# US 2014/0192118 A1 · Piezoelectric inkjet die stack

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- Number: US 2014/0192118 A1
- Document ID: US20140192118A1
- Status: Published application
- Kind: A1
- Application number: 14/117,053
- Filed: 2011-06-29
- Published: 2014-07-10
- Earliest claimed: 2011-06-29
- Assignees: Hewlett-Packard Development Company, L.P.
- Inventors: Tony S. Cruz-Uribe; Joseph E. Scheffelin; Tsuyoshi Yamashita; Silam J. Choy
- Web page: https://patentgrep.com/patent/US20140192118A1

## CPC

- B41J 2/045: by pressure, e.g. electromechanical transducers
- B41J 2/14233: {of film type, deformed by bending and disposed on a diaphragm}
- B41J 2002/1437: {Back shooter}
- B41J 2202/11: characterised by specific geometrical characteristics
- B41J 2202/12: with ink circulating through the whole print head
- B41J 2202/20: Modules
- B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS

## Abstract

A piezoelectric inkjet die stack includes a circuit die stacked on a substrate die, a piezoelectric actuator die stacked on the circuit die, and a cap die stacked on the piezoelectric actuator die. Each die in succession from the circuit die to the cap die is narrower than the previous die.

## Claims

### Claim 1

A piezoelectric inkjet die stack comprising:
a circuit die stacked on a substrate die;
a piezoelectric actuator die stacked on the circuit die; and
a cap die stacked on the piezoelectric actuator die;
wherein each die in succession from the circuit die to the cap die is narrower than a previous die.

### Claim 2 (depends on 1)

A die stack as in claim 1, wherein an additional die is interposed in the stack that has a width the same as or wider than the die above it in the stack.

### Claim 3 (depends on 1)

A die stack as in claim 1, further comprising a fluid passageway extending through each die to enable fluid flow from the substrate die to the cap die and back.

### Claim 4 (depends on 3)

A die stack as in claim 3, wherein the fluid passageway comprises:
two exit manifolds opposite one another at edges of the die stack;
two entrance manifolds opposite one another between the edges and the center of the die stack; and
one exit manifold at the center of the die stack.

### Claim 5 (depends on 1)

A die stack as in claim 1, further comprising:
a pressure chamber in the piezoelectric actuator die;
an entrance manifold and inlet port in the circuit die to supply ink to the pressure chamber;
an exit manifold and outlet port in the circuit die to allow ink to exit the pressure chamber; and
a bypass channel between the entrance and exit manifolds to enable ink to bypass the pressure chamber.

### Claim 6 (depends on 5)

A die stack as in claim 5, wherein the bypass channel comprises a flow restrictor to restrict the flow of ink.

### Claim 7 (depends on 1)

A die stack as in claim 1, further comprising:
a cap cavity in the cap die to protect a piezoelectric actuator; and
a ribbed upper surface in the cap cavity opposite the piezoelectric actuator.

### Claim 8 (depends on 4)

A die stack as in claim 4, further comprising:
a compliance film spanning a gap in the substrate die and forming a vented air space, the compliance film configured to flex into the air space during an ink pressure surge within an entrance manifold.

### Claim 9 (depends on 1)

A die stack as in claim 1, further comprising:
a pressure chamber in the piezoelectric actuator die; and
a floor to the pressure chamber that comprises an ASIC control circuit.

### Claim 10 (depends on 9)

A die stack as in claim 9, wherein the pressure chamber comprises:
a flexible membrane roof opposite the floor; and
a piezoelectric actuator adjacent the roof to cause the flexible membrane to flex.

### Claim 11 (depends on 10)

A die stack as in claim 10, further comprising a cavity formed in the cap die to seal the piezoelectric actuator.

### Claim 12 (depends on 11)

A die stack as in claim 11, further comprising a ribbed upper surface of the cavity to provide strength to the cavity.

### Claim 13 (depends on 9)

A die stack as in claim 9, further comprising:
a nozzle layer with a nozzle stacked on the cap die; and
a descender in the cap die opposite the floor of the pressure chamber to provide fluid communication between the pressure chamber and the nozzle.

### Claim 14 (depends on 13)

A die stack as in claim 13, wherein the descender is centrally located in the chamber roof such that the piezoelectric actuator is a split actuator having a first actuator segment on one side of the descender and a second actuator segment on another side of the descender.

### Claim 15 (depends on 9)

A die stack as in claim 9, further comprising a passivation layer covering the ASIC control circuit and configured to be in direct contact with ink in the pressure chamber.

### Claim 16 (depends on 9)

A die stack as in claim 9, further comprising a temperature sensing resistor and a heater element as part of the ASIC control circuit to control ink temperature within the pressure chamber.

### Claim 17 (depends on 9)

A die stack as in claim 9, wherein the ASIC control circuit is on the circuit die, the die stack further comprising drive transistors on an edge of the circuit die.

### Claim 18 (depends on 9)

A die stack as in claim 9, further comprising:
a flex cable coupled to an edge of the substrate die;
wire bonds from the edge of the substrate die to the edge of the circuit die; and
wire bonds from the edge of the circuit die to the edge of the actuator die.

### Claim 19

A piezoelectric inkjet printhead comprising:
a pressure chamber formed in a piezoelectric actuator die;
a roof to the pressure chamber comprising a membrane and a piezoelectric actuator on the membrane;
a circuit die adhered to the actuator die and forming a floor to the pressure chamber that is opposite the roof; and
control circuitry fabricated on the circuit die at the floor of the pressure chamber to controllably flex the membrane by activating the piezoelectric actuator.

### Claim 20 (depends on 19)

A printhead as in claim 19, further comprising:
a descender located centrally in the roof such that the membrane and the actuator comprise a split membrane and a split actuator, respectively; and
a nozzle opposite the pressure chamber at one end of the descender, the descender enabling fluid communication between the pressure chamber and the nozzle.