The bonding operation

Copper wines are used primarily because of thein economy and resistance to sweep, ie, tendency of the wine to move in a plane perpendicular to its length, during plastic encapsulation (11—16). Because copper is harder than gold, more attention is needed during the bonding operation to prevent the chip from cratering. Table 6 fists the various properties for wine materials. 

The implicit bonds are determined by calculating the interatomic distances as drawn on the screen, and bonding all atoms within 1.6 A of one another. A "delete bond" feature allows one to remove extra, unwanted bonds. The "add bond" feature, allows the bonds to be assigned explicitly by indicating the atom pairs to be bonded and depressing a key on the keyboard. The bonding operations automatically determine the connectivity data. 

Perform the bonding operation under appropriate moisture conditions (avoid excessive accumulation of water on the material surface) 50% relative humidity is ideal. 

Form a protective shield on the surface where chlorosis is likely to develop by applying oil to the area surrounding the material surface immediately before or after the bonding operation. 

Probably the most critical aspect of the introduction of a new process is that of the education and training of the personnel involved. It is vital that the people have a qualitatively correct overall picture of the importance of the different stages of the bonding operation, and of the health and safety considerations. The use of an untrained workforce is likely to cause problems sooner rather than later ... 

If a chemical surface treatment in required, the process must be monitored for proper sequence, bath temperature, solution concentration, and contaminants. If sand- or grit-blasting is employed, the abrasive must be changed regularly. Fresh solvents for cleaning should he on hand. Checks should be made to determine if cloths or solvent containers have become contaminated. The specific surface preparation used can be checked for effectiveness by the water-break-free test. After the final treatment step, the substrate surface is checked for its ability to form a continuous film of water when deionized water droplets are applied to the surface. After the surface treatment has been found to be adequate, precautions must be taken to assure that the substrates are kept clean and dry until the bonding operation. The adhesive or primer should be appUed to the treated surface as quickly as possible. 

Variables in the bonding operation are the frequency generated, dielectric loss of the plastic, the power applied, pressure, and time. The materials most suitable for dielectric welding are those that have strong dipoles. These can often be identified by their high electrical dissipation factors. Materials most conunonly welded by this process include polyvinyl chloride, polyurethane, polyamide, and thermoplastic polyester. Because the field intensity decreases with distance from the source, this process is normally used with thin polymer films. 

The FRP composite plate material used for the bonding operation is either the ultra-high-modulus (European definition) or the high-modulus (European definition) CFRP composite, and the manufacture and installation of the CFRP composite onto the site stmcture would be by one of the following methods ... 

The manual systems that we have studied were using the movement of the operator s hand in order to realise the relative movement of the applicator and the parts to be coated. In the following application techniques, the parts to be coated move under the application system which has a fixed position. It may be rolls, die, fixed guns, doctor blade, etc. Usually the bonding operation is part of the total production line, and the adhesive applicator is integrated into a conveyor together with drying ovens, assembly system and presses. 

There is no general-purpose adhesive. The best adhesive for a particular application will depend on the materials to be bonded, the service and assembly requirements, and the economics of the bonding operation. By using these factors as criteria for selection, the many commercially available adhesives can be narrowed down to a few possible candidates. All the desired properties are often not available in a single adhesive system. In these cases, a compromise adhesive can usually be chosen by deciding which properties are of major and minor importance. 

Cost requirements. Economic analysis of the bonding operation should consider not only raw-materials cost but also the processing equipment necessary, time and labor required, and cost incurred by wasted adhesive and rejected parts. Final cost per bonded part is a realistic criterion for selection of an adhesive. 

Fig. 27 shows the two time limits, waiting time and open time the working time WT is equal to OT — WT. It should be adapted to the speed of the bonding operations and the production line. 

The types of equipment available to assist in the bonding operation, ie jigs, fixtures, adhesive rollers, ovens, other types of heating equipment, presses, etc. 

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