Preface

The global high-end manufacturing industry is rapidly evolving toward miniaturization, precision, high-speed automation, low pollution and high reliability. With the advantages of solvent-free formulation, fast curing speed, low energy consumption and high forming accuracy, UV-curable adhesives have become an indispensable core material system for precision assembly, temporary wafer bonding, optical bonding and device sealing protection. As a classic and continuously upgraded photosensitive core component in UV adhesive formulations, benzophenone photoinitiators feature broad-spectrum ultraviolet absorption, outstanding surface curing performance and excellent compatibility with acrylate resins. When combined with co-initiators, they can efficiently generate free radicals to drive cross-linking reactions of resins. Newly developed benzophenone derivatives modified by structural optimization and high-purification treatment effectively mitigate traditional drawbacks including small-molecule migration, odor and yellowing. Customizable grades such as high-purity, low-migration and low-yellowing products are available for diverse application scenarios. They are widely adopted in seven high-end sectors: advanced semiconductor packaging, optical communication & AI computing power, automotive electronics, new energy & energy storage, aerospace & rail transit, medical & life sciences, industrial equipment and general industry, providing critical raw material support for the domestic substitution of the UV adhesive industrial chain.

I. Semiconductors and Advanced Packaging

Advanced semiconductor packaging serves as a core enabler for chip performance improvement. Processes including 2.5D/3D packaging, Chiplet, Fan-out and RDL redistribution impose stringent requirements on matching adhesives: ultra-low metallic ion impurities, low small-molecule leaching, low internal stress, rapid UV curing and superior thermal cycle stability, to avoid wafer contamination, microstructure damage, warpage and delamination. Benzophenone-series photoinitiators applied in UV adhesive systems for the semiconductor field are mainly used for temporary wafer bonding adhesives, wafer protective films, chip edge sealing adhesives, auxiliary adhesives for RDL processes, protective layers for FPC flexible circuit boards, and sealing adhesives around micro-bumps. High-purity benzophenone products strictly control the content of metal ions such as Na, K and Fe to reduce risks of electric leakage and device failure induced by ion migration. Their favorable surface curing capacity addresses surface tackiness of thick adhesive layers under oxygen-deficient environments, matching continuous UV exposure processes in wafer fabrication lines. The cured adhesive layer has controllable shrinkage and low internal stress, maintaining bonding integrity during repeated high-temperature thermal cycling tests and reducing defects such as wafer warpage and interfacial debonding. For heterogeneous integration of multi-chip Chiplet systems, UV adhesives for micro-gap filling and local sealing adopting benzophenone photoinitiation systems enable targeted rapid curing, protect sophisticated micro-interconnection structures and boost yield of advanced packaging, helping domestic packaging manufacturers achieve self-sufficiency of raw materials for supporting UV adhesives.

II. Optical Communication and AI Computing Power

AI computing clusters and high-speed interconnection in data centers have driven surging demand for optical modules, fiber arrays, optical lenses and passive optical components. Core performance indicators of UV optical bonding adhesives for optical communication devices include high transmittance, low yellowing, long-term optical stability and bonding strength, without light transmission attenuation or interfacial cracking under temperature cycling and humid-heat conditions. Benzophenone photoinitiators are used in lens bonding adhesives for optical modules, fiber array fixing adhesives, sealing adhesives for optical device housings, and packaging adhesives for on-board optical components of computing power boards. Their UV absorption band matches LED-UV curing light sources, delivering fast curing speed to align with high-speed automatic assembly lines of optical modules and greatly improving production throughput. Modified low-yellowing benzophenone products endow cured adhesive layers with excellent light transmittance and resistance to yellowing over long-term service, ensuring stable transmission of high-speed optical signals. The cured adhesive layers feature good temperature change resistance to withstand continuous high and low temperature operating environments in data centers and prevent displacement of optical elements and optical path offset. From optical interconnection components of switching servers to packaging of high-speed silicon photonic devices, UV adhesives based on benzophenone systems guarantee long-term reliable operation of massive optical components in AI computing infrastructure.

III. Automotive Electronics

The automotive electronics industry complies with stringent automotive-grade standards. On-board devices are exposed to complex operating conditions including alternating high and low temperatures, high humidity, vibration, oil contamination and UV irradiation over the service life, imposing rigorous requirements on aging resistance, humid-heat resistance and vibration resistance of bonding and sealing materials. Benzophenone photoinitiators are applied in lens bonding adhesives for vehicle cameras, sealing adhesives for millimeter-wave radar sensors, conformal coatings for BMS battery management circuit boards, optical laminating adhesives for vehicle displays, bonding adhesives for automotive optical components, and local reinforcement UV adhesives for vehicle-mounted PCBs. This photoinitiation system enables rapid curing and fits automated production processes combining dispensing and UV curing for high production efficiency. The cured adhesive layers possess strong adhesion to stably bond various substrates including PC, PMMA, glass and FR4 circuit boards. They exhibit excellent resistance to humid heat and thermal shock, and bonding interfaces are less prone to cracking or detachment under long-term vibration during vehicle operation. For electronic control units of new energy vehicles, low-volatility benzophenone grades are selected to reduce contamination of device contacts by volatile small molecules and meet high reliability requirements of automotive electronics.

IV. New Energy & Energy Storage, Aerospace and Rail Transit

New Energy and Energy Storage

PACK modules of energy storage systems, battery management systems for lithium batteries, PCBs of energy storage converters and battery sensor assemblies require insulating sealing and local reinforcement protective adhesives. UV insulating adhesives formulated with benzophenone photoinitiators are used for conformal coatings of energy storage circuit boards, bonding of plastic parts for battery components, and sealing of wiring terminals in energy storage modules. The instantaneous UV curing characteristic shortens waiting time on production lines. The cured adhesive layers have high insulation strength, moisture and corrosion resistance to block intrusion of moisture and dust into electronic components. Low-migration grades reduce the risk of contamination of electrochemical systems by organic small molecules, satisfying the long service life requirements of energy storage equipment.

Aerospace

UV adhesives are adopted for bonding and protection of airborne sensors, airborne optical windows, precision aerospace structural parts and lightweight satellite components. Aerospace scenarios demand materials with low volatility, low outgassing, wide temperature range resistance, cosmic ray resistance and lightweight properties. UV adhesives formulated with specially modified benzophenone photoinitiators feature low VOC and low extractables after curing to meet outgassing specifications for aerospace materials. The adhesive layers have good toughness to resist flight vibration and impact loads, and can be used for bonding of airborne optical elements and sealing protection of precision sensors.

Rail Transit

UV adhesives for bonding and sealing of on-board control units, signal sensors, in-vehicle optical indicators and train display assemblies in rail transit adopt benzophenone photoinitiation systems. The materials withstand environments with large temperature differences, high humidity, continuous vibration and dust pollution, and have strong anti-aging performance to ensure stable operation of rail transit signal and control systems.

V. Medical and Life Sciences

Medical consumables, in vitro diagnostics and biological detection devices impose strict controls on biological safety and small-molecule leaching of materials. Harmful components are prohibited from dissolving out to contaminate samples or contact human tissues. Low-migration modified benzophenone derivatives are used in UV adhesives for microfluidic chip bonding, fixing adhesives for medical optical detection components, bonding of disposable medical plastic parts and packaging adhesives for biosensors. Molecular structure optimization significantly reduces migration and leaching risks of unreacted photoinitiators and their degradation products after curing, minimizing interference with biological samples and body fluids. The cured adhesive layers have no solvent residue and good adhesion to common microfluidic substrates such as PC, COC and glass. High curing precision meets the requirements for precision assembly of microchannels. They are widely used in the assembly of nucleic acid detection and biochemical analysis chips, supporting the localization of life science diagnostic equipment.

VI. Industrial Equipment and General Industry

Precision industrial equipment, optical instruments, sensors and general plastic/glass components constitute the largest application market for UV-curable adhesives. Benzophenone photoinitiators are highly versatile, easy to formulate, and have good compatibility with most acrylate resins and reactive diluents. They stand out in surface curing under oxygen-deficient conditions and solve the common tackiness issue on adhesive surfaces caused by conventional photoinitiators. Application scenarios include bonding of industrial measurement lenses, fixation of machine vision optical components, assembly adhesives for precision hardware and plastics, bonding of glass artworks, and UV protective coatings for home appliance parts. Compatible with dispensing, spraying and flow coating processes, they balance performance and cost. They can be applied not only to high-end precision equipment but also in large-scale automated production lines of general manufacturing to improve product assembly efficiency and finished product durability.

Closing Remarks

With the continuous popularization of LED-UV curing technology and upgrading of downstream UV adhesive industry, benzophenone products keep iterating toward high purity, low migration, low odor, low yellowing and compatibility with long-wavelength LED light sources. Faced with increasingly stringent material standards in high-end manufacturing fields such as semiconductors, AI computing power, new energy and medical industries, benzophenone-series photoinitiators will continuously tap application potential, drive technological innovation of UV-curable adhesives, facilitate breakthroughs in the domestic high-end fine chemical material industrial chain, and empower high-quality development of various industries.