The purpose of this article is to introduce some basic concepts of reliability engineering as part of development and qualification of semiconductor or electronic packages.
What is Reliability
The reliability of a semiconductor or an electronic device is defined as its ability to perform a required function, under stated operating conditions, for a stated period of time. Reliability concerns itself with device performance and longevity after it has been placed successfully in service. Mathematically, reliability is the conditional probability at a given confidence level that a device will remain functioning within specification, after certain usage time, under specified conditions.
Quality vs. Reliability
Quality is a measure of the device performing its specified function when it is first used. It is a time zero measure (T=0). On the other hand, Reliability is the probability that a device will continue to perform its specified function over time. It deals with time after installation (T gt;0).
Thus, reliability is a measure of the quality remaining after some time of exposure to operating stresses.
Reliability engineers are responsible for the qualification of new product designs, new process technologies, new package materials, and manufacturing changes (process and package) for semiconductor devices. They perform a range of accelerated life and environmental stress tests, then use statistical methods to extrapolate the life expectancy of semiconductor devices under normal use conditions.
A qualification plan is a document that lists the stress tests required for a specific product, process, or package qualification. It describes the conditions, duration, and the acceptance criteria for each stress test.
In my next article, I will be discussing the methods involved in performing reliability stress tests. Make sure to watch for it.