EMC Question of the Week: July 18, 2022

Illustration of 1,2,3 and 4 vias per pad connecting a decoupling capacitor to internal planes

In most situations, the number of vias that should be used to connect each pad of an 0402 ceramic decoupling capacitor to the power planes is 

  1. 1
  2. 2
  3. 3
  4. 4


The best answer is “a.” While it is important to minimize the connection inductance of high-frequency decoupling capacitors, there is very little benefit to using more than one via per pad in an 0402 or 0603 package size. It's much more important to ensure that the vias are near each other and in or adjacent-to the mounting pads.

For small capacitors, employing multiple vias per pad takes up valuable space without providing any significant benefit. For large capacitor packages, multiple vias per pad can reduce the connection inductance measurably, but usually larger capacitors are employed when the inductance is less critical. 

It's not hard to find magazine publications and application notes that advocate using multiple vias per pad. However, for reasonable via lengths, peer-reviewed publications have consistently demonstrated that the overall connection inductance is not significantly improved by using multiple vias per pad. 

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