CANTILEVER FORCE SENSOR
A cantilever force sensor with relatively lower On-Force is disclosed, which comprises a top stack, a bottom stack, and a spacer. The first spacer is configured between the top stack and the bottom stack and configured in a first side of the force sensor. A second side, opposite to the first side, of the top stack, is cantilevered from the bottom stack. When the force sensor is depressed from the top side, the second side of the top stack moves down using the first spacer as a fulcrum. Since the cantilevered side can be easily depressed down so that the On-Force for the force sensor is reduced and hence a force sensor with a relatively higher sensitivity is created.
The instant application is a continuation application of U.S. application Ser. No. 17/152,668, filed Jan. 19, 2021, which is incorporated by reference herein in its entirety.
BACKGROUND Technical FieldThe present invention relates to a force sensor, especially relates to a cantilever force sensor which can be turned on with a relatively reduced on-force so that a force sensor with higher sensitivity is created.
Description of Related ArtFIGS. 1A˜1D shows a prior art.
Referring to FIG. 1A as disclosed in U.S. Pat. No. 8,371,174, a conventional force sensor comprises a top substrate 10 and a bottom substrate 109, a top electrode 11 is configured on a bottom side of the top substrate 10. A bottom electrode 119 is configured on the top side of the bottom substrate 109. A top piezoresistive layer 12 is configured on the bottom side of the top electrode 11. A bottom piezoresistive layer 129 is configured on the top side of the bottom electrode 119. A space 16 is formed between the two piezoresistive layers 12, 129. As shown in FIG. 1A, a ring spacer 15 is configured between the substrates 10 and 109. The top electrode 11 and bottom electrode 119 are electrically connected to a circuit system 13.
FIG. 1B shows an EE′ section view of the prior art FIG. 1A.
FIG. 1B shows that a ring spacer 15 is configured around the force sensor. The ring spacer 15 resists more against a force applied from the top side of the force sensor.
FIG. 1C shows when a force P is applied to the force sensor of FIG. 1A, the top piezoresistive layer 12 deforms downwardly in the middle portion and contacts the bottom piezoresistive layer 129, at this moment, the piezoresistive layers 12 and 129 have a total thickness of L1. Hence, an output resistance R1 of the force sensor can be determined by the equation R1=p*L1/A.
FIG. 1D shows an electricity property for the prior art.
FIG. 1D shows a curve for Conductance/Capacitance vs Force for FIG. 1C. Referring to FIG. 1D a status when the force sensor is depressed from the top side, at the moment of FIG. 1C, an On-Force starts at point P1 which is apparently greater than the zero force point. This is because the ring spacer 15 resists the force applied from the top of the force sensor.
A disadvantage for the prior art is that an On-Force is relatively greater because the ring spacer 15 gives more resistance to the force applied from the top side. It is hopeful for a person skilled in the art to reduce the On-Force so that a force sensor with a higher sensitivity can be obtained.
When the force sensor FS is depressed from the top side, the left side of the top stack TS moves down using the first spacer S1 as a fulcrum to turn on the force sensor FS. The first spacer S1 has a top end connected to the top piezo layer 22 of the top stack TS and has a bottom end connected to the bottom piezo electrode 24 of the bottom stack BS.
The top stack TS is comprised of a top substrate 20, a top electrode 21, and a top piezo layer 22 in sequence. The bottom stack BS is comprised of a bottom piezo layer 23, a bottom electrode 24, and a bottom substrate 25 in sequence.
A bottom switch SW is configured on the bottom side of the force sensor FS. A first conductive contact C1 is configured on the bottom side of the bottom stack BS of the force sensor FS. A second conductive contact C2, aligned with the first conductive contact C1, is configured on a top side of a printed circuit board 26 of the bottom switch SW. A second spacer S2 is configured between the bottom substrate 25 and the printed circuit board 26, and the second spacer S2 is configured in the right side of the bottom switch SW. The bottom stack BS, the first conductive contact C1, the second conductive contact C2, and the printed circuit board 26 are configured in sequence to form the bottom switch SW. The delayed turn-on switch is designed for shielding the initial noise signal from the force sensor at an initial stage when it is depressed.
The first conductive contact C1 slightly touches the second conductive contact C2, however without turns on the bottom switch SW. When the force sensor FS is depressed from the top side, the left side of the force sensor FS moves down so that the first conductive contact C1 touches the second conductive contact C2 firmly to turn on the bottom switch SW.
The first spacer S1 is configured between the top stack TS and the bottom stack BS and configured in the right side of the force sensor FS. A first gap G1 is configured between the top stack TS and the bottom stack BS. The first spacer S1 has a top end connected to the top piezo layer 22 of the top stack TS and has a bottom end connected to the bottom electrode 24 of the bottom stack BS.
The first spacer S1 is configured between the top stack TS and the bottom stack BS and configured in the right side of the force sensor FS. A first gap G1 is configured between the top stack TS and the bottom stack BS. The first spacer S1 has a top end connected to the top electrode 21 of the top stack TS and has a bottom end connected to the bottom piezo layer 23 of the bottom stack BS.
The top stack TS is comprised of a top substrate 20, and an auxiliary metal 21B in sequence. The auxiliary metal 21B is an auxiliary metal for electricity conductance when the force sensor FS is depressed. The bottom stack BS is comprised of a piezo layer 23, a pair of coplanar electrodes 241, 242, and a bottom substrate 25 in sequence.
The top stack TS is comprised of a top substrate 20 and a top piezo layer 22. The bottom stack BS is comprised of a pair of coplanar electrodes 241, 242, and a bottom substrate 25 in sequence.
The top stack TS is comprised of a top substrate 20, an auxiliary metal 21B, and a top piezo layer 22 in sequence. The auxiliary metal 21B is an auxiliary metal for electricity conductance when the force sensor FS is depressed. The bottom stack BS is comprised of a pair of coplanar electrodes 241, 242, and a bottom substrate 25 in sequence.
A third spacer S3 is configured between the top stack TS and the bottom stack BS. A fourth gap G4 is configured between the top stack TS and the bottom stack BS. The third spacer S3 is configured in the right side of the force sensor FS. The third spacer S3 and has a top end connected to the top piezo layer 22 of the top stack TS, and has a bottom end connected to the bottom piezo layer 23 of the bottom stack BS.
(1) slightly touching the second conductive contact C2 without turning on the bottom switch SW, and
(2) slightly apart from touching the second conductive contact, and
a fourth spacer S4 is configured between the force sensor 30 and the printed circuit board 26 and configured in the right side of the force sensor 30. When the force sensor 30 is depressed from the top side, the left side of the force sensor 30 moves down so that the first conductive contact C1 touches the second conductive contact C2 firmly to turn on the bottom switch SW.
The piezo layers 22, 23 disclosed in this invention is made of a material selected from the group consisting of piezo-electric material, triboelectric material, resistive material, and dielectric material
While several embodiments have been described by way of example, it will be apparent to those skilled in the art that various modifications may be configured without departs from the spirit of the present invention. Such modifications are all within the scope of the present invention, as defined by the appended claims.
REFERENCE NUMBERS
- 20 top substrate
- 21 top electrode
- 21B auxiliary metal
- 22 top piezo layer
- 23 bottom piezo layer
- 24 bottom electrode
- 241, 242 coplanar electrodes
- 25 bottom substrate
- 26 printed circuit board
- 30 force sensor
- 61 pen tip
- G1 first gap
- G2 second gap
- G3 third gap
- G4 fourth gap
- C1 first conductive contact
- C2 second conductive contact
- C3 third conductive contact
- S1 first spacer
- S2 second spacer
- S3 third spacer
- S4 fourth spacer
- SW switch
Claims
1. A cantilever force sensor, comprising a top stack, a bottom stack, a first spacer, a bottom switch, and a second spacer, wherein
- the first spacer is configured, in a thickness direction of the force sensor, between the top stack and the bottom stack, and is configured in a first side of the force sensor,
- a second side, opposite to the first side, of the top stack, is cantilevered from the bottom stack,
- in response to the top stack being depressed toward the bottom stack, the second side of the top stack moves down using the first spacer as a fulcrum,
- one of the top stack and the bottom stack is a first stack,
- another of the top stack and the bottom stack is a second stack,
- the first stack comprises: a first substrate, a first piezo layer, and a first electrode between the first substrate and the first piezo layer in the thickness direction,
- the bottom switch comprises: a first conductive contact configured on a bottom side of the bottom stack; a second conductive contact aligned with the first conductive contact, and configured on a top side of a third substrate, and
- the second spacer is configured between the bottom stack and the third substrate in the thickness direction, and configured in the first side of the force sensor.
2. The cantilever force sensor as claimed in claim 1, wherein
- the third substrate is a printed circuit board.
3. The cantilever force sensor as claimed in claim 1, wherein
- the first conductive contact and the second conductive contact are configured in the second side of the force sensor.
4. The cantilever force sensor as claimed in claim 3, wherein
- in a state where the top stack is not depressed toward the bottom stack, the first conductive contact slightly touches the second conductive contact without turning on the bottom switch, and
- in response to the top stack being depressed toward the bottom stack, the first conductive contact is caused to touch the second conductive contact firmly to turn on the bottom switch.
5. The cantilever force sensor as claimed in claim 3, wherein
- in a state where the top stack is not depressed toward the bottom stack, the first conductive contact is slightly apart from the second conductive contact, and
- in response to the top stack being depressed toward the bottom stack, a second side opposite to the first side of the bottom stack moves down using the second spacer as a fulcrum and causes the first conductive contact to touch the second conductive contact firmly to turn on the bottom switch.
6. The cantilever force sensor as claimed in claim 1, wherein
- the second stack comprises: a second substrate, a second piezo layer, and a second electrode between the second substrate and the second piezo layer in the thickness direction, and
- along the thickness direction, the first spacer overlaps the first substrate and the second substrate, without overlapping the first electrode, the first piezo layer, the second electrode and the second piezo layer.
7. The cantilever force sensor as claimed in claim 6, wherein
- as seen along the thickness direction, the first spacer has a shape of a segment of a circle.
8. The cantilever force sensor as claimed in claim 1, wherein
- the second stack comprises: a second substrate, a second piezo layer, and a second electrode between the second substrate and the second piezo layer in the thickness direction, and
- along the thickness direction, the first spacer overlaps the first substrate, the first electrode, the first piezo layer and the second substrate, without overlapping the second electrode and the second piezo layer.
9. The cantilever force sensor as claimed in claim 1, wherein
- along the thickness direction, the first spacer overlaps the second spacer.
10. The cantilever force sensor as claimed in claim 9, wherein
- the second stack comprises: a second substrate, a second piezo layer, and a second electrode between the second substrate and the second piezo layer in the thickness direction, and
- along the thickness direction, the second spacer overlaps the first substrate, the first electrode, the first piezo layer, the second substrate, the second electrode and the second piezo layer.
11. A cantilever force sensor, comprising a top stack, a bottom stack, and a first spacer, wherein
- the first spacer is configured, in a thickness direction of the force sensor, between the top stack and the bottom stack, and is configured in a first side of the force sensor,
- a second side, opposite to the first side, of the top stack, is cantilevered from the bottom stack,
- in response to the top stack being depressed toward the bottom stack, the second side of the top stack moves down using the first spacer as a fulcrum,
- the top stack comprises: a top substrate, a top piezo layer, and a top electrode between the top substrate and the top piezo layer in the thickness direction,
- the bottom stack comprises: a printed circuit board having, on a top side thereof, a conductive contact, and a bottom piezo layer on the top side of the printed circuit board, wherein the bottom piezo layer is wider than the conductive contact and covers the conductive contact.
12. The cantilever force sensor as claimed in claim 11, wherein
- along the thickness direction, the first spacer overlaps the top substrate and the printed circuit board, without overlapping the top electrode, the top piezo layer, the conductive contact and the bottom piezo layer.
13. The cantilever force sensor as claimed in claim 12, wherein
- as seen along the thickness direction, the first spacer has a shape of a segment of a circle.
14. The cantilever force sensor as claimed in claim 11, wherein
- along the thickness direction, the first spacer overlaps the top substrate, the top electrode, the top piezo layer, the printed circuit board and the bottom piezo layer.
15. The cantilever force sensor as claimed in claim 11, wherein
- along the thickness direction, the first spacer overlaps the top substrate, the top electrode, the top piezo layer, the printed circuit board, without overlapping the bottom piezo layer.
16. The cantilever force sensor as claimed in claim 11, wherein
- along the thickness direction, the first spacer overlaps the top substrate, the printed circuit board and the bottom piezo layer, without overlapping the top electrode and the top piezo layer.
17. A cantilever force sensor, comprising a top stack, a bottom stack, and a first spacer, wherein
- the first spacer is configured, in a thickness direction of the force sensor, between the top stack and the bottom stack, and is configured in a first side of the force sensor,
- a second side, opposite to the first side, of the top stack, is cantilevered from the bottom stack,
- in response to the top stack being depressed toward the bottom stack, the second side of the top stack moves down using the first spacer as a fulcrum,
- the top stack comprises: a top substrate, a top piezo layer, and a top electrode between the top substrate and the top piezo layer in the thickness direction,
- the bottom stack comprises: a bottom substrate, and a bottom piezo layer on a top side of the bottom substrate,
- along the thickness direction, the first spacer overlaps the top substrate and the bottom substrate, without overlapping the top electrode, the top piezo layer and the bottom piezo layer, and
- as seen along the thickness direction, the first spacer has a shape of a segment of a circle.
18. The cantilever force sensor as claimed in claim 17, wherein
- at least one of the top piezo layer or the bottom piezo layer is made of a material selected from the group consisting of piezo-electric material, triboelectric material, resistive material, and dielectric material.
19. The cantilever force sensor as claimed in claim 17, further comprising:
- a bottom switch which comprises: a first conductive contact configured on a bottom side of the bottom stack; a second conductive contact aligned with the first conductive contact, and configured on the top side of a third substrate; and
- a second spacer which is configured between the bottom stack and the third substrate in the thickness direction, and configured in the first side of the force sensor,
- wherein
- the first conductive contact and the second conductive contact are configured in the second side of the force sensor,
- in a state where the top stack is not depressed toward the bottom stack, the bottom switch is not turned on, and
- in response to the top stack being depressed toward the bottom stack, the first conductive contact touches the second conductive contact to turn on the bottom switch.
20. The cantilever force sensor as claimed in claim 17, wherein
- the bottom substrate is a printed circuit board having, on the top side thereof, a conductive contact, and
- the bottom piezo layer is wider than the conductive contact and covers the conductive contact.
Type: Application
Filed: Feb 1, 2023
Publication Date: Jun 1, 2023
Inventors: Chih-Sheng HOU (Taipei), Chia-Hung Chou (Taipei)
Application Number: 18/162,719