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16 The PCB Design Magazine • June 2014 part in 100 to plus/minus 0.002", then let's use that as a spec." Neither price nor yield was important to those uses—the only thing that mattered was performance, and FPC provided that wherever it was used. As the years passed, industry or- ganizations came on the scene, and they wrote whole catalogs of specifications and test proce- dures, all with the intent of completely button- ing down everything from raw material to pro- duction code marking. This documentary effort lowered the variation from vendor to vendor and improved product quality, but at a considerable effect on cost, hampering the use of FPC in commercial goods. Latterly, with increasing familiarity with the benefits of FPC in volume production—near elimination of interconnect errors, steep reduction in la- bor content and so forth— these excessively tight specs have been perceived as un- necessary, with the result that today we're moving towards the "form, fit and function" end of the spectrum. But we're not there yet: FPC is still subjected to excessive physical and visual inspection to tolerances which are not necessary to assure reliable func- tion, but the situation is improving. A procur- ing engineer will always review the product specifications and quality control requirements to be sure they cover everything that matters and have limits to produce good product, and work with the prospective vendor to agree on specifications just tight enough to yield good product at the best price. Secondly—and this may seem obvious and unimportant, but is a big issue—FPC is not a catalog item. It is a custom manufactured item and that makes a world of difference. A short story to illustrate: Once upon a time a consortium of PWBpeople bought control of an FPC manufacturing company. The PWB guys with their "commodity production" mindset thought the FPC managers were unimaginative and behind the times and that PWB manage- ment ideas and efficiencies would quickly turn a poorly managed business into a winner. This rosy thinking lasted through the first year, at which point the PWB guys realized that things were very different from what they first thought. In another year the company was dead and the assets sold at auction. Unfortunately for the PWB guys (and their bankers), this lesson was learned too late for fi- nancial recovery. What looked like an inefficient operation ripe for profit tweaking was actually a pretty savvy and experienced one struggling with an overload of variables and tight specs in a manufacturing environment significantly (perhaps 3X) more complicated than the one they knew. The biggest mistake in this tragic tale lay in the over- powering assumption that producing and selling FPC is the same as making PWBs, or razor blades, or any com- modity. Buying PWBs or FPC— anything that is built to a custom design—is very differ- ent from other procurement. To begin, you are trying to buy something that does not even ex- ist yet! Both of these products, but particularly FPC, have proven their worth as cost reducers in electronic assemblies. PWBs have reached the maturity of a commodity; FPC isn't there yet, but it's gaining. Use of FPC is rising rapidly: In this modern world we would not have digital cameras or smartphones or any of a hundred other high functioning, complex, yet reason- ably priced and rugged products we use every day without a piece of FPC, deep inside, provid- ing error-free, semi automated, rugged intercon- nections. If you expect your new electronic gad- get to make a profit, FPC is almost mandatory, and if you understand why the buying process is different, you can approach FPC procurement with confidence. Sales or Contract Negotiation Every manufacturer has a sales department, but in the FPC business it functions quite differ- ently. In the FPC world, bringing customers in the door isn't selling; it's contract negotiation. feature WHY PRoCURINg FLExIBLE PRINTED CIRCUITRY IS DIFFERENT continues FPC is still subjected to excessive physical and visual inspection to tolerances which are not necessary to assure reliable function, but the situation is improving. " "