How Does PCB Via Filling Affect the Reliability of the Circuit Board?

PCB Via Filling Affect the Reliability of the Circuit Board

PCB via filling is a process that involves placing either conductive or non-conductive material in the empty holes (vias) in a circuit board. This is an important step that increases the reliability of the board. Vias can connect layers of the board or provide pathways for electrical signals to flow.

A conductive via fill is more effective than an unfilled one at conducting electricity. It is typically made of copper or silver and fuses to the surface of the PCB to create a solid connection between layers. Conductive via fills also offer better thermal transfer capabilities as the metal wicks heat away from hot components to the other side of the board where it can be dissipated by a heat sink. However, they do not work well for high-speed or high-frequency signal transmission as the metal can impede current flow and cause impedance changes.

There are many different methods used to fill the plated-through holes in a PCB. Some are etch-based while others use laser beams to melt and fuse the conductive material into the hole. Each method has its own advantages and disadvantages in terms of cost, complexity, fill quality, and compatibility with the overall manufacturing workflow.

Before the pcb via filling can take place, the board needs to be cleaned and prepped. Once this is done, the etch-based or laser-assisted via filling can take place. Once the conductive or non-conductive material is in the via hole, it must be cured to ensure that it will remain strong and functional when soldering components on the board.

How Does PCB Via Filling Affect the Reliability of the Circuit Board?

The most common choice for a conductive via fill is copper, although some designers choose to use silver if it offers the desired performance. For non-conductive via fill, manufacturers typically choose a non-reactive epoxy such as Peters PP2795 or San-Ei Kagaku PHP-900. These types of epoxies have CTE values that match those of the laminate material they are being used with, ensuring that the structure will expand and contract cooperatively with the surrounding materials to avoid stress fractures caused by unequal expansion and contraction.

Another popular option is to close unused vias during the PCB design stage. This is an easy way to lower manufacturing costs while ensuring that no gaps or holes are left unfilled during production. However, this method must be carefully considered to make sure that the vias being closed are not necessary for the design and there is no alternative routing solution available.

In addition to the cost savings, this method can also improve the overall reliability of the board by reducing the risk of air or liquids becoming trapped in the vias. This is especially important if the vias are located near pads that need to be connected with molten solder in order to function properly. An open via can capture contamination from the molten solder and slow down or even break the connection between the pad and the component. Moreover, open vias can also be susceptible to solder thieving.