Microelectronics Reliability 148 (2023) 115162 Available online 12 August 2023 0026-2714/© 2023 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Microelectronics Reliability journal homepage: www.elsevier.com/locate/microrel TIMs for transfer molded power modules: Characterization, reliability, and modeling Alessandro Sitta a,∗ , Giuseppe Mauromicale a , Giuseppe Luigi Malgioglio a , Davide Maria Amoroso a,b , Biagio Schifano b , Michele Calabretta a , Gaetano Sequenzia b a Automotive and Discrete Group, R&D, STMicroelectronics, Stradale Primosole 50, Catania, 95121, Italy b University of Catania, Viale Andrea Doria 6, Catania, 95125, Italy ARTICLE INFO Keywords: Thermal interface material Power cycle Thermal simulation Power packages ABSTRACT This work presents an integrated experimental–numerical method to characterize, model, and experimentally study the properties of transfer molded power modules, considering two different thermal interface materials (TIMs). More specifically, a thermal grease and a phase change material are considered. The aim is to select the most reliable solution by making analytical characterization and power cycling tests on the modules equipped with the two kinds of TIMs. Then, further reliability study is accomplished, in order to estimate the lifetime of the power module equipped with the best TIM, that is the phase change one. Finally, a finite-element numerical model is developed and correlated with experimental data. 1. Introduction Energy consumption is one of the leading players in the world scenario. The need to reduce consumption and emissions has enabled the development of power electronic devices such as power modules, which use semiconductors to convert and control electrical energy [1, 2]. In this context, power modules can embed different chips in smaller area than discrete packages, creating the desired electric topology with optimized parasitic inductive elements and higher converter’s efficiency [3]. In addition, power density increases and, consequently, more ther- momechanical stress is generated. In this framework, reliability is of paramount importance for evaluating the performance of a power mod- ule [4–6]. Dedicated processes, like silver sintering, have developed in order to fulfill extreme reliability requests [7–10]. Various tests are needed to estimate the lifetime of the device during its mission profile and thus to predict when the device might fail according to different possible mechanisms. One key aspect is the study of the stress generated on power module interconnections by cyclic temperature swings [11]. This condition is particularly crucial in the thermal management of electronics [12], as excessive thermal resistances between junction and environment can cause high temperatures that can adversely affect performance and reliability of the power devices [13,14]. The power cycle (PC) test is related to the study of the reliability of the interconnections, by accelerated stress conditions. The aim of this experiment is to mimic ∗ Corresponding author. E-mail address: alessandro.sitta@st.com (A. Sitta). the thermal fatigue of module’s interfaces generated by temperature swing that occur during typical operations. According to AQG 324 guideline [15], there exist PC SEC and PC MIN , depending on the on time (  ) considered for the conduction. PC SEC involves the chip-near interconnections, such as die attach, while PC MIN is related also to the chip-remote interconnections. Modeling can support the temperature analysis during operations [16–18]. One important condition is related to the thermal interface material (TIM). The TIM is placed between two mated surfaces of components not attached with each other, e.g., module and its cooler. It serves to reduce gaps, increasing the effective contact area and thermal con- ductance at the interface. TIMs are used in transfer molded modules, that are gaining attention in high power applications. In this context, ACEPACK™ Surface Mounted Isolated Top-Side Cooled Package (SMIT), represented in Fig. 1, is the test vehicle chosen in this study [19,20]. It is made up by automotive grade silicon (Si) MOSFETs, based on super junction MDMesh technology [21]. This module encompasses different possible types of implementable topologies: in this paper the devices form a half bridge structure. The package is a top side cooling, with a leadframe and a kelvin source pin. Moreover, it has a direct bond copper substrate. ACEPACK™ SMIT is suitable for industrial and automotive applications, such as on-board chargers. This work compares power cycle performance of a power module mounted on cooler using two different TIMs. The paper is organized in the following way. In the next section, an overview of the TIM in power https://doi.org/10.1016/j.microrel.2023.115162 Received 2 June 2023; Received in revised form 17 July 2023; Accepted 25 July 2023