Thermocompression bonding

The cell is hermetically sealed. This is performed by a glass connection from the / "-alumina ceramic tube to a ring of a-alumina. Metal parts are connected to the a -alumina by thermocompression bonding and the metal parts are either con-... 

The cell design is shown schematically in Fig. 8.22. Two nickel components are sealed to a metallized j3-alumina collar by thermocompression bonding the 0-alumina tube is then attached to the alumina collar by a glass seal. This sub-assembly can then be welded to the prismatic metal can. A metal wick inserted in the steel can, before the sub-assembly is welded in place, acts as the cathode for sodium deposition when the cell is charged. The positive electrode is added as a mixture of nickel powder, salt and aluminium powder, and after addition of the molten sodium chloro-aluminate the cell is sealed by welding on the positive terminal... 

In the electrical and electronic equipment market, adhesives compete with other joining methods such as mechanical fasteners, brazing, welding, soldering, and thermocompression bonding. Major uses of adhesives in the electrical and electronic equipment market are shown in Table 1.5. Adhesives are generally the preferred method of joining whenever... 

Thermocompression bonding is a process in which soft metals such as Au are squeezed into each other with high force at elevated temperature. Thin films of metals can be deposited on the surface of wafers by evaporation, sputtering, or plating. 

Wire bonding is still the foremost method used. Aluminum or gold wire, generally 1-mil diameter, is used for most applications. High current power circuits require thicker wire up to 10-mil diameter. Die can be wire bonded at high speed with automatic thermocompression, thermosonic, or ultrasonic equipment. 

Thermocompression bonding n. The joining together of two materials without an intermediate material by the application of pressure and heat in the absence of an electrical current. 

The thermocompression bonding action does not effectively remove trace surface contaminants that interfere with the bonding process. 

Ultrasonic aluminum wire bonding is easily accomplished with the nickel-plated DEC. It should be noted that ultrasonic wire bonding of aluminum wire to copper can be effected the resultant bond is not as reliable as with the nickel plating. Gold thermocompression or thermosonic wire bonding requires at least 50 pin. of gold plating. 

If the subsequent assembly process calls for thermocompression or ther-mosonic wire bonding, the gold plating of the conductors is required. If ultrasonic aluminum wire bonding will be used, the plated nickel layer is sufficient. 

If the subsequent assembly process calls for thermocompression or thermosonic wire bonding, plated copper under the wire-bond sites should be avoided. This can be accomplished by selectively plating the copper. When the adhesion layer is Nichrome or titanium-tungsten, then precision-deposited thin-film resistors can be fabricated. 

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