Right Material for a Via Fill
When it comes to a PCB, the quality of its through holes is crucial to achieving successful functionality. Through-holes, which are also referred to as vias, connect circuitry layers and enable signals to flow through the board. Vias are drilled into the PCB substrate and then filled with either copper or non-conductive epoxy. The correct choice of through hole material has a direct impact on the integrity and performance of a PCB.
The most common via fill material is conductive silver or copper. Conductive vias have a high level of thermal and electrical conductivity that allows them to transfer current across the substrate, even at higher voltage levels. This makes them ideal for applications that need to withstand high amounts of heat. These include LED, high power and radio frequency PCBs.
Via filling can also reduce the number of voids on the board. A void is a gap in the via that can cause signal failures and other errors in the board. This is especially important for a PCB with high density and small pitch traces, where the space is limited. A void in a via can lead to poor connections and shorting, which is why it is crucial for a PCB manufacturer to follow strict quality guidelines when producing a board. This ensures that the vias are correctly filled with the proper material and that they meet the necessary standards for the specific application.
Choosing the Right Material for a Via Fill
Using copper-filled vias is an excellent way to improve the quality of a PCB. The copper enables signal transfers between the inner layers, making it easier to route and locate components. It also helps to keep the board cool by directing excess heat away from the chips. This reduces the stress that a chip can experience, which increases its lifespan and reduces the risk of failure.
Copper-filled vias are typically plated with copper in order to ensure their conductivity. This is a more expensive option than silver-plated vias, but it has many benefits that make it worth the investment. Its higher conductivity allows it to handle greater current levels, and it is more resistant to corrosion. It is also a good choice for applications that require precision soldering due to its high melting point.
A common misconception is that a non-conductive via fill doesn’t allow any current to pass through the via. This is incorrect, however, as the via is still plated with copper and is able to carry electrical signals. The difference between a non-conductive via fill and traditional vias lies in the fact that they are filled with a non-conductive epoxy paste, which replaces the air in the via hole. This is particularly useful for Via in Pad processing as it helps to prevent solder bridging between the pad and the hole wall.
There are several different types of non-conductive via fills, with Peters PP2795 epoxy and San-Ei Kagaku PHP-900 epoxy being popular choices. It is essential that the CTE of the epoxy used matches that of the laminate in order to avoid stress fractures caused by expansion.
