General Construction Notes

General Notes - Problems


The most common error with PCB assembly is inserting parts into the wrong holes or incorrectly orientated (polarized components only). Please double check every part before you solder any part into place.

Desoldering parts on a double-sided board is a skill that takes a while to master properly and, if not done properly, can not only damage the component but can also damage the PCB.

If you have put a component in the wrong place, then use wick or a good solder pump to remove the solder from the hole. Resoldering the joint with fresh solder can actually make the solder easier to remove. Once removed, ensure the hole is clear of solder,

Make sure your PCB is free of grease and dirt before you start soldering. An alcohol based cleaner like iso-propanol is a good choice as this will dissolve the grease and dry off quickly. I also use this to clean the board during assembly to remove excess flux that builds up through the soldering process.

You should ensure that your soldering iron tip is at the correct temperature as recommended for the solder being used. Too cool and you will not get the solder to flow properly and will have poor and unreliable solder joints. Too hot and the flux in the solder will burn off too quickly preventing a good solder joint from forming properly and you run the risk of damaging the component. This is particularly true of soft-bodied components like polystyrene capacitors and pcb-mount connectors with plastic bodies.

All resistors should be flat against the board surface before soldering. It is a good idea to use a ‘lead bender’ or pair of snipe-nosed pliers to pre-form the leads before putting them into their places. Try to keep the bend in the leg away from the point where the leg meets the component body as this may stress the joint. Once the part is in its holes, bend the leads that stick out the bottom outwards slightly to hold the part in place. This is called ‘cinching’. This only needs to be a slight bend as the intention is to prevent the component from falling out when the board is turned over for soldering. Also, the slight bend means that should you need to remove the component then it will be a lot easier than if the leg has been bent at 90°.

Turn the board over and solder from the bottom of the board, applying the solder so that the hole is filled with enough solder to make a small cone around the wire lead. Don’t put too much solder on, and don’t put too little on either. Clip the leads off with a pair of side cutters, trim level with the top of the little cone of solder.

Once all the resistors have been soldered, check them ALL again. Make sure they are all soldered and make sure the right values are in the right place.

IC sockets are recommended, especially if this is your first electronics project. We recommend the use of turned-pin sockets as these offer a superior `grip’ on the ic legs and thus better electrical connectivity.

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