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90 PCB007 MAGAZINE I MAY 2020 Introduction There are many reasons to get incredibly frustrated and confused when presented with complex issues related to the PCB fabrication process. There is much room for error, and of- ten, the simplest little detail overlooked leads to significant product quality loss. Consid- er the design requirements, along with more stringent reliability performance, and there is a recipe for defects, such as delamination. Let's review the concerns with the possibility of multilayer board delamination and the root cause or causes of the defect. Delamination Versus Laminate Voids When reviewing the potential root cause of delamination, the first thing the troubleshooter must do is determine if the anomaly is delami- nation or a lamination void. They are different as to the root causes of each. And once this is recognized, the protocol—along with fishbone diagrams and brainstorming—can begin. Voids are not a separation of the resin from the copper. Rath- er voids are basically air pockets formed within the multilayer pack- age. An example of laminate voids is shown in Figure 1. IPC-T-50 defines a void in lami- nate as a circular pocket within resinous area of laminate, usually formed by entrapped air or volatile materials and at or near the surface of the laminate. The prepreg or prepreg/laminate surface may show small voids. Lamination and Delamination These may expand when subjected to solder- ing or reflow. Small voids in the board may bridge conductors, pick up moisture, and cause electrical shorts. Delamination is a horse of a different color. Delamination is defined by IPC T-50 as "a sep- aration between plies within a base material, between a base material and a conductive foil, or any other planar separation within a printed board"—the key concept being separation. Blisters, even on inner layers, affect the sur- face of the printed board. A bubble will be able to be felt when touched. Understanding the root cause, however, is most critical at this juncture. A blister doesn't necessarily equate to classic delamination. Nonetheless, the blis- ter is a separation and most likely caused by moisture within the laminate package. What Trouble in Your Tank by Michael Carano, RBP CHEMICAL TECHNOLOGY Figure 1: Laminate voids.

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