Some Effects of Fabrication Parameter Variations on Thick Film Resistive Elements

摘要

A study of the interrelated effects of screen printing parameters on the yield of thick film resistive elements, in terms of uniformity and resistance values, demonstrated the impracticability of reducing the dimensions of resistor lines beyond the thickness provided by conventional 200-mesh screens and beyond lengths and widths of 30 mils. The effects of line orientation were found to be minimal, but nevertheless predictable, while those of the printing sequence were of great importance. Printing resistors below conductive terminations imparied electrical continuity. Analysis of width and resistance relations showed line perimeters to consist of a uniformly bevelled edge. Data are given to define this effect so as to provide a correction factor in circuit layout. A comparison of uniformity of resistances obtained on specially selected substrates compared with 'as-received' substrates showed a minimum of improvement. Application of the aforementioned effects to the fabrication of a bias resistor network demonstrated a lack of control of untrimmed resistance values when extremely short lengths, located close to resistors of longer lengths, were printed. For resistors of equal width and of the same paste, proportionality between resistance value and length was obtained after modifications in procedure to reduce substrate irregularities for the resistor printings, and changing the conductor to one of a silverfree composition. (Author)