ELEMINATING FALSE POSITIVE ICT RESPONSE THROUGH THE USE OF ORGANIC-METAL FINAL FINISH

摘要

In-Circuit testing (ICT) is one of the most effective ways a Printed Circuit Board (PCB) manufacturer ensures the quality of its products. As the name implies, ICT tests components that are part of an assembled PCB. In other words, the components under testing are "in a circuit". The first and most critical part of an ICT testing is detection of shorts-and-opens. PCB final finish, which is the last step on the fabrication process, has the most significant impact on the ICT testing. Historically, there have been two major types of final finishes: organic or metallic. As the ICT test probes requires a conductive pad/surface to perform the test, metallic final finishes works well for ICT. Organic finishes, such as organic solderability preservatives (OSP), faces challenges when it comes to ICT testing. Many fabricators prefer to use OSP because of its low cost but end up losing the cost advantage by implementing additional steps on the fabrication process to add metallic finish to the test pads on a PCB, This paper will present results from a series of statistically designed experiments that includes different types of probes for in-circuit testing along with different types of final finishes to demonstrate pin testability of the various surface finishes. Through this exercise, we will be able to provide assemblers guideline in choosing the correct final finish for their end application.