[sdiy] Odp: Tantalum manufacturing / assembly failures OT?

Ullrich Peter Peter.Ullrich at kapsch.net
Thu Nov 15 08:16:48 CET 2018


Hi!

Yes, the current price situation is crazy.
By switching between capacitor families always keep in mind their special behavior.
Würth Electronics has a special reminder tool for MLCC effects (here: voltage bias influence on capacity)
they show on the Electronica fair in Germany at the moment – someone posted it today on Instagram.

See photo
http://tinypic.com/r/95q2i1/9

Ciao
Peter

Von: Synth-diy <synth-diy-bounces at synth-diy.org> Im Auftrag von Roman
Gesendet: Donnerstag, 15. November 2018 07:16
An: Richie Burnett <rburnett at richieburnett.co.uk>; synth-diy at synth-diy.org
Betreff: [sdiy] Odp: Tantalum manufacturing / assembly failures OT?

I've only used couple of thousands SMD tantalums ever, so this may not be so reasonable quantity to say anything, but I remember only once it failed from unknown reason, at first power up.
There were aslo few other incidents in products working for some time, but it was always because connecting power in reverse.
I switched to ceramics as replacement some time ago, but with current price/shortage situation I may welcome tantalums back soon.

Roman


Dnia 14 listopada 2018 18:51 Richie Burnett <rburnett at richieburnett.co.uk<mailto:rburnett at richieburnett.co.uk>> napisał(a):
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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