Challenge #1: Inaccurate measurements
Measuring sub-milliohm resistors accurately is not easy because of the small resistance and parasitic effects. Parasitic effects such as lead inductance and resistance, as well as the temperature coefficient of the resistor, affect the accuracy of measurements. Commonly used benchtop meters typically have a limited measurement range and are unsuitable for measuring sub-milliohm resistors.
Solution: Use specialized measurement equipment such as four-wire resistance measurement, which eliminates the effect of leads by using two separate pairs of leads for measurement and compensation. Also, temperature control during measurement can help to minimize the effects of temperature changes.
Challenge #2: High thermal dissipation
Sub-milliohm resistors generate a lot of heat due to their low resistance, which can result in thermal stress and degradation over time. Additionally, high thermal dissipation can affect adjacent components and lead to errors in measurements.
Solution: Use resistors with high power dissipation, and ensure proper thermal management, such as using heat sinks or thermal vias. Also, make sure that the surrounding components are tolerant of the heat generated by the resistor.
Challenge #3: Assembly and handling
Sub-milliohm resistors are tiny, and the slightest damage during assembly or handling can affect their performance. Additionally, they are often mounted using automated assembly machines, which can cause mechanical stress and damage.
Solution: Use automated assembly machines that are designed for handling small components, and consider using protective packaging material such as tape-and-reel or matrix trays. Also, use proper static protection measures to avoid damaging the resistor due to electrostatic discharge.
Challenge #4: Low reliability
Sub-milliohm resistors must meet high reliability standards because they are used in critical applications, such as medical devices and automotive. However, ensuring long-term reliability is challenging because of the high thermal and mechanical stresses that the resistor experiences during use.
Solution: Use high-quality, reliable sub-milliohm resistors from reputable manufacturers. Conduct extensive testing and validation to ensure that the resistor meets the required standards for the specific application's operating conditions. Additionally, consider using redundancy or backup solutions to ensure that the system continues to operate in case of component failure.
In conclusion, although sub-milliohm SMD chip resistors present numerous challenges, they are essential components in modern electronics. Designers and engineers must consider the challenges and solutions discussed in this blog to ensure that they use these resistors effectively, reliably, and accurately in their designs. With proper attention to these challenges, designers can leverage the unique characteristics of sub-milliohm resistors to create robust, efficient, and reliable electronic systems.