Heat Stable Aryl Polysiloxane for LED Encapsulation
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Solution Overview
Problem
Current encapsulants for high-intensity LEDs, such as epoxy polymers, undergo unacceptable yellowing and degradation under long-term and high-temperature conditions, and aryl polysiloxanes are unsuitable due to yellowing and brown discoloration during accelerated heat aging, which affects the light efficiency and reliability of LEDs.
Innovation Solution
A curable aryl siloxane composition comprising an aryl vinyl polysiloxane, a hydrido silicon compound, and a hydrosilation catalyst with a Group VIII element (like platinum, rhodium, or palladium) at specific concentrations, which upon curing forms a heat-stable cured aryl polysiloxane that does not discolor during accelerated heat aging at 200°C in air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If aryl groups are attached to silicon atoms to increase refractive index, then light flow efficiency is improved, but yellowing and discoloration occur during heat aging
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating specific aryl groups (phenyl, naphthyl, phenoxyphenyl) at controlled proportions (at least 10 mole percent silicon bonded aryl groups) to adjust refractive index while maintaining heat stability. This resolves the contradiction by finding an optimal parameter range that achieves both high light flow efficiency and resistance to yellowing during heat aging.
Solution Approach 2:
The patent creates a composite aryl polysiloxane material that combines aryl-substituted silicon units with other silicon units in a polymeric structure. This composite approach allows the material to achieve the desired refractive index for efficient light flow while the overall composite structure resists degradation and discoloration under heat aging conditions.
2Ease of manufacture
If epoxy polymers are used as encapsulants, then manufacturing compatibility is maintained, but yellowing and degradation occur under high temperature conditions
Solution Approach 1:
The patent transitions from epoxy polymer chemistry to aryl polysiloxane chemistry, fundamentally changing the material composition parameters. This chemical parameter change enables the encapsulant to withstand high temperature conditions (100°C-200°C) for extended periods (10,000-100,000 hours) without yellowing or degradation, while still being compatible with LED encapsulation manufacturing processes.
3Reliability
If methyl substituted polysiloxanes are used, then resistance to degradation is improved, but refractive index is too low for efficient light flow
Solution Approach 1:
The patent modifies the polysiloxane structure by substituting at least 10 mole percent of the silicon-bonded organic groups with aryl groups (such as phenyl, naphthyl, or phenoxyphenyl). This compositional parameter change increases the refractive index from the typical 1.41 of methyl polysiloxanes to a range of 1.5-1.62, enabling efficient light flow while maintaining the degradation resistance characteristic of polysiloxanes.
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 provides a heat-stable and non-discoloring cured aryl polysiloxane composition that maintains optical clarity and efficiency, ensuring the longevity and performance of high-intensity LEDs under stringent operating conditions.
Implementation Method 1
a curable aryl siloxane composition including an aryl vinyl polysiloxane and a hydrido silicon compound, and a hydrosilation catalyst
Implementation Method 2
a hydrosilation catalyst present in an amount of at least 0.005 ppm to no more than 3.0 ppm, expressed as a Group VIII element equivalent value
Data Source
AI summary
A curable aryl siloxane composition is disclosed. A heat stable cured aryl polysiloxane composition is further disclosed, along with a method of making that heat stable cured aryl polysiloxane composition from the curable aryl siloxane composition. An encapsulated semiconductor device, and a method of making that encapsulated semiconductor device by coating a semiconductor element of a semiconductor device with the heat stable cured aryl polysiloxane are further disclosed.