Metals surface, adhesion loss

Locus and Mechanism of Adhesion Failure during Corrosion Effects of Adhesive Chemistry. In previous studies (4- on the corrosion induced adhesion loss of coatings from steel surfaces, a primary mechanism for coating deadhesion was polymer degradation at the coating/metal interface by corrosion reactions that generate hydroxide ion ... 

Wear in a strict sense occurs whenever material is lost from a solid. The mechanism of loss can be abrasion, adhesion, erosion, cavitation, corrosion or fatigue. This loss can occur at the atomic level. At this level analytical tools such as the field ion microscope and the atom probe can be used to study wear loss of polymers. These tools have been used in the authors laboratory for many years to study polymer adhesion and transfer to metal surfaces ... 

A new area of concern for electrical stability arises because of the increasing use of conductive adhesives as replacements for solder. Some conductive adhesives show unstable electrical-contact resistance when used on non-noble metal surfaces such as copper or tin-lead solder. Although stable on gold, palladium, platinum, and silver surfaces, the same adhesives were found to be unstable on tin, tin-lead, copper, and nickel surfaces.The unstable resistance and increase in resistance in temperature-humidity exposures have been attributed to the growth of an oxide layer separating the filler particles from the substrate at the interface, a mechanism similar to that for the loss of backside contact in die-attach materials. 

The discussion of heat durability in this section should make clear that this is a complex phenomenon. Embrittlement, retropolymerization, thermoplasticity, and the loss of adhesion are all factors affecting the adhesive s performance on metal surfaces. Based on the published state of the art, optimum cyanoacrylate heat durability could be achieved using a combination of a heat-resistant adhesion promoter, a crosslinking agent, and a plasticizer. The heat durability promoters discussed in this section are summarized in Table XI. 

A very good alternative to abrasive or chemical cleaning is to impart an oxide to the copper surface. If the copper has not been cleaned or if there are residual etch resist metals on the surface, the copper will not oxidize. The oxide provides a fine stmcture and microronghness for very good adhesion. When using this techniqne, the fabricator shonld use a reduced oxide so that cleaning chemistries in subsequent processes will not attack the oxide layer and cause adhesion loss at the mask-copper interface. 

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