Power Module Substrate Trench Design for Low Resistance
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Solution Overview
Problem
Conventional power module substrates face challenges in balancing bonding reliability and electric resistance value due to the thick glass layer in sintered Ag layers, which can lead to high electric resistance and improper connections between the circuit layer and semiconductor elements.
Innovation Solution
A power module substrate with a sintered Ag layer featuring a trench that connects the Ag layer to the circuit layer, allowing the Ag layer to extend along the trench's inner surface, reducing electric resistance while maintaining high bonding reliability by using a glass-containing Ag paste with increased glass content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the glass content in glass-containing Ag paste is increased to improve bonding reliability, then the bonding reliability between circuit layer and sintered Ag layer is improved, but the electric resistance value of the sintered Ag layer increases
Solution Approach 1:
The sintered Ag layer is segmented into multiple functional layers: a glass layer containing conductive particles for bonding reliability, and a low-resistance Ag layer for electrical conduction. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the sintered Ag layer have different compositions and properties. The glass layer provides local bonding strength and adhesion, while the Ag layer provides local electrical conductivity. This local quality differentiation resolves the contradiction between bonding reliability and low electric resistance.
2Strength
If a thick glass layer is formed in the sintered Ag layer to improve bonding strength, then the bonding strength between circuit layer and sintered Ag layer is improved, but the electric resistance value increases leading to improper connections
Solution Approach 1:
The sintered Ag layer is divided into a glass layer and an Ag layer. The glass layer can be made thick to provide bonding strength, while the Ag layer provides a low-resistance electrical path, thus resolving the contradiction between bonding strength and electric resistance.
Solution Approach 2:
The sintered Ag layer is a composite structure combining glass material and Ag material. The glass provides mechanical strength and adhesion, while the Ag provides electrical conductivity. This composite approach allows simultaneous achievement of bonding strength and low electric resistance.
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 solution effectively reduces the electric resistance value between the semiconductor and circuit layers, enhancing the reliability of the power module by maintaining low resistance and preventing thermal resistance increases during repeated power cycles.
Implementation Method 1
the glass-containing Ag paste is applied on the surface of the circuit layer made of aluminum or copper; and subjected to sintering. By following the process, the oxide film formed on the circuit layer is removed since the oxide film reacts with the glass; and the sintered Ag layer is formed.
Implementation Method 2
the oxide film formed on the circuit layer is removed since the oxide film reacts with the glass
Implementation Method 3
the Ag layer has an extended part extending to the circuit layer along with an inner surface of the slot, and the extended part electrically connects the Ag layer and the circuit layer
Data Source
AI summary
An elongated trench (35) is formed so as to connect the Ag layer (32) and the exposed part of the circuit layer stretching out around the Ag layer (32). The trench (35) a narrow and elongated recessed part penetrating the glass layer (31) and the aluminum oxide film (12A) from the Ag layer (32) to reach the surface (12a) of the circuit layer (2). The extended part (36), which is a part of the Ag layer (32) flatted along with the inner surface (35a) of the trench (35), is formed in the trench (35). The Ag layer (32) and the circuit layer (12) are electrically connected directly by Ag with a low electric resistance value by the extended part (36) in the portion where the trench (35) is formed.