To effectively enhance the radiation bandwidth of 60 GHz patch antennas, a micromachining process for the Low Temperature Co-fired Ceramic (LTCC) substrate was proposed. Specific green tape layers of substrate were micromilled to form perforated structures which were then filled with sacrificial materials. Thereafter, the individual layers were stacked up and sintered to form a three-dimensional (3D) microstructure. The cantilevers, enclosing frame structures and embedded microchannels were fabricated to verify the effectiveness of the process. The electrical properties of the antenna designs were validated by a full-wave analysis, and the effectiveness of the cooling channel was experimentally tested. The experiments show that the proposed process solves problems like the variation of contraction rate in various axes and the collapsing of the embedded cavities. The 3D frame, cantilever and the embedded microfluidic structure are fabricated with a maximum aspect ratio as high as 4∶1, and a total thickness of 1.4 mm (14 layers). The cross section size of the microchannel is as large as 200 μm×200 μm and its maximum length is beyond 2.5 cm. With smooth inner walls, the smooth microfluidic flow may provide a cooling effect over 40 K for the integrated power devices with a heating power density of 2 W/cm2. The simulated radiation pattern shows a doubled increase of radiation bandwidth from 2.7 GHz to 5.3 GHz and has a little gain loss. These results demonstrate that simple and low-cost micromachining may effectively enhance the radiation bandwidth of patch antennas without additional costs, which is beneficial to the design and implementation of large scale and highly integrated transmitting/receiving arrays with active power devices.