Electrically Conductive Silicone Composition for Thermal-Cycling Adhesion
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Solution Overview
Problem
Existing electrically conductive adhesives for solar cells and photovoltaic modules lack sufficient mechanical properties and adhesion strength to withstand temperature changes and mechanical stresses, leading to reduced module efficiency and lifetime.
Innovation Solution
An electrically conductive silicone composition comprising a silicone resin with vinyl groups, a silicone cross-linker with Si-H groups, conductive particles, a solvent, an adhesion promoter, and a catalyst, with a specific ratio of Si-H to vinyl groups, to provide high adhesion strength and electrical stability under varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrically conductive adhesives are used to bond solar cells, then electrical conductivity is achieved, but adhesion strength and mechanical durability are insufficient under thermal cycling and mechanical stress
Solution Approach 1:
The patent employs a composite adhesive system combining epoxy resin (for strong adhesion and mechanical properties) with silicone resin (for flexibility and thermal stability), along with conductive particles. This composite formulation achieves both high adhesion strength and mechanical durability while maintaining electrical conductivity, resolving the contradiction between reliability and strength.
Solution Approach 2:
The patent optimizes the ratio of Si-H groups to vinyl groups (1.05:1 to 1.2:1) and adjusts the proportions of epoxy resin, silicone resin, and conductive particles to achieve the desired balance between adhesion strength and mechanical durability. By precisely controlling these parameters, the adhesive maintains both high reliability and strength under thermal and mechanical stress.
2Strength
If the adhesive is made more rigid to withstand mechanical stress, then mechanical strength improves, but electrical stability under thermal cycling deteriorates
Solution Approach 1:
The combination of rigid epoxy resin (providing mechanical strength) with flexible silicone resin (maintaining electrical stability) creates a composite adhesive that exhibits both high mechanical strength and excellent electrical stability under thermal cycling. The silicone component's flexibility compensates for the rigidity of epoxy, preventing brittleness while maintaining structural integrity.
Solution Approach 2:
The patent carefully controls the ratio of epoxy resin to silicone resin, as well as the cross-linker to vinyl-group ratio, to achieve the optimal balance between mechanical strength and electrical stability. This parameter optimization ensures the adhesive remains mechanically strong while maintaining flexibility for electrical stability during thermal cycling.
3Reliability
If the ratio of Si-H to vinyl groups is increased to improve cross-linking density, then adhesion strength improves, but electrical conductivity may be compromised
Solution Approach 1:
The patent optimizes the Si-H to vinyl group ratio within a specific range (1.05:1 to 1.2:1) to achieve sufficient cross-linking density for strong adhesion while maintaining adequate electrical conductivity. This controlled parameter adjustment ensures both high reliability and sufficient electrical performance without excessive cross-linking that would compromise conductivity.
Solution Approach 2:
The composite formulation including conductive particles (silver, carbon, or nickel) compensates for any reduction in conductivity due to increased cross-linking. The conductive particles maintain electrical pathways while the cross-linked polymer matrix provides strong adhesion, resolving the trade-off between adhesion strength and electrical conductivity.
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 stable electrical contact and improved mechanical durability, maintaining performance through thermal cycling and humidity, with balanced adhesion and conductivity, suitable for shingled photovoltaic modules.
Implementation Method 1
a silicone resin (a) comprising at least one vinyl-group; b) a silicone cross-linker (b) having at least one Si—H group
Implementation Method 2
c) electrically conductive particles (c)
Data Source
AI summary
The present invention relates to an electrically conductive composition comprising a silicone resin comprising at least one vinyl-group; a silicone cross-linker having at least one Si—H group; electrically conductive particles; a solvent; an adhesion promoter; a catalyst; and an inhibitor, wherein ratio between Si—H groups and vinyl-groups is equal or greater than 1.3 but equal or less than 10.