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Terminal coated with a Noble material in a power-electronics module optimized for ultrasonic welding

IP.com Disclosure Number: IPCOM000241414D
Publication Date: 2015-Apr-24
Document File: 3 page(s) / 85K

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The IP.com Prior Art Database

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David Guillon: AUTHOR

Abstract

The layout from the bottom foot of terminal within a power semiconductor module is decribed. In state-of-the-art power electronics (PE) modules (e.g. ABB’s HiPak IGBT modules), the electrical terminals as well as other components are ultrasonic welded onto a metalized ceramics substrate. During the ultrasonic welding process normal and shear forces act on the parts to be welded, at the welding interface and at the substrate ceramic. After etching the metallization away to investigate the quality of the substrate material, conchoidal cracks have been identified directly below the welding spot since ceramic are brittle materials. The disclosure provides a solution to reduce the stress undergoes by the ceramic substrate within the ultrasonic welding process. The method is based on using a coating material with low friction coefficient inducing a smooth rising of the temperature within the welding interface, furthermore the coating material should have a high diffusion coefficient into copper material in order that the ultrasonic energy is absorbed within the welding interface and not directly transfer to the ceramic.

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24.04.2015

CH-1505101

Terminal coated with a Noble material in a power-electronics module optimized for ultrasonic welding

Author: D. Guillon

TECHNICAL FIELD

The present disclosure describes the layout from the bottom foot of terminal within a power semiconductor module.

BACKGROUND OF THE DISCLOSURE

In state-of-the-art power electronics (PE) modules (e.g. ABB's HiPak IGBT modules), the electrical terminals as well as other components are ultrasonic welded onto a metalized ceramics substrate. During the ultrasonic welding process normal and shear forces act on the parts to be welded, at the welding interface and at the substrate ceramic. After etching the metallization away to investigate the quality of the substrate material, conchoidal cracks have been identified directly below the welding spot since ceramic are brittle materials. The ultrasonic metal welding process imposes high stresses into ceramic substrates which can lead to cracks in the ceramic, in particular in AlN.

SUMMARY

The disclosure provides a solution to reduce the stress undergoes by the ceramic substrate within the ultrasonic welding process. The method is based on using a coating material with low friction coefficient inducing a smooth rising of the temperature within the welding interface, furthermore the coating material should have a high diffusion coefficient into copper material in order that the ultrasonic energy is absorbed within the welding interface and not directly transfer to the ceramic.

DETAILED DESCRIPTION OF EMBODIMENTS

Experimentally it has been demonstrated that when welding (Ultrasonic welding) a copper work piece (e.g. a terminal) to a copper metallization of an AlN substrate (e.g. DAB or Copper substrate metallization), an additional silver or gold layer on top of the metallization of the substrate or either on the bottom side of the terminal foot reduces the risk of substrate crackin...