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Molybdenum–copper composites were developed as heat sink materials. In order to reduce the amount of molybdenum used in the composite material, the explosive welding of molybdenum foil to copper plate was studied. Through the analysis of microstructure and elements, ideas for the processing of molybdenum–copper heat sink materials were proposed. The embrittlement of the molybdenum foil could be reduced by using salt as protective layer. The thickness increase in explosive in the weldability window results in more molybdenum melting, which reduces the generation of microcracks in return. The welding strength in the wave waist is lower than that in the wave front, and the thermal stress exceeding the strength limit of the molybdenum foil may be the important reason for the formation of microcracks. Delamination cracks in the isotherm direction and interface cracks in the joint direction can be observed. Methods of reducing temperature gradients such as thermal explosive welding can reduce the occurrence of microcracks. From outside the vortex to the center of the vortex, the copper content gradually decreases, while the molybdenum content gradually increases. The formation of the vortex is mainly dependent on the movement of copper. The molybdenum element in the transition layer is mainly introduced by diffusion process. The melting of molybdenum particles will lead to uneven quality distribution of molybdenum in the vortex. Compared with the copper side, the molybdenum side at the same distance from interface has a higher work hardening. [ABSTRACT FROM AUTHOR]