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PrintPOWER - Paste systems for multifunctional copper power modules

: Reinhardt, Kathrin; Körner, Stefan; Partsch, Uwe

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Erstellt am: 24.1.2020

Institute of Electrical and Electronics Engineers -IEEE-; International Microelectronics and Packaging Society -IMAPS-:
22nd European Microelectronics and Packaging Conference & Exhibition, EMPC 2019. Technical papers : 16-19 September 2019, Pisa, Italy
Piscataway, NJ: IEEE, 2019
ISBN: 978-1-7281-6291-1
ISBN: 978-0-9568086-6-0 (Originalausgabe)
ISBN: 978-0-9568086-5-3 (Originalausgabe)
European Microelectronics and Packaging Conference & Exhibition (EMPC) <22, 2019, Pisa>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IKTS ()
thick-film power modules; copper multilayer circuits; high temperature pastes; low temperature pastes; rheology; 3D dispensing

Power electronic systems are the backbone of the energy transition and environmentally friendly individual electromobility. Modules in which power semiconductors and other components are integrated form the heart of such systems. Copper thick films combine the advantages of DCB substrates, which are dominant in the module sector, and the silver thick-film technology used for highly reliable signal processing circuits. The focus of the work was the development of copper-compatible paste systems (conductive and dielectric pastes) and their combination to create multilayer module structures on ceramic substrates. The printed modules on the multifunctional substrates should be able to contain, in addition to the power semiconductors, various other active and passive components. This integrated functionality at the module level, let these modules count to the class of the “Intelligent Power Modules” (IPM). In future, the main aim is to develop power modules, which are more compact, functional and cost effective by using the thick-film technology. For this purpose, thick-film pastes were developed at Fraunhofer IKTS, which allow the application of high-current structures with copper layer thicknesses of up to 300 μm as well as filigree multilayer circuits for the production of control and driver circuits. This was to be achieved using novel, multifunctional substrates, which allow a particularly high integration density with simultaneously excellent heat dissipation and high current carrying capacity. The used multifunctional substrates consist of an Al2O3 ceramic plate onto various thick-film pastes were applied by a high-definition printing process (screen, stencil printing, dispensing). This makes it possible, in addition to conductors with a high cross-section, to apply electrically from these insulated areas of fine line conductors and three-dimensional structures. By using copper thick film pastes and adapted insulation pastes for inert firing or curing, several functions can be embedded in the module structure. Furthermore, new contacting options were evaluated via 3D-printed silver polymer suspensions, which could replace established technologies, such as bonding or Siemens Planar Interconnect Technology (SiPLIT), more cost-effectively and with high reliability. As part of these investigations, the following single paste-systems have been developed: Copper thick film pastes for thick print and fine line applications: By varying the composition of copper pastes, in particular with rheological additives, it was possible to specifically set different layer geometries, which enable both thick printing and fine line printing. / Glass insulations for nitrogen atmospheres: Two glasses were evaluated which sinter densely and transparently at temperatures of up to 955 ° C and have only small carbon residues within the layer. This makes it possible to use the developed glass pastes as dielectric layers, but also as covering layers. Furthermore, the development of glass insulation for sintering temperatures ≥ 850 ° C allows a multilayer structure with HT-Cu systems, so that robust circuits can be integrated in several levels. / Silver polymer pastes: For the low temperature range, a silver metallization has been developed, which has very good conducting properties and can be deposited by means of dispensing printing processes. This will allow future use of new 3D contacting options that can replace established technologies such as bonding or the SiPLIT method more cost-effectively and with higher reliability. / Al2O3 polymer insulation: In addition, an Al2O3 polymer insulation was developed, which has good insulation properties and can complete the assembly of a power multilayer module. // To verify the compatibility of the individual developed paste systems, a printed multi-layer module was set up and the layers tested for functionality. It could be shown that the developed paste systems can be combined with each other and can be sintered or hardened under nitrogen atmosphere without suffering a loss of function. Accordingly, it is possible in the future to build application-oriented power modules with the previously developed paste systems.