Composite circuit board and preparation method thereof, camera module

Abstract

The present application provides a composite circuit board and a preparation method thereof, as well as a camera module. The preparation method comprises the steps of: providing a circuit board with a through slot. Providing a thermally conductive reinforcing sheet, including a reinforcing sheet and a copper-plated layer, wherein the reinforcing sheet is provided with a through hole, and the copper-plated layer is arranged on the opposite surface of the reinforcing sheet and filled in the through hole. The circuit board, the adhesive layer and the thermally conductive reinforcing sheet are stacked so that the thermally conductive reinforcing sheet corresponds to the slot and the area of ​​the circuit board surrounding the slot. Pressing is performed so that the adhesive layer connects the circuit board and the thermally conductive reinforcing sheet to obtain a composite circuit board. The present application can effectively reduce the thickness of the composite circuit board, and the thermally conductive reinforcing sheet can take into account both high thermal conductivity and high rigidity, so that the composite circuit board can effectively dissipate heat.

Description

Technical Field

[0001] The present application relates to the field of circuit board preparation, and in particular to a composite circuit board and a preparation method thereof, and a camera module having the composite circuit board. Background Art

[0002] The camera module usually includes lens assembly, base, filter, photosensitive chip, circuit board and other components. When the camera module is working, the photosensitive chip will continue to generate heat, which is transferred to the circuit board used to carry the photosensitive chip.

[0003] However, if the circuit board fails to dissipate heat effectively, it is easy to deform or even damage the components on the circuit board, causing the photosensitive chip to not work properly. Furthermore, the circuit board needs to have a certain rigidity to prevent the photosensitive chip from breaking due to circuit board deformation during the wiring process. This requires the circuit board to have a certain thickness. However, increasing the thickness of the circuit board runs counter to the development trend of electronic products towards thinness and compactness. Summary of the invention

[0004] In order to solve at least one of the above shortcomings of the prior art, it is necessary to provide a composite circuit board and a method for preparing the same.

[0005] In addition, it is also necessary to provide a camera module having the above-mentioned composite circuit board.

[0006] The present application provides a method for preparing a composite circuit board, comprising the steps of: providing a circuit board, with a through slot; providing a thermally conductive reinforcing sheet, including a reinforcing sheet and a copper-plated layer, wherein a through hole is provided in the reinforcing sheet, and the copper-plated layer is disposed on the surface opposite to the reinforcing sheet and filled in the through hole; stacking the circuit board, the adhesive layer and the thermally conductive reinforcing sheet so that the thermally conductive reinforcing sheet corresponds to the slot and the area of ​​the circuit board surrounding the slot; and pressing so that the adhesive layer connects the circuit board and the thermally conductive reinforcing sheet, thereby obtaining a composite circuit board.

[0007] In a possible implementation, the thermally conductive reinforcement sheet further includes a plurality of thermally conductive columns, which are disposed on the surface of one of the copper-plated layers and extend into the slots.

[0008] In a possible implementation, the thermally conductive reinforcing sheet further includes a surface treatment layer, and the surface treatment layer is disposed on a surface of another copper plating layer.

[0009] In one possible implementation, the copper-plated layer provided with a thermally conductive column includes a first mounting area and a second mounting area arranged around the first mounting area, the thickness of the first mounting area is greater than the thickness of the second mounting area, so that the surface of the first mounting area is protruded compared to the surface of the second mounting area, and the thermally conductive column is arranged on the protruding surface of the first mounting area; the adhesive layer connects the circuit board and the second mounting area, so that the protruding portion of the first mounting area extends into the groove.

[0010] The present application also provides a composite circuit board, comprising: a circuit board, provided with a through slot; a thermally conductive reinforcement sheet, comprising a reinforcement sheet and a copper-plated layer, wherein a through hole is provided in the reinforcement sheet, and the copper-plated layer is arranged on the surface opposite to the reinforcement sheet and filled in the through hole; and an adhesive layer, arranged between the circuit board and the thermally conductive reinforcement sheet, the adhesive layer connects the circuit board and the thermally conductive reinforcement sheet, and the thermally conductive reinforcement sheet corresponds to the slot and the area of ​​the circuit board surrounding the slot.

[0011] In a possible implementation, the thermally conductive reinforcement sheet further includes a plurality of thermally conductive columns, which are disposed on the surface of one of the copper-plated layers and extend into the slots.

[0012] In a possible implementation, the thermally conductive reinforcing sheet further includes a surface treatment layer, and the surface treatment layer is disposed on a surface of another copper plating layer.

[0013] In a possible implementation, the copper-plated layer provided with the heat-conducting pillar includes a first mounting area and a second mounting area provided around the first mounting area, the thickness of the first mounting area is greater than the thickness of the second mounting area, so that the surface of the first mounting area is protruded compared to the surface of the second mounting area, and the heat-conducting pillar is provided on the protruding surface of the first mounting area. The adhesive layer connects the circuit board and the second mounting area, so that the protruding portion of the first mounting area extends into the groove.

[0014] The present application also provides a camera module, including a photosensitive chip, a lens holder, and a lens and a filter disposed in the lens holder. The camera module also includes a composite circuit board, which includes: a circuit board, which is provided with a through slot; a thermally conductive reinforcement sheet, which includes a reinforcement sheet and a copper-plated layer, in which a through hole is provided, and the copper-plated layer is disposed on the opposite surface of the reinforcement sheet and filled in the through hole; and an adhesive layer, which is disposed between the circuit board and the thermally conductive reinforcement sheet, and the adhesive layer connects the circuit board and the thermally conductive reinforcement sheet, and the thermally conductive reinforcement sheet corresponds to the slot and the area surrounding the circuit board. The photosensitive chip is accommodated in the slot and mounted on the thermally conductive reinforcement sheet, and the filter is located between the lens and the photosensitive chip.

[0015] In a possible implementation, the thermally conductive reinforcement sheet further includes a plurality of thermally conductive pillars, which are disposed on the surface of one of the copper-plated layers. The thermally conductive pillars extend into the slots, and thermally conductive material is filled between the slots and the thermally conductive pillars and between the thermally conductive pillars and the photosensitive chip.

[0016] In a possible implementation, the copper-plated layer provided with the heat-conducting pillar includes a first mounting area and a second mounting area provided around the first mounting area, the thickness of the first mounting area is greater than the thickness of the second mounting area, so that the surface of the first mounting area is protruded compared to the surface of the second mounting area, and the heat-conducting pillar is provided on the protruding surface of the first mounting area. The adhesive layer connects the circuit board and the second mounting area, so that the protruding portion of the first mounting area extends into the groove.

[0017] In one possible implementation, the circuit board includes an outer circuit layer and a protective layer disposed on the outer circuit layer, a portion of the outer circuit layer is exposed to the protective layer to form a soldering pad, and the photosensitive chip is electrically connected to the soldering pad via a wire.

[0018] Compared with the prior art, the photosensitive chip in the present application is installed on a thermally conductive reinforcement sheet. Since the thermally conductive reinforcement sheet includes a reinforcement sheet and a second copper-plated layer, the reinforcement sheet has a relatively high hardness and can effectively support the photosensitive chip, thereby avoiding the increase in the thickness of the circuit board due to the improvement of the rigidity of the circuit board in the prior art, thereby effectively reducing the thickness of the composite circuit board; furthermore, the heat generated by the photosensitive chip can be conducted to the thermally conductive reinforcement sheet and dissipated to the outside by the thermally conductive reinforcement sheet. Since the thermal conductivity of the material of the second copper-plated layer is higher than that of the reinforcement sheet, the thermal conductivity effect of the thermally conductive reinforcement sheet can be improved (that is, the thermally conductive reinforcement sheet can take into account both high thermal conductivity and high rigidity), thereby effectively dissipating heat from the composite circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional schematic diagram after the first adhesive layer and the copper foil layer are pressed onto the inner circuit substrate in one embodiment of the present application.

[0020] Figure 2 For Figure 1 A cross-sectional schematic diagram after preparing an outer circuit layer on the copper foil layer and covering it with a second protective layer.

[0021] Figure 3 For Figure 2 A schematic cross-sectional view of the structure shown after slotting.

[0022] Figure 4 It is a cross-sectional schematic diagram after a through hole is opened in the reinforcing sheet and a second copper plating layer is electroplated in one embodiment of the present application.

[0023] Figure 5 For Figure 4 The cross-sectional schematic diagram shown is after the second copper plating layer is leveled.

[0024] Figure 6 For Figure 5 A schematic cross-sectional view of the thermally conductive reinforcing sheet obtained after surface treatment on the second copper plating layer.

[0025] Figure 7 For the general Figure 3 The circuit board shown and Figure 6 The cross-sectional schematic diagram of the composite circuit board obtained by laminating and pressing the thermally conductive reinforcing sheet through the second adhesive layer is shown.

[0026] Figure 8 For Figure 7 The schematic cross-sectional view of the composite circuit board after the photosensitive chip is installed in the groove shown.

[0027] Fig. 9 For Figure 8 The cross-sectional schematic diagram of the camera module obtained after the lens holder is installed on the composite circuit board shown.

[0028] Fig.10 It is a cross-sectional schematic diagram of a reinforcing sheet in another embodiment of the present application.

[0029] Fig.11 For Fig.10 The cross-sectional schematic diagram of the reinforcement sheet after processing is shown.

[0030] Fig.12 For Fig.11 The cross-sectional schematic diagram of the thermally conductive reinforcing sheet obtained after the reinforcing sheet is surface treated is shown.

[0031] Fig.13 For the general Figure 3 The circuit board shown and Fig.12 The cross-sectional schematic diagram of the composite circuit board obtained by laminating and pressing the thermally conductive reinforcement sheets shown.

[0032] Fig.14 For Fig.13 The schematic cross-sectional view of the composite circuit board after the photosensitive chip is installed in the groove shown.

[0033] Fig.15 For Fig.14 The schematic cross-sectional view of the camera module is shown after the slots, conductive pillars and photosensitive chips are filled with heat-conducting materials and the lens holder is installed on the composite circuit board.

[0034] Main component symbols

[0035] Inner circuit board 10 Heat conducting column 44

[0036] Base layer 11 Thermal conductive material 45

[0037] Inner circuit layer 12 Photosensitive chip 50

[0038] Insulation layer 13 Conductor 51

[0039] First protective layer 14 Connecting layer 52

[0040] First adhesive layer 20 Mirror base 60

[0041] Copper foil layer 21 Lens 61

[0042] First copper plating layer 22 Filter 62

[0043] Outer circuit layer 23 Second adhesive layer 70

[0044] Second protective layer 24 Composite circuit board 100, 200

[0045] Slot 25 Solder pad 230

[0046] Circuit board 30 Camera module 300, 400

[0047] Blind slot 33 Through hole 410

[0048] Thermally conductive reinforcing sheet 40, 40' first installation area 421

[0049] Reinforcement sheet 41 Second installation area 422

[0050] The second copper plating layer 42 has a thickness of T1 and T2

[0051] Surface treatment layer 43

[0052] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0055] In order to further explain the technical means and effects adopted by the present application to achieve the intended purpose, the present application is described in detail below in conjunction with the accompanying drawings and preferred implementation methods.

[0056] See also Figures 1 to 7 In one embodiment of the present application, a method for preparing a composite circuit board 100 is provided. The method comprises the following steps:

[0057] S11, see Figure 1 , providing an inner layer circuit substrate 10 , and covering the surface of the inner layer circuit substrate 10 with a first adhesive layer 20 and a copper foil layer 21 .

[0058] The material of the first adhesive layer 20 can be commonly used pure glue.

[0059] In one embodiment, the inner circuit substrate 10 includes a base layer 11, an inner circuit layer 12 disposed on the surface of the base layer 11, and an insulating layer 13 and a first protective layer 14 disposed on the surface of the inner circuit layer 12 in sequence. As shown in the figure, the inner circuit substrate 10 in this embodiment is a flexible double-sided circuit substrate, that is, the inner circuit layer 12 is disposed on the two opposite surfaces of the base layer 11. In another embodiment, the number of circuit layers in the inner circuit substrate 10 can also be changed, for example, at least one intermediate circuit layer (not shown) can be formed on the surface of each inner circuit layer 12 by a layer-building process.

[0060] Among them, the material of the base layer 11 is insulating resin. Specifically, the material of the base layer 11 can be selected from one of the resins such as epoxy resin (epoxyresin), polypropylene (polypropylene, PP), BT resin, polyphenylene ether (Polyphenylene Oxide, PPO), polypropylene (polypropylene, PP), polyimide (polyimide, PI), polyethylene terephthalate (Polyethylene Terephthalate, PET) and polyethylene naphthalate (Polyethylene Naphthalate, PEN).

[0061] The material of the insulating layer 13 is insulating resin, specifically, the material of the insulating layer 13 can be selected from one of epoxy resin, polypropylene, BT resin, polyphenylene ether, polypropylene, polyimide, polyethylene terephthalate, polyethylene naphthalate, etc. The material of the insulating layer 13 can be the same as that of the base layer 11, or different.

[0062] The first protection layer 14 may be a solder resist layer or a cover film (CVL) and is used to prevent the inner circuit layer 12 from being oxidized or short-circuited by welding.

[0063] S12, see Figure 2 , electroplating is performed on the surface of the copper foil layer 21 to form a first copper plating layer 22 , and the copper foil layer 21 and the first copper plating layer 22 are etched through an exposure and development process to obtain an outer circuit layer 23 , and then a second protective layer 24 is covered on the outer circuit layer 23 .

[0064] Part of the outer circuit layer 23 is exposed to the second protective layer 24 to form two pads 230. Each pad 230 is used to electrically connect to the photosensitive chip 50 (see Figure 8 and Fig. 9 The second protective layer 24 may be a solder resist layer or a cover film (CVL). The second protective layer 24 is used to prevent the outer circuit layer 23 from being oxidized or short-circuited by welding.

[0065] S13, see Figure 3 At least one through slot 25 is formed in the second protection layer 24 , the outer circuit layer 23 , the first adhesive layer 20 and the inner circuit substrate 10 , thereby obtaining a circuit board 30 .

[0066] The slot 25 can be formed by punching or laser drilling.

[0067] When the inner circuit substrate 10 is a flexible circuit substrate, the circuit board 30 finally formed is a hard-soft board. Furthermore, the circuit board 30 is also provided with a blind groove 33 that penetrates the second protective layer 24, the outer circuit layer 23 and the first adhesive layer 20. The blind groove 33 is set apart from the slot 25. The blind groove 33 does not penetrate the inner circuit substrate 10, so that the first protective layer 14 is exposed to the blind groove 33. Thus, the part of the inner circuit substrate 10 corresponding to the blind groove 33 constitutes the soft board part of the hard-soft board. In other embodiments, the circuit board 30 is not limited to a hard-soft board, and can also be a hard board or a soft board.

[0068] S14, see Figures 4 to 6 A thermally conductive reinforcing sheet 40 is provided, comprising a reinforcing sheet 41 and a second copper plating layer 42. The reinforcing sheet 41 is provided with a plurality of through holes 410. The second copper plating layer 42 is disposed on the opposite surface of the reinforcing sheet 41 and filled in each through hole 410.

[0069] The width of the through hole 410 is 100-400 micrometers. The width of the through hole 410 is defined as the dimension of the through hole 410 along the extension direction of the circuit board 30. The distance between two adjacent through holes 410 is not less than 60 micrometers.

[0070] In one embodiment, the thermally conductive reinforcing sheet 40 further includes a surface treatment layer 43 disposed on the surface of the second copper plating layer 42. The surface treatment layer 43 can be formed by chemical gold plating, chemical nickel plating, chemical target plating, electroplating nickel, or electroless nickel plating. The surface treatment layer 43 is used to prevent the second copper plating layer 42 from being oxidized.

[0071] In one embodiment, the total thickness of the thermally conductive reinforcing sheet 40 (i.e., the sum of the thickness of the reinforcing sheet 41, the second copper plating layer 42, and the surface treatment layer 43) is 50-400 microns. The thickness of the thermally conductive reinforcing sheet 40 is defined as the dimension of the thermally conductive reinforcing sheet 40 along the extension direction of the circuit board 30. The width of the thermally conductive reinforcing sheet 40 may be greater than the width of the slot 25.

[0072] The reinforcing sheet 41 may be made of steel.

[0073] In one embodiment, the thermally conductive reinforcing sheet 40 may be prepared as follows:

[0074] like Figure 4As shown, a reinforcing sheet 41 is provided, and a plurality of through holes 410 are opened in the reinforcing sheet 41. Each through hole 410 penetrates the reinforcing sheet 41. Then, the second copper plating layer 42 is formed by electroplating on the surface of the reinforcing sheet 41 and in the through holes 410.

[0075] like Figure 5 As shown, the second copper plating layer 42 located on the surface of the reinforcing sheet 41 is leveled. In this embodiment, the second copper plating layer 42 can be leveled by grinding or mechanical milling.

[0076] like Figure 6 As shown, surface treatment is performed on the leveled second copper plating layer 42 to form a surface treatment layer 43 , thereby obtaining a thermally conductive reinforcing sheet 40 .

[0077] S15, see Figure 7 , the circuit board 30, the second adhesive layer 70 and the thermally conductive reinforcing sheet 40 are stacked. After stacking, the outer circuit layer 23 with the solder pad 230 is located on the surface of the circuit board 30 away from the thermally conductive reinforcing sheet 40, and the thermally conductive reinforcing sheet 40 corresponds to the slot 25 and the area of ​​the circuit board 30 surrounding the slot 25. Then, lamination is performed so that the second adhesive layer 70 connects the circuit board 30 and the thermally conductive reinforcing sheet 40, and the composite circuit board 100 is obtained.

[0078] In this embodiment, after the composite circuit board 100 is obtained, the preparation method further includes:

[0079] S16, see Figure 8 , place the photosensitive chip 50 in the slot 25 and install it on the thermally conductive reinforcing sheet 40 , and electrically connect the photosensitive chip 50 to the pad 230 through a wire 51 .

[0080] In one embodiment, the photosensitive chip 50 is mounted on the thermally conductive reinforcing sheet 40 via a connecting layer 52. The connecting layer 52 may be a solder layer or a conductive paste layer (such as solder paste).

[0081] S17, see Fig. 9 A lens holder 60 is installed on the second protective layer 24 corresponding to the outer circuit layer 23 having the pad 230. The lens holder 60 is provided with a lens 61 and a filter 62 opposite to the lens 61, so that the filter 62 is located between the lens 61 and the photosensitive chip 50, thereby obtaining a camera module 300.

[0082] See also Figure 7 The present application also provides a composite circuit board 100 prepared by the above preparation method. The composite circuit board 100 includes a circuit board 30, a second adhesive layer 70 and a thermally conductive reinforcing sheet 40 stacked in sequence. The second adhesive layer 70 connects the circuit board 30 and the thermally conductive reinforcing sheet 40.

[0083] The circuit board 30 includes an inner circuit substrate 10, which includes a base layer 11, an inner circuit layer 12 disposed on the surface of the base layer 11, and an insulating layer 13 and a first protective layer 14 disposed on the surface of the inner circuit layer 12 in sequence. The circuit board 30 also includes a first adhesive layer 20, an outer circuit layer 23, and a second protective layer 24 stacked in sequence on the inner circuit substrate 10. A portion of the outer circuit layer 23 is exposed to the second protective layer 24 to form two pads 230. A slot 25 is opened in the circuit board 30, and the slot 25 passes through the second protective layer 24, the outer circuit layer 23, the first adhesive layer 20, and the inner circuit substrate 10.

[0084] The thermally conductive reinforcing sheet 40 includes a reinforcing sheet 41 and a second copper plating layer 42. A plurality of through holes 410 are provided in the reinforcing sheet 41. The second copper plating layer 42 is disposed on the opposite surface of the reinforcing sheet 41 and fills each through hole 410. The thermally conductive reinforcing sheet 40 may further include a surface treatment layer 43 disposed on the surface of the second copper plating layer 42.

[0085] The outer circuit layer 23 with the solder pad 230 is located on a surface of the circuit board 30 away from the thermally conductive reinforcing sheet 40 , and the thermally conductive reinforcing sheet 40 corresponds to the slot 25 and the area of ​​the circuit board 30 surrounding the slot 25 .

[0086] See also Fig. 9 The present application also provides a camera module 300 made by the above-mentioned preparation method. The camera module 300 includes the above-mentioned circuit board 100, a photosensitive chip 50 and a lens holder 60. The lens holder 60 is provided with a lens 61 and a filter 62 opposite to the lens 61.

[0087] The photosensitive chip 50 is accommodated in the slot 25 and mounted on the thermally conductive reinforcing sheet 40 , and the photosensitive chip 50 is electrically connected to the pad 230 via a wire 51 . The filter 62 is located between the lens 61 and the photosensitive chip 50 .

[0088] Compared with the prior art in which the photosensitive chip 50 is mounted on the circuit board 30, the photosensitive chip 50 in the present application is mounted on the thermally conductive reinforcing sheet 40. Since the thermally conductive reinforcing sheet 40 includes a reinforcing sheet 41 and a second copper-plated layer 42, the reinforcing sheet 41 has a relatively high hardness, and thus can effectively support the photosensitive chip 50, thereby avoiding the prior art in which the thickness of the circuit board 30 is increased due to the increase in the rigidity of the circuit board 30. Therefore, the present application can effectively reduce the thickness of the composite circuit board 100, making the composite circuit board 100 more suitable for thin and light electronic products. Furthermore, the heat generated by the photosensitive chip 50 can be conducted to the thermally conductive reinforcing sheet 40, and dissipated to the outside by the thermally conductive reinforcing sheet 40. Since the thermal conductivity of the material of the second copper-plated layer 42 is higher than that of the reinforcing sheet 41, the thermal conductivity effect of the thermally conductive reinforcing sheet 40 can be improved (i.e., the thermally conductive reinforcing sheet 40 can take into account both high thermal conductivity and high rigidity), thereby effectively dissipating heat from the composite circuit board 100.

[0089] Another embodiment of the present application also provides a method for preparing a composite circuit board 200, wherein steps S21 to S23 of preparing a circuit board 30 are the same as steps S11 to S13, and are not described in detail. Figures 10 to 15 After step S23, the preparation method further comprises the following steps:

[0090] S24, see Figures 10 to 12 A thermally conductive reinforcing sheet 40 ′ is provided, comprising a reinforcing sheet 41 and a second copper plating layer 42 . A plurality of through holes 410 are provided in the reinforcing sheet 41 . The second copper plating layer 42 is disposed on the opposite surface of the reinforcing sheet 41 and fills each through hole 410 .

[0091] The difference from the thermally conductive reinforcing sheet 40 is that in the thermally conductive reinforcing sheet 40', a plurality of thermally conductive pillars 44 are further provided on the surface of one of the second copper-plated layers 42, and the thermally conductive pillars 44 can be formed by integrally extending the second copper-plated layer 42 (i.e., the material of the thermally conductive pillars 44 is also copper). The extension direction of the thermally conductive pillars 44 can be perpendicular to the surface of the second copper-plated layer 42. In one embodiment, the second copper-plated layer 42 includes a first mounting area 421 and a second mounting area 422 arranged around the first mounting area 421. The thickness T1 of the first mounting area 421 can be greater than the thickness T2 of the second mounting area 422, so that the surface of the first mounting area 421 is protruded compared to the surface of the second mounting area 422. The thermally conductive pillars 44 are arranged on the protruding surface of the first mounting area 421.

[0092] In one embodiment, the first mounting area 421 protrudes from the second mounting area 422 by a height of 50-200 micrometers.

[0093] In one embodiment, the thermally conductive reinforcing sheet 40' further includes a surface treatment layer 43. The surface treatment layer 43 is disposed on the surface of the second copper plating layer 42 away from the thermally conductive pillar 44. The surface treatment layer 43 can be formed by chemical gold plating, chemical nickel plating, chemical target plating, electroplating nickel, or electroless nickel plating. The surface treatment layer 43 is used to prevent the reinforcing sheet 41 from oxidation.

[0094] In one embodiment, the thermally conductive reinforcing sheet 40' can be prepared as follows:

[0095] like Fig.10 As shown, a reinforcing sheet 41 is provided, and a plurality of through holes 410 are opened in the reinforcing sheet 41. Each through hole 410 penetrates the reinforcing sheet. Then, electroplating is performed on the surface of the reinforcing sheet 41 and in the through holes 410 to form a second copper plating layer 42.

[0096] like Fig.11As shown, the second copper-plated layer 42 is processed by a computer numerical control machine tool (CNC). After processing, one of the second copper-plated layers 42 forms a first mounting area 421 and a second mounting area 422 with different thicknesses, and a heat-conducting column 44 extending from the surface of the first mounting area 421.

[0097] like Fig.12 As shown, surface treatment is performed on the leveled second copper plating layer 42 to form a surface treatment layer 43, thereby obtaining a thermally conductive reinforcing sheet 40'.

[0098] S25, see Fig.13 , the circuit board 30, the second adhesive layer 70 and the thermally conductive reinforcing sheet 40' are stacked. After stacking, the outer circuit layer 23 with the solder pad 230 is located on the surface of the circuit board 30 away from the thermally conductive reinforcing sheet 40', and the surface treatment layer 43 is located on the surface of the thermally conductive reinforcing sheet 40' away from the circuit board 30. The thermally conductive reinforcing sheet 40' corresponds to the slot 25 and the area of ​​the circuit board 30 surrounding the slot 25, and the thermally conductive column 44 extends into the slot 25. Then, lamination is performed so that the second adhesive layer 70 connects the circuit board 30 and the thermally conductive reinforcing sheet 40' to obtain a composite circuit board 200.

[0099] More specifically, when the second copper plating layer 42 includes the first mounting area 421 and the second mounting area 422 of different thicknesses, the second adhesive layer 70 connects the circuit board 30 and the second mounting area 422 so that the protruding portion of the first mounting area 421 also extends into the groove 25 .

[0100] In this embodiment, after the composite circuit board 200 is obtained, the preparation method further includes:

[0101] S26, see Fig.14 , place the photosensitive chip 50 in the slot 25 and install it on the first installation area 421 of the thermally conductive reinforcing sheet 40 ′, and electrically connect the photosensitive chip 50 to the pad 230 through the wire 51 .

[0102] Since the thickness T1 of the first mounting area 421 is relatively large, the first mounting area 421 has higher thermal conductivity than the second mounting area 422 , which is beneficial for quickly dissipating the heat conducted from the photosensitive chip 50 to the outside.

[0103] S27, see Fig.15 , a heat conducting material 45 is filled between the slot 25 and the heat conducting column 44 and between the photosensitive chip 50 and the heat conducting column 44. The heat conducting material 45 may also cover at least a portion of the wire 51.

[0104] In one embodiment, the spacing between the slot 25 and the heat-conducting column 44 is 100-200 microns. The width of the heat-conducting column 44 is 100-500 microns. The width of the heat-conducting column 44 is defined as the dimension of the heat-conducting column 44 along the extension direction of the circuit board 30. The heat-conducting material 45 can be heat-conducting silica gel.

[0105] S28, install a lens holder 60 on the second protective layer 24 corresponding to the outer circuit layer 23 with the welding pad 230, wherein the lens holder 60 is provided with a lens 61 and a filter 62 opposite to the lens 61, so that the filter 62 is located between the lens 61 and the photosensitive chip 50, thereby obtaining a camera module 400.

[0106] See also Fig.13 The present application also provides a composite circuit board 200 made by the above-mentioned preparation method. The composite circuit board 100 includes a circuit board 30, a second adhesive layer 70 and a thermally conductive reinforcing sheet 40' which are stacked in sequence. The thermally conductive reinforcing sheet 40' has a different structure from the above-mentioned thermally conductive reinforcing sheet 40. The second adhesive layer 70 connects the circuit board 30 and the thermally conductive reinforcing sheet 40'.

[0107] The thermally conductive reinforcing sheet 40' includes a reinforcing sheet 41 and a second copper-plated layer 42. A plurality of through holes 410 are provided in the reinforcing sheet 41. The second copper-plated layer 42 is disposed on the surface opposite to the reinforcing sheet 41 and is filled in each through hole 410. A plurality of heat-conducting pillars 44 are also disposed on the surface of one of the second copper-plated layers 42, and the heat-conducting pillars 44 can be formed by integrally extending the second copper-plated layer 42. In one embodiment, the second copper-plated layer 42 includes a first mounting area 421 and a second mounting area 422 disposed around the first mounting area 421. The thickness T1 of the first mounting area 421 can be greater than the thickness T2 of the second mounting area 422, so that the surface of the first mounting area 421 is protruded compared to the surface of the second mounting area 422. The heat-conducting pillars 44 are disposed on the surface of the first mounting area 421 protruding. The thermally conductive reinforcing sheet 40 may further include a surface treatment layer 43, which is disposed on the surface of the second copper-plated layer 42 away from the heat-conducting pillars 44.

[0108] The outer circuit layer 23 with the solder pad 230 is located on the surface of the circuit board 30 away from the thermally conductive reinforcing sheet 40', the surface treatment layer 43 is located on the surface of the thermally conductive reinforcing sheet 40' away from the circuit board 30, and the thermally conductive reinforcing sheet 40 corresponds to the slot 25 and the area of ​​the circuit board 30 surrounding the slot 25. The thermally conductive column 44 extends into the slot 25.

[0109] See also Fig.14 The present application also provides a camera module 300 made by the above-mentioned preparation method. The camera module 300 includes the above-mentioned circuit board 200, a photosensitive chip 50 and a lens holder 60. The lens holder 60 is provided with a lens 61 and a filter 62 opposite to the lens 61.

[0110] The photosensitive chip 50 is accommodated in the slot 25 and mounted on the thermally conductive reinforcing sheet 40, and the photosensitive chip 50 is electrically connected to the pad 230 through the wire 51. The filter 62 is located between the lens 61 and the photosensitive chip 50. The thermally conductive material 45 is filled between the slot 25 and the thermally conductive column 44 and between the photosensitive chip 50 and the thermally conductive column 44. The thermally conductive material 45 can also cover at least part of the wire 51.

[0111] In the camera module 400 of this embodiment, the heat generated by the photosensitive chip 50 can also be conducted to the thermally conductive pillars 44 and the ground layer (ie, the inner circuit layer 12 ) via the thermally conductive material 45 , thereby improving the thermal conductivity of the thermally conductive reinforcing sheet 40 ′.

[0112] It is understandable that a person skilled in the art can make various other corresponding changes and modifications based on the technical concept of the present application, and all these changes and modifications should fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a composite circuit board, characterized in that: Includes steps: Providing a circuit board with a through slot, wherein the slot is used to accommodate a photosensitive chip; A thermally conductive reinforcing sheet is provided, comprising a reinforcing sheet, a copper-plated layer and a plurality of thermally conductive pillars, wherein a through hole is provided in the reinforcing sheet, the copper-plated layer is arranged on the surface opposite to the reinforcing sheet and filled in the through hole, the thermally conductive pillar is arranged on the surface of one of the copper-plated layers, the thermally conductive pillar extends into the slot, and a thermally conductive material is filled between the slot and the thermally conductive pillar and between the thermally conductive pillar and the photosensitive chip; The circuit board, the adhesive layer and the thermally conductive reinforcing sheet are stacked in sequence, so that the thermally conductive reinforcing sheet corresponds to the slot and the area of ​​the circuit board surrounding the slot; The adhesive layer is pressed to connect the circuit board and the thermally conductive reinforcing sheet, thereby obtaining a composite circuit board.

2. The method for preparing a composite circuit board according to claim 1, characterized in that: The thermally conductive reinforcing sheet further includes a surface treatment layer, and the surface treatment layer is disposed on the surface of the other copper-plated layer.

3. The method for preparing a composite circuit board according to claim 1, characterized in that: The copper-plated layer provided with the heat-conducting pillar comprises a first mounting area and a second mounting area provided around the first mounting area, the thickness of the first mounting area is greater than the thickness of the second mounting area, so that the surface of the first mounting area is protruded compared with the surface of the second mounting area, and the heat-conducting pillar is provided on the protruding surface of the first mounting area; The adhesive layer connects the circuit board and the second mounting area so that a portion of the first mounting area that is protruded extends into the groove.

4. A composite circuit board, characterized in that: include: The circuit board is provided with a through slot, wherein the slot is used to accommodate the photosensitive chip; A thermally conductive reinforcing sheet, comprising a reinforcing sheet, a copper-plated layer and a plurality of thermally conductive pillars, wherein a through hole is provided in the reinforcing sheet, the copper-plated layer is arranged on the surface opposite to the reinforcing sheet and filled in the through hole, the thermally conductive pillar is arranged on the surface of one of the copper-plated layers, the thermally conductive pillar extends into the slot, and a thermally conductive material is filled between the slot and the thermally conductive pillar and between the thermally conductive pillar and the photosensitive chip; An adhesive layer is disposed between the circuit board and the thermally conductive reinforcing sheet, the adhesive layer connects the circuit board and the thermally conductive reinforcing sheet, and the thermally conductive reinforcing sheet corresponds to the slot and an area of ​​the circuit board surrounding the slot.

5. The composite circuit board according to claim 4, characterized in that: The thermally conductive reinforcing sheet further includes a surface treatment layer, and the surface treatment layer is disposed on the surface of the other copper-plated layer.

6. The composite circuit board according to claim 4, characterized in that: The copper-plated layer provided with the heat-conducting pillar comprises a first mounting area and a second mounting area provided around the first mounting area, the thickness of the first mounting area is greater than the thickness of the second mounting area, so that the surface of the first mounting area is protruded compared with the surface of the second mounting area, and the heat-conducting pillar is provided on the protruding surface of the first mounting area; The adhesive layer connects the circuit board and the second mounting area so that a portion of the first mounting area that is protruded extends into the groove.

7. A camera module, comprising a photosensitive chip, a lens holder, and a lens and a filter arranged in the lens holder, characterized in that: The camera module further includes a composite circuit board, and the composite circuit board includes: The circuit board is provided with a through slot; A thermally conductive reinforcing sheet, comprising a reinforcing sheet, a copper-plated layer and a plurality of thermally conductive pillars, wherein the reinforcing sheet is provided with a through hole, the copper-plated layer is arranged on the surface opposite to the reinforcing sheet and fills the through hole, the thermally conductive pillar is arranged on the surface of one of the copper-plated layers, and the thermally conductive pillar extends into the slot; and An adhesive layer is provided between the circuit board and the thermally conductive reinforcing sheet, the adhesive layer connects the circuit board and the thermally conductive reinforcing sheet, and the thermally conductive reinforcing sheet corresponds to the slot and the area of ​​the circuit board surrounding the slot; The photosensitive chip is accommodated in the groove and installed on the thermally conductive reinforcement sheet, the filter is located between the photosensitive chip and the lens, and thermally conductive materials are filled between the groove and the thermally conductive column and between the thermally conductive column and the photosensitive chip.

8. The camera module according to claim 7, wherein: The copper-plated layer provided with the heat-conducting pillar comprises a first mounting area and a second mounting area provided around the first mounting area, the thickness of the first mounting area is greater than the thickness of the second mounting area, so that the surface of the first mounting area is protruded compared with the surface of the second mounting area, and the heat-conducting pillar is provided on the protruding surface of the first mounting area; The adhesive layer connects the circuit board and the second mounting area so that a portion of the first mounting area that is protruded extends into the groove.

9. The camera module according to claim 7, wherein: The circuit board includes an outer circuit layer and a protective layer arranged on the outer circuit layer, a portion of the outer circuit layer is exposed to the protective layer to form a soldering pad, and the photosensitive chip is electrically connected to the soldering pad through a wire.

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