Power Module Solder Alloy Layer Crack Suppression
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Solution Overview
Problem
Power modules with semiconductor elements bonded to circuit layers using solder experience crack development and increased thermal resistance when subjected to power cycles, particularly in modules with copper or aluminum alloy circuit layers, which compromises reliability.
Innovation Solution
A power module configuration featuring a circuit layer with a copper or copper alloy surface, a solder layer, and an alloy layer at the interface containing 0.5-10% Ni and 30-40% Cu, with a coverage of 85% or more, suppresses crack development and enhances reliability by forming a thermally stable intermetallic compound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ni plating film is formed on the circuit layer surface and solder material is arranged on it to bond the semiconductor element, then the bonding is achieved, but cracks develop in the solder and thermal resistance increases when power cycles are applied
Solution Approach 1:
The invention changes the chemical composition parameters of the solder material by adding specific amounts of Ni (0.5-10% by mass) and Cu (30-40% by mass) to the Sn-based solder. This compositional modification transforms the solder's interaction with the Cu circuit layer, preventing harmful intermetallic compound formation while maintaining bonding strength, thereby resolving the contradiction between achieving bonding and preventing crack development during power cycles
Solution Approach 2:
The invention creates a composite solder material system comprising Sn as the base metal with controlled additions of Ni and Cu. This composite structure forms a stable alloy layer at the interface between the solder and Cu circuit layer, which prevents crack propagation. The composite material approach allows the solder to maintain both bonding capability and resistance to thermal fatigue, resolving the contradiction between bonding strength and solder integrity under power cycling
2Duration of action of stationary object
If the semiconductor element is bonded to the circuit layer using conventional soldering, then the assembly is completed, but the solder layer fractures at an early stage under power cycle loading
Solution Approach 1:
The invention modifies the solder material composition parameters by incorporating Ni (0.5-10% by mass) and Cu (30-40% by mass) into the Sn-based solder. This parameter change transforms the thermal and mechanical properties of the solder, enabling it to withstand power cycle loading without early-stage fracture. The modified composition allows the solder to maintain its structural integrity and bonding function throughout the module's operational lifespan, resolving the contradiction between operational duration and 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 solution effectively prevents early breakage of the solder layer and maintains low thermal resistance even after 100,000 power cycles, ensuring high reliability and prolonged module lifespan.
Implementation Method 1
an alloy layer including Ni and Cu is formed at the interface between the solder layer and the circuit layer
Data Source
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AI summary
A power module is disclosed, including a power module substrate in which a circuit layer is arranged on one surface of an insulating layer; and a semiconductor element that is bonded onto the circuit layer, in which a copper layer composed of copper or a copper alloy is provided on a surface of the circuit layer to be bonded to the semiconductor element, a solder layer formed by using a solder material between the circuit layer and the semiconductor element is provided, an alloy layer containing Sn as a main component, 0.5% by mass or more and 10% by mass or less of Ni, and 30% by mass or more and 40% by mass or less of Cu at an interface of the solder layer with the circuit layer is formed, and the coverage of the alloy layer at the interface is 85% or more.