standards or guidelines related to filled vias
mong the many things that a PCB designer needs to know is which via protection type they should use. Some PCBs have copper filled vias, others are plugged, and still others have both. Using the proper via protection is critical for your PCBs, because the wrong choice could lead to performance issues in the long run.
Conductive fill vias help to transmit current more efficiently from one side of the board to the other, while plugged vias provide better thermal transfer between layers. To achieve this, the via holes are filled with a conductive epoxy. The specific product used depends on the application; copper conductive epoxy has superior thermal transfer properties, while silver conductive epoxy is more cost-effective.
Via holes are usually created by either mechanical drilling (for traditional vias) or laser drilling (used for microvias). The drilled hole is then filled with a metal, such as gold or copper, to form a via. The via is plated to ensure the proper electrical connections between the different layers of the circuit board.
A conductive via fill is more expensive than a non-conductive one, but it offers superior performance and a longer life for the components on the PCB. They also improve a PCB’s density and enable higher routing speeds. Another benefit of the new copper plating process is that it creates a much smoother pad surface for soldering components into. This makes it easier for assemblers to process the pads and components through a pick-and-place machine.
Are there any standards or guidelines related to filled vias?
There are two ways to plate a via: the batch process and the inline process. The batch process involves placing the PCBs in an electrolyte tank for a time-consuming plating process, while the inline process is more efficient and costs less.
Another common method for via protection is the use of a solder mask, such as IPC-A-610 class 2 or IPC-A-610 class 3. This technique uses photo-imageable solder mask that’s exposed to ultraviolet light in order to selectively cure the areas of the PCB that need to be filled with via paste. This allows the vias to be filled with a conductive or non-conductive material, and provides a high degree of certainty that they will be filled.
However, if you’re planning on using a metal-filled via, it’s important to consider the CTE (coefficient of thermal expansion) differences between the copper and the laminate. When the vias are filled with metal, they’re going to expand and contract at a different rate than the laminate, and this can cause stress fractures between the pad and the hole wall. This is why it’s important to specify the correct IPC-4761 type for your vias.
If you’re not sure which via protection type to choose, we recommend consulting your PCB manufacturer to ensure they understand the details of your design and what’s important for your project’s success. This way, they can make recommendations for you that are best suited to your requirements and budget.