Patent GB-954569-A (GB)
Title: Improved thermocompression lead bonding apparatus
IPC: H01R43/02
Filed: 1961-10-30
Abstract: 954,569. Semi-conductor devices. ELECTROGLAS Inc. Oct. 30, 1961 [Oct. 31, 1960], No. 38797/61. Heading H1K. [Also in Division B3] Thermocompression bonding apparatus for bonding leads to an element comprises means for driving the bonding tool against the lead and element in two steps in a vertical direction, means also being provided for positioning the tool horizontally after completion of the first step. Figs. 2 and 4 show an arrangement comprising a base member 21 on which is a ball-bearing mounted carriage plate 33 movable in x and y directions. Plate 33 bears two support columns 73 on which is roller mounted a carriage block 76 which supports the bonding tool 141 consisting of a capillary tube through which is threaded gold lead wire 166 fed from a reel 144. The device to which the lead is to be bonded is held in a heated header holder 13 on base 21. The carriage block 76 is fixed to rod 110 which extends downwardly to piston 107 in cylinder 101 and upwardly to latch rod 112 which is provided with a groove 113 and shoulder 116 which co-operates with a controllable latching mechanism to limit the fall of the carriage block assembly 76. A valve mechanism enables cylinder 101 to be connected either to a compressed air supply or open atmosphere through an adjustable orifice 103. The position of carriage plate 33 and therefore of block 76 and bonding tool 141, relative to header holder 13 can be finely controlled by movement of rod 51 which is ball jointed at 58 to base 21 and also connected by a sliding ball joint 61 to carrier plate 23. A similar control rod is provided on the opposite side of the apparatus, for left-handed use. In operation, an aluminium element or other device is placed in the header holder 13 and switch 53 on rod 51 is pressed which operates MS-3 switch (Fig. 10) to energize latching relay 162 to operate valve 163 which cuts off the compressed air supply to cylinder 101, and also energizes a solenoid 122 to remove a latching mechanism (Fig. 8, not shown) from groove 113 to allow carriage block 76 to fall under its own weight. As it falls, latch rod 112 is arranged to operate a switch MS-1 which de-energizes solenoid 122 so that the latching mechanism operates when shoulder 116 reaches the desired position such that the end of the bonding tool lies just above the header in holder 13. The operator then moves rod 51 for fine adjustment of the bonding tool so that it lies precisely over the desired area on the header; a lamp and microscope are provided for this purpose. Switch 54 on rod 51 is then operated to energize solenoids 122 to release the latch mechanism from shoulders 116 so that the carriage block 76 falls a further small distance until piston 107 reaches the bottom of cylinder 101; during this fall the end of the bonding tool 141 contacts the surface of the header and the tool 141 and its holding assembly 136 and 138 lift slightly away from bushing 134 so that the bonding pressure is provided only by the weight of the tool and its holding assembly. Switch 54 also energized switch MS-2 to operate Timer 161 which after the desired period (e.g. 6 seconds) operates latched relay 162 to open valve 163 and thus supply compressed air to cylinder 101 and lift carriage block 76 to its original position. In the example the aluminium header was maintained at 325  F. during the bonding of the gold wire. The bonding tool 141 slides up the wire at this stage; the wire is then cut with a hydrogen torch to produce a small bead on the wire at the end of the tool 141 so that when tool 141 descends for the next sequence it carries wire 166 with it. The downward movement of carriage block 76 is restrained by friction engagement between concave " Teflon " (Registered Trade Mark) members 91 spring mounted on columns 73 and the side of block 76, as well as the pneumatic effect caused by piston 107 pushing air out through orifice 103. The apparatus may be used for the production of transistors, diodes, strain gauges or micromodules.