Laser Prototyping of Microwave Circuits in LTCC Technology

In this paper, a process for direct laser structuring of microwave circuits in low-temperature co-fired ceramic (LTCC) technology is reported. An efficient alternative to screen printing is proposed for prototyping circuits by laser patterning the conductors on the unfired tape. A line width and gap of 50 ¿m are achieved with laser machining. A range of samples has been studied using a scanning electron microscope in order to optimize the process parameters. The surface roughness of laser-treated samples is measured with a surface profiler and compared with the untreated samples. A method of creating microvias and trenches in thick LTCC substrate is also demonstrated. For 254 ¿m thick green tape, vias with a diameter and separation of 50 ¿ m are realized along with trenches having a width as small as 30 ¿m. The method of optimizing the laser machining process is described in detail. A band-stop mushroom resonator and a microstrip ring resonator filter are fabricated and their results compared against simulations.