Gideon Analytical Laboratories received several Avago HCPL-2202 Optocouplers for failure analysis. These optocouplers have a totem pole output stages and optical receiver input stages with built-in Schmitt triggers to provide logic-compatible waveforms. They feature low input current (1.6mA to 1.8mA), Mbd typical signal rate, and guaranteed performance from -40 to 85 degrees Celsius. Some of their applications include isolation of high-speed logic systems, microprocessor system interfaces, and ground loop elimination. Our goal was to determine why the Avago HCPL-2202 Octocouplers had been failing.
Gideon Analytical Labs received four Fairchild 74OL6000 field failed Optocouplers along with three good (virgin green dot) devices in which a comparison could be done. The LSTTL input compatibility is provided by an input integrated circuit, with industry standard logic levels. This input ampliﬁer IC switches a temperature compensated current source driving a high speed 850 nm AlGaAs LED emitter. This integration scheme eliminates CTR degradation over time and temperature. The emitter is optically coupled to an integrated photodetector/high-gain, high-speed output ampliﬁer IC.
Gideon Analytical Laboratories received three failed Vishay MOC8101 isolating photocouplers for failure analysis. These photocouplers are components that transfer electrical signals between two isolated circuits by using light. Like the MOC8102, MOC8103, MOC8104, and MOC8105, the MOC8101 consists of a consisting of gallium arsenide infrared emitting diode optically coupled to a silicon planar phototransistor detector in a plastic plug-in DIP-6 package (http://www.vishay.com/docs/83660/moc8101.pdf) The MOC8101 were reported to have intermittent function, it was the goal of Gideon Analytical Laboratories to diagnose the cause of these failures.
Gideon Analytical Labs received one failed photocoupler, a Vishay IL 420, for failure analysis along with two virgins (unused) optocouplers for comparison.
The basic function of a Photo Coupler is to have electronic isolation, including potential isolation (as in the case of the transformer) in an electrical circuit. Devices of the Photo Coupler family include Photo Transistor, Photo Darlington Transistor, Photo Triac and OPIC. These devices have the characteristics of excellent isolation, high CTR, compact package, high-speed operation, low decay and unit control function not being influenced by field effects.
Gideon Analytical Labs received several Fairchild QTC H11N1s, a high-speed logic optocoupler, in 6-pin plastic DIPs. The devices were reported as some good, some intermittent and some not working in the application.
The main function of an opto-isolator is to block high voltages and voltage transients, so that a surge in one part of the system will not disrupt or destroy another part of the circuit. Opto-couplers allow a signal to be sent in digital (some analog) between circuits.
Gideon Analytical Laboratories received two failed photocouplers for failure analysis. These photocouplers feature a high isolation voltage, high-speed switching, and high collector to emitter voltage. They are used in many types of applications, including power supply, telephones, and fax machines. The optocoupler was electrically tested; there was a short on both input diodes. The goal was to determine the cause of this failure.
After curve trace tests were performed, both failed devices were immersed in a low surface tension dye penetrant This is a modified Mil-Std 1014.