Adhesion is the tendency of dissimilar particles or surfaces to cling to one another (cohesion refers to the tendency of similar or identical particles/surfaces to cling to one another). The forces that cause adhesion and cohesion can be divided into several types.
The intermolecular forces responsible for the function of various kinds of stickers and sticky tape fall into the categories of chemical adhesion, dispersive adhesion, and diffusive adhesion. In addition to the cumulative magnitudes of these intermolecular forces, there are certain emergent mechanical effects that will also be discussed at the end of the article.
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Bonding involves the joining of two or more surfaces together using some sort of adhesive. Bonding failure can occur when surface contaminants are accidentally introduced into the process, or if the adhesives are wrong for the job.
- For polymer packages, surface pretreatments and coatings, failures may occur due to contaminants introduced during the handling or presence of lubricated spindle.
- In the case of metallic aluminum bond failures in microelectronics, the cause may be due to plasma remnants, an oxide layer or underlayers that diffuse grain boundaries to reach and spread over the surface during or after bonding causing failure.
Discovering the source of bonding problems often requires surface-sensitive analytical tools. Both sides of the failure site must be investigated to locate the contaminant causing the bond failure.
