Abstract: Multilayer microchannel aluminum alloy thermal structures are commonly used in power electronics owing to their efficient heat dissipation capabilities. Achieving high-quality bonding is essential for engineering applications. This paper investigates the effects of bonding pressure, holding time, and temperature on the interface microstructure and mechanical properties of the joint created by liquid-phase assisted diffusion bonding of 6063 Al using AlSiMgCu brazing material. The method eliminates the organizational inhomogeneity of brazed joints by extruding liquid filler metal with smaller pressure. It also reduces the stringent requirements of diffusion joining on the surface quality of base material and process parameters. Additionally, it offers high dimensional accuracy and adaptability of process parameters. The microstructure of joints remains consistent across a broad range of parameters. It typically consists of an Al alloy matrix and a small amount of solidified liquid brazing material, which fills micro gaps of the same scale as the surface roughness. The tensile strength of joints remains almost unchanged, which is equal to base material under the parameter of 550 ℃/1 h/2 MPa, with a tensile strength of 107 MPa and a deformation rate of only 0.10%.