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PCB-Apr2017

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56 The PCB Magazine • April 2017 In today's testing theatre, the flow of infor- mation from the OEMs and manufacturers to the independent contractors is mission critical. Missing information can cause delays, incorrect processing and ultimately scrap or end user re- jection of the product. The buzz term being used a lot today is "flow-down." It pretty much de- scribes itself: It is the flow of information down the supply chain. So let's go with the flow, shall we? We will break it down in the flow required for correct electrical testing of an unpopulated printed wiring board. 1. The OEM designs the latest must-have innovation for the market. Time is critical to get this product built, tested and on the shelves so that little Johnny will not be disappointed on his upcoming birthday. Now, the design engineers have painstakingly designed in all the impedance, IC footprints, material require- ments, impedance/inductance and resistive components, and have written it in their design specifica- tion document. Since this is a new product and top secret the document is then saved at their top secret secure location (along with the noto- rious 11 herbs and spices). 2. The OEM procurement department now receives the build request from the engineers and proceeds to shop vendors for manufactur- ing. They may send out many RFQs and each time they need to be specific on what they want manufactured. Here is the first major flow-down example: When the RFQ goes out they must be very specific on what they wish to receive. In- formation here are the general manufacturing requirements (IPC-6011, IPC-6012) but also the specifics that may be outlined in the top-secret design specification document the engineers created in section 1. What are the special re- quirements for characteristic impedance, dielec- tric breakdown, continuity and isolation? What is the performance class expectation? Does this board need to pass military perfor- mance specifications? by Todd Kolmodin GARDIEN SERVICES Go With the Flow TESTING TODD

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