Conductive Nanotube Interconnects for Semiconductor Chip Mounting

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Solution Overview

Problem

Existing semiconductor chip mounting methods, such as metal bump and carbon nanotube bonding, face challenges with electromigration-induced breakdown and thermal expansion stress, making it difficult to dismount defective chips without damaging the mounting board.

Innovation Solution

A semiconductor device design featuring conductive nanotubes extending between the chip and mounting board, with a press mechanism or flexible adhesive to allow for easy detachment of semiconductor chips by elastic deformation of the nanotubes, which absorb thermal expansion stress and maintain electrical contact at sidewalls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If metal bumps are used to bond semiconductor chips to mounting boards, then mechanical and electrical bonding is achieved, but electromigration causes breakdown of the bumps

Engineering Contradiction:

Improvebonding reliabilityVSAvoidelectromigration breakdown

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the material parameter from conventional metal (solder) to carbon nanotubes. Carbon nanotubes have superior electrical conductivity and resistance to electromigration compared to traditional metal bumps, thereby eliminating the electromigration breakdown issue while maintaining reliable electrical bonding between the semiconductor chip and mounting board

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs carbon nanotubes as a composite material structure to replace homogeneous metal bumps. The carbon nanotube structure provides both mechanical strength and electrical conductivity with immunity to electromigration, creating a composite bonding solution that overcomes the limitations of pure metal materials

Inventive Principle:

Principle #40Composite materials

2Strength

If conventional bonding methods are used, then strong bonding is achieved, but defective chips cannot be easily removed for replacement

Engineering Contradiction:

Improvebonding strengthVSAvoidchip replacement difficulty

Core Design Contradiction:

StrengthVSEase of repair

Solution Approach 1:

The patent introduces a press mechanism that can dynamically adjust the bonding pressure. During normal operation, the press mechanism maintains strong bonding pressure for reliable electrical connection. When chip replacement is needed, the press mechanism can be activated to release the bonding pressure, allowing the semiconductor chip to be easily removed from the mounting board without damaging either component

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If high current density flows through metal bumps, then miniaturization is achieved, but electromigration increases causing breakdown

Engineering Contradiction:

Improveconductive pad miniaturizationVSAvoidelectromigration

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the electrical conductivity parameter by using carbon nanotubes instead of metal. Carbon nanotubes can carry extremely high current densities (up to 10^9 A/cm²) without electromigration, enabling further miniaturization of conductive pads while maintaining or improving current carrying capacity and eliminating electromigration-related breakdown

Inventive Principle:

Principle #35Parameter changes

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

Enables the easy removal and replacement of defective semiconductor chips without damaging the mounting board, reducing the risk of breakdown due to electromigration and thermal stress, while maintaining reliable electrical contact.

Implementation Method 1

conductive nanotubes extending from the conductive pads of one of the mounting board and the semiconductor chip

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a press mechanism for pressing the semiconductor chip against the mounting board to mount the semiconductor chip on the mounting board

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS7633148B2Semiconductor device with semiconductor chips mounted on mounting board via conductive anaotubes

Publication Date: 2009.12.15 FUJITSU LTD

AI summary

A plurality of conductive pads (2) are formed on a mounting surface of a mounting board. Conductive pads (11) are formed on a principal surface of a semiconductor chip (10) at positions corresponding to the conductive pads of the mounting board, when the principal surface faces toward the mounting board. A plurality of conductive nanotubes (12) extend from the conductive pads of one of the mounting board and the semiconductor chip. A press mechanism (3) presses the semiconductor chip against the mounting board and restricts a position of the semiconductor chip on the mounting surface to mount the semiconductor chip on the mounting board, in a state that tips of the conductive nanotubes are in contact with the corresponding conductive pads not formed with the conductive nanotubes.