Page 29

EETE APR 2014

Reduce production cost by minimizing the cost of repair By Peter van den Eijnden Electronics manufacturi ng is ready to head back to Europe as the high level of automation in both assembly and testing alter the economics of electronics production, making the process far less labor intensive. Moving the production closer to the home markets also reduces shipping costs and time, which again reduces costs and improves efficiency. The ultimate goal of an Electronics Manufacturing Service (EMS) provider (or CM) is to deliver Printed Circuit Board Assemblies (PCBA’s) that are free from manufacturing defects. EMS providers typically deal with (high-tech,) high-mix, low-volume production per board type. Consequently many different types of boards are manufactured on the same production line posing an extra challenge on the “free from manufacturing defects” goal. As manufacturing defects are always present, testing is required to find the defects and repair them. To keep the repair costs low it is vital to reduce the chance for defects to happen, to maximize the fault coverage and to early detect and accurately locate the defects in the fastest possible way. Reducing the chance for manufacturing defects A minimal number of manufacturing defects is introduced by using a high quality assembly process, by applying Design for Manufacturing (DfM) rules and by minimizing the amount of manual labor involved (full reflow). High quality assembly equipment together with strict process control minimizes the possibility of introducing manufacturing defects, ie minimizes the Defects per Million Opportunities (DPMO). By assessing the feasibility of the assembly of a Printed Circuit Board during the design stage and correcting it as needed the physical board design is best matched to the capabilities of the assembly line and the chance for manufacturing defects is reduced. By further combining the DfM approach with the use of Surface Mount Devices (SMD), PCBA’s can be built with full reflow, using far less manual labor. All measures together result in a maximum first pass production yield and thus a minimal amount of repairs. A yield improvement of y percent means that y percent less boards need to be repaired. Maximizing fault coverage Optimizing the assembly process results in a minimum number of manufacturing defects and hence a minimal number of repairs. In addition a test approach for detecting manufacturing defects that provides immediate localization of defects minimizes the cost of repair per board. Detection of all possible defects is generally not feasible and boards containing one or more undetectable manufacturing defects slip through to the next level. To minimize such slip the test approach should provide maximal fault coverage. Using the right test methods and applying Design for Test, or DfT, leads to a maximum fault coverage and accurate and cost effective localization of defects. Structural testing specifically focusses on detecting manufacturing defects. This test method provides immediate pin-level diagnostics and requires no manual troubleshooting, minimizing labor and the diagnostics time. Structural test comprises both “visual” inspection methods (manually or automated) as well as specific electrical test methods. Peter van den Eijnden is is Co-founder and Director of JTAG Technologies - www.jtag.com learn more Compensated Basic Board Mount Pressure Sensors EE-Times_Europe_277x91_FINAL.indd 1 3/31/2014 1:30:17 PM www.electronics-eetimes.com Electronic Engineering Times Europe April 2014 29


EETE APR 2014
To see the actual publication please follow the link above