| abstract |
1,199,848. Integrated circuits. MOTOROLA ..Inc. 22 Nov., 1968 [15 Dec., 1967], No. 55557/68. Heading H1K [Also in Division B3] Leads are attached to raised coplanar aluminium bonding pads 12 on an integrated circuit wafer 11 by aligning the free ends of leads 24 (Fig. 6) extending inwardly from a frame member 21 with the pads and bonding them thereto in a single step. This is effected without heating by sandwiching the lead ends between the block and an anvil 32 no larger than the block itself and applying pressure and transverse high frequency vibrations (60 kc./s.) to the assembly via bonding needle 33. The free ends 54 of leads extending inwards from a larger frame member 51 of heavier gauge material such as nickel, copper, steel or KOVAR (RTM) are then aligned with portions of the first leads and bonded to them. Parts of the first leads extending beyond the bonds are removed before or (as shown) after this last operation. A number of frames 21 are preferably stamped or etched from a continuous strip of aluminium or copper 2 mils thick so that they can be wound on spools and run through the bonding apparatus in a continuous process. The anvil 32, bonding needle 33 and the backside of the wafer are roughened to facilitate communication of vibrations from the needle to the bonding areas. Lateral spread of the end of each tapered lead 24 during bonding causes it to kink adjacent the bond into the recess 35 provided for the purpose so that the leads stand proud of the edge of the wafer. Although leads 24 may be soldered, brazed, or bonded by a thermocompression or ultrasonic technique to those of frame 51 it is preferred to form resistance welds using a cylindrical welding element (Fig. 8, not shown). If desired, before this operation, the wafer and leads are stuck to a supporting disc of ceramic (shown in phantom) with epoxy resin or between two such discs. Finally leads 24 are severed from the first frame with the aid of a cylindrical knife edge or by simply ripping away the frame. The resulting elements may be potted in resin or mounted in ceramic flatpacks before removal from the second frames. |