Essentials of Electronic Packaging: A Multidisciplinary Approach
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Reliability enhancements are considered when a product, which is designed for a specific application, does not meet the life expectations as evidenced by accelerated test results. In such instances, reliability enhancements are implemented. The choice of materials and processes need to be carefully evaluated for optimum performance. As has been discussed in an earlier chapter, the word “reliability” encompasses performance under a variety of stresses and loads. These include
(a) Expansion and contraction
(b) Thermal management/heat dissipation
(c) Vibration, etc.
(a) Humidity (condensing and non-condensing)
(b) Corrosive gases
(c) Particulate dust, etc.
4. Radiation, etc.
(b) Cosmic (α, β, γ radiation)
An enhancement measure aimed at one reliability exposure may not provide the same level of improvement against a different reliability, and vice versa. The possibility that it may even degrade one at the expense of the other cannot be ignored. Thus, it is important to choose an appropriate design, the right materials, and processes for performance enhancement under a combination of stresses, since the product, in the use environment, experiences a multitude of stresses either separately or simultaneously. Reliability enhancement methodologies can be categorized as
1. Design methodologies
2. Physical enhancements
3. Underfills, encapsulants, coatings, etc.
Each of these is described in some detail in the ensuing paragraphs.