| 摘要 |
1,228,599. Printed circuits. INTERNATIONAL BUSINESS MACHINES CORP. 20 June, 1968 [6 July, 1967], No. 29363/68. Heading H1R. [Also in Division H2] In the manufacture of a printed circuit, conductive blocks of low melting point metal having a surface tension such that when the metal is heated it has a tendency to form into a globule are incorporated with the circuit lines as sections thereof whereby the circuit lines can be selectively opened or closed by heating of the metal blocks. In the embodiment of Figs. 6, 7 a glass fibre cloth impregnated with epoxy resin substrate 11 laminated with a metal foil sheet is coated with a photoresist and exposed to light through a negative mask of the desired metal blocks. After washing and etching the metal foil is provided with a plurality of rectangular recesses and a tin-lead solder is flowed over the board and exposed photoresist so that it collects in oblong globules in each etched area, Figs. 3, 4 (not shown). Thereafter the board is pressed by a heated platen to form solder slugs 17, 18, 19. The exposed photo-resist is removed and a new coating applied. After exposure to light through a negative mask and etching circuit lines 21 to 26 are left arranged as shown. The circuit shown in Fig. 6 may be changed to that shown in Fig. 7 by applying localized heat from an electron or laser beam to any one or all of the solder slugs 17, 18, 19. When the slug 17 reaches its molten state it forms a globule because of its high inherent surface tension and because the substrate 11 is not wetted by the solder the slug 17 breaks up into globules 17a, 17b thereby breaking the circuit. Slugs 18, 19 each form a single large globule on heating thereby completing the circuits as shown; |
