Gallium-Based Composite Solder for Low Thermal Stress Interconnections
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Solution Overview
Problem
Microelectronic devices with low k-value dielectric materials face damage from thermal stresses during manufacture, and existing solutions like stiffeners or changing geometry are not fully effective in reducing damage.
Innovation Solution
The use of solder materials with lower melting points, such as gallium-based composite solders, which react with metals to form intermetallic compounds with higher melting temperatures, reducing thermal stresses and allowing for more aggressive thinning of components, and the application of these solders through specific processing methods like reflowing and acid solutions to form stable interconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional soldering materials with high melting points are used, then strong interconnections are formed, but thermal stresses damage low k-value dielectric materials during manufacturing
Solution Approach 1:
The patent changes the melting point parameter of the solder material from traditional high melting point materials (like Sn-Pb with melting point around 183-250°C) to low melting point materials (melting point below 150°C, preferably 100-120°C). This parameter change allows the solder to remain liquid at lower processing temperatures, thereby reducing thermal stress on low k-value dielectric materials while still forming reliable interconnections.
Solution Approach 2:
The patent employs composite solder materials consisting of multiple components including gallium (40-60 wt%), indium (10-30 wt%), and other metals like tin, silver, or copper (10-30 wt%). This composite formulation achieves a eutectic composition that lowers the melting point while maintaining adequate mechanical strength and interconnection reliability, resolving the contradiction between low melting point and strong bonding.
2Length of moving object
If component thickness is reduced to enable aggressive thinning, then device integration is improved, but mechanical strength decreases making components more vulnerable to thermal stress
Solution Approach 1:
By changing the solder melting point parameter to below 150°C, the patent enables processing at lower temperatures that do not require thick components for thermal management. This allows aggressive thinning of components (reducing thickness parameter) while the low thermal stress from low-temperature soldering compensates for the reduced mechanical strength of thinner components.
3Strength
If stiffeners are added to components to withstand thermal stresses, then mechanical strength is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for stiffener structures by taking out the root cause of the problem - the high processing temperature. By using low melting point solder materials that enable processing below 150°C, the patent removes the requirement for additional mechanical reinforcement, thereby reducing device complexity while maintaining thermal stress 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
This approach reduces thermal stresses on microelectronic components during manufacturing, leading to higher yields and enabling more aggressive thinning of components, while providing stable interconnections suitable for electronic devices.
Implementation Method 1
react with metals to form intermetallic compounds
Implementation Method 2
removing an oxide on an exposed surface of the electrical contact using the acid solution
Data Source
AI summary
A solder and methods of forming an electrical interconnection are shown. Examples of solders include gallium based solders. A solder including gallium is shown that includes particles of other solders mixed with a gallium based matrix. Methods of applying a solder are shown that include swiping a solder material over a surface that includes a resist pattern. Methods of applying a solder are also shown that include applying a solder that is immersed in an acid solution that provides a fluxing function to aid in solder adhesion.