| 摘要 |
A method of manufacturing a frame grid, having a wire wound on a frame, for use in an electronic valve, comprises coating the frame with a phosphorus-containing nickel layer by holding the frame in an electroless Ni plating bath of an aqueous solution which contains Ni ions and hypophosphite ions, in which solution the mol. ratio between the hypophosphite ions the Ni ions is at least 3, the bath having a pH between 4 and 7, until the bath contains substantially no Ni ions in the solution, thereafter winding the grid wire on the frame, and then heating the assembly at between 700 DEG C. and 800 DEG C. to secure the wire to the frame. Frames of Mo or a Fe-Ni-Co alloy and W wire are referred to. The plating, e.g. to a thickness of 2-5 microns, is carried out at a temperature of at least 65 DEG C. and, if a large number of frames are to be plated, may be carried out in a rotating drum. A specific bath contains in a half a litre, 2 gms. Ni in the form of nickel chloride and 0.22 mol/litre of sodium hypophosphite, 0.4 mol/litre of acetic acid and 0.3 mol/litre of sodium acetate at a pH of 4.5 and temperature of 85 DEG C. |
