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Why hybrid aluminum capacitors fail to truly deliver the best of both worlds

Written by Anthony Kenny

February 18, 2019

INTRODUCTION

It is common marketing parlance that aluminum hybrid capacitor technology offers a designer the “best of both worlds”: the high conductivity and low ESR of an aluminum polymer capacitor combined with the high withstand voltage and high capacitance ratings of a traditional wet aluminum capacitor.

However, a closer look at the range of hybrid aluminum capacitors on offer today reveals a significant shortcoming in one of these departments. 

CONSTRUCTION

As its name suggests, a hybrid aluminum capacitor utilizes a composite of organic polymer and liquid as the electrolyte and aluminum as the anode. The polymer offers low ESR performance, and the liquid portion of the electrolyte offers high withstand voltage and high capacitance ratings due to its large effective surface area.

PROS

This hybrid technology does deliver some fundamental advantages over the unmixed types:

  • higher ripple current ratings than straight polymer types
  • low DC leakage and ESR
  • more compact design vis-a-vis straight electrolytic types
  • better endurance and humidity resistance than polymer types or standard electrolytic types

CON

A quick check however will reveal that they fall short in one significant area: available capacitance

The graph to the right compares upper capacitance ratings available from manufacturers of aluminum polymer capacitors against aluminum hybrid capacitors and shows an almost five fold difference in surface mount V-chip versions in polymer’s favour.

If figures were included for aluminum electrolytic capacitor, both sets of figures to the right would be dwarfed.

So, when it comes to aluminum hybrid capacitors, perhaps the marketing parlance should be changed to read “the best of both worlds within narrow capacitance limits

This difference is a surpise to Capacitor Faks as hybrid technology lends itself to high capacitance ratings, but this capability has not yet been realised, falling well short of polymer devices in available capacitance ratings. We welcome any input as to why this might be the case.

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