Metallurgical attachment

In addition, there has been greater use of flexible circuitry and foldable flex circuits requiring a corresponding degree of flexibility in the adhesives used. For these applications, solders or other metallurgical attachment materials have often failed due to cracking, delamination, electrical opens, or changes in electrical parameters. Some... 

Once in place and bonded, the bonding material must not change dimensionally, otherwise loss of coupling power occurs. Although metallurgical attachments (solder or laser welding) are used and are dimensionally stable, they require high temperatures or special, expensive equipment. ... 

In practice, several techniques can be used to maximize the dissipation of heat. Of course, solder and other metallurgical attachments provide the lowest thermal resistance but, where adhesives must be used, those having the highest thermal conductivities should be selected. Some silver-filled adhesives, formulated with unique suspensions of silver, resin, and carrier fluid are reported to have thermal conductivities of 20 W/m-Kf l approaching those of ceramics and some metals. An adhesive having a high silver loading is produced once the carrier fluid has been removed, and the adhesive is fully cured. 

Because natural gold is never pure, ancient technologists had to develop impressive metallurgical skills to separate it from impurities such as silver. In Egypt and Mesopotamia, where these methods were devised, metalworking was sacred and metallurgists commonly laboured in compounds attached to temples. The Babylonian god Marduk was Lord of Gold . 

Tie Scientific and Technical Department of the Imperial Institute conducts investigations for the Indian and Colonial Governments, chiefly relating to the composition and utilisation of raw materials. The National Physical Laboratory includes a Department of Metallurgy and Metallurgical Chemistry. Laboratories are attached to many public Institutions, such as the Davy-Faraday Research Laboratory of Hie Royal Institution, and those of the Lister Institute and the Royal Dublin Society. 

Table 1.1 Comparison of metallurgical, polymeric, and vitreous attachment methods...

Comparison of polymer adhesives with metallurgical and vitreous attachment materials... 

Besides this prime role of attachment, electrically conductive adhesives are widely used to form electrical contacts between components and the printed-wiring board or other interconnect substrate, such as thin-film or thick-film ceramic substrates or flexible cable. For this function, adhesives serve as low-cost alternates to wire, solder, and other metallurgical connections. 

Table 1.1. Comparison of Metallurgical, Polymeric, and Vitreous Attachment Methods...

COMPARISON OF POLYMER ADHESIVES WITH METALLURGICAL AND VITREOUS ATTACHMENT MATERIALS... 

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