Patent GB-685912-A (GB)
Title: Method of manufacturing electrical circuits and circuit components
IPC: H05K3/34
Filed: 1947-09-30
Abstract: 685,912. Printed circuits; holders for thermionic valves. STRONG, H. V., and EISLER, P. Nov. 1, 1948 [Sept. 30, 1947], No. 26400/47. Classes 36 and 38 (i). An electric assembly comprises electrical components and a connecting circuit, at least part of the circuit being in the form of a flexible conductive pattern firmly adherent to a flexible insulating support, the support and the pattern being deformed into three-dimensional configuration, as by bending, folding or winding, but being capable of being brought back into flat form for testing purposes and re-deformed to three-dimensional form without breaking the conductive pattern or making any major disconnection of the components. The conductive pattern may be produced on the insulating support by the methods described in Specifications 639,111, 639,178, 639,179 or 639,658 and may be produced on two or more sheets of insulation such as paper or resin impregnated cloth which are subsequently superposed and interconnected as necessary. Additional layers of insulation may be interposed 'between the sheets where necessary, and parts of the circuit which are not required to open out when the unit is flattened may be permanently stuck together. Some of these sealed parts may carry portions of the conductive pattern which are arranged to form condensers. Figs. 1B and 2B show insulating support sheets on which the conductive patterns are deposited. Some of the smaller components such as condensers C2, C3 are attached to the upper sheet. The wire terminals of these components are secured to the appropriate points on the pattern by means of hot wire staples which are driven through blobs of solder previously applied to the pattern. The larger components such as the coil cans are positioned in a tray and held together mechanically to act as supports for the flexible circuit. The two sheets are folded independently to make various permanent connections, certain of which may be secured by adhesive. The lower sheet is then placed over the cans in the tray so that the terminal taps of the cans project either through slits G or clearance holes H (Fig. 2B). Those terminals projecting through slits G are bent down and soldered to the conductive pattern. The condensers C1, C4-C9 and resistances R3- R5 and R7-R13 are stapled to the lower sheet and the sheet is further folded, forming various small capacitors. The upper sheet is then laid over the lower sheet so that the remaining coilcan terminals protrude through slits G therein. The areas F in this sheet are folded back to make necessary connections between the two sheets which are then bonded together and the areas around G and F on the upper sheet are solder-sprayed through a mask and hot staples are applied through the blobs of solder thus formed, thus clamping the sheets together. The composite sheet is further folded and valves V1-V5 are placed in position. The sheet with components thereon is then finally folded so that the various parts take up the positions as shown, for example, in Fig. 15. The tray in which the assembly is fitted is itself hinged and may be folded. Specification 634,202 is referred to. Holders for valves of the miniature type suitable for use with the assembly comprise two moulded plastic parts (Fig. 6). The lower part VH1 has grooves a and metal clips s. When pressed against the underside of a patterned sheet the sharp ridges protrude through slits J (Figs. 1B and 2B) previously made therein so that the strips of patterned sheet between the slits rest in the grooves a, The clips s protrude through holes K in the sheets. The valves are arranged with their pins in the grooves a and are held in position by the upper part VH2 of the holder which is provided with grooves a<SP>1</SP>, a<SP>11</SP> and projections t for engaging clips s. An alternative form of valve holder, Figs. 20 and 21 (not shown), is made by depositing relatively widelyspaced conducting strips on the sheet, which is then crimped so that the conductive portions, on which the valve pins are to rest, lie at the bottom of the crimps. The pins are insulated from one another by the non-conductive portions of the sheet which lie between them.