High-flatness circuit board and preparation method thereof

Abstract

The invention discloses a high-flatness circuit board and a preparation method thereof, and belongs to the technical field of circuit board preparation, and the method comprises the steps: preparing a second layer to a penultimate layer of the circuit board, and pressing the second layer to the penultimate layer to prepare a circuit board semi-finished product; placing the prepreg, the pretreated glass, the prepreg and the copper foil on the circuit board semi-finished product from bottom to top in sequence, placing the prepreg, the pretreated glass, the prepreg and the copper foil on the lower portion of the circuit board semi-finished product from top to bottom in sequence, and then conducting pressing to obtain a circuit board finished product; the glass is embedded between the first layer and the second layer of the circuit board and between the last but one layer and the last but one layer of the circuit board, the flatness of the circuit board is improved on the upper side and the lower side, the CTE of the glass is lower than that of a traditional material of the circuit board, the warping problem of the circuit board can be further solved, high flatness can be achieved only by introducing the glass in one step, and the production cost is reduced. The method is low in process implementation difficulty, and is universal for the preparation process of all circuit boards.

Description

Technical Field

[0001] The invention relates to a high-flatness circuit board and a preparation method thereof, belonging to the technical field of circuit board preparation. Background Art

[0002] With the application and promotion of high-speed communication technology, the design of communication products and the density of product wiring are getting higher and higher. The size of chip design is getting larger and larger. The requirements for the flatness of PCB boards during product assembly are getting higher and higher.

[0003] In the prior art, the flatness of circuit boards is mainly controlled by controlling the stress during the board manufacturing process. However, this method is difficult to implement, the process flow is very complicated, and it is not universal for all circuit boards. Summary of the invention

[0004] The purpose of the present invention is to provide a high-flatness circuit board and a preparation method thereof, so as to solve the problems of complex process flow and low applicability in the prior art.

[0005] To achieve the above objectives, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides a method for preparing a high-flatness circuit board, comprising: preparing the second layer to the second to last layer of the circuit board, and laminating the second layer to the second to last layer to form a semi-finished circuit board product; A prepreg, pretreated glass, prepreg and copper foil are placed in sequence from bottom to top above the semi-finished circuit board product, and a prepreg, pretreated glass, prepreg and copper foil are placed in sequence from top to bottom below the semi-finished circuit board product, and then pressed together to form a finished circuit board product.

[0006] Furthermore, the preparation of the second layer to the penultimate layer of the circuit board includes: The second to the second to last layers of the circuit board are processed using copper clad laminate, and the circuit patterns are etched on the third to the third to last layers.

[0007] Furthermore, the process of laminating the second layer to the penultimate layer to form a semi-finished circuit board includes: laminating the second layer to the penultimate layer, sequentially undergoing chemical copper reduction, mechanical hole processing, hole metallization, resin hole plugging, signal hole drilling, back drilling, resin hole plugging, and overall metallization, and then etching the circuit pattern of the second layer and the penultimate layer.

[0008] Furthermore, laminating the second layer to the penultimate layer comprises: The second layer to the penultimate layer are respectively overlapped with the prepreg and pressed in a high-temperature press. During pressing, the second layer and the penultimate layer are electrostatically cleaned. After pressing, the second layer and the penultimate layer are cleaned and polished.

[0009] Further, the preprocessing includes: The glass surface is roughened by grinding both sides of the glass; An enlarged hole is punched on the glass, the position of the enlarged hole corresponds to the conductive hole that needs to be connected between the first layer and the second layer of the circuit board, and the aperture of the enlarged hole is larger than the aperture of the conductive hole; Punching fixing grooves and fixing holes around the glass to position and fix the glass; All holes and slots on the glass are metallized and resin plugged, and then the glass is browned or roughened.

[0010] Furthermore, the roughening includes sanding and chemical etching.

[0011] Furthermore, the punching of the enlarged hole is performed by a carbon dioxide laser or a picosecond laser, and the punching of the fixing groove and the fixing hole is performed by a laser.

[0012] Furthermore, punching the fixing grooves and fixing holes around the glass includes: punching the fixing grooves and fixing holes around the area where the enlarged hole is located.

[0013] Furthermore, the manufacturing of the finished circuit board includes: The holes of the first layer and the penultimate layer are first etched. If there is exposed resin after etching, laser drilling is used to burn through to the second layer and the penultimate layer. Laser laser is performed on the etched holes to obtain laser laser holes. The laser laser holes are filled with electroplating. The circuit patterns of the first layer and the penultimate layer are etched, and then the subsequent preparation process of the circuit board is carried out to obtain a finished circuit board.

[0014] In a second aspect, the present invention provides a high-flatness circuit board, which is prepared by any method described in the first aspect.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: The present invention provides a high-flatness circuit board and a preparation method thereof, wherein glass is buried between the first layer and the second layer, and between the penultimate layer and the second-to-last layer of the circuit board, thereby improving the flatness of the circuit board on both the upper and lower sides, and the CTE of the glass is lower than that of traditional circuit board materials, which can further improve the warping problem of the circuit board, and high flatness can be achieved by only introducing the glass in one step, the process is easy to implement, and is universal for the preparation processes of all circuit boards. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of a method for preparing a high-flatness circuit board corresponding to Embodiment 1 of the present invention; Figure 2 is a schematic diagram of step 1 in embodiment 2 of the present invention; Figure 3 is a schematic diagram of a cross section of glass after step 2 in embodiment 2 of the present invention is completed; Figure 4 is a top view of the glass after step 2 in embodiment 2 of the present invention is completed; Figure 5 is a schematic diagram of glass after step 3 in Example 2 of the present invention is completed; Figure 6 is a schematic diagram of glass after step 4 in Example 2 of the present invention is completed; Figure 7 is a schematic diagram of glass after step 9 in Example 2 of the present invention is completed; Figure 8 is a schematic diagram of the hole after etching in step 10 in Example 2 of the present invention; Fig. 9 is a schematic diagram after laser irradiation in step 10 in embodiment 2 of the present invention; Fig.10 It is a schematic diagram of the hole filling after electroplating in step 10 in embodiment 2 of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0018] Example 1.

[0019] like Figure 1 As shown, the present invention provides a method for preparing a high-flatness circuit board, comprising: preparing the second layer to the second to last layer of the circuit board, and laminating the second layer to the second to last layer to form a semi-finished circuit board product; A prepreg, pretreated glass, prepreg and copper foil are placed in sequence from bottom to top above the semi-finished circuit board product, and a prepreg, pretreated glass, prepreg and copper foil are placed in sequence from top to bottom below the semi-finished circuit board product, and then pressed together to form a finished circuit board product.

[0020] The present invention improves the flatness of the circuit board on both the upper and lower sides by burying the glass between the first layer and the second layer and between the penultimate layer and the penultimate layer of the circuit board. The CTE of the glass is lower than that of traditional circuit board materials, which can further improve the warping problem of the circuit board. High flatness can be achieved by only introducing the glass. The process is easy to implement and is universal for the preparation process of all circuit boards.

[0021] Example 2.

[0022] The present invention provides a method for preparing a high-flatness circuit board, comprising: Step 1: After grinding both sides of the glass, the surface of the glass is roughened by sanding. The process is as follows: Figure 2 shown.

[0023] Step 2: Use a carbon dioxide laser or a picosecond laser to drill holes (enlarge holes) in the glass of the second step. The diameter of the enlarged hole is larger than the diameter of the via hole on the finished circuit board. The size larger than the via hole diameter is set according to the equipment processing capacity. The position of the enlarged hole is determined by the conduction relationship between the first layer and the second layer. The position that needs to be conducted is drilled, and the laser burns out fixed holes and fixed grooves at the same time.

[0024] The positions of the enlarged holes, fixing holes and fixing slots are as follows: Figure 4 As shown in the figure, the cross section of the glass after drilling is completed is as follows Figure 3 shown.

[0025] Step 3: Metallize all holes and grooves of the glass. Figure 5 shown.

[0026] Step 4: Plug the glass with resin, then brown or other roughening. Figure 6 shown.

[0027] Step 5: Use a copper clad laminate to process the second and third layers, the fourth and fifth layers, the sixth and seventh layers, until the second to last layer and the third to last layer, and etch the circuit pattern according to the traditional process of the circuit board, but the second and second to last layers are not processed with circuit patterns.

[0028] Step 6: After overlapping the layers of copper clad laminates prepared in step 5 and the semi-cured laminates, press them in a high-temperature press. During pressing, the second layer and the penultimate layer need to be electrostatically cleaned. After pressing, the second layer and the penultimate layer need to be cleaned and polished.

[0029] Step 7: After lamination, the second layer to the penultimate layer are a whole. After chemical copper reduction on the second layer and the penultimate layer, the whole is subjected to mechanical hole processing and hole metallization. After the hole is metallized, all the holes are plugged with resin, and after plugging, the signal holes and back drilling are performed. After back drilling, the second resin plugging is performed.

[0030] Step 8: After plugging the holes, metallize the entire structure. After metallization, etch the circuit patterns on the second layer and the penultimate layer.

[0031] Step 9: Use the ultra-thin glass fiber prepreg to press together the copper foil and the glass structure of step 4, where the copper foil is the first and last layer of the circuit board. After step 9, the circuit board structure is as follows Figure 7 As shown, there is glass between the first and second layers, and there is glass between the penultimate layer (last layer) and the penultimate layer.

[0032] Step 10: Etch the first and last layers of advanced holes. The structure after etching is as follows Figure 8 As shown in the figure, the exposed resin after etching can be burned through to the second layer and the second to last layer by laser drilling, and laser blasting is performed at the etched holes. The structure after laser blasting is as shown in the figure. Fig. 9 As shown, the laser hole is filled with electroplating, and the structure after the hole filling electroplating is as follows Fig.10 shown.

[0033] Step 11: Process the circuit graphics of the first layer and the last layer to form the outer layer graphics of the circuit board, and then carry out other circuit board process processing.

[0034] Step 12: You can choose to use laser to separate the boards according to the thickness of the boards, or you can first perform laser cutting on thicker boards, that is, cut from the first layer to the second layer, and cut the last layer to the second to last layer, and then use the board-lifting method to separate the boards.

[0035] Step 13: Other processes are processed according to the traditional complete circuit board process until the finished circuit board is obtained.

[0036] The warpage of the circuit board before adding the glass is >120um / inch, and the warpage of the circuit board after adding the glass can be <100um / inch. The warpage test method is shadow morie (thermal deformation appearance detection). The temperature conditions set during the test are: room temperature to 260 and then down to room temperature.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a high-flatness circuit board, characterized in that: include: preparing the second layer to the second to last layer of the circuit board, and laminating the second layer to the second to last layer to form a semi-finished circuit board product; A prepreg, pretreated glass, prepreg and copper foil are placed in sequence from bottom to top above the semi-finished circuit board product, and a prepreg, pretreated glass, prepreg and copper foil are placed in sequence from top to bottom below the semi-finished circuit board product, and then pressed together to form a finished circuit board product.

2. The method for preparing a high-flatness circuit board according to claim 1, characterized in that: The method of preparing the second layer to the penultimate layer of the circuit board comprises: The second to the second to last layers of the circuit board are processed using copper clad laminate, and the circuit patterns are etched on the third to the third to last layers.

3. The method for preparing a high-flatness circuit board according to claim 1, characterized in that: The method of laminating the second layer to the penultimate layer to form a semi-finished circuit board includes: laminating the second layer to the penultimate layer, sequentially performing chemical copper reduction, mechanical hole processing, hole metallization, resin hole plugging, signal hole drilling, back drilling, resin hole plugging, overall metallization, and then etching the circuit pattern of the second layer and the penultimate layer.

4. The method for preparing a high-flatness circuit board according to claim 3, characterized in that: The laminating of the second layer to the penultimate layer comprises: The second layer to the penultimate layer are respectively overlapped with the prepreg and pressed in a high-temperature press. During pressing, the second layer and the penultimate layer are electrostatically cleaned. After pressing, the second layer and the penultimate layer are cleaned and polished.

5. The method for preparing a high-flatness circuit board according to claim 1, characterized in that: The pre-processing comprises: The glass surface is roughened by grinding both sides of the glass; An enlarged hole is punched on the glass, the position of the enlarged hole corresponds to the conductive hole that needs to be connected between the first layer and the second layer of the circuit board, and the aperture of the enlarged hole is larger than the aperture of the conductive hole; Punching fixing grooves and fixing holes around the glass to position and fix the glass; All holes and slots on the glass are metallized and resin plugged, and then the glass is browned or roughened.

6. The method for preparing a high-flatness circuit board according to claim 5, characterized in that: The roughening includes sanding and chemical etching.

7. The method for preparing a high-flatness circuit board according to claim 5, characterized in that: The punching of the enlarged hole is performed by a carbon dioxide laser or a picosecond laser, and the punching of the fixing groove and the fixing hole is performed by a laser.

8. The method for preparing a high-flatness circuit board according to claim 5, characterized in that: Punching the fixing grooves and fixing holes around the glass includes punching the fixing grooves and fixing holes around the area where the enlarged hole is located.

9. The method for preparing a high-flatness circuit board according to claim 1, characterized in that: The finished circuit board product comprises: The holes of the first layer and the penultimate layer are first etched. If there is exposed resin after etching, laser drilling is used to burn through to the second layer and the penultimate layer. Laser laser is performed on the etched holes to obtain laser laser holes. The laser laser holes are filled with electroplating. The circuit patterns of the first layer and the penultimate layer are etched, and then the subsequent preparation process of the circuit board is carried out to obtain a finished circuit board.

10. A high flatness circuit board, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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