Patent GB-1504252-A (GB)
Title: Method and apparatus for obtaining electric interconnections of electric components on a base support
IPC: H05K13/06
Filed: 1976-03-02
Abstract: 1504252 Making connections; soldering COMMISSARIAT A L'ENERGIE ATOMIQUE 2 March 1976 [12 March 1975] 08336/76 Headings B3A and B3R [Also in Division H1] In fabricating an electrical interconnection circuit for a component assembly (Fig. 1), an insulant support 2 is provided with printed circuit tracks and insulated studs defined by etching, and is coated with adhesive resin 4 except for studs 6, conductive pads 8 and metallized through holes 10 and for a connector 14 of etched conductive tracks 14, ground line 12, and supply line 13. The studs 6 and through holes 10 serve for the attachment of discrete components, e.g. relays, capacitors, or resistors, and selected zones are interconnected by insulated wires bonded to the adhesive resin. Manufacture is effected (Fig. 2) by apparatus for heating, stripping, turning, soldering and off-cutting of the insulant interconnecting wires, and comprises a central barrel 20 electrically connected over rotary contacts, e.g. 22 to a rotatable frame 24 driven by motor 26 over pinion 28 and supported on bearings 30, 32. Wires 34 of the barrel supply electric currents to the contacts, insulated wire is fed from drum 36, and strip solder from a storage drum through tube 29 to a position opposite a stripping and tinning bit 42 of Nickel or nickel coated copper which is displaceable between an engaged and disengaged position relative to the wire (Fig. 4). A blower directs air over a tube, to the bit 41 when in the disengaged position 42 to remove oxidized solder into container 80. Arm 44 of the rotatable frame 24 is spring loaded to impress a grooved antiadhesive laying wheel 48 on the substrate 50, and the frame also carries a further channel shaped, e.g. tungsten soldering bit 51 and a cut-off knife 52 magnetically displaceable, to solder a wire 40 to stud, e.g. 53 and to offcut the surplus wire. Arm 44 and knife 52 are electromagnetically displaceable by devices 55, 57. In operation, a digital automatic control system operates the process elements synchronically so that motor 26 orients the frame 24 in the required direction of displacement of the wire, the latter is heated by coil 38 prior to soldering, the bit 4 strips the insulation from wire 40 and applies a required quantity of solder through tube 29 to the required point thereon. When the latter is located over the stud, displacement of the circuit board by table 50 movable in XY co-ordinate directions is arrested, after which bit 5 is applied to form a soldered joint, and knife 52 cuts off the surplus wire. Motor 26 then rotates the frame and the table is activated to present the insulated wire to a further stud, while wheel 48 presses the wire into the adhesive resin layer 4 (Fig. 3 not shown), the rotary head being retracted during transferance. The completed circuit assembly (Fig. 7) comprises an epoxy-glass support 2 coated with adhesive thermosetting resin 4 and having through holes coated with a copper layer 54 and lead-tin layer 106. Studs are interconnected by soldered insulated wire 40 at joints 108, 110, while resistors or capacitors may be interconnected e.g. at 112 between through holes on either or both faces. Alternatively a laser beam may be employed to solder the insulated wires to the connection studs, replacing the soldering bit 51. Tinning and stripping are then unnecessary, and the laser may also be pulsed for cutting. The substrate may be pre-formed by drilling, electrodeposition of copper, turning, and etching, and the adhesive resin may be cured by irradiation.