Stuffing boards with pulled QFP chips

[Jon Elson]

On 03/31/2017 06:28 PM, allison via cctech wrote:
>>>
>>> Is this something that an experienced hand can manually do?
>> Yes, definitely.  100 lead PQFP is perfectly doable if the lead pitch is not insanely small.  It takes a good fine tip soldering iron (mine is a Weller with a PTS tip), fine solder (preferably real, i.e., 63/37 non-PC solder).  Liquid flux is a big help, as is a magnifier and bright light or modest magnification microscope.
>>
>> If you have to do a couple of dozen boards this gets very tedious, but for 5-ish it isn't a big deal.
>>
>>
I have a project I do from time to time using 128-lead 14mm 
TQFPs with 0.4mm lead spacing.
I use a stereo zoom microscope with a home-made LED ring 
light. First, I rub the pads with a pencil eraser to remove 
oxidation caused by reflow temps on the rest of the board.  
I put a tiny dab of solder on two pads at opposite corners.
I then place the chip in place and reflow those pads.  If 
the alignment is not good enough, I can "walk" the chip a 
bit by reflowing one, then the other pad.  Then, I apply 
liquid flux to the rows of leads with a wire dipped in the flux.
And, then solder down the rows with a fine-tip soldering 
iron.  If a bridge develops, solder wick fixes it.

Jon