Segmented Copper Strap Packaging for Power Semiconductor Modules

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Solution Overview

Problem

Power semiconductor modules face issues with mechanical stress on chips due to thermal cycling and positioning deviations caused by thick copper frames, leading to potential damage and defective products.

Innovation Solution

The use of copper straps with adjustable positioning and reduced thickness to minimize mechanical stress, combined with laser and ultrasonic welding for connection, allows for improved thermal management and reduced turn-on resistance and parasitic inductance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thick copper frame is used to reduce turn-on resistance and parasitic inductance, then electrical performance is improved, but mechanical stress on the chip increases during thermal cycling

Engineering Contradiction:

Improveelectrical performanceVSAvoidmechanical stress on chip

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The copper frame is segmented into different thickness regions: a first copper frame portion with greater thickness for low electrical resistance, and a second copper frame portion with reduced thickness for lower mechanical stress. This segmentation allows simultaneous optimization of electrical performance and mechanical stress reduction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different portions of the copper frame have different thickness qualities tailored to their specific functions. The first portion (contacting the chip) has reduced thickness locally to minimize stress, while the second portion (external connection) has greater thickness for electrical performance, creating local quality variations that resolve the contradiction.

Inventive Principle:

Principle #3Local quality

2Reliability

If a thick copper frame is used to improve electrical connection, then turn-on resistance is reduced, but positioning precision becomes more difficult to control

Engineering Contradiction:

Improveturn-on resistanceVSAvoidpositioning precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The copper frame is divided into functional segments with different thickness characteristics. The first portion optimized for positioning has reduced thickness for better precision, while the second portion optimized for electrical connection has greater thickness, resolving the positioning precision contradiction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The copper frame design incorporates adjustable positioning structures that can be dynamically configured during assembly. The segmented design allows for flexible positioning adjustment while maintaining electrical performance, enabling dynamic optimization of both positioning precision and electrical connection.

Inventive Principle:

Principle #15Dynamics

3Reliability

If a thick copper frame is used to reduce parasitic inductance, then electrical performance is improved, but the complexity of the positioning process increases

Engineering Contradiction:

Improveparasitic inductanceVSAvoidpositioning process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The segmented copper frame design separates positioning functions from electrical connection functions. The first portion with reduced thickness simplifies positioning, while the second portion maintains electrical performance, thereby reducing overall process complexity despite improved electrical characteristics.

Inventive Principle:

Principle #1Segmentation

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 solution reduces mechanical stress on chips, enhances thermal management, and simplifies the positioning process, resulting in increased product reliability and yield by adjusting copper strap positions and reducing turn-on resistance and parasitic inductance.

Implementation Method 1

Copper has strong conductivity, which can reduce turn-on resistance and parasitic inductance

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

the thermal expansion coefficient of the copper is 16.9×10 -6

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

combined with laser and ultrasonic welding for connection

Methodology Applied

Scientific EffectLaser welding: Laser Beam Welding

Implementation Method 4

combined with laser and ultrasonic welding for connection

Methodology Applied

Scientific EffectUltrasonic welding: Ultrasonic Vibration

Data Source

PatentEP4148778B1Power semiconductor module

Publication Date: 2025.01.01 WUXI LEAPERS SEMICON CO LTD

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AI summary

The present disclosure provides a power semiconductor module, including a metal bottom plate, an insulating heat dissipation material layer, a chip, a binding plate, silica gel, and an outer housing, where the binding plate includes a copper plate and a copper strap. The copper plate is connected to the copper strap through welding, and the binding plate is configured to connect circuits of various components. The metal bottom plate is connected to the insulating heat dissipation material layer through tin soldering, the chip is connected to the insulating heat dissipation material layer through tin soldering, the chip is connected to the copper strap, and the copper strap is connected to the insulating heat dissipation material layer. The present disclosure can resolve the prior-art problem of mechanical stress generated on the chip in the case of a temperature change when a relatively thick copper frame is applied to the packaging of the power semiconductor module.