ABSTRACT
When fired in a pattern a) the resistor shall function properly with application of electric field to its terminations. In case b) some very high gradients of electrical field shall be present across some parts of the resistor, affecting the conductor-glass boundaries. That may result in permanent changes in resistor value and stability, local hot spots and resistor breakdown. It is not unusual for a substrate to have 5 to 7 separate screening operations. They may include several conductor, dielectric and resistor inks. Large variety of materials, final thickness, pattern sizes and dependability on direction of screening have strong influence on distribution of resistor values. The as-fired values typically fall within boundaries shown on Figure 2-4, and may be up to 50% off the designed value. In order to achieve the specified value, resistor has to be adjusted using laser or abrasive trimmer. The latter is used only in limited applications when the volume is very
a) b) Figure 2-3 Distribution of conductive particles in a fired resistor film: a) uniform sintering pattern, b) random sintering pattern.
