Bonded Substrate Terminal Geometry for Reliable Solder Joining
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Solution Overview
Problem
The existing method for manufacturing bonded substrates, as disclosed in US 2004/113994 A, faces issues with inconsistent electrical bonding of solder layers on terminals due to an unfavorable ratio of metal core height to solder thickness, leading to unreliable connections.
Innovation Solution
The method involves forming terminals with a metal core and a solder layer where the ratio of the metal core height to the solder thickness is set between 1:1 and 2:1, ensuring that the variation range of the core height does not overlap with the variation range of the sum of the core height and solder thickness, thereby ensuring reliable electrical bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ratio of metal core height to solder thickness is large (e.g., 3.75:1 to 4.29:1), then the metal core can be made taller to improve electrical connection, but the variation ranges of core height and total height overlap, causing unreliable electrical bonding
Solution Approach 1:
The invention changes the critical parameter from a large height ratio (3.75:1 to 4.29:1) to a controlled ratio within 1:1 to 2:1. This parameter change eliminates the overlap between variation ranges of core height and total height, ensuring that the solder layer always extends beyond the metal core tip. This reliable geometric relationship guarantees electrical bonding without requiring tight manufacturing tolerances.
2Strength
If the metal core height is increased to ensure electrical connection, then the connection strength improves, but the adhesion between metal core and solder layer deteriorates
Solution Approach 1:
The invention creates a composite terminal structure where the metal core and solder layer are combined in a specific geometric relationship. By controlling the height ratio to 1:1 to 2:1, the design optimizes the interface between the two materials, ensuring both mechanical strength and adhesion energy are maximized. The solder layer completely covers the metal core tip, creating a robust composite structure that prevents delamination while maintaining strong electrical connection.
3Ease of operation
If a flexible substrate is used to improve ease of operation, then the substrate can be bent to connect terminals, but the inconsistent solder bonding causes connection failures
Solution Approach 1:
The invention applies beforehand cushioning by designing a geometric configuration where the solder layer extends beyond the metal core tip. This pre-established geometric relationship acts as a cushion against variations in substrate flexibility, bending, and positioning. Even when the flexible substrate is bent or deformed, the solder layer maintains contact and ensures reliable electrical bonding, preventing connection failures.
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 enhances the reliability of electrical bonding between terminals, preventing adhesion issues and ensuring consistent connections by maintaining a sufficient solder layer thickness while avoiding excessive core height, thus improving the manufacturing process for bonded substrates.
Implementation Method 1
Next, the solder begins to melt due to heating, and the terminals approach the land portions.
Implementation Method 2
Then, the epoxy-based resin surrounding the land portions, the terminals and the solder is cured.
Implementation Method 3
electrically bonding the first terminals to the second terminals by heating the first substrate and the second substrate while applying pressure
Data Source
AI summary
A method for manufacturing bonded substrates includes: forming the first terminals on the first substrate, the first terminals each having a metal core projecting from a surface of the first substrate, each metal core coated with a solder layer lower in a melting point than the metal core; forming the conductive second terminals on the second substrate; and electrically bonding the first terminals to the second terminals by heating the first and second substrates while applying pressure to the first substrate and the second substrate. In the forming of the first terminals, a ratio of a height of the metal core from the surface of the first substrate in a thickness direction of the first substrate to a thickness of the solder layer in the thickness direction of the first substrate is in a range of from 1:1 to 2:1.