Analysis of open circuit on PTH holes

PTH holes are very important in PCB board, because they are either used to connect different layers of circuit tracks, or used to solder DIP components, or the combination of both functions. However, the copper on PTH holes is more difficult to control and test than the outer layers, so it is more often to have defect on PTH holes.

There are several reasons may cause open circuit or defect on PTH holes.

1. The rough surface of hole wall. The surface of holes may be too rough or uneven without proper treatment. So some places may have very thin copper, and this thin copper may be etched in later process.
2. The impurity attaches on the surface of hole wall. The impurity may cause thin copper at this place, or the impurity may be removed together with part copper from the hole.
3. The thin copper at the connection place between hole copper and track copper.
4. Over etching of PTH copper. The PTH copper may be over etched without proper protection during etching process.

Below are some possible solutions to improve the PTH copper.

1. Make the hole surface smoother, by good quality drill bits, and or proper settings of drilling machines.
2. Wash the boards before copper plating, in order to remove the impurities as much as possible.
3. Proper desmear process to remove the raised or outstanding resin on the surface of holes. This desmear process is usually integrated as part of the whole copper plating process. It is effectively help to make the surface smoother.
4. Proper copper plating and pattern plating process control, like proper portion of plating liquid, plating time, and so on.

SDY is experienced in PCB manufacturing, with rich experience of the possible defects and solutions of those defects on PCB products. Kindly please feel free to contact our engineers or sales Alex@sdy-pcb.com for any questions or RFQs.