Thermally Conductive Adhesives

Rebecca Wilmot
Adhesive Properties, Thermally Conductive
September 16, 2014

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.

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.

Types of thermally conductive adhesive

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.”

Thermally conductive adhesives: Properties and benefits

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;

  • High strength performance – good adhesion to a wide variety of substrate materials
  • Resistance to very low and very high temperatures – able to cope with differential expansion and contraction between dissimilar substrate materials (adhesive normally requires some degree of toughening)
  • Resistance to chemicals, water, and humidity
  • Low-outgassing to minimize risk of damage to sensitive circuitry
  • Non-corrosive formulation
  • Resistance to thermal shock, impact, and vibration
  • Able to withstand solder-reflow processes
  • Compliance with RoHS and REACH

Adhesive considerations

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;

  • What substrate materials are you bonding together? What is the size, dimensions, and joint design?
  • What strength performance are you looking for?
  • How quickly do you need the adhesive to cure?
  • How will it fit into your production line? What cure mechanism is acceptable in your process?
  • Is there a gap?
  • What is the glue line thickness? (A thin glue line will aid with thermal transfer between components. But if there is differential thermal expansion and contraction between dissimilar materials, it could put a lot of stress on component parts. For this reason, a  toughened adhesive and a controlled glue line thickness of 0.25µm would be recommended)
  • If you are potting, how big is the “pot,” and how complex is the part that is being potted? We need to consider how well the adhesive will flow around the parts. Also, if the application involves a large volume of potting adhesive, we have to consider a slower curing product to prevent it from getting too hot during cure (exotherm).

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  or


Let’s Discuss Your Project.

Find out more
Find out more
Find out more

Latest Posts