400
S. Shi et al.
ultraviolet (UV) blockers, fluorescing agents, colorants, and photosensitizers. Inorganic fillers are sometimes added to the resin system for CTE and stiffness control
of the build-up layers [3].
The conductors are used to establish the electron movement path to fulfill the
electrical design goal. The conductors are located in-between dielectric layers, on
the wall of pin-through holes (PTHs) and via holes. Copper is the single most dominant conductor material in substrate and PWB applications because of its excellent
combination of conductivity, ductility, properties and its processability, and affordability. Other conductors such as gold, nickel, palladium, vanadium, silver, tin, and
conductive adhesives can also find their use in some area of substrate and PWB such
as on exposed pad and in filled vias [3].
The selection of the above material components strongly depends on application
and cost targets. Although the material technical data sheet are readily available from
material suppliers, designing and making a successful substrate and PWB for high
density interconnection applications is often a strenuous job. Raw materials are first
screened through the lenses of application requirements, existing equipment, and cost
targets. The screened material candidates are down-selected through processability
tests, material characterization, and substrate and PWB performance and reliability
tests. These tests are often aided by modeling and simulation.
To facilitate the detail discussion of material considerations for 3D substrate applications, the materials are categorized into substrate and PWB cores, dielectric materials, PTH and via filling materials, solder masks, and surface finishes. The proper
integration of these materials yields all kinds of thick core, thin core, and core-less
substrates as well as rigid, flexible, and rigid-flex PWBs.
14.3.2 General Considerations
Substrate material selection is primarily driven by performance and cost considerations. The substrate cost is mainly determined by the cost of base material cost and
substrate manufacturability—the total number of process steps involved in manufacturing the substrate. The substrate manufacturability is not only impacted by the
intrinsic difficulty level and the number of process steps of processing base materials and yield, but also by the existing equipment capability. Adding new manufacturing capability can trigger major capital investments and results in higher cost to a
substrate manufacturer. A detailed discussion of material cost and substrate manufacturability is beyond the scope of this chapter. Readers can refer to microelectronics
packaging handbooks and printed circuits handbooks to get the desired information.
Substrate performance is correlated to the properties of base material and a variety
of interfaces generated during the manufacturing process. Although the property of
an interface is often impacted by the process, it is significantly related to the surface
properties of involved base materials. For a particular application, the thermal, physical, mechanical, and electrical properties of base materials must be considered. In
S. Shi et al.
ultraviolet (UV) blockers, fluorescing agents, colorants, and photosensitizers. Inorganic fillers are sometimes added to the resin system for CTE and stiffness control
of the build-up layers [3].
The conductors are used to establish the electron movement path to fulfill the
electrical design goal. The conductors are located in-between dielectric layers, on
the wall of pin-through holes (PTHs) and via holes. Copper is the single most dominant conductor material in substrate and PWB applications because of its excellent
combination of conductivity, ductility, properties and its processability, and affordability. Other conductors such as gold, nickel, palladium, vanadium, silver, tin, and
conductive adhesives can also find their use in some area of substrate and PWB such
as on exposed pad and in filled vias [3].
The selection of the above material components strongly depends on application
and cost targets. Although the material technical data sheet are readily available from
material suppliers, designing and making a successful substrate and PWB for high
density interconnection applications is often a strenuous job. Raw materials are first
screened through the lenses of application requirements, existing equipment, and cost
targets. The screened material candidates are down-selected through processability
tests, material characterization, and substrate and PWB performance and reliability
tests. These tests are often aided by modeling and simulation.
To facilitate the detail discussion of material considerations for 3D substrate applications, the materials are categorized into substrate and PWB cores, dielectric materials, PTH and via filling materials, solder masks, and surface finishes. The proper
integration of these materials yields all kinds of thick core, thin core, and core-less
substrates as well as rigid, flexible, and rigid-flex PWBs.
14.3.2 General Considerations
Substrate material selection is primarily driven by performance and cost considerations. The substrate cost is mainly determined by the cost of base material cost and
substrate manufacturability—the total number of process steps involved in manufacturing the substrate. The substrate manufacturability is not only impacted by the
intrinsic difficulty level and the number of process steps of processing base materials and yield, but also by the existing equipment capability. Adding new manufacturing capability can trigger major capital investments and results in higher cost to a
substrate manufacturer. A detailed discussion of material cost and substrate manufacturability is beyond the scope of this chapter. Readers can refer to microelectronics
packaging handbooks and printed circuits handbooks to get the desired information.
Substrate performance is correlated to the properties of base material and a variety
of interfaces generated during the manufacturing process. Although the property of
an interface is often impacted by the process, it is significantly related to the surface
properties of involved base materials. For a particular application, the thermal, physical, mechanical, and electrical properties of base materials must be considered. In