Resolving Inter Site Fabrication Discrepancies in Automated Module Packaging Files
Containerize module fabrication data in IPC-2581C to lock CAM modifications, enforce netlist parity, and eliminate inter-site geometry discrepancies.
Etching Compensation
Meaning
Positioned between circuit layout export and photolithography tool preparation, CAD pre-processing alters trace width geometry on photomasks to offset lateral undercut during chemical milling. Liquid etchant removes copper vertically through the resist opening while simultaneously attacking exposed sidewalls horizontally under the photoresist layer. Applying etching compensation widens designed track widths on the production master tooling so that finished circuit features match target nominal dimensions after wet processing.
This geometric adjustment ceases to apply on laser-direct imaging systems that dynamically modulate beam power to control line width tolerances without altering source CAM files.
Geometric Modification
Adding predictable overhang margins to conductor paths preserves target trace impedance across heavy copper layers. Thick copper weights experience greater lateral undercut due to extended spray chamber residence times during fabrication. Process engineers apply specific factors based on copper foil weight and chemical etchant concentration.
Layer Variation
Outer circuit layers require distinct modification factors compared to inner signal layers due to differential plating steps. Differential etch rates between isolated lines and dense trace arrays complicate uniform feature width delivery across large panel areas. Unadjusted artwork results in narrow conductor cross-sections, raising DC resistance and thermal dissipation across power distribution nets.
Signal Integrity
Controlled line widths maintain designed differential pair impedance.