| 摘要 |
<p>SYSTEM AND METHOD FOR TRACE WIDTH MEASUREMENT The system and method of the present invention provides a low-cost solution to measurement of the widths of traces on printed wiring boards. The system comprises a current source injecting one cycle of input current into a section of trace whose width is to be evaluated. A voltage measurement means with high input impedance is connected across said trace section. The amplitude of said input current gradually increases to a level which said voltage measurement means makes acceptably accurate measurement, and said input current is then cut off before the heat generated in said trace section becomes significantly higher than a reference temperature. The electrical resistance of said trace section is then calculated and the trace width is then evaluated from said resistance, resistivity of used trace metal at said reference temperature, together with other known parameters. A temperature measurement means is incorporated in the width evaluation for traces with very low resistance values. In an alternative embodiment, the measured resistance values of said trace section are compared against a pre-calibrated set of reference resistance values, which is useful for identification of printed wiring boards with manufacturing defects.</p> |
