Electrical performance characterization for novel multiple compartments shielding and verification on LTE modem SiP

This paper describes the performance characterization for a novel compartment shielding process. The CPS process is developed for molded base SiP module which can form multiple arbitrary shape shielded areas. This compartment shielding structure not only occupies the smallest space itself, the good shielding performance can reduce the leakage and increase more placement area by shortening the keep out distance at the sides and edges near the wall between compartments. It reduces the interference between shielded sub-circuits e.g. digital, analog and RF circuits. The compartment shielding structure is seamlessly connected to the grounding of the substrate, hence has superior isolation performance. The shielding wall which isolates the compartments is made by laser scribing and trench filling. First the model of geometry of CPS wall is built up, boundary condition is set and material parameters are assigned. SE performance of CPS is simulated by HFSS software using Finite Element Method (FEM). Manual Mesh is used to improve the accuracy of simulation. Visualized 3D EM field is extracted for analyzing how and to what extent the defects of process degrading the SE. Besides the shielding effectiveness, the conductivity of filling material and the contact resistance between that material and ground pad beneath the CPS trench is studied and correlated to the shielding performance. Finally we improve the shielding performance of CPS and the simulation model we built up is close to measurement. Moreover, a LTE modem with two shielding trenches is made and its performance is verified. This single mode/dual bands LTE modem module with three compartments accommodate digital, RF Tx and RF Rx circuit with size 23×26×1.9 mm only. The RF performance of this modem is excellent, and meets all 3GPP LTE Category 3 and carrier's requirements, passes FCC/CE EMI, GCF and PTCRB certification. It is found that this compartment shielding process is good for consumer grade SiP module both in technology and in commercial terms.