Selecting Tooling Shields for Thermal Protection during Selective Soldering Cycles
Selecting selective soldering tooling shields requires matching composite thermal resistivity against component clearance gaps to guarantee zero thermal damage.
Thermal Conductivity
Material Heat-Transfer
Heat-transfer rate per unit cross-sectional area per unit temperature gradient defines how thermal conductivity behaves within a solid substance. Designers select materials for printed circuit board substrates based on this property to manage the movement of energy away from integrated circuits. Dielectric layers transmit heat from copper traces into the core or heat sink assemblies.
Values for thermal conductivity typically appear in units of watts per meter-kelvin and define the efficiency with which a substrate dissipates energy generated by surface components.
Substrate Thermal-Performance
Resin systems and glass-fibre reinforcements contribute to the total heat-conducting capacity of a base laminate. High-density designs generate local temperatures that exceed the threshold of standard epoxy materials. Engineers use thermal conductivity to predict the junction temperature of power transistors during continuous operation.
Calculating this property allows for the simulation of cooling paths through vias and internal copper planes. Insufficient conduction results in premature degradation of the dielectric material or the catastrophic failure of soldered joints during active duty.
Measurement Standardisation
Testing methods for this property involve placing a sample between a known heat source and a heat sink while monitoring steady-state temperature differences across the thickness of the material. Variations in fiber orientation or resin loading affect the bulk value. Production quality control relies on data sheets provided by laminate manufacturers to ensure the material meets design requirements for heat removal.
Standard protocols require accurate contact pressure to eliminate air gaps that interfere with accurate measurements. Consistent performance of the finished circuit board depends on the stability of these material properties under fluctuating environmental conditions.