Power Semiconductor Device Electrode Crack Prevention
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Solution Overview
Problem
Existing power semiconductor devices face issues with solder cracks due to differences in linear expansion coefficients between aluminum heat dissipation members and insulating substrates, leading to inadequate cooling and increased material costs, while metal sintered bodies can cause upper electrode cracks and complex manufacturing processes.
Innovation Solution
A power semiconductor device design featuring a semiconductor element bonded via a metal sintered body to an insulating substrate, with an aluminum cooler bonded via solder, and a protective film with an inclined surface on the upper electrode to prevent cracking, along with a lead bonded via solder to the upper electrode using a copper-Invar clad material to optimize linear expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If solder is used to bond aluminum heat dissipation member to insulating substrate, then thermal conduction is improved and device weight is reduced, but solder cracks occur early due to large difference in linear expansion coefficient
Solution Approach 1:
The patent changes the material parameter of the insulating substrate by using a ceramic substrate with a linear expansion coefficient specifically selected to match that of aluminum (approximately 23Ă10^-6/â). This parameter matching eliminates the expansion mismatch that causes solder cracking, while maintaining the thermal conduction benefits of solder bonding.
Solution Approach 2:
The patent employs a composite structure where a ceramic substrate serves as the insulating base, combined with solder material for bonding. The ceramic material provides both electrical insulation and thermal conduction properties while its expansion coefficient is matched to aluminum, creating a composite system that resolves the contradiction between thermal performance and bonding reliability.
2Reliability
If copper pattern layer thickness is increased to match linear expansion coefficients, then solder crack is prevented, but difference in linear expansion coefficient between semiconductor element and insulating substrate increases causing electrode cracks
Solution Approach 1:
The patent changes the fundamental approach by selecting a ceramic substrate material whose linear expansion coefficient inherently matches both aluminum (for heat dissipation member bonding) and semiconductor elements. This eliminates the need to increase copper pattern thickness, thereby preventing both solder cracks and electrode cracks through proper material selection rather than structural modification.
3Reliability
If metal sintered body is used to bond semiconductor element to insulating substrate, then bonding reliability in high temperature operation is improved, but upper electrode cracks due to pressurization during bonding
Solution Approach 1:
The patent introduces a ceramic substrate as an intermediary component between the semiconductor element and the external environment. This ceramic substrate acts as a stable platform that distributes bonding pressure uniformly, preventing localized stress concentration that would crack the upper electrode, while still enabling reliable high-temperature operation through the metal sintered body bonding method.
4Stability of the object's composition
If iron frame material is used to restrain aluminum heat dissipation member expansion, then thermal expansion is controlled, but manufacturing complexity and material cost increase due to multiple parts
Solution Approach 1:
The patent extracts and eliminates the iron frame component entirely by integrating the thermal expansion control function directly into the ceramic substrate. The ceramic substrate's inherent linear expansion coefficient matching that of aluminum provides the restraining effect without requiring a separate frame structure, thereby reducing component count and manufacturing complexity while maintaining thermal expansion control.
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 design prevents upper electrode cracks, optimizes thermal management, reduces material costs, and enhances reliability for harsh environments by minimizing solder cracks and processing complexities, achieving durable and cost-effective power semiconductor devices.
Implementation Method 1
a power semiconductor device using a metal sintered body to bond a rear surface electrode of a semiconductor element and a wiring member
Implementation Method 2
a power semiconductor element is bonded via a solder to the upper surface of an insulating substrate, an aluminum heat dissipation member is bonded via a solder to the rear surface of the insulating substrate
Implementation Method 3
an aluminum heat dissipation member is bonded via a solder to the rear surface of the insulating substrate
Implementation Method 4
a protective film with an inclined surface on the upper electrode to prevent cracking
Implementation Method 5
a lead bonded via a solder to the upper electrode using a copper-Invar clad material to optimize linear expansion coefficients
Data Source
AI summary
In a power semiconductor device, the thickness dimension of a protective film of a semiconductor element is made smaller than that of an upper electrode, so a protective film is not pressed by being pressurized from upward when bonded by a metal sintered body, and the force of tearing off the upper electrode riding on an inclined surface of the protective film does not act, so that no crack of the upper electrode occurs, thus maintaining the soundness of the semiconductor element. Also, a lead bonded by a solder to the upper electrode of the semiconductor element is made of a copper-Invar clad material, the linear expansion coefficient of which is optimized, and thereby it is possible to realize a durability superior to that of a heretofore known wire-bonded aluminum wiring.