In high-end manufacturing fields such as power electronics, new energy, and aerospace, copper-clad ceramic substrates serve as core heat dissipation and load-bearing components. The quality of their connection with copper or aluminum heat sinks directly determines the thermal conductivity, mechanical stability, and lifespan of the devices. Traditional connection processes, primarily soldering and sintering, are widely used in the industry, but limitations imposed by material properties and process principles make it difficult to meet the stringent requirements of high-end devices for heat dissipation efficiency and reliability. Ultrasonic welding technology, with its core advantages of solid-state connection and low-temperature high efficiency, is gradually replacing traditional processes and becoming the preferred solution for connecting copper-clad ceramic substrates and heat sinks, propelling electronic packaging technology to new heights.
The core principle of ultrasonic welding is to achieve atomic-level metallurgical bonding between the copper layer of the copper-clad ceramic substrate and the heat sink through the synergistic effect of high-frequency mechanical vibration (typically 20-40kHz) and moderate pressure. During the welding process, high-frequency vibration causes intense friction at the connection interface, instantly breaking the surface oxide film and exposing the clean metal substrate; simultaneously, frictional heat raises the interface temperature to a plastic state below the material's melting point, promoting copper atoms to diffuse and penetrate in the solid state, forming a strong metallurgical joint. Compared to traditional processes, this method eliminates the need for solder, flux, and high-temperature heating, fundamentally avoiding the inherent drawbacks of traditional methods.
The advantages of ultrasonic welding are particularly significant compared to traditional soldering. Soldering relies on melting solder to fill the gaps, but the thermal conductivity of solder is much lower than that of copper and aluminum substrates, easily leading to contact thermal resistance. Furthermore, under prolonged high-temperature operation, the solder is prone to aging and detachment, resulting in decreased heat dissipation performance. In contrast, the metallurgical joint formed by ultrasonic welding has a resistivity close to that of the base material, significantly improving thermal conductivity. Simultaneously, the joint shear strength can reach over 36 MPa, and under some optimized processes, it can even exceed 60 MPa, far surpassing the mechanical properties of soldered joints. Moreover, the high temperatures during soldering can easily cause thermal stress cracking between the ceramic and copper layers of copper-clad ceramic substrates, while the low-temperature characteristics of ultrasonic welding effectively protect the ceramic substrate, preventing thermal deformation and structural damage.
In scenarios involving the joining of dissimilar materials, the adaptability of ultrasonic welding further highlights its technological value. The connection between copper-clad ceramic substrates and aluminum heat sinks is a common industry requirement. Traditional processes, due to the significant difference in thermal expansion coefficients between copper and aluminum, are prone to interfacial stress concentration, leading to joint cracking. Ultrasonic welding, through dynamic pressure control and vibration energy optimization, can refine the grain size in the weld nugget area, resulting in a more uniform distribution of interfacial stress. Simultaneously, it avoids excessive formation of brittle intermetallic compounds, controlling the intermetallic compound layer thickness to below 0.2 μm, significantly improving the thermal stability and fatigue life of dissimilar material joints. Under aging conditions at 150℃, the strength reduction rate of the optimized ultrasonic-welded joint can be controlled within a reasonable range, far superior to the aging resistance of joints made using traditional processes.
Ultrasonic welding technology has been widely applied in several high-end manufacturing fields. In SiC inverter modules for new energy vehicles, ultrasonic welding enables efficient connection between copper-clad ceramic substrates and copper heat sinks, improving module heat dissipation efficiency by 12-25% and ensuring stable operation of the motor control system under high-temperature conditions. In GaN RF amplifiers for 5G base stations, the low-temperature welding characteristics effectively protect sensitive electronic components, while the low contact thermal resistance helps the equipment achieve high-frequency, high-power operation. In aerospace electronic equipment, the high mechanical strength and resistance to extreme environments of ultrasonic welded joints meet the usage requirements of radar modules and satellite communication equipment under complex conditions such as high and low temperature cycling, vibration, and shock.
As electronic devices develop towards miniaturization and high power density, ultrasonic welding technology is iterating towards intelligence and precision. By introducing machine learning algorithms, welding pressure, amplitude, and time parameters can be automatically optimized based on substrate material, thickness, and base plate material combination, reducing the joint strength standard deviation to within ±2%. Upgraded flexible fixture design further solves the problem of easy cracking of the ceramic layer in base plate-less power module welding, achieving stable connection between the substrate and terminals through precise positioning and stress buffering. In the future, with the integration of multi-field collaborative processes and biomimetic interface design, ultrasonic welding will achieve breakthroughs in copper-clad ceramic substrate connections, resulting in higher strength, lower thermal resistance, and superior reliability, providing core technological support for the upgrading of the high-end electronics manufacturing industry.
From process principles to practical applications, ultrasonic welding, with its unique technological advantages, breaks the constraints of traditional processes on the connection between copper-clad ceramic substrates and heat sinks. In the high-end manufacturing field, which pursues efficient heat dissipation and reliable operation, this technology is not only a choice for process replacement but also a key lever for promoting industrial technology upgrades and enhancing product core competitiveness, and is expected to occupy a dominant position in the future electronic packaging field.
