Cu-Cu Bonded Connection Structure With Porous Copper Films
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Solution Overview
Problem
As semiconductor elements become more sophisticated, the narrower pitch between connection terminals increases the likelihood of short-circuiting between adjacent solder layers during reflow soldering, leading to short-circuits between adjacent connection terminals.
Innovation Solution
A connection structural body is designed with first and second roughened-surface copper metal films on opposing surfaces of connection terminals, featuring a porous structure formed by piling copper deposits, which are bonded without intermetallic compounds, allowing for direct copper-to-copper bonding and reducing the risk of short-circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch between connection terminals is narrowed to increase integration density, then the number of connection terminals per unit area increases, but short-circuiting between adjacent solder layers becomes more likely
Solution Approach 1:
The patent extracts the harmful solder material from the bonding interface and replaces it with a copper-based roughened-surface film structure. By removing the solder layer that causes short-circuiting and using direct copper-to-copper bonding through roughened surfaces, the design eliminates the short-circuit risk while maintaining narrow pitch between connection terminals
Solution Approach 2:
The patent employs roughened-surface copper metal films with porous structures formed by piled copper deposits. This porous morphology increases surface area for bonding while maintaining electrical conductivity and mechanical strength, allowing reliable connections at narrow pitches without requiring solder that could cause short-circuits
2Strength
If conventional solder bonding is used to join connection terminals, then bonding strength is achieved, but intermetallic compounds form and increase electrical resistance
Solution Approach 1:
The patent uses homogeneous copper material for both connection terminals and bonding films, eliminating the formation of intermetallic compounds that occur when dissimilar metals (copper and solder) are bonded. This homogeneous copper-copper bonding maintains low electrical resistance while achieving sufficient bonding strength through the roughened surface structure
Solution Approach 2:
The patent performs preliminary surface roughening treatment on copper terminals before bonding to create porous structures with increased surface area. This preliminary action prepares the surfaces for strong bonding while maintaining copper homogeneity, avoiding intermetallic compound formation and keeping electrical resistance low
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 porous structure of the copper metal films enhances bonding strength and reduces short-circuiting, ensuring reliable electrical connections between semiconductor elements and wiring substrates.
Implementation Method 1
these films are formed through an electrolytic copper plating process with polyacrylic acid
Implementation Method 2
creating a porous structure that allows for direct bonding without forming intermetallic compounds
Data Source
AI summary
A connection structural body includes: a first connection terminal including a first opposing surface; a first roughened-surface copper metal film formed on the first opposing surface; a second connection terminal including a second opposing surface facing the first opposing surface; and a second roughened-surface copper metal film formed on the second opposing surface and bonded to the first roughened-surface copper metal film. The first roughened-surface copper metal film includes a structure in which first deposits of copper are piled over one another on the first opposing surface. The second roughened-surface copper metal film includes a structure in which second deposits of copper are piled over one another on the second opposing surface. A bonded portion of the first and second roughened-surface copper metal films includes a structure in which the first deposits and the second deposits are piled such that the bonded portion includes pores.