[sdiy] Tantalum manufacturing / assembly failures OT?

Ullrich Peter Peter.Ullrich at kapsch.net
Wed Nov 14 22:16:26 CET 2018


Hi Ritchie!

We had some failures with Tantalum capacitors but not that much.

The Austrian Kemet Sales Manager once gave us a presentation about derating you should take care of.
I found this presentation online - you can have a look at it here at Digikey:
https://www.digikey.com/en/ptm/k/kemet/derating-guidelines-for-surface-mount-tantalum-capacitors/tutorial

Ciao
Peter

________________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Richie Burnett <rburnett at richieburnett.co.uk>
Sent: Wednesday, November 14, 2018 18:46
To: SDIY List
Subject: [sdiy] Tantalum manufacturing / assembly failures OT?

Since we're discussing Tantalum capacitors, has anyone else who manufactures
things in reasonable quantities, (either hobby, SDIY or in their day job,)
had problems with SMD Tantalum capacitors failing short or partially shorted
due to excessing heat during reflow?

I've had a bunch of boards made by a well known UK PCB fab and population
company, and several off them had 100uF/25V Panasonic SMD Tantalums fail
short-circuit within about 10 seconds of powering up the board.

Just to rule out a design issue, the two capacitors that were failing only
saw 15VDC from a well regulated power supply, and charge slowly through a
resistor so there is no significant inrush current or AC ripple current
either.  And they weren't installed with incorrect polarity!  The two
devices that failed on each board are right next to a D2PAK SMD power device
that is clearly discoloured from excessive temperature during assembly, so I
can only suspect that the use of a hot-air pencil during assembly is the
culprit!

I haven't used SMD tants that extensively in electronics, so would be
interested to hear others experiences, either on list or via PM.

-Richie,

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