The Research On The Thermal Resistance And Thermal Spectrum And The Process Of Thermal Transient Of IGBT

In today’s information society, Semiconductor technology is developing at high speed.. semiconductor products is changing people’s lives. In the field of rail transportation, industrial, automotive electronics, high-voltage transmission, military and civilian aircraft and ships, requires a high voltage, high current handling capability of the power of power electronic devices in order to achieve power conversion and control. Power electronics’initial product is rectifier, thyristor, power MOSFET, power GTR and other products. However, these products all have their own shortcomings. IGBT (insulated gate bipolar transistor) is a kind of power electronic devices which is develop rapidly and used widely.IGBT not only has the advantages of voltage controlling and fast switching speed like power MOSFET, but also has the advantages of lower voltage down, higher current carrying capacity like bipolar transistor. It also has the advantage of ease of integration,for example it can be integrated together in a single chip with some peripheral circuits such as over-voltage and over-current protection circuit,And we can be composed of many cells in series IGBT intelligent IGBT module. IGBT makes the overall performance including power electronic devices’ frequency, power, reliability and so on improve greatly.Power devices like IGBT generally work longer under high dissipated power in poor working conditions, so the thermal reliability research is particularly important in many aspects of the reliability of the study. According to statistics released by the United States Space Center,55percent of device failure is due to thermal failure.(1) The research on thermal resistance:thermal resistance is an important parameter reflects thermal properties of the device, it can be understood as the ability of heat conductivity by charge carrier from the micro sense, the size of thermal resistance of the device reflect semiconductor devices heat conduction and radiation capacity. Thermal resistance is traditionally considered to be the inherent nature of the semiconductor device, but the experiment proved that the thermal resistance measurements is closely related to test environments. This paper will discuss the nature and factors influence the thermal resistance testing in detail. There are two standard definition thermal resistance, defined by the International Electrotechnical Commission (IEC) and Solid Association (JEDEC).The thermal resistance test method defined by international Electrotechnical Commission (IEC) bases on steady-state process, The disadvantage of this method is the shell temperature cannot be tested accurately. To overcome this drawback Solid association defines a new method to test the thermal resistance, this method is based on thermal transients without shell temperature measurements. But the standard defined by Solid Association also has its own shortcomings, the paper will introduce and evaluate two methods in detail.(2) The research on thermal spectrum:Traditionally, transistor pn junction temperature is often assumed to be uniform, Standard electrical method is a method to obtain uniform junction temperature. But this assumption is not true, the junction temperature distribution can be found in very uneven through infrared thermal image. Get the transistor junction temperature distribution (thermal spectrum) have great influence on the thermal resistance measurements, the choice of maximum applied power, and whole system reliability. Although use infrared cameras can obtain transistor pn junction temperature distribution, but cost of testing is high, the testing process has devastating damage to the device. Transistors thermal spectrum can be found by electrical method through depth study. Electricity to obtain the transistor thermal spectrum is based on small current trend to high temperature, thermal spectrum analysis algorithm, the main parameter is the effective area and peak junction.(3) Device package detecting base on thermal transient:when we analyze thermal characteristics of the transistor, we usually analyze the steady-state process of transistors and get the transistor junction temperature, case temperature or ambient temperature under steady-state conditions. Since the process involves less steady reference point, the steady process reflects less information. Junction temperature rise or descent process is transient. Transient process lasts a long time and reflects a large amount of information. We use advanced equipment to capture the transient temperature change information in a very short time interval.By processing, we obtain the device structure of the layers of the thermal path. Furthermore we can get the device package information from structural function that we finally get.In this way, we can filter out unqualified products which has significant value for production testing.