The disclosure relates to the technical field of electronic devices, in particular to a flexible circuit board, an ultrasonic fingerprint module, and an electronic device.
An electronic device with an ultrasonic fingerprint module is more and more popular with users, due to its accurate collecting of users' fingerprints even when fingers have dirt or oil stains.
In traditional manufacturing of the ultrasonic fingerprint module, an anisotropic conductive film (ACF) is firstly applied to a base plate, and then a part of a flexible circuit board is bonded to the base plate with the ACF (e.g., a first bonding process), for electrical connection with pixel electrodes. In a bonding process, the ACF may overflow to an electrode layer and solidify (e.g., cured). In this way, another part of the flexible circuit board can be bonded to the electrode layer through the solidified ACF (e.g., a second bonding process). However, connection achieved through a secondary bonding of the ACF is not strong enough. In addition, in the secondary bonding process, the ACF accumulated between the flexible circuit board and the electrode layer is not compacted by a pressing head, and there is a gap between the flexible circuit board and a electrode layer, which allows external air or water vapor easily enter into the gap and affect the electrical connection between the flexible circuit board and the electrode layer, thus affecting electrical connection reliability of the ultrasonic fingerprint module.
The disclosure provides a flexible circuit board, an ultrasonic fingerprint module, and an electronic device.
The flexible circuit board provided in an implementation includes a substrate, one first pin, and multiple second pins. The substrate includes a first connection area and a second connection area connected with the first connection area. The first pin is disposed in the first connection area and the multiple second pins are disposed in the second connection area. The first pin has a first connection surface away from the substrate. The first pin defines an accommodation space. The accommodation space has an opening on the first connection surface.
In this implementation, by defining the accommodation space in the first pin, part of an anisotropic conductive film (ACF) can be filled into the accommodation space during a process of bonding the first pin to an electrode layer. In this way, the ACF formed between the first connection surface and the electrode layer has a small thickness, thus ensuring that conductive particles in the ACF can be electrically connected with both the first pin and the electrode layer at the same time, and further ensuring electrical connection stability between the first pin and a first portion of the ACF.
In addition, when the ACF between the first connection surface and the electrode layer has a small thickness, no gap will be generated between the flexible circuit board and the electrode layer, thus ensuring that no external water vapor or air will enter.
In addition, by defining the accommodation space in the first pin, a contact area between the first pin and the first portion is increased, so that electrical connection stability between the first pin and the first portion can be improved.
In an implementation, the first pin has a second connection surface. The second connection surface is disposed opposite to the first connection surface. The accommodation space extends through the second connection surface. In this way, the accommodation space has a large volume so that more ACF can be accommodated in the accommodation space during bonding of the first pin to the electrode layer, thereby reducing the thickness of the ACF between the first connection surface and the electrode layer, and ensuring that the conductive particles in the ACF can be electrically connected to the first pin and the electrode layer at the same time.
In an implementation, the first pin has a circumferential side surface. The circumferential side surface is connected between the first connection surface and the second connection surface. The accommodation space extends through at least part of the circumferential side surface, that is, the circumferential side surface has an opening of the accommodation space. In this way, when the first pin is bonded to the first portion, part of the ACF can flow out in a direction away from the first pin through the opening of the circumferential side surface, thereby further reducing the thickness of the ACF disposed between the first connection surface and the electrode layer.
In an implementation, the accommodation space has a planar groove side wall. The groove side wall has an included angle relative to the first connection surface. The included angle is greater than 90°. In this way, compared with an included angle of 90°, in this implementation, the included angle is set to be greater than 90° so that a surface area of the groove side wall of the accommodation space is larger. Therefore, on one hand, during bonding of the first pin of the flexible circuit board to the electrode layer, more ACF can be accommodated in the accommodation space, thereby reducing the thickness of the ACF disposed between the first connection surface and the electrode layer; on the other hand, the contact area between the first pin and the first portion is increased, thereby improving the electrical connection stability between the first pin and the first portion.
In addition, compared with an included angle which is less than or equal to 90°, in this implementation, by setting the included angle to be greater than 90°, difficulty in preparing the accommodation space at the first pin can be reduced.
In an implementation, the accommodation space has a cambered groove side wall, and the cambered groove side wall is concave in a direction away from a center of the accommodation space. In this way, the surface area of the groove side wall of the accommodation space is larger. Therefore, on one hand, during bonding of the first pin of the flexible circuit board to the electrode layer, more ACF can be accommodated in the accommodation space, thereby reducing the thickness of the ACF disposed between the first connection surface and the electrode layer, and on the other hand, the contact area between the first pin and the first portion is increased, thereby improving the electrical connection stability between the first pin and the first portion.
In an implementation, the accommodation space has multiple accommodation spaces arranged in an array. In this way, the accommodation space has a large total volume, that is, more ACF can be accommodated in the accommodation space, thereby reducing the thickness of the ACF between the first connection surface and the electrode layer. In addition, the contact area between the first pin and the first portion can also be increased, thereby improving the electrical connection stability between the first pin and the first portion.
The ultrasonic fingerprint module provided in an implementation includes a base plate, multiple pixel electrodes, a piezoelectric element, an electrode layer, an ACF, a fingerprint chip, and the flexible circuit boards described in any of above implementations. The base plate has a first surface. The multiple pixel electrodes are disposed on the first surface. The piezoelectric element is disposed on surfaces of the multiple pixel electrodes away from the first surface and covers the multiple pixel electrodes. The electrode layer is at least partially disposed on a surface of the piezoelectric element away from the first surface. The ACF includes a first portion and a second portion connected with the first portion, and the first portion is disposed on the electrode layer and the second portion is partially disposed on the first surface. The first connection surface of the flexible circuit board is attached to the first portion, and the first portion is partially received in the accommodation space, the first pin is electrically connected with the electrode layer through the first portion, and the multiple second pins are disposed in the second portion and electrically connected with the multiple pixel electrodes through the second portion. The fingerprint chip is mounted on the flexible circuit board and electrically connected between the first pin and the second pins.
In this implementation, the first pin defining the accommodation space is bonded to the first portion so that part of the ACF can be disposed in the accommodation space. In this way, the ACF formed between the first connection surface and the electrode layer has a small thickness, thus ensuring that conductive particles in the ACF can be electrically connected with both the first pin and the electrode layer at the same time, and further ensuring the electrical connection stability between the first pin and the first portion and thus a stable electrical connection of the ultrasonic fingerprint module.
In an implementation, the electrode layer includes a body part and an extension part connected with the body part. A thickness of the body part in a first direction is larger than that of the extension part in the first direction. The first direction is a direction directed from the base plate to the piezoelectric element. The first portion is disposed on the extension part.
In this implementation, the first pin of the flexible circuit board is electrically connected with the extension part, so that the flexible circuit board and the electrode layer are partially overlapped in a thickness direction of the ultrasonic fingerprint module, thereby reducing a thickness of the ultrasonic fingerprint module and facilitating thinning of the ultrasonic fingerprint module.
In addition, since the thickness of the body part in the first direction is greater than that of the extension part in the first direction, when the first portion is disposed on the extension part, a probability that the conductive particles in the ACF are not easily crushed by the pressing head due to being trapped in the first portion can be reduced.
In an implementation, the thickness of the first portion in the first direction is greater than or equal to that of the extension part in the first direction.
It can be understood that because the thickness of the first portion in the first direction is greater than or equal to the thickness of the extension part in the first direction, during bonding of the first pin to the first portion, the conductive particles of the ACF will be easily crushed by the pressing head because the conductive particles are not likely to be trapped in the first portion, thereby ensuring the electrical connection stability between the flexible circuit board and the electrode layer, and further ensuring connection reliability of the ultrasonic fingerprint module.
In an implementation, the electrode layer includes a main body part, a conductive part, and a connection part connected between the main body part and the conductive part. The main body part is disposed on a surface of the piezoelectric element away from the first surface. The connection part is disposed on a side surface of the piezoelectric element, the conductive part is disposed on the first surface, and the first portion is disposed on the conductive part.
In this implementation, the first pin of the flexible circuit board is electrically connected with the conductive part, so that the flexible circuit board, the electrode layer, and the piezoelectric element are partially overlapped in the thickness direction of the ultrasonic fingerprint module, thereby reducing the thickness of the ultrasonic fingerprint module and facilitating thinning of the ultrasonic fingerprint module.
In an implementation, the thickness of the first portion in the first direction is greater than or equal to that of the conductive part in the first direction. The first direction is a direction directed from the base plate to the piezoelectric element.
It can be understood that because the thickness of the first portion in the first direction is greater than or equal to the thickness of the conductive part in the first direction, during bonding of the first pin to the first portion, the conductive particles of the ACF will be easily crushed by the pressing head because the conductive particles are not likely to be trapped in the conductive part, thereby ensuring the electrical connection stability between the flexible circuit board and the electrode layer, and further ensuring connection reliability of the ultrasonic fingerprint module.
In an example, the electrode layer is made from silver.
In this example, because the silver is of a low price and is with a good conductivity, when the electrode layer is made from the silver, both the connection stability between the electrode layer and the flexible circuit board and a low cost of the ultrasonic fingerprint module can be ensured.
In an example, the ultrasonic fingerprint module includes a protective layer covering the surface of the electrode layer away from the piezoelectric element.
In this implementation, the protective layer is disposed on and covers the surface of the electrode layer away from the piezoelectric element to protect the electrode layer, and the electrode layer can be prevented from being damaged due to collision with other components, furthermore, the electrode layer can be prevented from being oxidized, thereby ensuring a reliable connection between the electrode layer and the piezoelectric element.
The electronic device provided in an implementation of the disclosure includes a housing, a display screen, and the ultrasonic fingerprint module described above. The display screen is mounted on the housing. The display screen and the housing define a device accommodation cavity. The ultrasonic fingerprint module is received in the device accommodation cavity. A top surface of the connection part of the ultrasonic fingerprint module faces the display screen.
In this implementation, the ultrasonic fingerprint module is disposed in the device accommodation cavity, so that when a user's finger is placed in a fingerprint collecting area of the display screen, the ultrasonic fingerprint module can accurately collect the user's fingerprint. In addition, because of the good electrical connection reliability of the ultrasonic fingerprint module, the electronic device also has a good reliability in the process of collecting the user's fingerprint.
In order to illustrate structural features and functions in this disclosure more clearly, the following detailed description will be made with reference to the drawings and specific implementations.
Technical solutions of implementations will be described clearly and completely with reference to accompanying drawings in the implementations. Apparently, implementations hereinafter described are merely some implementations, rather than all implementations, of the disclosure. All other implementations obtained by those of ordinary skill in the art based on the implementations herein without creative efforts shall fall within the protection scope of the disclosure.
As illustrated in
Reference is made to
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In an example, the ultrasonic fingerprint module 30 can compare the collected fingerprints with standard fingerprints stored in the database. The standard fingerprints refer to correct fingerprints stored by the user in the database in advance. A controller (not shown in
Reference is made to
The base plate 31 has a first surface 311. The base plate 31 can be, but is not limited to, made from glass or a polyimide film. A shape of the base plate 31 is adapted to that of the display screen 20. The base plate 31 made from glass or a polyimide film has advantages of low cost and good light transmittance. Therefore, the ultrasonic fingerprint module 30 (e.g., ultrasonic sensor 30) made of the base plate 31 also has the advantages of low cost and good light transmittance. When the ultrasonic sensor 30 is integrated in the display screen 20, the ultrasonic sensor 30 with a good light transmittance will not block display of the display screen 20.
The multiple pixel electrodes 32 are disposed on the first surface 311. The multiple pixel electrodes 2 are distributed in an array. The pixel electrode 32 can be, but is not limited to, made from any one of Indium tin oxide (ITO), silver nanowire (e.g., Ag nanowire), metal mesh, carbon nanotube, and Graphene. In this way, the pixel electrode 32 has a good flexibility and light transmittance, that is, the ultrasonic sensor 30 has a good flexibility and light transmittance.
The piezoelectric element 33 is disposed on surfaces of the multiple pixel electrodes 32 away from the first surface 311 and covers the multiple pixel electrodes 32. The piezoelectric element 32 is made from piezoelectric material. The piezoelectric element 32 transmits and receives the ultrasonic wave with piezoelectric effect. The piezoelectric material can be, but is not limited to, polyvinylidene fluoride (PVDF). Because PVDF has a good flexibility and light transmittance, the piezoelectric element 33 also has a good flexibility and light transmittance. In this way, the ultrasonic sensor 30 also has a good flexibility and light transmittance.
The electrode layer 34 is at least partially disposed on a surface of the piezoelectric element 33 away from the first surface 311. The electrode layer 34 covers the surface of the piezoelectric element 33 away from the first surface 311. In an example, the electrode layer 34 is made from silver. Because the silver is of a low price and is with a good conductivity, when the electrode layer 34 is made from the silver, both the connection stability between the electrode layer 34 and the flexible circuit board 37 and a low cost of the ultrasonic fingerprint can be ensured.
The ACF 35 includes a first portion 351 and a second portion 352 connected with the first portion 351. The first portion 351 is disposed on the electrode layer 34. The second portion 352 is partially disposed on the first surface 311. The second part 352 is partially disposed on a side surface of the piezoelectric element 33. The ACF 35 has conductive particles therein. When the conductive particles are broken under pressing by the pressing head, the conductive particles can electrically connect two components in a force application direction.
The flexible circuit board 37 includes a first connection area 371 and a second connection area 372 connected with the first connection area 371. The first connection area 371 is electrically connected with the electrode layer 34 through the first portion 351. The second connection area 372 is electrically connected with the multiple pixel electrodes 32 through the second portion 352. The ACF 35 can electrically connect the two components in the force application direction, so a short circuit the multiple pixel electrodes 32 can be avoided with the ACF 35. In an example, the flexible circuit board 37 may be disposed on a side of the base plate 31 away from the pixel electrodes 32. In addition, in another example, the flexible circuit board 37 is provided with a connector so that the ultrasonic sensor 30 can be electrically connected with other electronic components through the connector of the flexible circuit board 37.
The fingerprint chip 36 is mounted on the flexible circuit board 37. The fingerprint chip 36 can be configured to control a voltage across the piezoelectric element 33. For example, the fingerprint chip 36 can control the electrode layer 34 to communicate with a high-frequency voltage, and the pixel electrodes 32 to be grounded. In this way, when the high-frequency voltage is applied to the piezoelectric element 33, the piezoelectric element 33 generates and emits ultrasonic waves outward. In addition, the fingerprint chip 36 is also configured to receive a piezoelectric signal generated by the piezoelectric element 33 and form an ultrasonic image of an object to be detected according to the received electrical signal.
It can be seen from the above that the multiple pixel electrodes 32, the piezoelectric element 33, the electrode layer 34, the ACF 35, the flexible circuit board 37, and the fingerprint chip 36 constitute a closed loop of the ultrasonic fingerprint module 30. In this way, the ultrasonic fingerprint module 30 can collect fingerprints as follows.
When a user places a finger on the display screen 20, the fingerprint chip 36 outputs an electrical signal. The electrical signal is transmitted to the piezoelectric element 33 through the electrode layer 34 and the multiple pixel electrodes 32. The piezoelectric element 33 generates the ultrasonic waves upon application of the electrical signal. After the ultrasonic wave penetrates the display screen 20, it propagates to the finger of the user and is reflected by the finger with fingerprints. At this time, the piezoelectric element 33 converts the received ultrasonic waves into an electrical signal, and transmits the electrical signal to the fingerprint chip 36 through the electrode layer 34 and the multiple pixel electrodes 32. Finally, after the fingerprint chip 36 receives the electric signal, the user's fingerprint can be recognized according to the received electric signal. Locations of a fingerprint ridge and a fingerprint valley can be distinguished due to a difference in acoustic impedance caused by skin and air. In this way, according to a difference between the reflected ultrasonic waves, the user's fingerprint can be collected.
In an example, as illustrated in
As illustrated in
In this implementation, a first pin 374 of the flexible circuit board 37 is electrically connected with the extension part 342, so that the flexible circuit board 37 and the electrode layer 34 are partially overlapped in a thickness direction of the ultrasonic fingerprint module 30, thereby reducing a thickness of the ultrasonic fingerprint module 30 and facilitating a thinning of the ultrasonic fingerprint module 30.
In addition, because the thickness of the body part 341 in the first direction is greater than that of the extension part 342 in the first direction, when the first portion 351 is disposed on the extension part 342, a probability that the conductive particles in the ACF 35 are not easily crushed by the pressing head due to being trapped in the first portion 351 can be reduced with the extension part 342.
In an implementation, the thickness of the first portion 351 in the first direction is greater than or equal to that of the extension part 342 in the first direction.
Because the thickness of the first portion 351 in the first direction is greater than or equal to the thickness of the extension part 342 in the first direction, during bonding of the first pin 374 to the first portion 351, the conductive particles of the ACF 35 will be easily crushed by the pressing head because the conductive particles are not likely to be trapped in the first portion 351, thereby ensuring the electrical connection stability between the flexible circuit board 37 and the electrode layer 34, and further ensuring the excellent connection reliability of the ultrasonic fingerprint module 30.
As illustrated in
The substrate 373 can be, but is not limited to, of polymethyl methacrylate (PMMA).
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In this implementation, by defining the accommodation space 3742 in the first pin 374, part of the ACF 35 can be filled into the accommodation space 3742 during bonding of the first pin 374 to the electrode layer 34. In this way, the ACF 35 formed between the first connection surface 3741 and the electrode layer 34 has a small thickness, thus ensuring that conductive particles in the ACF 35 can be electrically connected with both the first pin 374 and the electrode layer 34 at the same time, and further ensuring the electrical connection stability between the first pin 374 and the first portion 351.
In addition, when the ACF 35 between the first connection surface 3741 and the electrode layer 34 has a small thickness, no gap will be generated between the flexible circuit board 37 and the electrode layer 34, thus ensuring that no external water vapor or air will enter this gap.
In addition, by defining the accommodation space 3742 in the first pin 374, a contact area between the first pin 374 and the first portion 351 is increased, so that the electrical connection stability between the first pin 374 and the first portion 351 is improved.
Reference can be made to
Reference can be made to
In an implementation, the accommodation space 3742 has a planar groove side wall. The groove side wall has an included angle relative to the first connection surface 3741. The included angle is greater than 90°. In this way, compared with an included angle being equal to 90°, in this implementation, the included angle is set to be greater than 90° so that a surface area of the groove side wall of the accommodation space 3742 is larger. Therefore, on one hand, during bonding of the first pin 374 to the electrode layer 34, more ACF 35 can be accommodated in the accommodation space 3742, thereby reducing the thickness of the ACF 35 disposed between the first connection surface 3741 and the electrode layer 34, and on the other hand, the contact area between the first pin 374 and the first portion 351 is increased, thereby improving the electrical connection stability between the first pin 374 and the first portion 351.
In addition, compared with an included angle being less than or equal to 90°, in this implementation, by setting the included angle being greater than 90°, a process difficulty in preparing the accommodation space 3742 at the first pin 374 can be reduced.
In an implementation, the accommodation space 3742 has a cambered groove side wall, and the cambered groove side wall is concave in a direction away from a center of the accommodation space 3742. In this way, the surface area of the groove side wall of the accommodation space 3742 is larger. Therefore, on one hand, during bonding of the first pin 374 of the flexible circuit board 37 to the electrode layer 34, more ACF 35 can be accommodated in the accommodation space 3742, thereby reducing the thickness of the ACF 35 disposed between the first connection surface 3741 and the electrode layer 34, and on the other hand, the contact area between the first pin 374 and the first portion 351 is increased, thereby improving the electrical connection stability between the first pin 374 and the first portion 351.
In an implementation, reference can be made to
Reference can be made to
In this implementation, the conductive part 344 is disposed on the first surface 311, and the first pin 374 of the flexible circuit board 37 is electrically connected with the conductive part 344, so that the flexible circuit board 37, the electrode layer 34 and the piezoelectric element 33 are partially overlapped in a thickness direction of the ultrasonic fingerprint module 30, thereby reducing a thickness of the ultrasonic fingerprint module 30 and facilitating a thinning of the ultrasonic fingerprint module.
In an implementation, the thickness of the first portion 351 in the first direction is greater than or equal to that of the conductive part 344 in the first direction. The first direction is a direction directed from the base plate 31 to the piezoelectric element 33.
It can be understood that because the thickness of the first portion 351 in the first direction is greater than or equal to the thickness of the conductive part 344 in the first direction, during bonding of the first pin 374 to the first portion 344, the conductive particles of the ACF 35 will be easily crushed by the pressing head because the conductive particles are not likely to be trapped in the conductive part 344, thereby ensuring the electrical connection stability between the flexible circuit board 37 and the electrode layer 34, and further ensuring the excellent connection reliability of the ultrasonic fingerprint module 30.
While the disclosure has been described in connection with certain implementations, it is to be understood that the disclosure is not to be limited to the disclosed implementations but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.
Number | Date | Country | Kind |
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201921126123.4 | Jul 2019 | CN | national |
This application is a continuation of International Application No. PCT/CN2019/112610, filed on Oct. 22, 2019, which claims priority to and the benefit of Chinese Patent application No. 201921126123.4, Jul. 17, 2019, the entire disclosures of which are hereby incorporated by reference.
Number | Date | Country | |
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Parent | PCT/CN2019/112610 | Oct 2019 | US |
Child | 17205327 | US |