Materials Are Used in Via Fill
Via fill is the process of filling the via holes in a PCB with conductive or non-conductive material. The purpose of via fill is to improve the performance and reliability of the board. Vias are copper-plated holes that allow electric connections between different layers of the PCB. There are several types of vias including through-hole, microvia, blind and buried. The via hole walls are plated with a conductive metal (copper) or filled with a conductive or non-conductive epoxy resin. Vias are used in many different ways in a circuit board such as connecting components, signal routing and power distribution.
The most common via fills are non-conductive. Conductive via fills are more expensive and can increase the overall cost of a circuit board. However, they provide more benefits such as improving thermal management and current capacity. For example, a conductive fill can help deviate the heat from large components such as ICs or BGAs, reducing solder wicking and silkscreen printing issues and enhancing current capacity and electrical conductivity.
There are a few factors that affect the choice of via fill material, such as its cost, CTE match and process compatibility. The type of via filling material should also be compatible with the plating technique used in the production of the circuit board. In addition, the PCB designer should consider how the metallization of the vias will be affected by the choice of fill material.
What Materials Are Used in Via Fill?
For example, the use of a conductive via fill can cause problems if the circuit board is subject to a high level of vibration. This is because the copper in the conductive via fill may move against the copper in the circuit board, causing the formation of stress fractures. To avoid this, the metallization should be designed to prevent movement of the copper in the via.
Another factor to consider is the CTE match between the via fill material and the surrounding laminate. This is important because the materials will experience a significant amount of expansion and contraction as the board undergoes heating and cooling. A better CTE match will reduce the chances of stress fractures and other failure modes.
The most popular via fills are copper and silver conductive epoxy. These materials are more affordable than gold, but don’t compromise on quality or performance. Conductive via fills are highly recommended for critical traces, as well as high-speed or high-current nets. They also offer better thermal conductivity and are more resistant to corrosion. Some manufacturers choose to use the DuPont CB100 or Tatsuto AE3030 via plugging pastes, which are both made with copper flecks embedded in a silver epoxy resin. These are both good options for manufacturers looking for a balance between performance and affordability. However, we recommend using copper, as it offers higher performance and is cheaper.
