CN105633108B - Multi-camera module and assembly method thereof - Google Patents

Abstract

The present invention provides an assembly method for a multi-camera module, comprising: providing a plurality of image sensor chips with suspended metal wires, wherein the first ends of the metal wires are bonded to pads of the image sensor chips, and the second ends are suspended from the image sensor chips; providing a lens barrel frame, wherein the lens barrel frame is an integral body suitable for assembling a plurality of lens modules and a plurality of image sensor chips; assembling the plurality of image sensor chips with the lens barrel frame to form a standard part, and then assembling the standard part with a circuit board through the second ends of the metal wires to form a multi-camera module.

Description

Multi-camera module and assembly method thereof

Technical Field

The present invention relates to the field of semiconductor manufacturing, and in particular to an assembling method of a multi-camera module.

Background technique

At present, the mainstream packaging methods of image sensors (CIS: CMOS Image Sensor) include: chip scale package (CSP), chip on board (COB) and flip chip (FC).

CIS CSP is a packaging technology currently widely used in low-end and low-pixel (2M pixels or less) image sensors. It can be packaged using die level or wafer level packaging technology. This packaging technology usually uses wafer-level glass and wafer bonding and uses a cofferdam to separate the image sensor chips on the wafer. Then, in the pad area of the polished wafer, a silicon through-hole technology (TSV: Through Silicon Via) is used to make a metal connection on the pad surface or the side of the hole inside the pad surface, or a T-shaped metal contact chip size packaging technology on the side of the pad after cutting. After extending the line on the back of the wafer, a ball grid array (BGA: Ball Grid Array) is made, and then a single sealed cavity image sensor unit is formed after cutting. The module assembly structure is formed by the SMT method at the back end. However, CSP packaging has the following obvious problems: 1. Impact on product performance: The absorption, refraction, reflection and scattering of light by thick supporting glass has a great impact on the performance of image sensors, especially those with small pixel sizes; 2. Reliability issues: The difference in thermal expansion coefficients between components in the packaging structure and the sealed gas in the cavity will cause reliability problems in the subsequent SMT process or changes in the product use environment; 3. Large investment scale, high environmental pollution control requirements, long production cycle, and high unit chip cost, especially for high-pixel and large-size image sensor products.

CIS COB packaging is a die level packaging technology currently widely used in high-end, high-pixel products (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 bonding metal wires, and installs a bracket and lens with IR glass to form an assembled module structure. However, COB packaging has the following obvious problems: 1. It is very difficult to control dust, requiring an ultra-high clean room level and high manufacturing and maintenance costs; 2. The product design is customized, the cycle is long, and the flexibility is insufficient; 3. It is not easy to mass produce;

CIS FC packaging is a recently emerging die-level packaging technology for high-end, high-pixel (5M pixels or above) image sensors. This packaging technology connects the chip pads that have been polished and cut with gold element bumps directly to the pads of the PCB through the action of thermal ultrasound to connect all the contact bumps and pads at once to form a packaging structure. The module assembly structure is formed by the SMT method through the pads or solder balls on the outside of the PCB at the back end. However, the FC packaging has the following obvious problems: 1. This package has very high requirements for the PCB substrate, has a similar thermal expansion coefficient to Si, and is very expensive; 2. Manufacturing reliability is very difficult, and the consistency of the connection between all bumps and pads by thermal ultrasound is very high. The bumps and pads are hard connected and have poor ductility; 3. It is difficult to control dust, the process environment requirements are high, and the cost is very high;

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

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

Step 2, assembling the lens module and the sleeve module to form a second component;

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

This camera module assembly method has the following disadvantages: for the camera module, high-precision installation equipment is required to perform the precise installation of the above step 3, otherwise it will affect the imaging effect of the camera module, and the qualified rate of the assembled camera module is not high; especially for high-pixel camera modules, it is difficult to complete the precise installation of the above step 3 using ordinary installation equipment, which greatly affects the imaging effect of the high-pixel camera module, and the imaging quality of the resulting image is poor, especially the imaging quality around the image is obviously poor.

Furthermore, in the image sensor chip packaging process using metal wire bonding, the image sensor chip is usually first die-bonded (e.g. adhered) to an adapter board (flexible circuit board), and then wire bonding is performed, with the first end of the metal wire connected to the pad of the image sensor chip and the second end connected to the adapter board, thereby achieving electrical connection between the image sensor chip and the adapter board, and then the packaged image sensor chip is connected to the circuit board through the leads or solder balls on the adapter board.

The existing wire bonding method easily results in poor structural flexibility after packaging, high subsequent assembly precision requirements for the camera module, and the relative position of the lens and the image sensor chip is difficult to control, which affects the performance of the camera module; and because the existing method has a long process and low packaging efficiency, the image sensor chip is 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 using other processes, a new bonding method and device is needed to connect the first end of the wire to the pad of the image sensor chip and the second end is suspended outside the image sensor chip.

In addition, with the rapid development of consumer electronic products, single cameras suitable for portable electronic devices have defects in some market segments, and focusing ability and dynamic balance are difficult to meet the needs under certain circumstances. Multi-camera modules have appeared in portable electronic devices, and multi-camera modules have been used in the main cameras of smartphones. However, in the assembly of multi-camera modules, the photosensitive surface of the image sensor chip is not aligned, and there are problems with height and deviation angles, which will bring unsolvable problems in the subsequent imaging process.

In summary, a new assembly method for multi-camera modules is a topic that the industry urgently needs to find.

Summary of the invention

Based on the above considerations, the present invention provides a method for assembling a multi-camera module, comprising:

Providing a plurality of image sensor chips with suspended metal wires, wherein a first end of the metal wire is bonded to a pad of the image sensor chip and a second end is suspended from the image sensor chip;

Providing a lens barrel frame, wherein the lens barrel frame is an integral body suitable for assembling multiple lens modules and multiple image sensor chips;

The plurality of image sensor chips are assembled with the lens barrel frame to form a standard component, and then the standard component is assembled with a circuit board through the second end of the metal wire to form a multi-camera module.

Preferably, the photosensitive surfaces of the plurality of image sensor chips are aligned.

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

Preferably, during the electrical testing of the standard part, the elastic structure of the metal wire undergoes elastic deformation to provide contact pressure, thereby improving the electrical connection performance between the metal wire and the testing device; during the assembly of the standard part and the circuit board, the elastic structure of the metal wire undergoes elastic deformation to provide contact pressure, thereby improving the electrical connection performance between the metal wire and the circuit board.

Preferably, the step of assembling the standard component with the circuit board includes: electrically connecting the second end of the metal wire with the circuit board by pressing contact, quick welding, conductive adhesive bonding or non-conductive adhesive bonding.

The present invention also provides a multi-camera module, characterized in that it comprises:

A plurality of image sensor chips, wherein the image sensor chips are electrically connected to suspended metal wires, wherein a first end of the metal wire is bonded to a pad of the image sensor chip, and a second end of the metal wire is suspended from the image sensor chip;

A lens barrel frame, which is a whole body suitable for assembling multiple lens modules and multiple image sensor chips, and the lens barrel frame and the image sensor chips are assembled to form a standard part; wherein the photosensitive surfaces of the multiple image sensor chips are parallel to each other without an inclination angle;

A circuit board is electrically connected to the standard component through the second end of the metal wire.

Preferably, the photosensitive surfaces of the multiple image sensor chips are aligned.

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

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

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

The present invention forms a suspended metal wire by bonding the chip of the image sensor through a metal wire, and further assembles an integral lens barrel frame with a plurality of image sensor chips, and then electrically connects the suspended end of the metal wire to a circuit board. The metal wire is an elastic structure and can undergo elastic deformation, which can better improve the electrical performance and has a process advantage over the SMT connection of the pad, BGA and solder of the traditional CSP. In addition, the lens barrel frame is an integral body and can be assembled with a plurality of image sensor chips. The photosensitive surfaces of the plurality of image sensor chips are aligned, thereby improving the assembly accuracy of the multi-camera module and the performance of the module.

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

The method for forming a multi-image sensor module can ensure the positioning and assembly accuracy between image sensors, avoid misalignment and angle deviation of the photosensitive surfaces of the image sensors, and avoid degradation of the imaging performance of the multi-image sensor module due to assembly accuracy.

Various aspects of the present invention will become more apparent through the following description of specific embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG1 is a schematic diagram of an image sensor chip with suspended metal wires according to an embodiment of the present invention;

FIG2 is a schematic diagram of a standard component according to an embodiment of the present invention;

FIG3 is a schematic diagram of a camera module according to an embodiment of the present invention;

FIG. 4 is a flow chart of a method for assembling a camera module according to the present invention.

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

Detailed ways

In the following specific description of the preferred embodiments, reference will be made to the attached drawings which constitute a part of the present invention. The attached drawings show by way of example specific embodiments that can implement the present invention. The illustrative embodiments are not intended to be exhaustive of all embodiments according to the present invention. It will be appreciated that other embodiments may be utilized, and structural or logical modifications may also be made without departing from the scope of the present invention. Therefore, the following specific description is not restrictive, and the scope of the present invention is limited by the appended claims.

In order to more clearly illustrate the packaging method of the present invention, glass is used as the substrate in the following embodiments. It is understood by those skilled in the art that the substrate may also be made of other transparent materials.

Figure 1 is a schematic diagram of an image sensor chip with suspended metal wires according to an embodiment of the present invention; Figure 2 is a schematic diagram of a standard part according to an embodiment of the present invention; Figure 3 is a schematic diagram of a camera module according to an embodiment of the present invention; Figure 4 is a flow chart of an assembly method of a camera module according to an embodiment of the present invention.

As shown in FIG. 4 , and also referring to FIG. 1 to FIG. 3 , the packaging method includes the following steps:

S10: providing a plurality of image sensor chips 110 having suspended metal wires 120, wherein a first end 121 of the metal wire 120 is bonded to a pad 111 of the image sensor chip 110, and a second end 122 is suspended from the image sensor chip 110;

In this step, the front side of the image sensor chip 110 has an image sensing area 112 and a pad area 113 surrounding the image sensing area 112, and the pad area 113 includes a plurality of pads 111. In this step, the second end of the metal wire 120 is suspended without being bonded to any medium, and the metal wire is a gold wire, a silver wire, a copper wire, etc., which has good wire performance and is an elastic structure, and can be elastically deformed when a force is applied to the second end 122;

Please refer to FIG. 2 , step S20 : providing a lens barrel frame 131 , wherein the lens barrel frame 131 is a whole body suitable for assembling a plurality of lens modules 132 and a plurality of image sensor chips 110 ;

Step S30 : assembling the plurality of image sensor chips 110 , the lens barrel frame 131 , and the lens module 132 to form a standard component 200 , and then assembling the standard component 200 and the circuit board 300 through the second end of the metal wire 120 to form a camera module 400 .

In this step, the image sensor chip 110 with suspended metal wires and the lens barrel frame 131 (mounting frame) and the lens module 132 located inside the lens barrel frame, in one embodiment, the inner surface of the lens barrel frame 131 also has a step 1311, the step 1311 is arranged corresponding to the end of the lens 132 facing the image sensor chip 110, and is suitable for assembling a packaging substrate 140, the packaging substrate 140 is made of glass or plastic, and 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 arranged, and the surface of the lens 132 close to the image sensing area 112 is directly covered with an IR film or an AR film.

After the standard component 200 is assembled, the standard component 200 and the circuit board 300 are assembled to form the camera module 400 by pressing and contacting the second end 122 of the metal wire, by quick welding, by conductive adhesive bonding or by non-conductive adhesive bonding.

Specifically, in the first embodiment, the press-fit contact method is adopted, and the second end 122 is in good contact with the pad 310 on the circuit board 300, and the standard component 200 is fixed to a partial area of the circuit board 300 by snapping or bonding.

In the second embodiment, a rapid welding method is adopted, specifically, a 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 heat conduction in the welding area is controlled by local rapid welding so as not to affect the performance of the lens component;

(I) Pad gold-tin alloy plating method: S201 provides a camera module, the camera module includes a temperature-sensitive lens, and the camera module also includes a metal wire with one end suspended and electrically connected to the image sensor chip; S203 provides a circuit board with a plurality of pads; S205 pre-attaches a solder layer to the pad of the circuit board, and quickly welds the suspended end of the metal wire to the pad 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-tin alloy welding layer with a high gold content in the subsequent rapid local welding. In another embodiment: the step of pre-attaching the solder layer to the pad of the circuit board also includes: S206 using a printing process to attach solder to the pad of the circuit board, and reflow soldering to form a solder layer. In another embodiment, the step of pre-attaching the solder layer to the pad of the circuit board also includes: S206' using a wave soldering process to attach the solder layer to the pad of the circuit board. 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 less 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 to the pad of the circuit board, reflow soldering to form a tin layer, and using a wind knife method, a suction gun suction method or a welding head adhesion method to make the thickness of the tin layer less than the thickness. 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, and has the characteristics of good fluidity, low resistivity, and good thermal conductivity. Rapid welding includes: pulse hot pressing welding process, laser welding process, ultrasonic hot pressing welding process, and rapid welding is a local welding method, and the heating range is less than 1/2 of the bottom area of the camera module.

(II) 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, and the camera module also includes a metal wire with one end suspended and electrically connected to the image sensor chip; S103 provides a circuit board with a plurality of pads; S105 pre-attaches a solder layer to the suspended end of the metal wire, and quickly welds the suspended end of the metal wire to the pad 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, in the subsequent rapid local welding, the gold wire and the tin layer can form a stable gold-tin alloy welding layer with a high gold content (rich in gold), wherein the thickness of the tin layer is less than the thickness of the gold wire. In the welding process, the gold-tin alloy has good material advantages, can reduce crystal brittleness, has good fluidity, low resistivity, and good thermal conductivity. Rapid welding includes: pulse hot pressing welding process, laser welding process, ultrasonic hot pressing welding process, and rapid 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, a conductive adhesive bonding method is adopted. The suspended end of the specific metal wire is pre-attached with conductive adhesive. In this embodiment, the conductive adhesive is silver paste. The suspended end of the metal wire is cured and electrically connected to the pad of the circuit board. Since the silver paste has good adhesion and conductivity, it can be used as a point electrode paste. After curing, it still has good performance according to controllable. 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 silver paste is 2 microns to 100 microns. The curing method is thermal curing or UV curing. In this embodiment, the composition of the silver paste is: a mixture of epoxy resin glue or UV glue and tiny silver flakes, and the thickness of the silver paste is: 2 microns to 100 microns. In addition, it can also be used: the pad of the circuit board is pre-attached with silver paste, and the suspended end of the metal wire is cured and electrically connected to the pad of the circuit board. Since the silver paste has good adhesion and conductivity, it can be used as a point electrode paste. After curing, it still has good performance according to controllable. 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 silver paste is 2 microns to 100 microns. The curing method is heat curing or UV curing. The composition of the silver paste in this embodiment is: a mixture of epoxy resin glue or UV glue and tiny silver flakes, and the thickness of the silver paste is: 2 microns to 100 microns. The conductive glue in this embodiment can also be made of other metal materials with conductive properties.

In the fourth embodiment, a non-conductive adhesive bonding method may be used, but the second end 122 of the metal wire needs to have good electrical contact with the pad of the circuit board.

After the standard part 200 is formed, the standard part 200 can also be tested. During the electrical test of the standard part 200, the elastic structure of the metal wire 120 is elastically deformed to provide contact pressure. Since the second end 122 of the metal wire is 5 micrometers to 300 micrometers lower than the lower surface of the image sensor chip 110 (please refer to FIG. 1, the distance is h), the connection performance between the metal wire 120 and the test device (not marked) is improved; and during the assembly process of the standard part 200 and the circuit board 300, the elastic structure of the metal wire 120 is elastically deformed to provide contact pressure. Since the second end 122 of the metal wire is 5 micrometers to 300 micrometers lower than the lower surface of the image sensor chip 110 (please refer to FIG. 1, the distance is h), the connection performance between the metal wire and the circuit board can be improved. Please refer to Figure 4, in which the dotted line 120' shows the first shape state of the metal wire 120 when the standard component 200 is not assembled with the circuit board 300; the solid line 120'' shows the second shape state of the metal wire after the standard component 200 and the circuit board 300 are assembled. At this time, the second shape state of the metal wire undergoes elastic deformation, and the second end of the metal wire is in better contact with the pad, which is beneficial to signal transmission. At this time, the contact area between the second end and the pad is greater than or equal to 0.01 square millimeters.

The present invention also provides a multi-camera module, comprising: a plurality of image sensor chips, the image sensor chips being electrically connected with a suspended metal wire, the first end of the metal wire being bonded to a pad of the image sensor chip, and the second end being suspended from the image sensor chip; a lens barrel frame, the lens barrel frame being an integral body suitable for assembling a plurality of lens modules and a plurality of image sensor chips, the lens barrel frame and the image sensor chips being assembled to form a standard part; wherein the photosensitive surfaces of the plurality of image sensor chips are respectively parallel and have no tilt angle; and a circuit board, the circuit board being electrically connected to the standard part via the second end of the metal wire.

The photosensitive surfaces of the multiple image sensor chips are aligned. The metal wire forms an elastic structure and the second end of the metal wire is 5 micrometers to 300 micrometers below the lower surface of the image sensor chip. The second end of the metal wire is connected to the circuit board by a press-fit contact method, a quick welding method, a conductive adhesive bonding method, or a non-conductive adhesive bonding method.

It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-restrictive in any way. Furthermore, it is apparent that the term "comprising" does not exclude other elements and steps, and the wording "a" does not exclude the plural. Multiple elements stated in a device claim may also be implemented by one element. The terms first, second, etc. are used to indicate names and do not indicate any particular order.

Claims (7)

1. The assembling method of the multi-camera module is characterized by comprising the following steps of:

providing a plurality of image sensor chips with suspended metal wires, wherein the first ends of the metal wires are bonded to the bonding pads of the image sensor chips, the second ends of the metal wires are suspended from the image sensor chips, the metal wires form an elastic structure, and the second ends of the metal wires are lower than the lower surface 5 of the image sensor chips

From microns to 300 microns;

providing a lens barrel frame, wherein the lens barrel frame is a whole body and is suitable for assembling a plurality of groups of lens modules and a plurality of image sensor chips;

assembling the plurality of image sensor chips and the lens barrel frame to form a standard component, and then assembling the standard component and a circuit board through the second end of the metal wire to form a multi-camera module;

in the electrical test process of the standard component, 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 test device is improved; in the assembly process of the standard component 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.

2. The method of assembling a multi-camera module of claim 1, wherein the photosensitive surfaces of the plurality of image sensor chips are aligned.

3. The method of assembling a multiple camera module of claim 1, wherein the step of assembling the standard with a circuit board comprises: and electrically connecting the second end of the metal wire with the circuit board through a pressing contact mode, a quick welding mode, a conductive adhesive mode or a non-conductive adhesive mode.

4. A multi-camera module assembled by the assembling method of the multi-camera module according to claims 1 to 3, comprising:

the image sensor chip is electrically connected with suspended metal wires, and the first ends of the metal wires are bonded to bonding pads of the image sensor chip;

the lens barrel frame is a whole body suitable for assembling a plurality of groups of lens modules and a plurality of image sensor chips, and the lens barrel frame and the image sensor chips are assembled to form a standard part; wherein the light sensitive surfaces of the plurality of image sensor chips are respectively parallel and have no inclination angle;

and the circuit board is electrically connected with the standard component through the second end of the metal wire.

5. The multi-camera module of claim 4, wherein the plurality of image sensor chip photosites are aligned.

6. The multi-camera module of claim 4, wherein the metal wire forms a resilient structure.

7. The multi-camera module of claim 4, wherein the second ends of the metal wires are connected to the circuit board by press-fit contact, flash soldering, conductive adhesive, or non-conductive adhesive.