| 摘要 |
710,235. Spark discharge apparatus. EISLER, P., and HAUSER, E. July 16, 1953 [Aug. 8, 1952], No. 20054/52. Class 39(1). [Also in Groups XXII and XXXVI] A printed circuit or circuit component is made by removing unwanted parts of the material from which the circuit or component is to be formed by an electric spark erosion process which comprises bringing an electrode (cathode) into close proximity to the substance to be eroded (anode) while both are immersed in a dielectric liquid, and passing a rapid succession of D.C. pulses between the cathode and anode to produce a spark discharge which dislodges minute portions of the anode which are carried away by the liquid. The anode 10 may comprise a conductive block 11 carrying a metal foil layer 12. The lower surface of the cathode 13 carries a relief negative image 15 of the circuit, and both cathode and anode are immersed in a dielectric liquid 20. The cathode is advanced towards the anode until sparking occurs between the projecting portions 15 and the adjacent areas of the anode, causing the foil in those areas to be eroded and thus leaving a conductive pattern forming the circuit on the anode. Alternatively a plain cathode may be used, a patterned layer of insulating material, which alters the breakdown value of the gap in the areas which are to be removed from that in the areas which are to remain, being interposed between the cathode and the anode. The cathode may be in the form of a roller which may revolve about a stationary axis while the anode is moved, or which may move over the stationary anode. The method may be adapted to the erosion of metal foils to reduce or to correct inequalities in their thickness. The cathode in this case is a roller immersed in dielectric liquid and the anode a strip of metal foil moving through the liquid. The resistance of the foil between two fixed points is continuously measured by an ohm meter, any variations in thickness causing a variation in the resistance reading. The ohm meter may be connected to servo mechanisms so that such variation is compensated by varying the size of the spark gap. |
