988 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1953 



specification. This condition is inherent in the design and methods of 

 manufacture of this type of product, as the process consists of an inte- 

 grated group of manually-controlled operations. The following brief sum- 

 mary of these operations will give a better appreciation of the difficulties 

 encountered in the control of a product of this type: 



3.311 Mica cut to size and silver coated 



A. Inspected for visual and mechanical dimensional defects. 



B. Laminations silver coated by silk screen process and fired. 



3.312 Assembly 



A. Laminations stacked by count and interleaved with lead foil. In 

 this state, the stack consists of laminations having multiple silvered 

 areas. 



B. Dip-sealed in Bi-Wax to hold pileup firmly together for subsequent 

 operations and excess wax pressed out of pileup. 



3.313 Sectioning 



A. Section the multiple stack of laminations by punch and die to 

 provide individual capacitor pileups. 



3.314 Preliminary stacking to capacitance range 



A. Rough adjust the individual capacitor pileups by adding or re- 

 moving single laminations to meet a broad capacitance range which is 

 capable of adjustment. Terminals are then attached by crimping. 



3.315 Adjusting 



A. Adjust by scraping silver from outer layer of mica until capacitance 

 is within ±0.2 mmf of specified value. 



3 .3 1 6 Molding — Stabilizing 



A. Mold in mica-filled molding compound. 



B. Stabilize by temperature cycling. 



In a proces.s of this type a number of individual operations combine to 

 determine the final product capabilities. Control of distribution is diffi- 

 cult since many of these operations tend to substantially modify the 

 distribution obtained in previous steps of the process. Figs. 9 and 10 show 



