There are many PCB manufacturers preferring the tenting method when placing vias, covering vias with different material allows them to conduct an electrical signal while dissipating any produced heat. Though tenting is not the only method, it’s common for PCB designers.
What is tenting via?
No matter the size, vias connect each layer of a PCB together. Tenting a via means you create a tent-like shape over the hole to cover the via. The purpose of tenting is to limit the number of exposed conductive pads on the PCB.
When a via is tented, the manufacturer used a solder mask to enclose the opening. Tenting a via has both positive and negative impacts on the PCB. If you’re wondering whether or not you should tent the vias on your PCB, it comes down to the design and manufacturing requirements of your board.
Needless to say, tenting via is the most popular and mature process in PCB fabrication, and tenting vias mean to cover the annular ring and via hole with solder mask, which is mainly in covering the annular ring to prevent exposure to the elements and reduce accidental shorting or contact with the circuit. No special steps are taken to ensure the hole opening remains closed. However it will make an effect on the PCB fabrication process if there is not solder mask ink in the vias. With the introduction of dry film solder mask, tenting via is easier.
What are the advantages of tending via?
Firstly, provide the solder mask to the vias as the protection. It can prevent the copper traces from oxidizing and corroding just like the solder mask, and the solder mask does the same thing for the via. So tenting via can make an effect on preventing any damages to the PCB layers.
What’s more, it can reduce the number of conductive components that are exposed to external elements with the tenting method. As left exposed, the elements can reduce the integrity of the components and result in corrosion. As well as play a role in reducing the possibility of a short from happening from solders bridging.
Why Is PCB Via Tenting Important?
PCB tenting vias is a common practice to protect printed circuit boards. It is often preferred over mask plugging or epoxy filling because of cost. The most cost-effective form of via tenting is LPI, or liquid photoimageable solder mask tenting. If you’re very concerned about the tenting coming loose and exposing the annular ring, you may choose to use a somewhat more expensive resin filling.
The main goal of via tenting is to leave fewer exposed conductive pads on the surface of your printed circuit board. This should, in turn, mean fewer shorts brought about during solder bridging during assembly. Another benefit is a reduction of paste migration from SMT pads, which can occur when vias are drilled on standard BGA “dog-bone” patterns or when the vias are on the edges of SMT pads. Tenting will also help ensure that the via is less likely to be damaged by exposure to the elements.
In general, tenting is more effective with small vias (diameter of 12 mil or less), so you need to consider closing the via instead with some kind of fill if you have larger vias that you need to protect. Obviously, it will not make an effect on conductivity with filling the vias because electrical travel through the copper plating is unimpeded.