Low Temperature Cofire Ceramic
LTCC substrate technology refers to the fabrication of highly compact three-dimensional multilayer circuitry of noble metals within a ceramic form.
LTCC begins as individual soft ceramic-organic tapes or sheets, commonly referenced as 'Green Tape' - a trademark name from the largest source supplier of LTCC materials, Dupont, (other LTCC material vendors include: Ferro, Heraeus, ESL and other company in-house material sets).
Each sheet in the three-dimensional layout may contain vias (vertical interconnects to adjacent layers). Conductive traces or patterns, dielectric patterns, and resistive pastes may be applied by means of screen-printing, photolithography or other means onto each sheet of tape per design requirements. Typical metals for LTCC include: Silver, Palladium, Gold, Platinum or alloys of these materials.
Individual layers are inspected, as sheets with damaged circuitry can be repaired or replaced for yield improvement. Independent layering also provides for in-process replacement from design modifications (very low cost customer design revision).
The sheets are ordered, precisely aligned, stacked and laminated together to form monolithic plates. In this form, complex shapes and cavities can be machined to customer design.
These plates are then placed in a profile controlled furnace where all materials are 'co-fired' simultaneously. The initial stage of the profile burns out the organics (often 350°-450°C) and the final stage of the profile sinters the remaining materials together (often 800°-875°C), leaving only the ceramic, noble metals, and glass. The resulting structure is a hermetic, monolithic, three-dimensional network within a substrate.
LTCC substrates can be designed as simple interfacing to other substrates and circuitry, or designed as a complete System In a Package. Typical LTCC designs include embedded components (resistors, capacitors, inductors, baluns, etc.).
External surfaces of the substrate may be designed to provide for various surface mount attachment of active or passive components, and IC's may be attached via BGA's, flip-chip, wire bonding, epoxy or other means. Populated substrates may be packaged for integration into other systems.
LTCC networks can be designed to range from small, simple components (smaller than 0.1 x 0.1 inches) to larger highly-complex, multi-function circuits (larger than 5.0 x 5.0 inches)
High-density integration provides for LTCC components to be combined within miniaturized surface-mount packages, removing the need for most external components. LTCC designs can include circuit elements in die form for more reduction in size. Since the materials used in LTCC designs are very temperature stable, the need to compensate for variations in temperature is greatly reduced.
Highly thermally conductive heat-sinks can also be designed into the substrate for handling higher power applications.
LTCC is an inexpensive, repeatable, reliable process capable of producing large quantities of digital, RF and microwave components measuring only a fraction of the size of components fabricated with conventional substrate materials.
Our Design Guidelines can provide you with technical information regarding the properties of the materials, and how to design your circuits with our team. Contact Us to find out more.
