Patent GB-1031288-A (GB)
Title: Improvements in automatic fabrication of microcircuitry
IPC: G03G15/22
Filed: 1963-07-18
Abstract: 1,031,288. Etching; printing processes. RANK XEROX Ltd. July 18, 1963 [July 18, 1962], No. 28434/63. Headings B6C and B6J. [Also in Divisions G2 and H1] Apparatus for forming printed circuits on to rigid plates 31 comprises a rotatable drum 11 supporting a plurality of master circuit patterns 10 each consisting of an electrically insulating circuit image on a conductive backing, selection means whereby a chosen pattern 10 is rotated to be adjacent electrostatic charging station 20 to form an electrostatic image which is then developed by cascade powder apparatus 25 and transferred at station 30 to a plate 31, heat or solvent vapour fusing means 63 to fix the image, and conveyer 88 whereby the plate is passed through solution 105 to etch away the plate surface unprotected by the powder resist image. The powder is then removed by solvent 107 and the printed plate is deposited at 111. The master patterns 10 may comprise a persistent developable image which may be erased after prolonged use as in Specification 977,904. In the preferred embodiment a xero-printing plate as disclosed in Specification 675,398 is used to provide a permanent image. The plates 31 comprise a dielectric substrate 45 of a phenol formaldehyde laminate, a ceramic material &c. as in Figs. 3 and 5 (not shown), supporting a resistive layer 46 on which is a further conductive layer 47. Elements 54 such as transistors may be inserted through holes 52. Different circuit plates may be assembled by tabs 34 to form complete units. Patterns 10 are carried on drum 11 in peripheral columns each associated with a plate processing unit A, B, C or D, each unit having a magazine 32 and a conveyer 33. Motors M-3 selectively actuate feeder bars 38 to push a plate 31 to its transfer station 30, the corona charging unit 21 being axially movable to charge the appropriate pattern, in its column. For continuous operation, magnetic indicia 50 on drum 11 are sensed by head 51 which controls motors M-3. Corona generator 60 charges the back of each plate for electrostatic image transfers. Conveyer 33 has spaced sprocket driver chains 64 carrying brackets 69 as in Figs. 7 and 8 (not shown) on which are mounted spring-loaded slides 67 movable in and out by engagement with camming rails 75 whereby gripper fingers 66 on the slides hold or release a plate 31. The plates leave fusing station 63 and are moved to abut gate 90 adjacent process conveyer 88. Gate 90 is lowered by engagement of pin 96 on the conveyer with lever 97, and a plate enters an open bucket 92 for transport through baths 105 and 107. The plates may be re-processed with formation of additional circuits as on Figs. 9 and 10 (not shown), in which conveyer 124 returns the plates to a magazine 129 adjacent conveyer 33. The etching bath may be a ferric chloride solution if copper is to be dissolved, while nickel or aluminium may be removed by nitric acid or sodium hydroxide respectively. Chromium is removed by first dusting with zinc powder and then dipping in hydrochloric acid. Superposed layers of different materials may be selectively etched, as when nitric acid is used to etch magnesium oxide but not underlying aluminium, or a layer of chromium underlying nickel.