A shift in the capacitance-voltage ratio to service the growing number of portable applications has been one of the key trends in the capacitor market as a result of the automotive and portable segments generating the greatest volumes.
Other trends are a growing number of automotive parts supporting the reliability and temperature requirements of this market, and a push to reduce ESR (equivalent series resistance) to improve high frequency performance.
As the market is generally moving to lower operating voltages, manufacturers are offering higher capacitance devices at lower voltage ratings. This allows the implementation of higher value devices in smaller case sizes, yet maintains the critical electrical requirements of the component.
In many cases component rationalisation is another viable option. By trading off the requirement for higher operating voltages it is often possible to replace two or more capacitors with just one higher capacitance, lower voltage component.
Polymer tantalum
To address the needs of the automotive market, tantalum manufacturers are developing smaller, higher capacity devices with higher temperature rating and lower ESR. In order to achieve higher reliability and lower FIT (failure in time) the latest development is to replace the manganese dioxide layer with a polymer layer.
This development can also improve high frequency performance, helping tantalum manufacturers access the growing high frequency market. The inclusion of polymers can reduce the ESR to around a third of that of a standard item, reducing ESR from around 900mOhm to around 300mOhm.
New multi-anode devices use up to three anodes in parallel to further reduce ESR down to 100mOhm or so. Multianode polymer devices are only available up to 10V at the moment but it is expected that higher voltages will be available over time, similar to those offered for manganese dioxide parts.
Incorporating protection
Component rationalisation is another area being looked at by manufacturers.
A promising development is the high reliability, MLSC (multilayer serial capacitors) technology that incorporates integrated short circuit protection. Designed primarily for applications where the capacitor is hanging off the power line, the device is made up of two MLCC in series encapsulated within a standard multilayer chip package. These can eliminate further protection devices in certain applications.
Safety capacitors
X2 safety capacitors are now being rated at 305Vac (a jump from the old standard of 275V), primarily because more and more engineers are developing their own EMC filtering circuitry on board rather than specifying off the shelf systems. Despite this improvement in electrical specifications and higher capacitances – up to 10µF – the size and corresponding footprint trends are smaller than before and the prices are not adversely affected.
With reliability in mind another significant development is that of ‘soft termination’ products. These use a different type of termination material that is more flexible and is therefore less susceptible to mechanical stress.
These are just highlights among a host of new capacitor technologies. More and more component manufacturers are tending to specialise on a limited range of generics. It is therefore important that any new designs are supported by a component supplier that understands which manufacturers are the key players within each field.
Mike Fitzpatrick is marketing manager for passives at Abacus Polar
