Semiconductor Mounting Junctions with Alloy-Metal Composite for Stress Relief
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Solution Overview
Problem
The increasing demand for finer wiring and faster signal processing in semiconductor devices leads to the use of low dielectric constant insulating films, which are fragile and prone to exfoliation or cracking due to thermal stress, especially at the corners of rectangular semiconductor chips, and are affected by electromigration phenomena causing fluctuations in connection resistance.
Innovation Solution
A mounting structure with junctions that include a metal having a lower modulus of elasticity than the alloy, where the alloy is grown from both the semiconductor chip and the circuit board electrodes, surrounded by solder with a lower modulus of elasticity, to reduce stress concentration and prevent exfoliation, and the use of specific alloy compositions like nickel-tin alloys to enhance connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitches of electrode terminals are reduced to increase pin density, then the number of pins per area increases, but short circuits occur between adjacent electrode terminals due to faulty bridges or thermal stress
Solution Approach 1:
The patent applies local quality by creating a multi-layer electrode structure where different materials and properties are used at different locations. Specifically, a first electrode terminal layer is formed on the semiconductor chip, a second electrode terminal layer is formed on the circuit board, and these are connected through protruding electrodes with insulating films. This layered structure provides localized insulation and connection paths that prevent short circuits while maintaining high pin density.
Solution Approach 2:
The patent uses composite materials by combining multiple materials in the electrode structure. The protruding electrodes are made of conductive material, covered with insulating films, and connected through alloy layers formed by eutectic reactions. This composite structure provides both electrical connection and mechanical strength while preventing adjacent terminal short circuits through the insulating barrier.
2Strength
If solder bumps are used for protruding electrodes, then bonding strength is achieved, but faulty bridges cause short circuits between adjacent electrode terminals
Solution Approach 1:
The patent introduces an insulating film as an intermediary between the protruding electrodes and the electrode terminals. This insulating film is formed on the surface of the protruding electrodes before mounting, and it prevents direct contact between adjacent solder bumps, thereby eliminating faulty bridges while maintaining the bonding strength provided by the solder material.
Solution Approach 2:
The insulating film provides localized insulation precisely where needed - on the surface of the protruding electrodes. This allows the solder material to maintain its bonding strength function while the insulating film prevents the harmful short circuit function, creating separate local functions within the same structure.
3Strength
If molding resin is used to fill clearance between semiconductor chip and circuit board, then bonding strength is enhanced, but faulty connections occur due to thermal stress from difference in thermal expansion coefficients
Solution Approach 1:
The patent changes the material parameters of the protruding electrode structure by introducing insulating films and multi-layer electrode configurations. This modifies the thermal and mechanical properties of the connection structure, reducing the stress concentration that occurs with conventional single-material solder bumps subjected to thermal expansion differences between the semiconductor chip and circuit board.
4Strength
If anisotropic conductive film with metallic particles is used for protruding electrodes made of gold or copper, then bonding is achieved, but metallic particles join together between adjacent protruding electrodes causing short circuits
Solution Approach 1:
The patent introduces an insulating film as an intermediary barrier on the surface of the protruding electrodes. This insulating film prevents the metallic particles from the anisotropic conductive film from directly contacting and joining with adjacent protruding electrodes, thereby eliminating short circuits while allowing the anisotropic conductive film to perform its bonding function.
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 effectively reduces stress on fragile insulating films, prevents exfoliation and cracking, and stabilizes connection resistance by suppressing electromigration, thereby achieving higher connection reliability and maintaining stable bonding between semiconductor chip and circuit board electrodes.
Implementation Method 1
junctions each of which contains an alloy and a metal having a lower modulus of elasticity than the alloy, has a cross section structure containing the alloy surrounded by the metal having the lower modulus of elasticity, and connects the first electrode terminal and the second electrode terminal
Implementation Method 2
use of specific alloy compositions like nickel-tin alloys to enhance connection reliability... surrounded by solder with a lower modulus of elasticity, to reduce stress concentration and prevent exfoliation
Implementation Method 3
the alloy is grown from both the semiconductor chip and the circuit board electrodes
Implementation Method 4
growing a first alloy composed of a metal constituting a first protruding electrode and a metal constituting solder and a second alloy composed of a metal constituting a second protruding electrode and the metal constituting the solder, by melting the solder
Data Source
AI summary
In a provided mounting structure, an electronic component such as a semiconductor chip having a fragile film is mounted on a substrate such as a circuit board with higher connection reliability. A junction that connects an electrode terminal (4) of an electronic component (1) and an electrode terminal (5) of a substrate (2) contains an alloy (8) and a metal (9) having a lower modulus of elasticity than the alloy (8). The junction has a cross section structure in which the alloy (8) is surrounded by the metal (9) having the lower modulus of elasticity.