The dielectric materials used in HDI fabrication are specialized laminates engineered to enable the fine features, withstand the demanding processing conditions required, and deliver stable electrical performance. Typical materials for HDI include:
Polyimides
Polyimides like HD-4000 from Hitachi or Durimide from Rogers offer thermoset polymers with excellent dimensional stability after curing and at higher temperatures. This makes them suited for the repeated lamination cycles in sequential build HDI processing. They have lower loss than traditional FR-4 material.
High Tg Epoxies:
Materials such as Nelco 4000-13SI have high glass transition temperatures above 170°C. This provides good thermal resistance when...
The dielectric materials used in HDI fabrication are specialized laminates engineered to enable the fine features, withstand the demanding processing conditions required, and deliver stable electrical performance. Typical materials for HDI include:
Polyimides
Polyimides like HD-4000 from Hitachi or Durimide from Rogers offer thermoset polymers with excellent dimensional stability after curing and at higher temperatures. This makes them suited for the repeated lamination cycles in sequential build HDI processing. They have lower loss than traditional FR-4 material.
High Tg Epoxies:
Materials such as Nelco 4000-13SI have high glass transition temperatures above 170°C. This provides good thermal resistance when building up successive dielectric layers. These epoxies still absorb more moisture than polyimides though.
PTFE Blends:
Blends of PTFE (polytetrafluoroethylene) and epoxy provide a balance of dimensional stability and low loss performance. Rogers RO4350B is a common example containing a PTFE filler. The PTFE contributes a lower dielectric constant and loss tangent.
Liquid Photoimageable Dielectrics (LPID):
LPIDs like Taiyo PSR-4000 AUS are epoxy based resins that can be screen printed then photocured. They enable fine features with tight alignment between layers, ideal for high density stacking. But they require extra process steps.
Selecting the right materials is key to achieving reliable HDI designs. This includes properly matching material properties and coefficients of thermal expansion between dielectrics, cores, and copper.
