Development of a compact bandpass microstrip filter on low loss ultra-thin Coreless substrate for RF-SiP

Along with high performance and miniaturization of electronic components, there is a tremendous demand for package substrate with thinner and higher density Coreless substrate could meet the requirement, which eliminates the core part in the substrate and utilizes only its build up materials to interconnect between the chip and PCB board. The major challenge for coreless substrate manufacturing and assembly process is reducing warpage. In this paper, a low warpage low loss was introduced here. The glass cloth perpreg (PP) HL832NSF was used as coreless substrate. And a novel low cost manufactory process for coreless substrate was also developed by using Semi-Additive process (SAP). Semi-Additive primer (SAPP) was used here to improve the adhesion between the PP and copper. A novel rigid frame was proposed to keep the coreless substrate flat during the manufacture. The low loss of the HL832NSF is quite suitable for RF-System in package. A compact 4 pole microstrip chebyshev band-pass filter was developed for WCDMA downlink application. The minimal space of the filter is 30 um. The proposed filter is fabricated on HL832NSF to demonstrate its RF performance.