Quest for Reliability

By Eric Camden

If you follow industry standards, does that mean you'll have improved reliability? It depends.

 

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Standards have been around in the industry as long as the industry itself. But if they are followed, does that mean that you’ll have improved reliability? The answer is a famous one in certain circles: it depends.

It depends on a few things, such as the product’s intended use and warranty. If you are building something that must work only as it leaves the facility and is considered a Class I product, then reliability isn’t something you need to worry about. But having been in electronics for just shy of 20 years, I can say that the next time we work on a Class I failure analysis project, it will pretty much be the first. Class I electronics serve a different purpose in life, and if they fail, it’s normally not a big deal; instead, it’s mainly a minor inconvenience. 

 

In this article, I’ll speak to specifications for Class I, II, and III products per IPC definitions as well as the IPC standards process. 


Class I, II, and III

The low-cost materials and disposable nature of Class I products basically preclude them from ever being labeled as high-reliability. Within IPC guidelines for Class I, the assembly guidelines are very different than Class II or Class III. This isn’t a knock on Class I products by any means. IPC’s definition for Class I is, “includes products suitable for applications where the major requirement is the function of the completed assembly.” There’s not a single word about reliability or critical nature of their intended use. 

 

Class II is defined as dedicated service electronic products, which “includes products where continued performance and extended life is required, and for which uninterrupted service is desired but not critical. Typically, the end-use environment would not cause failures.” Class II products would be found in a lot of automotive electronics (not related to safety) as well as harsh environment electronics that may not necessarily be life-critical but are expected to operate for 20+ years. 

 

Class III is defined as “products where continued high performance or performance-on-demand is critical, equipment downtime cannot be tolerated, the end-use environment may be uncommonly harsh, and the equipment must function when required, such as life support or other critical systems.” These electronics are most commonly found in industries like healthcare and aerospace. When your life or the life of others  is on the line, Class I simply won’t do. 

 

The standards for assembling Class II and III are well known, with IPC J-STD-001 being the cornerstone of the J-STD series of standards. J-STD-001 is titled “Requirements for Soldered Electrical and Electronic Assemblies,” which covers a lot of ground. The Technical Activities Executive Committee (TAEC) says, among other things, that standards should focus on the end-use environment, not tell you how to make something. That last part is very important to remember because standards aren’t the full recipe necessary to build electronics; they should be considered a guideline to reference when there is uncertainty on how to do some part of the process. The order of precedent on any drawing should be as agreed between the user and the supplier and standards like J-STD. This helps to drive home the point that IPC standards are not necessarily the final word on how to build a PCBA, but should be used as a companion to the demands of the customers.

 

IPC Standards Process

IPC standards are nearly ubiquitous these days on most all assemblies, which is a good thing. IPC standards are written (and constantly rewritten) by some of the best minds in the industry, and me. Seriously, they will let literally anyone come to the task group meetings and have some input on what the next revision should look like. 5-22A J-STD-001 is one of the largest task groups of the many focused ones, such as the 7-31B IPC-A-610 Task Group; it’s one of the few meetings that lasts all day, including a review of how it plays with other standards on a different day. It’s tied to training, and there is another task group for J-STD on how to teach the class and what updates within J-STD-001 will impact that training. In other words, it’s a big undertaking. 

 

One of the things I appreciate about the standards process within IPC is the fact that most are constantly being reviewed to react to changes within the electronics industry. This is of the utmost importance when you think about changes spurred by things like the required implementation of lead-free solder or trying to keep up with miniaturization. This requires reviewing and updating the assembly process that needs to be reflected in the standards, which is why it’s so necessary to meet face-to-face during the year to make sure everything is being covered. 

 

The latest update to J-STD is a great example of how the standards are ever-evolving for the betterment of the industry. A cleanliness standard that was initially a military standard in the 1970s and then adopted by IPC was written into a lot of product drawing requirements. This is the resistivity of solvent extract test that at one point was a good test for monitoring for gross changes in the process. The test was used and abused over time for process qualification when that was never its intended purpose.

 

Recently, J-STD was updated to include better analysis recommendations for process qualification while leaving the option to continue using the ROSE test if you have historical data showing that it is effective for the purpose for which you are using it. Basically, if it ain’t broke, don’t fix it. But the fact the industry recognized that the test was no longer enough for qualifying today’s materials and component styles is proof that people within the industry are taking ownership of their processes and not simply relying on historical testing protocols that worked 20 years ago.

 

Conclusion

The best thing about standards is the fact that they will always be second to what is agreed upon between the user and the supplier. Nobody knows more about your product than you do, but in lieu of internal specifications, industry standards are a great option. They are all written by companies that require reliability as part of their standard, so you can expect the same.

 

Eric Camden is a lead investigator at Foresite, Inc.

 

 

For additional information, contact Foresite at foresiteinfo@foresiteinc.com or call 765-457-8095.

 

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