Photoinitiated Adhesive Composition for Uniform Internal Curing
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Solution Overview
Problem
Conventional photoinitiators for polymer curing require direct line-of-sight access to a light source, limiting their use in applications like multilayer silicon die assembly and adhesive bonding where internal curing is necessary, and often result in skin formation rather than uniform curing.
Innovation Solution
The development of polymer formulations with photoinitiators and energy converters that can be activated indirectly, allowing for ambient temperature curing across the entire adhesive volume without line-of-sight access to an external energy source, using materials like down-converting phosphors to convert radiation into activating wavelengths for photoinitiators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional photoinitiators are used for polymer curing, then curing can occur at ambient temperature, but direct line-of-sight access to light source is required which prevents internal curing of complex geometries
Solution Approach 1:
The patent introduces an intermediary substance (phosphor material) that converts external radiation into UV light locally within the adhesive. This phosphor acts as a mediator between the external radiation source and the photoinitiator, enabling curing in locations where direct light access is impossible such as internal surfaces and complex geometries.
Solution Approach 2:
The patent replaces the direct optical mechanism (light traveling in straight lines) with an indirect energy conversion mechanism. Instead of relying on photons to directly reach and activate photoinitiators, the system uses radiation-to-UV conversion through phosphors, substituting the mechanical/optical path requirement with a chemical energy conversion process.
2Temperature
If conventional UV curing is used, then ambient temperature curing is achieved, but skin formation occurs instead of uniform volume curing
Solution Approach 1:
The patent applies local quality by distributing phosphor particles throughout the adhesive volume, creating localized UV generation centers throughout the entire adhesive bead. This ensures uniform curing throughout the volume rather than surface-only curing, as each local region generates its own UV activation energy independently.
Solution Approach 2:
The phosphor material serves as an intermediary that distributes UV energy uniformly throughout the adhesive volume. By converting radiation to UV light at multiple distributed points within the adhesive, the system achieves uniform volumetric curing without the skin formation problem that occurs with surface-only UV exposure.
3Strength
If thermal curing is used for thermosetting adhesives, then strong bonds are formed, but high temperatures cause thermal stress and damage to temperature-sensitive components
Solution Approach 1:
The patent replaces thermal energy with radiant energy for the curing process. Instead of using heat to activate the photoinitiator and drive polymerization, the system uses radiation that is converted to UV light by phosphors, enabling curing at ambient temperature while maintaining the chemical crosslinking and bond strength of thermosetting adhesives.
Solution Approach 2:
The patent changes the activation parameter from thermal energy to radiant energy. By using radiation-to-UV conversion through phosphors, the system activates photoinitiators at ambient temperature rather than requiring elevated temperatures, thus achieving the same curing effect without thermal stress on sensitive components.
4Temperature
If UV light is used for curing, then ambient temperature processing is achieved, but line-of-sight access is required which limits application to simple geometries
Solution Approach 1:
The phosphor material acts as an intermediary that eliminates the line-of-sight requirement. By converting external radiation into UV light locally within the adhesive at the point of application, the system can cure adhesives on complex geometries, internal surfaces, and in tight spaces where direct light access is impossible.
Solution Approach 2:
The patent transitions from a surface-level UV curing approach to a volumetric curing approach by distributing phosphors throughout the adhesive. This enables curing in three-dimensional spaces and complex geometries rather than being limited to surface areas accessible to direct light.
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
Enables controlled, uniform curing of adhesives across complex geometries and internal surfaces, improving bond strength and reducing thermal stress, while allowing for bonding on low-energy substrates without the need for external light exposure.
Implementation Method 1
irradiating the assembly with radiation at a first wavelength, capable of conversion by the at least one energy converting material, to a second wavelength capable of activating the photoinitiator
Implementation Method 2
these systems employ at least one photoinitiator, which, when exposed to UV light, releases chemical energy to form free radicals or cations to initiate the reaction of the monomers
Data Source
Figure 1A~1B
Figure 1C
Figure 1D~2A
AI summary
A method of and system for adhesive bonding. The method and system a) treat a surface of an element to be bonded to provide an adherent structure including one or more rubber compounds on the surface; b) place a polymerizable adhesive composition, including at least one photoinitiator and at least one energy converting material, in contact with the adherent structure and two or more components to be bonded to form an assembly, c) irradiated the assembly with radiation at a first wavelength, capable of conversion by the at least one energy converting material, to a second wavelength capable of activating the at least one photoinitiator to produce from the polymerizable adhesive composition a cured adhesive composition; and d) adhesively join the two or more components by way of the adherent structure and the cured adhesive composition.