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Old 20th Jan 2019, 2:06 am   #8
Join Date: Jan 2004
Location: Stockport, Greater Manchester, UK.
Posts: 755
Default Re: Hedghog and soldering

In my previous job, we had JBC hot air rework stations (superseding rather unsatisfactory ones using butane cylinders) and some decent flux (smelt like isopropanol) and three effective ways to fit SMDs were:

Soldering iron - Solder opposite corners (22 swg 60/40 multicore solder) then run iron down all pins of one side, adding solder as necessary, until it dropped off the end.

Solder: Tin all pads with solder, much as above, apply flux and IC aligned to less than half a leg out, apply hot air, see solder melt and draw IC into alignment by surface tension.

Solder paste: Dilute slightly with flux, spread over pads, plonk IC on in fair alignment, apply hot air. Tweak alignment using tweezers if necessary. Apply soldering iron (small, pointy tip) to any solder shorts to make them run back up the IC leg.

Replacing ICs was easy: apply hot air until solder melted, remove IC with tweezers and position new one, remove hot air, flood with flux, apply hot air and see solder melt and IC align itself, touch up the odd dry joint with solder applied with the pointy tip to the end of the leg, re-apply hot air to reflow and give a nice smooth finish.

This was just possible by naked eye in my early 40s, but I'd need my "strong" reading glasses to do it 15 years on.
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