Using experimental analysis to evaluate the influence of printed circuit board construction on the thermal performance of four package types in both natural and forced convection

As the functionality of electronic systems increase, so does the complexity of Printed Circuit Board (PCB) design, with greater component packing densities requiring additional internal signal, power and ground layers to facilitate interconnection. The extra copper content introduced increases PCB thermal conductivity and heat spreading capability, which can strongly influence component operating temperature. Therefore, this experimental study sought to quantify the impact of PCB construction on component operating temperature and relate this sensitivity to the package design, PCB effective conductivity and convective environment. This was achieved by measuring the steady state thermal performance of four package types (PSO20: heat slug up, PSO20: heat slug down, LFBGA80 and SBGA352) on up to six different, single-component thermal test PCBs in the standard natural and forced convection environments. Test velocities ranged from 0.5 m/s to 5.0 m/s and all test components contained a thermal test die. Measurements of junction temperature and component-PCB surface temperature distributions are both presented for power dissipation levels within the range 0.5 to 6.0 Watts. The study includes the low and high conductivity JEDEC standard, FR4-based test PCBs and typical application boards. As each PCB had a different internal structure and effective thermal conductivity, this study highlights the sensitivity of component operating temperature to the PCB, provides benchmark data for validating numerical models, and helps one assess the applicability of standard junction-to-air thermal resistance (θ_JA and θ_JMA), as well as both junction-to-board (Ψ_JB) and junction-to-top (Ψ_JT) thermal characterisation parameters for design purposes on non-standard PCBs.