We are seeing around 1 in 100 Tantalum caps fail shorted when initially pow ered up on the test fixture. There was a discussion here about such failur es being an initial short from fabrication or created when reflowed on the board. An article was linked which discussed a real world app where they p owered up the board with a voltage ramp and enough series resistance to pre vent the cap from creating a hard short and failing. But no information on how slow is "slow" and how much resistance is needed to prevent damage whi le clearing the short.
On the test fixture we can add a resistance to be bypassed with a jumper. We can't control the ramp up time of that voltage rail other than adding mo re capacitance to slow it down. I suppose that is an option if we know a t arget ramp rate. I've asked the manufacturer of the regulator (CUI V7812-1
000) what the ramp rate is and how it varies with capacitance. We'll see i f they respond.Any suggestions on improving this problem? It's not a big deal, but we did have one cap that failed catastrophically and actually burned the board, b ut not beyond repair.
Rick C.
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