Konica Minolta’s silicon MEMS printhead

EP 2 716 461 A1
Inkjet head and inkjet drawing device provided with same
Konica Minolta, Inc.

This patent application seeks to overcome two problems. When designing a high density printhead with multiple rows of nozzles it is difficult to provide electrical connections to actuators as the wiring must pass between other chambers. In addition the electrical contacts and piezo actuators may be sensitive to moisture.

April-14aHere a section through the printhead is shown. At the bottom is a silicon nozzle plate 11 and a spacer layer 12 made from glass. Next is a silicon on insulator (SOI) substrate, with layer 13 forming the chambers and thin layer 14 forming the diaphragm. Thin film piezo actuators 31 are formed on the diaphragm layer. At the top of the printhead is the wiring substrate layer 21 which is also silicon. On the surface of the wiring substrate are the wiring

Connections between the external exible circuit board 25 with driver chips 24 and the actuators. The printhead assembly is connected to the wiring substrate layer 21 by a resin adhesive layer 30. This is patterned to provide cavities for the actuators and the ink channels. above the printhead is ink manifold 40.

April-14bOn the left the structure is shown in more detail. The wiring on the substrate 21 is more visible. Connections are made from the upper surface to the lower surface with vias. Both top and bottom surfaces of the wiring substrate are protected by films 26 and 28. As the wiring substrate only has ink passages through it, almost the whole surface is available for wiring tracks to the multiple actuator rows.

On top of the piezo actuator is a gold bump 16. At the corresponding point on the wiring substrate is a solder bump 29. Heating the printhead to above the solder melting point of 139C makes the connection. the printhead and wiring substrates are fixed together by the resin adhesive layer 30 in the presence of dry nitrogen. This results in the actuators being encapsulated in a dry inert environment, preventing both the electrical connections and actuators from deterioration in the presence of moisture.