SMT007 Magazine

SMT007-Nov2018

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74 SMT007 MAGAZINE I NOVEMBER 2018 tronics and marrying rigid PCBs with flex. Can you talk more about that? Khan: Yes. Usually, the difference is in the change in the thermal coefficient between the rigid and flex boards, so it contracts and expands at a different rate. There is a differ- ence in bonding it together that needs special- ized lamination. Where to place the compo- nents—either on the rigid side or the flex side—is another challenge. Sometimes, the board is entirely flex with 16- to 20-layer flex circuits. Further, wire bonding of the devices is differ- ent because of the materials. It could be a gold wire bond, aluminum, or copper, depending on the application of medical devices. The thickness also becomes an issue. It could be one-mil aluminum wire or two-mil gold wire, but it could also go on a finer sub mil, like 20 microns. Concerning manufacturing, you have to be precise, control finer wires for bonding, and assemble them properly (wedge bond). What we see now is kind of a mixture of assemblies—a portion of it is SMT, and the other portion with microelectronics. The tech- nology is merging between traditional and microelectronics assembly, which is fine, but again, OEMs for medical devices need to go to somebody who can do all of these processes in-house because that's the way to manufac- ture it. You need to do SMT manufacturing first and cover all the areas where you'll be doing the microelectronics first. Once you finish with SMT, then you go to the clean room and finish up the microelectronics assembly. There's a process to making a product, whether it's a medical device or any other kind. You could have a hybrid of both, but then you need to make sure that you are going to the right EMS Company who has the process dialed in. Some startups are developing sensors in a specialized material that can measure the temperature of your skin and bodily fluids. Through the specialized material that they're developing, they can get an accurate reading of your body chemistry. Companies are trying to make machines that used to be huge, such as scanning oncology products for detecting cancer, into small portable devices the size of Figure 3: Wirebond clean room at NexLogic Technologies.

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