Multistage Buildup
Sequential fabrication operations combining multiple lamination and drilling stages enable the production of complex high-density interconnect circuit boards. Advanced board architectures require blind microvias and buried via structures that cannot be formed in a single pressing cycle. Executing sequential subassembly lamination builds inner core subassemblies with completed via structures before adding outer prepreg and foil layers.
The process scope encompasses multilayer press operations and intermediate drill steps, excluding single-pass rigid board fabrication.
Buildup Integration
Subassembly cores undergo independent photo-imaging, etching, drilling and plating cycles to establish inner-layer interconnections before sub-laminates are stacked together. Subsequent lamination passes join processed subassemblies using thin prepreg sheets, creating complex microvia structures that span specific layer sets. Utilizing sequential subassembly lamination allows board designers to place buried vias across internal layers without consuming routing space on outer signal layers.
Registration accuracy across multiple pressing cycles requires precise optical alignment systems to compensate for cumulative dimensional movements of sub-laminates. Thermal history accumulates with each lamination pass, requiring substrate materials capable of enduring multiple press thermal cycles without resin degradation. High-density designs for mobile and aerospace platforms rely on this multi-pass approach to maximize interconnection density within thin form factors.
Yield Loss Accumulation
Scrap rates increase with each lamination stage because defects introduced late in processing destroy previously completed subassemblies. Strict process controls and intermediate electrical testing catch defects prior to final outer-layer lamination. Managing dimensional movement across lamination cycles maintains pad-to-via registration.
