Trendsetter in packaging technologies
Packaging has a significant impact on the level of miniaturization of electronic components and modules. An array of advanced TDK and EPCOS packaging technologies has enabled ultra-compact products characterized by extremely low insertion heights.
A wide range of technologies developed for the integration and miniaturization of electronic components and modules allows manufacturers to implement smartphones and conventional mobile phones as well as other mobile devices with advanced circuit design and superior performance. For its miniaturized innovative products, TDK uses not only new materials and thin-film and integration technologies, but, in particular, a whole range of packaging technologies. They allow extremely tiny and flat components and modules to be manufactured. And this is a key advantage, especially considering the fact that the insertion height of these miniaturized products is increasingly becoming the decisive parameter.
Several new packaging technologies have been developed in the field of RF filters which enable highly compact components such as SAW filters and duplexers and, thus, also modules with extremely low insertion heights. They include the EPCOS chip-sized SAW packaging (CSSP®-Cu) based on copper frames and the die-sized SAW packaging (DSSP®) technologies as well as the TDK thin-fi lm packaging (TFP) technology. Their miniaturization potential with respect to insertion height is shown in Figure 1.
Rugged CSSP3 Cu-frame technology
SAW filters based on the CSSP3 Cu-frame technology are used either as discrete components or are integrated in a module. Their advantages include low insertion height, compactness and the possibility of integrating additional components into the package. SAW components manufactured in the CSSP3 Cu-frame packaging technology are no more than 450 μm high and are, in contrast to conventional CSSP packages, stable up to molding pressures of 100 bar depending on the process used. Molding processes are frequently used in the further stages of module manufacture (Figure 2).
|Figure 2: EPCOS SAW filter in a CSSP3 Cu-frame package|
DSSP allows extreme miniaturization
The innovative EPCOS DSSP technology is a milestone in the miniaturization of discrete components. For the first time, the package area corresponds to the chip area, allowing the highest level of miniaturization currently possible to be implemented (Figure 3).
|Figure 3: EPCOS SAW filter in a DSSP package|
Filters and duplexers in DSSP technology were developed primarily for use in RF modules, as these products have the greatest need for miniaturization with respect to both footprint and insertion height. This is because state-of-the-art mobile phones and smartphones have to support more and more frequency bands, which requires a corresponding number of filters. Extremely miniaturized components are the only way of allowing the compact dimensions of these devices to be maintained.
The extremely flat design is among the most important performance features of DSSP components, whose insertion height of only 350 μm including the solder bumps make them significantly flatter than products manufactured in other currently available technologies.
With a fine pitch of up to 220 μm, DSSP technology represents the most advanced state of the art in module production: Depending on the processing technique, DSSP products can withstand molding pressures of up to 100 bar and have been tested to IPC/JEDEC J-STD-020B MSL2a.This allows SAW filters of only 0.6 mm × 0.7 mm and duplexers of 1.5 mm × 1.1 mm and less to be implemented. At the same time, these tiny components offer extremely low insertion losses and high selectivity.
The DSSP platform is an outstanding basis for further integration and miniaturization, as the further development of DSSP shows: This will allow the integration on the cap wafer of matching components such as coils with a high Q. The insertion height of these components is 375 μm (275 μm without solder bumps).
Thin-film packaging technology for ultra-flat BAW duplexers
TDK has entered new territory with its even flatter filter components manufactured in TDK thin-film technology, thanks to a combination of outstanding performance features, ultra-compact dimensions and a flat package. Until now, this technology has been used to manufacture products such as multilayer chip inductors, ceramic components for overvoltage protection and MLCCs.
Meanwhile, it is being applied to implement ultra-flat bulk acoustic wave (BAW) filters in TFP packages for use in future highly miniaturized RF modules (Figure 4). Their insertion height is about 200 μm (including solder bumps). TFP technology allows the realization of technologically superior modules and innovative RF architectures.
|Figure 4: Structure of a BAW duplexer in a TFP package|
Stable packaged MEMS technology for smartphones
The packaging technologies for extremely miniaturized RF products are also used for MEMS products such as microphones and pressure sensors (Figure 5). The new EPCOS C920 and C923-MEMS microphones are two of the most compact topport microphones on the market. They use a unique packaging technique which virtually eliminates resonance problems. The C923 MEMS microphone measures only 2.75 mm × 1.85 mm × 0.9 mm and has a flat frequency response to below the lower limit of the audible spectrum, whereas the C920 has a high-pass filter that extracts low frequencies below 100 Hz, thus helping to suppress wind noise.
|Figure 5: Stable packaging for EPCOS MEMS microphones|
One of the latest members of this ultraminiaturized product line is the C914 MEMS microphone. It has a very high signal-to-noise ratio (SNR) of 64 dB(A), making it ideally suited for high-end audio applications in smartphones. Its high SNR and very low THD distortion significantly improve audio quality when recording distant sound sources. In addition to these outstanding acoustic properties, it offers dimensions of only 3.35 mm × 2.5 mm × 1 mm.
Miniaturized pressure sensors from EPCOS are also ideally suited for integration in smartphones. With dimensions of only 2.23 mm × 2.78 mm × 0.7 mm the calibrated and temperature-compensated digital pressure sensor T5400 is one of the most compact sensors worldwide (Figure 6). Designed to measure absolute pressures of 300 mbar to 1200 mbar, it supplies 16-bit resolution at the serial digital interface. It has a low energy consumption of only 0.3 μA in sleep mode and 3 μA in operation. The T5400 requires no further calibration. This benefits developers of navigation devices and mobile phones, which use air pressure measurements to determine the exact height above sea level.
Together with GPS navigation, this altitude measurement allows precise 3D positioning accurate to within a single story of a building. Emergency calls coming from mobile phones equipped with this feature can considerably facilitate the work of rescue teams.