Prevent Buckling in Via Filling
When manufacturing a printed circuit board (PCB), the via hole is copper-plated to create an electrical connection between two or more layers. While via holes are essential for conducting heat and signals between the components, they must be sealed properly to prevent contaminants from entering and potentially causing failures during assembly. In order to avoid trapped air and liquids, the via hole is filled with a conductive or non-conductive material, also known as via covering or filling. There are different methods of via covering and filling, including via plugging, via tenting and via filling.
Conductive via filling involves placing a copper cylinder in the via hole before plating it. This method is often preferred due to its reliability as well as its cost effectiveness and speed. However, if the plated copper in the via hole is too thick, it may cause thermal and current issues and can even lead to premature board failure.
To prevent this, the conductive material in the via hole is reduced by adding non-conductive materials like epoxy or ceramic. The process of avoiding contaminants during PCB production is called non-conductive via filling or non-conductive via treatment. While preventing contaminants is the primary goal of non-conductive via treatment, it’s not always successful due to the presence of microparticles and other pollutants in the PCB manufacturing environment. These microparticles can end up in the via barrel and contaminate the solder pads or traces.
How to Prevent Buckling in Via Filling
Non-conductive via treatment works by filling the via hole with non-conductive material, reducing its size and then metallizing it and plating it over. This method is used to prevent contamination, improve the quality of solder joints and reduce the risk of voids in the via hole. While this technique is less expensive than the alternatives, it can still be a costly issue if the plating process is not carefully controlled.
A common cause of voids in the via barrel is an imbalance of leveling agents or poor solution agitation. By ensuring that the leveling agent is evenly distributed and that the plating solution is agitated regularly, voids can be avoided.
Another cause of voids is the improper use of copper in the vias. If the copper is too thick, it will cause a bridging problem, and this will prevent the pad from bonding to the copper in the via. In addition, the excess copper can increase the weight of the PCB and cause other issues.
The proper techniques for copper plating are critical to avoiding these problems. To do this, the manufacturers must pay attention to the thickness of the copper in the vias and avoid using too much copper. This can cause the PCB to be prone to warping and bending, and it may not meet the design specifications. For this reason, it’s important for the PCB designers to prioritize performance, manufacturability and cost when designing the circuit boards. The engineers at Rush PCB are experienced in the field and know how to do this.
Via filling and rigid printed circuit boards (PCBs) serve distinct functions in electronic design and manufacturing, each with its own set of characteristics and applications. Understanding the differences between them is crucial for engineers and designers aiming to optimize their circuit layouts for specific requirements.