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.
Titanium Seed Layer
Adhesion Interface
Metallic adhesion layers are deposited onto a substrate to provide a conductive surface for subsequent electroplating. The titanium seed layer acts as a bonding agent between non-conductive materials like glass or ceramic and the main copper traces. This layer also functions as a diffusion barrier to prevent the migration of metals into the substrate.
Deposition Process
Physical vapor deposition in a vacuum chamber is typically used to apply this film at a thickness of only a few hundred angstroms. Once the titanium seed layer is in place, a second layer of copper is often added before the board moves to the main plating line. The quality of the vacuum and the purity of the titanium target are necessary for achieving a uniform and pinhole-free coating.
If this layer is too thin, it may not provide enough conductivity for even plating, while a layer that is too thick can be difficult to remove during the final etch.
Final Removal
After the circuit patterns are plated, the exposed areas of the titanium seed layer must be chemically removed to prevent short circuits. Choosing an etchant that targets titanium without damaging the copper traces is the final requirement in the sequence.