Adhesion between surfaces assuring

The most important requirements to assure good adhesion between surfaces are the cleanliness and chemical and physical condition of the surfaces. The adhesive chosen must be able to wet the surfaces so that a contact angle of less than 90° results, as... 

The irradiated components can be placed adjacent to sulfur-containing unvulcanized elastomeric compounds and, when necessary, coated with suitable adhesive between the contacting surfaces to assure good bond after final cure of the tire.54... 

Particle/particle interactions induce aggregation, while matrix/filler interactions lead to the development of an interphase with properties different from those of both components. Both influence composite properties significantly. Secondary van der Waals forces play a crucial role in the development of these interactions and they are modified by surface treatment. Occasionally reactive treatment is also used its importance is smaller in thermoplastics than in thermoset matrices. However, reactive treatment must always be used in fiber reinforced polymers in order to achieve the necessary adhesion between the components. Strong adhesion is a primary condition of good stress transfer, assuring the proper performance of the composite. 

Most commercially available anisotropically conductive adhesives are formulated on the bridging concept, as illustrated in Fig. 1. A concentration of conductive particles far below the percolation threshold is dispersed in an adhesive. The composite is applied to the surface either by screen printing a paste or laminating a film. When a device is attached to a PWB, the placement force displaces the adhesive composite such that a layer the thickness of a single particle remains. Individual particles span the gap between device and PWB and form an electrical interconnection. For successful implementation of anisotropically conductive adhesives, the concentration of metal particles must be carefully controlled such that a sufficient number of particles is present to assure reliable electrical conductivity between the PWB and the device (Z direction) while electrical isolation is maintained between adjacent pads (X,Y directions). 

Since the adhesive matrix is a nonconductive material, interconnection joints rely to some extent on pressure to assure contact for conventional ACAs. Adhesive interconnections therefore exhibit different failure mechanisms compared to soldered connections, where the formation of intermetallic compoimds and coarsening of grains are associated with the main mechanisms. Basically there are two main failure mechanisms that can affect the contacts. The first is the formation of an insulating film on either the contact areas or conductive particle surfaces. The second is the loss of mechanical contact between the conductive elements due to either a loss of adherence or relaxation of the compressive force. 

Fluorinated surfactants are used in solvent-based adhesives (e.g., Zonyl FSN-100 and FSO-lOO) or in water-based adhesives (e.g., Zonyl FSA, FSP, and FSN). Fluorinated surfactants added to water-based adhesives facilitate wetting and penetration of the substrates being joined [1]. By improving leveling and spreading, fluorinated surfactants assure a complete contact between the joining surfaces and retard foaming. 

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