Quantitative Analysis of Resistance Tolerance of Polymer Thick Film Printed Resistors

Low cost methodologies of resistor fabrications are needed for cost effective embedding of resistors into polymeric substrates. Polymer thick film resistors (PTFRs) are low temperature processable, low cost resistors with a wide resistivity range. The electrical resistance variation of these resistors is in the range of around plusmn20% after deposition and trimming procedure is employed to tune the resistances to meet specifications. This adds to the cost and complicates the fabrication process when the resistors are embedded. In this study, the influences of PTFRs geometries on the resistance tolerances were investigated. Results indicated that the resistance accuracy of stencil printed resistors was markedly higher than that of the screen-printed resistors. The screen-printed resistor edge geometries were observed to be rough. Finite element method analyses revealed that the resistance tolerances were associated with edge roughness. Remedies to reduced variations were proposed and the relationship between resistance tolerances and aperture orientations was also outlined