Capacitor plague-Symptoms-Common characteristics-PCB

- Feb 10, 2017-

Capacitor plague-Symptoms-Common

characteristics-PCB

Symptoms

Common characteristics

The non-solid aluminum electrolytic capacitors with improperly formulated electrolyte mostly belonged to the so-called "low ESR", "low impedance", or "high ripple current" e-cap series. The advantage of e-caps using an electrolyte composed of 70% water or more is, in particular, a low ESR, which allows a higher ripple current, as well as the use of water making them less expensive to produce, water being the least costly material in a capacitor.

Comparison of aluminum e-caps with different non-solid electrolytes
ElectrolyteManufacturer
Series, Type
Dimensions
D x L
(mm)
Max. ESR
at 100 kHz, 20 °C
(mΩ)
Max. Ripple current
at 85/105 °C
(mA)
Non-solid
organic electrolyte
Vishay
036 RSP, 100µF/10V
5x111000160
Non-solid, Ethylene glycol,
boric acid (borax) electrolyte
NCC
SMQ, 100µF/10V
5x11900180
Non-solid
water-based electrolyte
Rubycon
ZL, 100µF/10V
5x11300250

Premature failure

All electrolytic capacitors with non-solid electrolyte age over time, due to evaporation of the electrolyte. The capacitance usually decreases and the equivalent series resistance (ESR) usually increases. The normal lifespan of a non-solid electrolytic capacitor of consumer quality, typically rated at 2000 h/85 °C and operating at 40 °C, is roughly 6 years. It can be more than 10 years for a 1000 h/105 °C capacitor operating at 40 °C. Electrolytic capacitors that operate at a lower temperature can have a considerably longer lifespan.

The capacitance should normally degrade to as low as 70% of the rated value, and the ESR increase to twice the rated value, over the normal life span of the component, before it should be considered as a "degradation failure". The life of an electrolytic capacitor with defective electrolyte can be as little as two years. The capacitor may fail prematurely after reaching approximately 30% to 50% of its expected lifetime.


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