Epoxy is a natural substance. It is made by carbon chains which are linked to elements like hydrogen, nitrogen, and oxygen. The link that is formed between these different elements is because of the covalent bond present between them, in which each element shares a pair of electrons in order to bind together.
Epoxy is commonly used as an adhesive, and a good adhesive must have the capability to withstand harsh conditions such as chemicals, water damage, and high temperatures. A quality adhesive also needs to be malleable to be formed into the desired shapes. However, in the case of artificially created bonds like epoxy, all of these properties can be controlled or changed as desired.
The thermal conductivity of epoxy
Generally, epoxy has a poor thermal conductivity that ranges from 0.15–0.25 W/mK. Hence, this makes it a good insulator. However, the thermal conductivity of epoxy can be increased by adding insulator composites. Because epoxy is used in many applications such as the automotive industry, fuel cells, and electronics, it is important to make sure that the thermal conductivity of epoxy is just right.
Mainly for being used in electronics, the thermal conductivity of epoxy is intensified. The additional composite that is added into the epoxy to make it more conductive forms a percentage of its mass. The elements that can be used for this purpose include and are not limited to Graphite, Gold, Carbon, Silver, Copper, and Nickel.
By adding these elements with epoxy, the electrical conductance in addition to the thermal conductivity of the material increases. In addition to the metallic fillers mentioned above, ceramic fillers can also be added to the epoxy mixture in order to attain higher heat conductivity. As these materials are added to the adhesive formulation, they become more useful in many applications, primarily for use in electronics.
When these fillers are added, the following things are kept in mind as they directly affect the conductivity.
- The type of filler being used
- The concentration of the particles of the filler
- The proportions of the particles of filler
- The filler-to-adhesive ratio
- The shapes of the particles of the filler
Uses of thermally conductive epoxy
Thermally conductive epoxy can be used in several applications, generally in bonding, coating, enclosing, and potting applications in many different industries. Some of the specific applications of thermally conductive epoxy are:
- Heat sink bonding
- Potting
- Chip scale packages
- Power semiconductors
Advantages of thermally conductive epoxy
With a wide range of applications in a number of different industries, thermally conductive epoxy offers many different benefits. Some of the featured benefits are discussed below.
- The product is lead-free. Hence the material used in many different applications becomes non-toxic. No lead is actively used in the production of thermally conductive epoxy.
- Because the toxicity decreases, there is no need for preventative measures such as wearing a mask when handling thermally conductive epoxy.
- Because the material contains traces of conductive metals, the product becomes moisture resistant, preventing any kind of moisture damage.
- No flux occurs through the material.
Drawbacks of thermally conductive epoxy
With benefits come the weaknesses as well. The same goes for epoxy, which is made thermally conductive. A few of the downsides are listed below.
The material must be properly stored to keep its shelf life extended. When the material is exposed to open air, it may get toxic and non-conductive materials deposited into it, which can decrease the conductivity as well as the shelf life of the material.
In order to get the desired conductivity, the correct amount of composites have to be added, and the correct composite-adhesive ratio has to be kept in mind. If the value of the concentration of either of the substrates fluctuates, it can directly affect the thermal conductivity as well as electrical conductivity.
Because the traces used for increasing the conductivity are of expensive materials, i.e., gold, epoxy can sometimes become really expensive when there is a huge amount of composites present in it.
It is easier to use than soldering, but it takes more time to set than soldering as well. In most cases, this is why many people prefer to use a soldering method over using conductive epoxy because it takes a lot of time to set into place.
Conclusion
Being used in a variety of applications, epoxy has a role in our day-to-day life. No matter if we need to use it or not, it is important that we know about its thermal conductivity as it is something that you may require at any time. While the article clarifies that epoxy is not thermally conductive, it can be made by adding some elements. Can you think of additive features other than those discussed above?