Metal Particles-Dispersed Composition for Flip Chip Mounting
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Solution Overview
Problem
Conventional flip chip mounting processes face challenges in forming fine-pitch bumps and achieving high productivity due to viscosity increases in thermosetting resin adhesives, leading to electrical short circuits and reduced connecting reliability.
Innovation Solution
A composition with metal particles dispersed in a thermoset resin, where a curing agent is embedded within the particles, allowing them to melt and initiate a curing reaction, combined with a convection additive that generates gas upon heating, enabling self-assembly of metal particles between electrodes and forming a thermoset resin layer for electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional solder bump-forming process is used, then electrical connections can be formed, but fine-pitch bumps with pitch of 100 μm or less cannot be formed
Solution Approach 1:
The metal particles automatically self-assemble between the electrode pads through capillary action during the underfill process, eliminating the need for separate bump formation equipment and processes. The particles move themselves to the correct positions based on the liquid flow field created by the underfill resin, achieving fine-pitch connections without additional manufacturing steps.
Solution Approach 2:
The invention combines the bump formation process with the underfill application process into a single step. The metal particles are mixed with the underfill resin beforehand, so that when the underfill is applied, it simultaneously performs both the gap-filling function and the bump formation function, thereby improving productivity while achieving fine-pitch connections.
2Reliability
If a large number of bumps are formed to accommodate high pin-number LSI, then electrical connectivity is improved, but manufacturing cost increases due to reduced productivity
Solution Approach 1:
The metal particles self-assemble to form bumps during the underfill process, eliminating the need for time-consuming separate bump formation steps. This self-organizing behavior allows rapid formation of numerous fine-pitch bumps simultaneously across the entire chip surface, accommodating high pin-count LSIs while maintaining high productivity and reducing manufacturing costs.
3Reliability
If metal particles are dispersed in thermosetting resin adhesive, then electrical connections can be formed, but viscosity increases leading to electrical short circuits and reduced connecting reliability
Solution Approach 1:
The invention uses particles with a melting point lower than the curing temperature of the thermosetting resin. During heating, the particles melt and become mobile, allowing them to move to the electrode pads through capillary action. After the resin cures and solidifies, the particles are fixed in their final positions. This parameter change (solid→liquid→solid) enables reliable bump formation without the viscosity problems associated with dispersed solid particles.
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 allows for the efficient formation of fine-pitch solder joints and underfill resin layers, reducing residual metal particles and improving connecting reliability by maintaining low viscosity during the initial heating phase and promoting convection-assisted self-assembly of metal particles.
Implementation Method 1
the metal particles melt upon heating so that the first component comes in contact with the second component to form a thermoset resin
Implementation Method 2
the convection additive is capable of generating a gas upon heating
Data Source
AI summary
A flip chip mounting process wherein a semiconductor chip and a circuit substrate are electrically interconnected. The process includes the steps of preparing a semiconductor chip on which a first plurality of electrodes are formed and a circuit substrate on which a second plurality of electrodes are formed; supplying a composition onto a surface of the circuit substrate, such surface being provided with second plurality of electrodes; bringing the semiconductor chip into contact with a surface of said composition such that the first plurality of electrodes are opposed to the second plurality of electrodes; and heating the circuit substrate, and thereby electrical connections including a metal component constituting the metal particles dispersed in the composition are formed between the first plurality of electrodes and the second plurality of electrodes. Also, a thermoset resin layer is formed between the semiconductor chip and the circuit substrate.