IPC International Community magazine an association member publication
Issue link: https://iconnect007.uberflip.com/i/1543955
48 I-CONNECT007 MAGAZINE I MARCH 2026 Multilayer Presses and Process Cycles The welded coupon bonding process is like the induction lamination process (Figure 6). The welded book can better withstand the dilations and shrink- ages of the hot-press cycles, allowing the best pos- sible linear movement of all layers during lamina- tion. It reduces internal stresses that cause warping and deformations, and moreover, reduces distor- tions and misalignments between inner layers. Another practical benefit is that welded multi- layer stackups can be X-rayed to check before and after lamination to verify registration and help adjust compensation factors. Advantages of Pinless Lamination Pinless lamination offers several advantages: • Increased layer-to-layer registration accuracy • Increased process predictability and im- proved registration data • Improved ability to characterize lamination press processes • Better registration of thin cores (accurate and consistent) • Flexibility using lamination plates without tooling holes • Fewer lamination plates required (usable across multiple panel sizes) • Separator plates without tooling holes (fewer sets required) • Cleaner operation (no resin-filled tooling holes to clean) • Prepreg does not require pin clear- ances (minimizes prepreg dust) • More flexibility in panel sizes without pin restrictions • Elimination of pins and bushings (remove consumables) • No depinning required Impedance Planning and Signal Integrity The advances in semiconductor fabrication over the past 50 years have been dramatic. When I start- ed college, integrated circuits had only a handful of transistors. Today, many devices contain billions. That's revolutionary, but it also means transistors switch extremely fast. As a result, many PCB interconnects must be treated as transmission lines even when the system clock appears relatively slow. For multilayers, im- pedance planning and signal integrity are essential. Verification of the multilayer stackup with the fabricator is critical because the final pressed thicknesses will vary between fabricators and can differ from datasheet values. Field-solver selection is also important, as well as these factors: • Dielectric height and crosstalk control • Dielectric and hybrid material selections • Fiber-weave effect • Stackup wizard accuracy and limitations • Detailed understanding of plating impacts • Stacked vs. staggered vias H A P PY'S T EC H TA L K # 47 Figure 6: a) Induction lamination cycle; b) Stackup welding cycle.