Power Module Terminal Attachment With Buffer Structure Welding

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Solution Overview

Problem

Conventional methods for attaching terminals to insulated metal substrates in semiconductor power modules face challenges with reliability, especially at high voltage applications, due to mechanical and thermal stress during ultrasonic welding, which can lead to resin deformation, cracking, and delamination.

Innovation Solution

A method involving a buffer structure element with a protrusion on the metal top layer, which absorbs mechanical and thermal stress, and is ultrasonically welded to the terminal, reducing the impact on the resin layer and ensuring a stable connection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ultrasonic welding is used to attach terminals to the metal top layer, then connection reliability is improved, but mechanical stress damages the isolating resin layer

Engineering Contradiction:

Improveconnection reliabilityVSAvoidmechanical stress damage to resin layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A buffer structure element is introduced as an intermediary component between the terminal and the metal top layer. This buffer element absorbs and distributes the mechanical stress generated during ultrasonic welding, preventing direct transmission of stress to the isolating resin layer while maintaining reliable electrical connection through the buffer element to the terminal.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer structure element is pre-installed on the metal top layer before terminal attachment. This beforehand cushioning structure is designed to absorb and mitigate the mechanical impact and thermal stress that will be generated during the subsequent ultrasonic welding process, protecting the resin layer from damage before the stress even occurs.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Productivity

If ultrasonic welding is applied directly to the metal substrate, then manufacturing efficiency is improved, but thermal stress causes resin deformation and cracking

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidthermal stress deformation

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The buffer structure element serves as a thermal mediator between the ultrasonic welding heat source and the isolating resin layer. It absorbs and dissipates thermal stress during the welding process, preventing thermal deformation and cracking of the resin layer while allowing the efficient ultrasonic welding process to continue.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer structure element is positioned in advance to provide thermal cushioning during ultrasonic welding. It prepares the thermal pathway to absorb and distribute heat stress before it can reach the resin layer, enabling the welding process to proceed without causing thermal damage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If terminal attachment is performed without buffer structure, then device complexity is reduced, but connection stability under thermal load cycles deteriorates

Engineering Contradiction:

Improvestructure complexityVSAvoidconnection stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The buffer structure element acts as a stress-absorbing intermediary that improves connection stability during thermal load cycles. It compensates for thermal expansion differences and mechanical stress between the terminal and substrate, maintaining reliable electrical connection despite temperature variations and mechanical loading.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method enables reliable and cost-effective attachment of terminals to insulated metal substrates, enhancing the semiconductor power module's stability and durability for high voltage applications while minimizing damage to the resin layer.

Implementation Method 1

coupling the at least one terminal to the buffer structure element by means of ultrasonic welding with an ultrasonic welding head

Methodology Applied

Scientific EffectUltrasonic welding: Ultrasonic Vibration

Implementation Method 2

ultrasonic welding provides a reliability of ultrasonic welding interface towards thermal load cycles

Methodology Applied

Scientific EffectFriction heating: Friction

Data Source

PatentEP4239660A1Method of attaching a terminal to a metal substrate structure for a semiconductor power module and semiconductor power module

Publication Date: 2023.09.06 HITACHI ENERGY LTD

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AI summary

A method for attaching a terminal (4) to a metal substrate structure (3) for a semiconductor power module (10) comprises providing at least one terminal (4) and providing the metal substrate structure (3) with a metal top layer (17), a metal bottom layer (19) and an isolating resin layer (18) arranged between the metal top layer (17) and the metal bottom layer (19). The method further comprises providing and coupling a buffer structure element (7) to a top surface (171) of the metal top layer (17) to form a protrusion for the at least one terminal (4). The method further comprises coupling the at least one terminal (4) to the buffer structure element (7) by means of ultrasonic welding such that the buffer structure element (7) is arranged between the metal top layer (17) and the at least one terminal (4) and is materially bonded to the at least one terminal (4).