Semiconductor Package Thermal Impedance Extraction for Modelica Thermal Network Simulation Combined with VHDL-AMS model

Abstract

Because of the emerging market demand for higher power with higher efficiency for the power semiconductor devices, thermal design of the semiconductor package and its cooling method has become one of the key elements for the power supply systems in power electric design. Thus, many thermal designers now require the junction-to-case thermal Impedance ZθJC since it is one of the most important thermal characteristics of semiconductor devices and thus, in November 2010, the more reliable and sufficiently reproducible measurement method without a case temperature measurement has been standardized by JEDEC as JESD 51-14 (https://www.jedec.org/standardsdocuments/docs/jesd51-14-0) This paper shows the new feature in ANSYS simulation tool, ANSYS Electronics Desktop, which extracts ZθJC from JESD 51-14 compliant measurement data. The extracted ZθJC , or its cumulative expression of thermal resistance ∑ (Rthi) n i=1 and capacitance∑ (Cthi) n i=1 called “structure function”, is transformed to the Modelica thermal ladder network model. This Modelica model was simulated by ANSYS TwinBuilder, Multi-domain system simulator, and the junction temperature is reproduced by this simulation, that agreed well with the original measured temperature data. Further, ZθJC is split into two components, Junction-to-Die part(IC package DUT) and Heat-sink part(cold plate) in accordance with the guideline of Transient Dual Interface Measurement Procedure principle described in JESD 51-14. Then, ZθJC corresponding to IC package structure part is transformed to the VHDL-AMS model ( as IC Package thermal compact model ) while Heat-sink structure part is transformed to Modelica model(as testing fixture structure model) . Those models built by two wellknown physical model description languages were connected with the acausal (i.e., conservative) condition in ANSYS TwinBuilder and the thermal response of the combined model is evaluated. The result of the simulation matches to the full Junction-to-Heat-sink Modelica thermal ladder network model, that ensures Modelica and VHDL-AMS models can be connected in a single physical multi-domain system simulation environment in ANSYS TwinBuilder under the energy conservative principle, that might expand the potential applicability and the coverage for Modelica simulation for the broader application area. Please send an email to eiji.nakamoto@ansys.com if there are any questions or suggestions regarding this paper.