Vias in Pads
If you are designing a PCB for manufacturing, then there is a good chance that you have considered using via in pad technology. This technology aims to minimize the number of holes in the board, increase the density and allow for a more efficient connection between the layers. However, this approach is not without its drawbacks, including increased manufacturing costs and longer turnaround times. It is therefore important to carefully consider your design requirements and choose the right type of via for your project.
Firstly, the process of creating vias in pads requires additional steps and material costs than standard PCB fabrication. In particular, it requires specialized drilling equipment capable of producing small-diameter vias with high precision. It also requires specialized plating techniques to ensure reliable conductive paths within the vias. Furthermore, it is essential to follow rigorous quality control practices during the production and assembly processes to prevent solder wicking into the vias or pads and to avoid other defects such as thermal stress on components.
Another major concern of utilizing via in pad technology is the fact that it significantly increases the cost of a circuit board. To create a via in pad, you must first drill the hole in the pad, then fill it with a non-conductive epoxy or a capped via. The resulting plated through hole is then covered by the component pad and solder mask, so that no solder or impurities can enter the via. This process is known as “via tenting” and it is necessary to make sure that the via hole is not exposed during assembly.
Is it Necessary to Fill Vias in Pads?
Conductive via filling improves the signal transmission capabilities of the via, but it also increases the overall board cost. This is due to the fact that the process of filling the via requires an extra plating step. In addition, it is not recommended to use conductive via filling in HDI PCBs with fine pitch parts, as this can cause solder bridging issues and reduce reliability.
In order to avoid these issues, you can opt for a capped via instead of a filled one. Capped vias are still plated with copper, but they do not transfer heat or electrical signals. Instead, they offer structural support for the pad and help it to dissipate heat. In contrast, a filled via is hollow and is used to pass signals and heat from one layer to the other.
Despite their disadvantages, a capped via is often the best solution for a high-density PCB. It helps to maximize the routing capacity of the board, eliminating the need for dog bone tracks and allowing designers to place vias directly on the component pads. This can result in much shorter signal paths and can significantly reduce the overall size of the board. In addition, it can also lower the overall cost of a PCB. So, if you are considering using via in pad technology, be sure to weigh up the pros and cons of this option with your contract PCB manufacturer.
