With the development of integrated circuits towards high performance, miniaturization and high integration, three-dimensional packaging technology has become a mainstream trend in the semiconductor industry.
3D packaging achieves a high-density, high-bandwidth, low-power package structure by stacking multiple chips vertically and utilizing vertical interconnects (e.g., TSVs, through-silicon vias). The development of this technology has put forward higher requirements for packaging materials, especially in thermal management, mechanical strength, thermal expansion matching, etc. Molybdenum-Cu alloy is becoming one of the key support materials in 3D packaging due to its excellent thermal conductivity, low coefficient of thermal expansion, good mechanical properties and machinability.
1. Heat Sink and Heat Spreader
One of the most important applications of Mo-Cu alloys is as a heat sink or heat diffuser plate. Due to the large number of chip layers and high power density, 3D packaging is prone to "hot spots" accumulation, which affects the performance and lifetime of the device. Mo-Cu alloys have high thermal conductivity (up to 180–220 W/m·K) and good thermal diffusion properties, which can quickly remove the heat generated by the chip from the inside of the package and prevent heat accumulation. At the same time, its coefficient of thermal expansion is between silicon (~3 ppm/°C) and copper (~17 ppm/°C), typically 6–8 ppm/°C, and has good thermal compatibility with semiconductor materials and ceramic packaging substrates, which can effectively reduce the risk of thermal stress and cracking.
2. Substrate Support Structure
In 3D stacked chip constructions, a strong, dimensionally stable metal support material is often required for the bottom or middle chip to support the weight of the upper chip and to ensure that the entire structure does not warp or deform during thermal cycling. Due to its high modulus of elasticity and high temperature stability, molybdenum copper is used as an interposer baseplate to ensure the mechanical strength and long-term reliability of the package stacking structure.
3. Interposer thermal pad
In through-silicon vias (TSVs) or wafer-level 3D packages, interposers are the key components that connect the electrical signals and thermal paths of the upper and lower chips. Molybdenum copper can be used as the thermal conductivity path of the interposer and play a stable role as a thermal conductivity bridge. Some advanced processes combine the Mo-Cu composite structure with a ceramic interposer to take into account both electrical and thermal properties.
4. Micro heat sink and customized thermal structure parts
There is a growing need for localized thermal management in 3D packaging, especially in high-power computing chips (e.g., GPUs, AI chips). Mo-Cu alloys can be precision machined into miniature thermal structures, such as micro-grooves, micro-pillars, or embedded heat sinks, etc., which can be integrated into the package for more efficient heat dissipation control. At the same time, due to its excellent machinability, various shapes can be customized to suit different packaging schemes.
5. Package Cover Plate (Lid) and Thermally Conductive Sandwich (TIM Support)
In some 3D packaging modules, molybdenum copper is also used as a cover plate for the package housing, or as a stable support structure between thermal interface materials (TIMs). By working in tandem with materials such as high thermal grease and graphite sheets, the Mo-Cu cover plate can further improve the overall heat dissipation efficiency and reliability of the package.
6. Application in high-frequency and high-power packaging
With the development of 5G communication and high-frequency radar technology, 3D packaging is gradually expanding to high-frequency and high-power scenarios. Due to its excellent thermal stability, electromagnetic compatibility and non-magnetic characteristics, molybdenum-copper alloy is used as the thermal control base and structural support of power amplifier modules (PA modules), radio frequency devices (RF devices) and other devices, providing a solid foundation for high-frequency signal transmission.
