Failure Modes and Effects Analysis of Mobile Phones

Model

In this study, SEMCAD X was applied for a sensitivity analysis of various parts inside a recent quad-band phone. The original detailed CAD dataset of the commercial quad-band phone from Motorola Inc. consisting of >1000 IGES parts were directly imported into the SEMCAD X platform and processed without major simplifications. The model consisted of a multi-layer PCB, helical antenna, shielding, display, battery, connectors, digital components and dielectric housing parts. Freespace and device+ homogeneous SAM head configurations for touch position were considered to investigate whether enhanced SEMCAD X environment can proof its value to identify failure modes and their effects to RF performance.

Simulation

Minimum spatial grid resolutions of 0.1 mm were used to resolve the critical details such as multi-layer PCB and the curvature of the thin helical antenna via the automated grid generation. Maximum grid resolutions were reduced in the area of the head phantom, where high permittivity occurs. Broadband and harmonic simulations were run to investigate the performance at different operational bands. Finally, the effects of critical parameters on performance behaviour were virtually determined in a semi-automatic manner by using the Python language based scripting engine and by performing a large number of simulations. The availability of the SEMCAD X’s latest hardware acceleration providing computation speeds up to 600-800 MCells enables such a simulation of the device in less than 5 minutes.

Results

Far-field measurements were made at different operational bands using the DASY4 measurement system and used to validate simulation results. Excellent agreement was obtained. For failure modes analysis, some of the connections that were tested are shown in figure at left. The influence of the grounding of the LCD bracket can be easily seen from the recorded higher surface currents when the bracket is not properly grounded. Furthermore, an increase in spatial peak average SAR is also recorder for this case. This study demonstrated that the speed and features provided by SEMCAD X exceeds the use as a common simulation platform and revealed its value as a predictive engineering tool for product development environment. 
 
For further information related to this study download the publication of R. Tay, et al., 2006.