A precision circuit board with high heat dissipation performance and a manufacturing method thereof

Abstract

The present invention discloses a precision circuit board with high heat dissipation performance and a method for manufacturing the same. The method comprises the following steps: cutting a multilayer copper foil having three copper foil layers, with a nickel layer disposed between adjacent copper foil layers; applying dry film to both surfaces of the multilayer copper foil, then opening windows in the dry film at locations corresponding to circuit patterns to produce a plurality of blind vias; performing hole-filling electroplating on the multilayer copper foil to form copper pillars within the blind vias, and then stripping the film; laminating the multilayer copper foil with polypropylene (PP) and exposing the top surfaces of the copper pillars by grinding the plate; peeling the multilayer copper foil apart and removing the middle copper foil layer to form upper and lower production boards; applying film to the PP surface of the production board and then etching to remove the copper foil layer on the other side of the PP; after stripping the film, depositing a copper layer on both surfaces of the PP by copper deposition, and producing outer layer circuits on both surfaces of the PP using a positive film process. The method of the present invention solves the problem that precision circuit boards cannot be produced using conventional copper / silver paste via plugging to meet heat dissipation requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board manufacturing, and in particular to a precision circuit board with high heat dissipation performance and a manufacturing method thereof. Background Art

[0002] For double-sided boards with low reliability requirements, copper and silver pastes can be used to directly plug the vias, taking advantage of their excellent electrical conductivity and heat dissipation properties. Metallization can then be applied to the surface of the copper or silver paste to achieve interlayer connectivity. For multi-layer boards, however, in-hole electroplating is required before copper or silver paste plugging is performed to ensure electrical interconnection performance within the inner layers.

[0003] Simple double-sided copper / silver paste process flow: drilling → copper / silver paste plugging → grinding → outer layer circuit → solder mask → surface treatment → post-process

[0004] The process flow of inner layer buried hole board copper / silver paste: drilling → copper / silver paste plugging → grinding → copper plating, board electroplating → pattern transfer → etching → browning → pressing → post-process.

[0005] As electronic devices become smaller, denser, and more multifunctional, the mounting density of components on printed circuit boards has greatly increased, thereby increasing heat loss on the assembly area. Conventional use of the conductive and heat-dissipating properties of copper / silver paste to directly plug holes will reduce the heat loss of the printed circuit boards. In addition, for precision circuit production, based on the capabilities of drilling equipment and to avoid circuit short circuits, the drilling aperture of 100μm has reached its limit, making it extremely difficult to control and the drilling cost very high. It is also very prone to quality problems such as hole collapse and internal short circuits. At the same time, the distance between holes in different networks needs to be >180μm. Precision circuit boards below this range cannot be cooled by copper / silver paste plugging after drilling, and the production cost of copper / silver paste plugging is high. Summary of the Invention

[0006] In response to the above-mentioned existing technical defects, the present invention provides a method for manufacturing a precision circuit board with high heat dissipation performance. The method can produce a high-precision circuit with a plurality of copper pillars in the circuit area to meet the high heat dissipation performance of the precision circuit board, and solve the problem that the precision circuit board cannot be made using conventional copper / silver paste plugging to meet the heat dissipation requirements.

[0007] In order to solve the above technical problems, the present invention provides a method for manufacturing a precision circuit board with high heat dissipation performance, comprising the following steps:

[0008] In a first aspect, the present invention discloses a method for manufacturing a precision circuit board with high heat dissipation performance, comprising the following steps:

[0009] S1. Cutting a multilayer copper foil, wherein the multilayer copper foil comprises a first copper foil layer, a second copper foil layer, and a third copper foil layer arranged in sequence, and a nickel layer is provided between two adjacent copper foil layers to separate the two adjacent copper foil layers;

[0010] S2. A dry film is applied to both surfaces of the multi-layer copper foil, and then windows are opened on the dry film at positions corresponding to the circuit pattern through exposure and development in sequence to produce a plurality of blind holes exposing the inner copper surface;

[0011] S3, performing hole-filling electroplating on the multi-layer copper foil to form copper pillars in the blind holes, and then retreating the film;

[0012] S4, laminating PP on both surfaces of the multi-layer copper foil and pressing them together, and exposing the top surface of the copper pillar by grinding the plate;

[0013] S5, peeling off the three copper foil layers of the multi-layer copper foil to remove the second copper foil layer in the middle, thereby forming two independent production boards;

[0014] S6. Laminating the PP surface in the production board, and then etching to remove the copper foil layer on the other side of the PP;

[0015] S7. After stripping the film, a layer of copper is deposited on both surfaces of the PP by copper plating, and then the outer layer circuits are made on both surfaces of the PP by the positive film process, and the graphic electroplating process in the positive film process only plates copper but not tin.

[0016] Furthermore, in step S1 , the thickness of the first copper foil layer and the third copper foil layer are both 3 μm, and the thickness of the second copper foil layer is 18 μm.

[0017] Furthermore, in step S2, the thickness of the dry film is 200-300 μm, and the aperture of the blind hole is 100 μm.

[0018] Furthermore, in step S3, the height of the copper pillar is lower than the thickness of the dry film.

[0019] Furthermore, in step S4, excess PP is removed by a ceramic grinding plate to expose the top surface of the copper column.

[0020] Furthermore, in step S6, after the PP surface is filmed, the entire surface is first exposed to protect the exposed copper pillars through the film, and then rapid etching is performed to remove the first copper foil layer or the third copper foil layer on the other surface of the PP to obtain a PP substrate with several copper pillars.

[0021] Furthermore, in step S7, after copper layers are deposited on both surfaces of the PP substrate by copper deposition, a film is then attached to the PP substrate, and a circuit pattern is formed by sequentially exposing and developing. The copper pillars are located in the circuit pattern area. Then, the copper layer thickness at the circuit pattern is thickened by pattern electroplating, and only copper is plated without tin during pattern electroplating. After stripping the film, the copper layer on the board surface in non-circuit pattern areas is removed by rapid etching to obtain a high-heat dissipation precision circuit with several copper pillars.

[0022] Furthermore, in step S7, the copper layer deposited in the copper deposition process can have a thickness of 0.5 μm.

[0023] In a second aspect, the present invention further discloses a method for manufacturing a precision circuit board with high heat dissipation performance, comprising the following steps:

[0024] S1. Cutting a multilayer copper foil, wherein the multilayer copper foil is composed of a first copper foil layer and a second copper foil layer arranged in sequence, and a nickel layer is provided between the first copper foil layer and the second copper foil layer to separate the first copper foil layer and the second copper foil layer; the thickness of the first copper foil layer is 3 μm, and the thickness of the second copper foil layer is 18 μm

[0025] S2, affixing a dry film on the surface of the first copper foil layer, and then sequentially performing exposure and development to open windows at positions corresponding to the circuit pattern on the dry film to produce a plurality of blind holes exposing the surface of the first copper foil layer; and a fully exposed dry film protective film is affixed on the surface of the second copper foil layer;

[0026] S3, performing hole-filling electroplating on the multi-layer copper foil to form copper pillars in the blind holes, and then retreating the film;

[0027] S4, laminating PP on the surface of the first copper foil layer and pressing it, and exposing the top surface of the copper column by grinding the plate;

[0028] S5. peeling off the two copper foil layers of the multi-layer copper foil, removing the second copper foil layer, and retaining the first copper foil layer with PP to form a production board;

[0029] S6. Laminating the PP surface in the production board, and then etching to remove the first copper foil layer on the other side of the PP;

[0030] S7. After stripping the film, a layer of copper is deposited on both surfaces of the PP by copper plating, and then the outer layer circuits are made on both surfaces of the PP by the positive film process, and the graphic electroplating process in the positive film process only plates copper but not tin.

[0031] In a third aspect, the present invention further discloses a precision circuit board with high heat dissipation performance, which is manufactured using the manufacturing method described in any one of the first aspect or the second aspect.

[0032] Furthermore, the following steps are included between steps S3 and S4:

[0033] S31. Grind the copper clad laminate to make the surface smooth.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] In the present invention, a plurality of blind holes are formed by first pasting a dry film on a multi-layer copper foil and opening windows, and then copper pillars are formed after hole filling and electroplating. The copper pillars are located in the circuit area and are used for subsequent heat dissipation. Since the drilling diameter of the copper / silver paste plugging process needs to be greater than 180μm, the existing conventional copper / silver paste plugging process cannot produce high-heat dissipation precision circuit boards with a hole spacing of ≤180μm. However, the blind hole formation method of the present invention through exposure, development and opening windows can make the spacing between holes ≤180μm, meeting the production requirements of high-heat dissipation precision circuit boards with a hole spacing of ≤180μm. In addition, the production process is easy to control, convenient to produce and can effectively improve production quality, solving the problem of high heat dissipation precision circuit boards with a hole spacing of ≤180μm. The existing drilling method is difficult to control, costly, and prone to quality problems such as short circuits. Since adjacent copper foil layers of multi-layer copper foil are separated by a nickel layer, the nickel layer and the copper layer can be peeled off after being combined. The copper pillars and PP are formed into a whole after etching away the copper foil layer on the surface of the PP. This is used as the PP substrate (equivalent to the core board) for circuit board production, and then the outer layer circuits are produced on both surfaces of the PP through copper deposition and positive film processes. In this method, only the thin copper layer formed when copper is deposited in non-circuit patterns is removed during etching, and the etching amount is small, so that high-precision outer layer circuits can be produced, and ultimately high-precision circuit boards can be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the multi-layer copper foil in Example 1;

[0037] Figure 2 Schematic diagram of the process of forming copper pillars after applying a dry film to a multi-layer copper foil and electroplating the copper pillars in Example 1;

[0038] Figure 3 Schematic diagram of forming copper pillars on a multi-layer copper foil and removing the dry film in Example 1;

[0039] Figure 4 Schematic diagram of the multi-layer copper foil and PP after lamination in Example 1;

[0040] Figure 5 This is a schematic diagram of the multi-layer copper foil after peeling off in Example 1;

[0041] Figure 6 This is a schematic diagram of the multi-layer copper foil after removing the second copper foil layer in Example 1;

[0042] Figure 7 This is a schematic diagram of the dry film attached to the production board in Example 1;

[0043] Figure 8 This is a schematic diagram of the production board in Example 1 after etching away the copper foil layer to form a PP substrate. DETAILED DESCRIPTION

[0044] In order to more fully understand the technical content of the present invention, the technical solution of the present invention will be further introduced and illustrated in conjunction with specific embodiments below.

[0045] Example 1

[0046] The method for manufacturing a precision circuit board with high heat dissipation performance shown in this embodiment includes the following processing steps in sequence:

[0047] (1) Cutting: Prepare multiple layers of copper foil and cut them according to the design size, such as Figure 1 As shown, the multi-layer copper foil consists of a first copper foil layer 1, a second copper foil layer 2 and a third copper foil layer 3 arranged in sequence, and a nickel layer (not shown in the figure) is provided between two adjacent copper foil layers to separate the two adjacent copper foil layers; the thickness of the first copper foil layer and the third copper foil layer are both 3μm, the thickness of the second copper foil layer is 18μm, and the thickness of the nickel layer is generally controlled at 0.5μm.

[0048] (2) Film: Figure 2 As shown, dry film 4 is attached to both surfaces of the multi-layer copper foil, and then windows are opened at positions corresponding to the circuit pattern on the dry film through exposure and development in sequence, so as to produce a plurality of blind holes 5 at positions corresponding to the circuit pattern to expose the inner copper surface.

[0049] In the above, the thickness of the dry film is 200-300 μm, and the aperture of the blind hole is 100 μm.

[0050] (3) Hole filling plating: The multi-layer copper foil is subjected to hole filling plating to form copper pillars 6 (such as Figure 2 As shown), while the retreating membrane (as Figure 3 shown).

[0051] In the above, the height of the copper pillar is lower than the thickness of the dry film to prevent the top surface of the copper pillar from extending beyond the dry film and radially expanding beyond the circuit pattern area after electroplating, thereby affecting the subsequent etching operation and circuit quality.

[0052] (4) Pressing: Figure 4 As shown, after PP7 is overlapped on both surfaces of the multi-layer copper foil, it is pressed, only the PP is pressed, and then the excess PP on both surfaces is removed by a ceramic grinding plate, so that the top surface of the copper column is exposed, that is, the top surface of the copper column is flush with the surface of the PP.

[0053] (5) Peeling: Figure 5 As shown, the three copper foil layers of the multi-layer copper foil are peeled off to remove the second copper foil layer in the middle to form two independent production boards (such as Figure 6 As shown), a production board formed by combining the first copper foil layer with the PP and another production board formed by combining the third copper foil layer with the PP.

[0054] (6) Etching: Figure 7 As shown, a dry film 4 is applied to one side of the PP surface in the production board, and then the entire surface is exposed to protect the exposed copper pillars through the dry film, and then rapid etching is performed to remove the first copper foil layer or the third copper foil layer on the other surface of the PP to obtain a PP substrate with several copper pillars (equivalent to the core board for making circuit boards), and then the film is removed (as shown in FIG. Figure 8 shown).

[0055] (7) Copper deposition: A 0.5 μm copper layer is deposited on both surfaces of the PP substrate through the copper deposition process.

[0056] (8) Production of outer circuits: Transfer of outer pattern, using LDI exposure machine, with 5-7 grid exposure scale (21 grid exposure scale) to complete outer circuit exposure, after development, the outer circuit pattern is formed on the PP substrate, and the copper pillar is located in the circuit pattern area; the outer pattern is electroplated, and then copper is plated on the production board, and the copper layer thickness at the outer circuit pattern is plated to the required thickness of the design, and only copper is plated without tin during pattern electroplating; after stripping, the copper layer of the board surface that is not the outer circuit is removed by rapid etching to obtain a high heat dissipation precision circuit with several copper pillars inside; outer layer AOI, using automatic optical inspection system, by comparing with CAM data, to detect whether the outer circuit has defects such as open circuit, gap, incomplete etching, short circuit, etc.

[0057] (9) Post-process: Then, solder mask layer, surface treatment, molding treatment and FQC inspection are made on the PP substrate in sequence to produce a precision circuit board with high heat dissipation performance.

[0058] Example 2

[0059] The method for manufacturing a precision circuit board with high heat dissipation performance shown in this embodiment includes the following processing steps in sequence:

[0060] (1) Cutting: Prepare multi-layer copper foil and cut it according to the designed size. The multi-layer copper foil consists of a first copper foil layer and a second copper foil layer arranged in sequence, and a nickel layer is provided between the first copper foil layer and the second copper foil layer to separate the first copper foil layer and the second copper foil layer; the thickness of the first copper foil layer is 3 μm, the thickness of the second copper foil layer is 18 μm, and the thickness of the nickel layer is generally controlled at 0.5 μm.

[0061] (2) Film pasting: A dry film is pasted on the surface of the first copper foil layer, and then windows are opened on the dry film at the positions corresponding to the circuit patterns through exposure and development in sequence, so as to make a number of blind holes exposing the inner copper surface at the positions corresponding to the circuit patterns; at the same time, a dry film is also pasted on the surface of the second copper foil layer, but the dry film on the second copper foil layer is fully exposed to protect the entire second copper foil layer.

[0062] In the above, the thickness of the dry film is 200-300 μm, and the aperture of the blind hole is 100 μm.

[0063] (4) Hole filling plating: Hole filling plating is performed on multi-layer copper foil to form copper pillars in the blind holes and then retreat the film.

[0064] In the above, the height of the copper pillar is lower than the thickness of the dry film to prevent the top surface of the copper pillar from extending beyond the dry film and radially expanding beyond the circuit pattern area after electroplating, thereby affecting the subsequent etching operation and circuit quality.

[0065] (4) Lamination: Lamination is performed after PP is laminated on the surface of the first copper foil layer. Only PP is laminated, and then excess PP is removed by a ceramic grinding plate to expose the top surface of the copper column, that is, the top surface of the copper column is flush with the surface of PP.

[0066] (5) Peeling: Peel the first copper foil layer and the second copper foil layer apart, remove the second copper foil layer, and retain the first copper foil layer with PP to form a production board.

[0067] (6) Etching: A dry film is applied to one side of the PP surface in the production board, and then the entire surface is exposed to protect the exposed copper pillars through the dry film. Then, a rapid etching is performed to remove the first copper foil layer on the other surface of the PP to obtain a PP substrate with several copper pillars (equivalent to the core board for making circuit boards), and then the film is removed.

[0068] (7) Copper deposition: A 0.5 μm copper layer is deposited on both surfaces of the PP substrate through the copper deposition process.

[0069] (8) Production of outer circuits: Transfer of outer pattern, using LDI exposure machine, with 5-7 grid exposure scale (21 grid exposure scale) to complete outer circuit exposure, after development, the outer circuit pattern is formed on the PP substrate, and the copper pillar is located in the circuit pattern area; the outer pattern is electroplated, and then copper is plated on the production board, and the copper layer thickness at the outer circuit pattern is plated to the thickness required by the design, and only copper is plated without tin during pattern electroplating; after stripping, the copper layer of the board surface that is not the outer circuit is removed by rapid etching to obtain a high heat dissipation precision circuit with several copper pillars inside; outer layer AOI, using automatic optical detection system, by comparing with CAM data, to detect whether the outer circuit has defects such as open circuit, gap, incomplete etching, short circuit, etc.

[0070] (9) Post-process: Then, solder mask layer, surface treatment, molding treatment and FQC inspection are made on the PP substrate in sequence to produce a precision circuit board with high heat dissipation performance.

[0071] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for manufacturing a precision circuit board with high heat dissipation performance, characterized in that: The following steps are involved: S1. Cutting a multilayer copper foil, wherein the multilayer copper foil comprises a first copper foil layer, a second copper foil layer, and a third copper foil layer arranged in sequence, and a nickel layer is provided between two adjacent copper foil layers to separate the two adjacent copper foil layers; S2. Apply dry film to both surfaces of the multi-layer copper foil, and then perform window openings on the dry film at positions corresponding to the circuit pattern through exposure and development in sequence to produce a plurality of blind holes exposing the inner copper surface, with the spacing between adjacent blind holes being ≤180μm; S3, performing hole-filling electroplating on the multi-layer copper foil to form copper pillars in the blind holes, and then retreating the film; S4, laminating PP on both surfaces of the multi-layer copper foil and pressing them together, and exposing the top surface of the copper pillar by grinding the plate; S5, peeling off the three copper foil layers of the multi-layer copper foil to remove the second copper foil layer in the middle, thereby forming two independent production boards; S6. Laminating the PP surface in the production board, and then etching to remove the copper foil layer on the other side of the PP; S7. After stripping the film, a layer of copper is deposited on both surfaces of the PP by copper plating, and then the outer layer circuits are made on both surfaces of the PP by the positive film process, and the graphic electroplating process in the positive film process only plates copper but not tin.

2. The method for manufacturing a precision circuit board with high heat dissipation performance according to claim 1, characterized in that: In step S1 , the thickness of the first copper foil layer and the third copper foil layer are both 3 μm, and the thickness of the second copper foil layer is 18 μm.

3. The method for manufacturing a precision circuit board with high heat dissipation performance according to claim 1, characterized in that: In step S2, the thickness of the dry film is 200-300 μm, and the aperture of the blind hole is 100 μm.

4. The method for manufacturing a precision circuit board with high heat dissipation performance according to any one of claims 1 to 3, characterized in that: In step S3, the height of the copper pillar is lower than the thickness of the dry film.

5. The method for manufacturing a precision circuit board with high heat dissipation performance according to claim 1, wherein: In step S4, excess PP is removed by a ceramic grinding plate to expose the top surface of the copper column.

6. The method for manufacturing a precision circuit board with high heat dissipation performance according to claim 1, wherein: In step S6, after the PP surface is filmed, the entire surface is first exposed to protect the exposed copper pillars through the film, and then rapid etching is performed to remove the first copper foil layer or the third copper foil layer on the other surface of the PP to obtain a PP substrate with several copper pillars.

7. The method for manufacturing a precision circuit board with high heat dissipation performance according to claim 6, characterized in that: In step S7, after copper layers are deposited on both surfaces of the PP substrate by copper deposition, a film is then attached to the PP substrate, and a circuit pattern is formed by sequentially exposing and developing. The copper pillars are located in the circuit pattern area. Then, the copper layer thickness in the circuit pattern is thickened by pattern electroplating, and only copper is plated without tin during pattern electroplating. After stripping the film, the copper layer on the board surface in non-circuit pattern areas is removed by rapid etching, thereby producing a high-heat dissipation precision circuit with several copper pillars.

8. The method for manufacturing a precision circuit board with high heat dissipation performance according to claim 1, wherein: In step S7 , the copper layer deposited in the copper deposition process can have a thickness of 0.5 μm.

9. A method for manufacturing a precision circuit board with high heat dissipation performance, characterized in that: The following steps are involved: S1. Cutting a multilayer copper foil, wherein the multilayer copper foil is composed of a first copper foil layer and a second copper foil layer arranged in sequence, and a nickel layer is provided between the first copper foil layer and the second copper foil layer to separate the first copper foil layer and the second copper foil layer; the thickness of the first copper foil layer is 3 μm, and the thickness of the second copper foil layer is 18 μm S2. A dry film is applied to the surface of the first copper foil layer, and then windows are opened on the dry film at positions corresponding to the circuit pattern through exposure and development in sequence to produce a plurality of blind holes that expose the surface of the first copper foil layer, with the spacing between adjacent blind holes being ≤180μm; and a fully exposed dry film protective film is applied to the surface of the second copper foil layer; S3, performing hole-filling electroplating on the multi-layer copper foil to form copper pillars in the blind holes, and then retreating the film; S4, laminating PP on the surface of the first copper foil layer and pressing it, and exposing the top surface of the copper column by grinding the plate; S5. peeling off the two copper foil layers of the multi-layer copper foil, removing the second copper foil layer, and retaining the first copper foil layer with PP to form a production board; S6. Laminating the PP surface in the production board, and then etching to remove the first copper foil layer on the other side of the PP; S7. After stripping the film, a layer of copper is deposited on both surfaces of the PP by copper plating, and then the outer layer circuits are made on both surfaces of the PP by the positive film process, and the graphic electroplating process in the positive film process only plates copper but not tin.

10. A precision circuit board with high heat dissipation performance, characterized in that: The invention is manufactured by the manufacturing method according to any one of claims 1 to 9.

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