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Bob Neves discusses a disconnect he sees in reliability testing between what’s being tested and what happens out in the field, as well as why most reliability tests these days should instead be considered robustness tests.
Nolan Johnson: What are the current dynamics in assembly reliability?
Bob Neves: My history and focus are primarily within the electronics industry surrounding PCBs. My customer base at Microtek, and for testing and evaluation, are the suppliers to the PCB manufacturers, the PCB manufacturers themselves, and the users of PCBs. When we talk about testing, most people who buy PCBs look at the PCB like they would look at a resistor or capacitor—it’s just another component on their build list. The truth is that you really can’t treat the PCB as a component. You need to look at it as a very complex subsystem like you were buying a power supply or some other multi-component assembly that did something for you rather than just a single attribute component like a capacitor or resistor.
The PCB is relied on for passing signals between components and isolating signals from places they’re not supposed to be. When things go bad in an electronics assembly, those are typically the areas where you start looking. Is the signal getting to the correct spot, or are we losing signal some place where we’re supposed to have a signal? A lot of problems that I’ve experienced have to do with the fact that something’s gone wrong in the interconnection or isolation process on the PCB. Engineers come to me, saying, “If I press down on this component, it works,” or, “If I heat it up with a hot air gun, my system works. But if I take it off, it doesn’t work anymore.” That’s where a lot of failures end up being PCB related.
Reliability starts for a product after the component attachment process. After you’ve put all the components on, changed anything that was bad, tested it, and it’s ready to put it in the field, that’s when reliability starts. Any reliability you’re testing—whether it’s on the bare PCB, a component, or the entire assembly— needs to have some sort of simulation that shows that it’s gone through this component attachment process, getting you all the way up to the point of where it would be going out the door. That’s one feature that not everyone does before testing. A lot of people will take a component and then do testing on that component as it comes in the door, or they’ll electrically test a PCB before component attachment and say, “Everything’s great.” But any type of testing that you do to see how long your product might last needs to have some sort of simulation of the soldering process before testing. That simulation also needs to include the rework and repair part of the component attachment process.
To read this entire conversation, which appeared in the September 2020 issue of SMT007 Magazine, click here.