FET Failure Analysis

Gideon Analytical Laboratories receivedthree Fairchild RFP40N10 power MOSFETs. A MOSFET is a specific type of metal oxide semiconductor field-effect transistor (MOSFET) designed to handle significant power levels.Compared to the otherpower semiconductor devices, for example, an insulated-gate bipolar transistor (IGBT) or athyristor, its main advantages are highswitchingspeed and good efficiency at low voltages. It shares with the IGBT an isolated gate that makes it easy to drive. They can be subject to low gain, sometimes to degree that the gate voltage needs to be higher than the voltage under control. The [Fairchild](http://Fairchild RFP40N10 power MOSFET) RFP40N10 power MOSFET is an N-Channel power MOSFET manufactured using MegaFET process, which uses featuresizes approaching those of LSI integrated circuits givesoptimum utilization of silicon. These MOSFETs were in TO-220AB packages. All of the terminals on theFairchild RFP40N10 power MOSFETs were shorted.

Gideon Analytical Laboratories received one IXYSRF DE375-501N21A MOSFET for electronic failure analysis. A MOSFET is a type of field-effect transistor (FET). It has an insulated gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. The IXYSRF DE375-601N21A MOSFET has high dv/dt, nanosecond switching, and 50 MHz maximum frequency. The IXYSRF DE375-601N21A MOSFET sent to Gideon Analytical Laboratories had a g-s short. The goal was to determine the cause of the failure.

Gideon Analytical Laboratories received 8Murata Ps DC-DC converters (pn 8600118) with suspected MOSFET failures. A DC-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. Power levels range from very low (small batteries) to very high (high-voltage power transmission). The DC to DC converters MOSFET is a type of field-effect transistor (FET). It has an insulated gate, whose voltage determines the conductivity of the device. This ability to change conductivity with the amount of applied voltage can be used for amplifying or switching electronic signals. Gideon Analytical Laboratories received 8 totalMurata Ps DC-DC converters (pn 8600118) in two separate batches. The first batch had a different mode of failure than the second batch. The goal was to determine the cause of the failures by focusing specifically on the MOSFETs.

Gideon Analytical Laboratories received two failed AUIRF7648M2 MOSFETs. These are rather new on the market and specifically designed for the automotive industry. Typically, when a MOSFET fails, all terminals short. It is the failure analyst’s job to discover how the MOSFET failed in the application by combining the schematics, clues found in the failure analysis, and clues found on the PCB to give a complete picture to help resolve the client’s problem.

Gideon Analytical Laboratories received one 2N3700 transistor for failure analysis. A new 2N3700 transistor was also received for comparison. A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor’s terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. The 2N3700 NPN bipolar transistor had a collector base maximum voltage of 140V, a collector-emitter maximum voltage of 80V, and an operating temperature range from -55°C to 175°C. The goal was to identify the reason for failure.

Gideon Analytical Laboratories received one linear microcircuit modular hybrid FK23009 for electronic failure analysis. A hybrid integrated circuit (HIC) is a miniaturized electronic circuit constructed of individual devices, such as semiconductors and passive components like resistors or inductors, and typically encapsulated in epoxy. The hybrid microcircuit is used in military and communications applications and is excellent for creating custom analog circuits, such as amplifiers and modulators. Thick film technology is often used as the interconnecting medium for hybrid integrated circuits. The modular hybrid FK23009 had no output on lead 1. The goal was to perform electronic failure analysis and discover the reason why it failed.

Gideon Analytical Labs received two failed RV4141AM ground fault interrupter controllers. The devices had far different impedance values than a new one did on several of the input pins. The RV4141A is a low power controller for AC outlet appliance leakage circuit interrupters. These devices detect hazardous current paths to ground such as an appliance falling into the water. The interrupter then opens the circuit line before a harmful or lethal shock occurs. Internally, the RV4141A has a diode bridge rectifier, Zener shunt regulator, op-amp, current reference, time delay circuit, latch and SCR driver. In addition, an external sense transformer, SCR, relay, two resistors and component selection, unique applications, resigned components, etc.

Gideon Analytical Laboratories received several dual N-channel SO-9 Vishay Siliconix MOSFETs. MOSFETs are transistors used for amplifying or switching electronic signals. The MOSFET is the most common transistor in both digital and analog circuits, used in many scenarios where voltage conversion is necessary. These dual N-channel SO-9 Vishay Siliconix Si4980DY MOSFETs were received for component evaluation and environmental testing in a variety of conditions to determine any noticeable flaws or anomalies with the package, die, or electrical parameters.

Gideon Analytical labs received one FDN337N-channel FET for failure analysis. The Drain-Source was reported shorted. Super SOTTM-3 N-Channel logic level enhancement mode power field effect transistors are produced using Fairchild’s high cell density DMOS technology. This very high-density process is specially tailored to minimize on-state resistance.

These devices are particularly suited for low voltage applications in notebook computers, portable phones, PCMCIA cards, and other battery powered circuits where fast switching and low in-line power loss are needed in a very small outline surface mount package.

Gideon Analytical Laboratories received two failed TI UCC27223PWP and three vintage devices for comparison. Two 14 pin Dip TI UCC27223PWP functional failures were sent from assemblies. The UCC27223 is a high-speed synchronous buck driver for thigh-efficiency lower-output voltage designs. Using PredictiveGate Drive (PGD) control technology, these drivers reduce diode conduction and reverse recovery losses in the synchronous rectifier MOSFET(s). The UCC27223 has an enable pin that controls the operation of both outputs. A logic latch, which keeps both outputs low until the first PWM input pulse comes in, is included. The RDS(on) of the SR pull-down sourcing device is minimized for higher frequency operations. This closed loop feedback system detects body-diode conduction and adjusts dead time delays to minimize the conduction time interval. This virtually eliminates body-diode conduction while adjusting for temperature, load-dependent delays, and for different MOSFETs. Precise gate timing at the nanosecond level reduces the reverse recovery time of the synchronous rectifier MOSFET body-diode, reducing reverse recovery losses seen in the main (high-side) MOSFET. The lower junction temperature in the low-side MOSFET increases product reliability. Since the power dissipation is minimized, a higher switching frequency can also be used, allowing for smaller component sizes.

Gideon Analytical Laboratories received three-failed Fairchild RFP40N10 power MOSFETs. All the terminals were shorted. A MOSFET is a voltage-controlled power device. If no positive voltage is applied between gate and source, the MOSFET will be non-conducting. If a positive voltage is applied to the gate an electrostatic field between it and the rest of the transistor will be produced. This positive gate voltage will push away the holes inside the p-type substrate and attracts the movable electrons in the n-type regions under the source and drain electrodes. This produces a layer just under the gate’s insulator, silicon dioxide, through which electrons migrate and move from source to drain. This region is known as the channel. The positive gate (doped polysilicon) voltage,therefore, inverts the p-type region and creates a channel in the top layer of material between the gate oxide and p-Si. Increasing the voltage will widen the channel and thus, increase the amount of current that can flow through the channel. This is called an enhancement mode MOSFET.

Gideon Analytical Laboratories received a failed IR FR22ON MOSFET within DC-DC converter. All the MOSFETs were shorted on all terminals. The MOSFETs were tested by lifting the gate and source wires from the circuitry. The Idss leakage for a good IR MOSFET is typically around less than 1 nano-amp. All the good MOSFETs tested were around .8 nano-amps, BVdss 220V, Vgsth 3.6, Igss <100nA. This IR FR220N has thermal damage. This typically overwhelms the junctions with current (heat) and the weakest hex cells are destroyed first. The black areas are produced by the anaerobic carbonization of the epoxy packaging.

Gideon Analytical Laboratories received two BSP 77 HITFET devices with resistive shorts. The HITFET is a highly integrated temperature protected FET low-side switch which provides protection from short circuits, overloads, voltage surges, open circuits, excessive temperature, and ESD. These low-side switches are versatile power transistors specially designed for automotive and industrial applications. Their built-in intelligence and protective features offer improved performance and reliability over discrete components.

The die is covered with a polyimide over glassivation on top of the trace lines. The polyimide is destroyed. The yellow arrow is melted glass at the failure site. There are two circuits off the gate wire: the EDS protection and the drive unit. The failures occurred in the region adjacent to the gate pad. There are several junctions where over current is observed. The temperature on this device had to get hot in order to melt the polyimide.