Lamination of LTCC at low pressure and moderate temperature using screen-printed adhesives

In this work, we investigate a new method of low-pressure lamination of low-temperature cofired ceramic (LTCC) tapes, by pre-coating with specially-formulated adhesive layers. This allows fabrication of intricate structures that would be destroyed by high lamination pressures, yet preserves compatibility with standard processing operations, such as blanking, laser cutting, punching, via filling and screen printing. Techniques proposed previously are application of adhesive tapes, solvents or glues. These methods are applied after the tape processing steps and therefore require an extra operation in the processing chain, which may be unpractical, especially if the tape is very thin has been extensively cut. In our procedure, the adhesives are printed and dried on the blanked tape before any other operation, with the drying step also useful for pre-conditioning the tapes, which may then be stored as "standard" blanks. The adhesives are formulated to have low tack at room temperature, making them compatible with standard processing, but to become very soft at 50-60°C, allowing lamination at low pressures. Compatibility with different tape materials is investigated, and the requirements for adequate adhesive formulation are discussed