The Smallest Form Factor GPS for Mobile Devices

We have developed a GPS product to eliminate the enclosure by creating a hollow cavity between active dice and the package substrate. To create the hollow cavity, we use a 2-layer sheet overmold to prevent mold compound encroaching under the dice. Flipped SAW filter and GaAs low noise amplifier (LNA) dice with gold stud bumps are attached to Ultra Low-footprint CSP (ULC) co-fired ceramic substrate using Gold-Gold Interconnect (GGI) thermosonic die attach. This results in the unit's low cost with significant potential profit margin. This is the first time a GaAs LNA has been integrated in a hollow cavity to accommodate the SAW filter requirement. This GPS product is targeted for the mobile RF and handset products. Measurements show the module meets the application-targeted noise figure, in-band gain, and excellent off band rejection. The module has also completed our stringent standards suite of reliability with resolvable minor concern regarding gold stud bump landing pads surface pre-treatment process. The SAW filter's interdigitated transducers are enclosed in a cavity housing, creating an enclosure to avoid contamination of the transducer surface. Any contamination on the surface of transducers can shift frequency response of the filter, causing GPS unit failure. However, presence of the enclosure increases the die area and packaged unit thickness. This paper presents the integration and packaging processes followed by reliability and performance assessment of our front end GPS module.