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The Composition OF Conductive Adhesive

Time: 2020-07-23

Conductive adhesive is an adhesive with certain conductivity after curing or drying. It can connect a variety of conductive materials together to form an electrical path between the connected materials. In the electronics industry, conductive adhesive has become an indispensable material.

How does the conductive adhesive conduct electricity?

The mutual contact between the conductive particles forms a conductive path, which makes the conductive adhesive conductive. The stable contact between the particles in the adhesive layer is caused by the curing or drying of the conductive adhesive. Before the conductive adhesive is cured or dried, the conductive particles are separated in the adhesive, and there is no continuous contact with each other, so they are in an insulating state. After the conductive adhesive is cured or dried, the volume of the adhesive shrinks due to the volatilization of the solvent and the curing of the adhesive, so that the conductive particles are in a stable continuous state with each other, thus exhibiting conductivity.

What is the main composition of conductive adhesive?

   Conductive adhesive is mainly composed of resin matrix, conductive particles, dispersing additives, auxiliary agents, etc. The matrix mainly includes epoxy resin, acrylate resin, polychloroester, etc. Although the structure of highly conjugated polymers also has conductivity, such as macromolecular pyridine structures, which can conduct electricity through electrons or ions, the conductivity of this type of conductive adhesive can only reach the level of semiconductors, and cannot be like metals. The same low resistance makes it difficult to play the role of conductive connection. Most of the conductive adhesives used in the market are filler type.

   The resin matrix of the filler-type conductive adhesive, in principle, can use various types of resin matrixes, commonly used thermosetting adhesives such as epoxy resin, silicone resin, polyimide resin, phenolic resin, Adhesive systems such as polyurethane and acrylic resin. These adhesives form the molecular skeleton structure of the conductive adhesive after curing, provide mechanical properties and bonding performance guarantee, and enable conductive filler particles to form channels. Since epoxy resin can be cured at room temperature or below 150°C, and has rich formulation and design properties, epoxy-based conductive adhesives dominate.

    Conductive glue requires that the conductive particles themselves have good conductivity and the particle size should be within a suitable range, and can be added to the conductive glue matrix to form a conductive path. The conductive filler can be powder of gold, silver, copper, aluminum, zinc, iron, nickel, graphite and some conductive compounds.

   Another important component in conductive adhesive is solvent. Since the amount of conductive filler added is at least 50%, the viscosity of the resin matrix of the conductive adhesive is greatly increased, which often affects the process performance of the adhesive. In order to reduce viscosity and achieve good manufacturability and rheology, in addition to selecting low-viscosity resins, it is generally necessary to add solvents or reactive diluents. The reactive diluents can be directly used as the resin matrix for reaction curing. Although the amount of solvent or reactive diluent is not large, it plays an important role in the conductive adhesive, not only affecting the conductivity, but also affecting the mechanical properties of the cured product.      Commonly used solvents (or diluents) should generally have a larger molecular weight, slower volatilization, and the molecular structure should contain polar structures such as carbon-oxygen polar segments. The amount of solvent added should be controlled within a certain range so as not to affect the overall performance of the conductive adhesive.

   In addition to the resin matrix, conductive fillers and diluents, the other components of the conductive adhesive are the same as the adhesives, including crosslinking agents, coupling agents, preservatives, toughening agents and thixotropic agents.

How about Xianglong Keypad's conductive ashesive?

 The conductive rubber is made of natural silicon rubber, which is resistant to wear, corrosion and aging,etc characteristic. The button elasticity can reach 180-200g.