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68 PCB007 MAGAZINE I AUGUST 2020 New Laser Method for PCB Depaneling Increases Process Utilization Article by Frank Gäbler COHERENT INC. Technological changes in the materials, thickness, and composition of PCBs are moti- vating a move away from traditional mechani- cal cutting and depaneling methods toward laser-based processes. But not all lasers for PCB depaneling are created equal. There are significant differences among various lasers in cut characteristics and quality, specifically in terms of the heat-affected zone (HAZ). This, in turn, affects process utilization since it determines how closely circuits can be placed on a PCB, and can also impact circuit functionality and downstream processes like waterproofing or EMI shielding. This docu- ment presents a new nanosecond laser and as- sociated cutting process developed at Coherent Inc. that enables laser depaneling with sub- stantially reduced HAZ compared to other cur- rently available products. Why Laser Cutting? The market increasingly demands physically smaller and thinner PCBs, which offer greater functionality and improved energy efficiency. Manufacturers must deliver all this in a highly competitive cost environment. In terms of con- struction, this has meant greater use of thinner traditional boards, wide-scale implementation of flex circuitry, thicker conductive layers, and increased utilization of low-k dielectrics (the latter especially for 5G technology). One way to manage cost is through improved process utili- zation. Specifically, this means placing boards closer together on a panel to increase yield. In terms of cutting and depaneling, all this necessitates increasingly narrow kerf widths and higher dimensional accuracy for the cut- ting process. The closer physical proximity of the cut to the functional areas of the PCB also means that the cutting process must not affect the surrounding material or circuitry, whether due to mechanical stress or heat. Another requirement is minimal production of debris, which might require a subsequent cleaning step.

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