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28 The PCB Design Magazine • August 2017 FAULT-FINDING: IT'S ALL ABOUT PREVENTION, NOT BLAME who's at fault. It is more of a 10,000-foot flyover of a project or process, tailored to determining where, in a progression of events, the root cause of a problem occurred so that it can be identi- fied and corrected. Once an organized, logical, process-oriented approach has been implemented in order to determine the root cause of a problem, what is the next step? How can we best convey the re- sults? We are fortunate that our PCB manufac- turing industry stakeholders have been around long enough to establish successful processes and can usually recognize when a process needs to change or evolve. PCB manufacturers are very familiar with a form of communication between customer and supplier known as the corrective action report (RCA) request. When an unacceptable problem is identified by a cus- tomer, it is common for the customer to issue a CAR request to the supplier as a form of good business practice and clear communication. The CAR request is intended to communicate that a problem was found and determined to be rooted somewhere in a process owned by the supplier. The CAR request is carefully generated to identify and define the problem, such as a non-conformance issue relating to a hole size or finish defect and respectfully convey it to the supplier. Simply, the CAR protocol requests the supplier to perform three basic steps in order to improve their process so business can continue: 1) Acknowledge ownership of the defect. 2) Be able to point to an established process and identify where the defect occurred, when it occurred and how it occurred. 3) Be able to explain to the customer how the process shall be corrected so that the problem will not occur again. Let's face it. Problems happen within any system with human involvement. Mistakes will be made, and process will break down. How the call-and-response format is tendered will affect the success of both parties. Hopefully your de- sign team will see that a compelling CAR proto- col between customer and supplier is far more propulsive to product success and good business than a desperate call for a merciful beheading. RCA stresses that preventing a future snafu is far more important than identifying the ac- tors responsible for the current foul-up. When a customer issues a CAR request, a general process for performing and documenting RCA correc- tive action on the part of the suppler is outlined like this: That Day we Received Pink PCB Assemblies Oh, if our engineering, manufacturing and purchasing groups had only possessed some RCA skills the day we started receiving pink PCB assemblies! A while back, my job involved de- signing LED boards that were used to backlight colorfully silkscreened glass panels. Our engi- neering customers had specified the color of the PCBs to be white so as to enhance the reflectiv- ity of the boards behind the glass. Anyone who has walked down the paint aisle of Home Depot will quickly realize that there are many shades and hues of white. But to keep things simple on our PCB fabrication drawing notes, the solder resist color was specified as "white." Depending on the supplier of the bare PCBs, I had noticed various shade or hue differences from part number to part number. Sometimes the hue would be slanted toward gray. Some- times the color would be shifted to a tan we called "toasted almond." Every so often, the hue would be slightly pinkish, which we referred to as "mauve." But for the most part, our many various PCB designs requiring white solder re- sist would pass incoming inspection because they were, well, "white-ish." All seemed fine until our department's new purchasing clerk arrived and placed a new order for white PCB assemblies. Upon receipt, the box was opened and our entire design group heard the exclamation: "These boards are not white— these boards are pink!" Within a 48-hour period, the purchasing clerk had drafted a list of several possible suspects and organizations to blame. This new "problem," which was never identi- fied as a problem previously, had been iden- tified by a fresh set of eyes. The drama began to attract the attention of many others in the department, each with his own hypothesis on why the board assemblies were pink. Bare board suppliers were suddenly calling designers and describing how they were being accused of us- ing pink solder resist by our purchasing depart-

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