Which is the best adhesive for electronics?

In the manufacture and assembly of electronics, adhesives have come to replace many traditional soldering processes. Adhesives provide a strong bond to hold PCB components in place. They also protect electronics against vibration, corrosion and environmental hazards.

Typical applications of adhesives for electronics include: bonding of surface-mount devices, wire tacking, potting and encapsulating and conformal coating of PCBs. A range of adhesive technologies is available to meet different application needs.

Main applications of adhesives for electronics

• Bonding of surface-mount devices to circuit boards: SMDs are placed on beads of adhesive. The adhesive is then cured by exposure to heat or UV radiation. The process holds SMDs in place until they are soldered to the board. Single-component acrylics, epoxies and urethane acrylates are commonly used to this purpose.
• Wire tacking: The adhesive is used to reinforce wired connections. The wire is bonded to the board and protected from vibrations. Adhesives used for wire tacking are cyanoacrylates, epoxies and light-curable acrylics.
• Potting and encapsulation: The process of immersing an entire assembly in adhesive. This shields components from physical damage. It also provides additional insulation. Typical adhesives for potting are epoxies, polyurethanes, silicones and acrylics.
• Conformal coatings: Thin resin films adhering to the board. They are usually applied by spraying. Coatings protect components and provide isolation. Epoxies, polyurethanes, silicones and acrylics are common choices.

Electronics adhesive properties

Several types of adhesives are suited for electronics. Each type is required to have specific properties.

• Electrically conductive: Most adhesives are not electrically conductive. Conductivity is achieved by adding a filler to the base material. Typical fillers are silver, nickel and carbon. The base material is usually epoxy resin.
• Thermally conductive: These adhesives are designed to transfer heat away from sensitive electronics. The heat is then dissipated through heat sinks. Thermally conductive systems are formulated with epoxies, silicones and acrylics.
• Ultraviolet curing: Light-curing adhesives are simple to use. They cure quickly without heat. Also, they don’t require additives that are potentially damaging to the environment. UV curing adhesives are usually acrylics and contain photo-initiators.

Many other properties have to be considered when choosing adhesives for electronics. These include: suitability for high-speed dispensing; good strength and flexibility; quick curing time. Adhesives used for SMD bonding need to be single-component. This avoids issues with air entrapment and altered viscosity.

The best adhesive for electronics depends on the application. Epoxy resins are the most versatile. UV-curing acrylics are well-suited to SMD bonding. Cyanoacrylates are frequently used for wire tacking. Silicones are great for encapsulation and conformal coatings, because of their outstanding sealing properties.

Conro Electronics, as an electronic manufacturing distributor, offers a wide choice of adhesives and conformal coatings, from major manufacturers such as Henkel Loctite and Humiseal.

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