| 摘要 |
<p>624,698. Coating with metals. BRUSH DEVELOPMENT CO. April 18, 1946, No. 11991. Convention date, May 4, 1945. [Class 82(ii)] [Also in Group XL(c)] The electrodes for a piezo-electric crystal are formed of a layer mainly of a metal such as aluminium, beryllium or magnesium which adheres firmly to the crystal surface, followed by a layer mainly of a highly conductive and preferably less corrodible metal such as gold, silver, palladuim or platinum which adheres firmly to the first metal but which would adhere less firmly if applied directly to the crystal. The two processes of deposition are preferably carried out in a vacuum and without releasing the vacuum, and the second process may be commenced before the first is completed so that the junction of the layers is formed by a mixture of the metals. Fig. 3 shows the deposition being carried out within a bell-jar 21 evacuated by pump 24. The crystal plates 29 rest on a curved holder 28 below a tungsten filament 27 which carries short lengths or aluminium and gold wire 41, 40. The filament is heated by an electric current causing the evaporation to commence first of the aluminium and then of the gold. When two distinct layers are required the two metals may be hung on separate filaments which are heated in turn, Fig. 4 (not shown). The filaments are preferably kinked to prevent the metals flowing along the filaments. The aluminium or gold may alternatively be coated on the filaments or may be evaporated from crucibles. Burnishing the final electrode improves adhesion.</p> |
