Dual Cure Epoxy Adhesive for Low-Temperature Packaging
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Solution Overview
Problem
Current dual cure adhesives for semiconductor and optoelectronic packaging lack a commercially available, all epoxy formulation that is curable both photochemically and thermally at low temperatures, making them incompatible with temperature-sensitive components like polycarbonate lenses, and are prone to gelation at room temperature, complicating handling and storage.
Innovation Solution
A dual cure, all epoxy adhesive composition comprising at least 93% polymerizable epoxides, a photo-acid generator for UV-induced acid-catalyzed polymerization, a redox agent, and a thermal acid generator for heat-induced polymerization, allowing for stable storage and low-temperature curing, specifically using copper(II), iron(III), or titanium(IV) salts as redox agents to control reactivity and extend storage life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high reactivity epoxy resin compositions are used to enable fast curing, then curing speed is improved, but storage stability deteriorates due to gelation at room temperature
Solution Approach 1:
The patent changes the chemical parameters of the epoxy resin composition by selecting specific epoxide compounds with controlled reactivity and using catalytic amounts of acid generators that remain dormant until activated by UV light or heat, thereby achieving fast curing when needed while maintaining storage stability
Solution Approach 2:
The patent introduces UV light and heat as intermediary activation mechanisms that trigger the curing process only when applied, allowing the adhesive to remain stable during storage and handling but cure rapidly when exposed to these external stimuli
2Reliability
If high temperature thermal curing is used to achieve complete epoxy polymerization, then curing completeness is improved, but damage to temperature-sensitive components worsens
Solution Approach 1:
The patent employs a two-stage curing process where UV light initiates polymerization first, followed by low-temperature thermal treatment to complete the curing, replacing the need for high-temperature single-stage curing and thereby protecting temperature-sensitive components
Solution Approach 2:
The patent performs preliminary UV curing to initiate the polymerization process and achieve sufficient bond strength before applying low-temperature thermal treatment, allowing the adhesive to set in place sensitive components before final curing
3Adaptability or versatility
If hybrid resin formulations containing acrylates and epoxies are used to enable dual cure, then dual curing capability is improved, but adhesion performance and environmental resistance worsen compared to pure epoxy
Solution Approach 1:
The patent makes pure epoxy resin universal by enabling it to undergo both photochemical polymerization (when exposed to UV light) and thermal polymerization (when heated), eliminating the need for hybrid formulations while maintaining superior adhesion and environmental resistance
Solution Approach 2:
The patent uses homogeneous pure epoxy resin composition throughout the formulation, avoiding the heterogeneity of hybrid systems, which ensures consistent adhesion performance and environmental resistance while achieving dual curing capability through the epoxy's ability to polymerize via both UV and heat activation
Data Source
AI summary
A dual cure, all epoxy adhesive that is both photochemically and thermally curable is disclosed. The adhesive may comprise at least about 93% by weight of one or more polymerizable epoxides, a catalytic amount of a photo-acid generator (PAG) configured to induce acid-catalyzed polymerization of the polymerizable epoxide when exposed to UV or visible light, about 0.01% to about 1% by weight of a redox agent, and a catalytic amount of a thermal acid generator (TAG) configured to induce acid-catalyzed polymerization of the polymerizable epoxide in the presence of the redox agent when exposed to a temperature at or above about 70° C.