How to Reduce PCB Cost when Designing HDI PCB?

Dated:2017-04-11      Popularity:1388

Budget for HDI PCB is always higher than standard one, so how to save PCB cost really matters. High density interconnect PCBs have a higher wiring and pad density than conventional PCBs, along with smaller trace widths and spaces. They require advanced PCB technologies such as blind vias, buried vias, and microvias. In this article, we will offer a cost-effective solution by making good use of blind vias, buried vias, and microvias.

Solution 1: Reduce layer count by widening the BGA breakout channel with a blind via. If you're using through-hole vias for a design and the trace escape for a ball grid array (BGA) isn't going smoothly, consider widening the breakout channels on the bottom and inner layers with blind vias.

Solution 2: Eliminate electrical layers by replacing through-hole vias with microvias. Microvias have the smallest pad size (as little as 0.008"), which helps maximize routing channel width.

Solution 3: Use blind and buried vias to reduce the PCB aspect ratio. Often, a PCB will have BGA components with several different pitches. For example, there may be a 1.27mm pitch BGA and an 0.8mm pitch BGA on a 4.0mm (160mil)-thick PCB. 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. There is usually an additional manufacturing cost for aspect ratios higher than 10 or 12. 
To meet the aspect ratio requirements, the PCB thickness would have to be reduced as follows: 3.6mm (140mil) for 10mil through-hole vias (drill size of 12mil) with 0.5mm (20mil) pads for the 0.8mm pitch BGA; 3.0mm (120mil) for 8mil through-hole vias (drill size of 10mil) with 0.45mm (18mil) pad for the 0.8mm pitch BGA. If you reduce the layer count by replacing through-hole vias with blind vias and microvias, you can achieve a smaller aspect ratio for your PCB, and avoid any cost penalties due to using blind/microvias.

Hope it is useful of you.


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