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Requirements for Molybdenum-Copper Alloy for 3D Packaging

With the continuous development of integrated circuit technology, the traditional two-dimensional planar packaging method has been difficult to meet the packaging requirements of high-performance computing, 5G communication, AI chips and other fields for miniaturization, high density, and high heat flux density. 

As an emerging packaging architecture, 3D packaging technology adopts vertical stacking of chips, multi-chip integration and heterogeneous integration, which not only improves the integration level, but also brings significant thermal management challenges.

How to effectively conduct heat, suppress thermal stress, and ensure the stability of the packaging system in a limited space has become a key issue in the development of 3D packaging technology. In this context, molybdenum-copper alloy (Mo-Cu) has become increasingly valuable in 3D packaging due to its excellent thermophysical properties.

In a 3D package structure, multiple chips are stacked on top of each other via through-silicon vias (TSVs), micro bumps, or interconnect layers, resulting in a significant increase in thermal power density per unit volume. Too high a heat flux can cause the chip to rise too quickly, causing thermal runaway, signal drift, and even device failure. Therefore, the encapsulation material must have the following properties:

1. High thermal conductivity: to achieve rapid conduction and diffusion of heat inside the chip;

2. Low coefficient of thermal expansion (CTE): matched with chip materials (such as silicon) to reduce thermal stress;

3. Good machinability and stability: adapt to complex miniature packaging structure;

4. Strong compatibility: meet the working conditions under vacuum packaging or inert atmosphere.

Molybdenum-copper alloy is a material composed of molybdenum with high melting point metal and high thermal conductivity metal copper through powder metallurgy technology, which combines the low thermal expansion coefficient of molybdenum (about 5.6×10⁻⁶/K) and the high thermal conductivity of copper (about 380 W/m·K), which is a promising thermal management intermediate layer material, so it is widely used in 3D packaging. 

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