Tin-Based Bonding Member for Semiconductor Thermal Stress Management
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Solution Overview
Problem
Semiconductor devices with stress relieving members for heat dissipation face issues with lower heat transfer rates and metal fatigue due to thermal expansion coefficient differences, leading to unsatisfactory heat dissipation and reliability.
Innovation Solution
A semiconductor device configuration using an insulating substrate with conductive plates, a semiconductor chip, and a cooler, where the bonding between the substrate and a plate member, and the plate member and cooler, is performed using a tin-based bonding member with a cyclic stress lower than the bonding member's tensile strength, ensuring efficient heat transfer and reduced metal fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stress relieving member with stress accommodating spaces is used between the insulating substrate and the cooler, then thermal stress is relieved, but heat transfer properties deteriorate due to low heat-transfer rate of air in stress accommodating spaces
Solution Approach 1:
The patent changes the material parameter of the stress relieving member from conventional materials with air-filled stress accommodating spaces to a rubber-like material with elastomeric properties. This material parameter change enables the stress relieving member to achieve both stress relief through elastic deformation and satisfactory heat transfer properties, as rubber-like materials have higher thermal conductivity than air while maintaining elastomeric characteristics for stress accommodation.
Solution Approach 2:
The patent employs a composite material approach by using a rubber-like material that combines the properties of elastomeric stress accommodation with thermal conduction capabilities. This composite material integrates the functions of stress relief and heat transfer in a single component, resolving the contradiction between thermal stress resistance and heat transfer rate.
2Reliability
If the thickness of the stress relieving member is increased to not less than 1 mm and not more than 4 mm for adequate stress relief, then stress accommodation is improved, but heat flow spread is insufficient due to obstruction by stress accommodating spaces
Solution Approach 1:
The patent changes the structural parameter of the stress relieving member by eliminating internal stress accommodating spaces and instead using the continuous elastomeric matrix itself for stress relief. This parameter change allows heat flow to spread effectively through the entire thickness of the member (1-4 mm) without being obstructed by air-filled spaces, while still achieving adequate stress relief through the inherent elasticity of the rubber-like material.
3Strength
If a bonding member with high tensile strength is used to withstand thermal stress, then bonding strength is improved, but manufacturing complexity increases due to high bonding temperature requirements
Solution Approach 1:
The patent changes the material parameter of the bonding member from conventional high-temperature bonding materials to a tin-based bonding member with a melting point of 232°C or lower. This parameter change enables bonding at lower temperatures (200°C or lower), significantly reducing manufacturing complexity and energy consumption while still achieving sufficient bonding strength through the tin-based material's adhesive properties.
Solution Approach 2:
The patent adopts a tin-based bonding member that can be applied as a thin layer (0.01-0.1 mm) and provides adequate bonding strength at low temperatures. This approach uses a simpler, lower-cost bonding material that sacrifices some high-temperature strength compared to conventional bonding materials but compensates through adequate low-temperature bonding performance and ease of application.
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 configuration maintains satisfactory heat transfer properties while reducing metal fatigue and improving the reliability of the semiconductor device by managing thermal stress, ensuring effective heat dissipation and prolonged device lifespan.
Implementation Method 1
at least one of bonding between the lower surface of the insulating substrate and the plate member and bonding between the lower surface of the plate member and the cooler is performed via a bonding member which is composed mainly of tin
Implementation Method 2
a cyclic stress of the plate member is smaller than a tensile strength of the bonding member
Implementation Method 3
an average heat-transfer rate of a stress relieving member is lower than an average heat-transfer rate of a base member
Data Source
AI summary
A semiconductor device and a method for manufacturing the semiconductor device. The semiconductor device includes an insulating substrate, a semiconductor chip, a plate member, and a cooler. The insulating substrate includes insulating ceramics serving as an insulating plate, and conductive plates provided on opposite surfaces of the insulating ceramics. The semiconductor chip is provided on an upper surface of the insulating substrate. The plate member is bonded to a lower surface of the insulating substrate. The cooler is bonded to a lower surface of the plate member. At least one of bonding between a lower surface of the insulating substrate and the plate member and bonding between a lower surface of the plate member and the cooler is performed via a bonding member composed mainly of tin. Also, a cyclic stress of the plate member is smaller than a tensile strength of the bonding member.