Part 1
Mechanism of accelerated aging of automotive chips under high temperature environment
Chip aging is a complex phenomenon involving multiple physical and chemical processes. At the microscopic level, key factors include electromigration, thermal stress, and dielectric breakdown.
● Chip aging primarily stems from the gradual degradation of material properties during operation. This degradation includes, but is not limited to:
◎ Electromigration: High-temperature environments accelerate electron migration in metal interconnects, causing voids or metal build-up in the circuit, which can lead to open circuits or short circuits.
◎ Thermal expansion mismatch: Different materials (such as silicon, copper, solder joints, etc.) within the chip package have different coefficients of thermal expansion. Under repeated exposure to high temperatures, mechanical stress will be generated, leading to solder joint breakage or cracking of the package layer.
◎ Dielectric breakdown (TDDB): High temperatures accelerate the degradation of the dielectric layer, making it more susceptible to electrical breakdown and leading to chip failure.
◎ Intermetallic compound embrittlement: The intermetallic compound layer in the solder joint gradually thickens and becomes brittle under high temperature conditions, thereby reducing the reliability of the package.
In hot climates, ambient temperatures rise significantly. According to the Arrhenius equation, the degradation rate of materials is exponentially related to temperature. For automotive chips, the high-temperature environment accelerates various physicochemical processes within the chip.
Taking electromigration as an example, high temperatures increase the thermal energy of metal atoms, making them more susceptible to migration under the influence of an electric field, thus accelerating the occurrence of faults caused by electromigration. In automotive chips that are exposed to high temperatures for extended periods, electromigration problems that might otherwise take a long time to occur can happen prematurely due to the high temperatures, significantly shortening the chip's lifespan.
Hot climates not only present high temperatures but also frequent temperature fluctuations. These temperature fluctuations exacerbate thermal stress problems.
When a chip rapidly switches between different temperatures, the inconsistent thermal expansion and contraction of different materials can generate greater mechanical stress. For example, the thermal expansion coefficients of the packaging material and the core of the chip differ. When the temperature fluctuates, the connection between the two will be subjected to repeated tensile and compressive stresses, which can easily lead to the weakening or even breakage of connection points such as solder joints, creating new potential failure modes.
The increased computing power resulting from intelligent driving has significantly improved the utilization rate of MCU components. In hot climates, the temperature of automotive chips rises due to the increased ambient temperature, and the high utilization rate further increases the heat generated by the chips.
Cars with autonomous driving capabilities may operate for extended periods, keeping their chips under sustained high workloads and causing them to overheat.
The synergistic effect of high temperature and high utilization accelerates the chip aging process. Compared to normal operating conditions, the aging rate of chips can increase several times over under hot climates and high utilization conditions.
● Simply put, under high temperature:
◎ The electromigration rate of the chip increases exponentially, and the failure time of the interconnect is greatly reduced.
◎ High-temperature-induced mechanical stress accumulates between different packaging materials, significantly increasing the risk of solder joint fracture.
◎ Advanced process chips (such as 5nm and 3nm) have thinner and finer interconnects, which significantly reduces their tolerance to heat and current, making them particularly vulnerable at high temperatures.
◎ Autonomous driving and AI functions further increase the chip's duty cycle (running time ratio), and continuous high-temperature operation significantly increases the aging rate.
Currently, the industry commonly uses the Arrhenius equation to predict the aging process of chips. However, the nonlinear dynamic interactions in complex environments such as high temperature, high humidity, and multiple vibrations pose challenges to the accuracy of these predictions. This not only affects the reliability assessment of chips but also increases safety hazards in actual designs.
Part 2
Solutions to chip aging
To cope with high-temperature environments, chip manufacturers can select more heat-resistant materials during the design phase. For example, for interconnect materials, they can research and develop new high-temperature stable metals or alloys with higher melting points and better anti-electromigration properties, enabling them to maintain structural stability at high temperatures for extended periods.
Regarding insulating dielectrics, materials with higher breakdown voltages and thermal stability are sought to reduce the risk of dielectric breakdown. Sufficient margins should be incorporated into chip design to accommodate potential performance changes at high temperatures. This includes appropriately adjusting the chip's electrical parameters and operating frequency. For example, appropriately reducing the chip's operating frequency can decrease current density, thereby reducing the risk of electromigration.
At the same time, the redundancy design of the internal circuitry of the chip is increased. However, it should be noted that at advanced nodes (such as 5nm and 3nm), due to the extremely high circuit density, too much redundant circuitry may affect the overall performance. Therefore, a fine balance needs to be struck between redundancy and performance.
Improve the chip's thermal management structure to increase heat dissipation efficiency. More efficient heat dissipation materials, such as new heat sinks or thermal pastes with high thermal conductivity, can be used to quickly dissipate the heat generated by the chip.
At the same time, optimize the heat conduction path inside the chip, such as designing a reasonable layout of heat holes, so that heat can be distributed more evenly and quickly conducted to the heat dissipation parts.
● Chip manufacturers have begun to incorporate more margin in their designs to address the challenges of extreme environments:
◎ Material improvements: Develop more heat-resistant packaging materials and dielectric layers, such as using silicon carbide (SiC) instead of silicon-based materials.
◎ Enhanced interconnect resistance: By optimizing interconnect materials and geometry, the impact of electromigration on reliability is mitigated.
◎ Active cooling design: Incorporate thermal management modules into the system design, such as introducing miniature cooling devices or highly efficient thermally conductive materials.
By utilizing advanced monitoring technologies, such as integrating sensor networks into the chip, key parameters of the chip, such as temperature, current, and voltage, can be monitored in real time.
These monitoring data can be used to promptly detect changes in chip performance and potential failure risks. When excessively high chip temperature or abnormal current fluctuations are detected, it can be determined that the chip may be aging or have potential failure hazards.
Dynamically regulate the chip's operating status. One approach is to employ technology similar to that used by Chinese suppliers, which integrates artificial intelligence into chips. When chip performance degradation is detected, intelligent algorithms adjust parameters such as the chip's operating frequency and voltage to extend its lifespan. For example, if rising chip temperature is detected as causing performance degradation, the operating frequency can be appropriately reduced to decrease power consumption and heat generation, while maintaining the chip's basic functions.
Establish a comprehensive fault early warning and handling mechanism. When the monitoring system determines that a chip may be about to malfunction, it should promptly send a warning signal to the vehicle control system, allowing the vehicle to take appropriate measures, such as reducing speed, switching to a safe mode, or reminding the driver to go to a repair shop.
Meanwhile, during system design, the optimization of the fault transfer circuit is considered to ensure that when some chips fail, the function can be safely transferred to other systems as required, and the fault transfer circuit itself must also have high reliability and high temperature resistance.
● Active monitoring technology: By integrating sensors into the chip, key parameters such as temperature, current, and voltage are monitored in real time to predict chip degradation trends.
● Predictive maintenance: Based on AI algorithms, analyze chip operating data and proactively adjust frequency, voltage, or load distribution to slow down chip aging.
● Redundancy design: Introduce backup channels or circuits for critical components to quickly switch over in the event of a component failure, ensuring normal system operation.
● Task profile upgrade: Reassess the impact of autonomous driving and AI functions on chip lifespan and optimize the parameters of the task profile accordingly.
● Vehicle thermal management system: Develop more efficient in-vehicle temperature control solutions to mitigate the impact of the in-vehicle environment on electronic components, such as optimizing the synergistic efficiency of battery cooling and chip heat dissipation in electric vehicles.
As the issue of aging automotive chips becomes more prominent, industry standards need further improvement. For example, the next version of the ISO 26262 standard will incorporate predictive maintenance, emphasizing the monitoring and resilient management of silicon wafer data.
The entire industry should actively follow and promote the implementation of such standards, so that the design, manufacturing and application of automotive chips have clearer specifications and requirements, and promote the overall progress of automotive chip technology in dealing with the problem of aging in hot climates.
Automotive chips involve multiple links such as chip manufacturers, car manufacturers, and parts suppliers, requiring strengthened cooperation between upstream and downstream of the industry chain.
◎ Chip manufacturers and automakers should work closely together to develop suitable chip products based on the actual usage environment and needs of automobiles.
◎ Collaborate with material suppliers to develop new high-temperature resistant materials;
◎ Collaborate with software developers to optimize chip monitoring and control software algorithms.
By collaborating across the industry chain and integrating resources from all parties, we can jointly overcome the challenge of automotive chips aging in hot climates.
summary
Rising global temperatures and the increasing frequency of extreme weather events pose unprecedented challenges to the reliability of automotive chips. With the development of autonomous driving, electrification, and intelligent technologies, chips are playing an increasingly crucial role in in-vehicle systems. The phenomenon that hot climates accelerate chip aging indicates that existing technologies and standards still have significant shortcomings in extreme environments.
Chip design and manufacturing technologies need to strike a better balance between performance and reliability. From materials innovation to the application of predictive maintenance, and then to collaborative optimization at the vehicle level, the industry is exploring multi-layered solutions.
