Innovative Use of Vias for Density Improvements


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Introduction

In today’s fast-paced global, economic environment—which requires constant innovation, upskilling, and performance improvements— there is a need for increasing density. The classic way to increase density is to reduce the trace and spacing. But in many high-speed board applications, the copper and dielectric losses from smaller traces, or the increased crosstalk from reduced spacings, does not permit this. Four old ideas used in board design and fabrication can offer some insight into how routing density can be increased. These four ideas are:

  • Landless vias
  • Swing vias for BGA breakout
  • Solid paste vias for via-under-pads
  • Power mesh for increased layer density

Getting Over the Density Wall

When it comes to getting higher routing density, you only have five degrees of freedom:

  • Smaller traces
  • Traces closer together (spaces)
  • Smaller vias (down to microvias)
  • Smaller annular ring for the vias
  • Higher layout efficiency when routing    (definition in column #10-DFM/A, June 29-2016 Newsletter)

I’m talking about routing density on a single layer; more signal layers will result in more total routing distance on a board.  

 

Editor's Note: To read this entire article, which appeared in the November 2016 issue of The PCB Magazine, click here.

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