High Density Interconnect, or HDI, circuit boards are printed circuit boards with a higher wiring density per unit area than traditional printed circuit boards (PCB). In general, HDI PCBs are defined as PCBs with one or all of the following: microtraces, VIP (Via In Pad), microvias, blind vias, buried vias or other microvia technique, built-up laminations and high signal performance considerations.
Placement Feasibility – SMT Parts will not fit with room for pin escapes to PTH vias, so use VIP via in pad.
High Speed or RF performance – unwanted parasitics or excess inductance from standard PTH vias
Requirement for thin PCBs in some market spaces.
Back to back large active BGA’s on both sides of PCB.
RF on Primary Side / Digital on Secondary side
Upcoming manufacturing process development will allow circuits to be designed with lines and spaces in the range of 1-2 mil (25-50uM) with strict impedance control
mSAP – Modified Semi-Additive Process
With mSAP, a much thinner copper layer is coated onto the laminate, and plated in the areas where the resist is not applied thus, the “additive” nature of the process. The thin copper remaining in the spaces between conductors is then etched away. Whereas trace geometries are chemically defined during subtractive processes, mSAP allows trace geometries to be defined via photolithography.
SAP – Semi-Additive Process
Although the semi-additive process (SAP) used in the IC substrate board can realize more precise circuit fabrication, but there is a problem that the manufacturing cost is high and the production scale is small, thus restricted to ICs as of today
|Monthy Capability||3900 m²/month|
|Finished board thickness||2m|
|Min Trace Width/Space||3.5mil|
|Min hole size||0.2mm|
|Min copper in hole thickness||1oz|
|Outer layer Finished copper thickness||1.5oz|
|Inner layer base copper thickness||1oz|
|Impedance Control Tolerance||±10%|