PCB Fabrication with Via-In-Pad Technology
There are 2 different methods we utilize to connect our PCB layers: traditional vias and VIP. For traditional vias the solder mask has been a viable plugging medium that prevents solder draw into the barrel of the via. Solder mask can only be used for traditional vias. For Printed Circuit Boards (PCB) that requires a higher layer density, we use the VIP (Via-In-Pad) method.
The Via-In-Pad PCB Design method refers to a pad with a plated hole that connects copper tracks from one layer of the board to the other layers. The Via-In-Pad PCB technique allows the PCB designer to put the via beneath the component pad. When using VIP you have to decide which fill material best suits your PCB project, based on overall particle size and finished CTE (coefficient of thermal expansion). Conductive fill material is a silver coated copper particle filled epoxy matrix, which provides some electrical and thermal conductivity in a cured state. Non-conductive fill materials have CTE and TG values that more closely match the original PCB material. Non-conductive inks are less expensive, easy to metallize, reliable, and more efficient for small holes.
Although the initial price is more expensive compared to using blind or buried traditional vias the benefits outweigh the cost. Via-In-Pad is more expensive because of the higher quality epoxies, metal based vias, and copper cap plating that is involved in this method. The key advantages associated with using Via-In-Pad technology are: higher component density, more board space, better thermal management, lower inductance, and much improved routing.