| 摘要 |
1,255,253. Printed circuits. MINNESOTA MINING & MFG. CO. 31 Jan., 1969 [1 Feb., 1968], No. 5296/69. Heading H1R. A multilayer printed circuit is formed by screen printing in succession conducting paths and ceramic layers on a refractory base and firing the composite structure. A green ceramic base 10 is provided with holes 12, 14, 16 and then fired after which metal pads are formed on the underside of the base 10 around the holes by squeeging a metallic paste through a screen. Some of the metallic paste passes through the holes 12, 14, 16 to provide a connection therethrough. On the opposite side of the base a conductor pattern is screen printed as shown in Fig. 2 some of the strips connecting with the metallic paste in holes 14, 16. By choosing the paste the conductors may'be of high or low resistance. Following the screening of the conductor pattern a ceramic layer is screened on to the base 10 to cover the pattern except for square holes corresponding to metallic pads 31, 33 holes corresponding to holes 12, 14, 16 and further holes which will provide connection to strips on the base 10. The metallic pattern shown in Fig. 4 is then applied over the ceramic layer, the metallic paste penetrating through the holes in the ceramic layer to form the interconnections between conductors in the various levels thereby providing cross-overs of the conductors. In order to protect the surface of the layer of Fig. 4 and to provide a non- conducting base for metallized seal rings the insulative pattern of Fig. 5 is imposed on the top of the layer of Fig. 4 metallic rims 71, 72a, 73, 74a being provided as shown. After a preliminary heating to remove organic binders the structure is fired to sinter the metal and ceramic constituents. Nickel, gold or other metals may then be applied electrolytically or electrolessly to provide terminals. If an unfired ceramic base 10 is employed then in order to prevent deformation during the final firing stage a metal pattern is provided on the back of sheet 10 over which an insulative layer is applied to which is applied the metallic contact pads, Figs. 6, 7 (not shown). |
