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PCB007-June2021

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22 PCB007 MAGAZINE I JUNE 2021 is is a relatively simple question but one which conjures up some technically diverse potential answers, each of them necessarily weighted by several qualifying questions to make certain they will meet the end product's require- ments. is is a seemingly small but very impor- tant detail and thus precludes the notion of being able to offer up a universal "next best" solution. at said, there are several historical choices for making electrical connections between compo- nents and PCBs without relying on traditional sol- der. e most common is arguably a conductive adhesive, both isotropic and anisotropic types, which have been in use in electronics for many years. eir limitations are that they are generally less conductive and do not generally provide the kind of bond strength that solder does; thus, they may not be as resistant to shock and vibration as solder. e components are oen "glob topped" to hold them in place and this, unfortunately, makes rework problematic and makes them more susceptible to overheating in operation. More recent years have seen the rise of low temperature sinterable alloys enabled by nan- otechnology. Included among these is a na- no-copper "solder" from Kuprion. ese show promise and are finding some traction, but wide acceptance is not yet here. Another historical method that has been large- ly reserved for connectors is press fitting of leads into plated through-holes. When intelligently designed and assembled, press-fit connections can be quite reliable and provide a gas-tight seal between lead and component. Obviously, the method precludes the use of most SMT devices. Socketing of components is another method of interconnecting components to a printed cir- cuit without solder but sockets add expense and typically are soldered to the board themselves. A method I have been promoting for more than a dozen years through my company, Ver- dant Electronics, is solder alloy-free electron- ic (SAFE) assembly which seeks to obviate the need for solder. is objective is accomplished using a novel reverse approach to manufactur- ing where components are first attached to a carrier with planar leads facing up and circuits are built up by directly plating copper to lead terminations using familiar printed circuit man- ufacturing processes. e elimination of solder precludes the need for numerous process steps. Concerns have been expressed about the need for rework and repair, but it is arguable that the need for rework and repair is evidence of a process that has intrinsic control issues, mak- ing rework and repair a necessity. My credo has evolved to, "If we seek to make the best prod- ucts possible, we must first do all the right things and then do all those things right." For more de- tail, please read my May 2021 column and/or my free I-007 eBook, Solderless Assembly For Elec- tronics—e SAFE Approach. PCB007 Joe Fjelstad is founder and CEO of Verdant Elec- tronics and an international authority and innovator in the field of electronic interconnection and packaging technologies with more than 185 patents issued or pending. To read past columns or contact Fjelstad, click here. Download your free copy of Fjelstad's book Flexible Circuit Technology, 4 th Edition, and watch his in-depth workshop series "Flexible Circuit Technology." Beyond solder, what's the next best interconnection between the components and the PCB? A Q

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