Ceramic Board Terminal Bonding Layout for Thermal Stress Relief
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Solution Overview
Problem
Semiconductor modules face stress-related issues due to thermal expansion and contraction, leading to potential cracks in the ceramic board and increased risk of dielectric breakdown, particularly because the linear expansion coefficient of solder is higher than that of the circuit pattern metal plate, causing concentrated stress on the ceramic board.
Innovation Solution
Incorporating stress relaxation portions, such as slits or grooves, in the circuit pattern metal plate under the external connection terminals, where the solder bonds are positioned, to distribute thermal stress and prevent crack formation without increasing the module's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stress relaxation portions are formed in the circuit pattern metal plate to reduce thermal stress on the ceramic board, then the risk of ceramic board cracking is reduced, but the mounting area increases leading to larger module size
Solution Approach 1:
The invention applies stress relaxation portions only at specific locations where thermal stress concentrates (around external connection terminals and semiconductor elements) rather than uniformly across the entire circuit pattern metal plate. This localized approach reduces ceramic board cracking risk at critical stress points while minimizing the additional area required, thus resolving the contradiction between reliability improvement and module size increase.
2Reliability
If a sufficient amount of solder is supplied between the external connection terminal and the circuit pattern metal plate to prevent electrical connection breakage, then electrical connection reliability is improved, but thermal stress on the ceramic board increases
Solution Approach 1:
The invention converts the harmful thermal expansion of solder into a beneficial stress relief mechanism by designing stress relaxation portions in the circuit pattern metal plate. These portions allow the solder to expand and contract thermally without transmitting excessive stress to the ceramic board, thus maintaining electrical connection reliability while mitigating the harmful thermal stress effect.
3Reliability
If the case is designed to accommodate thermal deformation of the base plate, then thermal reliability is improved, but stress concentrates on the peripheral edge portion of the circuit pattern metal plate
Solution Approach 1:
The invention segments the circuit pattern metal plate by introducing stress relaxation portions (such as grooves or holes) that divide the continuous metal structure into separated regions. This segmentation allows the plate to accommodate thermal deformation more uniformly, preventing stress concentration at peripheral edges while maintaining overall structural integrity and thermal reliability.
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 stress relaxation portions effectively reduce the risk of ceramic board cracking and dielectric breakdown, allowing for the use of lower-strength ceramic materials and maintaining the module's size by decentralizing stress application, thus enhancing thermal reliability.
Implementation Method 1
a thermal stress caused by the expansion and contraction of the solder and the circuit pattern metal plate is applied to a portion of the ceramic board
Data Source
AI summary
A semiconductor module includes a ceramic board, a circuit pattern metal plate on a principal surface of the ceramic board, and an external connection terminal including a bonding portion and a conductive portion. The metal plate includes a bonding area at a first surface thereof, and a stress relaxation portion disposed within the bonding area. The bonding portion has a bonding surface, and an edge that is located at a position overlapping an area in which the stress relaxation portion is disposed in a plan view. A solder is disposed between the bonding surface and the bonding area, to bond the external connection terminal to the circuit pattern metal plate.