Keyword: pcb, pcb board, printed circuit board
A Disturbed joint is pcb board one that has been subjected to movement as the solder was solidifying. The surface of the joint may appear frosted, crystalline or rough. Often called a 'Cold Joint'. They can look similar to a true cold joint, but the cause is different pcb board.
Repair: pcb board This joint can be repaired by reheating and allowing it to cool undisturbed. Prevention: Proper preparation, including immobilizing the joint and stabilizing the work in a vise can prevent disturbed joints. Cold Joint A 'Cold Joint' is one where the solder did not melt completely. pcb board It is often characterized by a rough or lumpy surface. Cold joints are unreliable. The solder bond will be poor and the cracks may develop in the joint over time.
Repair: Cold joints can usually be repaired by simply re-heating the joint with a hot iron until the solder flows. pcb board Many cold joints (such as the one pictured) also suffer from too much solder. The excess solder can usually be drawn-off with the tip of the iron. Prevention: A properly pre-heated soldering iron with sufficient power will help prevent cold joints. Overheated Joint pcb board At the other extreme, we have the overheated joint. The solder has not yet flowed well and the residue of burnt flux will make fixing this joint difficult.
Repair: An overheated joint can usually be repaired after cleaning. Careful scraping with the tip of a knife pcb board, or little isopropyl alcohol & a toothbrush will remove the burnt flux. Prevention: A clean, hot soldering iron, proper preparation and cleaning of the joint will help prevent overheated joints. Insufficient Wetting (Pad) These two joints both show signs of insufficient wetting pcb board of the solder pad. The solder has wetted the leads nicely, but it has not formed a good bond with the pad. This can be caused by a dirty circuit board, or by failing to apply heat to the pad as well as the pin.
Repair: This condition can usually be repaired by placing the tip of the hot iron at the base of the joint until the solder flows to cover the pad pcb board. Prevention: Cleaning the board and even heating of both the pad and the pin will prevent this problem. Insufficient Wetting (Pin) This solder in this joint has not pcb board wetted the pin at all and has only partially wetted the pad. In this case, heat was not applied to the pin and the solder was not given adequate time to flow.
Repair: This joint can be repaired by re-heating and applying more solder. pcb board Be sure that the tip of the hot iron is touching both the pin and the pad. Prevention: Even heating of both the pin and the pad will prevent this problem. Insufficient Wetting (Surface Mount) Here we have three pins of a surface mount component where the solder has not flowed onto the solder pad. This is caused by heating the pin instead of the pad.
Repair: This is easily repaired pcb board by heating the solder pad with the tip of the iron, then applying solder until it flows and melts together with the solder already on the pin. Prevention: Heat the pad first pcb board.
