CN107301988B - Camera module and assembly method thereof - Google Patents

Abstract

The invention provides an assembly method of a camera module, which comprises the following steps: providing an image sensor chip with a suspended metal wire, wherein a first end of the metal wire is bonded to a bonding pad of the image sensor chip, and a second end of the metal wire is suspended in the image sensor chip; assembling the image sensor chip and a supporting frame provided with a light-transmitting window into a packaging piece, wherein the image sensor chip, the light-transmitting window and the supporting frame in the packaging piece form a cavity, so that the pollution of external foreign matters to the image sensor chip is reduced; and then assembling the packaging piece, the circuit board and the lens module through the second end of the metal wire to form the camera module.

Description

Camera module and assembly method thereof

technical field

The invention relates to the field of semiconductor manufacturing, in particular to an assembly method of a camera module.

Background technique

Currently, mainstream image sensor (CIS: CMOS Image Sensor) packaging methods include: Chip Scale Package (CSP), Chip On Board (COB) and Flip Chip Package (FlipChip, FC) .

CIS CSP is a packaging technology commonly used in low-end, low-pixel (2M pixels or below) image sensors at present, and can adopt Die level (chip level) or Wafer level (wafer level) packaging technology. This packaging technology usually uses wafer-level glass and wafer bonding and uses cofferdams to separate the image sensor chips of the wafer, and then makes pad surface or pad in-plane holes in the pad area of the polished wafer. The through-silicon via technology (TSV: Through Silicon Via) connected by the side ring metal or the T-shaped metal contact chip size packaging technology on the side of the pad after cutting, and the solder ball grid array (BGA: Ball Grid Array) is made after extending the circuit on the back of the wafer. ), and then cut to form a single sealed cavity image sensor unit. The back end forms a module assembly structure through the SMT method. However, CSP packaging has the following obvious problems: 1. It affects product performance: the absorption, refraction, reflection and scattering of light by thick support glass have a great impact on the performance of image sensors, especially products with small pixel sizes; 2. Reliability issues : The thermal expansion coefficient difference between the components in the package structure and the sealing gas in the cavity have reliability problems in the subsequent SMT process or changes in the product use environment; 3 Large investment scale, large environmental pollution control requirements, and long production cycle , the unit chip cost is relatively high, especially for high-pixel and large-size image sensor products.

CIS COB packaging is a Die Level (chip-level) packaging technology commonly used in high-end, high-pixel product (5M pixels or above) image sensors. This packaging technology bonds the back of the chip after grinding and cutting to the pad of the PCB board using a bonding metal wire, and installs a bracket with an IR glass sheet and a lens to form an assembled module structure. However, COB packaging has the following obvious problems: 1. Dust control is very difficult, requiring ultra-high clean room levels, and manufacturing maintenance costs are high; 2. Product design is customized, the cycle is long, and the flexibility is not enough; 3. It is not easy to scale production ;

CIS FC packaging is the Die Level (chip-level) packaging technology of the recently emerging high-end, high-pixel (5M pixels or above) image sensor. This packaging technology connects the chip pads that have been ground and cut with gold bumps on the pads directly to the pads of the PCB through the action of thermosonic to connect all the contact bumps and pads at one time to form a packaging structure. The rear end uses the SMT method to form a module assembly structure through the solder pads or solder balls on the outside of the PCB. However, the FC package has the following obvious problems: 1. The package has high requirements on the PCB substrate, and has a similar thermal expansion coefficient to Si, and the cost is very high; 2. Manufacturing reliability is very difficult, and the connection between all the bumps and pads of the thermosonic is consistent. Very high performance requirements, bumps and pads are hard-connected, and the ductility is not good; 3. The dust control is difficult, the process environment requirements are high, and the cost is high;

In addition, the assembly method of the previous CIS module is:

Step 1, solder the image sensor chip to the circuit board to form the first component;

Step 2, assemble the lens module and the sleeve module to form the second part;

Step 3, assemble the first part and the second part to form a complete camera module.

This method of assembling the camera module has the following disadvantages: For the camera module, it is necessary to use high-precision installation equipment to carry out the precise installation of the above step 3, otherwise it will affect the imaging effect of the camera module, and then assembled The qualified rate of finished products of camera modules is not high; especially for high-pixel camera modules, it is difficult to complete the precise installation of the above step 3 with ordinary installation equipment, so that the imaging effect of high-pixel camera modules is affected. If the impact is large, the imaging quality of the formed image is poor, especially the imaging quality around the image is obviously not good.

Moreover, in the image sensor chip packaging process using metal wire bonding, the image sensor chip is usually first bonded (such as adhered) to the adapter board (flexible circuit board), and then bonded to the wire, the metal wire The first end of the image sensor chip is connected to the pad of the image sensor chip, and the second end is connected to the adapter board, thereby realizing the electrical connection between the image sensor chip and the adapter board, and then the packaged image sensor chip is passed through the adapter board. The leads or solder balls on the board connect to the circuit board.

The existing wire bonding method is likely to cause poor structural flexibility after packaging, and the subsequent assembly precision of the camera module is high, and the relative position of the lens and the image sensor chip is difficult to control, which affects the performance of the camera module; The process is long and the packaging efficiency is low, resulting in the image sensor chip being exposed to the air for a long time, requiring multiple inspections and cleanings, reducing the yield rate, and increasing the cost of the camera module. In particular, for some image sensor chips whose second ends of metal wires are connected by other processes, a new bonding method and device are needed so that the first ends of the wires are connected to the pads of the image sensor chips, and the second ends Suspended outside the image sensor chip.

To sum up, there is an urgent need for a low-cost, high-performance, high-reliability, and ultra-thin packaging structure technology for realizing high-pixel, large-chip-size image sensors.

Contents of the invention

Based on the above considerations, a camera module assembly method is proposed, including the following steps:

providing an image sensor chip with suspended metal wires, the first end of the metal wire is bonded to the pad of the image sensor chip, and the second end is suspended from the image sensor chip;

Assembling the image sensor chip and a support frame provided with a light-transmitting window into a package, in which the image sensor chip, the light-transmitting window and the support frame form a cavity to reduce contamination of the image sensor chip by external foreign matter; then The package is assembled with a circuit board and a lens module through the second end of the metal wire to form a camera module.

Preferably, the metal wire forms an elastic structure, and the second end of the metal wire is 5 microns to 300 microns lower than the lower surface of the image sensor chip.

Preferably, during the electrical testing process of the package, the elastic structure of the metal wire is elastically deformed to provide contact pressure and improve the electrical connection performance between the metal wire and the test device; during the electrical connection between the package and the circuit board During the assembly process, the elastic structure of the metal wire is elastically deformed to provide contact pressure and improve the electrical connection performance between the metal wire and the circuit board.

Preferably, the second end of the metal wire is electrically connected to the circuit board by means of welding, press-fit contact, ultrasonic bonding, or conductive adhesive bonding.

Preferably, during the assembly process of the package and the circuit board,

When the cavity of the package is sealed, by controlling the value of P/(273+t) to change within a certain range, the air pressure difference between the inside of the cavity and the outside of the cavity is less than 20%, where P is The external pressure of the cavity, t is the temperature in Celsius outside the cavity, so as to reduce the damage to the package due to the pressure difference between the inside and outside of the cavity during the assembly process;

When the cavity of the package is unsealed, by controlling the value of P/(273+t) to change within a certain range, the air pressure difference between the inside of the cavity and the outside of the cavity is less than 20%, where P is the external pressure of the cavity, and t is the Celsius temperature outside the cavity, which reduces the air flow inside and outside the cavity, thereby reducing the contamination of the chip by external foreign matter during the assembly process.

The present invention also provides a camera module, including:

An image sensor chip, the image sensor chip is electrically connected to a suspended metal wire, the first end of the metal wire is bonded to the pad of the image sensor chip, and the second end is suspended to the image sensor chip;

The supporting frame is provided with a light-transmitting window, and is suitable for assembling with the image sensor chip into a package;

The lens module is suitable for being assembled in the support frame in the package and assembled with the circuit board to form a camera module;

A circuit board, the circuit board is electrically connected to the package through the second end of the metal wire.

Preferably, the metal wire forms an elastic structure and the second end of the metal wire is 5 microns to 300 microns lower than the lower surface of the image sensor chip.

Preferably, the second end of the metal wire is electrically connected to the circuit board through welding, press-fit contact, ultrasonic bonding, or conductive adhesive bonding

The assembly method of the camera module of the present invention can accurately assemble the camera module using ordinary installation equipment, which overcomes the deficiency that the assembly method of the camera module in the prior art needs to adopt high-precision installation equipment. The assembly method is simple, easy to adjust the focal plane from the image sensor chip to the lens, and easy to correct the inclination of the lens and the image sensor chip, so as to ensure the optical performance of the camera module after assembly. The assembly steps of the present invention make the camera module The group has high-quality imaging effects, especially for high-pixel camera modules, which can significantly improve the imaging quality around the image.

In the present invention, the chip of the image sensor is cut to form a suspended metal wire by bonding the metal wire, and the lens module is further assembled on the image sensor chip, and then electrically connected to the circuit board through the suspended end of the metal wire, and the metal The wire is an elastic structure, which can undergo elastic deformation and can better improve the electrical performance. Compared with the traditional CSP pad, BGA and solder SMT connection, it has more technological advantages

The invention uses the gold wire to directly connect the chip and the pad of the PCB substrate, and the gold wire has good ductility, strong environmental adaptability and good reliability. The supporting frame of the present invention can form an open structure with the image sensor chip, effectively reducing the stray light of light in the camera module, and improving the performance of the module. .

Various aspects of the present invention will be clarified through the description of specific embodiments below.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

1 is a schematic diagram of an image sensor chip with suspended metal wires according to an embodiment of the present invention;

2 is a schematic diagram of a package according to an embodiment of the present invention;

3 is a schematic diagram of an initial assembly state of a camera module according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an assembled state of a camera module according to an embodiment of the present invention;

FIG. 5 is a flowchart of an assembly method of a camera module according to the present invention.

In the drawings, the same or similar reference numerals denote the same or similar means (modules) or steps throughout different views.

Detailed ways

In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof. The accompanying drawings show, by way of example, specific embodiments in which the invention can be practiced. The illustrated embodiments are not intended to be exhaustive of all embodiments in accordance with the invention. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Accordingly, the following detailed description is not limiting, and the scope of the invention is defined by the appended claims.

In order to illustrate the packaging method of the present invention more clearly, in the following embodiments, glass is used as the substrate. Those skilled in the art can understand that the substrate can also be made of other transparent materials.

Fig. 1 is a schematic diagram of an image sensor chip with suspended metal wires according to an embodiment of the present invention; Fig. 2 is a schematic diagram of a package according to an embodiment of the present invention; Fig. 3 is an initial assembly state of a camera module according to an embodiment of the present invention Schematic diagram; FIG. 4 is a schematic diagram of an assembled state of a camera module according to an embodiment of the present invention; FIG. 5 is a flowchart of an assembly method of a camera module according to an embodiment of the present invention.

As shown in Figure 5, please also refer to Figure 1 to Figure 4. The packaging method includes the following steps:

First, step S11 is performed: providing an image sensor chip 110 with a suspended metal wire 120, the first end 121 of the metal wire 120 is bonded to the pad 111 of the image sensor chip 110, and the second end 122 is suspended from the Image sensor chip 110 .

In this step, the front surface of the image sensor chip 110 has an image sensing area 112 and a bonding pad area 113 surrounding the image sensing area 112 . The bonding pad area 113 includes a plurality of bonding pads 111 . In this step, the second end of the metal wire 120 is suspended in the air and is not bonded to any medium. The metal wire is gold wire, silver wire, copper wire, etc., which have good wire performance and are of an elastic structure. When the force is applied to the second end 122 Can undergo elastic deformation;

Please refer to FIG. 2 to FIG. 4 at the same time, step S12: assemble the image sensor chip 110 and the support frame 131 provided with the light-transmitting window 133 into a package 200, the image sensor chip 110, the light-transmitting window in the package 200 133 and the support frame 131 to form a cavity 134 to reduce the contamination of the image sensor chip 110 by external foreign objects; Group.

In this step, the image sensor chip 110 with suspended metal wires is assembled with the support frame 131. In one embodiment, the inner surface of the support frame 131 also has a step 1311, which is suitable for assembling a packaging substrate 140. The packaging substrate 140 is Made of glass or plastic, the surface of the packaging substrate 140 is covered with an IR film or an AR film; in another embodiment, the step 1311 and the packaging substrate 140 are not provided, and the surface of the lens module 130 close to the image sensing area 112 is directly covered with an IR film or AR film. AR film.

After the assembly of the image sensor chip 110 and the supporting frame 131 is completed, the package 200 and the circuit board 300, The lens module 130 is assembled to form the camera module 400. It should be noted that the lens module 130 is assembled on the support frame 131 corresponding to the area of the light-transmitting window. The order of assembly can be electrically connected to the circuit board 300 at the second end 122 of the metal wire Before the bonding pad 310 of the circuit board 300 , it may also be after the second end 122 of the metal wire is electrically connected to the bonding pad 310 of the circuit board 300 .

During the assembly process of the package and the circuit board, when the cavity of the package is sealed, by controlling the value of P/(273+t) to change within a certain range, the inside of the cavity, the cavity The air pressure difference outside the body is less than 20%, where P is the external pressure of the cavity, and t is the Celsius temperature outside the cavity, so as to reduce the damage to the package due to the air pressure difference inside and outside the cavity during the assembly process; when the cavity of the package When the body is non-sealed, by controlling the value of P/(273+t) to change within a certain range, the air pressure difference between the inside of the cavity and the outside of the cavity is less than 20%, where P is the external pressure of the cavity, t is the temperature in Celsius outside the cavity, which reduces the air flow inside and outside the cavity, thereby reducing the contamination of the chip by external foreign objects during the assembly process.

Specifically, in the first embodiment, the press-fit contact method is used to make good contact with the pad 310 on the circuit board 300 through the second end 122, and the package 200 is connected to a part of the circuit board 300 by snapping or bonding. fixed.

In the second embodiment, the welding method is adopted, and the specific method is: a layer of gold-tin alloy welding layer is plated on the second end 122 of the metal wire or the pad 310 of the circuit board 300, and the welding area is controlled by local rapid welding. Heat conduction so as not to affect the performance of lens components;

(1) Pad gold-plated tin alloy method: S201 provides a camera module, the camera module includes a temperature-sensitive lens, and the camera module also includes a metal wire electrically connected to the image sensor chip with one end suspended; S203 providing a circuit board with several pads; S205 pre-attaching a solder layer to the pads of the circuit board, and quickly welding the floating ends of the metal wires to the pads of the circuit board. The metal wire is a gold wire, the diameter of the gold wire is greater than or equal to 10 microns, and the solder layer is a tin layer. By controlling the thickness of the tin layer, the gold wire and the tin layer can form a stable gold content in the subsequent rapid local welding. gold-tin alloy solder layer. In another embodiment, the step of pre-attaching the solder layer to the pads of the circuit board further includes: S206 using a printing process to attach solder to the pads of the circuit board, and reflow soldering to form the solder layer. In another embodiment, the step of pre-attaching the solder layer to the pad of the circuit board further includes: S206' attaching the solder layer to the pad of the circuit board by using a wave soldering process. In one embodiment, the method for controlling the thickness of the tin layer includes: controlling the parameters of the wave soldering process so that the thickness of the tin layer is smaller than the diameter of the gold wire. In another embodiment, the method for controlling the thickness of the tin layer includes: using a printing process to attach solder paste on the pad of the circuit board, reflow soldering to form the tin layer, and adopting air knife method, suction gun suction method or welding head adhesion The method makes the thickness of the tin layer less than the thickness of the tin layer. The thickness of the tin layer is smaller than the thickness of the gold wire. The gold-tin alloy has good material advantages during the welding process, can reduce crystal brittleness, has the characteristics of good fluidity, low resistivity, and good thermal conductivity. Fast welding includes: pulse hot-press welding process, laser welding process, ultrasonic hot-press welding process, and fast welding is a local welding method, and the heating range is less than 1/2 of the bottom area of the camera module.

(2) The second end 122 of the metal wire is plated with gold-tin alloy. S101 provides a camera module. The camera module includes a temperature-sensitive lens. The camera module also includes an electrical connection with the image sensor chip S103 provides a circuit board with several pads; S105 pre-attaches a solder layer to the dangling ends of the metal wires, and quickly welds the dangling ends of the metal wires to the pads of the circuit board. The metal wire is a gold wire, the diameter of the gold wire is greater than or equal to 10 microns, and the solder layer is a tin layer. By controlling the thickness of the tin layer, the gold wire and the tin layer can form a stable gold content in the subsequent rapid local welding. (Gold-rich) gold-tin alloy welding layer, in which the thickness of the tin layer is less than the thickness of the gold wire, the gold-tin alloy has good material advantages during the welding process, can reduce crystal brittleness, has good fluidity, low resistivity, and thermal conductivity Sexual characteristics. Fast welding includes: pulse hot-press welding process, laser welding process, ultrasonic hot-press welding process, and fast welding is a local welding method, and the heating range is less than 1/2 of the bottom area of the camera module.

In the third embodiment, the conductive adhesive bonding method is adopted, and the specific suspended end of the metal wire is pre-attached with conductive adhesive. In this embodiment, the conductive adhesive is tin glue, and the suspended end of the metal wire and the pad of the circuit board are cured. Make electrical connections. Because tin glue has good adhesion and conductivity, it can be used as point electrode paste, and it still has good performance after curing according to controllable conditions. The metal wire is a gold wire, the diameter of the gold wire is greater than or equal to 5 microns, and the thickness of the tin glue is 2 microns to 100 microns. The curing method adopts thermal curing or UV curing. The composition of the tin glue in this embodiment is: a mixture of epoxy resin glue or UV glue, and tiny silver flakes, and the thickness of the tin glue is: 2 microns to 100 microns. In addition, it is also possible to use: the pads of the circuit board are pre-attached with tin glue, and the floating ends of the metal wires are cured and electrically connected to the pads of the circuit board. Because tin glue has good adhesion and conductivity, it can be used as point electrode paste, and it still has good performance after curing according to controllable conditions. The metal wire is a gold wire, the diameter of the gold wire is greater than or equal to 5 microns, and the thickness of the tin glue is 2 microns to 100 microns. The curing method adopts thermal curing or UV curing. The composition of the tin glue in this embodiment is: a mixture of epoxy resin glue or UV glue, and tiny silver flakes, and the thickness of the tin glue is: 2 microns to 100 microns. The conductive adhesive in this embodiment can also use other metal materials with conductive properties.

After the package 200 is formed, the package 200 can also be tested. During the electrical test of the package 200, the elastic structure of the metal wire 120 is elastically deformed to provide contact pressure. The two ends 122 are 5 microns to 300 microns lower than the lower surface of the image sensor chip 110 (please refer to FIG. 1, the distance is h), so as to improve the connection performance between the metal wire 120 and the test device (not marked); and in the package 200 and the circuit board 300 during the assembly process, the elastic structure of the metal wire 120 is elastically deformed to provide contact pressure, because the second end 122 of the metal wire is lower than the lower surface of the image sensor chip 110 by 5 microns to 300 microns ( Please refer to Figure 1, the distance is h), which can improve the connection performance between the metal wire and the circuit board. Please refer to FIG. 4. What the dotted line 120' in FIG. 4 shows is the first shape state of the metal wire 120 when the package 200 is not assembled with the circuit board 300; the solid line 120'' shows that the package 200 is assembled with the circuit board 300 After completion, the second shape state of the metal wire, at this time, the second shape state of the metal wire is elastically deformed, and the contact between the second end of the metal wire and the pad is better, which is conducive to signal transmission. The contact area with the pad is greater than or equal to 0.01 square millimeters.

The present invention also provides a camera module, which is characterized in that it includes: an image sensor chip, the image sensor chip is electrically connected with a suspended metal wire, and the first end of the metal wire is bonded to the image sensor chip. The pad, the second end is suspended from the image sensor chip; the supporting frame is provided with a light-transmitting window, and is suitable for being assembled into a package with the image sensor chip; the lens module is suitable for being assembled in the supporting frame in the package and is connected with the The circuit board is assembled into a camera module; the circuit board is electrically connected to the package through the second end of the metal wire. The metal wire forms an elastic structure, and the second end of the metal wire is 5 microns to 300 microns lower than the lower surface of the image sensor chip. The second end of the metal wire is connected to the circuit board by pressing contact, quick soldering, conductive adhesive bonding or non-conductive adhesive bonding. It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all respects as exemplary and not restrictive. Furthermore, it is obvious that the word "comprising" does not exclude other elements and steps, and the word "a" does not exclude the plural. A plurality of elements recited in device claims may also be embodied by one element. The words first, second, etc. are used to denote names and do not imply any particular order.

Claims (7)

1. The assembly method of the camera module is characterized by comprising the following steps of:

providing an image sensor chip with a suspended metal wire, wherein a first end of the metal wire is bonded to a bonding pad of the image sensor chip, and a second end of the metal wire is suspended in the image sensor chip;

assembling the image sensor chip and a supporting frame provided with a light-transmitting window into a packaging piece, wherein the image sensor chip, the light-transmitting window and the supporting frame in the packaging piece form a cavity, so that the pollution of external foreign matters to the image sensor chip is reduced; then assembling the packaging piece, the circuit board and the lens module through the second end of the metal wire to form a camera module;

during assembly of the package with the circuit board,

when the cavity of the packaging piece is sealed, the pressure difference between the inside and the outside of the cavity is smaller than 20% by controlling the value of P/(273+t) to change within a certain range, wherein P is the external pressure of the cavity, and t is the temperature of the outside of the cavity, so that the damage of the pressure difference between the inside and the outside of the cavity to the packaging piece in the assembly process is reduced;

when the cavity of the packaging part is unsealed, the value of P/(273+t) is controlled to be changed within a certain range, so that the air pressure difference between the inside of the cavity and the outside of the cavity is smaller than 20%, wherein P is the outside pressure of the cavity, and t is the temperature of the outside of the cavity, the flow of air flow in and out of the cavity is reduced, and the contamination of the chip by external foreign matters in the assembly process is reduced.

2. The method of assembling a camera module of claim 1, wherein the metal wire forms an elastic structure and the second end of the metal wire is 5 to 300 microns below the lower surface of the image sensor chip.

3. The method for assembling a camera module according to claim 2, wherein during the electrical testing of the package, the elastic structure of the metal wire is elastically deformed to provide a contact pressure, so as to improve the electrical connection performance between the metal wire and the testing device; in the assembly process of the packaging piece and the circuit board, the elastic structure of the metal wire is elastically deformed to provide contact pressure, so that the electrical connection performance of the metal wire and the circuit board is improved.

4. The method of assembling a camera module of claim 1, wherein the second end of the metal wire is electrically connected to the circuit board by soldering, press-contact, ultrasonic bonding, or conductive adhesive.

5. A camera module, comprising:

the image sensor chip is electrically connected with a suspended metal wire, a first end of the metal wire is bonded with a bonding pad of the image sensor chip, and a second end of the metal wire is suspended in the image sensor chip;

the support frame is provided with a light-transmitting window and is suitable for being assembled with the image sensor chip to form a package;

the lens module is suitable for being assembled in the supporting frame in the packaging piece;

the circuit board is electrically connected with the packaging piece through the second end of the metal wire;

when the cavity of the packaging piece is sealed, the value of P/(273+t) is controlled to be changed within a certain range in the assembly process, so that the air pressure difference between the inside and the outside of the cavity is smaller than 20%, wherein P is the external pressure of the cavity, and t is the temperature of the outside of the cavity, so that the damage of the air pressure difference between the inside and the outside of the cavity to the packaging piece in the assembly process is reduced;

when the cavity of the packaging piece is unsealed, the value P/(273+t) is controlled to change within a certain range in the assembly process, so that the air pressure difference between the inside of the cavity and the outside of the cavity is smaller than 20%, wherein P is the outside pressure of the cavity, and t is the temperature outside the cavity, so that the flow of air flow inside and outside the cavity is reduced, and the contamination of external foreign matters on chips in the assembly process is reduced.

6. The camera module of claim 5, wherein the metal wire forms a spring structure and the second end of the metal wire is 5 microns to 300 microns below the lower surface of the image sensor chip.

7. The camera module of claim 5, wherein the second end of the metal wire is electrically connected to the circuit board by soldering, press contact, ultrasonic bonding, or conductive adhesive.

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