How can I find failure rates and probabilities when there is no information available?
Your best choice is to ask the manufacturer, and ask them to give you a document, not just a mail.

If for some reason the manufacturer can't give you any information, you have to guesstimate how reliable a part is.

There are several standards which can be used to estimate a MTBF for a part.


Mil-HDBK-217
Telcordia SR-332
IEC-TR-62380 
Siemens SN 29500
FIDES 2009
217Plus
GJB/Z 299C


I can't really comment on how useful each and everyone of them is, I think in our safety assessments we use different standards.

Siemens and IEC are the ones I already stumbled upon. But in some cases things tend to get very odd. Like failure rates for RAM, where you can get values from almost 0 to so large it dominates the whole system and with a RAM-test you just removed 90 % of the failures and are "done".

On this website I found a few comments on those standards, which suggest that the Mil-HDBK-217 is the most pessimistic guess and if you apply that you'll probably end up on the safe side.

Another source for information is usually the certification authority which is usually involved in the process of getting a SIL certified product for example. But in most cases, they hint you to the same standards, but you get an idea which one they prefer and using that reduces the amount of time spent arguing with them.