Electronic components must keep shrinking, especially for mobile communication equipment. Progressive miniaturization alone has made it possible to extend the functionality of terminals without increasing their dimensions. What used to be a simple mobile phone has now turned into a portable multimedia center - without any increase in size. But there are limits to this trend. Christian Block, executive vice president and general manager, microwave ceramics and modules, describes the situation as follows: "Major progress can no longer be made by continuing to miniaturize discrete passive components alone. So we are opting for passive integration based on LTCC technology."

The low-temperature co-fired ceramic (LTCC) technology used to make these modules is a variant of multilayer ceramic technology. The functions of conventional passive electronic components are implemented between the ceramic layers. According to Christian Block, the fabrication of modules with up to 20 ceramic layers is feasible. The current average is 14 layers. "The action takes place between the ceramic layers", adds Block. "The functions of up to 60 discrete components such as capacitors and inductors as well as fixed and voltage-dependent resistors are embedded here. Up to 20 more components such as SAW filters and PIN diodes - and recently even complete power amplifiers - can also be accommodated in piggy-back fashion."

These tiny modules have edge lengths of only a few millimeters and are hardly more than a millimeter high. Footprints of 4.5 × 3.2 mm are typical of these customer-specific solutions, which save more than 90% of the board space required by conventional designs. "We are now offering our customers complete front-end modules for WLAN terminals and four-band mobile phones. These modules can be handled like a single component and are thus more reliable than discrete solutions", stresses Block. As only one component is involved, mean time between failures (MTBF) is correspondingly high. Customers can also dispense with time-consuming and expensive design work and thus shorten time to market. They can save plenty on logistics too. Where several dozen components once had to be qualified, purchased and managed, this effort is now restricted to a single component. LTCC modules have so far been developed mainly for mobile phones and WLAN terminals. Their high reliability and miniaturization potential have opened up new applications in automotive electronics as well. Here new LTCC modules with even smaller dimensions will be used in automatic transmissions, ABS and vehicle interval radar systems.