Conductive adhesive

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The material conductive adhesive refers to an electrically and / or thermally conductive adhesive . One of the main uses of electrically conductive adhesives is the bonding of flexible conductor foils when assembling liquid crystal screens, or the simultaneous bonding and contacting of chips or SMDs on circuit boards. Thermally conductive adhesives are mainly used for bonding heat sinks or for dissipating heat, e.g. for sensors.

A connection with a conductive adhesive is less conductive than a soldered connection , but it is elastic and therefore more mechanically resilient. This elasticity is achieved in particular with the silicone adhesives used to connect solar cells . An enormous advantage of adhesives is that, unlike solder, they are lead-free and therefore more environmentally friendly.

Conductive adhesives consist of the adhesive (resin) and inorganic, electrically conductive fillers. Their share is around 30 percent by volume . Because of the metallic fillers used, the connection points also have good thermal conductivity. Well-suited fillers include silver ( conductive silver adhesive ), gold , palladium , nickel and platinum , while copper , aluminum , tin , lead , silicon and bronze are problematic or unsuitable . Silver is preferred in semiconductor technology.

Anisotropic conductive adhesives form a class of their own among the conductive adhesives. Spherical conductive particles are used as the filler material. Only 5% of the total volume is made up of the conductive material. This creates a locally limited electrical connection. When applied as a thin film, the electrical connection is only established vertically (between the surfaces), but not horizontally, as the balls do not touch. This allows the adhesive to be applied over a large area without adjustment. The disadvantage is the limitation of the operating temperature to 80 degrees Celsius and a principle-related implied short-circuit probability .

See also

literature

  • Dirk Jansen: Handbook of Electronic Design Automation. Hanser, Munich 2001, ISBN 3-446-21288-4 .
  • Gerd habenicht: Gluing: basics, technology, applications. 5th edition. Springer, Berlin a. a. 2006, ISBN 3-540-26273-3 .