What Adhesion Accomplishes

What is accomplished by adhesion promotion treatments in IC manufacturing should actually be referred to as wafer substrate preparation, and not adhesion. Adhesion in the structural sense, as experienced in airplane composite material parts attachment, is not accomplished by silane wafer processing treatments except for the PI applications discussed early in this paper. The term adhesion, as it is used here, refers to a more practical definition—that is, resist image adhesion. Nevertheless, this type of adhesion is essential to the huge international semiconductor business, and the early silane work of Plueddemann and others was essential to early wafer adhesion process development. 

In many instances, vibration problems in turbomachinery can be attributed to faulty support. Once the problem areas have been identified, correcting defects can be a logical procedure. What is novel is that this result can often be accomplished through the proper selection and application of adhesives. 

Short-term preservation (several weeks) can usually be successfully accomplished by generous application of polyethylene plastic wrap and duct-tape. Be careful in applying the tape to avoid direct contact with the items. The adhesive can be left behind on the part and when removed, can take with it important dust, fibers, or other data. Even short-term preservation requires some control of access, chain of custody documentation and conspicuously posted signs. Many workers are genuinely curious to learn and see for themselves what the damaged or essential part actually looks like, and may unintentionally cause changes. 

Quality control begins on the receipt of raw materials such as adhesives and catalysts. The purchase order ordinarily defines the required quality properties of this material. This is accomplished by an actual statement of requirements, or by what is called out in the material specifications. The inspection requirements are normally specified in the material specifications as Quality Acceptance Tests or as Receiving Inspection Requirements. ... 

Fortunately, a great deal of work has been accomplished in a short time, and notably by aircraft manufacturers as well as adhesives suppliers. There are several important contributions in this area. First, in the area of FPL etch, the important consideration is what kind of bonding surface is provided by the preparation method. The chromic acid/sulfuric acid not only removes air oxide and leaves base metal it also has a chemical potential which produces a very thin anodic type oxide layer of the surface. This oxide layer is porous, due to the dissolving action of the strong acid mixture, and thus the surface produced may be characterized as a thin, porous anodic oxide. (A. W. Smith compared it to a 3V chromic acid anodize based on impedance measurements.) The optimum conditions for this etch as to time, temperature, and composition have been studied at Fokker and by Smith and generally a somewhat higher concentration of sodium dichromate or chromic acid was recommended than was commonly used. 

Pressure-sensitive adhesives were so named because they bond under very light pressure. However, since we name other adhesives based on what accomplishes their change in state (heat-activated, solvent-activated adhesives, etc.), perhaps it would be more descriptive to refer to these materials as time-scale sensitive adhesives. 

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