microvias be plated with different materials
The interconnects that enable electronic devices to communicate are drilled holes in the different layers of the printed circuit board (PCB). These are called plated through-holes, or vias, and provide a route for electrical connections between layers. Vias also play a critical role in distributing heat from components and reducing the risk of hot spots that can lead to mechanical failures.
Depending on the material used to drill the hole, and the process used for filling and plating, microvias can have different reliability characteristics. This is because the plated copper that connects the inner-layer circuits to the PCB surface must be of high quality, and consistency. Additionally, the aspect ratio of the via – that is, its relationship between depth and diameter – needs to be carefully considered. Deviation from the ideal or recommended aspect ratio can impact its functionality, and can result in defects such as voids.
When it comes to avoiding via-related ICDs, proper design and fabrication is key. The PCB designer must ensure that the hole is positioned correctly, and that it doesn’t intersect with other layers or traces. Similarly, the PCB fabricator must make sure that the vias are drilled with the correct materials and process. It is important to choose a fabricator that is experienced with using high-density circuit boards and has the tools and knowledge required for precision drilling, including the latest lasers.
Can microvias be plated with different materials
Once the different PCB layers have been fabricated and composited together, all the thru-holes must be drilled. This includes component pin holes, non-plated holes, and vias. These holes are then cleaned of debris from the drilling process, and the PCB manufacturer will use either pure copper or epoxy resin with copper to fill them. Then, they will plate the copper onto the top surface of the PCB. The plating process is critical, because it prevents the formation of dimples, voids, or bumps in the copper layer that could compromise the integrity of the via.
In addition to ensuring that the copper layer is of good quality, manufacturers must also take care not to deviate from the recommended aspect ratio for the microvia. In order to achieve a reliable copper via, the holes should have a ratio of 1:1 between their diameter and depth. Any deviation from this ratio may lead to a defect that is known as a ‘via-related ICD’. This can occur if stress is applied to the via, or if there are variations in the thickness of the copper plating layer.
Another common type of ICD that affects the reliability of microvias is a copper bond failure. This occurs when the copper connection breaks off, typically due to high stresses during assembly and usage or because the copper is weaker than it should be. This type of ICD is not as prevalent as the other two types, but it can still be a major problem for PCBs with high density. There are some newer products available on the market that can improve copper bond strength, but this technology is not yet widely used in PCBs.