While advancements in microprocessor speed, memory density and monolithic IC integration grab many headlines, the destiny of discrete passive and active components is not often discussed. Are the discretes disappearing? Definitely not. Many discretes are used in diverse applications such as automotive electronics and communications, medical, consumer and industrial equipment.
Passive discretes, specifically inductors and capacitors, are indispensable as basic filter components, not only for RFI or surge suppression but also for data acquisition applications when digital filtering is not appropriate. Other members of the passive class—transformers and opto-couplers—are ideal for providing circuit isolation.
Passive-component test instruments, specifically LCR bridges, have existed for many years, and models are still being introduced to keep up with changing technological requirements and applications. Some now test components at their operating frequencies and voltage levels; others are smaller to meet growing field-application requirements.
Discrete active components, a vast array of semiconductor devices including MOSFETs and insulated gate bipolar transisters (IGBTs), are often employed when high current, voltage or power levels are involved. They are typically used in power-control, power-factor correction and regulator circuits and for energizing relays and actuators.
Their number and types continue to grow, especially in automotive, consumer appliance and industrial applications. As a consequence, more test engineers may have to specify or use the higher-power stimuli and instrumentation needed to test these active devices.
High-power semiconductor test equipment is unique in several ways. “To perform dynamic parametric evaluations of IGBTs, test levels in the range of 2,000 V and up to 1,000 A may be involved,” said Hans Giessibl of SZ Testsysteme. It’s a major challenge to Protect the test equipment and the user from the dangerous situations that may occur when a DUT is defective.
“When a DUT blows up, and some definitely will, the test equipment must not be damaged,” said Rodney Schwartz, Vice President at Integrated Technology. “On a new tester, we spend about 60% of the engineering design time implementing ways to protect the tester and the user from the device.”
Safeguarding the test equipment is sometimes accomplished by including ultra-fast cutoff circuitry that disconnects the DUT from the ATE in the case of a malfunction. “But cutoff circuitry is not without problems. The added components have capacitance and inductance that can adversely affect the DUT environment,” advised Mr. Giessibl.
The need for unique and creative safeguard solutions was also stressed by Mr. Schwartz. Today’s power semiconductor devices operate at very high switching speeds and power MOSFETs and IGBTs can generate extremely high di/dt waveforms. Consequently, when performing dynamic tests, any series inductance—even a short piece of heavy wire—can be detrimental. Including additional series-limiting or disconnecting circuitry in the DUT to protect the tester is often not practical, he commented.
“Another major problem is making socketed connections to the DUT,” Mr. Schwartz continued. “Most power device packages have been around for some time and device manufacturers continue to put new technology into old packages, even though they may not be optimum.
“For example, the venerable TO-3 package slows down the switching times of a power MOSFET significantly over that obtained with a TO-220 package because of lead inductance. Currently available sockets for these packages further degrade switching performance. To even approach the real wired-in performance the device is capable of, the test equipment must provide very specialized interfaces,” Mr. Schwartz concluded.
Fortunately for quantity users or manufacturers of power discrete devices, companies such as SZ Testsysteme and Integrated Technology have solved these special problems. But test engineers who have only an occasional need for testing these types of devices and assemble their own test setups will have to pay special attention, not only to technical performance but also to safety aspects.
Component Test Products
Discrete Semiconductor Tester
Features Multiple Test Heads
The ITC5730 Dynamic Parametric Test System mainframe accepts test heads that perform nondestructive transient measurements on semiconductor devices, such as IGBTs, power MOSFETs, diodes and other bipolar devices. The mainframe includes the instrumentation and software required to perform switching time, switching losses, gate charge, Trr/Qrr and other transient tests. Test heads are optimized for specific types of transient tests and are provided with personality boards to accept the various device types, device packages and circuit arrangements. Mainframe: $65,000; Test Heads: from $6,000. Integrated Technology, (602) 968-3459.
Varied Discrete Tests
Supported by ATE Series
The M3020 Series Advanced Discrete Test System tests individual power semiconductor devices, including IGBTs, MOSFETs, power FETs, transistors, diodes, thyristors and triacs. The M3020ST tests static parameters with multiplexed test heads. One M3020DYN test head checks static parameters on packaged devices to 300 A and 2,000 V. Another test head verifies dynamic parameters, including avalanche, short-circuit current, power, time measurement and thermal resistance. The M3020MD Parallel Quad-Die Discrete Tester performs DC parameter checks. $150,000 to $525,000. SZ Testsysteme,(408) 744-0793.
Component Tester Features
Throughput of 60,000 Devices/h
The Model 5300HS tests a variety of discrete components, including MOSFET, IGBT, transistor, diode, zener, J-FET, MOV, opto, triac, SCR, quadrac, regulator, SSOVP, diac, STS and sidac devices, and relays. Features include three-station multiplex operation, fast single test/measure, throughput to 60,000/h, real-time math, a handler/prober interface, self-test, auto calibrate, datalog, binning, lot summary, intuitive programming, 1-kHz ZZ test, a programmable soak, a scanner and built-in statistics. It provides current to 1,200 A and voltage to 5 kV, and has 1-pA/1-mV resolution. From $32,500. Scientific Test, (214) 487-9421.
LCR Meters Perform Over
Range of 100 Hz to 100 kHz
The SR700 Series LCR Meters measure R+Q, L+Q, C+R and C+D at frequencies ranging from 100 Hz to 100 kHz. The SR715 has a basic accuracy of 0.2% and the SR720 has an accuracy of 0.05%. Three drive voltages and five source frequencies may be selected. Up to nine instrument setup configurations can be stored and recalled. Automatic binning and limit features and RS-232, optional GPIB and parts-handler interfaces facilitate production testing. SMD and Kelvin clips are optional. SR715: $1,295; SR720: $1,995. Stanford Research Systems, (408) 744-9040.
Hand-Held Bridge Suited
For Sorting, Matching
The Model 878 Hand-Held LCR Bridge measures inductance (0.1 µH to 10,000 H), capacitance (0.1 pF to 10 mF) and resistance (1 mW to 10 MW ) with an accuracy of 0.7%. Dual digital readouts simultaneously display capacitance and the dissipation factor or inductance and Q. A minimum/maximum/average function records the running average and the highest and lowest readings. The relative mode stores the value of a reference part, then shows (±) differences. An audible alert can indicate when a component is outside of tolerance. $275. B+K Precision, (312) 889-1448.
RLC Meter Has
Charged Capacitor Protection
The Model 7400C is an impedance-measuring RLC meter with charged capacitor protection. It handles capacitor discharge surge currents up to 50 A for one 60-Hz cycle. Also, a front-panel-mounted fuse protects the AC source from capacitor discharges. Because of this feature, the 7400C accurately measures the capacitance value, the dissipation factor and the equivalent series resistance of large value capacitors. The meter has a basic measurement accuracy of 0.05%. $9,100. QuadTech, (800) 253-1230.
Inductance Analyzer Suited
For High-Volume Applications
The PMA3260A Precision Magnetic Analyzer can be used in the manufacturing and test departments of high-volume magnetic component producers. It tests inductors and transformers at frequencies up to 10 MHz. A built-in insulation test capability (100, 200 and 500 VDC) is optional. Inductors may be tested for L, Z, RDC, C, Q, D, RAC and phase angle. Transformer tests include RDC for each winding, primary inductance and Q, turns ratio, interwinding capacitance and leakage inductance. The PMA3260A can be configured for automated testing via GPIB or incorporated in an ATE. $9,490. Wayne Kerr Electronics, (617) 938-8390.
RCL Meter Enables Fast
Testing of Passive Components
The PM 6306 RCL meter provides an immediate readout of dominant and secondary values as well as the equivalent-circuit diagram when a component is connected to the test posts. Test frequencies are continuously variable from 50 Hz to 1 MHz. The PM 6306 also features continuously variable AC/DC excitation voltages to help evaluate frequency- or voltage-dependent behavior of components under test. DC bias can be applied for testing electrolytic capacitors and semiconductor junctions. $4,235. Fluke. (800) 44-FLUKE.
Copyright 1996 Nelson Publishing Inc.
April 1996
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