Bonding Sheet Composition for Uniform Solder Self-Aggregation
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Solution Overview
Problem
Existing bonding sheets with solder particles of 7.1 μm average size result in uneven self-aggregation, leading to reduced reliability in connecting terminals of wiring circuit boards.
Innovation Solution
A bonding sheet with solder particles having an average primary and secondary particle size of 7 μm or less, combined with a resin component that includes a thermoplastic resin with a softening point of 110°C or more and a viscosity of 5000 mPa·s or less, and optionally flux, to ensure uniform aggregation and improved reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder particles with average particle size of 7.1 μm are used in the bonding sheet, then the bonding sheet can be manufactured with conventional processes, but uneven self-aggregation occurs leading to reduced reliability
Solution Approach 1:
The patent applies parameter changes by strictly controlling the solder particle size distribution with both average primary and secondary particle sizes at 7 μm or less. This parameter optimization ensures uniform melting behavior and self-aggregation during the bonding process, eliminating the uneven aggregation that occurs with larger 7.1 μm particles while maintaining compatibility with conventional manufacturing processes.
2Reliability
If the resin component has low viscosity at solder melting point, then the solder particles can aggregate uniformly, but the resin may flow excessively during bonding
Solution Approach 1:
The patent applies parameter changes by optimizing the resin component's viscosity to 5000 mPa·s or less at the solder melting point. This viscosity parameter is carefully controlled to balance two requirements: low enough to allow uniform solder particle aggregation and movement, but high enough to prevent excessive resin flow that would compromise bonding stability and composition integrity.
3Stability of the object's composition
If a thermoplastic resin with softening point of 110°C or more is used, then the bonding sheet maintains structural integrity at operating temperatures, but the resin remains solid at room temperature reducing processability
Solution Approach 1:
The patent applies phase transitions by selecting a thermoplastic resin with a softening point of 110°C or more. The resin exists in a solid state at room temperature (25°C) providing structural integrity and stability, but transitions to a softened or melted state during the bonding process at elevated temperatures, enabling proper flow, wetting, and aggregation uniformity without compromising ease of manufacture.
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 enhances the reliability of connections by suppressing uneven self-aggregation, reducing the risk of short-circuits and connection failures, thereby improving the overall bonding process.
Implementation Method 1
the bonding sheet is heated. Thus, solder particles included in the bonding sheet are melted, and gather between the first electrode and the second electrode (self-aggregation), thereby forming a solder portion which electrically connects the first electrode to the second electrode
Implementation Method 2
solder particles included in the bonding sheet are melted, and gather between the first electrode and the second electrode (self-aggregation)
Implementation Method 3
the resin component includes a thermoplastic resin, and the thermoplastic resin has a softening point of 110° C. or more
Data Source
AI summary
A bonding sheet includes a resin component and a solder particle. Both an average primary particle size of the solder particle and an average secondary particle size of the solder particle are 7 μm or less.