This study is to develop a novel flip-chip on board packaging for an immersion electrochemical sensor which is able to detect the concentration of a target substance fast and accurately. The package was fabricated and the electrochemical measurement was performed to validate its function especially immersion capability and sensitivity. The calibration line for uric acid known concentrations were created firstly. Then test samples were measured and their values of concentration were determined according to the calibration line. Furthermore, the measurement results using the proposed electrochemical sensors were compared to the ones from the health examination in hospital where they use timed endpoint method typically. The comparison show that the measurement error between these two methods is less than 5% to represent the high consistency in the measurement of concentrations of uric acid. However, the new package with CV measurement provide the faster results of examination than the ones of hospital in regular process (24 hours). In summary, the proposed electrochemical sensor with flip-chip on board packaging technology demonstrate high accuracy of measurement, fast processing time, and low-cost for the application in uric acid detecting. More experiments are performed to offer a low-cost and fast detecting for a target substance in various applications.