Adhesives in the Electronics Industry: Characteristics and Applications

Adhesives are crucial for securely bonding similar or dissimilar materials, offering several advantages such as stress-free joints, high bonding strength, and ease of automation. These benefits have led to their widespread application across various industries, particularly as auxiliary materials in electronics manufacturing. As demands for miniaturization, lightweight construction, and high performance in electronic products continue to rise, the variety and usage of electronic-grade adhesives have expanded significantly, with advancements in performance keeping pace. Although adhesives used in the electronics industry account for less than 1% of the total adhesive market by volume, they represent a highly specialized sector with strict performance requirements and high added value, making them an important segment within the adhesive industry.

Requirements for Electronic Adhesives

The primary characteristics of adhesives used in the electronics industry include the following:

Main Types of Electronic Adhesives

1. General-Purpose Adhesives

"General-purpose" adhesives refer to those capable of bonding a wide range of materials, including metals and plastics. Key types include:

• Second-Generation Acrylate Adhesives: Available in dual-component and primer-activated versions, these adhesives are known for their fast curing times and high bonding strength.
• Alpha-Cyanoacrylate Adhesives: Representing the class of fast-curing adhesives, these are effective on most materials and, when used with primers, can bond even polyolefins and engineering plastics.
• Hot Melt Adhesives: Common varieties include EVA, polyamide (nylon), and polyester-based adhesives. EVA hot melt adhesives are widely used but have limited heat resistance, whereas the latter two types offer better thermal stability. The primary advantage of hot melt adhesives is their rapid curing and pollution-free nature.
• Silicone Adhesives: Silicone adhesives come in one-component and two-component formulations, each with various subtypes. In the electronics industry, one-component moisture-curing silicone rubbers are commonly used. Their applications include the insulation and sealing of high-voltage lines, bonding and sealing of various electronic components, hybrid integrated circuits, power modules, cathode ray tubes, and heat-resistant glass products.

2. Thermally Conductive Adhesives

Thermally conductive adhesives are essential when assembling components that generate significant heat and require efficient heat dissipation, such as transformers, transistors, and CPU chips. These adhesives are typically single-component and offer excellent thermal conductivity, resistance to thermal cycling, aging resistance, and electrical insulation. Additionally, they provide superior moisture resistance, vibration damping, corona resistance, dielectric strength, chemical resistance, and can operate continuously within the temperature range of -60°C to 280°C without swelling, while maintaining strong adhesion to most metals and non-metals.

3. Electrically Conductive Adhesives

In microelectronics assembly, electrically conductive adhesives are used for various applications, including bonding fine wires to printed circuit boards (PCBs), metal layers on ceramic substrates, and metal chassis. They also connect wires to tube sockets, components to through-hole PCBs, and waveguide tuning and repair. Depending on the curing system, electrically conductive adhesives can be categorized into room-temperature curing, medium-temperature curing, high-temperature curing, and UV-curing adhesives.

4. Potting Compounds

Potting compounds are used for bonding, sealing, potting, and protective coating of electronic components. In their uncured state, potting compounds are liquid, and upon curing, they provide waterproofing, moisture resistance, dust protection, insulation, thermal conductivity, sealing, corrosion resistance, temperature stability, and shock resistance. The most commonly used potting compounds are categorized into three main types based on material: epoxy resin potting compounds, silicone resin potting compounds, and polyurethane potting compounds.