Design007 Magazine

40 The PCB Design Magazine • August 2016 things: the first is the elimination of solder; the second is the placement of all compo- nents (fully tested and burned in) beneath the surface with terminations facing up; and the third is selecting only components that have terminations on a common grid pitch. The combination of these three simple prin- ciples makes it all possible. Consider first the elimination (or at least the minimization or possible replacement) of the use of solder. Solder pads take up a signifi- cant amount of space on the outer layers of a circuit assembly leaving little room for routing circuits. The fact that hundreds of millions of dollars are arguably wasted annually, inspect- ing, testing of PCBs and assemblies, x-raying and repairing defective solder joints seems, if one reflects without prejudice, a reasonable thing to try and eliminate. However, there is also the cleaning process which is getting ever more difficult as lead pitches shrink. Eliminate (or replace) solder and you eliminate all of these wasted steps. The elimination of solder is made possible (with the least number of steps) by the second item from above. That is the building of the components into the board and then applying the circuits. More succinctly, rather than build - ing a circuit board and soldering components to the surface, build a "component board" and then build up the circuits on them. Some might consider this impractical but it can be done and fortunately while using nearly all of the current infrastructure. Circling back to the analogy that bikes work better without train - ing wheels, the manufacturing process can as well. The last item is perhaps the most challeng- ing because components come with leads on many different sizes, shapes, pitches and lead forms. J-leads, gull wing leads, though-hole leads, radial leads, pins, balls and even no leads Elimination of solder makes possible significant improvements in design efficiency. THE AUTHORS OF THE PRINTED CIRCUITS HANDBOOK SPEAK

• Cover
• Feature Content — Voices of the Industry
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• Column — Voices of the Industry
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• Feature — The Authors of the Printed Circuits Handbook Speak
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