner. Double check the alignment with the magnifying glass.  If all is well proceed to solder the rest of the pins.  Since the pitch is so close on these pins just solder each side without worrying about solder bridges and let it cool before doing the next.  After the chip cools go back over each side with solder wick to remove the excess solder.  This will remove most of the solder and leave just enough to make a proper connection.  Repeat the process if solder bridges still exist.  Be sure to let the chip cool between each side so the microcontroller will not be damaged by excessive heat.  The results can be fantastic if you take your time."

Everything is step by step and shouldn't be too hard to follow.  If anything comes up let me know.

Best Regards,

Robert

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