[sdiy] Tantalum manufacturing / assembly failures OT?

Richie Burnett rburnett at richieburnett.co.uk
Wed Nov 14 18:46:50 CET 2018


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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