AEC-Q100- Failure Mechanism Based on Integrated Circuit Stress Test Certification

With the progress of automotive electronic technology, there are many complicated data management control systems in today's cars, and through many independent circuits, to transmit the required signals between each module, the system inside the car is like the "master-slave architecture" of the computer network, in the main control unit and each peripheral module, automotive electronic parts are divided into three categories. Including IC, discrete semiconductor, passive components three categories, in order to ensure that these automotive electronic components meet the highest standards of automotive anquan, the American Automotive Electronics Association (AEC, The Automotive Electronics Council is a set of standards [AEC-Q100] designed for active parts [microcontrollers and integrated circuits...] and [[AEC-Q200] designed for passive components, which specifies the product quality and reliability that must be achieved for passive parts. Aec-q100 is the vehicle reliability test standard formulated by the AEC organization, which is an important entry for 3C and IC manufacturers into the international auto factory module, and also an important technology to improve the reliability quality of Taiwan IC. In addition, the international auto factory has passed the anquan standard (ISO-26262). AEC-Q100 is the basic requirement to pass this standard.

List of automotive electronic parts required to pass AECQ-100:

Automotive disposable memory, Power Supply step-down regulator, Automotive photocoupler, three-axis accelerometer sensor, video jiema device, rectifier, ambient light sensor, non-volatile ferroelectric memory, power management IC, embedded flash memory, DC/DC regulator, Vehicle gauge network communication device, LCD driver IC, Single power Supply differential Amplifier, Capacitive proximity switch Off, high brightness LED driver, asynchronous switcher, 600V IC, GPS IC, ADAS Advanced Driver Assistance System Chip, GNSS Receiver, GNSS front-end amplifier... Let's wait.

AEC-Q100 Categories and Tests:

Description: AEC-Q100 specification 7 major categories a total of 41 tests

Group A- ACCELERATED ENVIRONMENT STRESS TESTS consists of 6 tests: PC, THB, HAST, AC, UHST, TH, TC, PTC, HTSL

Group B- ACCELERATED LIFETIME SIMULATION TESTS consists of three tests: HTOL, ELFR, and EDR

PACKAGE ASSEMBLY INTEGRITY TESTS consists of 6 tests: WBS, WBP, SD, PD, SBS, LI

Group D- DIE FABRICATION RELIABILITY Test consists of 5 TESTS: EM, TDDB, HCI, NBTI, SM

The group ELECTRICAL VERIFICATION TESTS consist of 11 tests, including TEST, FG, HBM/MM, CDM, LU, ED, CHAR, GL, EMC, SC and SER

Cluster F-Defect SCREENING TESTS: 11 tests, including: PAT, SBA

The CAVITY PACKAGE INTEGRITY TESTS consist of 8 tests, including: MS, VFV, CA, GFL, DROP, LT, DS, IWV

Short description of test items:

AC: Pressure cooker

CA: constant acceleration

CDM: electrostatic discharge charged device mode

CHAR: indicates the feature description

DROP: The package falls

DS: chip shear test

ED: Electrical distribution

EDR: non-failure-prone storage durability, data retention, working life

ELFR: Early life failure rate

EM: electromigration

EMC: Electromagnetic compatibility

FG: fault level

GFL: Coarse/fine air leakage test

GL: Gate leakage caused by thermoelectric effect

HBM: indicates the human mode of electrostatic discharge

HTSL: High temperature storage life

HTOL: High temperature working life

HCL: hot carrier injection effect

IWV: Internal hygroscopic test

LI: Pin integrity

LT: Cover plate torque test

LU: Latching effect

MM: indicates the mechanical mode of electrostatic discharge

MS: Mechanical shock

NBTI: rich bias temperature instability

PAT: Process average test

PC: Preprocessing

PD: physical size

PTC: power temperature cycle

SBA: Statistical yield analysis

SBS: tin ball shearing

SC: Short circuit feature

SD: weldability

SER: Soft error rate

SM: Stress migration

TC: temperature cycle

TDDB: Time through dielectric breakdown

TEST: Function parameters before and after stress test

TH: damp and heat without bias

THB, HAST: Temperature, humidity or high accelerated stress tests with applied bias

UHST: High acceleration stress test without bias

VFV: random vibration

WBS: welding wire cutting

WBP: welding wire tension

Temperature and humidity test conditions finishing:

THB(temperature and humidity with applied bias, according to JESD22 A101) : 85℃/85%R.H./1000h/bias

HAST(High Accelerated stress test according to JESD22 A110) : 130℃/85%R.H./96h/bias, 110℃/85%R.H./264h/bias

AC pressure cooker, according to JEDS22-A102:121 ℃/100%R.H./96h

UHST High acceleration stress test without bias, according to JEDS22-A118, equipment: HAST-S) : 110℃/85%R.H./264h

TH no bias damp heat, according to JEDS22-A101, equipment: THS) : 85℃/85%R.H./1000h

TC(temperature cycle, according to JEDS22-A104, equipment: TSK, TC) :

Level 0: -50℃←→150℃/2000cycles

Level 1: -50℃←→150℃/1000cycles

Level 2: -50℃←→150℃/500cycles

Level 3: -50℃←→125℃/500cycles

Level 4: -10℃←→105℃/500cycles

PTC(power temperature cycle, according to JEDS22-A105, equipment: TSK) :

Level 0: -40℃←→150℃/1000cycles

Level 1: -65℃←→125℃/1000cycles

Level 2 to 4: -65℃←→105℃/500cycles

HTSL(High temperature storage life, JEDS22-A103, device: OVEN) :

Plastic package parts: Grade 0:150 ℃/2000h

Grade 1:150 ℃/1000h

Grade 2 to 4:125 ℃/1000h or 150℃/5000h

Ceramic package parts: 200℃/72h

HTOL(High temperature working life, JEDS22-A108, equipment: OVEN) :

Grade 0:150 ℃/1000h

Class 1:150℃/408h or 125℃/1000h

Grade 2:125℃/408h or 105℃/1000h

Grade 3:105℃/408h or 85℃/1000h

Class 4:90℃/408h or 70℃/1000h

ELFR(Early Life failure Rate, AEC-Q100-008) : Devices that pass this stress test can be used for other stress tests, general data can be used, and tests before and after ELFR are performed under mild and high temperature conditions.

Concentrator Solar Cell

A concentrating solar cell is a combination of [Concentrator Photovoltaic]+[Fresnel Lenes]+[Sun Tracker]. Its solar energy conversion efficiency can reach 31% ~ 40.7%, although the conversion efficiency is high, but due to the long sunward time, it has been used in the space industry in the past, and now it can be used in the power generation industry with sunlight tracker, which is not suitable for general families. The main material of concentrating solar cells is gallium arsenide (GaAs), that is, the three five group (III-V) materials. General silicon crystal materials can only absorb the energy of 400 ~ 1,100nm wavelength in the solar spectrum, and the concentrator is different from silicon wafer solar technology, through the multi-junction compound semiconductor can absorb a wider range of solar spectrum energy, and the current development of three-junction InGaP/GaAs/Ge concentrator solar cells can greatly improve the conversion efficiency. The three-junction concentrating solar cell can absorb energy of 300 ~ 1900nm wavelength relative to its conversion efficiency can be greatly improved, and the heat resistance of concentrating solar cells is higher than that of general wafer-type solar cells.

Conduction Zone of Heat

Thermal conductivity

It is the thermal conductivity of a substance, passing from high temperature to low temperature within the same substance. Also known as: thermal conductivity, thermal conductivity, thermal conductivity, heat transfer coefficient, heat transfer, thermal conductivity, thermal conductivity, thermal conductivity, thermal conductivity.

Thermal conductivity formula

k = (Q/t) *L/(A*T) k: thermal conductivity, Q: heat, t: time, L: length, A: area, T: temperature difference in SI units, the unit of thermal conductivity is W/(m*K), in imperial units, is Btu · ft/(h · ft2 · °F)

Heat transfer coefficient

In thermodynamics, mechanical engineering and chemical engineering, the heat conductivity is used to calculate the heat conduction, mainly the heat conduction of convection or the phase transformation between fluid and solid, which is defined as the heat through the unit area per unit time under the unit temperature difference, called the heat conduction coefficient of the substance, if the thickness of the mass of L, the measurement value to be multiplied by L, The resulting value is the coefficient of thermal conductivity, usually denoted as k.

Unit conversion of heat conduction coefficient

1 (CAL) = 4.186 (j), 1 (CAL/s) = 4.186 (j/s) = 4.186 (W).

The impact of high temperature on electronic products:

The rise in temperature will cause the resistance value of the resistor to decrease, but also shorten the service life of the capacitor, in addition, the high temperature will cause the transformer, the performance of the related insulation materials to decrease, the temperature is too high will also cause the solder joint alloy structure on the PCB board to change: IMC thickens, solder joints become brittle, tin whisker increases, mechanical strength decreases, junction temperature increases, the current amplification ratio of transistor increases rapidly, resulting in collector current increases, junction temperature further increases, and finally component failure.

Explanation of proper terms:

Junction Temperature: The actual temperature of a semiconductor in an electronic device. In operation, it is usually higher than the Case Temperature of the package, and the temperature difference is equal to the heat flow multiplied by the thermal resistance. Free convection (natural convection) : Radiation (radiation) : Forced Air(gas cooling) : Forced Liquid (gas cooling) : Liquid Evaporation: Surface Surroundings Surroundings

Common simple considerations for thermal design:

1 Simple and reliable cooling methods such as heat conduction, natural convection and radiation should be used to reduce costs and failures.

2 Shorten the heat transfer path as much as possible, and increase the heat exchange area.

3 When installing components, the influence of radiation heat exchange of peripheral components should be fully considered, and the thermal sensitive devices should be kept away from the heat source or find a way to use the protective measures of the heat shield to isolate the components from the heat source.

4 There should be sufficient distance between the air inlet and the exhaust port to avoid hot air reflux.

5 The temperature difference between the incoming air and the outgoing air should be less than 14 ° C.

6 It should be noted that the direction of forced ventilation and natural ventilation should be consistent as far as possible.

7 Devices with large heat should be installed as close as possible to the surface that is easy to dissipate heat (such as the inner surface of the metal casing, metal base and metal bracket, etc.), and there is good contact heat conduction between the surface.

8 Power supply part of the high-power tube and rectifier bridge pile belong to the heating device, it is best to install directly on the housing to increase the heat dissipation area. In the layout of the printed board, more copper layers should be left on the board surface around the larger power transistor to improve the heat dissipation capacity of the bottom plate.

9 When using free convection, avoid using heat sinks that are too dense.

10 The thermal design should be considered to ensure that the current carrying capacity of the wire, the diameter of the selected wire must be suitable for the conduction of the current, without causing more than the allowable temperature rise and pressure drop.

11 If the heat distribution is uniform, the spacing of the components should be uniform to make the wind flow evenly through each heat source.

12 When using forced convection cooling (fans), place the temperature-sensitive components closest to the air intake.

13 The use of free convection cooling equipment to avoid arranging other parts above the high power consumption parts, the correct approach should be uneven horizontal arrangement.

14 If the heat distribution is not uniform, the components should be sparsely arranged in the area with large heat generation, and the component layout in the area with small heat generation should be slightly denser, or add a diversion bar, so that the wind energy can effectively flow to the key heating devices.

15 The structural design principle of the air inlet: on the one hand, try to minimize its resistance to the air flow, on the other hand, consider dust prevention, and comprehensively consider the impact of the two.

16 Power consumption components should be spaced as far apart as possible.

17 Avoid crowding temperature sensitive parts together or arranging them next to high power consuming parts or hot spots.

18 The use of free convection cooling equipment to avoid arranging other parts above the high power consumption parts, the correct practice should be uneven horizontal arrangement.

EC-105HTP,MTP,MTHP, High and low temperature constant temperature bath (1000L)

EC-35EXT, Superior constant temperature bath (306L)

IEC-60068-2 Combined Test of Condensation and Temperature and Humidity

Difference of IEC60068-2 damp heat test specifications

In the IEC60068-2 specification, there are a total of five kinds of humid heat tests, in addition to the common 85℃/85%R.H., 40℃/93%R.H. In addition to fixed-point high temperature and high humidity, there are two more special tests [IEC60068-2-30, IEC60068-2-38], these two are alternating wet and humid cycle and temperature and humidity combined cycle, so the test process will change temperature and humidity, and even multiple groups of program links and cycles, applied in IC semiconductors, parts, equipment, etc. To simulate the outdoor condensation phenomenon, evaluate the material's ability to prevent water and gas diffusion, and accelerate the product's tolerance to deterioration, the five specifications were organized into a comparison table of the differences in the wet and heat test specifications, and the test points were explained in detail for the wet and heat combined cycle test, and the test conditions and points of GJB in the wet and heat test were supplemented.

IEC60068-2-30 alternating humid heat cycle test

This test uses the test technique of maintaining humidity and temperature alternating to make moisture penetrate into the sample and cause condensation (condensation) on the surface of the product to be tested, so as to confirm the adaptability of the component, equipment or other products in use, transportation and storage under the combination of high humidity and temperature and humidity cyclic changes. This specification is also suitable for large test samples. If the equipment and the test process need to keep the power heating components for this test, the effect will be better than IEC60068-2-38, the high temperature used in this test has two (40 ° C, 55 ° C), the 40 ° C is to meet most of the world's high temperature environment, while 55 ° C meets all the world's high temperature environment, the test conditions are also divided into [cycle 1, cycle 2], In terms of severity, [Cycle 1] is higher than [Cycle 2].

Suitable for side products: components, equipment, various types of products to be tested

Test environment: the combination of high humidity and temperature cyclic changes produces condensation, and three kinds of environments can be tested [use, storage, transportation ([packaging is optional)]

Test stress: Breathing causes water vapor to invade

Whether power is available: Yes

Not suitable for: parts that are too light and too small

Test process and post-test inspection and observation: check the electrical changes after moisture [do not take out the intermediate inspection]

Test conditions: Humidity: 95%R.H.[Temperature change after high humidity maintenance](low temperature 25±3℃←→ high temperature 40℃ or 55℃)

Rising and cooling rate: heating (0.14℃/min), cooling (0.08 ~ 0.16℃/min)

Cycle 1: Where absorption and respiratory effects are important features, the test sample is more complex [humidity not less than 90%R.H.]

Cycle 2: In the case of less obvious absorption and respiratory effects, the test sample is simpler [humidity is not less than 80%R.H.]

IEC60068-2 damp heat test specification difference comparison table

For component type parts products, a combination test method is used to accelerate the confirmation of the test sample's resistance to degradation under high temperature, high humidity and low temperature conditions. This test method is different from the product defects caused by respiration [dew, moisture absorption] of IEC60068-2-30. The severity of this test is higher than that of other humid heat cycle tests, because there are more temperature changes and [respiration] during the test, the cycle temperature range is larger [from 55℃ to 65℃], and the temperature change rate of the temperature cycle is faster [temperature rise: 0.14 ° C /min becomes 0.38 ° C /min, 0.08 ° C /min becomes 1.16 ° C /min], in addition, different from the general humid heat cycle, the low temperature cycle condition of -10 ° C is added to accelerate the breathing rate and make the water condensed in the gap of the substitute freeze, which is the characteristic of this test specification. The test process allows the power test and the applied load power test, but it can not affect the test conditions (temperature and humidity fluctuation, rising and cooling rate) because of the heating of the side product after power. Due to the change of temperature and humidity during the test process, there can not be condensation water droplets on the top of the test chamber to the side product.

Suitable for side products: components, metal components sealing, lead end sealing

Test environment: combination of high temperature, high humidity and low temperature conditions

Test stress: accelerated breathing + frozen water

Whether it can be powered on: it can be powered on and external electric load (it can not affect the conditions of the test chamber because of power heating)

Not applicable: Can not replace moist heat and alternating humid heat, this test is used to produce defects different from respiration

Test process and post-test inspection and observation: check the electrical changes after moisture [check under high humidity conditions and take out after test]

Test conditions: damp heat cycle (25 please - 65 + 2 ℃ / 93 + / - 3% R.H.) please - low temperature cycle (25 please - 65 + 2 ℃ / 93 + 3% R.H. - - 10 + 2 ℃) X5cycle = 10 cycle

Rising and cooling rate: heating (0.38℃/min), cooling (1.16 ℃/min)

Heat and humidity cycle (25←→65±2℃/93±3%R.H.)

Low temperature cycle (25←→65±2℃/93±3%R.H. →-10±2℃)

GJB150-09 damp heat test

Instructions: The wet and heat test of GJB150-09 is to confirm the ability of equipment to withstand the influence of hot and humid atmosphere, suitable for equipment stored and used in hot and humid environments, equipment prone to high humidity, or equipment that may have potential problems related to heat and humidity. Hot and humid locations can occur throughout the year in the tropics, seasonally in mid-latitudes, and in equipment subjected to combined pressure, temperature and humidity changes, with special emphasis on 60 ° C /95%R.H. This high temperature and humidity does not occur in nature, nor does it simulate the dampness and heat effect after solar radiation, but it can find the parts of the equipment with potential problems, but it cannot reproduce the complex temperature and humidity environment, evaluate the long-term effect, and can not reproduce the humidity impact related to the low humidity environment.

Relevant equipment for condensation, wet freezing, wet heat combined cycle test: constant temperature and humidity test chamber

Maintenance of refrigeration compressor for constant temperature and humidity test chamber, cold and hot shock test chamber

Article summary: For environmental monitoring equipment, the only way to maintain long-term and stable use is to pay attention to maintenance in all aspects. Here, we will introduce the maintenance of the compressor, which is an important component of the constant temperature and humidity test chamber and the cold and hot shock test chamber

Detailed content:

Maintenance plan for refrigeration compressor:

As the core component of the refrigeration system in the constant temperature and humidity test chamber, the maintenance of the compressor is essential. Guangdong Hongzhan Technology Co., Ltd. introduces the daily maintenance steps and precautions for the compressor in the constant temperature and humidity test chamber and the cold and hot shock test chamber

1、 Carefully check the sound of the cylinders and moving parts at all levels to determine if their working condition is normal. If any abnormal sound is found, immediately stop the machine for inspection;

2、 Pay attention to whether the indicated values of pressure gauges at all levels, pressure gauges on gas storage tanks and coolers, and lubricating oil pressure gauges are within the specified range;

3、 Check if the temperature and flow rate of the cooling water are normal;

4、 Check the supply of lubricating oil and the lubrication system of the moving mechanism (some compressors are equipped with organic glass baffles on the side of the cross head guide rail of the machine body),

You can directly see the movement of the crosshead and the supply of lubricating oil; The cylinder and packing can be inspected for oil discharge using a one-way valve, which can check if the oil injector is inserted into the cylinder

Oil injection situation;

5、 Observe whether the oil level in the body oil tank and the lubricating oil in the oil injector are below the scale line. If they are low, they should be refilled in a timely manner (if using a dipstick, stop and check);

6、 Check the temperature of the intake and exhaust valve covers at the cross guide rail of the crankcase with your hand to see if it is normal;

7、 Pay attention to the temperature rise of the motor, bearing temperature, and whether the readings on the voltmeter and ammeter are normal. The current should not exceed the rated current of the motor. If it exceeds the rated current, the cause should be identified or the machine should be stopped for inspection;

8、 Regularly check whether there are any debris or conductive objects inside the motor, whether the coil is damaged, and whether there is friction between the stator and rotor, otherwise the motor will burn out after starting;

9、 If it is a water-cooled compressor and water cannot be immediately supplied after the water is cut off, it is necessary to avoid cylinder cracking due to uneven heating and cooling. After parking in winter, the cooling water should be drained to prevent freezing and cracking of the cylinder and other parts;

10、 Check whether the compressor vibrates and whether the foundation screws are loose or detached;

11、 Check whether the pressure regulator or load regulator, safety valve, etc. are sensitive;

12、 Pay attention to the hygiene of the compressor, its associated equipment, and the environment;

13、 Gas storage tanks, coolers, and oil-water separators should regularly release oil and water;

14、 The lubricating machine used should be filtered by sedimentation. Differentiate the use of compressor oil between winter and summer

Temperature and Humidity Terms

Dew Point temperature Td, in the air water vapor content unchanged, maintain a certain pressure, so that the air cooling to reach saturation temperature called dew point temperature, referred to as dew point, the unit is expressed in ° C or ℉. It's actually the temperature at which water vapor and water are in equilibrium. The difference between the actual temperature (t) and the dew point temperature (Td) indicates how far the air is saturated. When t>Td, it means that the air is not saturated, when t=Td, it is saturated, and when t<Td, it is supersaturated.

dew is the liquid water in the air that condenses on the ground. In the evening or at night, due to the radiation cooling of the ground or ground objects, the air layer close to the surface will also cool down. When the temperature drops below the dew point, that is, when the water vapor content in the air is susaturated, there will be condensation of water vapor on the surface of the ground or ground objects. If the dew point temperature is above 0 ° C at this time, tiny water droplets appear on the ground or ground objects, which are called dew.

frost refers to the white ice crystals formed on the ground or objects after the air close to the ground is cooled to the frost point (meaning the dew point is below 0) under the influence of radiation cooling on the ground.

fog refers to the condensation of water vapor suspended in the atmosphere near the Earth's surface, composed of small water droplets or ice crystals. When the temperature reaches the dew point temperature (or is close to the dew point), the water vapor in the air condenses to form fog.

snow is solid water in the form of snowflakes that falls to the ground from mixed clouds. Precipitation consisting of a large number of white opaque ice crystals (snow crystals) and their polymers (snow masses). Snow is the natural phenomenon of water condensing and falling in the air, or falling snow;

There is a limit to the amount of water vapor that can be contained in a unit volume of air under a certain pressure and a certain temperature. If the water vapor contained in the volume of air exceeds this limit, the water vapor will condense and produce precipitation, and the actual value of water vapor in the volume of air. In terms of absolute humidity. The more water vapor there is, the higher the absolute humidity of the air.

Relative Humidity refers to the percentage of water vapor pressure in the air and saturated water vapor pressure at the same temperature, or the ratio of the absolute humidity of wet air to the maximum absolute humidity that can be reached at the same temperature, and can also be expressed as the ratio of the partial pressure of water vapor in wet air to the saturation pressure of water at the same temperature.

Humidity: wet and dry bulb measurement

The dry and wet bulb thermometer is used to detect the [relative humidity] in the air, the dry bulb temperature is the temperature measured by the general temperature sensor, and the wet bulb temperature is tied on the temperature sensor with a wet cloth, and then soaked in a small cup of water, so that the water is wrapped in the whole sensor, because the relative humidity in the air must be less than or equal to 100% (the water vapor in the air is not saturated). Therefore, the moisture of the wet bulb will be evaporated, and the heat will be taken away during evaporation, resulting in a drop in the wet bulb temperature (the dry bulb temperature is the real air temperature), which means that the greater the difference in the readings of the dry and wet bulb thermometer, the more vigorous the evaporation of water, and the smaller the relative humidity in the air, as long as the temperature of the dry and wet bulb is measured, Then compare [relative humidity table] you can know the relative humidity of the environment at that time.

Temperature Cyclic Stress Screening (1)

Environmental Stress Screening (ESS)

Stress screening is the use of acceleration techniques and environmental stress under the design strength limit, such as: burn in, temperature cycling, random vibration, power cycle... By accelerating the stress, the potential defects in the product emerge [potential parts material defects, design defects, process defects, process defects], and eliminate electronic or mechanical residual stress, as well as eliminate stray capacitors between multi-layer circuit boards, the early death stage of the product in the bath curve is removed and repaired in advance, so that the product through moderate screening, Save the normal period and decline period of the bathtub curve to avoid the product in the process of use, the test of environmental stress sometimes lead to failure, resulting in unnecessary losses. Although the use of ESS stress screening will increase the cost and time, for improving the product delivery yield and reduce the number of repairs, there is a significant effect, but for the total cost will be reduced. In addition, customer trust will also be improved, generally for electronic parts of the stress screening methods are pre-burning, temperature cycle, high temperature, low temperature, PCB printed circuit board stress screening method is temperature cycle, for the electronic cost of the stress screening is: Power pre-burning, temperature cycling, random vibration, in addition to the stress screen itself is a process stage, rather than a test, screening is 100% of the product procedure.

Stress screening applicable product stage: R & D stage, mass production stage, before delivery (screening test can be carried out in components, devices, connectors and other products or the whole machine system, according to different requirements can have different screening stress)

Stress screening comparison:

a. Constant high temperature pre-burning (Burn in) stress screening, is the current electronic IT industry commonly used method to precipitate electronic components defects, but this method is not suitable for screening parts (PCB, IC, resistor, capacitor), According to statistics, the number of companies in the United States that use temperature cycling to screen parts is five times more than the number of companies that use constant high temperature prefiring to screen components.

B. GJB/DZ34 indicates the proportion of temperature cycle and random vibrating screen selection defects, temperature accounted for about 80%, vibration accounted for about 20% of the defects in various products.

c. The United States has conducted a survey of 42 enterprises, random vibration stress can screen out 15 to 25% of the defects, while the temperature cycle can screen out 75 to 85%, if the combination of the two can reach 90%.

d. The proportion of product defect types detected by temperature cycling: insufficient design margin: 5%, production and workmanship errors: 33%, defective parts: 62%

Description of fault induction of temperature cyclic stress screening:

The cause of product failure induced by temperature cycling is: when the temperature is cycled within the upper and lower extremal temperatures, the product produces alternating expansion and contraction, resulting in thermal stress and strain in the product. If there is a transient thermal ladder (temperature non-uniformity) within the product, or the thermal expansion coefficients of adjacent materials within the product do not match each other, these thermal stresses and strains will be more drastic. This stress and strain is greatest at the defect, and this cycle causes the defect to grow so large that it can eventually cause structural failure and generate electrical failure. For example, a cracked electroplated through-hole eventually cracks completely around it, causing an open circuit. Thermal cycling enables soldering and plating through holes on printed circuit boards... Temperature cyclic stress screening is especially suitable for electronic products with printed circuit board structure.

The fault mode triggered by the temperature cycle or the impact on the product is as follows:

a. The expansion of various microscopic cracks in the coating, material or wire

b. Loosen poorly bonded joints

c. Loosen improperly connected or riveted joints

d. Relax the pressed fittings with insufficient mechanical tension

e. Increase the contact resistance of poor quality solder joints or cause an open circuit

f. Particle, chemical pollution

g. Seal failure

h. Packaging issues, such as bonding of protective coatings

i. Short circuit or open circuit of the transformer and coil

j. The potentiometer is defective

k. Poor connection of welding and welding points

l. Cold welding contact

m. Multi-layer board due to improper handling of open circuit, short circuit

n. Short circuit of power transistor

o. Capacitor, transistor bad

p. Dual row integrated circuit failure

q. A box or cable that is nearly short-circuited due to damage or improper assembly

r. Breakage, breakage, scoring of material due to improper handling... Etc.

s. out-of-tolerance parts and materials

t. resistor ruptured due to lack of synthetic rubber buffer coating

u. The transistor hair is involved in the grounding of the metal strip

v. Mica insulation gasket rupture, resulting in short circuit transistor

w. Improper fixing of the metal plate of the regulating coil leads to irregular output

x. The bipolar vacuum tube is open internally at low temperature

y. Coil indirect short circuit

z. Ungrounded terminals

a1. Component parameter drift

a2. Components are improperly installed

a3. Misused components

a4. Seal failure

Introduction of stress parameters for temperature cyclic stress screening:

The stress parameters of temperature cyclic stress screening mainly include the following: high and low temperature extremum range, dwell time, temperature variability, cycle number

High and low temperature extremal range: the larger the range of high and low temperature extremal, the fewer cycles required, the lower the cost, but can not exceed the product can withstand the limit, do not cause new fault principle, the difference between the upper and lower limits of temperature change is not less than 88°C, the typical range of change is -54°C to 55°C.

Dwell time: In addition, the dwell time can not be too short, otherwise it is too late to make the product under test produce thermal expansion and contraction stress changes, as for the dwell time, the dwell time of different products is different, you can refer to the relevant specification requirements.

Number of cycles: As for the number of cycles of temperature cyclic stress screening, it is also determined by considering product characteristics, complexity, upper and lower limits of temperature and screening rate, and the screening number should not be exceeded, otherwise it will cause unnecessary harm to the product and cannot improve the screening rate. The number of temperature cycles ranges from 1 to 10 cycles [ordinary screening, primary screening] to 20 to 60 cycles [precision screening, secondary screening], for the removal of the most likely workmanship defects, about 6 to 10 cycles can be effectively removed, in addition to the effectiveness of the temperature cycle, Mainly depends on the temperature variation of the product surface, rather than the temperature variation inside the test box.

There are seven main influencing parameters of temperature cycle:

(1) Temperature Range

(2) Number of Cycles

(3) Temperature Rate of Chang

(4) Dwell Time

(5) Airflow Velocities

(6) Uniformity of Stress

(7) Function test or not (Product Operating Condition)

Temperature Cyclic Stress Screening (2)

Introduction of stress parameters for temperature cyclic stress screening:

The stress parameters of temperature cyclic stress screening mainly include the following: high and low temperature extremum range, dwell time, temperature variability, cycle number

High and low temperature extremal range: the larger the range of high and low temperature extremal, the fewer cycles required, the lower the cost, but can not exceed the product can withstand the limit, do not cause new fault principle, the difference between the upper and lower limits of temperature change is not less than 88°C, the typical range of change is -54°C to 55°C.

Dwell time: In addition, the dwell time can not be too short, otherwise it is too late to make the product under test produce thermal expansion and contraction stress changes, as for the dwell time, the dwell time of different products is different, you can refer to the relevant specification requirements.

Number of cycles: As for the number of cycles of temperature cyclic stress screening, it is also determined by considering product characteristics, complexity, upper and lower limits of temperature and screening rate, and the screening number should not be exceeded, otherwise it will cause unnecessary harm to the product and cannot improve the screening rate. The number of temperature cycles ranges from 1 to 10 cycles [ordinary screening, primary screening] to 20 to 60 cycles [precision screening, secondary screening], for the removal of the most likely workmanship defects, about 6 to 10 cycles can be effectively removed, in addition to the effectiveness of the temperature cycle, Mainly depends on the temperature variation of the product surface, rather than the temperature variation inside the test box.

There are seven main influencing parameters of temperature cycle:

(1) Temperature Range

(2) Number of Cycles

(3) Temperature Rate of Chang

(4) Dwell Time

(5) Airflow Velocities

(6) Uniformity of Stress

(7) Function test or not (Product Operating Condition)

Stress screening fatigue classification:

The general classification of Fatigue research can be divided into High-cycle Fatigue, Low-cycle Fatigue and Fatigue Crack Growth. In the aspect of low cycle Fatigue, it can be subdivided into Thermal Fatigue and Isothermal Fatigue.

Stress screening acronyms:

ESS: Environmental stress screening

FBT: Function board tester

ICA: Circuit analyzer

ICT: Circuit tester

LBS: load board short-circuit tester

MTBF: mean time between failures

Time of temperature cycles:

a.MIL-STD-2164(GJB 1302-90) : In the defect removal test, the number of temperature cycles is 10, 12 times, and in the trouble-free detection it is 10 ~ 20 times or 12 ~ 24 times. In order to remove the most likely workmanship defects, about 6 ~ 10 cycles are needed to effectively remove them. 1 ~ 10 cycles [general screening, primary screening], 20 ~ 60 cycles [precision screening, secondary screening].

B.od-hdbk-344 (GJB/DZ34) Initial screening equipment and unit level uses 10 to 20 loops (usually ≧10), component level uses 20 to 40 loops (usually ≧25).

Temperature variability:

a.MIL-STD-2164(GJB1032) clearly states: [Temperature change rate of temperature cycle 5℃/min]

B.od-hdbk-344 (GJB/DZ34) Component level 15 ° C /min, system 5 ° C /min

c. Temperature cyclic stress screening is generally not specified temperature variability, and its commonly used degree variation rate is usually 5°C/min