Patent GB-1369042-A (GB)
Title: Electromagnet force system for integrated circuit fabrication
IPC: B23K20/02
Filed: 1971-10-04
Abstract: 1369042 Welding by pressure HONEYWELL INFORMATION SYSTEMS Inc 4 Oct 1971 [5 Oct 1970] 46147/71 Heading B3R A bonding device suitable for integrated circuit fabrication comprises a tool for applying pressure to a workpiece, electromagnet means for applying force to the tool, means for sensing the force applied to the tool, means for sensing the tool movement due to workpiece deformation and means responsive to the force sensing means and to the movement sensing means to apply a force to the tool in accordance with a predeter-  mined fabrication programme. In an embodiment a bonding assembly is carried on a support 14, Fig. 1, connected to a vertically movable motor driven means 16. The force applying means 5 of the assembly comprises an upper housing 8, Fig. 3, and a lower housing 12, a water cooled support 55 fixed between the housings carrying a toroidal coil 60 supplied with current by leads 62. A vertically movable annular iron core 70 has a wall 76 surrounding the coil and a core 70 within the coil and is mounted on a shaft 75 slidable in a bushing 77 in the housing 8. A displacement transducer assembly 80 has a fixed portion 81 attached to the housing 8 and a movable portion 82 carried on a shaft 78 secured to the shaft 75. A rod 88 carrying cooling fins 86 is secured to the core 70 and carries a force transducer 98 in a housing 94, a shaft 96 extending from the transducer 98 carrying a tool mounting plate 50 via a cross-bar 44 and guide shafts 46. The housing 94 has flanges 91, 92 engageable with adjustable stops 95, 97 on the housing 12 and a spring 42 is arranged between a flange 43 on the housing 12 and the housing 94. The tool secured to the plate 50 may be a resistance heated head 30, Fig. 1, an ultrasonically vibrated sonotrode or a thermocompression tool. The latter tool comprises a member 110, Fig. 6, having a reflector 112 mounted therein for directing radiation from an infra-red lamp 102 mounted in a parabolic reflector 104 behind a condenser lamp 105 on to a hemispherical surface 128 of a lens 130 mounted in the member 110. The lens is of glass or the like and has a polished surface 132 for application to the workpiece and the infra-red radiation source may be mounted in the travel mechanism 16. Electrical and electronic circuits connected to the apparatus include a position programme generator and a force programme generator connected to the transducers 80, 98 via comparators and a voltage programmable current source connected to the coil 60. In use in response to a signal from the position generator the tool is moved towards the work by the motor 18 and when the tool engages the work a signal from transducer 80 is fed to a comparator which provides an error signal to the position generator which stops the motor 18. The force generator is initiated by the position generator and causes the voltage programmable current source to supply current to the coil 60, the energy supply to the tool being subsequently started. Force applied to the tool is sensed by transducer 98 which feeds a signal to a comparator and then to the force generator and minute workpiece deformation is sensed by transducer 80 which feeds a signal to both comparators. The drive is caused to raise the tool when the appropriate said formation is sensed.