How To Solder Lead free…

In my limited experience with hand soldering on micro-sized circuit board pads, adding any additional solder greatly increases the chances of creating short circuits from excess solder remaining on the pins or pads.

A small amount of liquid flux is adequate, and I mean barely more than a slight trace of flux, because a drop is way too much, and will prevent good visibility.

I generally use a toothpick with a little liquid flux on it, but much of it wiped onto a scrap of paper to leave just a thin coat of flux on the toothpick, then dragging the toothpick along one side of the IC, followed by a close inspection to see that a tiny amount of the flux is on each pin or pad, and then proceed to apply flux to the other sides of the IC.

I can’t work on items that small anymore without magnification and very good lighting, and wouldn’t attempt it without a good magnifier lamp, even with great eyesight.

Just touching a clean, hot soldering iron tip on the connection is normally all that’s required for complete reflow of the existing solder. If there is excess solder on the iron’s tip, it will likely cause problems.

With enough magnification, it’s easy to determine if the proper reflow has been accomplished. If any of the connections appear to have too little solder for a reliable connection under close inspection, then it may require the application of a very slight amount of solder.

Adding the solder can be tricky, but remember that it’s probably going to be easier to add too much, than it will be to remove the excess, so just wet the iron’s tip enough to get a little solder to transfer to the connection. The liquid flux will insure that transfer takes place.

I would use ordinary flux core 60/40 solder on the iron’s tip, or a very small amount of paste solder, of the type intended for surface mount components applied to the pads (only if needed though).


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