In a printed circuit board (PCB) production run, the components are not manually soldered. The soldering in the manufacturing process uses the same principles employed in the prototyping process but draws on some heavy-hitting machinery to get the job done. The use of machinery in the soldering of components does not guarantee that there will be fewer errors than there would be with hand soldering. Soldering in the manufacturing process requires extreme precision that can only be achieved through a carefully controlled environment. And even the most careful efforts can still yield soldering errors; it’s simply the nature of the process.
Here are some of the most common soldering issues that can affect PCBs:
This common problem develops when a trace of solder adheres to the PCB surface during the soldering process.
This issue occurs when two solder joints are connected. The unfortunate result is a short circuit. Bridging occurs when weight is not distributed evenly on the PCB design, when components are facing the same direction, or when there is insufficient space between the pads and the solder mask layer.
In the course of wave soldering, the board may raise up off of its base, giving the appearance of a tombstone. This effect may be triggered when the lead length lifts the solder bath or when solder is applied to a flexible board, with the board bending even as the components stay flat.
If solder drains slowly from the soldering device, the solder could build up in excess. This creates what are referred to as solder flags, and they can hurt the board’s function.
Solder should be applied to all surface mounts, but sometimes they get skipped, and you end up with unconnected components. This can be caused by the gassing of the flux underneath the board or the use of incorrect wave heights.
Sometimes when a board passes through a wave soldering machine, it picks up too much solder, compromising the board.
This problem won’t detract from your board’s function, but it won’t look pretty. When a manufacturer uses different types of flux materials or changes solder masks part way through the soldering process, you could end up with a discolored mask.
Manufacturers must monitor for soldering errors in the course of the production process and remedy the problems immediately. Otherwise, a whole run could be taken down, leading to wasted money and frustrated customers.