What is an electrically conductive adhesive?
Have you ever wondered what an electrically conductive adhesive is? As a rule, it is an adhesive that is provided with conductive metallic fillers. In this article, we will explain how these conductive adhesives work and when they are used.
How does an electrically conductive adhesive work?
An electrically conductive adhesive usually consists of an adhesive, a curing agent and an electrically conductive metal that serves as a filler. Due to the high concentration of particles of the conductive metal in the adhesive, continuous conductive networks are created in the adhesive, which make the adhesive electrically conductive overall.
Some electrically conductive adhesives are also referred to as ECAs, which is an abbreviation for “Electrically Conductive Adhesives “.
What electrically conductive adhesives are available?
The types of electrically conductive adhesives differ according to the adhesive used and the filler mixed with it.
Epoxy resin is often used as an adhesive for electrically conductive adhesives. However, there are also electrically conductive silicone adhesives, for example, in which the adhesive is
The following metals are suitable as electrically conductive fillers, which are distributed in flake form in the adhesive:
- Gold
- Nickel
- Palladium
- Platinum
- silver
In the semiconductor sector, the so-called silver conductive adhesive is used in particular, in which the adhesive contains around 80 percent silver flakes.
The advantage of silver is that this metal has a very low resistance, which makes it particularly conductive. Of all known metals, silver is the one with the highest conductivity. Compared to gold, for example, silver is also cheaper
Application of electrically conductive adhesives – bonding instead of soldering
Electrically conductive adhesives are generally used in electronic components, for example when soft soldering would not lead to a satisfactory result. This can be the case, for example, if there is a risk of cracking during soldering or diffusion, i.e. mixing of the base material with the solder used.
In contrast to leaded solders, electrically conductive adhesives, i.e. ECAs, have the advantage of being lead-free. ECAs that cure at room temperature have a further advantage. Conventional soldered joints require high temperatures during production.
ECAs that harden at room temperature are therefore also referred to as cold solder in comparison to conventional solder joints, although ECAs themselves are not solder, but a solder substitute or solder alternative.
When working with electrically conductive adhesives, however, it is important to be aware of the typical problems associated with bonding technology. For example, surface contamination must be removed before bonding so that the adhesive adheres well to the base material. Corrosion of the base material or mismatching of the coefficient of thermal expansion of the materials used can also lead to delamination.
ECAs are sometimes also used for shielding by distributing electrical charges around a specific object. This is intended to prevent these charges from passing through the object. In addition, certain ECAs are also suitable as heat conductors. These ECAs can therefore also be used to dissipate heat in electronic components.
Difference between isotropic and anisotropic adhesives
A distinction is made between isotropic and anisotropic conductive adhesives, or ICAs (Isotropic Conductive Adhesives) and ACAs (Anisotropic Conductive Adhesives) for short.
ICAs are characterized by the fact that they conduct in all directions, while ACAs only conduct in one direction. The latter are particularly suitable for use with flip chips, but also for use in RFID assemblies.
Order LOCTITE from Henkel at abovo
Henkel offers various electrically conductive adhesives under its LOCTITE brand. abovo AG has been an authorized distributor for Henkel Electronic Materials (Henkel Electronics) in Switzerland for more than 15 years and has a great deal of experience in handling electrically conductive adhesives from Henkel. It should be noted, for example, that most of the silver conductive adhesives must be stored at minus 40°C, otherwise they will dry out.
Dry ice is used for the transportation of silver conductive adhesives. An exception is the adhesive
Among other things, the following properties of the electrically conductive adhesive and the following questions regarding the requirements should be clarified before purchasing an ECA:
- Contact resistance
- Curing temperature
- Curing time
- Viscosity
- Shelf life
- Processing time
- Service life
- Flexibility
- Coefficient of thermal expansion
- Type of component used and its properties
- Size of the component
- Which application/application technology is used
- Maximum permissible curing time and curing temperature
- Thermal shock/thermal cycle requirement
The experts at abovo will be happy to advise you on which electrically conductive adhesive is the right one for your application and provide you with the properties of the respective electrically conductive adhesive.
