Porous Bump-Forming Material for Narrow Pitch Substrate Bonding
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Solution Overview
Problem
The challenge in electronic component mounting is the deformation and disconnection of substrates due to thermal expansion stress, particularly at narrow pitches, where traditional methods face difficulties in filling underfill agents and maintaining bump shape for fine fabrication.
Innovation Solution
A bump-forming material comprising a base resin, solvent, foaming agent, and photosensitizer is used, which forms a porous film upon heating, allowing for expansion and filling the gap between substrates without deformation, enhancing mechanical strength and bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional reflow process with metal bumps is used, then electrical connection is achieved, but the large diameter of bumps hinders development of narrow pitches
Solution Approach 1:
The patent changes the physical and chemical parameters of the bump material by using an organic resin composition with foaming agents and photosensitizers instead of traditional metal alloys. This allows the bump diameter to be reduced to 50-200 μm while maintaining structural integrity through controlled foaming and curing processes
Solution Approach 2:
The invention uses a composite organic resin material comprising base resin, foaming agent, photosensitizer, and solvent. This composite structure enables the bump to achieve both small diameter for narrow pitch and sufficient mechanical strength through the synergistic effects of the components
2Reliability
If underfill agent is poured after reflow process, then stress between substrates is reduced, but it is difficult to pour material due to small gap at narrow pitch
Solution Approach 1:
The patent applies the underfill agent to the chip surface before bonding (first-in method) rather than after bonding. The agent is then expanded in-situ through foaming during the bonding process, eliminating the need for post-bonding pouring and solving the narrow gap filling problem
Solution Approach 2:
The underfill agent undergoes phase transition from liquid to foam through thermal expansion during the bonding process. This volume expansion allows the material to fill the gap between substrates effectively, achieving stress reduction without requiring post-bonding pouring operations
3Strength
If bumps are pressed and heated (reflow process), then bumps are bonded together, but bumps remain spherical which hinders fine fabrication
Solution Approach 1:
The patent changes the shape parameter of bumps from spherical to rectangular through controlled expansion of the foaming agent during curing. The rectangular shape is achieved by configuring the mold cavity and controlling the foaming process, enabling fine fabrication while maintaining bonding strength
Solution Approach 2:
The bump structure incorporates a porous interior formed by the foaming agent, creating a rectangular outer shape with internal voids. This porous structure reduces material usage and enables precise shape control for fine pitch applications while maintaining sufficient mechanical strength for bonding
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 material effectively reduces stress between substrates by forming a porous film that fills gaps, ensuring strong bonding and reliable semiconductor devices with reduced electrical resistance and improved thermal cycling performance.
Implementation Method 1
a foaming agent and a photosensitizer, and/or a substance that serves as a foaming agent and a photosensitizer
Implementation Method 2
a foaming agent and a photosensitizer, and/or a substance that serves as a foaming agent and a photosensitizer
Implementation Method 3
the vicinity of bumps is filled with an underfill agent 103 (organic resin material) after the reflow process
Data Source
AI summary
A material includes a base resin; a solvent; and a foaming agent and a photosensitizer, and/or a substance that serves as a foaming agent and a photosensitizer.