Abstract: Ionic contamination (IC) tester is used to test the IC content retained on the cleaned printed circuit board (PCB) surface. Because the solution temperature has direct effect on the level of IC, a high rate of IC test should be ensured by precise control of solution temperature. In practice, however, it is very difficult to control temperature precisely via the traditional PID control methods. An intelligent PID control method for the solution temperature based on pattern recognition is proposed in this paper. With the identified pattern parameters and expert experience, the PID control rules can be adaptively adjusted on line, and the temperature can be kept on its predetermined values. The simulation results show the proposed method has more excellent performance and robustness than conventional PID controllers. The practical control precision can be achieved to ±0.2℃ and the overshoot can be less than 0.5℃ in the application of ionic contamination testor, which can meet the engineering requirement.