Experimental characterization and modeling of power module warpage during assembly process
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SHORT ORIGINAL PAPER
Experimental characterization and modeling of power module warpage during assembly process Michele Calabretta1
· Alessandro Sitta1,2
· Salvatore Massimo Oliveri2
· Gaetano Sequenzia2
Received: 11 March 2020 / Accepted: 6 October 2020 © Springer-Verlag France SAS, part of Springer Nature 2020
Abstract Hybrid and full electric automotive market is strongly increasing the demand for power semiconductor modules. With respect to discrete packages, manufacturing of power modules is more complex and new process parameter, such as module deformation (warpage), assumes a key role for a robust design and to guarantee reliable application. The aim of this paper is to study the warpage behaviour during power module assembly flow by means of dedicated warpage measurement at different process steps. Once highlighted the most impacting process for warpage, a finite element model has been developed to reproduce phenomenology, predicting the induced deformation. Keywords Power module · Warpage measurement · Planarity · Finite element modeling · Manufacturability
1 Introduction Power semiconductor modules have several uses in Power Electronics such as controlling electric motors in automotive applications, in which the overall efficiency and reliability play a crucial role. Therefore, package performance is fundamental to achieve the required standards for automotive applications. A key aspect is the planarity of power modules, both during the assembly process and at final level. Too high deformed module represents a severe issue for manufacturability, making critical some productive steps, such as the ultrasonic welding of power terminals [3]. Furthermore, considering power modules have to be mounted on a cooling system, too high warpage values make the contact between module and cooling system too irregular, limiting the whole hydraulic sealing performances. Warpage represents also a limitation for Bond Line Thickness Uniformity and consequently a thermal resistance and reliability bottle neck. Warpage assumes a central role also for the connection between module and its driving printed circuit board (PCB): excessive module warpage implies reliability issue at board level. Power modules warpage is unavoidable due to the mis-
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Michele Calabretta [email protected]
1
STMicroelectronics, Catania, Italy
2
Dipartimento di Ingegneria Elettrica, Elettronica e Informatica, Università degli Studi di Catania, Catania, Italy
match of materials and due to the asymmetric structure in almost every packaging process. An important component is the ceramic substrates that are made by two metal (typically copper) layers, separated by an insulating ceramic layer. They work as mechanical supports for the dies and the passive components of Power Module Packages, on which electronic devices are soldered and/or sintered [1]. In addition, the substrate’s top metal layer is routed to constitute the circuitry for power module, while substrate helps the dissipation of heat, which is normally generated during the ap
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