What is the knowledge of conductive fillers for conductive adhesives

Conductive adhesiveThe conductive fillers are mainly divided into three categories: carbon, metal, and metal oxide. Carbon black in carbon based materials has good conductivity, but there are difficulties in processing; Graphite is difficult to crush and disperse, and its conductivity varies greatly depending on the place of origin. Carbon fillers generally use a mixture of carbon black and graphite powder. Metal oxides generally have poor conductivity. The commonly used fillers are metal powders with low resistivity such as Au, Ag, Cu, Ni, etc.

Au powder has excellent conductivity and chemical stability, making it the most idealConductive fillerHowever, it is expensive and generally only used in situations with high requirements. Ag powder has a relatively low price, good conductivity, and is not easily oxidized in air. However, it undergoes electromigration in humid environments, which reduces the conductivity of the conductive adhesive. Cu powder and Ni powder have good conductivity and low cost, but they are prone to oxidation in air, resulting in decreased conductivity. Therefore, conductive fillers are generally selected as Ag or Cu.

The particle size and shape of conductive fillers have a direct impact on the conductivity of conductive adhesives. Fillers with larger particle size have better conductivity than those with smaller particle size, but at the same time, they can lead to a decrease in connection strength. Amorphous (sheet-like or fibrous) fillers have better conductivity and connection strength than spherical fillers. But anisotropyConductive adhesiveOnly spherical fillers with narrow particle size distribution can be used. The combination of fillers with different particle sizes and shapes can achieve better conductivity and connection strength.