Applying the physics of failure
What is the difference between ruggedness, ruggedization and reliability? Is a rugged card reliable? Is a ruggedized module reliable? How about vice versa? Many vendors claim they have rugged electronics capable of meeting the harsh environments of defense and aerospace applications. Does that mean their products are reliable?
Tin whisker growing out of a pure tin surface of a lead-free electronic component. Curtiss-Wright subjects assemblies to harsh environment sequences known to grow whiskers in order to evaluate the effectiveness of mitigations.
The above image shows an insidious failure mode known as pad cratering beneath a BGA solder ball. Curtiss-Wright has performed extensive testing on pad cratering and implemented a mitigation approach that substantially improves reliability.
Photo of PWB microsection showing microvia failure. Curtiss-Wright has been performing reliability testing (Interconnect Stress Testing) on production lots of PWBs for over a decade.
Let us take a look at some definitions
Rugged – strongly built or constituted (Source: Merriam-Webster on-line)
Ruggedize – to strengthen for better resistance to wear, stress, and abuse (Source: Merriam-Webster on-line)
Reliability – the ability of a product to function under given conditions and for a specified period of time without exceeding acceptable failure levels (Source: IPC-9701, Performance Test Methods and Qualification Requirements for Surface Mount Solder Attachments)
The ruggedness definition is the most vague, and leaves much to be desired in terms of clarity and specificity. Ruggedization is better, and allows for further definition such as the ruggedization levels of different product classes (e.g. Curtiss-Wright Ruggedization Table).
The reliability definition allows us to be very specific by defining “given conditions,” “period of time,” and “acceptable failure levels”. A deeper understanding of reliability leads to going beyond traditional metrics like MTBF (mean time between failures), and working to understand and apply the physics of failure (PoF). Curtiss-Wright COTS Solutions has been dedicated to such an approach for many years and we have built a broad and deep understanding of rugged electronics failure modes, mechanisms, and mitigations for a variety of environments. This hard-earned knowledge has been diligently applied to each new product we design and build.
Below are some examples of how this approach has permeated our design, manufacturing and test processes:
- Reliability Risk Assessment (RRA) process performed early in the product design stage to consistently apply our reliability knowledge base
- PWB reliability testing through Interconnect Stress Testing (IST)
- Sine and random vibration testing on every new product, with full functional testing during vibration
- Reliability Demonstration Testing (RDT)
- Solder Joint Reliability (SJR) testing
- On-going reliability research with leading universities and consortia to gain the latest knowledge, in particular for lead-free electronics
Engineered for Ruggedization and Reliability
The ability of a product to function under given conditions and for a specified period of time without exceeding acceptable failure levels.
Defines rugged environmental, design and construction, safety, and quality requirements for COTS plug-in units intended for mobile applications.
Curtiss-Wright COTS boards and systems mitigate technical maturity and product obsolescence issues using open architecture industry standards.
Curtiss-Wright implemented best practices for the design and production of lead-free assemblies to ensure reliability.