Patent GB-1143957-A (GB)
Title: Improvements in or relating to electrical circuit structures
Inventor: BINGHAM KENNETH CHARLES ARTHUR
IPC: H01L23/538
Filed: 1965-07-13
Abstract: 1,143,957. Printed circuits. INTERNATIONAL COMPUTERS Ltd. 5 July, 1966 [13 July, 1965], No. 29736/65. Heading H1R. A printed circuit comprises a first set of parallel conductors 8 formed by vacuum deposition, and a second set of parallel conductors 10 similarly deposited over the first set at right angles thereto, and insulated therefrom by interposed strips 9 of insulating material, desired connections between conductors of the two sets being effected at cross-over points by connecting links 15. As shown, power conductors 3 are formed on a sintered alumina ceramic substrate 1 by silk screening thereon a pattern of Au in a glass matrix, followed by firing. An insulating layer 4, having a matrix of rectangular apertures 5 therein, is formed by silk screening a glaze over substrate 1 and conductors 3, followed by firing. An earth plane 6 is next formed, by the same method as conductors 3, having apertures which register with apertures 5, and projections 7 which protrude into the apertures. A further insulating layer 18, similar to layer 4, is next deposited, and conductors 8 are formed on layer 18 by the vacuum deposition of Au through a mask. A layer of photo-resist is now applied followed by an evaporated Au layer and a second layer of photo-resist. The second layer of resist is exposed and developed to form a protective pattern over conductors 10; the rest of the Au layer is etched away, so uncovering the underlying first resist layer, which is exposed, developed, and removed except below conductors 10, where it remains to form insulating strips 9. Discontinuities 11 are produced where required in conductors 8, 10 by spark erosion, and conductive links 15, 16 between selected conductors 8 and 10 are formed by the vacuum deposition of A1 through a layer of photo-resist exposed at the site of each link to an electron beam and subsequently etched. Electrical components 2, such as integrated circuit chips, are positioned in apertures 5, contact areas on the components being ultrasonically welded to power conductors 3, earth plane projections 7, and areas 17 of conductors 8, 10 which project into apertures 5; either the contact areas or the circuit terminal areas may be plated with Al or Au to facilitate welding. Modifications.-The substrate 1 may be of glass, Si, or a conductive material such as Al coated with an insulating material such as alumina, SiO, or photo-resist. The components 2 may be inserted in recesses in the substrate, connection to the circuit being by vacuum deposition; or apertures in the substrate may be temporarily filled with wax during the formation of the conductors which are reinforced by electroplating, the wax being subsequently removed and replaced by the components which are connected into the circuit by welding or deposition of A1 links. Other noble metals may replace Au, and conductors 3, 8, 10 may be formed by the vacuum deposition of Cr or Ni-Cr followed by Au. Insulation layers 4, 18 may be of exposed, developed photo-resist, or a polymer, or SiO; and layer 18 may be formed of strips similar to strips 9. In place of spark erosion, discontinuities in the conductors mav be formed by electron beam or laser beam scanning, chemical etching, mechanical scribing, or condenser discharge.