Snap-Cure Conductive Epoxy Adhesive for Flexible Solar Cell Bonding
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Solution Overview
Problem
Conventional electrically conductive adhesives used in photovoltaic modules face challenges such as high resistive losses, differential thermal contraction, stress, and micro-cracks due to soldering processes, and require faster cure times and lower cure temperatures to ensure high throughput and mechanical reliability, while maintaining flexibility and adhesion.
Innovation Solution
A snap-cure flexible electrically conductive one-component epoxy adhesive composition comprising cycloaliphatic epoxide resin, vinyl ether, onium salt, radical initiator, electrically conductive particles, and organic solvent, which provides low electrical contact resistance, high flexibility, and strong adhesion to metallization parts of silicon solar cells, allowing for rapid curing at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional electrically conductive adhesives are used in photovoltaic modules, then electrical connection is achieved, but resistive losses are high and cure time is long
Solution Approach 1:
The patent modifies the chemical composition parameters of the adhesive by incorporating specific conductive fillers (silver particles, carbon nanotubes, or graphene) in optimized concentrations (5-85 wt%), along with cycloaliphatic epoxy resins and curatives. These parameter changes enable simultaneous achievement of low electrical resistance and rapid curing through the synergistic interaction of components
Solution Approach 2:
The invention creates a composite adhesive material combining organic matrix (cycloaliphatic epoxy resin with molecular weight 350-500 g/mol), conductive fillers (metallic or carbon-based), and curative agents. This composite structure integrates the adhesive properties of the polymer matrix with the high electrical conductivity of the filler particles, resolving the contradiction between electrical performance and curing characteristics
2Strength
If soldering process is used to attach ribbons to busbars, then strong electrical connection is achieved, but thermal stress and micro-cracks occur due to differential thermal contraction
Solution Approach 1:
The patent replaces the mechanical soldering process with a chemical adhesive bonding system. The adhesive composition forms a flexible, electrically conductive bond that accommodates thermal expansion differences between dissimilar materials (silicon, glass, metal) through its viscoelastic properties, eliminating the brittle failure mode inherent in rigid solder joints while maintaining electrical connectivity
Solution Approach 2:
The invention changes the bonding mechanism from metallurgical bonding (soldering) to polymeric chemical bonding. The adhesive's molecular structure (cycloaliphatic epoxy with specific molecular weight range) provides both strong adhesion and thermal flexibility, with the glass transition temperature and crosslink density optimized to maintain mechanical integrity across the operating temperature range of photovoltaic modules
3Productivity
If fast curing is implemented to ensure high throughput, then productivity increases, but adhesion strength and flexibility may be compromised
Solution Approach 1:
The adhesive is formulated with pre-selected components that enable rapid curing without sacrificing final bond strength. The cycloaliphatic epoxy resin is chosen for its inherently fast reaction kinetics, and the curative system is optimized to provide immediate gelation followed by complete curing, achieving both high throughput and strong adhesion through preliminary chemical design
Solution Approach 2:
The patent optimizes the molecular weight of the cycloaliphatic epoxy resin (350-500 g/mol) and the ratio of resin to curative (90:10 to 50:50 wt%) to balance cure speed and adhesion. The conductive filler content (5-85 wt%) is also optimized to maintain electrical conductivity during rapid curing while ensuring sufficient polymer matrix remains to provide bonding strength and flexibility
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 composition achieves rapid curing within 10-60 seconds at 120-200°C, ensuring high throughput and mechanical reliability, with improved adhesion and reduced resistive losses, effectively addressing the limitations of conventional adhesives in photovoltaic module assembly.
Implementation Method 1
comprising a) from 5 to 25% by weight of the total weight of the composition of a cycloaliphatic epoxide resin; b) from 0.05 to 10% by weight of the total weight of the composition of a vinyl ether; d) from 0.01 to 10% by weight of the total weight of the composition of a radical initiator
Implementation Method 2
c) from 0.1 to 0.45% by weight of the total weight of the composition of an onium salt
Data Source
Figure 1a~2
Figure 3
AI summary
The present invention relates to an electrically conductive composition comprising a) from 5 to 25% by weight of the total weight of the composition of a cycloaliphatic epoxide resin; b) from 0.05 to 10% by weight of the total weight of the composition of a vinyl ether; c) from 0.1 to 0.45% by weight of the total weight of the composition of an onium salt; d) from 0.01 to 10% by weight of the total weight of the composition of a radical initiator; e) from 45 to 85% by weight of the total weight of the composition of electrically conductive particles; and f) from 0.1 to 10% by weight of the total weight of the composition of an organic solvent. The composition can be used as an adhesive in the electronic applications, especially as an adhesive in the shingle module photovoltaic applications