In circuit board design, via means a pad with a plated hole which helps to link copper traces from one layer of the PCB to subsequent layers. High-density multi-layer circuit boards might have blind vias that are noticeable only on a single surface or buried vias that cannot be seen on either of the surface and they are generally referred as micro vias. The introduction and widespread use of high density pin out parts and the need for small size circuit boards has created fresh challenges. A better solution to meet this kind of challenges is the use of latest but familiar PCB fabrication technology is “via in pad”.
There are numerous benefits of via in pad PCB. It helps to increase density, lessen inductance and use finer pitch packages. In via in pad process, a via is directly placed below the device’s contact pads. This enables greater part density and superior routing. Therefore, via in pad furnishes the considerable board space savings to the PCB designer.
Filled via in pad enables to accomplish intermediate density with an intermediate price as opposite to blind/buried vias. The benefits of using of via in pad technology are:
fan out leadless packages
closely packed placement
enhanced thermal management, etc.
Via in pad is being speedily used in the current PCB design because of the constantly decreasing pitch of part footprints, in addition to the requirement to miniaturize board form factor. Signal routing can be achieved in as little an area of the PCB layout as possible, in majority of the cases even avoiding escaping the perimeter of the device footprint.
Vias in the pads is mostly helpful in high speed designs because they decrease trace length and consequently inductance. You are required to confirm that your PCB house is well-equipped to do this as it may cost more. If you are not able to place via in the pad, putting directly and using more than one can assist in decreasing inductance.
Via in pad is also useful where the space is inadequate like in micro-BGA designs, and where the conventional fan-out methods cannot be used.
This technology has few drawbacks linked to it. There is a huge cost impact due to the adoption of a new technology. Added manufacturing process complication and the essential material price for the conductive fill are the two main cost elements linked with via in pad technology.
In particular, via in pad technology leads to increase in steps to the PCB manufacturing process. Nevertheless, the decline in number of layers by means of via in pad technology covers the extra charges related to this process.