Tape casting

What Is Tape Casting?

Tape casting is a ceramic and materials processing technique used to fabricate thin, flat sheets from a fluid suspension of powdered material. Developed industrially in the 1950s for electronic substrate production, it remains the principal method for forming ceramic layers in the 20-micrometer to 2-millimeter thickness range. The process transforms a homogeneous slurry of ceramic powder, solvent, binder, and plasticizer into a continuous green tape that can be cut, laminated, and fired to produce dense functional components.

Tape casting draws from colloid chemistry, rheology, and ceramic engineering. The properties of the final component depend heavily on the uniformity and composition of the starting slurry, making material preparation as critical as the casting step itself.

Slurry Preparation

The slurry is the foundation of tape casting. Ceramic powder (typically alumina, zirconia, barium titanate, or silicon nitride) is dispersed in a solvent using a dispersing agent that prevents particle agglomeration. Organic binders such as polyvinyl butyral (PVB) and plasticizers are then mixed in to impart flexibility to the dried tape. The mixture is milled to achieve a uniform particle size distribution, then filtered and deaerated to remove bubbles and aggregates that would otherwise create defects in the cast layer.

Solvent choice influences drying rate, tape flexibility, and processing hazards. Aqueous systems have gained preference for environmental reasons, while solvent-based systems using ketones and alcohols offer faster drying and better binder compatibility. Rheological characterization of the slurry is essential: the suspension must flow smoothly under the doctor blade while resisting sedimentation during storage. Research at Fraunhofer IKTS covers a wide range of material systems including piezoceramics, PVDF-based composites, and oxide ceramics formulated for specific tape casting applications.

Doctor Blade Casting and Drying

In the casting step, the prepared slurry is loaded into a reservoir and allowed to flow beneath a doctor blade, a precisely gapped blade mounted above a moving carrier film, typically polyethylene terephthalate. The gap between the blade and the carrier controls the wet thickness of the deposited layer. As the carrier advances at a controlled speed, the slurry spreads into a continuous film of uniform thickness. On drying, the solvent evaporates and the tape contracts, yielding a flexible green sheet.

Blade geometry influences the hydrodynamics of the casting pool and therefore the surface quality of the tape. Slot-die casting offers an alternative delivery method for high-volume production, allowing tighter control over flow rate. As documented by Fraunhofer IKTS's tape casting and processing program, typical green tape thicknesses after drying range from 20 micrometers to 1 millimeter depending on the application.

Multilayer Structures and Sintering

One of the principal advantages of tape casting is compatibility with multilayer construction. Dried green tapes are cut to shape by stamping or laser cutting, then stacked and laminated under heat and pressure. Individual layers in a stack can carry different compositions or embedded conductor patterns, enabling the production of multilayer capacitors, co-fired ceramic substrates, and solid oxide fuel cell membranes. The laminated stack is then fired in a controlled atmosphere to burn out the organic binders and sinter the ceramic particles into a dense body. Dimensional control during sintering requires precise matching of shrinkage rates across adjacent layers, particularly in multilayer electronic ceramic components where delamination or warping would be unacceptable.

Applications

Tape casting has applications in a range of fields, including:

Related Topics

Ceramics