Probability Density Function of a system failure.

Hi everyone,
Stat is not my strong area. Your help is much appreciated.
I am trying to get probability density function (PDF) of a system failure. First of all I have very limited information, and I am not sure what information I need to get PDF.
The system fails at 155 degree temperature, and at 40 degree temperature probability of failure is 1%. What would be the failure probability at temperature 75 degree. The temperature value ranges form 20 degree - 155 degree.
Is this enough to find PDF, or what other information I need.

Thank you