Comparison of Metal Conductive Materials for Conductive Adhesive
Conductive adhesive has the advantages of high resolution, relatively low curing temperature, good mechanical properties and good wetting with most materials, which can well meet the development trend of miniaturization of electronic products and highly integrated printed circuit board. Therefore, conductive adhesive is often used as a substitute for lead tin solder in electronic packaging.
According to the matrix composition, conductive adhesives can be divided into structural type and filling type. The structural type refers to the polymer material as the matrix of conductive adhesive, which is conductive adhesive; Filling type refers to the conductive adhesive which usually uses adhesive as matrix and relies on adding conductive filler to make the adhesive liquid have conductive effect. Its conductivity mainly comes from conductive fillers. The resistivity, shape, particle size and distribution of fillers directly affect the conductivity of conductive adhesives.
At present, the common metallic conductive fillers are silver (Ag), gold (AU), nickel (Ni), copper (Cu) and aluminum (AL). What is the difference between these conductive fillers?
Silver
Silver has the characteristics of high conductivity and thermal conductivity, moderate price, easy processing and so on. It is hardly oxidized in the adhesive. Even if the oxidized silver oxide still has conductivity, it is widely used. Although silver has many advantages, it is the most widely used conductive filler of conductive adhesive, but it will produce electromigration phenomenon under the action of electric field, which will reduce the conductivity and affect its service life.
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Silver Nanopowder
Copper
Copper based conductive adhesive is the most widely used and stable one at present. The resistivity of copper is similar to that of silver, and the price is cheaper than that of silver. It should be an ideal conductive filler for preparing conductive adhesive. However, the chemical property of copper is more active than that of silver, which will be oxidized rapidly in air and then covered with insulating oxide layer; The higher the specific surface area of powdered copper, the faster the oxidation rate, which will make its conductivity decreased rapidly, thus limiting its application.
In fact, the appropriate surface modification is useful. The research shows that silane coupling agent can improve the conductivity and stability of copper powder conductive adhesive. Of course, in addition to using silane coupling agent to modify the surface of copper, silver plating on the surface of copper is also a common way to prevent copper oxidation and reduce the cost. In addition, the morphology and size of copper also affect the conductivity of conductive adhesive. The use of fibrous or fibrous like copper powder with large aspect ratio will help to improve the conductivity of conductive adhesive.
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Gold
Gold is the king of conductive fillers. The conductive adhesive with gold as conductive filler has good conductivity and stable performance. It can work in harsh environment without electromigration in normal environment. But its price is high, only used in the circuit with high reliability and small chip size, such as aerospace industry.
Nickel
Its resistivity is higher than that of silver, copper and gold, so the prepared conductive adhesive has higher resistivity, and nickel is also more active, and it is easy to be oxidized when the temperature rises, resulting in increased resistivity. Therefore, the conductive adhesive prepared with nickel can not be used in high-end precision electronic instruments.
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nano nickel powder for conductive filler.The particle size is 50nm, 80nm, 100nm, 150nm, 300nm, 400nm, 600nm, 1um, 5um, 10um, 15um, 25um, and so on. If you are interested, pls click here:
Nickel Nanopowder
