At What Stage Are Most Product Reliability Problems Introduced?

Initially the theoretical design aspects of the design are used in combination with the weakest or lowest technical component specifications as reference to be used prior to the production of the prototype samples for the supposed product..

The prototype production is followed by a series of functional and quality performance process where the final testing results and evaluations are combined and subjected to a following of simulated environmental performance application processes..

In practice This pass/failure testing stages of the final QA processes of the prototype product is where the combined product reliability is determined and established.... And which are incorporated prior to the manufacturing the final product..

I agree that prototype validation and environmental stress testing are critical stages for establishing confidence in product reliability. However, from my experience with electronic systems, I've found that many reliability issues are effectively "designed in" long before the prototype is built.

For example, component derating, thermal margins, signal integrity, power integrity, PCB stack-up decisions, and supply chain component selection can significantly influence long-term reliability outcomes. In many cases, qualification testing doesn't establish reliability; it verifies that the design and manufacturing processes have met the intended reliability targets.

This raises an interesting question: do you think the industry relies too heavily on pass/fail prototype testing, rather than incorporating reliability engineering principles earlier in the design and component selection process?

I'd be interested in hearing how others balance design-for-reliability practices with prototype qualification and environmental testing.

You may have missed to read the 1st paragraph in my response.. This is where the quality, function and integrity of each every components you used are determined

Which means that your component selection processes is relying on the corresponding QA of whoever manufactured those selected components..

Which also means that the functionality, quality and reliability of your chosen product will mostly be dependent upon your knowledge, experience and technical ability to apply and implement your goals and objectives..

Sorry, my bad, I think you've highlighted an important point regarding component selection and the engineer's responsibility in applying those components correctly.

One aspect I'd add is that some reliability issues only become visible after products accumulate significant operating hours in the field. Accelerated testing and qualification can identify many failure modes, but they don't always capture every real-world operating condition or use case.

This is why industries such as aerospace, automotive, and semiconductor manufacturing place so much emphasis on field-return analysis, reliability growth programs, and continuous feedback into the design process. In many cases, the most valuable reliability data comes not from the prototype stage, but from understanding why products fail after deployment.

Would you say that long-term field performance data is ultimately a more accurate measure of product reliability than prototype qualification testing alone?