Glassy Adhesive UV Resistance Reflow Cracking
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Solution Overview
Problem
Current adhesives for UV-LEDs face challenges with UV resistance, cost, and reliability, particularly experiencing cracks and voids after reflow processes due to degradation from UV irradiation and thermal stress.
Innovation Solution
A glassy adhesive composition comprising a polysilazane compound with specific structures (A-1 and A-2) and a curing catalyst, such as citric acid or organic aluminum compounds, is developed, which does not contain hydrosilyl groups and has a non-volatile content of 50% or more after heating, ensuring high UV resistance and adhesion strength at low temperatures without defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If condensation-curing silicone resin is used to improve UV resistance by eliminating carbon-carbon bonds, then UV resistance is improved, but water and alcohol eliminated during condensation reaction cause cracks and voids when evaporating and increasing in volume during reflow process
Solution Approach 1:
The patent extracts and eliminates the problematic eliminated components (water and alcohol) from the condensation reaction system by using a different curing mechanism (addition reaction) that does not produce small molecule byproducts, thereby solving the crack and void formation issue while maintaining UV resistance
Solution Approach 2:
The patent changes the curing reaction type from condensation reaction to addition reaction, fundamentally altering the reaction parameters to eliminate the production of water and alcohol, thus preventing the volume expansion and subsequent defects during reflow processing
2Ease of manufacture
If addition-curing silicone resin is used to simplify the curing mechanism, then ease of manufacture is improved, but carbon-carbon bonds remain in the cured resin causing degradation under UV irradiation
Solution Approach 1:
The patent uses a composite curing system combining addition reaction and condensation reaction in a specific ratio, where the addition reaction provides ease of manufacture while the condensation reaction eliminates carbon-carbon bonds to improve UV resistance, achieving both benefits simultaneously
3Quantity of substance
If epoxy resin is used as encapsulant to reduce cost, then cost is reduced, but photo-degradation occurs under UV irradiation and thermal degradation occurs from heat generation
Solution Approach 1:
The patent changes the chemical composition parameters of the encapsulant from epoxy resin to silicone resin with specific molecular structure (low carbon-carbon bond content), fundamentally improving UV and heat resistance while maintaining cost-effectiveness through optimized formulation
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 adhesive provides high UV resistance, prevents cracks and voids, and maintains adhesion strength even after reflow processes, while being cost-effective and suitable for low-temperature applications.
Implementation Method 1
Curing of silicone resin is usually made to proceed by making vinyl groups and hydrosilyl groups in the resin bond with each other by an addition reaction. Therefore, carbon-carbon bonds remain in the resin after the reaction, and degradation progresses by the above-described mechanism. On the other hand, the condensation reaction cures the resin by condensing hydroxy groups and alkoxy groups with each other, and therefore, has a characteristic that carbon-carbon bonds do not remain in the cured resin.
Implementation Method 2
a curing catalyst, wherein a mole ratio of the component (A-1) to the component (A-2), which is (A-1):(A-2), is within a range of 3:7 to 7:3, the composition has a non-volatile content of 50 mass % or more, when the composition being heated at 105° C. for 3 hours, and the curing catalyst is at least one selected from the group consisting of an organic acid, a simple substance of a d block element belonging to the fourth period of the periodic table, a platinum group element, and an amphoteric element, and a compound containing the element
Implementation Method 3
Silicone resin has few carbon-carbon bonds, which constitute the main chain of organic resins such as epoxy resin, and mainly has siloxane bonds, Si—O—Si, which are more resistant to light and heat. Therefore, silicone resin has good light resistance and heat resistance
Implementation Method 4
These radicals newly form crosslinking bonds, so that the silicone resin rapidly hardens. Finally, cracks occur so that the silicone resin no longer functions as an encapsulant.
Data Source
AI summary
A glassy adhesive including a composition containing at least: a polysilazane compound having structures represented by the following formulae (A-1) and (A-2) and not containing a hydrosilyl group; and a curing catalyst, where a mole ratio of the component (A-1) to the component (A-2), which is (A-1):(A-2), is within a range of 3:7 to 7:3, the composition has a non-volatile content of 50 mass % or more, when the composition being heated at 105° C. for 3 hours, and the curing catalyst is at least one selected from the group consisting of an organic acid, a simple substance of a d block element belonging to the fourth period of the periodic table, a platinum group element, and an amphoteric element, and a compound containing the element. This provides an adhesive that is low-cost, has high UV resistance, and in which cracks and so forth do not occur even after a reflow process.