May 29, 2012 -- Ricoh Company, Ltd. developed an ink-jet printing (IJP) technique that can produce lead zirconate titanate (PZT) piezoelectric material in a voluntary pattern shape at 2µm film thickness. Ricoh made PZT material into an ink. Ricoh simultaneously developed a lead-free piezoelectric material, bearing the same deformation properties as the PZT material on a silicon substrate.
Combining both technologies will allow users to manufacture a lead-free piezoelectric device that is functionally equivalent to PZT at a low cost, on a silicon substrate using the additive IJP fab process. (PZT contains lead but is exempted from the EU RoHS Directive banning lead in electronics.)
The IJP technique was used to create an actuator. IJP makes more efficient use of materials and labor than traditional semiconductor manufacturing processes, and can be configured to make diverse products in small lot sizes. It also reduces manufacturing costs and environmental impact, the company reports.
Ricoh controlled ink ejection for drawing precise patterns, modifying hydrophilicity and hydrophobicity of a substrate surface, and eliminated discards during firing thick film. This enabled 2µm film thickness, about 50 times that of the film formed with the usual IJP method. There are unique devisals on the nature of a solvent and drying speed control, which are needed to prepare film at a uniform thickness.
Ricoh’s lead-free material has about the same deformation properties (deformation amount when applied voltage) as PZT and could be used as a replacement. It is a system of materials of lead-free barium titanate with tin added (BSnT). This material needs to be fired at high temperature to form a high-quality film. To do so, Ricoh raised the thermal stability of the under layer (electrode layer provided under the piezoelectric material) of the substrate and enabled film formation of BSnT with properties at a practical level on the silicon substrate. Ricoh has adopted a method to use the precursor of BSnT in liquid form, for ink, unlike the conventional powder method. The lead-free material can therefore be used to make micro electro mechanical system (MEMS).
Ricoh will first manufacture a prototype of an actuator, then work on technical solutions, targeting commercialization. Piezo MEMS are used to monitor seismic activity, in information technology, and in other fields.
Ricoh announced both technologies at "The 29th Meeting on Ferroelectric Materials and Their Applications (FMA29)," in Kyoto, Japan, this past week.
Ricoh makes printing technologies. Learn more at http://www.ricoh.com/.
Below: Surface morphology of the BSnT films fired at different temperatures. The one on the right fired at higher temperature shows larger grain size, indicating better film properties.