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Another Teaching Moment: Soldering

Do you have everything you need to solder, but are unsure exactly how to go about it? This article will go over the basic process of soldering to get you started. At the end of the article is a link to our soldering demonstration video to help give a visual of the process as we solder a kit using the Hakko FX888D soldering station.

First, before anything else, put on safety glasses and turn on a fume extractor. Safety is of the utmost importance. Then, go ahead and turn on the soldering iron to let it heat up. The temperature of the iron is dependent on the components being soldered and type of solder. Leaded solder melts at a lower temperature than lead-free solder, but some people prefer lead-free for health reasons. If your iron’s temperature is adjustable, set the iron to 700F for leaded solder, or 750F for lead-free. The solder station should either have a sponge or brass wool to clean the tip. After the tip has been cleaned, put a small amount of solder on the tip to “tin” it and clean it on the sponge again. The tip should be clean and shiny, otherwise a bit of tip-tinning paste can be used if needed. NEVER use anything too abrasive on your solder tip. There is a protective metallic coating that covers the copper, and if it’s removed, the copper will oxidize and damage the tip and it will need to be replaced.

Once the above steps have been completed, place the soldering iron on one side of the pre-placed component lead and pad to heat them, then place the solder on the other side until enough solder has melted onto the connection. A good solder joint will look like a “hershey kiss” and make contact with the pad on the board and the post. See the image below for examples of good and bad solder joints.

Solder Joint

The first joint has made a strong connection with the post and pad. Joint A is called a “cold joint” because the pad wasn’t heated, preventing the solder from making contact with it. To fix this, just place the tip of the soldering iron on the joint until the solder flows, covering the pad. Joint B has too much solder. Joint C has insufficient wetting of the post. This either means there wasn’t enough heat applied to the pad and post for a long enough amount of time, or one of them was dirty. To fix this, just place the tip of the soldering iron on the joint until the solder flows, covering the pad. Flux may help clean components that have oils or dirt on them. Joints D and E have a “short” or “bridge” between the two. To fix this, use solder wick to remove enough solder to correct the issue.

For more instructions and a demonstration on good soldering practices, take a look at our video, below. Two of our technicians solder a circuit board kit while another goes over safe soldering practices along with tips and tricks.




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