Self-Assembling Solder Bumps for Flip-Chip Electrical Continuity
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Solution Overview
Problem
Conventional flip-chip packaging using anisotropic conductive materials faces challenges in ensuring stable electrical continuity and process control, particularly for next-generation LSI chips with high-pin-count connection terminals, due to mechanical contact issues and difficulties in controlling the properties of thermosetting resin and conductive particles.
Innovation Solution
A package and production method involving self-assembly of solder bumps using a solder resin paste with solder powders and a convection-inducing additive, where the solder powders are dispersed in resin and accumulate on an electrode pattern, allowing for selective solder accumulation and preventing short circuits, while the convection-inducing additive generates convection to facilitate uniform solder formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anisotropic conductive materials are used for flip-chip packaging, then electrical connection between chip and substrate is achieved, but stable electrical continuity cannot be ensured due to mechanical contact issues
Solution Approach 1:
The patent replaces the mechanical contact-based anisotropic conductive material system with a self-assembling solder bump system. The solder bumps form through self-assembly during the flip-chip bonding process, eliminating the need for mechanical contact through conductive particles in resin. This substitution provides stable electrical continuity through direct metallurgical bonding rather than mechanical contact.
Solution Approach 2:
The solder bumps perform dual functions: they provide electrical connection and simultaneously serve as bonding agents for fixing the chip to the substrate. The self-assembly process allows the solder to automatically form connections without additional bonding steps, simplifying the overall process while improving reliability.
2Manufacturing precision
If solder paste is applied entirely over substrate to form bumps, then fine-pitch bumps can be formed, but productivity is reduced due to complicated process
Solution Approach 1:
The solder paste formulation includes additives that enable self-alignment and self-assembly of solder bumps during the bonding process. The solder automatically positions itself on the connection terminals through capillary action and surface tension effects, eliminating the need for complex mask alignment processes while maintaining fine-pitch formation capability.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the solder paste by adding specific additives that change its flow characteristics, surface tension, and reactivity. These parameter changes enable the solder to self-assemble into precise bumps during heating, achieving both fine-pitch precision and high productivity through a simplified process.
3Manufacturing precision
If chemical deposition type solder is used for fine bump formation, then fine-pitch design is achieved, but flexibility in solder composition selection is reduced
Solution Approach 1:
The patent uses solder paste with controlled particle size distribution and added additives that enable fine bump formation through self-assembly. This approach allows flexibility in selecting different solder compositions (including Pb-free options) while maintaining precise bump size control, as the fine-pitch capability comes from the self-assembly process rather than being constrained by specific chemical deposition reactions.
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 provides a highly reliable and high-productivity package by preventing electrical short circuits and ensuring stable electrical connections, while allowing for flexible solder composition and improved process control, even with high-density connection terminals.
Implementation Method 1
the convection-inducing additive generates convection to facilitate uniform solder formation
Implementation Method 2
the electrode terminals on the mounting substrate and the electrode terminals are electrically connected collectively by solder bumps formed in self-assembly
Data Source
AI summary
A highly reliable, high-productivity package equipped with a semiconductor chip, and a method for producing the same. In a package (100) comprising a semiconductor chip (10) and a mounting substrate (30), a plurality of electrode terminals (12) are formed on the surface (10a) of the semiconductor chip (10) opposing the mounting substrate side, connection terminals (32) respectively corresponding to the plurality of electrode terminals (12), are formed on the mounting substrate (30), the connection terminals (32) on the mounting substrate (30) and the electrode terminals (12) are electrically connected collectively by solder bumps (17) formed in self-assembly, an electrode pattern (20) not connected with the electrode terminals (12) and the connection terminals (32) is formed on the chip surface (10a) or the surface (35) of the mounting substrate (30) corresponding to the chip surface (10a), and solder (19) is accumulated on the electrode pattern (20).