Multichip Module Technologies:Materials for HTCC Aluminum Packages.

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Materials for HTCC Aluminum Packages

Metal conductors of tungsten and molybdenum are used for compatibility in co-firing to temperatures of 1600°C. Materials compatibility during co-firing dictates that raw materials of alumina with glass used for densification and any conductor metal powders (W, Mo) must be designed to closely match onset,

Multichip Module Technologies-0130

Processing HTCC Ceramics

The raw materials used in fabrication of aluminum substrates include aluminum oxide, glass, binder, plasticizer, and solvent. Materials specifications are used to control alumina particle size, surface area, impurity, and agglomeration. Glass frit is controlled through composition, glass transition and softening point, particle size, and surface area. Molecular weight, group chemistry, and viscosity controls are used for the binder and plasticizer.

Metal Powder and Paste

A thick-film paste often uses metal powder, glass powder, organic resins, and solvents. Compositions are varied to control screening properties, metal shrinkage, and conductivity. Paste fabrication begins with batch mixing, dispersion, and deagglomeration, which are completed on a three-roll mill.

Thick-Film Metallization

The greensheet is cast, dried, stripped from the carrier film, and blanked into defect-free sheets, typically 200 mm2. The greensheet is then processed through punching, screening, and inspection operations.

HTCC in Summary

• Electrical performance characteristics include 50-ohm impedance, low conductor resistance, abil- ity to integrate passive components such as capacitors and inductors, the ability to achieve high wiring density (ease of increasing the number of wiring at low cost), the ability to support high- speed simultaneous switching drivers, and the ease of supporting multiple reference voltages.

• Inherent thermal performance characteristics superior to MCM-L and MCM-D.

• Time-demonstrated reliability.

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