PCB007 Magazine

PCB007-July2019

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40 PCB007 MAGAZINE I JULY 2019 going to monitor process control and provide validation. The pass-fail method was designed in the '70s when the Bee Gees were on the ra- dio every other song. I'm glad we're not in the '70s anymore for a number of reasons, but the standard we've been using until last October was established in the '70s. Boards, of course, have changed dramatically since then. Shaughnessy: You used IoT as an example of electronics now being in environments that are new and nontraditional. Can you talk about some of the contamination effects? Konrad: It's not often that we are in a revolu- tionary moment. Usually, we're in an evolu- tion, but now, the revolution of electronics has allowed us to largely take consumer goods and throw them into harsh environments. We're putting electronics into smart electrical meters that are in harsh environments outside of hun- dreds of millions of homes. We're putting elec- tronics in toothbrushes and refrigerators and accelerometers in footballs and tennis rackets. All of these things experience harsh environ- mental conditions. Whenever the temperature or humidity increases, the amount of residue tolerance decreases. With what would normal- ly be Class 1 electronics—which really have no high expectation of reliability— we're throwing them outside and causing them to fail. The explosion of IoT—and tak- ing electronic components and as- semblies and putting them in plac- es where we traditionally have not had them—is creating a need to re- move residues more than it would have before. Normally, we remove residues if somebody is going to die if the component or the assem- bly fails. That's considered a high- reliability requirement; we clean so we don't kill people. Now, a lot of consumer goods—even Class 1 con- sumer goods—are being cleaned because it will create a better repu- tation for the manufacturer. For ex- ample, the failure of an electronic flea collar will not kill anyone; you just have an itchy dog. We're seeing a lot of things being cleaned that historically—at least in the last 30 years—were not. Shaughnessy: Are you talking about contami- nation during manufacture that presents once the product is deployed? Konrad: Yes. Ionic contamination, specifically, is not an issue unless it's merged with mois- ture and electrical current. Three factors work together to produce electrochemical migration, which has a number of knock-on fatal effects on an assembly: ionic residue, moisture, and electrical current. Remove any one of those three, and you solve the problem. If the power is turned off, electrochemical migration won't occur. Prevent the assembly from ever coming into contact with moisture, and we can leave residue on the assembly. In most cases, how- ever, we really can't prevent moisture from ever contacting the assembly. And we certain- ly can't suggest our customers turn off their products to improve reliability, so what's left is to remove the residue. Shaughnessy: Are you doing seminars around the country on this topic? Michael Konrad presenting at the 2019 IPC High-Reliability Forum and Microvia Summit.

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