Date: 27/05/2012

Ink jet printing technique by Ricoh to make electronic components out of PZT

These days electronic component manufacturing researchers are exploring Ink-Jet Printing (IJP) technique to make devices as an alternative low cost manufacturing method instead of conventional semiconductor device making.

Ricoh Company has announced it has succeeded in developing a unique IJP technique that can produce PZT (lead zirconate titanate) in a voluntary pattern shape at 2 micro meter-film thickness. The company demonstrated its functionality with an actuator created by this method. Further, Ricoh has simultaneously developed a lead-free piezoelectric material, bearing the same deformation properties as the PZT material on a silicon substrate. Ricoh claims both are world firsts. Ricoh says combining both technologies will allow it to manufacture a lead-free piezoelectric device , bearing functionality equivalent to PZT, on a silicon substrate using the IJP method at low cost and with low environmental impact.

The many advantages of IJP method over conventional semiconductor manufacturing processes include the efficient use of materials, fewer man-hours, reduced environmental impact, sharply reduced manufacturing costs, and the ability to respond to small-lot production of diverse products.

Ricoh said it has made PZT material, currently used extensively for piezoelectric elements, into an ink with a specific technology, and has succeeded in molding a piezoelectric pattern. The pattern demonstrates mechanical deformation properties as an actuator at 2µm film thickness. This thickness is about 50 times that of the film formed with the usual IJP method. This was not possible without the integration of technologies for controlling ink ejection in drawing precise patterns, modifying hydrophilicity and hydrophobicity of a substrate surface, and even, eliminating discards during firing thick film, explains Ricoh. Further, there are unique devisals on the nature of a solvent and drying speed control, which are needed to prepar film at a uniform thickness, adds Ricoh.

PZT is said to have unique piezoelectric properties and ferroelectric properties. It is used in sensors or actuators such as car-navigation systems and high precision positioning devices. Although PZT contains lead, which is designated a controlled substance by the RoHS Directive , PZT is exempted and often used, as there is no alternative material that matches its properties.

Ricoh said it has developed a material having about the same deformation properties (deformation amount when applied voltage) as PZT. It could be used to replace PZT. This was done in a system of materials (BSnT material) of lead-free barium titanate with tin added. 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. This enabled application as a microelectromechanical system (MEMS) and enabled modularization. The application area was significantly extended. Further, Ricoh has adopted a method to use the precursor of BSnT in liquid form, unlike the conventional powder method. Doing so allowed adoption of the IJP method to form piezoelectric film, resulting in cost and environmental advantages.

Ricoh to announce both technologies at "The 29th Meeting on Ferroelectric Materials and Their Applications (FMA29)," a well-known conference, to be held in Kyoto May 23 to 26.