Wheatstone bridge

A 4-arm bridge forming a diamond, all of whose arms are predominantly resistive, with three resistors of known values in three of the arms and the unknown resistor in the fourth.

NOTE 1    A voltage source, e.g., a battery, is connected across two opposite points of the diamond and a current-detecting instrument (e.g., a galvanometer) is connected across the other two points. The values of one or two of the known resistors are varied until no current flows through the galvanometer. The bridge is then balanced and the value of the unknown resistor can be calculated in terms of the other three.

NOTE 2    A method using the Wheatstone bridge for monitoring resistance of solder bumps in electromigration tests has greater sensitivity to resistance change than other methods. Net resistance changes due to electromigration of only the solder bumps, excluding the Al or Cu traces, can be deduced by this method.


JEP154, 1/08