The main failure modes of electronic components include, but are not limited to, open circuit, short circuit, burn, explosion, leakage, functional failure, drift of electrical parameters, and non-stable failure. For hardware engineers, the failure of electronic components is a very troublesome task. For example, a certain semiconductor device has a good appearance but is in fact half-failed or fully failed. It takes a lot of time to debug the hardware circuit, and sometimes it even crashes.
Hardware engineer debugs explosion scene
Therefore, it is an indispensable knowledge for hardware engineers to master the effective mechanism and characteristics of various types of electronic components. The following classification details the failure modes and mechanisms of various types of electronic components.
Resistor failure mode and mechanism failure mode: various failure phenomena and their manifestations. Failure mechanism: is the physical, chemical, thermodynamic, or other process that caused the failure.
1, the main failure mode and failure mechanism of the resistor
1) Open circuit: The main failure mechanism is the burning of the resistive film or the large-area shedding, the matrix fracture, the lead cap and the resistor body falling off.
2) The resistance drift is over-specified: the resistance film is defective or degraded, the substrate has movable sodium ions, and the protective coating is poor.
3) Lead fracture: defects in the welding process of resistors, contamination of solder joints, and mechanical stress damage of the leads.
4) Short circuit: migration of silver, corona discharge.
2. Failure mode accounts for the total proportion of failures
(1) Wire wound resistor
| Failure mode | Total proportion of failure |
| open circuit | 90% |
| Resistance drift | 2% |
| Lead break | 7% |
| other | 1% |
(2) Non-wire wound resistors
| Failure mode | Total proportion of failure |
| open circuit | 49% |
| Resistance drift | twenty two% |
| Lead break | 17% |
| other | 7% |
3, failure mechanism analysis
The failure mechanism of resistors is various, and various physical and chemical processes that occur under operating conditions or environmental conditions are the causes of resistor aging.
(1) Structure change of conductive material
The conductive film layer of the thin film resistor is generally obtained by a vapor deposition method, and an amorphous structure exists to some extent. From the thermodynamic point of view, there are crystallization trends in amorphous structures. Under working conditions or environmental conditions, the amorphous structure in the conductive film layer tends to crystallize at a certain speed, that is, the internal structure of the conductive material tends to be densified, which can often cause a decrease in the resistance value. The crystallization speed increases as the temperature increases.
In the preparation process, the resistance wire or the resistance film will bear the mechanical stress and cause the internal structure to be distorted. The smaller the wire diameter or the thinner the film layer, the more significant the stress effect will be. Heat treatment methods are generally used to eliminate internal stress, residual internal stress may be gradually eliminated during long-term use, and the resistance of the resistor may change accordingly.
The crystallization process and the internal stress removal process both slow down over time but cannot be terminated during the use of the resistor. It can be considered that these two processes take place at an approximately constant speed during the operation of the resistor. The resistance changes associated with them account for about one thousandth of the original resistance.
Electric load high-temperature aging: In any case, the electric load will accelerate the aging process of the resistor, and the effect of the electric load on accelerating the aging of the resistor is more pronounced than the accelerated aging of the elevated temperature because of the temperature of the contact portion of the resistor body and the lead cap. The rise exceeded the average temperature rise of the resistor body. Generally, the life is shortened by half every 10°C. If the overload causes the temperature of the resistor to rise by more than 50°C above the rated load, the life of the resistor is only 1/32 of the normal life. Accelerated life tests can be performed in less than four months to evaluate the stability of the resistors over a period of 10 years.
DC load - Electrolysis: Under the action of DC load, electrolysis causes aging of the resistor. The electrolysis takes place in the notch resistor groove, and the alkali metal ions contained in the resistor matrix displace in the electric field between the grooves to generate an ion current. In the presence of moisture, the electrolysis process is more severe. If the resistive film is a carbon film or a metal film, it is mainly electrolytically oxidized; if the resistive film is a metal oxide film, it is mainly electrolytically reduced. For high-resistance thin-film resistors, the consequences of electrolytic action can increase the resistance, and film damage can occur along one side of the spiral. Conducting a DC load test in a hot-humid environment can provide a comprehensive assessment of the antioxidant or anti-reduction properties of the resistor's substrate material and film, as well as the moisture resistance of the protective layer.
(2) Vulcanization
After one batch of on-site instruments were used in a chemical plant for one year, the instruments failed. The analysis found that the resistance of the thick film chip resistor used in the instrument became larger and even became an open circuit. When the failed resistor was placed under the microscope, black crystalline material appeared on the edge of the resistor electrode. Further analysis of the composition revealed that the black material was a silver sulfide crystal. The original resistance was corroded by sulfur from the air.
(3) Gas adsorption and desorption
The resistive film of the membrane resistor at the grain boundary, or the conductive particles and the binder part, may always adsorb a very small amount of gas, they constitute an intermediate layer between the crystal grains, and hinder the contact between the conductive particles, and thus Obviously affect the resistance.
Synthetic membrane resistors are made under normal pressure. When working under vacuum or low pressure, they will desorb part of the gas, improving the contact between the conductive particles and reducing the resistance. Similarly, when a pyrolytic carbon film resistor made in a vacuum operates directly under normal environmental conditions, part of the gas is adsorbed due to the increase in gas pressure, increasing the resistance. If the unfinished semi-finished product is preset at an appropriate time under normal pressure, the resistance of the finished resistor will be improved.
Temperature and pressure are the main environmental factors that affect gas adsorption and desorption. For physical adsorption, cooling can increase the amount of equilibrium adsorption, heating is the opposite. Gas adsorption and desorption occur on the surface of the resistor body. Therefore, the impact on the membrane resistor is more significant. Resistance changes up to 1% to 2%.
(4) Oxidation
Oxidation is a long-term contributing factor (different from adsorption). The oxidation process starts from the surface of the resistor and gradually deepens into the interior. In addition to noble metal and alloy thin film resistors, the resistors of other materials are affected by oxygen in the air. As a result of the oxidation, the resistance increases. The thinner the resistive film layer, the more pronounced is the oxidation effect.
The fundamental measure to prevent oxidation is sealing (inorganic materials such as metals, ceramics, and glass). Coating or potting with organic materials (plastics, resins, etc.) does not completely prevent the protective layer from moisture permeability or air permeability. Although it can delay the oxidation or adsorption of gases, it may also bring about new problems related to the organic protective layer. The aging factor.
(4) Effect of organic protective layer
During the formation of the organic protective layer, polycondensation volatiles or solvent vapors are released. The heat treatment process causes some of the volatiles to diffuse into the resistor, causing the resistance to rise. Although this process lasts for 1 to 2 years, it has a significant influence on the resistance time of about 2 to 8 months. To ensure the stability of the resistance of the finished product, it is appropriate to leave the product in the warehouse for a period of time and then leave the factory.
(5) Mechanical damage
The reliability of the resistor depends to a large extent on the mechanical properties of the resistor. Resistors, lead caps, and lead wires should all have sufficient mechanical strength, and matrix defects, lead cap damage, or lead breakage can all lead to resistor failure.
Electrolytic capacitor failure failure mode 1, depletion failure depletion failure (1)
The end of life of an electrolytic capacitor is usually judged based on the fact that the capacity drops below 80% of the nominal (initial value). Due to the early electrolyte filling of the aluminum electrolytic capacitor, the capacity of the aluminum electrolytic capacitor slowly decreased at the beginning of the work. As the working electrolyte continuously repairs the anodic oxide film damaged by the impurities during the load, the electrolyte gradually decreases. In the later period of use, since the electrolyte evaporates and decreases, it becomes difficult for the electrolyte with increased viscosity to fully contact the oxide film layer on the surface of the corroded rough aluminum foil, and thus the effective area of ​​the plate of the aluminum electrolytic capacitor is reduced. That is, the capacity of the anode and cathode aluminum foil is reduced, causing a sharp drop in the capacity. Therefore, it can be considered that the capacity reduction of the aluminum electrolytic capacitor is caused by the volatilization of the electrolyte. The main cause of the volatilization of the electrolyte is the high temperature environment or heat generation.
Depletion failure (2)
The reason why the aluminum electrolytic capacitor generates heat due to the application conditions is that the aluminum electrolytic capacitor operates in the rectification and filtering (including high frequency rectification filtering of the output of the switching power supply), and the ripple (or pulsation) current flowing through the aluminum of the power electric furnace is bypassed through the aluminum. Electrolytic capacitors generate losses in the ESR of aluminum electrolytic capacitors and turn them into heat to generate heat.
When the electrolyte of the aluminum electrolytic capacitor evaporates more and the solution becomes thicker, the resistivity increases as the viscosity increases, and the equivalent series resistance of the working electrolyte increases, resulting in a significant increase in the loss of the capacitor and an increase in the loss angle. For example, for an electrolytic capacitor with a working temperature of 105 degrees Celsius, when the maximum core temperature is higher than 125 degrees, the electrolyte viscosity suddenly increases and the ESR of the electrolyte increases by nearly ten times. Increased Equivalent Series Resistance generates more heat, causing greater volatilization of the electrolyte. In this way, the capacity of aluminum electrolytic capacitors drops sharply and even causes explosions.
Depletion failure (3)
Increased leakage currents often lead to failure of aluminum electrolytic capacitors.
Application of high voltage and high temperature can cause increased leakage current
2, pressure relief device action
In order to prevent the electrolyte in the aluminum electrolytic capacitor from the internal high-temperature boiling gas or the gas generated by the electrochemical process, the internal high pressure causes the aluminum electrolytic capacitor to explode. In order to eliminate the explosion of aluminum electrolytic capacitors, aluminum electrolytic capacitors with a diameter of 8 mm or more have set pressure
Release devices, which act to vent gas before the pressure inside the aluminum electrolytic capacitor reaches a dangerous pressure that has not caused the aluminum electrolytic capacitor to explode. With the action of the pressure release device of the aluminum electrolytic capacitor, the aluminum electrolytic capacitor is declared invalid.
Aluminum electrolytic capacitor pressure release device (middle cross)
Electrochemical process leads to action of pressure release device
The leakage current of aluminum electrolytic capacitors is an electrochemical process and has been discussed in detail in the foregoing, and will not be described again. The electrochemical process will generate gas, and the accumulation of these gases will cause the internal air pressure of the aluminum electrolytic capacitor to rise, eventually reaching the pressure relief device action to relieve pressure.
Excessive temperature causes the pressure release device to operate
Aluminum electrolytic capacitor temperature is too high may be high ambient temperature, such as aluminum electrolytic capacitor near the heating element or the entire electronic device out of the high temperature environment;
The second reason why the temperature of the aluminum electrolytic capacitor is too high is that the core temperature is too high. The fundamental reason for the high temperature of the aluminum electrolytic capacitor core pack is that the aluminum electrolytic capacitor flows excessively high ripple current. Excessive ripple current generates excessive loss in the ESR of the aluminum electrolytic capacitor and excessive heat generation causes the electrolyte to boil and generate a large amount of gas, which causes the pressure release device to act when the internal pressure of the aluminum electrolytic capacitor rises sharply.
3, instantaneous over-temperature
In general, the core-core temperature of an aluminum electrolytic capacitor is increased by a factor of two each time it is lowered by 10°C. This core is roughly in the center of the capacitor and is the hottest point inside the capacitor. However, when the capacitor heats up to its maximum allowable temperature, for most types of capacitors at 125°C, the electrolyte is driven by the capacitor core, causing the capacitor's ESR to increase by 10 times. Under this effect, transient over-temperature or over-current can cause permanent increase of ESR, resulting in capacitor failure. In the application of high temperature and large ripple current, special attention should be paid to the possibility of transient over-temperature occurrence, and additional attention should be paid to the cooling of aluminum electrolytic capacitors.
4, the instantaneous over-voltage generation
Power shock
During the power-on process, due to the filter inductance releasing energy storage into the filter capacitor, an excessive transient overvoltage of the filter capacitor is caused.
Power over voltage
Preventing over-voltage failure of capacitors
Capacitors are easily broken down in overvoltage conditions, and instantaneous high voltages in real applications are common.
For aluminum electrolytic capacitors with good over-voltage transient resistance, aluminum electrolytic capacitors from RIFA give instantaneous over-voltage values.
5, electrolyte dryness is the main reason for the failure of aluminum electrolytic capacitors
Causes of electrolyte drying up
The electrolyte evaporates naturally
Electrolyte consumption
The electrolyte evaporates naturally
The evaporation rate of electrolyte increases with temperature
The evaporation rate of the electrolyte is related to the sealing quality of the capacitor, and it must have good sealing performance under both high and low temperature conditions.
Electrolyte consumption
Electrochemical effects due to leakage currents consume electrolyte
Life of aluminum electrolytic capacitors decreases with increasing leakage current
Leakage current increases with temperature: Leakage current at 25°C is only less than one-tenth of the leakage current at 85°C Leakage current increases with increasing applied voltage: Aluminum electrolytic capacitors with a withstand voltage of 400V at rated voltage The leakage current is approximately 5 times the leakage current at 90% of rated voltage.
6, the electrolyte drying time is the life of aluminum electrolytic capacitors
Factors affecting the life of aluminum electrolytic capacitors (Temperature 1)
According to the different electrolytes of aluminum electrolytic capacitors, the maximum operating temperature of aluminum electrolytic capacitors can be divided into:
General purpose: 85°C
General high temperature use: 105°C
Special high temperature use: 125°C
Automotive engine compartment: 140~150°C
Factors Affecting the Life of Aluminum Electrolytic Capacitors (Nominal Life Hours)
According to the number of hours of life aluminum electrolytic capacitors can be divided into:
General purpose (normal temperature, within 3 years): 1000 hours
General purpose (room temperature, hope longer time): 2000 hours or more
Industrial Grade: Longer Life Hours
Factors Affecting the Life of Aluminum Electrolytic Capacitors (Temperature 2)
Every 10°C increase in temperature, the number of hours of service is halved
Factors Affecting Life of Aluminum Electrolytic Capacitors (Electrolyte)
Multi-and oligo-determined electrolytic capacitor life of electrolyte
Factors Affecting the Life of Aluminum Electrolytic Capacitors (Application Conditions)
High temperature shortens the life of aluminum electrolytic capacitors
High ripple current shortens the life of aluminum electrolytic capacitors
High Operating Voltage Reduces Life of Aluminum Electrolytic Capacitors
7. Parameters and Application Conditions Affecting Life of Aluminum Electrolytic Capacitors
Operating voltage and leakage current
Operating voltage and leakage current
The leakage current and applied voltage of a 450V/4700μF/85°C aluminum electrolytic capacitor produced by a company
Temperature and leakage current
The leakage current and the ambient temperature of a 450V/4700μF/85°C aluminum electrolytic capacitor produced by a company
Influence of Temperature, Voltage, and Ripple Current on Lifetime
Take an example of an aluminum electrolytic capacitor for electronic ballasts.
Aluminum electrolytic capacitors have different lifetimes under different voltage and temperature conditions
Derating life characteristics of an aluminum electrolytic capacitor for an electronic ballast
Over-voltage life characteristics of an aluminum electrolytic capacitor for an electronic ballast
Relationship between Lifetime, Temperature, and Ripple Current of Aluminum Electrolytic Capacitors
Inductance Failure Analysis Inductor Failure Mode: Inductance and Other Performance Overshoot, Open Circuit, Short Circuit Molded Wire Wound Inductor Failure Mechanism:
1. The magnetic stress produced by the magnetic core during processing is large and has not been released
2. There are impurities in the magnetic core or the core material itself is not uniform, affecting the magnetic field of the magnetic core, so that the permeability of the magnetic core has a deviation;
3. Sintering cracks due to sintering;
4. When the copper wire is connected to the copper strip by dip soldering, the coil part is splashed with tin liquid, melting the insulating layer of the magnet wire, causing a short circuit;
5. Slim copper wire, causing false welding and open circuit failure when connecting with copper tape
1, solder resistance
Low-frequency film sense after reflow solder flux increase "20%
As the reflow temperature exceeds the Curie temperature of the low-frequency sheet sensing material, demagnetization occurs. After the demagnetization of the sheet, the magnetic permeability of the sheet-like material recovered to the maximum, and the inductance increased. The general requirement of the control range is resistance to welding heat after the sheet, the sense of increase in magnitude is less than 20%.
The problem that may be caused by soldering resistance is that when small batches of manual soldering are performed, the circuit performance is all qualified (at this time, the overall sense of the sheet is not heated, and the inductance is small). However, when a large number of patches were placed, some circuit performance was found to be degraded. This may be due to the fact that after the reflow soldering, the amount of film inductance will increase, affecting the performance of the circuit. In places where the precision of the touch sensing is more stringent (such as the signal receiving and transmitting circuit), the concern about the solder resistance of the film should be increased.
Detection method: First, measure the sense value of the sheet sensation at room temperature, then immerse the sheet sensation in the molten solder pot for about 10 seconds and take it out. After the feeling of the sheet is thoroughly cooled, a new feeling amount value of the sheet feeling is measured. The percentage of increase in the amount of inductance is the magnitude of the solder resistance of the sheet.
2, weldability
Electroplating Introduction
When the reflow temperature is reached, metallic silver (Ag) reacts with metallic tin (Sn) to form a eutectic and thus cannot be directly plated on the silver tip of the sheet. Instead, nickel is first plated (about 2um) on the silver tip to form an insulating layer and then tin (4-8um).
Solderability testing
The tip of the sheet to be tested was cleaned with alcohol, and the sheet was immersed in a molten solder pot for about 4 seconds and taken out. Solderability is acceptable if the coverage of solder on the tip of the sheet reaches more than 90%. ,
Poor weldability
1) Oxidation of the tip: When the tablet is exposed to high temperature, humidity, chemicals, oxidizing gases (SO2, NO2, etc.), or the storage time is too long, the metal Sn on the tip of the tablet is oxidized to SnO2. Head darkens. Since SnO2 does not form eutectic with Sn, Ag, Cu, etc., the solderability of the sheet is reduced. Sensitive product shelf life: six months. If the tip of the sheet is contaminated, such as oily substances, solvents, etc., it can also cause a drop in solderability.
2) Nickel-plated layer is too thin to eat silver: If the nickel plating is too thin, the nickel layer cannot be isolated. During reflow, Sn on the tip of the sheet sensor first reacts with its own Ag, which affects Sn and solder paste on the pad to co-melt, causing the silver to be eaten, and the solderability of the sheet is degraded. .
Judgment method: Immerse the sheet into a molten solder pot for a few seconds and remove it. If pitting occurs at the end of the head and even the appearance of the porcelain body is exposed, it can be judged that the phenomenon of eating silver occurs.
3, bad welding
Internal stress
If the sheet sensation produces a large internal stress during the production process and no measures are taken to eliminate the stress, a good sensation in the reflow process will result in a standing sheet due to the influence of the internal stress, commonly known as the tombstone effect.
Judging whether there is a large internal stress in the feeling of the piece, a simpler method can be adopted:
Take a few hundred pieces of the feeling, into the general oven or low temperature furnace, heated to about 230 °C, heat, observe the situation inside the furnace. If you hear the sound of 噼噼 å å å å å å å , , , , , , , , , , , , , , , , 。 。 。.
Component deformation
If the sheet product has a bending deformation, there will be a magnification effect when welding.
Bad welding, cold welding
Normal welding
Improper pad design
a. Both ends of the pad should be symmetrically designed to avoid different sizes, otherwise the melting time and wetting force at both ends will be different.
b. The length of the welding is more than 0.3mm (that is, the coincident length of the metal tip and the land of the sheet)
c. The length of the pad space is as small as possible, generally not more than 0.5mm.
d. The width of the pad itself should not be too wide, and its reasonable width should not exceed 0.25mm compared with the MLCI width.
Bad patch
When patching, due to the unevenness of the pad or the sliding of the solder paste, the sheet feel is shifted by θ. Due to the wetting force generated when the pad melts, the above three conditions may be formed, in which the self-aligning is dominant, but sometimes the pull is more oblique, or the single pull is positive, the sheet is pulled to a pad It was even pulled up and slanted or erected (tombstone phenomenon). Current placement machines with θ-angle shift visual inspection can reduce the occurrence of such failures
Welding temperature
The soldering temperature profile of the reflow soldering machine must be set according to the requirements of the solder. It should try to ensure that the solder on both ends of the chip is melted at the same time so as to avoid the different time for the wetting force to be generated at both ends, leading to the shift of the chip sensation during the soldering process. If there is a bad weld, check if the temperature of the reflow machine is abnormal or the solder has changed.
The inductor is easily damaged in the case of rapid cooling, rapid heating or local heating. Therefore, special attention should be paid to the control of the welding temperature while welding, and the welding contact time should be as short as possible.
Reflow recommended temperature profile
Manual welding recommended temperature curve
4, open machine
Weld, poor welding contact
Remove the tablet sense test from the circuit board, whether the performance of the tablet is normal
Current burn through
If the sense of the selected plate is selected, the rated current of the beads is small, or a large inrush current in the circuit may cause the current to burn through, and the chip or bead may fail, causing the circuit to open. Remove the sheet sense test from the circuit board, the sheet is ineffective and sometimes burned. If there is a current burn-through, the number of failed products will be more, and the failed products in the same batch will generally reach more than a hundred percent.
Welding open
In the reflow soldering process, there is a rapid and rapid heat, which causes internal stress in the sheet-like sensation, resulting in a very small number of defects in the sheet-like sensation with an open-circuit hazard inside, and causing a feeling of openness. Remove the tablet sense test from the circuit board, and the sense of the panel is invalid. If there is an open solder joint, the number of failed products is generally less, and the number of failed products in the same batch is generally less than 1,000.
5, the damage of the magnet
Magnet strength
Insufficient sheet-sintering or other reasons cause insufficient strength and brittleness of the porcelain body. When the patch is applied, or the product is damaged by external force, the porcelain body is damaged.
Adhesion
If the film has a poor adhesion to the end silver layer, during reflow, the sheet feels hot and cold, the stress due to thermal expansion and contraction, and the porcelain body is affected by external forces, which may cause separation of the sheet-feeling tip and the porcelain body. Fall off; or the pad is too large. When reflowing, the wetting force generated when the solder melts and reacts at the tip is greater than the tip adhesion, causing damage to the tip.
The sheet feels burned or burned, or microcracks are generated inside during the manufacturing process. When the reflow solder is quenched and hot, the internal part of the sheet will be stressed, crystal cracks will occur, or micro cracks will expand, causing damage to the porcelain body.
Semiconductor device failure analysis
Failure analysis of semiconductor devices is to determine the failure modes of devices by performing various tests and physical, chemical, and metallographic tests on failed devices, analyzing the physical and chemical processes (failure mechanisms) that cause device failure, and finding the cause of device failure. , formulate corrective and improvement measures. Enhancing the failure analysis of semiconductor devices and improving its inherent reliability and use reliability are the most active and fundamental methods for improving the quality of electronic products, and have a very important role in improving the reliability of the entire machine.
The failures associated with the use of semiconductor devices are very prominent and account for the vast majority of all failed devices. Compared with domestic devices, the proportion of device failure due to inherent defects in the devices is significantly lower, indicating that the imported devices have better process control and higher inherent reliability.
1, use-related failure
The main reasons for invalidation related to use are:
Electrical stress damage, electrostatic damage, improper device selection, improper use of circuit design, mechanical overstress, and operational errors.
1 Electrical stress damage. The burn-out failure caused by over-electrical stress accounts for most of the devices that fail during use. It occurs in various stages such as device testing, screening, installation, debugging, and operation. The specific reasons are various, and common causes are bridging shorts caused by unwanted substances. Electric surge generated by the ground wire and power system, leakage of the soldering iron, and inductive surge caused by improper grounding of the instrument or test bench. According to the type of electrical stress, there is a continuous high-current type electrical stress formed after the metal bridges the short circuit, an instantaneous high-current type electrical stress generated by the coil recoil electromotive force, and a high-voltage small-current electrical stress caused by leakage, induction, etc.; The damage mechanism distinguishes between PN junctions and metallization burnout failures directly caused by external overstresses, as well as PN junctions triggered by external overstresses that cause CMOS circuits to latch off and cause burnout failure due to increased supply current.
2 electrostatic damage. Strictly speaking, the electrostatic damage of the device also belongs to the damage of electrical stress, but due to the special nature of the electrostatic-type over-voltage stress and the extensive use of electrostatic sensitive devices, this problem is becoming increasingly prominent. Electrostatic over-stress is characterized by high voltage (several hundred volts to tens of thousands of volts), low energy, and large instantaneous currents, but very short duration. Compared with general overstress, electrostatic damage often occurs in the non-power-on process of device transportation, transmission, installation, etc. It is unknowing to the damage process of the device and has a great harm. From the point of view of failure modes after electrostatic damage to the device, there are not only high-voltage and small-current failure modes such as PN junction degradation breakdown and surface breakdown, but also large current failure modes such as metallization and polysilicon burning.
3 improper device selection. Improper device selection is also one of the causes of failure caused by frequent use problems. The main reason is that designers do not understand the device parameters and performance comprehensively and are not well thought out. The selected devices cannot meet the designed circuit requirements in some aspects.
4 operation mistakes. Operational error is also one of the reasons for the frequent failure of the device, such as the failure of the device due to the polarity reversed.
2. Failure caused by inherent defects of the device
The failure causes associated with the inherent defects of the device include: surface problems, metallization problems, bond wire bonding problems, chip bonding problems, packaging problems, and defects in the body. Among these reasons, the major problems affecting device reliability are surface problems, bonding problems, and failures caused by stick-sheet problems. They are all batch-like and often occur repeatedly.
(1) Surface problems
From a reliability point of view, the most significant influence on the device is the mobile positive ion charge in the silicon dioxide layer, which will cause the breakdown voltage of the device to decrease, the leakage current to increase, and the device performance as the power-on time increases. Gradually deteriorated. Devices with this type of defect cannot be eliminated by conventional screening methods, and they are very detrimental to reliability. In addition, pinholes in the silicon dioxide layer on the surface of the chip have a greater influence on device reliability. Devices with such defects often have a very thin oxide layer at the beginning of the pinhole. The performance of the device is still normal. It can also pass tests such as aging and screening, but due to TDDB effect and electric surge after long-term use. The impact of the pinhole will pierce the short circuit, causing the device to fail.
(2) Metallization issues
The common metallization problems that cause device failures are stepped off aluminum, aluminum corrosion, metal film scratches, and the like. For primary integrated circuits, stepped aluminum and aluminum corrosion are more common: For secondary integrated circuits, internal metal film resistors are scratched during cleaning and wiping, causing open circuit failure is also one of the common failure modes.
(3) Pressure welding wire bonding problems
Common failures caused by bond wire bonding problems are the following types.
(1) The contaminated corrosion at the end of the welding wire or the pressure welding spot causes the pressure welding spot to fall off or the corrosion to open.
2 The gold layer under the external pressure solder joint is not firmly adhered to or gold and aluminum alloy occurs, causing the pressure solder joint to fall off.
3 over-pressure welding pressure welding point, so that the pressure wire neck disconnect caused by open circuit failure.
4 The arc of the pressure welding wire is not enough, and the angle with the chip surface is too small, and it easily collides with the silicon edge or the metallized aluminum wire under the bonding wire, causing device failure.
(4) Chip Bonding Problems
The most common are open circuits caused by too little solder on the die, solder oxidation, and low sintering temperatures. The poor bonding of the chip and the blackening of the solder cause the chip to lift up and separate from the base after being subjected to mechanical stress during "magnetic forming", resulting in open circuit failure.
(5) Packaging problems
Failures caused by packaging problems are the following types. 1 The package is not good, the gas leakage from the shell and the shell, so that water vapor or corrosive substances enter the interior of the shell, causing pressure welding wire and metalized corrosion. 2 There is a defect in the tube shell, which makes the tube leg open and short circuit failure.
3 The internal coating cracks and breaks the bonding aluminum wire, causing the device to open or instantaneous open circuit failure. This failure often occurs when the device is subjected to high and low temperature tests.
(6) In vivo defects
The presence of defects in the semiconductor device body can also cause the device's junction characteristics to deteriorate and fail, but this type of failure is not common, but often occurs in the body defects caused by the device's secondary breakdown tolerance and latch-up threshold voltage is reduced and burned .
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