"The limitations of long-term reliability are important concerns" determined S.M.Sze in his book "Physics in Semiconductor Devices". Sze wrote in his book that "Since most practical problems in the reliability and stability of all semiconductor devices are intimately related to their surface conditions, an understanding of the surface physics…is of great importance to device operations". He also stated "Extensive studies are continuing in this field to understand the material quality, absorption coefficients, and reliability". But what is this reliability?
Reliability is defined as the probability that the element (component, Integrated Component, interconnect, module) will perform it's intended function for a specified period under a given operating conditions without failure.
Technically speaking, reliability is the percent of survivals, that is R(x) = 1-F(x), in which R(x) is the reliability (survival) function and F(x) is the Cumulative Distribution Function (CDF).
The one and only way to determine the element reliability is by reliability testing to determine the F(x) which represents the life distribution, a theoretical population model used to describe the lifetime of an element.
The objective of reliability tests is to obtain failures and to best fit the failure data to determine the parameters of the CDF of a chosen probability distribution.
As soon as the life distribution F(x) of the element is estimated by reliability testing- the Reliability R(x), failure rate, commutative failure rate, average failure rate, mean time to failure etc. Of the element are readily determined.
Most reliability tests are accelerated tests, with increased intensity of exposure to aggressive environmental conditions and realistic sample sizes and test times.
Accelerated models are needed to translate the failure probability, reliability function, failure rate and mean time to failure from a test condition to an operating condition.
In establishing the acceleration models for lead free interconnects, their surrounding materials [solder, molding plastic, ceramic, copper, fiber-reinforced glass-epoxy, silicon], loading[stress, strain, temperature, humidity, current density, voltage] and failure mechanisms and modes [overload, fatigue, corrosion, electromigration] must be considered.
EDE Electronics masters the Reliability field and cooperate with all the companies whose products EDE offers as their back end reliability partner.