Fabrication Architecture
Multi-stage lamination processes enable the creation of high-density interconnect structures by adding dielectric and conductive layers in repeated cycles. Utilizing a sequential build up stackup allows for the integration of microvias that connect only specific layers rather than passing through the entire board thickness. The method is standard for mobile devices and high-performance computing modules where space is at a premium.
Layer Connection
Every lamination cycle involves bonding a new layer of resin-coated copper or prepreg and foil to the existing core. The sequential build up stackup process repeats the drilling and plating steps to create complex vertical paths for electrical signals. High precision registration is required to ensure that the small laser-drilled holes land accurately on the pads of the underlying layer.
Production Complexity
Increased manufacturing time and cost are the trade-offs for achieving higher circuit density. A sequential build up stackup requires multiple passes through the etch and plating lines which increases the risk of cumulative defects. Managing the thermal history of the board is vital because each lamination cycle subjects the previous layers to heat and pressure.
Advanced shops use automated registration systems to maintain the alignment of the layers throughout the long fabrication sequence. Yield rates are sensitive to the number of cycles and the thickness of the dielectric materials used.
