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62 SMT Magazine • March 2017 Galloway: We are starting to see peo- ple put BGAs on flex. We've even seen chip scale BGA packag- es on flex. Just be- cause you can do something doesn't mean you should do it. A rigid-flex may be more appropriate in these cases. While flex circuits require specialized handling during manufacturing, the real concern would be robustness in the field since flexing of the material during transport or use of the product could result in degradation of solder joints. Las Marias: What about the challenges with respect to flexible circuit materials? Galloway: We have had limited issues with different flex materials. The suppliers we use are experts in the field and we have discussions with them on best ways to process specific substrates. Las Marias: What has the greatest impact on the quality of flexible circuit assemblies? Galloway: The support factor in processing. Tooling must keep the flex circuit flat and im- movable. Las Marias: In which end markets are you see- ing increasing use of flexible circuits? Galloway: We are seeing across the board: consumer applications, industrial equipment and medical. We aren't seeing it defense appli- cations. Las Marias: What should OEMs consider when choosing an assembly partner for their flex circuit assembly? Galloway: Have an open dialogue with the contract manufacturers you are considering to see how comfortable they are with flex circuit as- sembly and what their experience and capabili- ties are. Make sure more sensitive components such as BGAs are on a rigid portion of the flex. Also, make sure fiducials are in the design. We've seen a growing trend of designers leaving out fi- ducials. They are critical to accurate component placement on any substrate. The fiducials can be placed on the rigid, flex or the panel. This is an area where contract manufacturers may have in- dividual placement preferences so having open dialog during the layout process is important. Las Marias: Do you have any final comments? Galloway: Flex may seem exotic, but with a little extra care can be a reliable way to get elec- tronics into highly mechanically-constrained environments. Following a few guidelines and talking with your manufacturer will help to take the mystery and risk out of using flex circuits. Las Marias: Thank you very much, Mike. Galloway: Thank you. SMT Mike Galloway With RoHS requirements in full swing, companies must adapt and adapt quickly as lead based soldering will be completely phased out by 2019 in Europe. In this interview during the recent IPC APEX EXPO 2017, Tim O'Neill, technical marketing manager at AIM Sol- der, discusses their two new lead-free alloys that are proving to en- hance reliability for high-end applications while minimizing issues with voiding. Watch The Interview Here Real Time with...IPC: Tim O'Neill Discusses Latest Developments in Lead-Free Soldering Market FLEX-CIRCUIT ASSEMBLY SUCCESS HINGES ON MSL CONTROL AND PANELIZATION

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