1. Introduction Resistance may reflect Chip , Welding layer and the shell of the sintering or bonding quality, the thermal resistance characteristics of the Transistor Has a critical influence on reliability. Parameters and the thermal resistance transistor Vbe use under certain conditions, to satisfy a mathematical relationship, indirectly, by measuring the parameters of the transistor Vbe to test the thermal resistance parameters, with the measurement of high efficiency, low costs, the advantages of the device without damage, but the thermal characteristics of transistors with complex, sensitive and unstable characteristics. To achieve the practical need for greater measurement accuracy difficult, at present, foreign copy omega countries have developed a theory of resistance testing system. Urgent need for the domestic market, higher transistor test cost-effective screening device. The system can power bipolar transistors (NPN and PNP type) and steady-state thermal resistance measurement of transient thermal resistance, but also test diodes and LED Thermal resistance. By loading test conditions to test the system, the thermal resistance of the transistor characteristics to reflect the temperature changes in the measurement data displayed on computer screen and, based on rapid screening test results. System has access to detection and shock detection feature to prevent poor contact and the shock caused by temperature measurement errors, the system also has the anti-avalanche of self-protection circuit, used for measuring safety zone SOA (safe operating area), to improve the test system stability.
2. Resistance testing technology Transistor thermal resistance generally chip, chip tube socket contact resistance and thermal resistance of the composition of shell. Concerned with the production of sintered silicon chip tube socket contact resistance the most difficult to control, sintering is not good, would greatly increase the tube socket chip thermal resistance, the use of excessive junction temperature will be as a result of device failure. Transistor thermal resistance under pulsed conditions of work for the junction temperature rise and power dissipation pulse amplitude ratio. Of the power transistor is usually shell temperature as the temperature reference point, which was expressed as: jc = (Tj-Tc) / P, which for the chip junction temperature Tj, Tc for the shell temperature, P for the pulsed power. Resistance attributed to the pulse power measurements P, Tc shell temperature and junction temperature Tj of measurement, apparently the transistor junction temperature Tj can not be measured directly. To this end, using the emitter forward voltage drop Vbe and junction temperature Tj in a certain context has a good linear relationship: Vbe = M? Tj, where M is temperature sensitive parameters, the relationship was used as a measurement of transistor the physical basis of device thermal rockford grade fake watches resistance, while measurements Vbe need to set the following main parameters, which are Vcb (C, B voltage between electrodes); Ie (load current); Im (induced current); Pt (power time) ; Dt (delay time); upperlimit (limit); lowerlimit (lower limit). Since each manufacturer on some of the differences in process, although sometimes the same type of pipe, but belong to different manufacturers products, imposed by pulsed power, testing time and temperature sensitive parameters chosen are different. 3. Test system architecture Basic framework of resistance testing system is computer controlled by software, precision analog and digital circuit, the conditions imposed on the device under test results of samples Filter
more calculate a series of process control identification to complete the measured device electrical parameters of the automatic test, the entire process of each test is less than 0.2 seconds. System main board analog multiplexer, digital multi-board, ADC board, Im board, Ie board and Vcb plates, shown in Figure 1. 4. vbe test flow chart Vbe is an important parameter of the transistor, the transistor's thermal resistance with a quantitative linear relationship, which reflects the ability of power transistors, the transistor's packaging process and failure analysis of important guiding significance to the Vbe testing process as shown in Figure 2. 5. Software function implementation module System software design is the use of visualC cheap armand nicolet watches + + and assembly language to complete a combination of both, the software function to implement the module are: 1, household management module, the program cartier pasha seatimer online runs need to determine the identity of the user, the user types of cartier tank francaise replica operators, maintenance workers, engineers, system administrators. Operator permissions is to run the test program; maintenance staff permission to test the self-test and calibration equipment; engineers permission is edited test procedures; system administrator has full permissions. 2, edit modules for device selection, classification setting, commissioning, establishing testing procedures, the initial test program interface shown in Figure 3: 3, run the module, according to the user's parameter settings, the device testing, and testing results and data displayed on the computer screen.
4, other modules, a system of tools, screening modules, print modules. System tools, with self calibration of instruments for self-test on the thermal resistance test systems, calibration, field test; filter module, the user can set filter criteria based on the different devices tested, the test results to a screening machine; Print module, according to pre-set, the test results and data to the appropriate format for printing, for analysis and archiving. I am an expert from home-burglaralarms.com, while cartier knockoff watches we provides the quality product, such as Wireless Baby Monitors , 3G Video Alarm Manufacturer, 3G Video Alarm,and more.