| 摘要 |
1356879 Welding by pressure FERRANTI Ltd 9 Oct 1972 46467/72 Addition to 1255832 Heading B3R A method of manufacturing a support for a semi-conductor device comprises the steps of providing a supply of spherical particles of gold, selecting a particle, transporting the selected particle to and depositing it on a selected part of a supporting member and impacting the particle into the surface of said selected part by an unheated impacting tool to deform the selected part and bond the particle thereto. The surface of the supporting member may be of gold, silver, copper or aluminium. An electrolytically-deposited silver coating may be provided on a nickel-iron-cobalt alloy lead frame and to protect the silver coating a gold flash of molecular thickness may be deposited thereon. Bonding may be carried in an atmosphere of nitrogen. Selection and transport of the spherical particle of gold, which may be 0À01 inch diameter, is preferably effected by means of a suction nozzle 17 which is adapted to enter a receptacle 11 holding a supply of particles 10. The nozzle is heated, e.g. to 300‹ C. and in depositing the particle 10 on the selected part of the lead frame 18 the particle 10 is deformed as in Fig. 2b and caused to adhere to the lead frame. Bonding is effected by an unheated impacting tool 20 of tungsten carbide having a polished plane end surface 21. Apparatus for simultaneously bonding gold particles to a batch of sixteen lead frames 18 mounted on an elongated strip 23 comprises a carrier 27 reciprocable laterally by cylinder and piston means 28 beneath a vertically reciprocable head 31 supporting a series of impacting tools 20 and suction nozzles 13, the carrier 27 having an undercut mounting channel 26 in and along which the strip 23 may be indexed; a series of bins 11 are provided for the particles 10 and a supply of nitrogen to the bins 11 prevents the particles becoming jammed. Semi-conductor devices, e.g. transistors 25 may subsequently be bonded to the gold-coated support areas by conventional alloying techniques to provide, e.g. a goldsilicon eutectic bond layer, and gold wire electrical interconnections 39 may be bonded to contacts on the upper face of the transistor and to the conductors 24 of the lead frame by thermocompression. The transistors are subsequently encapsulated in epoxy resin and the lead frames 18 separated from the strip 23 leaving conductors 24 extending from each epoxyencapsulated device. Where the semi-conductor device is larger, e.g. in the case of an integrated circuit a plurality of gold particles may be simultaneously bonded to the support adjacent to each other to form a single bonding area of larger size (Figs. 6, 7, not shown). In an alternative method of selection, the particles are passed over a surface having indentations at the desired locations. |
