What are Tented Vias?

Tenting or capping in PCB means covering the annular ring and via hole with solder mask. Tented Vias are those that are completely covered with soldermask. Via tenting is performed to reduce the number of exposed conductive pads on a PCB which in turn mitigates the probability of physical damage like corrosion and shorts happening due to solder bridging.

Via Tenting has several advantages for Printed Circuit Boards. The solder mask which is used to cover the via to protect the copper traces from oxidizing and corroding. Using Via tenting also reduces the number of conductive elements that are exposed to the external environment. When the interior of a via is exposed to the environment, then the exposed copper could slowly corrode.

Via Tenting should be done on both sides of the PCB, as tenting just one side will result in inside of the via on non-tented side will prone to oxidation and corrosion. Tenting Vias is a cost-effective method of providing protection to the vias and copper around them.

Figure 1 Extreme corrosion due to untented vias

Via tenting has its downsides as well. Since the solder mask which is used in tenting is primarily liquid, there is a possibility of the liquid developing cracks on a microscopic level after drying which creates small holes. They will trap moisture and chemicals which can cause corrosion and damage the PCB.