The effect of impingement cooling using a dual synthetic jet actuator (SJA) with improvement of exit configuration has been investigated experimentally. A hump with cross section of a half-elliptic shape was attached to the flat between the two exits of the SJA. Due to Coanda effect, spread of the synthetic jet was enhanced. Two different humps with height to half width ratios of e = 1.0 and 1.5 have been tested. An infrared camera was utilised to record the temperature of the cooled plate. Statistical results of the temperature have been discussed. With humps, average temperature of the impinged area decreased about 2.6 °C and 0.6 °C corresponding to e = 1.0 and 1.5. Standard deviation of the temperature in the impinged area was almost unchanged. Effective cooled area on the plate was enlarged significantly. For e = 1.0 and 1.5, the effective cooled area with temperature below 20 °C increased by 1.1 and 0.5 times. It means that the improvement is very helpful to applications of electrothermal cooling that involve large cooled area.