Via Filling Be Used in Space Applications
Via filling is the process of filling plated-through holes (vias) on printed circuit boards with either conductive or non-conductive material. It improves a PCB’s performance, reliability, and structural integrity by reducing the possibility of air or liquid getting trapped in the via hole, and enables effective heat dissipation from the internal components to the outside world. This is an essential step in high-density interconnect (HDI) manufacturing, which requires the use of smaller and more compact board components to accommodate increased connectivity demands.
Conductive via filling is typically done with copper, which provides excellent thermal management properties by efficiently dissipating heat to the surrounding surface of the PCB. However, the process of forming a conductive path through the copper layer within the via requires multiple steps, including activation, electroless copper deposition, and time-consuming plating processes. These steps are also expensive, causing the overall cost of a PCB to increase.
Using a non-conductive via fill method, on the other hand, avoids these issues by replacing the copper with an epoxy resin, which offers much better thermal insulation properties than copper. This also helps prevent solder wicking and silkscreen printing issues. In addition, the insulating resin can also help prevent electromagnetic interference (EMI) and other electrical problems caused by high-frequency signals.
Can Via Filling Be Used in Space Applications?
Both types of via filling methods require special attention to detail during the PCB fabrication process, as overfilling with either a conductive or non-conductive fill can result in the creation of voids. Voids can cause solder to wick into the plated-through holes, thereby negatively impacting the reliability of the circuit board. They can also lead to short circuits and electrical failures.
For the best results, it is critical to work closely with your PCB manufacturer to optimize every aspect of the via filling process. This includes selecting the right via fill materials, following proper dispensing and curing techniques, and ensuring that the aspect ratio of the via hole is not too large or too small for DFM acceptability.
Conductive via fills are generally characterized by their copper content, and two common options include DuPont CB100 and Tatsuto AE3030. Both of these conductive via fills contain copper particles suspended in an epoxy binder, but AE3030 is usually chosen when cost is more of a consideration than conductivity. Decide whether to use conductive or non-conductive via filling material based on electrical requirements and manufacturing constraints. Conductive fill materials like solder or conductive epoxy enhance electrical performance, while non-conductive materials like epoxy resin improve reliability.
The most important factor in the success of a conductive via is the ability to maintain a consistent copper thickness throughout the entire hole barrel. The lack of uniformity in the thickness can lead to a stress fracture between the pad and hole wall when the copper is subjected to unfavorable environmental conditions, such as elevated temperatures. This can eventually lead to the failure of the device, if not addressed promptly. To avoid this problem, it is important to follow the correct dispensing and curing procedures when assembling your PCB, as well as maintaining an appropriate level of agitation for the copper plating solution.