[sdiy] Tantalum manufacturing / assembly failures OT?

Roman Sowa modular at go2.pl
Thu Nov 15 12:28:57 CET 2018


Wow, there are 47uF 0805 caps in that photo!
They must be utterly crap at that size.
Pure marketing obviously.
I never reach for more than 10uF in 0805 and that's when I really need 4uF.

Roman

W dniu 2018-11-15 o 08:16, Ullrich Peter pisze:
> 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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