Variable-Height Sealing Structure for Crack-Resistant Power Semiconductors

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Solution Overview

Problem

The semiconductor device experiences reliability issues due to cracks in the bonding members between semiconductor chips and lead frames or wiring boards, leading to increased thermal resistance and reduced heat dissipation, which deteriorates the device's performance and lifespan.

Innovation Solution

A semiconductor device design featuring a cooling body with a top plate, semiconductor units, and a sealing member that includes a first portion sealing the main electrode with a smaller thickness than a second portion surrounding the wiring portion, minimizing stress and preventing cracks by maintaining consistent thermal expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a uniform sealing member thickness is used, then manufacturing is simpler, but stress concentration occurs at bonding members leading to cracks

Engineering Contradiction:

Improvesealing member fabricationVSAvoidbonding member integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The sealing member is designed with varying thickness: a first thickness in regions adjacent to bonding members and a second thickness in other regions. This local differentiation reduces stress concentration at bonding interfaces while maintaining manufacturing feasibility through molded construction.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The sealing member's thickness parameter is changed from uniform to non-uniform, with specific thickness values assigned to different regions based on their functional requirements, particularly reducing thickness near bonding members to minimize thermal expansion stress.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If sealing member thickness is reduced near bonding members, then stress and crack risk are reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvecrack preventionVSAvoidsealing member thickness control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The sealing member is segmented into distinct thickness regions: a first thickness region adjacent to bonding members and a second thickness region in other areas. This segmentation allows optimized stress distribution while maintaining manufacturability through injection molding techniques.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sealing member design transitions from a two-dimensional uniform thickness to a three-dimensional variable thickness profile, creating a graded structure that naturally distributes stress while remaining compatible with standard molding processes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Productivity

If bonding members are used to connect semiconductor chips, then electrical connection is achieved, but thermal resistance increases due to cracks

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidbonding member durability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The sealing member is designed with reduced thickness adjacent to bonding members before thermal cycling occurs, creating a stress-absorbing configuration that prevents crack formation during subsequent thermal expansion and contraction, thereby maintaining bonding integrity and heat dissipation.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The sealing member uses a composite structure with varying thickness regions, combining the benefits of stress reduction near bonding members with adequate sealing thickness in other areas, optimizing both reliability and thermal performance.

Inventive Principle:

Principle #40Composite materials

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

The design enhances the reliability and longevity of the semiconductor device by reducing thermal resistance and maintaining effective heat dissipation through controlled thermal expansion, thereby improving the device's operational stability.

Implementation Method 1

a crack may appear in the bonding member on the front surface or the back surface of a semiconductor chip due to the difference in linear expansion coefficient between the members

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

A refrigerant flows inside the cooler. By doing so, the cooler cools the semiconductor module which generates heat

Methodology Applied

Scientific EffectHeat dissipation: Convection

Data Source

PatentUS12538834B2Semiconductor device with sealing surfaces of different height and semiconductor device manufacturing method

Publication Date: 2026.01.27 FUJI ELECTRIC CO LTD

AI summary

A semiconductor device, including a cooling body, a semiconductor unit including a wiring portion electrically connected to a semiconductor chip, and a sealing member sealing the entire semiconductor unit over a cooling surface of the cooling body. The sealing member includes a first portion and a second portion which surrounds the first portion in a plan view. The first portion seals a central portion of a main electrode of the semiconductor chip, and has a first sealing surface opposite the cooling surface of the cooling body. The second portion seals a wiring portion to thereby surround the first portion in the plan view, and has a second sealing surface opposite the cooling surface. A distance in a thickness direction of the semiconductor device from the cooling surface to the first sealing surface, is smaller than a distance in the thickness direction from the cooling surface to the second sealing surface.