Multilayer ceramic wiring carriers (interposers) with thin-film compatible surfaces

Wiring carriers are mechanical substrates on which conductor structures for the electrical connection of electronic components are integrated. These wiring carriers are essential components in electronics manufacturing. They not only serve to connect components electrically, but also perform mechanical, thermal, and shielding functions. Innovative technologies such as LTCC (Low Temperature Cofired Ceramics) and HTCC (High Temperature Cofired Ceramics) enable highly reliable solutions for complex electronic systems.

At Fraunhofer IKTS, wiring carriers, known as interposers, based on low-temperature cofired ceramics (LTCC) have been developed and manufactured for many years. This technology offers decisive advantages over conventional alternatives such as printed circuit board technology (rigid or flexible) or classic thick-film technology:

• High wiring density thanks to high-resolution, thick-film-based printing processes
• Miniaturized vias enable wiring across multiple layers (R&D up to 40 layers)
• Increased packing density through additional integration of passive components (R, L, C) into the inner layers of the substrate
• High mechanical stability under vibration and shock loads
• Thermomechanical adaptation to silicon-based components for maximum reliability during thermal cycles

In the past, Fraunhofer IKTS developed components using multilayer ceramic technology with highly integrated wiring layers on up to 23 ceramic layers for use in a temperature range up to 300 °C. A special feature here is the electrical contacting via bond connections on the cross-sectional areas of sawn-off via structures, which offers an additional degree of freedom for the decoupling of complex electronic circuits. This also allows miniaturized thin-film components to be implemented efficiently. The ceramic substrate surfaces and the metallized vias they contain are polished to a target roughness of Ra ≤ 50 nm for subsequent thin-film processes. This extremely smooth surface is crucial for the reliable integration of thin-film structures and ensures maximum precision in manufacturing.

The use of a commercial material system, such as Celanese's Micromax™ 951 LTCC material system, offers the additional advantage of technology transfer to industrial manufacturers, ensuring the scalability and cost-effectiveness of the technology.