HTOL testing core objectives:
As the core project (B1 item) of AEC-Q100 Standard Group B (Accelerated Lifecycle Simulation Testing), HTOL testing aims to evaluate the reliability of chips under long-term high-temperature operation, mainly achieving the following goals:
1. Simulate long-term service state: Utilize high-temperature accelerated aging effect to verify the functional stability of the chip within the expected life of the vehicle specification level (10-15 years).
2. Stimulate potential defects: Promote the early emergence of potential defects related to manufacturing processes (such as metal interconnect weaknesses, oxide layer defects) and design (such as inadequate thermal management).
3. Meet the zero failure standard: Ensure that the chip can maintain functional integrity and reliability in harsh application environments, such as high-temperature engine compartments.
Testing method:
HTOL testing strictly follows the JEDEC JESD22-A108 standard, with the following key implementation elements:
1. Test conditions:
Temperature and duration (set according to device level):
Grade 0: 150 ℃, 1000 hours (equivalent to approximately 10 years @ 150 ℃ activation energy 0.7eV)
Grade 1: 125 ℃, 1000 hours (equivalent to about 10 years @ 125 ℃ activation energy 0.7eV)
Grade 2: 105 ℃, 1000 hours (equivalent to approximately 5 years @ 105 ℃ activation energy 0.7eV)
Voltage stress: Apply the maximum operating voltage (usually 1.1 times the rated voltage, allowing for higher voltages to accelerate the aging effect in conjunction with temperature, but not exceeding the absolute maximum rated voltage).
Working state: The chip remains powered on and operates in typical load mode throughout the entire testing process.
2. Sample requirements:
Quantity: A total of 231 chips, from 3 non continuous production batches (77 chips per batch).
Preprocessing: For chips containing Flash memory, it is necessary to conduct 10K erase durability tests in advance and write checkerboard test data in Flash.
3. Common equipment:
DL601/602: Suitable for low-power microcontrollers (MCUs).
MCC LC2: Suitable for high-power system on chip (SoC) with independent temperature control capability.
4. Apply stress content:
For chips containing Flash, continuous Flash read operations are required during the HTOL process (simulating actual application scenarios).
Perform a scan chain (SCAN) test to verify the functionality of digital logic.
Run memory built-in self-test (MBIST) to detect RAM defects.
Apply corresponding workloads to each simulated functional module.
Typical Failure Mechanism Analysis:
1. Electromigration:
Principle: High current density drives directional migration of atoms in metal interconnects (such as Cu/Al), resulting in the formation of voids (open circuits) or whiskers (short circuits).
Typical manifestation: The resistance of the power network increases, causing the supply voltage drop (IR Drop) to exceed the standard.
2. Gate Oxide Degradation:
TDDB (dielectric breakdown over time): Defects accumulate in the gate oxide layer under high temperature and high pressure stress, ultimately leading to insulation layer breakdown (such as causing CMOS logic function failure).
HCI (Hot Carrier Injection): Strong electric fields allow channel carriers to gain high energy and inject it into the gate oxide layer, causing device threshold voltage drift or transconductance degradation.
3. Interconnection/packaging failure:
Solder joint creep fatigue: Lead free solder materials such as SnAgCu undergo creep at high temperatures, leading to fatigue cracks in BGA solder balls or bonding points until fracture.
Bond wire detachment: The Au/Al bonding interface experiences delamination or detachment under temperature cycling stress due to a mismatch in coefficient of thermal expansion (CTE).
4. Device parameter drift:
Increased leakage current: PN junction degradation or contaminated ion migration leads to an increase in static power consumption.
Decreased operating frequency: The driving capability of the transistor is weakened due to the negative bias temperature instability (NBTI) effect.
The key role of HAST testing
HAST (High Acceleration Stress Test) achieves a 10 fold acceleration effect compared to traditional temperature and humidity testing through the superposition of three stresses: temperature, humidity, and pressure. It specifically exposes the following failure modes that HTOL cannot cover:
1. Moisture penetration: Water vapor invades the plastic packaging, causing internal corrosion (such as rusting of bonding wires)
2. Ion migration: Wet environment accelerates metal ion diffusion, causing short circuits
3. Layered failure: Material interface delamination and peeling under high temperature and high humidity
According to the AEC-Q100 standard, all non sealed automotive chips must pass the HAST test (uHAST/bHAST), which together with HTOL forms the certification core item (Group B+Group G).
The independently developed HAST high acceleration life test chamber for intercooled low-temperature is designed specifically for HTOL to meet the full requirements of vehicle grade reliability verification. Compared to traditional high-temperature and high humidity testing, HAST increases the pressure inside the container, enabling temperature and humidity control under conditions exceeding 100 ℃. This can accelerate the aging effects of temperature and humidity (such as migration, corrosion, insulation degradation, material aging, etc.), greatly shorten the reliability evaluation testing cycle, and save time and cost. HAST high accelerated aging testing has become a standard in certain industries, especially in products such as PCBs, semiconductors, solar energy, display panels, etc., as a fast and effective alternative to standard high-temperature and high humidity testing.
Mainly used to evaluate the reliability of non airtight packaged IC devices, metal materials, etc. in humid environments. This experiment examines the effects of high temperature and time on the device under long-term storage conditions of the chip. This device is suitable for HAST testing requirements during the validation testing phase of mass-produced chips, and is only applicable to non sealed packaging (plastic packaging), testing with bias (bHAST), and testing without bias (uHAST).

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