Base Material Components

Environmental legislation such as the European Union s Restriction of Hazardous Substances (RoHS) directive has a profound impact on all levels of the electronics supply chain, including these components. RoHS restricts the use of lead, which is an element in the solder used for component assembly onto printed circuits. The impact on the base materials and components is primarily the result of higher assembly temperatures that are associated with lead-free assembly. Table 7.1 summarizes the key issues for base material components. RoHS issues will be discussed further in Chap. 10. 

TABLE 7.1 Lead-Rree Assembly Impact on Base Material Components... 

The critical base material properties required for each are summarized here, and discussed in more detail later in this chapter. The impact on the base material components is discussed in Section 10.4. 

As pointed out in Table 10.2, the vapor pressure of water at lead-free assembly temperatures—260°C, for example—is much higher than at eutectic tin-lead assembly temperatures such as 230°C. Figure 10.10 plots the vapor pressure of water, in both mm Hg and psi, versus temperature. At 230°C the vapor pressure of water is near 400 psi. At 260°C, it is close to 700 psi. Therefore, any absorbed moisture within a PCB during assembly can have a much greater impact in lead-free assembly, as the greater pressure stresses the adhesion between the base material components and can also create small voids within the resin system. 

The increasing use of bio-based, but non-degradable polymers as additives in biopolymer blends tends to impair their biodegradabiUty. For co- and ter-polymers, the increasing use of non bio-based blend components or petrochemical monomer raw material necessarily leads to a reduction in the amount of bio-based material in the final polymer material. Currently, no minimum content levels have been established for bio-based material components in biopolymer blends and co- or ter-polymers. Therefore, polypropylene-starch blends or various copolyesters are considered biopolymers, even though they are non-biodegradable and their bio-based content is significantly smaller than their petrochemical content. 

Table 4-15 lists base materials Elliott has tested. This list, which is continually being expanded, includes low alloy steels, high alloy iron base, nickel base, cobalt base materials, and odiers. Table 4-16 shows some of the coatings Elliott has tested. The list indicates die supplier, coating designation, and major components of the coating composition. 

When contemplating the use of copper-base materials for industrial purposes it is necessary to bear in mind that even though a satisfactory life of the component may be obtained, trouble can arise from other causes ... 

Neutral and alkaline solutions Copper-base materials are resistant to alkaline solutions " over a wide range of conditions but may be appreciably attacked by strong solutions, particularly if hot. Copper/nickel alloys usually give the best results in alkaline solutions. Copper and copper alloys should be avoided if ammonia is present, owing to the danger of both general corrosion and, if components are under stress, stress corrosion. 

These have been developed for special uses. For example, since petroleum-based materials harm natural rubber, a grease based on castor oil and lead stearate is available for use on the steel parts of rubber bushes, engine mountings, hydraulic equipment components, etc. (but not on copper or cadmium alloys). Some soft-film solvent-deposited materials have water-displacing properties and are designed for use on surfaces which cannot be dried properly, e.g. water-spaces of internal combustion engines and the cylinders or valve chests of steam engines. 

From a practical review, perhaps it can be stated that buildings and construction materials are exposed to the most severe environments on earth, particularity when the long time factor is included. The environments include such conditions as temperature, ultraviolet, wind, snow, corrosion, hail, wear and tear, etc. Basically the following inherent potentials continue to be realized in different plastics ease of maintenance, light weight, flexibility of component design, combine with other materials, corrosion/abrasion/weather resistance, variety of colors and decorative appearance, multiplicity of form, ease of fabrication by mass production techniques, and total cost advantages (combinations of base materials, manufacture and installation). 

R. Mukhopadhyay, RecycUng of automotive systems and components and development of non-oil-based material for mbber industry. Annals of the Indian Academy of Engineering, III, 107-111, December 2006. 

When an ophthalmic ointment is manufactured, all raw material components must be rendered sterile before compounding unless the ointment contains an aqueous fraction that can be sterilized by heat, filtration, or ionizing radiation. The ointment base is sterilized by heat and appropriately filtered while molten to remove extraneous foreign particulate matter. It is then placed into a sterile steam-jacketed kettle to maintain the ointment in a molten state under aseptic conditions, and the previously sterilized active ingredients) and excipients are added aseptically. While still molten, the entire ointment may be passed through a previously sterilized colloid mill for adequate dispersion of the insoluble components. 

Wastewater from porcelain enameling on steel is generated by base metal surface preparation, enamel application, ball milling, and related operations. The constituents in the wastewater include the base material being coated (iron), as well as the components of the surface treatment solutions and enamels being applied. 

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