Dual-Layer Bonding Agent for Semiconductor Thermal Expansion Matching
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Solution Overview
Problem
Semiconductor devices face reliability issues due to detachment caused by differences in thermal expansion coefficients between the semiconductor chip and the bonding agent, and between the bonding agent and the strain-causing metal body, leading to impaired bonding and potential destruction of the semiconductor chip.
Innovation Solution
A semiconductor device is designed with a bonding layer comprising a filler-containing first layer and a second layer with a higher thermal expansion coefficient, where the first layer has a larger amount of filler and a lower thermal expansion coefficient, and the second layer has a smaller amount of filler and better meltability, ensuring improved bonding between the metal body and the semiconductor chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mixing amount of silica filler is increased to achieve a thermal expansion coefficient close to that of the semiconductor chip, then the thermal expansion coefficient matching is improved, but the silica filler protrudes from the bonding agent which impairs the reliability of bonding between the bonding agent and the semiconductor chip
Solution Approach 1:
The bonding agent is divided into two distinct layers: a first layer containing silica filler with thermal expansion coefficient close to the semiconductor chip, and a second layer with thermal expansion coefficient close to the metal body. This segmentation allows each layer to fulfill its specific function without compromise - the first layer ensures thermal matching with the chip while the second layer provides bonding reliability, eliminating the filler protrusion problem that occurs when a single layer attempts to balance both requirements.
Solution Approach 2:
Different regions of the bonding agent are assigned different properties: the first layer (adjacent to semiconductor chip) has low thermal expansion coefficient and fine filler distribution for precise thermal matching, while the second layer (adjacent to metal body) has higher thermal expansion coefficient and different composition for robust bonding. This local differentiation resolves the contradiction by allowing optimal properties in each location rather than compromising uniformly across the entire bonding agent.
2Reliability
If a single bonding agent is used to match thermal expansion coefficients, then the bonding reliability may be compromised, but using a layered structure increases device complexity
Solution Approach 1:
The bonding agent is segmented into two functional layers with distinct compositions and thermal expansion properties. The first layer (with silica filler) interfaces with the semiconductor chip providing thermal expansion matching, while the second layer interfaces with the metal body providing strong bonding. This segmentation resolves the reliability issue by allowing each layer to be optimized for its specific function, while the complexity increase is minimal - merely adding one additional bonding layer.
Solution Approach 2:
The bonding structure uses composite materials approach by combining two different bonding agent formulations in a layered configuration. Each layer is composed of materials specifically selected for its function - the first layer uses silica-filled compound for thermal matching, while the second layer uses a different composition for bonding strength. This composite structure achieves superior reliability compared to a single homogeneous bonding agent, with the complexity penalty being acceptable given the performance gains.
3Reliability
If the thermal expansion coefficient of the bonding agent is adjusted to match the semiconductor chip, then thermal matching is improved, but the bonding agent cannot adequately bond to the metal body with different thermal expansion properties
Solution Approach 1:
The bonding agent is segmented into two layers where the first layer (containing silica filler) is optimized for thermal expansion matching with the semiconductor chip, while the second layer is optimized for bonding strength with the metal body. This segmentation allows the first layer to provide the necessary thermal expansion coefficient matching without compromising the bonding strength, as the second layer specifically handles the metal body interface with appropriate material properties.
Solution Approach 2:
Different thermal expansion coefficients are assigned to different locations within the bonding agent structure. The first layer adjacent to the semiconductor chip has thermal expansion coefficient matched to the chip, while the second layer adjacent to the metal body has thermal expansion coefficient matched to the metal. This local quality differentiation allows optimal thermal matching at each interface without sacrificing bonding strength, resolving the contradiction between thermal matching and bonding strength.
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 enhances the reliability of bonding between the bonding layer and the semiconductor chip by matching thermal expansion coefficients, preventing detachment and destruction, and ensuring high bondability and heat resistance.
Implementation Method 1
the semiconductor chip may be detached or destroyed due to the differences in thermal expansion coefficient between the strain-causing body and a bonding agent and between the semiconductor chip and the bonding agent
Data Source
Figure 1
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Figure 3(a)~3(d)
AI summary
A semiconductor device includes a metal body; a bonding layer placed on the metal body; and a semiconductor chip placed on the bonding layer. The bonding layer includes a filler-containing first layer formed between the metal body and the semiconductor chip and a second layer bonded to the first layer and the semiconductor chip. The second layer has a thermal expansion coefficient higher than that of the first layer.