高效在线测量加速实验中双极晶体管结温方法的研究

针对晶体管在加速寿命实验和老炼实验等实际工程中结温的在线测控问题,本文基于大电流电学测温方法研究了型号为2N3055的双极大功率晶体管在恒定的集电极电压V_(ce)和集电极电流I_(ce)条件下发射结电压V_(be)随着温度T变化的对应关系.研究结果表明,温度在40—140℃范围内时,在集电极加载大功率电流电压的条件下,发射结电压随温度上升而线性减小,基极电流随温度变化不超过4%.通过理论推导恒定功率下发射结电压与温度的数学模型,证明了当基极电流数值随温度变化不超过4%时,V_(be)-T关系曲线呈线性且理论上引起的温度误差不超过0.5℃,以此为基础推导出一种新的在线测量加速实验中结温测试公式.最后利用Phase11进行对比验证实验,证明了该方法的正确性.

High-efficiency on-line measurement of junction temperature based on bipolar transistors in accelerated experiment

Junction temperature is an important factor affecting the reliabilities of semiconductor devices. Usually, the method of measuring the junction temperature is not tested on-line. However, due to the fact that neither contact thermal resistance nor thermal resistance varying with temperature is taken into account, there exists an error in the off-line measurement. A way to solve the problem of off-line measurement is to measure the junction temperature on-line. In this paper, we propose an electrical method of measuring the temperature rise of high-power bipolar transistor in the working condition. The measurement method is based on a good linear relationship between base-emitter voltage (V_be) and temperature during the steady-state. Taking the model 2N3055 of bipolar high power transistor for example, in this paper we study the relationship between base-emitter voltage (V_be) and temperature under the conditions of constant collector-emitter voltage (V_ce) and collector-current (I_ce). During the experiment, the device is placed in a thermostat. A voltage is applied to the device collector, a current is applied to the base, and the emitter is earthed. Before the device is measured, we set different temperatures and make sure that the equipment is in a steady state. In order to avoid the effect of self-heating, the pulse current is used in the experiment. The pulse width and the period are 500 μups and 1 ms, respectively.
The research result shows that the base-emitter voltage (V_be) decreases linearly with temperature increasing and the base-emitter current is changed below 4% when the temperature is in a range of 40 ℃-140 ℃. In this paper we also deduce the mathematical expressions for base-emitter voltage (V_be) and temperature under a steady state. It is proved that the V_be-temperatrue curve is linear and temperature error is less than 0.5 ℃ when the changes of base current value does not exceed 4%. Therefore, in this paper we deduce a new method of testing the junction temperature in the speeding up measurement experiment. By measuring any of the reference points on the calibration curve under certain experimental conditions, the junction temperature can be calculated quickly according to the proposed formula.
Finally, the phase 11 is used to verify the proposed method. We measure the thermal resistance upper the case for the junction of model 2N3055 and the thermal resistance under the case for the junction of model 2SD1047. The measurement results of phase11are compared with the junction temperature calculated using the test formula. The results show that the error of junction temperature between the two methods is less than 0.7%, which is corresponding with the needs of practical application. It proves the correctness and feasibility of the method.