Tracking Down Intermittent Noises And Disappearing Sound

ã 1995~2008 by Eddie Ciletti

An automated process called "Wave Soldering" makes hundreds of printed circuit board (PCB) connections in seconds. Unfortunately, the solder connection alone is often used to make both the electronic as well as the mechanical connections.  Solder is made up of 60% lead and 40% tin, so it can not be expected to do the mechanical job for long.  Designing larger circuit board traces does help to increase the surface area as well as strengthen the pad and the trace leading to it.  To minimize stress to the soldered connections, physically heavy components — as well as all frequently used switches and connectors — should first be mechanically secured to the PCB. 

Figure 1 has been magnified and enhanced to show four solder pads that have potentially cold joints.  Counter-clockwise from lower right, the initial problem isn't so easy to spot, just a slightly "grey" or frosted joint, with each counter-clockwise joint getting progressively worse. 

This is what ultimately happens when a little pressure is applied over and over again via both mechanical stress and repeated heating and cooling cycles.  This would be the case in any studio and especially on the road.  Once in this state, the connector could easily be removed from the circuit board with little effort, without soldering.  Sometimes the solder connection holds up, but the junction of the PCB trace and the PCB pad will break.