CN111473894B

CN111473894B - Force sensor

Info

Publication number: CN111473894B
Application number: CN201910067380.3A
Authority: CN
Inventors: 童玺文; 蔡文彬; 吴名清
Original assignee: Coretronic Mems Corp
Current assignee: Coretronic Mems Corp
Priority date: 2019-01-24
Filing date: 2019-01-24
Publication date: 2021-12-14
Anticipated expiration: 2039-01-24
Also published as: CN111473894A

Abstract

The invention provides a force sensor which comprises a sensing element, a first circuit board and at least one second circuit board. The sensing element is provided with a top surface and a bottom surface which are opposite and a sensing part, wherein the sensing part is positioned on the top surface. The first circuit board is arranged on the top surface and electrically connected to the sensing element. The at least second circuit board is connected to the first circuit board, wherein the at least second circuit board shields the sensing element. The sensing part is suitable for generating a sensing signal through external force transmitted to the top surface.

Description

Force sensor

Technical Field

The invention relates to a sensor, in particular to a force sensor.

Background

Micro-Electro-Mechanical systems (MEMS) technology is a design that starts with a miniaturized electromechanical integrated structure. Currently, the common Micro-electromechanical technology is mainly applied to three fields, such as Micro sensors, Micro actuators, Micro structures, and the like, in which the Micro sensors can convert external environmental changes (such as force, pressure, sound, speed, and the like) into electrical signals (such as voltage or current, and the like) to achieve environmental sensing functions, such as force sensing, pressure sensing, sound sensing, acceleration sensing, and the like. The micro-sensor is well-competitive because it can be fabricated using semiconductor processing techniques and can be integrated with integrated circuits. Therefore, the trend of the mems is that the mems is a sensing device using the mems.

For the mems force sensor, a casing is usually added to protect the sensing device in the force sensor and to enhance the overall structural strength of the force sensing device, so as to prevent the sensing device from being exposed and directly bearing a pressing force, which may cause the sensing device to be easily worn. However, if a cover body for covering the sensing element is added to solve the above problem, the overall thickness and manufacturing cost of the sensor are increased. Therefore, how to protect the sensing element of the force sensor and maintain the sensing performance thereof without increasing the overall thickness and manufacturing cost of the sensor is an important issue in the field of micro-electromechanical force sensing.

Disclosure of Invention

The invention provides a force sensor, wherein a sensing element of the force sensor is well protected and has good sensing performance.

The force sensor of the present invention includes a sensing element, a first circuit board, and at least one second circuit board. The sensing element is provided with a top surface and a bottom surface which are opposite and a sensing part, wherein the sensing part is positioned on the top surface. The first circuit board is arranged on the top surface and electrically connected to the sensing element. The at least one second circuit board is connected to the first circuit board, wherein the at least one second circuit board shields the sensing element. The sensing part is suitable for generating a sensing signal through external force transmitted to the top surface.

In an embodiment of the invention, the sensing element and the at least one second circuit board are located on the same side of the first circuit board.

In an embodiment of the invention, at least one of the second circuit boards surrounds the sensing element.

In an embodiment of the invention, the force sensor further includes a first adhesive, wherein the first adhesive is filled between the first circuit board, the at least one second circuit board and the sensing element and covers the sensing element.

In an embodiment of the invention, the force sensor further includes a second adhesive, wherein the first circuit board has an opening. The sensing part pair is positioned at the opening. The second colloid is at least partially arranged in the opening and covers the sensing part. The second colloid is suitable for receiving external force.

In an embodiment of the present invention, the second colloid protrudes from the opening.

In an embodiment of the invention, the force sensor further includes at least one conductive bump, wherein the at least one conductive bump is disposed between the top surface and the first circuit board. The sensing element is electrically connected to the first circuit board through at least one conductive bump.

In an embodiment of the invention, the force sensor further includes at least a third colloid, wherein the third colloid covers the at least one conductive bump.

In an embodiment of the invention, the first circuit board has a first circuit therein and is electrically connected to the sensing element through the first circuit. At least one second circuit board has a second trace therein. One end of the second line is connected to the first line. The other end of the second circuit extends to the tail end of at least one second circuit board to form an electrical contact.

In an embodiment of the invention, the force sensor further includes a signal processing unit, wherein the signal processing unit is disposed on the first circuit board and electrically connected to the sensing element through the first circuit board.

Based on the above, the force sensor of the present invention has the first circuit board and the second circuit board, and the sensing element is connected to the first circuit board and shielded by the second circuit board, so as to provide the force sensor with good structural strength through the first circuit board and the second circuit board and protect the sensing element therein.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

FIG. 1 is a cross-sectional view of a force sensor according to one embodiment of the present invention;

FIGS. 2-5 are cross-sectional views of a manufacturing process of a force sensor according to an embodiment of the invention;

fig. 6 is a cross-sectional view of a force sensor according to another embodiment of the present invention.

The reference numbers illustrate:

100. 200: force sensor

110. 210: sensing element

110a, 210 a: the top surface

110b, 210 b: bottom surface

111. 211: sensing part

120. 220, and (2) a step of: first circuit board

120a, 220 a: opening of the container

121. 221: first line

130. 230: second circuit board

130a, 230 a: groove

130b, 230 b: end tip

131. 231: second line

131a, 231 a: electrical contact

140. 240: the first colloid

140a, 240 a: surface of

150. 250: second colloid

160. 260: third colloid

170: conductive bump

270: first conductive bump

280: signal processing unit

290: second conductive bump

F: external force

Detailed Description

FIG. 1 is a cross-sectional view of a force sensor according to an embodiment of the present invention. Referring to fig. 1, the force sensor 100 of the present embodiment is, for example, a micro-electromechanical force sensor and includes a sensing element 110, a first circuit board 120, at least one second circuit board 130, a first colloid 140, a second colloid 150, a third colloid 160, and at least one conductive bump 170. The sensing element 110 has a top surface 110a and a bottom surface 110b opposite to each other, and has a sensing portion 111, wherein the sensing portion 111 is located on the top surface 110 a. The sensing element 110 may be a piezoresistive sensing element (piezoresistive sensing element), a capacitive sensing element (capacitive sensing element), or other suitable sensing elements, which is not limited in the present invention. The first circuit board 120 is disposed on the top surface 110a and electrically connected to the sensing element 110 through at least one conductive bump 170.

At least one second circuit board 130 is connected to the first circuit board 120 and is located on the same side of the first circuit board 120 as the sensing element 110. The at least one second circuit board 130 forms a recess 130 a. The sensing element 110 is located in the groove 130a and shielded by the at least one second circuit board 130. In the present embodiment, the number of the second circuit boards 130 is one, and the second circuit boards 130 are disposed around the sensing element 110 to form a groove 130a for accommodating the sensing element 110. The first colloid 140 is filled in the groove 130 a. In detail, the first encapsulant 140 is filled between the first circuit board 120, the at least one second circuit board 130 and the sensing element 110 and covers the sensing element 110. In some embodiments, the number of the second circuit boards may be multiple, and the second circuit boards are assembled to form the groove and locate the sensing element therein, so that the second circuit boards are disposed around the sensing element, but the invention is not limited thereto.

The first circuit board 120 has an opening 120 a. The pair of sensing portions 111 of the sensing element 110 is located at the opening 120 a. The second encapsulant 150 is filled in the opening 120a and protrudes from the opening 120a to the first circuit board 120. The sensing part 111 is adapted to enable the sensing element 110 to generate a sensing signal by an external force F transmitted from the second colloid 150 to the top surface 110 a. The first circuit board 120 has a first circuit 121 therein. At least one second circuit board 130 has a second circuit 131 therein. One end of the second line 131 is connected to the first line 121. The other end of the second wire 131 extends to the end 130b of at least one second circuit board 130 to form an electrical contact 131 a. The sensing element 110 is electrically connected to the first circuit 121 in the first circuit board 120 through at least one conductive bump 170. That is, the sensing signal generated by the sensing element 110 can be transmitted to the electrical contact 131a of the end 130b of the at least one second circuit board 130 through the first line 121 and the second line 131. The at least one second circuit board 130 may be connected to other components and integrate the sensing signal generated by the sensing element 110 with the functions of the other components. The force sensor 100 can be applied to a device with a touch function for determining a touch force of a user by its force sensing function. However, the invention is not limited thereto, and the force sensor 100 can be applied to other kinds of devices.

The sensing element 110 is, for example, a piezoresistive sensor (piezoresistive sensor), a material of a main body is, for example, silicon, and the sensing portion 111 thereon is provided with a piezoresistive material, and the piezoresistive material is electrically connected to the corresponding at least one conductive bump 170.

In the present embodiment, the third colloid 160 surrounds at least one conductive bump 170, so as to protect the conductive bump 170 and ensure the bonding between the sensing element 110 and the first circuit 131, and prevent the conductive bump 170 from falling off during the manufacturing process and the use process, thereby preventing the force sensor 100 from being disabled. In this way, the force sensor 100 completely covers the sensing element 110 by the first colloid 140, the second colloid 150 and the third colloid 160, so that the sensing element 110 is well protected, and the sensing element 110 is prevented from contacting moisture and dust in the external environment, thereby reducing the sensitivity of the force sensor 100.

In this embodiment, the second colloid 150 may be different from the first colloid 140 and the third colloid 160 in material. The hardness of the first colloid 140 and the third colloid 160 is greater than the hardness of the second colloid 150, so that the second colloid 150 is relatively soft and has better elastic deformation capability, so as to effectively transmit the external force to the sensing portion 111 of the sensing element 110. In addition, the first colloid 140 and the third colloid 160 with greater hardness can firmly cover the sensing element 110 and the at least one conductive bump 170 and increase the structural strength of the force sensor 100. In other embodiments, the material of the second colloid 150 may be the same as the material of the first colloid 140 and the third colloid 160, which is not limited in the present invention. The first encapsulant 140, the second encapsulant 150, and the third encapsulant 160 may be formed by curing a thermosetting adhesive, a photo-curing adhesive, or other suitable types of adhesive materials, which is not limited in the disclosure.

It should be noted that a surface 140a of the first encapsulant 140 away from the first circuit board 120 is adapted to be flush with the end 130b of the second circuit board 130 or recessed in the end 130b, so as to facilitate electrical connection between the electrical contact 131a on the end 130b and an electronic device other than the force sensor 100. The first colloid 140 may be formed by a mold, or a surface polishing process (e.g., a chemical mechanical polishing process) may be performed after the first colloid 140 is formed.

The force sensor 100 improves the overall structural strength of the force sensor 100 by the arrangement of the first circuit board 120 and the second circuit board 130 around the sensing element 110, so that a casing does not need to be additionally arranged around the force sensor 100 to protect the force sensor 100, and the manufacturing cost is reduced.

The detailed manufacturing flow of the force sensor will be described below. Fig. 2 to 5 are sectional views illustrating a manufacturing process of a force sensor according to an embodiment of the present invention. Please refer to fig. 2. The first circuit board 120 and the at least one second circuit board 130 are connected to each other, and the first circuit 121 in the first circuit board 120 and the second circuit 131 in the at least one second circuit board 130 are electrically connected together. It should be noted that the opening 120a formed on the first circuit board 120 is communicated with the recess 130a formed on the at least one second circuit board 130. In addition, the first circuit board 120 further has a plurality of conductive contacts of the first circuit 121 located in the grooves 130a, so that the first circuit board 120 can be electrically connected to the sensing element 110 (fig. 3) to be disposed later.

Please refer to fig. 3. The sensing element 110 is electrically connected to the first circuit 121 of the first circuit board 120 by forming a conductive bump 170 in the recess 130a on the top surface 110a thereof, for example, by solder bonding. The conductive bump 170 is formed on the top surface of the sensing element 110 by, for example, electroplating, printing, or ball-planting, and is electrically connected to the first circuit 121 of the first circuit board 120, which is not limited in the present invention. The sensing portion 111 of the sensing element 110 is aligned to the opening 120 a. It should be noted that the distance between the end 130b of the at least one second circuit board 130 having the electrical contact 131a and the first circuit board 120 is greater than the distance between the bottom surface 110b of the sensing element 110 and the first circuit board 120, so that the sensing element 110 can be completely located in the recess 130a and shielded by the at least one second circuit board 130.

Please refer to fig. 4. In order to protect the conductive bumps 170 from being damaged by the subsequent processes and to stabilize the connection between the first circuit board 120 and the sensing element 110, the third encapsulant 160 is formed, for example, in a dispensing manner, so as to encapsulate the at least one conductive bump 170.

Please refer to fig. 5. Next, the opening 120a is filled with a second colloid 150. The second encapsulant 150 is formed by dispensing or injection molding, for example, and completely fills the opening 120 a. The top of the second colloid 150 is suitable for being stressed (labeled as an external force F) as shown in fig. 1 to generate elastic deformation of the second colloid 150, and the sensing element 110 is suitable for sensing the elastic deformation of the second colloid 150 to generate a sensing signal. Meanwhile, the second colloid 150 protrudes from the first circuit board 120 and is adapted to receive an external force.

Please refer back to fig. 1. The first colloid 140 is filled in the recess 130a formed by the at least one second circuit board 130 by, for example, injection molding, and completely covers the sensing element 110. Through the above steps, the entire configuration of the force sensor 100 is completed.

Fig. 6 is a cross-sectional view of a force sensor according to another embodiment of the present invention. The configuration and operation of the sensing element 210, the top surface 210a, the bottom surface 210b, the sensing portion 211, the first circuit board 220, the opening 220a, the first circuit 221, the at least one second circuit board 230, the groove 230a, the end 230b, the second circuit 231, the electrical contact 231a, the first colloid 240, the surface 240a, the second colloid 250, the third colloid 260, and the first conductive bump 270 of the force sensor 200 are similar to the configuration and operation of the sensing element 110, the top surface 110a, the bottom surface 110b, the sensing portion 111, the first circuit board 120, the opening 120a, the first circuit 121, the at least one second circuit board 130, the groove 130a, the end 130b, the second circuit 131, the electrical contact 131a, the first colloid 140, the surface 140a, the second colloid 150, the third colloid 160, and the conductive bump 170 of fig. 1, and will not be described herein again. The difference between the force sensor 200 and the force sensor 100 is that the force sensor 200 further includes a signal processing unit 280, and when the first circuit board 220 is connected to the at least one second circuit board 230, a space is reserved in the groove 230a, so that the signal processing unit 280 is disposed on the same side of the first circuit board 220 as the sensing element 210 and is shielded by the at least one second circuit board. Besides, the first circuit board 220 reserves a plurality of contacts of the first circuit 221, and the signal processing unit 280 is electrically connected to the first circuit 221 of the first circuit board 220 through at least one second conductive bump 290 in addition to the at least one first conductive bump 270 and the sensing element 210. The first encapsulant 240 also encapsulates the signal processing unit 280. The sensing signal from the sensing portion 211 of the sensing element 210 can be transmitted to the signal processing unit 280 through the first line 221 in the first circuit board 220, and processed by converting or filtering noise in the signal processing unit 280, and connected to other electronic devices through the second line 231.

In summary, the force sensor of the present invention accommodates the sensing element through the space formed by the first circuit board and the second circuit board, so as to provide the force sensor with good structural strength and provide the electrical connection between the sensing element and other electronic elements. And the sensing element is coated by the first colloid, the second colloid and the third colloid, so that the sensing element is well protected, and the sensing element is prevented from being exposed and easily damaged. Through the elastic deformation characteristic of the second colloid protruding out of the opening of the first circuit board, the pressing force acting on the second colloid can be smoothly transmitted to the sensing element along with the deformation of the second colloid, so that the sensing element can accurately sense the pressing force.

Although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A force sensor, comprising:

the sensing element is provided with a top surface and a bottom surface which are opposite and a sensing part, wherein the sensing part is positioned on the top surface;

the first circuit board is arranged on the top surface and is electrically connected with the sensing element; and

at least one second circuit board connected to the first circuit board, wherein the at least one second circuit board shields the sensing element,

wherein the sensing part is adapted to generate a sensing signal by an external force transmitted to the top surface,

wherein the at least one second circuit board surrounds the sensing element,

the first circuit board is internally provided with a first circuit and is electrically connected with the sensing element through the first circuit, the at least one second circuit board is internally provided with a second circuit, one end of the second circuit is connected with the first circuit, and the other end of the second circuit extends to the tail end of the at least one second circuit board to form an electrical contact.

2. The force sensor of claim 1, wherein the sensing element is located on the same side of the first circuit board as the at least one second circuit board.

3. The force sensor according to claim 1, further comprising a first gel, wherein the first gel fills between the first circuit board, the at least one second circuit board and the sensing element and covers the sensing element.

4. The force sensor according to claim 1, further comprising a second adhesive body, wherein the first circuit board has an opening, the pair of sensing portions is located in the opening, the second adhesive body is at least partially disposed in the opening and covers the sensing portions, and the second adhesive body is adapted to receive the external force.

5. The force sensor according to claim 4, wherein the second gel protrudes from the opening.

6. The force sensor according to claim 1, further comprising at least one conductive bump, wherein the at least one conductive bump is disposed between the top surface and the first circuit board, and the sensing element is electrically connected to the first circuit board through the at least one conductive bump.

7. The force sensor according to claim 6, further comprising at least a third gel, wherein the third gel encapsulates the at least one conductive bump.

8. The force sensor according to claim 1, further comprising a signal processing unit, wherein the signal processing unit is disposed on the first circuit board and electrically connected to the sensing element through the first circuit board.