TWI740579B - Circuit board and method for manufacturing the same, and backlight plate - Google Patents

Abstract

A method for manufacturing a circuit board, includes step of: providing a circuit substrate, the circuit board including a base layer and a first wiring layer and a second wiring layer disposed on opposite surfaces of the circuit board, the first wiring layer including a first connecting pad, the second wiring layer including a second connecting pad corresponding to the first connecting pad, the circuit substrate further including a heat conducting post connected to the first connecting pad and the second connecting pad; covering a heat dissipating film at least on the second connecting pad, the heat dissipating film including a heat conducting adhesive and a heat dissipating layer, the heat conducting adhesive disposed between the second connecting pad and the heat dissipating layer, the heat dissipating layer including heat conducting particles and a heat conducting layer wrapping each of the heat conducting particles.

Description

Circuit board and preparation method thereof, and backlight board

This application relates to the technical field of printed circuit boards, and in particular to a circuit board, a method for preparing the circuit board, and a backlight board having the circuit board.

Sub-millimeter light-emitting diodes (Mini LEDs) refer to LEDs with a grain size of about tens of microns. As a new generation of LED display technology, it can be applied to small-pitch LED display screens below P1.0 mm. When used as a backlight, Mini LED adopts COB or "four-in-one" technology to transfer to rigid or flexible substrates in batches. On the one hand, it can achieve local dimming and bring finer light and dark (HDR) partitions, on the other hand, it can By increasing the number of light sources, the light mixing distance (OD distance) is reduced, thereby reducing the thickness of the backlight.

In order to improve luminous efficiency and reduce light loss, Mini LEDs usually need to be matched with a white high-reflectivity substrate (emissivity must exceed 80%). However, in actual work, the heat generated by the Mini LED will be dissipated to the high-reflectivity substrate through the rigid or flexible substrate. If the high-reflectivity substrate fails to dissipate the heat in time, the product will work at high temperatures and affect its service life.

In view of the above, it is necessary to propose a circuit board that can dissipate heat in time and a preparation method thereof.

In addition, it is also necessary to provide a backlight board applied to the above-mentioned circuit board.

The present application also provides a method for preparing a circuit board, including the following steps: providing a circuit substrate, the circuit substrate comprising a base layer and a first circuit layer and a second circuit layer formed on two opposite surfaces of the base layer, the first circuit The layer includes a first connection pad, the second circuit layer includes a second connection pad corresponding to the first connection pad, and the circuit substrate is provided with a thermally conductive connection between the first connection pad and the second connection pad. Pillar; covering the first circuit layer with a protective film so that the first connection pad is exposed to the protective film; and covering at least the second connection pad with a heat dissipation film, the heat dissipation film including a thermally conductive adhesive layer and The heat-dissipating layer, the heat-conducting adhesive layer is located between the second connection pad and the heat-dissipating layer, and the heat-dissipating layer includes heat-conducting particles and a heat-conducting paint covering the outer surface of the heat-conducting particles.

The present application also provides a circuit board, including: a circuit substrate, including a base layer and a first circuit layer and a second circuit layer formed on two opposite surfaces of the base layer, the first circuit layer includes a first connection pad, and the second circuit layer The second circuit layer includes a second connection pad corresponding to the first connection pad, and the circuit substrate is provided with a thermally conductive post connecting the first connection pad and the second connection pad; a protective film covering the first connection pad On a circuit layer, the first connection pad is exposed to the protective film; and a heat dissipation film at least covers the second connection pad. The heat dissipation film includes a thermally conductive adhesive layer and a thermally conductive layer, and the thermally conductive adhesive layer is located on Between the second connection pad and the heat dissipation layer, the heat dissipation layer includes thermally conductive particles and a thermally conductive paint coated on the outer surface of the thermally conductive particles.

The present application also provides a backlight panel, which includes a light-emitting element, the backlight panel further includes the circuit board as described above, and the light-emitting element is mounted on the first connection pad.

The heat generated by the light-emitting element of the present application is conducted to the thermally conductive adhesive layer through the thermally conductive column, and the heat dissipation layer can dissipate the heat energy conducted by the thermally conductive column to the outside, so as to effectively dissipate the heat generated by the light-emitting element and ensure the product The heat dissipation layer includes thermally conductive particles and thermally conductive paint coated on the outer surface of the thermally conductive particles. Therefore, even if the thickness of the heat dissipation layer is small, it can have high heat dissipation performance, which is conducive to the realization of thinner products. .

1: Double-sided copper clad substrate

1a: The first copper foil layer

1b: The second copper foil layer

10: Circuit board

11: The first circuit layer

12: The second circuit layer

13: Grassroots

14: heat conduction column

15: Solder pad

16: thermal pad

20: The first photosensitive layer

21: The first graphic opening

22: The first patterned photosensitive layer

30: second photosensitive layer

31: The second graphic opening

32: The second patterned photosensitive layer

40: Third photosensitive layer

41: The third graphic opening

42: The third patterned photosensitive layer

50: Fourth photosensitive layer

51: The fourth graphic opening

52: Fourth patterned photosensitive layer

60: Protective film

61: Protective film material

70: heat dissipation film

71: Thermally conductive adhesive layer

72: heat dissipation layer

80: Light-emitting element

81: Electrode

100: circuit board

101: Through hole

110: The first connection pad

120: second connecting pad

140: outer peripheral surface

200: Backlight board

810: outer side

D: distance

W: width

FIG. 1 is a cross-sectional view of a double-sided copper clad substrate provided by a preferred embodiment of this application.

2 is a cross-sectional view of the double-sided copper clad substrate shown in FIG. 1 after opening through holes.

3 is a cross-sectional view of the first photosensitive layer and the second photosensitive layer on both sides of the double-sided copper-clad substrate shown in FIG. 2.

4 is a cross-sectional view of developing the first photosensitive layer and the second photosensitive layer shown in FIG. 3 to obtain the first patterned photosensitive layer and the second patterned photosensitive layer.

5 is a cross-sectional view of the through hole shown in FIG. 4 and the first patterned photosensitive layer and the second patterned photosensitive layer after being filled with a thermally conductive material.

6 is a cross-sectional view of the third photosensitive layer and the fourth photosensitive layer on both sides of the double-sided copper clad substrate shown in FIG. 5 being covered.

FIG. 7 is a cross-sectional view of developing the third photosensitive layer and the fourth photosensitive layer shown in FIG. 6 to obtain the third patterned photosensitive layer and the fourth patterned photosensitive layer.

FIG. 8 shows the patterning of the first copper foil layer and the second copper foil layer by the third patterned photosensitive layer and the fourth patterned photosensitive layer shown in FIG. 7 to form the first circuit layer and the second circuit layer A cross-sectional view of the obtained circuit board.

FIG. 9 is a cross-sectional view of the protective film material printed on the first circuit layer shown in FIG. 8.

Fig. 10 is a cross-sectional view of the protective film material shown in Fig. 9 after being developed to obtain a protective film.

11 is a cross-sectional view of the circuit board obtained by covering the heat dissipation film on the second circuit layer shown in FIG. 10.

Fig. 12 is a cross-sectional view of a backlight panel obtained after mounting light-emitting elements on the circuit board shown in Fig. 10.

1 to FIG. 11, a preferred embodiment of the present application provides a method for preparing a circuit board. According to different requirements, the order of the steps of the method can be changed, and some steps can be omitted or combined. The preparation method includes the following steps: Step 1, referring to FIGS. 1 to 8, a circuit substrate 10 is provided. The circuit substrate 10 includes a base layer 13 and a first circuit layer 11 and a second circuit layer formed on two opposite surfaces of the base layer 13. Two circuit layer 12. The first circuit layer 11 includes a first connection pad 110, the second circuit layer 12 includes a second connection pad 120 corresponding to the first connection pad 110, and the circuit substrate 10 is provided with a connection to the first connection pad. The connection pad 110 and the heat conduction post 14 of the second connection pad 120.

In this embodiment, the circuit substrate 10 can be prepared by the following method: as shown in FIG. 1, a double-sided copper-clad substrate 1 is provided, and the double-sided copper-clad substrate 1 includes the base layer 13 and the The first copper foil layer 1a and the second copper foil layer 1b on the opposite surfaces of the base layer 13.

As shown in FIG. 2, at least one through hole 101 that penetrates at least the base layer 13 and the first copper foil layer 1 a is opened in the double-sided copper clad substrate 1. Wherein, the through hole 101 can be formed by mechanical drilling or laser drilling. In this embodiment, the through hole 101 is a through hole that penetrates the base layer 13, the first copper foil layer 1a, and the second copper foil layer 1b. In other embodiments, the through hole 101 may also be a blind hole that only penetrates the base layer 13 and the first copper foil layer 1a (that is, the through hole 101 does not penetrate the second copper foil layer 1b). ).

As shown in FIG. 3, a first photosensitive layer 20 and a second photosensitive layer 30 are respectively covered on the first copper foil layer 1a and the second copper foil layer 1b having the through holes 101.

As shown in FIG. 4, the first photosensitive layer 20 and the second photosensitive layer 30 are exposed and developed to form first pattern openings 21 and second pattern openings 31, respectively, so as to form a first patterned photosensitive layer 22 and the second patterned photosensitive layer 32. Both the first pattern opening 21 and the second pattern opening 31 are used to expose the through hole 101.

As shown in FIG. 5, the first pattern opening 21, the second pattern opening 31, and the through hole 101 are filled with a thermally conductive material, and then the first patterned photosensitive layer 22 and the second patterned photosensitive layer 22 are removed. Patterned photosensitive layer 32. Wherein, the thermally conductive material located in the through hole 101 forms the thermally conductive pillar 14. The thermally conductive material located in the first pattern opening 21 forms a bonding pad 15, the bonding pad 15 is located on the first copper foil layer 1a, and the thermally conductive material located in the second pattern opening 31 is formed The thermal conductive pad 16 is located on the second copper foil layer 1b.

In this embodiment, the thermally conductive material may be electroplated metal or conductive paste, but is not limited thereto. For example, the thermally conductive material may be copper paste or tin paste, and the electroplated metal may be electroplated copper.

As shown in FIG. 6, a third photosensitive layer 40 and a fourth photosensitive layer are respectively covered on the first copper foil layer 1a with the solder pad 15 and the second copper foil layer 1b with the thermal conductive pad 16 Layer 50.

As shown in FIG. 7, the third photosensitive layer 40 and the fourth photosensitive layer 50 are exposed and developed respectively to form a third pattern opening 41 and a fourth pattern opening 51, thereby forming a third patterned photosensitive layer 42 and the fourth patterned photosensitive layer 52. The third pattern opening 41 and the fourth pattern opening 51 are staggered from the solder pad 15 and the thermal conductive pad 16.

As shown in FIG. 8, the first copper foil layer 1a and the second copper foil layer 1b are patterned by the third pattern opening 41 and the fourth pattern opening 51, respectively, to form the first circuit Layer 11 and the second circuit layer 12. At this time, the circuit board 10 is obtained. Wherein, the solder pad 15 is located on the first connection pad 110, and the thermal conductive pad 16 is located on the second connection pad 120.

Step two, referring to FIGS. 9 and 10, a protective film 60 is covered on the first circuit layer 11, so that the bonding pad 15 and the first connection pad 110 corresponding to the bonding pad 15 are exposed to the述保护膜60。 The protective film 60. The solder pad 15 is used to mount the light-emitting element 80 (refer to FIG. 12).

The protective film 60 can be formed by coating white solder resist ink and baking and curing. The white solder resist ink includes a solder resist ink and a light diffusion material (such as titanium dioxide particles or barium titanate particles) mixed in the solder resist ink. The light diffusion material is used to increase the light reflectivity of the white solder resist ink. Wherein, the quality ratio of the light diffusion material in the white solder mask ink can be determined according to the protective film 60 The required light reflectivity is set. In this embodiment, the light reflectivity of the protective film 60 is greater than 90%.

Wherein, the preparation of the protective film 60 includes the following steps: referring to FIG. 9, covering the protective film material 61 on the first circuit layer 11 with the solder pad 15 by printing, and by baking Curing.

Referring to FIG. 10, the protective film material 61 is exposed and developed to expose the bonding pad 15 and the first connection pad 110 to obtain the protective film 60.

Step 3, referring to FIG. 11, at least cover the heat dissipation film 70 on the second connection pad 120 with the thermal pad 16 to obtain the circuit board 100 at this time. The heat dissipation film 70 includes a thermally conductive adhesive layer 71 and a heat dissipation layer 72, and the thermally conductive adhesive layer 71 is located between the second connection pad 120 and the heat dissipation layer 72. Wherein, the material of the thermal conductive adhesive layer 71 is an opaque adhesive (such as a black adhesive), which is used to increase the shielding property and heat absorption performance of the internal structure of the circuit board 100. The heat dissipation layer 72 is used for dissipating the heat energy conducted through the solder pad 15, the heat conduction pillar 14 and the heat conduction pad 16 to the outside. As shown in FIG. 11, in this embodiment, the heat dissipation film 70 covers the entire second circuit layer 12 with the thermal pad 16. The thermally conductive adhesive layer 71 is also filled in the circuit gap of the second circuit layer 12.

In this embodiment, the heat dissipation layer 72 includes thermally conductive particles and a thermally conductive paint coated on the outer surface of the thermally conductive particles, wherein the thermally conductive particles can be selected from materials such as silver, copper, gold and the like. The thermally conductive paint may be a thermally conductive polyester paint, and the thermally conductive polyurethane has better thermal conductivity, and the thermal conductivity reaches 2.2 W/(m.K). Further, the heat dissipation layer 72 can be formed by coating or sputtering, and the thickness of the heat dissipation layer 72 is 3 to 5 microns. Since the material of the heat dissipation layer 72 also has a conductive function, the thermally conductive adhesive layer 71 is also used to electrically isolate the heat dissipation layer 72 and the second circuit layer 12 to avoid short circuits.

In this embodiment, the circuit board 100 includes two circuit layers as an example for description. However, it can be understood that the technical solution of the present application can also be applied to a multilayer circuit board 100 with more than two circuit layers. That is, after the inner circuit layer is formed, the application can also continue to form other circuit layers on the inner circuit layer by the build-up method, and then perform the subsequent steps (such as forming the thermally conductive pillar 14, the bonding pad 15 and the thermally conductive pad). 16. Steps such as covering the protective layer and the heat dissipation film 70). Therefore, the above-mentioned first circuit layer 11 and second circuit layer 12 can be understood as outer circuit layers in the circuit substrate 10.

11, a preferred embodiment of the present application also provides a circuit board 100, the circuit board 100 includes a circuit substrate 10 including a base layer 13 and formed on two opposite surfaces of the base layer 13 The first circuit layer 11 and the second circuit layer 12. The first circuit layer 11 includes a first connection pad 110, the second circuit layer 12 includes a second connection pad 120 corresponding to the first connection pad 110, and the circuit substrate 10 is further provided with a connection to the first connection pad. A thermally conductive pillar 14 connecting the pad 110 and the second connecting pad 120. The first circuit layer 11 is covered with a protective film 60, and the first connection pad 110 is exposed to the protective film 60. At least the second connection pad 120 is covered with a heat dissipation film 70. The heat dissipation film 70 includes a thermally conductive adhesive layer 71 and a heat dissipation layer 72, and the thermally conductive adhesive layer 71 is located between the second connection pad 120 and the heat dissipation layer 72.

In this embodiment, the first connection pad 110 is provided with a solder pad 15 and the second connection pad 120 is provided with a thermal pad 16; the solder pad 15 and the thermal pad 16 and the heat conductive pillar 14 One-piece molding and thermal conductivity connection.

Please refer to FIG. 12, a preferred embodiment of the present application further provides a backlight panel 200, the backlight panel 200 includes the circuit board 100 and at least one light-emitting element 80. The light-emitting element 80 is mounted on the bonding pad 15 and is electrically connected to the first circuit layer 11 through the bonding pad 15. In this embodiment, the light-emitting element 80 is a Mini LED.

In this embodiment, the light-emitting element 80 has two electrodes 81, and each of the electrodes 81 is mounted on one of the bonding pads 15 respectively. The light-emitting element 80 used in the present application has a small width W (W is between 100 microns and 200 microns), so the distance between the two electrodes 81 is also small, so that the thermally conductive pillars 14 are located on the two The outside of the electrode 81. Specifically, each electrode 81 includes an outer side surface 810 away from the other electrode 81. The heat-conducting pillar 14 connected to the solder pad 15 corresponding to the electrode 81 includes an outer peripheral surface 140 (that is, the hole wall of the through hole 101 accommodating the heat-conducting pillar 14 ). The minimum distance D between the outer peripheral surface 140 of the heat conducting column 14 and the outer side surface 810 of the electrode 81 is not less than 5 microns. Therefore, after the through hole 101 is filled with a conductive material, whether the ends of the formed heat-conducting column 14 are flat will not affect the flatness of the light-emitting element 80.

When in use, the heat generated by the light-emitting element 80 is conducted to the thermally conductive adhesive layer 71 via the solder pad 15, the thermally conductive pillar 14 and the thermally conductive pad 16. The heat dissipation layer 72 can dissipate the heat energy conducted by the heat conducting column 14 to the outside, thereby effectively dissipating the heat generated by the light-emitting element 80 and ensuring the service life of the product. Wherein, the heat dissipation layer 72 includes thermally conductive particles and a thermally conductive paint coated on the outer surface of the thermally conductive particles. Therefore, even if the thickness of the heat dissipation layer 72 is small, it can have high heat dissipation performance, which is conducive to the realization of thinner products. At the same time, since the protective film 60 has a large light reflectivity, most of the light emitted by the light-emitting element 80 can be reflected by the protective film 60, so that the product has a high light reflectivity. Firing rate.

Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out. Modifications or equivalent replacements should not depart from the spirit and scope of the technical solutions of the present invention.

11: The first circuit layer

12: The second circuit layer

13: Grassroots

14: heat conduction column

15: Solder pad

16: thermal pad

60: Protective film

70: heat dissipation film

71: Thermally conductive adhesive layer

72: heat dissipation layer

100: circuit board

110: The first connection pad

120: second connecting pad

Claims (11)

A method for preparing a circuit board, which is improved in that it includes the steps of: providing a circuit substrate, the circuit substrate comprising a base layer and a first circuit layer and a second circuit layer formed on two opposite surfaces of the base layer, the first circuit The layer includes a first connection pad, the second circuit layer includes a second connection pad corresponding to the first connection pad, and the circuit substrate is provided with a connection pad that simultaneously connects the first connection pad and the second connection pad A thermally conductive pillar; covering a protective film on the first circuit layer so that the first connection pad is exposed to the protective film; and covering at least a heat dissipation film on the second connection pad, the heat dissipation film including a thermally conductive adhesive layer And a heat dissipation layer, the heat conduction adhesive layer is located between the second connection pad and the heat dissipation layer, and the heat dissipation layer includes heat conduction particles and a heat conduction paint covering the outer surface of the heat conduction particles. The method for manufacturing a circuit board according to claim 1, wherein the heat dissipation layer has a thickness of 3 to 5 microns, and the thermally conductive adhesive layer is a black adhesive material. The method for manufacturing a circuit board according to claim 1, wherein the step of forming the circuit substrate includes: providing a double-sided copper-clad substrate, the double-sided copper-clad substrate comprising the base layer and two oppositely formed on the base layer The first copper foil layer and the second copper foil layer on the surface; in the double-sided copper clad substrate, at least one through hole that penetrates at least the base layer and the first copper foil layer is opened; in the first copper foil layer And the second copper foil layer are respectively covered with a first patterned photosensitive layer and a second patterned photosensitive layer, the first patterned photosensitive layer and the second patterned photosensitive layer respectively have a first patterned opening and a second patterned photosensitive layer Two patterned openings, the first patterned openings are used to expose the through holes; the through holes are filled with a thermally conductive material to obtain the thermally conductive pillars; and the first copper foil layer and the A second copper foil layer, thereby obtaining the first circuit layer and the second circuit layer. The method for manufacturing a circuit board according to claim 3, further comprising: filling the first pattern opening and the second pattern opening with the thermally conductive material, and then removing the first patterned photosensitive layer And the second patterned photosensitive layer; Wherein, the thermally conductive material located in the first pattern opening forms a soldering pad, the soldering pad is located on the first connection pad, the thermally conductive material located in the second pattern opening forms a thermally conductive pad, and the The thermal pad is located on the second connection pad. The method for manufacturing a circuit board according to claim 1, wherein the material of the protective film includes a white solder resist ink, and the white solder resist ink includes a solder resist ink and a light diffusion material mixed in the solder resist ink . A circuit board is improved in that it includes: a circuit substrate including a base layer and a first circuit layer and a second circuit layer formed on two opposite surfaces of the base layer, the first circuit layer includes a first connection pad, and the second circuit layer The second circuit layer includes a second connection pad corresponding to the first connection pad, and the circuit substrate is provided with a thermally conductive pillar that simultaneously connects the first connection pad and the second connection pad; a protective film covering the On the first circuit layer, the first connection pad is exposed to the protective film; and a heat dissipation film covering at least the second connection pad, the heat dissipation film includes a thermally conductive adhesive layer and a thermally conductive layer, the thermally conductive adhesive layer Located between the second connection pad and the heat dissipation layer, the heat dissipation layer includes thermally conductive particles and a thermally conductive paint coated on the outer surface of the thermally conductive particles. The circuit board according to claim 6, wherein the heat dissipation layer has a thickness of 3 to 5 microns, and the thermally conductive adhesive layer is a black adhesive material. The circuit board according to claim 6, wherein the first connection pad is provided with a soldering pad, the second connection pad is provided with a heat-conducting pad, and the soldering pad and the heat-conducting pad are integrally formed with the heat-conducting pillar And the thermal conductivity is connected. The circuit board according to claim 6, wherein the material of the protective film includes a white solder resist ink, and the white solder resist ink includes a solder resist ink and a light diffusion material mixed in the solder resist ink. A backlight panel includes a light-emitting element, wherein the backlight panel further includes the circuit board according to any one of claims 6 to 9, and the light-emitting element is mounted on the first connection pad. The backlight panel according to claim 10, wherein the light-emitting element has two electrodes, each of the electrodes is respectively mounted on one of the first connection pads, and each of the electrodes includes an outer surface corresponding to the The thermally conductive column of the electrode includes an outer peripheral surface, and the outer peripheral surface and the outer side surface The minimum distance between them is not less than 5 microns.

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