Laminate Glass Weave Selection for High Speed Differential Pair Routing
Selecting spread glass fabric styles with tight yarn pitch eliminates differential skew and preserves PAM4 channel margins without complex trace routing.
Stackup Registration
Layer Alignment
Alignment of internal circuit patterns and drill holes ensures the electrical continuity of vias across all layers of a multi-layer board. In board fabrication, stackup registration measures the accuracy with which each circuit layer is positioned relative to the others and the drill coordinates. This positioning is critical for establishing reliable connections without breaking out of internal annular rings.
Artwork Position
Manufacturing tooling pins and optical alignment cameras align each layer during the lamination layup process to prevent shift. The pins must fit precisely into registration slots routed into the borders of each panel to minimize rotational and translational errors. As the stack of material is compressed and heated, the layers can slide, requiring careful tensioning of the fixtures.
An inaccurate registration will cause drill bits to miss the center of internal pads, leading to open circuits or short circuits between adjacent vias.
Inspection Method
X-ray imaging and cross-section analysis are the primary non-destructive methods used to verify internal registration after lamination. These tests measure the offset between specific test targets etched into the margin of each layer. Continuous monitoring of these registration offsets allows fabricators to adjust their scaling factors and tooling setup to maintain high yields.