Lifespan wet tantalum

[salomonander]

Hey there,
im wondering about the life of wet tantalum caps. I have a tape machine here that uses them exclusively (axial Kemets). There is one electrolytic per board and dozens of wet tantalums. I did measure a bunch of them and they seem fine. The machine is from the 70s though…. Is it safe to leave them in there?
If not, or in case one fails later, what can i replace them with? Considering the price, modern wet tantalums are not an option (unless id only need a handfull).
thanks!

 

[ccaudle]

Wet tantalums are not used much in the commercial equipment I am familiar with, but I have heard lots of horror stories of older equipment with leaky wet caps. The electrolyte is acidic, and will damage the PCB where it leaks.

According to this paper from AVX, there was a change in construction style at some point, and the new hermetic style is much more durable than the older epoxy seal style:
AVX wet tantalum whitepaper

This Vishay whitepaper says there are multiple seal styles:
Vishay wet tantalum whitepaper

I do not know how to tell the difference between the styles, and the '70's would be right around the cross over point (the stories of leaky caps I have heard was mostly from late 60's or early 70's equipment designs).

 

[emrr]

I always thought they sounded cool in the 1RU Thomson Volumax units, never saw a leaky one.