126 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1957 



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JFMAMJJASONOJFMAMJJASONDJFMAMJJASOND 

 1954 1955 1956 



Fig. 5 — Paper capacitor yield. 



esses. The art of silk screening was applied to deposit silver paste in a 

 specific area or areas on each side of a lamination. A sharply defined 

 rectangular area was required so that when superimposed one over an- 

 other the desired capacitance would be obtained. Cementing of mica 

 laminations onto machined methacrylate forms presented some addi- 

 tional problems through the bowing of the mica laminations as the ce- 

 ment cured. Obtaining screens that would give the proper length and 

 width dimensions for the coated area, was another problem. A silk screen 

 woven of strands of silk obviously limits, by the diameter of the threads, 

 the extent to which the dimensions of an opening may be increased or 

 decreased. Beryllium copper U-shaped terminals were used to clamp 

 the layers of mica together into a stack. Control of the pressure used in 

 crimping these terminals was found to be very critical in view of the 

 exceptionally tight limits on capacitance and stability. Fig. 6 shows the 

 composite yield at various times for all mica capacitors. 



Resistors. There were three designs of ceramic resistors, which were 

 resistance-wire wound on ceramic spools. These were intended to be 

 assembled into the hole inside the core tube on which the paper capaci- 

 tors were wound. Special winding machines equipped with binocular 



