There is a wide range of uses for thermally conductive adhesives within the electronics industry. The main applications include bonding SMDs (Surface Mount Devices) to PCBs (Printed Circuit Boards), bonding heatsinks for dissipating heat from circuit boards or other components, potting and encapsulating parts (including PCBs, transformers and coils). There are also applications for electric motors, batteries, lighting and LED heat transfer management.
Any application requiring good heat transfer between component parts e.g. for heating and cooling units (heat exchangers) and tooling or mechanical parts also use thermally conductive adhesives.
Soldering is a quick and easy way of attaching components to PCBs. It is also very cheap and quite safe with lead-free solder now available. However, some component parts are not suitable for soldering as they may not have “legs” which go through holes in the PCB, or they need some sort of electrical resistance to protect them and prevent short circuits. Thermally conductive adhesives offer an ideal alternative for attaching SMDs when soldering isn’t practical. They also replace mechanical assembly – offering cost and process savings and helping to reduce component weight and prevent vibration loosening and rattling.
Components, PCB, and transformer coils are often “potted” inside a plastic housing (or “pot”) with a potting adhesive to help dissipate heat away from the electronic part, to protect the parts against impact, vibration, environmental conditions, and for security reasons.
Popular adhesive products for these applications include 1 and 2 part silicones, 2-part epoxies and polyurethanes (normally for potting). Occasionally it is possible to use 1-part epoxy adhesives if components are not sensitive to the high temperature needed for curing the adhesive. Alternatively, special room temperature cure 1-part epoxies that do not require high temperatures for curing can be used. However, these are very expensive to purchase and require special storage, shipping, and handling at subzero temperatures. Other recent developments include structural acrylic adhesives which combine rapid cure speeds with strength performance and high thermal transfer rate.”
On average, standard filled epoxy adhesives achieve thermal conductivity measurements of between 0.4 and 0.55 W/m.K, whereas an unfilled epoxy adhesive would achieve less (which is a pity as many potting applications require a low viscosity adhesive to fill all the gaps around the components). However, specially developed thermally conductive epoxies are available with thermal conductivity of between 1.5 and 3 W/m.K. It is possible to formulate epoxies with special fillers, including ceramic, metallic, or nano-fillers to give this level of thermal performance. In fact, epoxy adhesives can even be blended with silver powder to give both thermal and electrical conductivity! Products can be formulated to be flame retardant and comply with standards such as UL94-V0 which is often required in the electronics industry.
As well as good thermal conductivity, there are other benefits for electronics applications and general bonding. These include;
Before choosing a thermally conductive adhesive, consider a number of factors. It is not just a case of going for the adhesive with the best conductivity;
Permabond chemists are able to formulate thermally conductive adhesives, modified epoxies, and acrylic adhesives to meet your specific requirements. If you have an application you would like to discuss with a technical advisor or would like to receive further information, please contact firstname.lastname@example.org or email@example.com.