Test Analysis & Equipment Utilization

Reliability Test Service

Environmental Test

Temperature, Humidity, Bias (THB) testing is a reliability test designed to accelerate metal corrosion, particularly that of the metallizations on the die surface of the device. Aside from temperature and humidity which are enough to promote corrosion of metals in the presence of contaminants, bias is applied to the device to provide the potential differences needed to trigger the corrosion process. The failure mechanism of THB is classified into galvanic, electrochemical, direct chemical corrosion, and ion migration.

THB testing employs the following stress conditions: 1000 hours at 85 deg C, 85% RH, with bias applied to the device. The bias applied is usually designed to simulate the bias conditions of the device in its real-life application, maximizing variations in the potential levels of the different metallization areas on the die as much as possible. During THB, intermediate readout at desired points of time is often used to test, which gives look-ahead reliability data as the THB test progresses.

THB Failure Mechanism
THB Failure Mechanism

Summary of THB conditions

Temperature (dry bulb °C) Relative Humidity1 (% R.H) Temperature (wet bulb, °C) Vapor Pressure (psia/kPa) Duration (hours)
85 ± 2 85 ± 5 81.0 7.12 (49.1) 1000

Reference Documents

  • JESD22-A101 “Steady State Temperature Humidity Bias Life Test”
THB chamber
THB chamber

Temperature cycling test is performed to determine the ability of a device to withstand 1) low and high temperature conditions 2) alternate exposures at high and low temperature extremes.
When a failure is introduced under repeated thermo-mechanical load cycles, it belongs to fatigue failure. TC is a test intended to accelerate this fatigue failure. A thermal shock is also a fatigue failure-acceleration test just like TC. Testing procedures include mounting samples to a TC chamber and exposing it repeatedly to high and low temperature extremes.
If the endpoint cycle completes, observe its appearance, lead, and seal at 10-20X magnifications and check marking status at maximum 3X magnifications.
If appearance, lead, or seal is damaged or marking is not clear, it is considered as failure.
Aside from visual inspection, electrical tests are performed according to product specifications to inspect TC-accelerated failures.

◎ Stress factors of thermal shock or temperature cycle
Difference low temperature and high temperature (ΔT)
Transition time between low temperature and high temperature
Dwell time at low temperature and high temperature

TC failure mechanism: die cracking, package cracking, neck/heel/wire breaks, bond lifting, etc.

Summary of TC conditions

TC-JEDEC
Test Condition Nominal Ts(min)(°C) Nominal Ts(max)(°C)
A -55 +85
B -55 +125
C -65 +150
G -40 +125
H -55 +150
I -40 +125
J -0 +100
K -0 +1215
L -55 +110
M -40 +150
N -40 +85
R -25 +125
T -40 +100
  • See reference documents for how to set the conditions
TS-Mil-Std-883
Condition Temperature (°C)
Low High
A -55 (-10/+0) +85 (-0,+15)
B -55 (-10/+0) +125 (-0,+15)
C -65 (-10/+0) +150 (-0/+15)
D -65 (-10/+0) +200 (-0/+15)
E -65 (-10/+0) +300 (-0/+15)
F -65 (-10/+0) +175 (-0/+15)

Reference Documents

  • Mil-Std-883 Method 1010 “Temperature Cycling”
  • JESD22-A104 “Temperature Cycling”
Two-chamber type &  air-circulation type equipment
Two-chamber type & air-circulation type equipment
SJR T/C
SJR T/C
The power and temperature cycling test is performed to determine the ability of a device to withstand alternate exposures at high and low temperature extremes and simultaneously the operating biases are periodically applied and removed.
It is intended to simulate worst case conditions encountered in application environments. The power and temperature cycling test is considered destructive and is only intended for device qualification.
This test method applies to semiconductor devices that are subjected to temperature excursions and required to power on and off for five minutes during all temperatures. Transition time between temperature extremes should be enough long so that all test samples may reach specified temperature (which is reached when bias is not applied).

Summary of PTC conditions

Test Condition Temperature Extremes
Degrees C.
Transition Time Between
Temp Extreme, Max.
Dwell Time at Each
Temp Extreme, Min.
A -40 (+0, -10) to +85 (+10,-0) 20 minutes 10 minutes
B -40 (+0, -10) to + 125 (+10, -0) 30 minutes 10 minutes
Summary of PTC conditions
Not required to synchronize cycles between temperature cycles and power cycles.

Reference Documents

  • JESD22-A105 “Power and Temperature Cycling”

Thermal shock test is performed to determine the resistance of a device to sudden changes in temperature. The test is repeated for a specified number of cycles, which start at ambient temperature. The sample is exposed to an extremely low temperature and within a short period of time, exposed to an extremely high temperature, before going back to a room temperature again. If the endpoint cycle completes, observe its appearance, lead, and seal at 10-20X magnifications and check marking status at maximum 3X magnifications. If appearance, lead, or seal is damaged or marking is not clear, it is considered as failure.

TS test-related failure mechanism includes die cracking, package cracking, neck/heel/wire breaks, bond lifting, etc. Newly-developed products are usually tested for 1000 numbers of cycles. Failure is determined by electrical tests or visual inspection at 200~500 X magnifications.

◎ Stress factors of thermal shock or temperature cycle
Difference low temperature and high temperature (ΔT)
Transition time between low temperature and high temperature
Dwell time at low temperature and high temperature

Summary of TS conditions

TS-JEDEC
Condition Temperature (°C)
Low High
A -40 (-10/+0) 85 (-0/+10)
B 0 (-10/+0) 100 (-0/+10)
C -55 (-10/+0) 125 (-0/+10)
D -65 (-10/+0) 150 (-0/+10)
  • Total Transfer Time < 20 seconds
  • Total Dwell Time Shall not be less than the time required samples to reach specified temperature
  • Specified Temp reached within dwell time
TS-Mil-Std-883
Condition Temperature (°C)
Low High
A 0 (-10/+2) 100 (-2/+10)
B -55 (-10/+0) 125 (-0/+10)
C -60 (-10/+0) 150 (-0/+10)
  • Total Transfer Time < 10 seconds
  • Total Dwell Time > 2 minutes
  • Specified Temp reached in < 5 minutes
  • Must be conducted for a minimum of 15 cycles

Reference Documents

  • Mil-Std-883 Method 1011 “Thermal Shock”
  • JESD22-A106 “Thermal Shock”
Thermal Shock Test Euipment
Thermal Shock Test Euipment
The autoclave (or pressure cooker) test is performed for the purpose of evaluating the moisture resistance of a device. It is used primarily to accelerate corrosion in the metal parts of the product, including the metallization areas on the surface of the die. Samples are tested for 168 hours at 121°C, 100% RH, and 2 atm. Surface-mount devices are preconditioned prior to autoclave testing. Preconditioning simulates the board mounting process of the customer. It normally consists of a bake to drive away the moisture inside the packages of the samples, a soak to drive a controlled amount of moisture into the package, and three cycles reflow. The samples are tested after preconditioning, failures from which are considered as preconditioning failures and not autoclave failures. Preconditioning failures should be taken seriously, since these imply that the samples are not robust enough to even withstand the board mounting process. Because of the extreme moisture condition during autoclave testing, moisture-related electrical leakage failures may be encountered after the test. Unless predefined to be so, such failures must not be considered as valid PCT failures. Only permanent failures, such as those arising from corrosion, are considered valid PCT failures.

Summary of PCT conditions

Temperature (dry bulb °C) Relative Humidity (% R.H) Duration (hours)
121 ± 2 100 96 (-0, +2)

Reference Documents

  • JESD22-A102 “Accelerated Moisture Resistance - Unbiased Autoclave”
TPCT Euipment
TPCT Euipment
HAST (Highly Accelerated Stress Test) was developed as a shorter alternative to Temperature Humidity Bias (THB) Testing. If THB testing takes 1000 hours to complete, HAST results are available within 96-100 hours. Because of this, the popularity of HAST has continuously increased in recent years. Like THB testing, HAST accelerates corrosion, particularly that of the die metal lines and thin film resistors. HAST requires preconditioning and is conducted with electrical bias at 130 deg C and 85% RH for 96-100 hours.
The samples for HAST stressing are loaded into HAST boards prior to loading into the HAST chamber. HAST boards are designed to withstand the severe test conditions of HAST (See Figure).
HAST is recommended for the qualification of any change that can potentially affect the corrosion resistance of the product. Thus, HAST certification is required changes in molding compound, die glassivation, metallization, thin film resistors, etc. as well as a new fab process, a new package, or a new fab/assembly site.
◎ Bias Condition Setting
Power dissipation must be minimized to ensure that moisture is always present at the die surface.
Alternate pins must be subjected to opposite bias (low voltage versus high voltage) as much as possible.
The operating voltage range for the device must also be maximized, as long as the power dissipation is kept under control.

Summary of HAST conditions

Temperature
(dry bulb °C)
Relative
Humidity (% R.H)
Temperature
(wet bulb, °C)
Vapor Pressure
(psia/kPa)
Duration
(hours)
A 130 ± 2 85 ± 5 124.7 33.3/230 96 (-0, +2)
B 110 ± 2 85 ± 5 105.2 17.7/122 264 (-0, +2)

Reference Documents

  • JESD22-A110 “Highly Accelerated Temperature and Humidity Stress Test (HAST)
HAST Chamber and Board
HAST Chamber and Board
The High-Temperature Storage (HTS) test is performed to determine the effect on devices of long-term storage at elevated temperatures. HTS is similar to Stabilization Bake (Mil-Std-883 Method 1008), except that HTS is done over a much longer period of time (1000 hours vs. 24 hours for Stab Bake at 150 °C). The purpose of HTS is to assess the long-term reliability of devices under high temperature conditions while that of Stabilization bake is merely to serve as part of a screening sequence or as a preconditioning treatment prior to the conduct of other tests. HTS consists of storing the sample at the specified ambient temperature for a specified amount of time. The devices must be allowed to reach the specified temperature before the duration starts counting. Measurements (External visual inspection and electrical test) must be conducted within 96 hours after the specified test conditions are removed. HTS is not a substitute for burn-in because it does not subject its samples to electrical stresses. Nonetheless, HTS is effective for the reliability testing of samples in terms of mechanisms accelerated by temperature only, e.g., oxidation, bond and lead finish intermetallic growths, etc. HTS may be conducted basically at 150 °C/1000 h and for various purposes by changing temperature and time conditions. Low Temperature Storage (LTS) is also performed for the same purpose as HTS but is different in that it is performed at low temperature conditions. Aside from storage tests, this test can be performed in association with data retention or other reliability tests as a single test sequence.

Summary of HTS conditions

HTS
Condition Temperature (°C)
A +125 (-0/+10)
B +150 (-0/+10)
C +175 (-0/+10)
D +200 (-0/+10)
E +250 (-0/+10)
F +300 (-0/+10)
G +85 (-0/+10)
LTS
Condition Temperature (°C)
A -40 (-10/+0)
B -55 (-10/+0)
C -65 (-10/+0)

Reference Documents

  • Mil Std 883, Method 1008 “Stabilization Bake”
  • JESD22-A103 “High Temperature Storage Life”
  • JESD22-A119 “Low Temperature Storage Life”
  • EIAJ ED-4701/200 test method 202 “Low Temperature Storage”
Image of test chambers and sample loading
Image of test chambers and sample loading
Different package types exhibit different sensitivity levels to moisture ingress and its effects. Through-hole and bulkier packages absorb moisture per volume at a slower rate than the thinner SMD packages. The problem with moisture absorption and retention inside the package is that the trapped moisture will vaporize and exert tremendous internal package stresses when the device is subjected to sudden, elevated temperature (Ex. Board mounting). Package cracking due to such moisture-induced stresses is known as popcorn cracking.
In general, surface-mount devices (SMD) are more prone to popcorn cracking because:
  • They are thinner and therefore have lower fracture strength.
  • They absorb and retain moisture more easily.
  • SMD board mounting also subjects the molding compound to the high temperature.
일정시간 대기에 노출된 device, 수분 흡수발생→Package 내부로 침투한 수분이 기화하면서, (약 1200배 이상 팽창)Popcorn 현상 발생
In recognition of the varying degrees of popcorn cracking tendency of various package types, IPC/JEDEC defined a standard classification of moisture sensitivity levels (MSL's). The MSL's are expressed in numbers, with the MSL number increasing with the vulnerability of the package to popcorn cracking. Thus, MSL1 correspond to packages that are immune to popcorn cracking regardless of exposure to moisture, while MSL5 and MSL6 devices are most prone to moisture-induced fracture.

Summary of MSL

Level FLOOR LIFE SOAK REQUIREMENTS
STANDARD
TIME CONDITION TIME (hours) CONDITION
1 Unlimited ≤30 °C / 85 % R.H 168 +5 / -0 85 °C / 85 % R.H
2 1 year ≤30 °C / 60 % R.H 168 +5 / -0 85 °C / 60 % R.H
2a 4 weeks ≤30 °C / 60 % R.H 696 +5 / -0 30 °C / 60 % R.H
3 168 hours ≤30 °C / 60 % R.H 192 +5 / -0 30 °C / 60 % R.H
4 72 hours ≤30 °C / 60 % R.H 96 +2 / -0 30 °C / 60 % R.H
5 48 hours ≤30 °C / 60 % R.H 72 +2 / -0 30 °C / 60 % R.H
5a 24 hours ≤30 °C / 60 % R.H 48 +2 / -0 30 °C / 60 % R.H
6 Time on Label ≤30 °C / 60 % R.H TOL 30°C / 60% R.H

Reference Documents

  • JSTD-020 “Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices”
Precondition comprehensively means a reliability testing step performed to determine the ability of a device to withstand the thermal stresses of the board mounting or board soldering process. In semiconductor reliability, precondition usually means surface-mount process of surface-mount devices. Though reliability of SMD packages should be tested, it is difficult to remove samples from the product (it is difficult to avoid physical damage). Therefore, reliability test samples are prepared by applying temperature profile generated during PCB reflow process to the package of a single product (See the below figure).
Moisture sensitivity level should be preliminarily determined before precondition is performed according to specified level.
In recognition of the varying degrees of popcorn cracking tendency of various package types, IPC/JEDEC defined a standard classification of moisture sensitivity levels (MSL's). The MSL's are expressed in numbers, with the MSL number increasing with the vulnerability of the package to popcorn cracking. Thus, MSL1 correspond to packages that are immune to popcorn cracking regardless of exposure to moisture, while MSL5 and MSL6 devices are most prone to moisture-induced fracture.
규정된 MSL로 Soak 수준 결정→Reflow 3 cycles→출하제품과 동일한 상태→Temperature Humidity Bias Test/Highly Accelerated Stress Test/Temperature Cycle/Autoclave/Unbiased - HAST
Precondition is performed prior to THB, HAST, TC, AC, and UHST.

Reference Documents

  • JESD22-A113 “Preconditioning of Plastic Surface Mount Devices Prior to Reliability Testing”
  • JSTD-020 “Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices”
Salt atmosphere test is an accelerated test that simulates the effects of seacoast atmosphere on products and packages. This test consists of spraying salt solution, forming salt atmosphere fog, and exposing devices for a specified period of time. Upon completion of the test, the device should be washed in D/I water for at least 5 minutes. And then evaluate pitting, blistering, flaking, corrosion, etc. at 10 to 20X magnifications.

Summary of Salt Atmosphere conditions

  • exposure of parts to salt fog
  • salt : sodium chloride meeting impurity level reqts.
  • salt concentration: 0.5 % - 3 % by wt. in DI/distilled water
  • salt fog temperature : 35 deg C minimum
  • exposure zone maintained between 32 - 38 deg C
  • pH : 6.5 - 7.2 at 35 deg C
Test Condition Duration (hours)
A 24
B 148
C 96
D 240

Reference Documents

  • Mil-Std-883 Method 1009 “Salt Atmosphere (corrosion)”
  • JESD22-A107 “Salt Atmosphere”
Test Apparatus
Test Apparatus
Highly Accelerated Life Test (HALT) is a completely different concept of test from conventional reliability tests. This test is performed at the product design step to find design weakness and reduce return rates by applying improved design to the product. This is not a concept of simulating field environment but accelerating weak point at low and high temperature conditions or random vibration to find weakness as fast as possible. This test consists of designer’s selecting critical parameters and monitoring characteristics according to sequence. If any failure appears, product margins are secured by finding failure points and improvements. Above all, test plans should be established by agreement between designer and investigator, accurate test (where target parameters can be corrected) be performed, and cause analysis be performed at the event of problems. Based upon the reliability technology and know-how accumulated for 25 years, QRT is performing tests optimized for the purpose of HALT.

Summary of HALT

  • Thermal Step Stress Test - cold
  • Thermal Step Stress Test - Hot
  • Rapid Thermal Transient Stress Test
  • Vibration Step Stress Test
  • Combined Environment Stress Test
Rapid Thermal Transitions

Reference Documents

  • Mil-Std883 Method 2005 “Vibration Fatigue”
  • JESD22-B103B “Vibration, Variable Frequency”
HALT 장비와 챔버와 실제 시험모습
HALT Chamber and Test JIG