Method for preparing circuit board with embedded electrical insulating heat sink

Abstract

The present invention discloses a method for preparing a circuit board with an embedded electrically insulating heat sink. In a specific embodiment, the preparation method includes the following steps: preparing a circuit substrate with an accommodating through hole, wherein the outer surface of the outer core board in the circuit substrate has a first copper foil layer; preparing an electrically insulating heat sink, wherein the two opposite surfaces of the electrically insulating heat sink have a second copper foil layer; placing the electrically insulating heat sink into the accommodating through hole, and hot pressing the circuit substrate under a negative pressure environment, and providing an adhesive film on opposite sides of the circuit substrate during hot pressing, and the adhesive film fills the gap between the first copper foil layer and the second copper foil layer during hot pressing; removing the adhesive film, and filling the gap between the first copper foil layer and the second copper foil layer with copper. The preparation method of the present invention can ensure the consistency of the copper thickness of the outer conductive circuit of the circuit board and improve product quality.

Description

Technical Field

[0001] The present invention relates to the field of circuit boards; more specifically, to a method for preparing a circuit board with an embedded electrical insulating heat sink. Background Art

[0002] Various heat-generating electronic devices such as LED devices (e.g., LED light-emitting devices), thyristors, GTOs (gate turn-off thyristors), GTRs (power transistors), MOSFETs (power field-effect transistors), IGBTs (insulated gate bipolar transistors), and power diodes are usually mounted on circuit boards and generally release a large amount of heat during operation. Therefore, circuit boards used to mount these heat-generating electronic devices are usually required to have good heat dissipation performance.

[0003] Embedding a heat sink in a circuit board is an effective way to improve heat dissipation performance. Figure 1 The typical structure of such a circuit board is shown, which includes a circuit substrate 100 and an electrically insulating heat sink 200 embedded in the circuit substrate 100, the circuit substrate 100 includes a multi-layer core board 110 and a semi-cured sheet 120 arranged between adjacent core boards 110, the outer surface of the circuit substrate 100 has a first copper foil layer 130, and the two opposite surfaces of the electrically insulating heat sink 200 have a second copper foil layer 210.

[0004] When preparing the circuit board of the above structure, the electrical insulating heat sink 200 can be fixed in the circuit substrate 100 by hot pressing the circuit substrate 100. Specifically, when the circuit substrate 100 is hot pressed, the prepreg 120 will flow into the gap between the circuit substrate 100 and the electrical insulating heat sink 200, thereby achieving a bonding connection between the electrical insulating heat sink 200 and the circuit substrate 100.

[0005] Furthermore, in this preparation method, in order to realize the electrical connection between the circuit substrate 100 and the conductive circuit on the electrically insulating heat sink 200, it is necessary to first form a thickened copper foil layer 300 on two opposite surfaces of the circuit board after hot pressing, and then perform patterning etching on the first copper foil layer 130, the second copper foil layer 210 and the third copper foil layer 300 to produce the outer conductive circuit. However, since the prepreg 120 will simultaneously fill the gap between the first copper foil layer 130 and the second copper foil layer 210 during hot pressing, the thickness of the outer conductive circuit at the connection between the first copper foil layer 130 and the second copper foil layer 210 is small (only the thickness of the thickened copper foil layer 300), and the consistency of the thickness of the outer conductive circuit cannot be maintained, which affects the conductive performance of the circuit board.

[0006] Therefore, it is necessary to improve the above-mentioned circuit board preparation method. Summary of the invention

[0007] The main purpose of the present invention is to provide a method for preparing a circuit board, which can ensure that the outer conductive circuit formed on the circuit board with an embedded electrical insulating heat sink has better thickness consistency.

[0008] In order to achieve the above main purpose, the present invention discloses a method for preparing a circuit board with an embedded electrical insulating heat sink, comprising the following steps:

[0009] A circuit substrate with an accommodating through hole is prepared; wherein the circuit substrate comprises a multi-layer core board and a prepreg sheet arranged between adjacent core boards, two core boards in the multi-layer core board are outer core boards, and the outer surface of the outer core board has a first copper foil layer;

[0010] Prepare an electrically insulating heat sink; wherein two opposite surfaces of the electrically insulating heat sink both have a second copper foil layer;

[0011] The electrically insulating heat sink is placed in the receiving through hole, and then the circuit substrate is hot pressed under a negative pressure environment; wherein, during the hot pressing, a resist film is arranged on opposite sides of the circuit substrate, and the resist film is controlled to fill the gap between the first copper foil layer and the second copper foil layer during the hot pressing process;

[0012] After the hot pressing is completed, the resist film is removed first, and then copper is filled in the gap between the first copper foil layer and the second copper foil layer.

[0013] In order to achieve the above main purpose, the present invention also discloses another method for preparing a circuit board with an embedded electrical insulating heat sink, comprising the following steps:

[0014] A circuit substrate with an accommodating through hole is prepared; wherein the circuit substrate comprises a core board and a first copper foil layer arranged on opposite sides of the core board, and a prepreg is arranged between the first copper foil layer and the core board;

[0015] Prepare an electrically insulating heat sink; wherein two opposite surfaces of the electrically insulating heat sink both have a second copper foil layer;

[0016] The electrically insulating heat sink is placed in the receiving through hole, and the circuit substrate is hot pressed under a negative pressure environment; wherein, during the hot pressing, a resist film is arranged on opposite sides of the circuit substrate, and the resist film is controlled to fill the gap between the first copper foil layer and the second copper foil layer during the hot pressing process;

[0017] After the hot pressing is completed, the resist film is removed first, and then copper is filled in the gap between the first copper foil layer and the second copper foil layer.

[0018] According to a specific embodiment of the present invention, the above-mentioned preparation method further includes, after the copper filling step, first copper plating the two opposite surfaces of the circuit board, and then making an outer conductive circuit on at least one surface of the circuit board.

[0019] According to a specific embodiment of the present invention, a metal foil, such as aluminum foil, is also disposed on the outer side of the adhesive barrier film during hot pressing.

[0020] According to a specific embodiment of the present invention, the electrically insulating heat sink is a ceramic heat sink, such as an aluminum nitride, aluminum oxide, silicon nitride or silicon carbide ceramic heat sink.

[0021] According to a specific embodiment of the present invention, preparing the circuit substrate includes the step of forming an exhaust channel in the circuit substrate, wherein the exhaust channel is provided so that the adhesive barrier film can better fill the gap between the first copper foil layer and the second copper foil layer under the action of negative pressure.

[0022] The technical solution of the present invention has the following beneficial effects:

[0023] In the preparation method of the present invention, a resist film is arranged on opposite sides of the circuit substrate during hot pressing, and the resist film is controlled to fill the gap between the first copper foil layer and the second copper foil layer during the hot pressing process. After hot pressing, copper is filled in the gap between the first copper foil layer and the second copper foil layer, which can well ensure the consistency of the thickness of the outer conductive line of the circuit board and improve the conductive performance and product quality of the circuit board.

[0024] Furthermore, the resist film fills the gap between the first copper foil layer and the second copper foil layer during the hot pressing process, and the electrically insulating heat sink can be positioned by hot pressing, so that there is a uniform gap between the electrically insulating heat sink and the circuit substrate, and the semi-cured sheet can be evenly filled between the electrically insulating heat sink and the circuit substrate, thereby improving the connection reliability between the electrically insulating heat sink and the circuit substrate.

[0025] In order to more clearly illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of a circuit board with an embedded electrical insulating heat sink in the prior art;

[0027] Figure 2 is a schematic structural diagram of a circuit substrate to be hot pressed in Example 1 of the present invention;

[0028] Figure 3 is a structural schematic diagram of a hot pressing process of a circuit substrate in Example 1 of the present invention;

[0029] Figure 4 is a schematic diagram of the structure of the circuit board after copper filling in Embodiment 1 of the present invention;

[0030] Figure 5 This is a schematic diagram of the structure of the circuit board after the entire board is copper plated in Example 1 of the present invention;

[0031] Figure 6 is a schematic structural diagram of a circuit substrate to be hot pressed in Example 2 of the present invention;

[0032] Figure 7 is a structural schematic diagram of a hot pressing process of a circuit substrate in Example 2 of the present invention;

[0033] Figure 8 It is a schematic diagram of the structure of the circuit board after copper filling in Example 2 of the present invention. DETAILED DESCRIPTION

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other variations or replacements made on this basis. Therefore, other possible implementation methods that may be known to those skilled in the art based on the embodiments described in this application all belong to the protection scope of the present invention.

[0035] Example 1

[0036] The circuit board manufacturing method of Example 1 includes the steps of preparing a circuit substrate 10 to be hot-pressed and an electrical insulating heat sink 20. Figure 2 As shown, the circuit substrate 10 includes two core boards 11 and a prepreg 12 arranged between adjacent core boards 11. Both core boards 11 are outer core boards, and their outer surfaces have an outer copper foil layer 111 (first copper foil layer), and their inner surfaces have an inner copper foil layer 112. It should be noted that although the circuit substrate 10 in the illustrated embodiment only includes two core boards 11, the number of layers of the core board 11 can be three or more (in this case, the outermost core board is the outer core board, and the core board between the outer core boards is the inner core board), which can be specifically set according to the thickness of the circuit board and / or the number of layers of the conductive circuit. In the present invention, the core board 11 can be a FR-4 core board, but it is not limited to this.

[0037] The core board 11 and the prepreg 12 are subjected to window opening treatment to form a through hole 14 for embedding the electrical insulation heat sink 20 in the circuit substrate 10. In the present invention, the electrical insulation heat sink 20 can be a ceramic heat sink, such as aluminum nitride, aluminum oxide, silicon nitride or silicon carbide ceramic heat sink. The two opposite surfaces of the electrical insulation heat sink 20 have a copper foil layer 21 (second copper foil layer), and the thickness of the copper foil layer 21 can be the same as the thickness of the outer copper foil layer 111; the copper foil layer 21 can completely cover the surface of the electrical insulation heat sink 20 (such as Figure 2 As shown), it may also be spaced apart from the edge of the electrically insulating heat sink 20 .

[0038] Furthermore, the circuit board manufacturing method of Example 1 includes the steps of placing the electrically insulating heat sink 20 into the receiving through hole 14, and then hot pressing the circuit substrate 10 under a negative pressure environment; wherein, Figure 3As shown, during hot pressing, a resist film 101 is arranged on opposite sides of the circuit substrate 10. Different from the existing preparation method in which a release film is arranged on opposite sides of the circuit substrate 10 during the hot pressing step, the resist film 101 in the present invention has a flexible and deformable characteristic and can be deformed under the action of pressure and temperature. During the hot pressing process, the resist film 101 is controlled to fill the gap between the outer copper foil layer 111 and the copper foil layer 21, so that the resist film 101 forms a filling portion 1011 that prevents the semi-cured sheet 12 from flowing into the gap between the outer copper foil layer 111 and the copper foil layer 21. In addition, during hot pressing, a metal foil 102 can also be arranged on the outside of the resist film 101 to improve the quality of hot pressing. Among them, the metal foil 102 can be an aluminum foil.

[0039] In the preparation method of the present invention, the hot pressing parameters such as the material, thickness, hot pressing pressure / temperature and / or negative pressure of the adhesive film 101 can be controlled so that the filling portion 1011 of the adhesive film 101 completely fills the gap between the outer copper foil layer 111 and the copper foil layer 21 during the hot pressing process, which can ensure the consistency of the thickness of the outer layer of the circuit board and will not affect the reliable connection between the electrical insulation heat sink 20 and the circuit substrate 10. The thickness of the adhesive film 10 can be 25μm to 100μm, such as 50μm and 75μm, which can be selected according to the specific situation, and the present invention is not limited to this.

[0040] Preferably, there is a gap between the copper foil layer 21 and the edge of the electrically insulating heat sink 20 , that is, the edge area of ​​the surface of the electrically insulating heat sink 20 is not covered by the copper foil layer 21 , which helps the adhesive film 101 to more easily fill the gap between the outer copper foil layer 111 and the copper foil layer 21 .

[0041] like Figure 4 As shown, after the hot pressing is completed, the resist film 101 is removed, and copper is then filled in the gap between the outer copper foil layer 111 and the copper foil layer 21 to form a copper hole 31 that fills the gap between the two. The copper hole 31 can be prepared by a blind hole electroplating process, and the specific steps can be referred to the prior art and will not be repeated here.

[0042] Furthermore, if Figure 5 As shown, after the copper filling step, the two opposite surfaces of the circuit board are copper plated throughout the board to form a thickened copper foil layer 32. After the entire board is copper plated, an outer conductive circuit is made on at least one surface of the circuit board, a portion of which is located on the electrically insulating heat sink 20, and another portion is located on the circuit substrate 10. The steps for making the outer conductive circuit can refer to the prior art and will not be repeated here.

[0043] In the preparation method of the present invention, the preparation of the circuit substrate 10 preferably includes the step of forming an exhaust channel in the circuit substrate 10, and the exhaust channel is connected to the accommodating through hole 14. During hot pressing, the accommodating through hole 14 can be connected to the external negative pressure environment, which is more conducive to the resistance film 101 filling the gap between the outer copper foil layer 111 and the copper foil layer 21 under the action of negative pressure.

[0044] In Example 1, the exhaust channel can be provided in the inner copper foil layer 112. For example, the inner copper foil layer 112 can be made with inner conductive lines, and the gaps between the inner conductive lines are used as the exhaust channel during hot pressing. In addition to using the gaps between the inner conductive lines as the exhaust channel, exhaust grooves can also be processed in the inner copper foil layer 112 to serve as the exhaust channel.

[0045] In the preparation method of Example 1, the resist film 101 is set on the opposite sides of the circuit substrate 10 for hot pressing, and the resist film 101 is controlled to fill the gap between the outer copper foil layer 111 and the copper foil layer 21 during the hot pressing process. After hot pressing, copper is filled in the gap between the outer copper foil layer 111 and the copper foil layer 21, which can well ensure the consistency of the thickness of the outer conductive line of the circuit board, thereby improving the conductive performance and product quality of the circuit board.

[0046] Furthermore, the resist film 101 fills the gap between the outer copper foil layer 111 and the copper foil layer 21 during the hot pressing process, and the electrically insulating heat sink 20 can be positioned by hot pressing, so that there is a uniform gap between the electrically insulating heat sink 20 and the circuit substrate 10, and the semi-cured sheet 12 can be uniformly filled between the electrically insulating heat sink 20 and the circuit substrate 10, thereby improving the connection reliability between the electrically insulating heat sink 20 and the circuit substrate 10.

[0047] Example 2

[0048] like Figure 6 As shown, in the preparation method of Example 2, the circuit substrate 10 includes a core board 11 and a copper foil layer 13 (first copper foil layer) arranged on opposite sides of the core board 11, and a prepreg 12 is arranged between the copper foil layer 13 and the core board 11; wherein the copper foil layer 13 can be an RCC copper foil (resin-coated copper foil), and the thickness of the copper foil layer in the RCC copper foil is the same as the thickness of the copper foil layer 21. It should be noted that, although the circuit substrate 10 in Example 2 includes only one inner core board 11, the number of layers of the core board 11 can be two or more, which can be specifically set according to the thickness of the circuit board and / or the number of layers of the conductive circuit.

[0049] The core board 11 and the prepreg 12 are subjected to window opening treatment to form a receiving through hole 14 for embedding the electrical insulating heat sink 20 in the circuit substrate 10; the copper foil layer 13 is also subjected to window opening treatment to facilitate the placement of the electrical insulating heat sink 20 in the receiving through hole 14.

[0050] like Figure 7 As shown, in the preparation method of Example 2, during hot pressing, a resist film 101 is disposed on opposite sides of the circuit substrate 10, and the resist film 101 is controlled to fill the gap between the copper foil layer 13 and the copper foil layer 21 during hot pressing, so that the resist film 101 forms a filling portion 1011 that prevents the prepreg from flowing into the gap between the copper foil layer 13 and the copper foil layer 21. Similar to Example 1, a metal foil 102 may also be disposed on the outside of the resist film 101 during hot pressing to improve the quality of hot pressing.

[0051] like Figure 8 As shown, after the hot pressing is completed, the resist film 101 is removed, and copper is then filled in the gap between the outer copper foil layer 111 and the copper foil layer 21 to form a hole copper 31 that fills the gap between the two. Similar to Example 1, after the copper filling step, the two opposite surfaces of the circuit board are firstly copper plated to form a thickened copper foil layer, and then an outer conductive circuit is made on at least one surface of the circuit board.

[0052] In the preparation method of Example 2, the preparation of the circuit substrate 10 may also include the step of forming an exhaust channel in the circuit substrate 10. Specifically, the exhaust channel may be made in the inner copper foil layer 113 on the surface of the inner core board 11. For example, the inner copper foil layer 113 may be made with an inner conductive circuit, and the gaps between the inner conductive circuits are used as the exhaust channel during hot pressing. In addition to using the gaps between the inner conductive circuits as the exhaust channel, an exhaust groove may be processed in the inner copper foil layer 113 to serve as the exhaust channel.

[0053] The parts of Example 2 that are the same as those of Example 1 are not described here, and reference may be made to Example 1.

[0054] It is easy to understand that the circuit board preparation method of the present invention may also include steps such as making a solder mask layer on the surface of the circuit board and making the circuit board shape. These steps can refer to the existing technology in the field, so the detailed description thereof is omitted here.

[0055] Although the present invention is disclosed as above with specific embodiments, these specific embodiments are not intended to limit the scope of the present invention. Any person skilled in the art can make some changes / replacements without departing from the scope of the present invention, that is, all equivalent changes made according to the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a circuit board with an embedded electrical insulating heat sink, comprising the following steps: preparing a circuit substrate having an accommodating through hole; in, The circuit substrate comprises a multi-layer core board and a prepreg sheet arranged between adjacent core boards, two core boards in the multi-layer core board are outer core boards, and the outer side surface of the outer core board has a first copper foil layer; Prepare an electrical insulating heat sink; wherein two opposite surfaces of the electrical insulating heat sink have a second copper foil layer; The electrically insulating heat sink is placed in the accommodating through hole, and then the circuit substrate is hot pressed under a negative pressure environment; wherein, during the hot pressing, a resist film is arranged on opposite sides of the circuit substrate, and the resist film is controlled to fill the gap between the first copper foil layer and the second copper foil layer during the hot pressing process; After the hot pressing is completed, the resist film is removed, and copper is then filled in the gap between the first copper foil layer and the second copper foil layer.

2. The preparation method according to claim 1, further comprising include: After the copper filling step, the two opposite surfaces of the circuit board are firstly copper plated throughout the board, and then an outer conductive circuit is made on at least one surface of the circuit board.

3. The preparation method according to claim 1, in, During hot pressing, a metal foil is also arranged on the outer side of the adhesive barrier film.

4. The preparation method according to claim 1, in, The electrical insulation heat sink is a ceramic heat sink.

5. The preparation method according to claim 1, in, The preparation of the circuit substrate includes the step of forming an exhaust passage in the circuit substrate that communicates with the accommodating through hole.

6. A method for preparing a circuit board with an embedded electrical insulating heat sink, comprising the following steps: preparing a circuit substrate having an accommodating through hole; in, The circuit substrate comprises a core board and a first copper foil layer arranged on two opposite sides of the core board, and a prepreg is arranged between the first copper foil layer and the core board; Prepare an electrical insulating heat sink; wherein two opposite surfaces of the electrical insulating heat sink have a second copper foil layer; The electrically insulating heat sink is placed in the accommodating through hole, and the circuit substrate is hot pressed under a negative pressure environment; wherein, during the hot pressing, a resist film is arranged on opposite sides of the circuit substrate, and the resist film is controlled to fill the gap between the first copper foil layer and the second copper foil layer during the hot pressing process; After the hot pressing is completed, the resist film is removed, and copper is then filled in the gap between the first copper foil layer and the second copper foil layer.

7. The preparation method according to claim 6, further comprising include: After the copper filling step, the two opposite surfaces of the circuit board are firstly copper plated throughout the board, and then an outer conductive circuit is made on at least one surface of the circuit board.

8. The preparation method according to claim 6, in, During hot pressing, a metal foil is also arranged on the outer side of the adhesive barrier film.

9. The preparation method according to claim 6, in, The electrical insulation heat sink is a ceramic heat sink.

10. The preparation method according to claim 6, in, The preparation of the circuit substrate includes the step of forming an exhaust passage in the circuit substrate that communicates with the accommodating through hole.

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