High voltage caps, two caps from Kemet with same volt rating have much diff lead sp

[kaquino215]

Two caps, one from Kemet, the other from AVX, one in a surface mount 1812 package, the other in a surface mount 1210 package have same voltage and almost equivalent dielectric strength specification yet the spacing between the pads is much different.

Is it ok to use the 1210 capacitor (with the smaller spacing) on a board if I expect there to be a voltage of 1000 VDC between the terminals?

What is the clearance requirement for spacing versus DC voltage for traces and pads (top layer of the board) on an FR4 PCB Here's the info on the two caps:

Cap 1.
Mfg = Kemet
Mfg's P/N =C1210C123KFRACTU
Voltage rating = 1500 volts
Diel Strength = 1800 volts
Terminal spacing = 2.2 mm

Cap 2.
Mfg = AVX
Mfg's P/N = 1812SC103KAT
Voltage rating = 1500 volts
Terminal spacing = 4.0 mm

 

[Harvey]

I don't recommend trying to use the smaller part. You're looking at three critical issues:

1. The vaules of the two caps are different. The AVX 1812SC103KAT is rated at 10,000 pF (0.01 µF) while the Kemet C1210C123KFRACTU is rated at 0.012 µF (12,000 pF). That's a 20% difference. Unless you know the design considerations for why the part value was selected, it's best to stick with the value originally specified.

2. The solder terminals for an 1810 (18 mm x 12 mm) package are larger and spaced further apart than those for an 1208 (12 mm x 8 mm) package so you will not be able to position the smaller package to make full contact with solder pads on the circuit board.

2. Typically, a larger package is rated to dissipate more power than a smaller one. This may not be a factor unless the 1810 part was selected by the designers to be able to handle more power than the 1208 part.

While you're at it, make sure the part you buy matches the original part for temperature coefficient. That is the variation in the actual absolute value of the part over temperature. For example, a capacitor rated as Z5U can range from -80% to +20% of its nominal value over a wide temperature range while one rated as X7R may vary +/- 5% and one rated as NPO will have an extremely low variance. The tempco for both the AVX 1812SC103KAT and the Kemet C1210C123KFRACTU is X7R.

I searched for sources for other manufacturers of the same part, and I was unable to find one. The exact replacement part is available from DigiKey Electronics and Mouser Electronics.

Your question suggests you are not familiar with soldering and unsoldering surface mounted components. If the part you are trying to repair is critical to you, don't try doing it by yourself as a learning experience.