How to Reduce HDI PCB Cost?
It is known to all that high density interconnect or HDI circuit board design always requires a higher wiring and pad density than custom PCBs, along with smaller trace width and spacing. HDI PCB fabrication is more expensive than custom one for its complicated build-up process and high-technology requirement such as blind vias, buried vias, microvias, etc. But today, EPCB will outline two useful tips aiming to reduce your cost.
Tip 1: Widen a BGA breakout channel with a blind via.
Some of you are used to using through-hole vias, and that cause the trace escape for a BGA fails to run smoothly. How about widening the breakout channels on the bottom and inner layers with blind vias?
Suppose the board on the top had three rows of through-hole vias, letting only four traces out between the 1st and 3rd rows. While we replace them with blind vias in the middle row, you will find six traces is permitted now, which means a 50% increase. This way indirectly reduces your cost for reducing your PCB layer count.
Tip 2: Use blind and buried vias to reduce the PCB aspect ratio.
Often, a PCB will have BGA components with several different pitches. Here the minimum via hole is not only determined by drill size, but also the aspect ratio, which is the thickness of the PCB divided by the diameter size of the drilled hole. And there is usually an additional cost for aspect ratios higher than 10 or 12.
If through-hole vias are required, even after blind/micro/buried vias are used, it may still be a challenge keep the aspect ratio low. To meet the aspect ratio requirements, the PCB thickness would have to be reduced as follows. One is 3.6mm (140mil) for 10mil through-hole vias (drill size of 12mil) with 0.5mm (20mil) pads for the 0.8mm pitch BGA. Another is 3.0mm (120mil) for 8mil through-hole vias (drill size of 10mil) with 0.45mm (18mil) pad for the 0.8mm pitch BGA.
The above two tips are proved to be cost-effective, and you can have a try in your HDI PCB design.