Tantalum cap voltage?

[Mr RB]

I have a SMD tantalum cap on a PCB and trying to determine it's voltage.

It is size A I believe, about 2.4x3.0mm yellow body.

Markings;
^106V
8C7K1

I believe the 106 is 10uF because that makes sense re the place it is in circuit, and I have a feeling the V is a code for lead or leadfree.

The K probably indicates 10% tolerance.

The cap looks to be too small for a 10uF 35v cap (which would would be a V marking as a voltage code). Based on its small size I would guess a 6v 10v cap, maybe 16v.

Would anybody be able to offer some thoughts on the cap voltage rating? Thanks!

 

[crutschow]

The best guess is likely to do as you did. Look up other 10μF tantalum caps of that size and see what voltage ratings they have. If you are looking to replace it, select the highest voltage available in that size and capacity.

 

[Mike odom]

If a tantalum is used to decouple, the voltage rating needs to be at least 3 times the max voltage it will see. Otherwise, it will tend to BLOW UP... tantalum caps are not intended to be used as decoupling caps, according to their manufacturers...

 

[simonbramble]

Try looking on the AVX website. You can download a datasheet with sizes and working voltages. I've never heard that they are not meant to be used for decoupling... They used to blow up, but I hear they are much better now...

 

[Mike odom]

Try looking on the AVX website. You can download a datasheet with sizes and working voltages. I've never heard that they are not meant to be used for decoupling... They used to blow up, but I hear they are much better now...

I just went through a year troubleshooting Flight Data Recorder Boards with the tantalum problems. It didn't matter which manufacturer's part we used. We had 5 50V diodes on a 28V bus that would blow up. On a 1000 board run, we'd replace 250-260 parts, sometimes the same location twice. Since it was a 28V bus, we'd use a thermal camera to find the offending part since one bad part would drag the whole bus down. After a while, we decided to just hit the bus with a 4 amp supply and look for the smoke, shutting it down before the board was damaged. Sometimes you could find them by the 'volcano top' effect or black soot on the board where they vented, but not very often. Since these defects were found prior to burn in, engineering thought it was no big deal. When recorders started coming back from airplanes with the tops blown off some of the caps, they decided to get off their duffs and do something about it. The soln, squeeze a 63V part in, and eventually redesign the board to use an even higher voltage part. I would say it was our number one manufacturing defect.

We were having this issue up to the time I left in April of this year, so I'd say they aren't much better now. The problem is the rate at which current is applied... the decoup's seeing a faster inrush current, and rapid spot heating of any O2 inside the tantalum mix.

 

[Doktor Jones]

(deleted)

 

[Mr RB]

The best guess is likely to do as you did. Look up other 10μF tantalum caps of that size and see what voltage ratings they have. If you are looking to replace it, select the highest voltage available in that size and capacity.

Thanks Crutschow, it's in a commercial product that is getting power line glitches on a 25v DC rail, I thought it might be because a cap had been inserted at the wrong voltage.

I unsoldered the cap in question and it tested at 8.97uF (10uF) and seemed to charge and discharge fine repeatedly at 35v DC (into a short too) so I guess it really is a 35v rated cap.

Anyway now that cap is scrapped and a brand new 10uF 35v cap installed, and there are still glitches on the PSU rail so that's that.

Thanks too SimonBramble, I checked the AVX markings but they don't seem to match that cap either.