HIGH PERFORMANCE RF DIPLEXER MODULE USING A GLASS INTERPOSER

摘要

The growth of the mobile device market has posed a challenging set of filter requirements for RF front end devices. The introduction of a greater set of frequency bands along with standards that drive towards multiple-input-multiple-output (MIMO) configurations make it essential that the filter elements offer low electrical loss, and at the same time maintain good rejection between adjacent bands. Smaller and thinner form factors necessitate small device footprints and thinner profile packages. There are several beneficial properties to realizing broadband filters on glass which include high resistivity, low electrical loss, and adjustable CTE (coefficient of thermal expansion). In this paper, recent performance data will be presented which shows the performance benefits achieved when using glass. A process has been developed to manufacture a glass diplexer module using conventional laminate circuit board processes that have been adapted to handle fragile glass substrates. Over the past few years we have evaluated both Cu plating and electrically conductive adhesives (ECAs) to produce a through glass via (TGV). From this work, it has been determined that Cu plating is a preferred process to form a robust TGV in a manufacturing environment. A Cu plated TGV nicely compliments our semi-additive plating (SAP) processes to produce fine line Cu circuitry on both sides of a glass substrate. In addition, we have successfully laminated an Ajinomoto Buildup Film (ABF) to both sides of a glass substrate having TGVs. The ABF completely filled the vias and also maintained uniform flatness on both sides. The resulting interposer was very flat and suitable for the next level of Cu plating using SAP. The ABF material was able to form high quality blind vias using laser drilling. A more comprehensive characterization of the glass diplexer modules will be presented, which will include X-sections of a double-sided Cu circuitry and Cu MIM (metal-insulator-metal) capacitors and inductors.