Modified Semi Additive Process Yield Loss Recovery Contract Mechanics
Modified semi additive process contracts require clear yield baselines, defect attribution formulas, and flash-etch metrology to recover scrap costs cleanly.
Electrodeposition Non-Uniformity
Surface Morphology
Current variance dictates how evenly copper grows across the surface of a panel during the bath cycle. Any electrodeposition non-uniformity results in traces being thicker near the edges than in the middle. Uneven metal distribution impacts the electrical impedance of fine conductors.
Plating Variance
Ion travel follow lines of force that cluster around isolated features or large ground planes. When electrodeposition non-uniformity occurs, it stems from high current density at corners that pulls more metal from the solution than flat areas. Using thieving patterns or shields reduces this effect by leveling out the electric field across the whole frame.
Technicians monitor the chemical additives every four hours to ensure the brighteners prevent localized overgrowth. If the solution is not perfectly balanced, copper builds up rapidly on high points, which eventually leads to short circuits after etching. These variations also affect the flatness needed for components with many small pins.
Mechanical Impact
Physical differences in trace height create difficulty during the solder masking stage. Widespread electrodeposition non-uniformity leaves some areas too thin to carry the full power load required by the circuit. Boards fail inspection if the height difference exceeds the tolerance set in the master drawing.