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Most manufacturers produces crimped and straight lead pairs of their capacitors which has exactly same capacitance and voltage rating. Why do they bother crimping the leads? What advantage does it make? In which cases a crimped lead capacitor should be preferred?

enter image description here

hkBattousai
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    I'd suspect that it's easier to hand-solder them, as they will hold in place after cutting the leads. – Simon Richter Oct 22 '14 at 06:26
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    Serves two purposes: 1) Space the cap up a bit when inserted into a PC board. 2) Provide some flex so that the cap is not overstressed while being inserted into the board and soldered. – Hot Licks Oct 22 '14 at 21:09
  • It wall also assist with draining of the flux wash and accommodate the slight size variations of thee parts when automatically held by the insertion machine and pressed in. – KalleMP Nov 13 '14 at 09:39

3 Answers3

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It's to space the capacitor up off the board so that undue stress is not placed on the ends of the capacitor (for example, if the lead spacing in the board holes is not exactly the same as the lead spacing on that particular capacitor, or if the thermal coefficient of expansion is different from that of the PCB).

As well as your pictured film capacitors, you'll find similar kinks in ceramic disc capacitor, thermistors, MOVs and similar parts.

Here you can see it clearly called a "hold off" kink on a disc capacitor.

enter image description here

Some other parts- NTC (Negative Temperature Coefficient) thermistors:

http://www.homepin.com/pics/5pack.jpg

The capacitors you pictured are epoxy dipped, but the early laquer dipped ones were even more susceptible to damage from too much force on the leads. This should bring back some bad memories for oldsters here:

http://www.retrosynth.com/~analoguediehard/studio/keyboards/oberheim_obsx/broken-capacitors.jpg

Spehro Pefhany
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Ceramic capacitors are rather brittle and so they do not like their leads getting tugged on. Adding these crimps forces the capacitor to sit off the board with a few mm of relatively flexible lead in between. This will isolate the capacitor from forces that it would otherwise experience during vibration, board flexing/bending, thermal expansion/contraction, etc. By providing the crimped leads at the factory, the board house does not require a machine to add those in-house.

alex.forencich
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  • What does exactly happen if their leads are tugged on? – hkBattousai Oct 22 '14 at 06:40
  • Ceramic is brittle and will crack if subjected to too much force. Electrolytic capacitors, for example, can tolerate a bit of movement on the leads because they are held in a flexible rubber plug. A cracked ceramic capacitor will not work as intended - it can fail short or open, or simply come far enough out of tolerance to affect operation. – alex.forencich Oct 22 '14 at 07:01
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    To be specific, a straight down tug is not so bad. The problems happen if the pcb hole spacing is slightly different from the lead spacing which causes them to be tugged outward. It also lines them up nicely for inspection. – Jeff Bell Oct 22 '14 at 17:50
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As the capacitors pictured are film capacitors, using the crimp to stand them off the board will help to keep their temperature below the melting point of the film during soldering.