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COPPER based PACKaging for direct cooled power module – COPPERPACK

COPPERPACK

Copper based power module packaging

Goals

COPPERPACK project aims at opening the way to competitive power electronics converters with a new class of power modules. The modules will be double side cooled and will present high electrical and thermal performance and high reliability. COPPERPACK project will contribute to validate and push our concept from Technology Readiness Level (TRL) 2 up to a TRL 3-4 with a functional technological demonstrator. In order to reach the application related objectives, the partners are aware that understanding of the physical mechanisms taking place in each building brick is mandatory.

In order to realize high performances power modules using SiC wide band gap devices, technological breakthroughs should be achieved by addressing three main targets:
1. Synthesis of nanoporous Cu films, either freestanding or directly deposited on substrate with controlled microstructure,
2. Thermocompression of the nanoporous Cu films at low pressure using conventional heating or fast heating in order to limit oxidation issues,
3. Deposition of thick Cu layers (several hundreds of µm) or bulk materials with complex shapes and, small and monitored dimensions on metallized substrates.

Nanoporous copper rubans with several tens on µm thick, an homogenous microstructure and an adjustable porosity have been successfully achieved. The porosity can be monitored by the alloy composition and the dealloying time and temperature. The ligaments size between 50 and 100 nm and pores of hundreds of nm are obtained at the initial state after dealloying. These values can be monitored by adjusting the electrolyte bath temperature or by achieving a thermal heat treatment after dealloying.

The electrodeposition of thick porous copper Cu using the Dynamic Hydrogen Bubble Template (DHBT) approach has allowed to demonstrate the feasability of nanoporous structure with monitored pores and ligaments dimensions. The results show that this techique may allow the realisation of porous film able to be used as die attach with a thermocompression process as well as metal foams that can be used for hybrid electroformed heat sinks.

Thermocompression of nanoporous copper films achieved using various technologies ( spin melting followed by dealloying, Dynamic Hydrogen Bubble Template...)
Design and evaluation of hybrid heat sinks (using porous and bulk copper) deposited using electroforming technique directly on the metallised substrate.
Design and evaluation of power modules based on the thermocompression of nanoporous copper films for die attach and the electrofromed heat sinks.

Scientific publications
1. J. SCHOENLEBER, M-P. GIGANDET, B. FEDI, J-Y. HIHN “Porous Copper Electroforming by Dynamic Hydrogen Bubble Template Using Continuous and Pulse Currents” acceptée à l’ECS 240th Orlando USA.
2. L. CHACHAY, J.M. MISSIAEN, D. BOUVARD, R. DAUDIN, « Fabrication de rubans de cuivre nanoporeux par dissolution sélective d’alliages Cu-Mn : application à l'assemblage par thermocompression»,

The market introduction of high temperature wide bandgap power semiconductor devices with junction temperature exceeding 200°C significantly accelerates the trend towards high power density and severe ambient temperature electronics applications. Such evolution may have a great impact in aeronautics applications, especially with the development of More Electric Aircraft (MEA), since it can allow to reduce the mass and volume of power electronics systems. As a consequence, the aircraft operating cost can decrease. However, for electronics used under such harsh conditions, the package reliability and the heat evacuation are very critical issues. The goal of this project is to design and fabricate high performance double sided cooled power electronics modules with optimized thermomechanical properties. The assembly is based on copper joints and a copper heat sink and integrates several technological breakthroughs. Three main technological bricks will be deeply addressed in order to reach the target:
1) Synthesis of nanoporous copper films, either freestanding or directly deposited on metallized substrates with controlled microstructure: In order to limit the risks, three independent strategies will be investigated during the project: the synthesis of nanoporous copper free standing films using melt-spinning and chemical dealloying techniques, the direct on-substrate electroforming of copper-alloy followed by anodic dealloying, and the direct growth of nanoporous structures without any additional treatment by tuning electrolyte formulation and plating parameters.
2) Thermocompression of the nanoporous copper films for die attach: Conventional heating will be achieved at low pressure and in inert/reductive atmosphere. An alternative method based on laser induced fast heating will also be evaluated to thermocompress the nanoporous copper in air. Both solutions allow to limit the oxidation copper issues. The underlying physical mechanisms taking place during the thermocompression of the various morphologies and microstructures of nanoporous copper films will be in-depth investigated. The joint stability under electro-thermo-mechanical aging conditions will be evaluated.
3) Deposition of thick copper layers for substrate/heatsink assembly using electroforming process: A thick dense metal layer will be deposited on a designed sacrificial polymer preform allowing to create a wide range of complex shapes directly on the metallized substrate with low residual stresses. This technology combined to virtual prototyping will allow us to fabricate high performance heat sink patterns (liquid forced convection without phase change) in terms of high local heat transfer coefficient and low pressure drop. The thermal-hydraulic performances of the heat sinks will be analyzed with an experimental setup. The robustness of the assembly (substrate/heat-sink) under repetitive temperature variations will be also evaluated.
Silicon Carbide (SiC) devices based power modules (inverter phase leg) using the aforementioned technological bricks will be realized and evaluated in the project. Electrical, thermal and robustness tests are planned to estimate the module performances. The COPPERPACK project will contribute to validate and push our concept from Technology Readiness Level (TRL) 2 up to a TRL 3-4 with a functional technological demonstrator.

Project coordination

Rabih KHAZAKA (SAFRAN)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

SAFRAN
G2Elab Laboratoire de Génie Electrique de Grenoble
Grenoble INP / SIMAP Institut polytechnique de Grenoble
INSTITUT UTINAM UNIVERS, TEMPS-FREQUENCE, INTERFACES, NANOSTRUCTURES, ATMOSPHÈRE ET ENVIRONNEMENT, MOLÉCULES

Help of the ANR 593,745 euros
Beginning and duration of the scientific project: December 2019 - 48 Months

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