Low-Cost Thermal Solution for High-Power GaN Converters – Eval Board

The GSP665x-EVBIMS2 from GaN Systems is a horizontal Insulated Metal Substrate (IMS) evaluation platform that can be used to evaluate the electrical and thermal performance benefits of GaNPX® bottom-side cooled gallium-nitride E-HEMTs in high-power applications.

The optimized thermal and electrical designs provide a reference for implementing a low-cost, high-performance design. Using this platform, power designers can evaluate the performance of GaN Systems’ E-HEMTs (Enhancement mode High Electron Mobility Transistors) in high power, high efficiency applications.

The IMS 2 half-bridge power board is populated with GaN Systems’ GS66516B (bottom-side cooled E-HEMT, rated at 650V / 25mΩ) or GS66508B (bottom-side cooled E-HEMT, rated at 650V / 50mΩ). The embedded GaNPX® SMD package has the following features:

  • Large power source/thermal pad for improved thermal dissipation.
  • Bottom-side cooled packaging for conventional PCB or advanced IMS/Cu inlay thermal design.
  • Ultra-low inductance for high frequency switching.

The following measures are taken to optimize the design of this evaluation platform:

  • The IMS 2 evaluation platform is implemented as a two-board asssembly. The gate drive circuitry is assembled on the GSP665HPMB-EVBIMS2, a multi-layer FR4 PCB mother board. This includes the gate driver ICs, an isolated push-pull power supply to power the driver IC, and dc decoupling capacitors. The GaN E-HEMTs are mounted to the IMS half bridge board (GSP66508HB-EVBIMS2 and GSP66516B-EVBIMS2). This approach addresses the shortcomings of implementing the design on a single layer IMS board.
  • While a large copper area is preferred to maximize heat spreading and handle high current, the area of copper at the switching node (high dv/dt) needs to be minimized to reduce the parasitic coupling capacitance to the metal substrate. An IMS board with thicker dielectric layer (100um) is chosen on this design to further reduce this effect.

Performance comparison of 3 thermal design options for SMT power devices (click on table to enlarge)

Comparison of Junction to Heatsink thermal resistance (RthJ-HS) (Estimated based on GS66516B)

The IMS 2 half-bridge power board is designed for users to gain hands-on experience in the following ways:

  • Evaluate the GaN E-HEMT performance in any half-bridge-based topology, over a range of operating conditions. This can be done using either the accompanying power motherboard (P/N: GSP665HPMB-EVBIMS2) or with the users’ own board for in-system prototyping.
  • Use as a thermal and electrical design reference of the GS66516B or GS66508B GaNPX® package in demanding high-power applications.

IMS 2 EVB board and IMS 2 half-bridge power module with heatsink.

Features and Benefits

  • Enhanced thermal and mechanical design
  • Ultra low inductance, bottom-cooled GaNPX® package
  • Minimizing parasitic elements of the power and gate drive loops via magnetic flux-cancellation
  • High performance switching with low EMI
  • Scalable and parallelable GaNPX® packaging for applications up to 100kW
  • Low cost thermal solution for high power applications.
GaN Systems Inc.
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