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Page 132 of 147

SEPTEMBER 2020 I SMT007 MAGAZINE 133 in Figure 20. Nothing goes over the 5% thresh- old, and Figure 21 shows a 100% pass. The difference is in dielectric, and laser via diame- ter was half of one of my hair's thickness, and that is even the manufacturing process win- dow shop. It is extremely critical that the geometries are conducive for the reliable passing of OM test- ing, and your boards will pass through assem- bly, just as well. Summary In summary, the OM test validation will prove that your design and material selections and structural constructions meet today's chal- lenging PCB requirements. It is validated by actual reflow conditions to your design geom- etry and detects failures at reflow that heal at room temperature. These test records are the actual temperature on the coupon and resis- tance values. It validates propagated via struc- tures that match the PCB design and are con- sistent with IPC-6000 requirements. This data collection allows for better design practices. As you find designs that are not conducive for passing, you may want to change your design and increase the diame- ter of the microvia to eliminate certain struc- tures and make your designs more reliable and profitable. SMT007 Figure 20: Remake with correct via and dielectric. Figure 21: 100% pass with the correct via and aspect ratio.

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