Thermochromic Epoxy Coatings for Stray Light Control
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Solution Overview
Problem
Current materials fail to simultaneously achieve high transparency for radiation-induced curing and opacity for deep encapsulation in camera modules and chip encapsulation, leading to issues with light scattering and reliability under temperature changes.
Innovation Solution
A method using a curable epoxy-based composition with a reversible thermochromic component that transitions from transparent to opaque by controlling temperature and actinic radiation, allowing for a single process step to achieve opacity without complex measures, utilizing a heat-latent acid generator to enhance the color change and polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If opaque encapsulation material is used to minimize stray light, then light transmission is reduced, but irradiability for deep encapsulation and alignment processes is prevented
Solution Approach 1:
The encapsulation material's optical properties are made dynamic through temperature-dependent reversible thermochromic dyes. The material transitions from opaque at room temperature to transparent at elevated temperatures (e.g., 60-80°C), enabling irradiability during alignment processes and providing opacity during operation to minimize stray light. This dynamic property resolution allows the same material to satisfy both contradictory requirements at different stages.
Solution Approach 2:
The optical transmission parameter of the encapsulation material is changed by controlling temperature. During active alignment, the material is heated to raise its optical transmission above a first threshold, enabling sufficient irradiability. During normal operation, the material cools to below the threshold, achieving high opacity to minimize stray light. This parameter change through temperature control resolves the contradiction between opacity and irradiability.
2Object-affected harmful factors
If opaque coatings are applied to minimize stray light, then additional process steps are required, but manufacturing complexity increases
Solution Approach 1:
The invention merges the opacity function (to minimize stray light) with the encapsulation material itself rather than requiring separate opaque coatings. The reversible thermochromic encapsulation material provides both structural encapsulation and optical control functions in a single component, eliminating additional process steps for applying separate opaque layers while still achieving stray light minimization during operation.
Solution Approach 2:
The encapsulation material performs multiple functions: it provides mechanical protection, thermal management, and dynamic optical control. The reversible thermochromic property enables the same material to provide opacity when needed (minimizing stray light) and transparency when needed (allowing irradiation for curing and alignment), eliminating the need for separate functional layers or process steps.
3Reliability
If irreversible thermochromic dyes are used to indicate curing progress, then color change is permanent, but the material cannot return to transparent state for inspection
Solution Approach 1:
The invention uses reversible thermochromic dyes that dynamically change optical properties based on temperature. During curing, the material transitions to an opaque state providing reliable curing indication. After curing, the material can be heated to return to a transparent state, enabling optical inspection of the cured product. This reversibility resolves the contradiction between permanent curing indication and post-curing inspection capability.
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 method ensures a stable opaque state with reduced light scattering, maintaining alignment and reliability across temperature changes, while allowing for easy quality inspection and flexible application in various components.
Implementation Method 1
the curable mass which is transmissible above a first temperature and which contains a reversible thermochromic component... Heating the curable mass to at least a second temperature above the first temperature sufficient to induce a color change of the thermochromic component
Implementation Method 2
Exposing the curable mass in the transmissible state to actinic radiation of a suitable wavelength at the second temperature to initiate a polymerization reaction
Implementation Method 3
utilizing a heat-latent acid generator to enhance the color change and polymerization
Data Source
AI summary
The invention relates to a method for producing an opaque potting compound, bond, or coating using a curable mass that is transmissible to radiation above a first temperature and contains a reversible thermochromic component, wherein the method comprises the following steps: a) metering the curable mass onto a first substrate; b) selectively adding a second substrate to the curable mass; c) heating the curable mass to at least a second temperature above the first temperature sufficient to induce a color change of the thermochromic component to a transmissible state; d) exposing the curable mass in the transmissible state to actinic radiation of a suitable wavelength at the second temperature to initiate a first polymerization reaction; and e) cooling the cured mass to or below the first temperature.and wherein the curable mass is an epoxy-based mass curable by cationic polymerization. Furthermore, a curable mass for use in the process is described.