During the use of electronic products, the temperature is constantly changing due to temperature variations between components and PCB boards, such as when the device is switched on, off, running and on standby. Some solder joints begin to suffer from stresses due to the mismatch in the coefficient of thermal expansion of the materials between the component and the PCB not being taken into account. Below are some of the common causes that can lead to cracked solder joints failing due to mismatched coefficients of thermal expansion between components and PCBs, as well as solutions.
What is solder joint cracking failure due to incompatible coefficients of thermal expansion of components and PCBs?
“Failure of solder joints due to inconsistent thermal expansion coefficients of components and PCBs” refers to a failure condition that may occur during the manufacturing and use of electronic equipment. In this case, the connection point between an electronic device (e.g., integrated circuit chip, resistor, capacitor, etc.) and a printed circuit board (PCB), i.e., the solder joint, may experience stress accumulation due to a mismatch in coefficients of thermal expansion between the component and the material of the PCB. This stress build-up may lead to small cracks in the solder joints, which may eventually lead to complete cracking of the solder joints, thus triggering the failure of the device.
What are the effects of solder joint cracking failure due to mismatch of thermal expansion coefficients of components and PCB boards:
1、Equipment failure: solder joints are important connections in electronic equipment. Poorly connected or cracked solder joints can lead to circuit interruptions or performance degradation, which can prevent the equipment from working properly, or even fail completely.
2、Performance degradation: If part of the solder joints are cracked but still connected, the resistance, capacitance, signal transmission and other properties of the circuit may be affected, resulting in a decline in the performance of the equipment, unstable operation or noise.
3、Reliability degradation: The reliability of the equipment is greatly threatened. Cracked solder joints may cause equipment to fail in a relatively short period of time, reducing product life and increasing the need for maintenance and replacement.
4、Increased maintenance and costs: Once a solder joint is cracked, the equipment needs to be repaired or the solder joint replaced, which can be costly in terms of labour and time. If the equipment is used in the field, repairs can be even more difficult and expensive.
5、Safety hazards: In certain applications, such as medical equipment, aerospace equipment, etc., cracked solder joints can lead to safety hazards or even life-threatening injuries.
6、Product recalls: If cracked solder joints seriously affect the performance and reliability of a product, the manufacturer may have to conduct a product recall, which can result in significant costs and brand loss.
Components and PCBs do not have the same coefficient of thermal expansion, resulting in the failure of cracked solder joints.
The following are some of the main causes of solder joint cracking failure due to inconsistencies in the coefficient of thermal expansion of components and PCBs:
1、Thermal expansion mismatch caused by material differences: Components and PCBs are usually made of different types of materials, which expand or contract at different rates when the temperature changes, i.e., they have different coefficients of thermal expansion. When the solder joints between the component and the PCB connect these materials, the mismatch in coefficients of thermal expansion can lead to stress during temperature changes. This stress can build up in the solder joint area and eventually lead to cracking of the solder joint.
2、Cyclic stresses caused by temperature changes: Electronic devices may experience different temperature changes during normal operation, such as switching on and off, temperature increases during operation and temperature decreases during hibernation. These cyclical temperature changes can lead to periodic stress on the solder joints between components and PCBs, which can increase the risk of solder joint cracking.
3、Mechanical vibration and shock: In addition to temperature changes, equipment may experience environmental effects such as mechanical vibration, shock and vibration during use. These external forces can apply mechanical stresses to the solder joint area, increasing the likelihood of cracked solder joints, especially if the difference in thermal expansion between the component and the PCB already exists.
The Solution
The following measures can be taken to address solder joint cracking failures due to inconsistencies in the coefficients of thermal expansion between components and PCBs:
1、Material Selection and Matching: In the early stages of product design and manufacturing, give preference to materials with similar coefficients of thermal expansion, especially in the area of solder joints between components and PCBs. This helps to reduce stresses caused by thermal expansion mismatches.
2、Design of elastic connections: In the design near the solder joints, consider the use of elastic connections, cushioning materials, or bending structures to absorb the stresses caused by differences in thermal expansion, thus reducing stress concentrations in the solder joint area.
3、Use of compensating components: Introduce specialised thermal expansion compensating components into the design, such as thermal expansion compensating sheets and elastic spacers, which can reduce the stress between the components and PCB to a certain extent.
4、Control of temperature changes: try to control the temperature of the environment in which the equipment is located in the magnitude of temperature changes, for example, by strengthening the heat dissipation design, temperature control systems and other means to reduce the temperature-induced thermal expansion differences.
5、Mechanical stability design: taking into account the impact of mechanical vibration and impact on the solder joint area, the design of a stable shell structure and fixtures to reduce the impact of external forces on the solder joints.
6、Reliability testing and simulation: During the product development process, simulation tests and reliability analysis are conducted to assess potential problems caused by thermal expansion and predict solder joint failures in order to optimise the design.
7、Manufacturing process improvement: In the production process, through the optimisation of the welding process, material treatment and other means to reduce the stress concentration between the components and PCB, to reduce the risk of solder joint cracking.