A Compact 28 GHz RF Front-end Module using IPDs and Wafer-level Metal Fan-out Packaging

A new wafer-level packaging (WLP) technology for millimeter-wave power devices is presented, which features simple fabrication, low signal transition loss and thermal consideration. Instead of using through molding via (TMV) process, the proposed WLP technology incorporates thick copper sheet as a core frame to make through-interconnection. Short electroplated interconnection shows transition loss within 0.2 dB and return loss above 20 dB, at frequency range up to 30 GHz. Using this package technology, a 28 GHz RF FEM is designed and fabricated for 5G communication system. To improve the package density and also enhance the RF performances, two integrated passive device (IPD) capacitors for bias network of the PA are integrated in the module. The size of the realized RF FEM is 4.4×4.3 mm2 and its thickness is only 0.2 mm. The measured output power of the FEM is more than 25 dBm and its efficiency is 25 % at the saturation power. The measured noise figure is 3.4 dB and it value is almost same to the initial LNA IC.