Thermal conductivity is the foundation of reliable and effective electrical appliances, and the fast growth of the electronics industry has contributed to the demand for thermally conductive adhesives. Thermally conductive adhesives bond heat-generating components to heat sinks. They conduct heat while providing structural integrity, electrical insulation or conductivity, depending on the application.
Many different types and chemical compositions are available, each with advantages and considerations. Knowing which one is best for your application is essential to ensuring success in your assemblies.
Understanding Thermally Conductive Adhesives
Thermally conductive adhesives are industrial-grade adhesives that can conduct significant heat without degrading. One of their primary uses is in heat sinks — they transfer heat away from electric components to prevent overheating.
Their ability to conduct and dispense heat is entirely dependent on their formulation. As they have high thermal resistance, they can redirect the heat generated by an electric current, preventing malfunctioning.
Thermal adhesives are available in various chemical configurations to suit different applications. Some of the most common types of thermally conductive adhesives include:
Thermal Glue or Epoxy
Epoxy and thermal glue have filler materials with conductive properties. They are applied in a liquid state, allowing the material to seep deeper into the product’s surface textures. You can automate the application, which saves time and reduces human error, and adjust their thermal conductivity by changing the level of conductive particles in the filler materials.
Despite these benefits, applying thermal glue or epoxy can be imprecise. The process must be done in two parts — application and curing. Repeated thermal cycling can also make this material brittle over time. Once you have cured the parts, it can be challenging to rework them due to the hardness of the material.
Thermal Grease
Thermal grease, or thermal paste, is a liquid with less adhesive qualities than epoxy or glue. It seeps into textured surfaces and eliminates areas of low conductivity. Because its adhesive properties are minimal, you can disassemble components with minimal damage. However, it dries out over time.
The application is also imprecise and takes time, as you must apply multiple thin layers. Any overflow could damage the circuitry, making the product unusable.
Thermally Conductive Adhesive Film
A thermally conductive adhesive film is ideal for simple and complex geometries. The films are die-cut into precise shapes to bond a specific area, holding components in place while maintaining thermal conductivity.
These adhesive films provide an even distribution of conductive material. There is no risk of overflow, and their thickness is adjustable. They are unsuitable for heat sinks or potting but offer options for machine-automated applications.
Thermal Pads
Thermal conductive pads are attached between a printed circuit board and a heat sink. When an electric current passes through the board, the heat transfers onto the pad, redistributing it throughout the heat sink. These pads are easy to peel and attach and can be electrically or non-electrically conductive. However, they only eliminate some microscopic air gaps and are prone to degradation over time.
Characteristics of Different Adhesive Chemistries
Thermal adhesives are available in various chemistries, each with unique properties. The principal chemistries and their properties include:
- Epoxy: Thermally conductive epoxy adhesives have effective thermal conductivity and can be electrically and thermally conductive. They provide structural-grade adhesive bonds and high hardness, which are excellent for filling large gaps. Epoxy is also resistant to chemicals and environmental conditions.
- Urethane: Thermally conductive urethane adhesives have high elasticity to withstand thermal expansion and contraction. They also offer high chemical and environmental resistance. Thermal conductivity is moderate, and urethane has lower bond strength than epoxies and acrylics.
- Acrylic: Thermally conductive acrylic adhesives deliver high strength without needing surface preparation and fast curing times. They have good chemical and environmental resistance, moderate thermal conductivity and high hardness.
- Silicone: Thermally conductive silicone adhesives provide high elasticity and good environmental resistance. They offer moderate thermal conductivity and are only suitable for light loads. They have low hardness and poor chemical resistance, making them unsuited for specific applications.
Factors to Consider When Choosing a Thermally Conductive Adhesive
Each type and chemistry of adhesive is beneficial in the correct application. Consider the following factors to choose the right thermally conductive adhesive for your needs.
Temperature Range and Environmental Conditions
Continuous and intermittent peak temperatures can dictate your choice of adhesive. Silicone-based adhesives offer the highest performance in high temperatures. Similarly, thermal resistance is another consideration. Poor thermal resistance can cause the entire system to fail. Pay attention to the size, proximity and surrounding materials to determine the most effective thermal adhesive.
Environmental conditions are another crucial consideration. Factors like humidity, temperature and chemical exposure can impact your adhesive’s performance over time. Evaluate the specific environmental conditions in which the adhesive will be used and manufactured so you can focus on optimal performance.
Mechanical and Electrical Properties
Understanding the mechanical and electrical properties of your chosen adhesive is essential for achieving optimal performance in your application. Its mechanical strength determines its ability to withstand physical stresses, including shear, tensile and compressive forces. If the thermal adhesive is subject to thermal expansion, vibration or cycling, it needs high tensile strength and modulus of elasticity.
Any thermal adhesive used as an electrical insulator must have the correct dielectric strength and volume resistivity to withstand electrical stress and prevent leakage. Balancing thermal conductivity with electrical insulation properties is essential to achieving optimal performance for your application.
Surface Preparation for Adhesive Bonding
Surface cleanliness and preparation significantly influence the performance and longevity of your adhesive. Contaminants such as dust, oil, grease and moisture can create barriers that hinder proper adhesion. They lead to weak bonds and increase the chance of assembly failure.
All substrate surfaces must be clean and free from contaminants. They must also have the right texture to promote adhesion. Smooth surfaces may require additional treatment to enhance adhesion, as rougher surfaces improve bond strength.
The Advantages of Thermally Conductive Adhesive Film
Thermally conductive adhesive film emerges as an excellent choice for many applications, offering these key benefits:
- Enhanced thermal management: Thermally conductive adhesive film provides effective heat transfer between components, ensuring optimal thermal performance in various applications.
- Faster assembly: Thermally adhesive film is die-cut into precise shapes, making it easy to apply. The bonding process is more straightforward than traditional adhesives, leading to faster assembly times and increased productivity. The film’s consistent thickness also provides uniform heat transfer across the bonded surfaces, enhancing overall performance.
- High adhesion strength: Adhesive films offer strong bonding capabilities to various substrates, including metals, plastics and ceramics. They can also be formulated for different materials, making them ideal for automotive, electronics and aerospace applications.
- Reduced curing time: Many thermally conductive adhesive films cure quickly with minimal heat, allowing for faster production cycles and reducing downtime.
- Improved flexibility: These films can conform to various surface geometries, proving effective thermal management in complex assemblies.
Find the Ideal Thermally Conductive Adhesive for Your Application With Advantage Converting
Choosing the right thermally conductive adhesive is essential to ensure your assembly works as intended. However, the number of options can make the selection process challenging.
At Advantage Converting, we provide a range of materials to simplify thermal management. We have the manufacturing expertise to convert thermal interface materials with various thermally conductive adhesives. We also use silicone sponge materials, thermal fabrics and tapes to dissipate heat across industries and applications.
As a 3M preferred converter, we’re recognized for providing innovative solutions. Our access to 3M’s industry-leading materials and global supply chain makes us ideally positioned to assist you. Contact us to find the ideal thermally conductive adhesive today.
