SILICON CRYSTAL RECTIFIERS 9 



turn be standardized, and that manufacturing facilities might be estabhshed 

 to supply adequate quantities of the device. The development and initial 

 production of the device was accomplished in a short period of time. This 

 was possible because process experience had been acquired in the insert 

 development, and centimeter wave measurements techniques and faciUties 

 were then available to measure the characteristics of experimental units 

 at the operating frequency. By December 1941, a pattern of manufacturing 

 techniques had been established so that production by the Western Electric 

 Company began shortly thereafter. This is believed to have been the 

 first commercial production of the device in this country. 



As a result of the basic information on centimeter wave measurements 

 techniques which was available from earlier microwave research at the 

 Holmdel Radio Laboratory, it was possible also, at this early date, to 

 propose to the Armed Services that each unit be required to pass an ac- 

 ceptance test consisting of measurement of the operating characteristics 

 at the intended operating frequency. This plan was adopted and standard 

 test methods devised for production testing. Considering the complexity 

 of centimeter wave measurements, this was an accomplishment of some 

 magnitude and was of first importance to the Armed Services because it 

 assured by direct measurement that each unit would be satisfactory for 

 field use. 



The cartridge structure resulting from these developments and meeting 

 the international dimensional standards is shown in Fig. 5. It consists 

 of two metal terminals separated by an internally threaded ceramic insu- 

 lator. The rectifying element itself consists of a small piece of silicon (p- 

 type) soldered to the lower metal terminal or base. The contact spring or 

 "cats whisker" is soldered into a cylindrical brass pin which slides freely 

 into an axial hole in the upper terminal and may be locked in any desired 

 position by set screws. The spring itself is made from tungsten wire of an 

 appropriate size, formed into an S shape. The free end of the wire, which 

 in a finished unit engages the surface of the silicon and establishes rectifica- 

 tion, is formed to a cone-shaped configuration in order that the area of 

 contact may be held at the desired low value. 



The silicon elements used in the rectifiers are prepared from ingots of 

 fused high purity silicon. Alloying additions are made to the melt when 

 required to adjust the electrical resistivity of the silicon to the value desired. 

 The ingots are then cut and the silicon surfaces prepared and cut into small 

 Dieces approximately 0.05 inch square and 0.02 inch thick suitable for use 

 n the rectifiers. The contact springs are made from tungsten wire, gold 

 Dlated to facilitate soldering. Depending upon the application, the wires 



