Semiconductor Bonding via Malleable Metal Interlayer
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Solution Overview
Problem
Semiconductor components experience mechanical stress due to thermal expansion differences with substrates, leading to reduced performance and reliability, especially when using traditional soldering methods that introduce stress and undesirable material interactions.
Innovation Solution
A method involving diffusion bonding or thermocompression welding using a thin film of malleable metal on a metallized substrate, applying pressure and heat below the melting point to promote interfacial interaction and form a compound or alloy with a higher melting temperature, reducing mechanical stress and improving bonding precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional soldering methods are used to bond semiconductor components to substrates, then electrical contact and thermal conduction are achieved, but mechanical stress increases due to CTE differences and undesirable material interactions occur
Solution Approach 1:
The patent introduces a malleable metal interlayer between the semiconductor component and substrate. This intermediary layer accommodates CTE differences through its plastic deformability, reducing mechanical stress while maintaining bonding reliability. The malleable metal acts as a stress-absorbing mediator that prevents direct stress transmission between dissimilar materials.
Solution Approach 2:
The patent changes the bonding parameters by heating to a temperature below the melting point of the malleable metal and applying pressure to induce plastic deformation. This parameter change enables stress relief through controlled deformation rather than through melting and solidification as in traditional soldering, thereby reducing mechanical stress while maintaining reliable bonding.
2Stress or pressure
If a substrate with CTE close to semiconductor component is chosen, then mechanical stress is reduced, but thermal conductivity decreases
Solution Approach 1:
The patent segments the bonding interface into multiple functional layers: a thermally conductive substrate, a stress-relieving malleable metal interlayer, and the semiconductor component. This segmentation allows the substrate to maintain high thermal conductivity while the interlayer handles stress accommodation, thereby achieving both low operating temperature and reduced mechanical stress.
Solution Approach 2:
The malleable metal interlayer serves as an intermediary that decouples the thermal and mechanical functions. It allows the substrate to be optimized for thermal conductivity without compromising mechanical stress resistance, as the interlayer absorbs thermal expansion differences while permitting efficient heat transfer from the semiconductor component.
3Stress or pressure
If solder with low melting temperature is chosen, then mechanical stress during bonding is reduced, but solder migration and wicking occur under thermal cycling
Solution Approach 1:
The patent changes the bonding mechanism from melting-based (soldering) to plastic deformation-based (thermocompression bonding). By heating below the melting point and applying pressure, the malleable metal undergoes controlled plastic deformation to form strong bonds without melting, thereby avoiding migration and wicking issues while maintaining bonding stability under thermal cycling.
Solution Approach 2:
The patent replaces the thermal-melting mechanism with a mechanical-plastic deformation mechanism. Instead of relying on melting and solidification, the bonding is achieved through pressure-induced plastic deformation of the malleable metal, which creates stable, migration-resistant bonds that maintain reliability under subsequent thermal cycling.
4Strength
If molten solder is used for bonding, then bonding strength is achieved, but thickness precision and bonding accuracy are reduced
Solution Approach 1:
The patent changes the bonding parameters by eliminating melting and instead using controlled plastic deformation at temperatures below the melting point. This allows precise control of the bonding process through pressure and temperature parameters, maintaining bonding strength while achieving superior thickness precision and bonding accuracy through controlled deformation rather than uncontrolled melting.
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 approach minimizes mechanical stress, enhances bonding strength, and increases the operational lifetime of semiconductor components by forming a strong, stress-reduced interface without melting the metals, thus improving thermal conductivity and reliability.
Implementation Method 1
The predetermined pressure is selected to cause plastic deformation of the malleable metal(s) and promote intimate physical contact with the adjacent surface
Implementation Method 2
providing a predetermined quantity of heat to the third structure for a predetermined period of time, the predetermined quantity of heat raising the temperature of the third structure to a temperature higher than ambient temperature but lower than the melting temperature of any of the materials of the third structure
Implementation Method 3
the predetermined time and the predetermined pressure are selected so that the malleable metal(s) interact with the adjacent semiconductor component layer. In one instance, the interaction between the malleable metal(s) disposed on the substrate includes the forming of a compound or alloy with the metal on the semiconductor component
Implementation Method 4
Failure of semiconductor components is accelerated in part by mechanical stress. One source of stress results from the different coefficient-of-thermal-expansion (CTE) between the material of the semiconductor component and the material of the substrate. At temperatures where the solder is molten, the mechanical stress is insubstantial. Once the temperature decreases below the melting temperature of the solder, the substrate applies a mechanical stress on the component
Data Source
AI summary
A method of attaching a semiconductor component to a heat-sink where the component is first placed onto a heat-sink substrate whose attachment surface comprises a malleable-metal film, a semiconductor component is placed onto the malleable-metal film, and pressure and heat is applied for a predetermined time to the stack including substrate with malleable-metal film and semiconductor component.