TWI838065B - Printed circuit board with symmetrical lamination structure and method for producing the same - Google Patents

Abstract

A printed circuit board with a symmetrical lamination structure and a method for producing the same are provided. The printed circuit board includes an inner layer circuit structure and two outer layer circuit structures. The inner layer circuit structure is formed through one-time lamination, and has a first drill hole penetrating a first joint surface and a second joint surface thereof. The first drill hole has a first hole diameter, and the inner sidewall of the first drill hole is formed with a first electroplated conductive layer. The two outer layer circuit structures are respectively laminated to the first joint surface and the second joint surface of the inner layer circuit structure through a second-time lamination. One of the two outer layer circuit structures has a second drill hole. The second drill hole corresponds in position to the first drill hole. The second drill hole has a second hole diameter larger than the first hole diameter, and the inner sidewall of the second drill hole is formed with a second electroplated conductive layer connected to the first electroplated conductive layer.

Description

Printed circuit board with symmetrical pressed structure and manufacturing method thereof

The present invention relates to a circuit board and a manufacturing method thereof, and in particular to a printed circuit board with a symmetrical pressed structure and a manufacturing method thereof.

As shown in Figure 4, in the prior art, a printed circuit board containing high-frequency materials can be applied to terminal application products with high-frequency requirements.

Under the design requirements of some products containing mixed-pressing materials and having asymmetric stacked printed circuit boards (such as high-frequency and high-speed products), the above-mentioned printed circuit boards need to be designed with blind hole structures. However, the primary pressed circuit structure 200A and the secondary pressed circuit structure 200B formed by secondary pressing contained in the above-mentioned printed circuit board have asymmetric plate structures. The thickness of the primary pressed circuit structure 200A is significantly greater than the thickness of the secondary pressed circuit structure 200B. Among them, the secondary pressed circuit structure is a high-frequency material. After the pressing operation, the above-mentioned printed circuit board with mixed-pressing materials has a more serious board bending problem, and the board bending height may reach 40 mm, thus causing troubles at the product application end.

The technical problem to be solved by the present invention is to provide a printed circuit board with a symmetrical pressing structure and a manufacturing method thereof in view of the shortcomings of the existing technology, which can meet the needs of having a blind hole structure and can further solve the problem of board bending without increasing the thickness of the board.

In order to solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a printed circuit board with a symmetrical pressed structure, which includes: an inner layer circuit structure; wherein the inner layer circuit structure is formed by a single press, and the inner layer circuit structure has a first drill hole penetrating the first joint surface and the second joint surface thereof, the first drill hole has a first aperture, and an inner side wall of the first drill hole is formed with a first electroplated conductive layer; and two outer layer circuit structures, wherein the inner layer circuit structure is formed by a single press, and the inner layer circuit structure has a first drill hole penetrating the first joint surface and the second joint surface thereof, the first drill hole has a first aperture, and a first electroplated conductive layer is formed on an inner side wall of the first drill hole; and The first joint surface and the second joint surface of the inner layer circuit structure are respectively pressed symmetrically on the structure through secondary pressing; wherein one of the two outer layer circuit structures has a second drill hole, the second drill hole corresponds to the first drill hole in position, the second drill hole has a second hole diameter greater than the first hole diameter, and an inner side wall of the second drill hole is formed with a second electroplated conductive layer connected to the first electroplated conductive layer.

In order to solve the above technical problems, another technical solution adopted by the present invention is to provide a method for manufacturing a printed circuit board with a symmetrical pressed structure, which includes: performing a first pressing operation to form an inner layer circuit structure that has been pressed once, and the inner layer circuit structure has a first joint surface and a second joint surface located on opposite sides; performing a first drilling operation to form a first drill hole that penetrates the first joint surface and the second joint surface in the inner layer circuit structure, and the first drill hole has a first aperture; performing a first electroplating operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a second pressing operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a second pressing operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a second pressing operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a second pressing operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a second pressing operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a first electroplating ... A process is performed to symmetrically press two outer circuit structures onto the first joint surface and the second joint surface of the inner circuit structure through secondary pressing; a second drilling process is performed to form a second drill hole on one of the two outer circuit structures; wherein the second drill hole corresponds to the first drill hole in position and has a second hole diameter greater than the first hole diameter; and a second electroplating process is performed to form a second electroplated conductive layer directly connected to the first electroplated conductive layer on an inner side wall of the second drill hole to achieve electrical connection.

The printed circuit board with a symmetrical pressing structure and the manufacturing method thereof provided by the present invention can meet the customer's demand for a product with a blind hole structure, and can further solve the problem of board bending without increasing the thickness of the board of the original stacking design. The blind hole structure of the present invention is formed by a specially designed first drill hole and a second drill hole, so that the printed circuit board can have a symmetrical pressing structure, thereby effectively solving the problem of board bending.

To further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings provided are only for reference and description and are not used to limit the present invention.

[The present invention]

100: Printed circuit board

110: Inner circuit structure

110a: first joint surface

110b: Second joint surface

111: First drilling hole

112: First electroplating conductive layer

113: Resin material

114: Inner core substrate

115: Inner adhesive layer

116: Inner circuit pattern

D1: First aperture

120: Outer layer circuit structure

121: Second drilling hole

122: Second electroplating conductive layer

123: Solder mask ink

124: Outer dielectric substrate

125: Outer adhesive layer

126: Outer layer circuit pattern

D2: Second aperture

H: Electroplated vias

V: Laser blind via

S: Browning treatment surface

P: Projection area

[Prior Art]

200A: Single-stage compression circuit structure

200B: Secondary compression circuit structure

Figure 1 is a schematic cross-sectional view of a printed circuit board according to an embodiment of the present invention.

Figure 2A is a schematic diagram of step S101 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2B is a schematic diagram of step S102 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2C is a schematic diagram of step S103 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2D is a schematic diagram of step S104 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2E is a schematic diagram of step S105 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2F is a schematic diagram of step S106 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2G is a schematic diagram of step S107 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2H is a schematic diagram of step S108 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2I is a schematic diagram of step S109 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2J is a schematic diagram of step S110 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 2K is a schematic diagram of step S111 of the method for manufacturing a printed circuit board according to an embodiment of the present invention.

Figure 3 is a schematic diagram of a projection area of a printed circuit board according to an embodiment of the present invention.

Figure 4 is a schematic cross-sectional view of a printed circuit board in the prior art.

The following is a specific embodiment to illustrate the implementation method disclosed by the present invention. The technical personnel in this field can understand the advantages and effects of the present invention from the content disclosed in this manual. The present invention can be implemented or applied through other different specific embodiments. The details in this manual can also be modified and changed based on different viewpoints and applications without deviating from the concept of the present invention. In addition, the attached drawings of the present invention are only for simple schematic illustration and are not depicted according to actual size. Please note in advance. The following implementation method will further explain the relevant technical content of the present invention in detail, but the disclosed content is not used to limit the scope of protection of the present invention.

It should be understood that although the terms "first", "second", "third" and so on may be used in this article to describe various components or signals, these components or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" used in this article may include any one or more combinations of the related listed items depending on the actual situation.

[Printed circuit board with symmetrical pressed structure]

Please refer to FIG. 1 , an embodiment of the present invention provides a printed circuit board 100 with a symmetrical pressed structure. The printed circuit board 100 includes: an inner circuit structure 110 and two outer circuit structures 120 formed on two opposite surfaces of the inner circuit structure 110.

The printed circuit board of the embodiment of the present invention can meet the customer's demand for a product with a blind hole structure, and can further solve the problem of board bending without increasing the thickness of the board of the original stacking design. The specific structural features of the inner layer circuit structure 110 and the outer layer circuit structure 120 and the connection relationship between them will be specifically described below.

The inner circuit structure 110 is formed by one press-fitting, and defines a first joint surface 110a (e.g., upper surface) and a second joint surface 110b (e.g., lower surface) located on opposite sides. The inner circuit structure 110 further has a first drill hole 111, and the first drill hole 111 is formed by penetrating the first joint surface 110a and the second joint surface 110b of the inner circuit structure 110. The first drill hole 111 has a first aperture D1. The first drill hole 111 can be formed, for example, by mechanical drilling, but the present invention is not limited thereto.

In some embodiments of the present invention, the first aperture D1 of the first drill hole 111 is not less than 2 mils, and preferably not less than 4 mils, but the present invention is not limited thereto.

Furthermore, a first electroplated conductive layer 112 is formed on an inner wall of the first drill hole 111. The material of the first electroplated conductive layer 112 may be, for example, metal copper, and the first electroplated conductive layer 112 may be formed, for example, by electroplating, but the present invention is not limited thereto.

In addition, the first electroplated conductive layer 112 is not only formed on the inner wall of the first drill hole 111, but also extends to form the first bonding surface 110a and the second bonding surface 110b of the inner layer circuit structure 110 to form a circuit pattern on the surface.

In this embodiment, the first electroplated conductive layer 112 is used to electrically connect the multi-layer circuits of the inner layer circuit structure 110 (such as the multi-layer inner layer circuit pattern 116 shown in FIG. 1 ), and an inner space surrounded by the first electroplated conductive layer 112 is filled with a resin material 113. The resin material 113 may be, for example, epoxy resin, but the present invention is not limited thereto.

In addition, in this embodiment, the inner circuit structure 110 includes a plurality of inner core substrates 114 and an inner adhesive layer 115 formed between the plurality of inner core substrates 114 and used for bonding. In addition, two layers of inner circuit patterns 116 are formed on both side surfaces of each inner core substrate 114.

The inner core substrate 114 can also be called a core. The material of the inner core substrate 114 can be, for example, a glass fiber cloth (such as FR-4), which is a non-high-frequency material, but the present invention is not limited thereto.

The inner adhesive layer 115 is used to adhere two adjacent inner core substrates 114, and the material of the inner adhesive layer 115 can be, for example, a semi-cured adhesive sheet (such as Prepreg, PP glue).

The two inner circuit patterns 116 formed on the two side surfaces of the inner core substrate 114 can be formed by, for example, metal copper foil through circuit etching, but are not limited thereto.

The inner circuit structure 110 is formed by pressing together the multiple inner core substrates 114 having the inner circuit pattern 116 through the inner adhesive layer 115. In addition, the number of layers of the inner circuit pattern 116 of the inner circuit structure 110 is usually twice the number of the inner core substrates 114. For example, the number of the inner core substrates 114 in this embodiment is two, and the number of layers of the inner circuit pattern 116 is four, but the present invention is not limited thereto.

Please refer to FIG. 1 again. The two outer circuit structures 120 are respectively pressed onto the first joint surface 110a and the second joint surface 110b of the inner circuit structure 110 through secondary pressing, thereby forming a symmetrical printed circuit board stacking structure.

More specifically, the two outer circuit structures 120 are symmetrically pressed onto the first joint surface 110a and the second joint surface 110b of the inner circuit structure 110 in the structure, so as to balance the stress on the first joint surface 110a and the second joint surface 110b of the printed circuit board 100 formed after the secondary pressing, thereby reducing the degree of board bending of the printed circuit board.

Furthermore, one of the two outer layer circuit structures 120 (the upper outer layer circuit structure 120 shown in FIG. 1 ) has a second drill hole 121, and the second drill hole 121 corresponds in position to the first drill hole 111.

The second drill hole 121 has a second aperture D2, and the second aperture D2 of the second drill hole 121 is larger than the first aperture D1 of the first drill hole 111. The second drill hole 121 can also be formed by mechanical drilling, for example, but the present invention is not limited thereto.

In some embodiments of the present invention, the second aperture D2 of the second drill hole 121 is not greater than 12 mils, and preferably not greater than 8 mils, but the present invention is not limited thereto.

In addition, the difference between the second aperture D2 and the first aperture D1 is not less than 1 mil, and preferably not less than 2 mils, but the present invention is not limited thereto.

It is worth mentioning that the above mil is also called filament or strip, which is a unit of length commonly used in the field of printed circuit board technology to describe the size of the aperture. As known to those skilled in the art, 1 mil is equal to 25.4 microns.

Furthermore, a second electroplated conductive layer 122 is formed on an inner wall of the second drill hole 121, and the second electroplated conductive layer 122 directly abuts against the first electroplated conductive layer 112 and is electrically connected to each other. In this embodiment, as shown in FIG. 1 , the bottom of the second electroplated conductive layer 122 abuts against the first electroplated conductive layer 112 and is roughly V-shaped or U-shaped, but the present invention is not limited thereto.

The material of the second electroplated conductive layer 122 can be, for example, copper metal, and the second electroplated conductive layer 122 can be, for example, formed by electroplating, but the present invention is not limited thereto. In addition, in addition to being formed on the inner wall of the second drill hole 121, the second electroplated conductive layer 122 also extends to form the outer surfaces of the two outer layer circuit structures 120 to form an outer layer circuit pattern.

In this embodiment, the second electroplated conductive layer 122 is configured to electrically connect the different layers of the corresponding outer layer circuit structure 120 (such as the upper outer layer circuit structure 120 in FIG. 1 ) (such as the outer layer circuit pattern 126 in FIG. 1 ), and is further electrically connected to the first electroplated conductive layer 112. The inner space surrounded by the second electroplated conductive layer 122 is filled with a solder mask 123 (such as a solder mask).

In addition, in this embodiment, each of the outer circuit structures 120 includes an outer dielectric substrate 124, an outer adhesive layer 125 and two outer circuit patterns 126. The two outer circuit patterns 126 are formed on the two side surfaces of the outer dielectric substrate 124, and the outer dielectric substrate 124 having the outer circuit pattern 126 is adhered to the first joint surface 110a or the second joint surface 110b of the inner circuit structure 110 through the outer adhesive layer 125, but the present invention is not limited thereto. The number of layers of the outer dielectric substrate 124 and the outer circuit pattern 126 of each outer circuit structure 120 is not limited to that shown in FIG. 1, and can be adjusted according to the design requirements of the product.

Specifically, among the two outer circuit structures 120, the outer circuit structure 120 disposed on the first joint surface 110a of the inner circuit structure 110 has the second drill hole 121. In addition, an outer dielectric substrate 124 of the outer circuit structure 120 disposed on the second joint surface 110b of the inner circuit structure 110 is formed of a high-frequency material.

It is worth mentioning that the high-frequency materials mainly use Teflon (PTFE) and polyphenylene oxide (PPO). The two resins have good material stability and reliability in high-frequency environments, but the present invention is not limited to this. Furthermore, the outer dielectric substrate 124 of another outer layer circuit structure 120 can be, for example, glass fiber cloth (such as: FR-4), but the present invention is not limited to this.

The material of the outer adhesive layer 125 may be, for example, a semi-cured bonding sheet (such as Prepreg), and the two outer circuit patterns 126 formed on the two side surfaces of the outer dielectric substrate 124 may be, for example, formed by metal copper foil through circuit etching, but the present invention is not limited thereto.

In a modified embodiment of the present invention, among the two outer circuit structures 120, the outer circuit structure 120 disposed on the first joint surface 110a of the inner circuit structure 110 has the second drill hole 121, and the outer dielectric substrate 124 of the outer circuit structure 120 having the second drill hole 121 is formed of a high-frequency material.

It should be noted that the "first joint surface 110a" and "second joint surface 110b" of the inner circuit structure 110 referred to in this article are only for the convenience of distinguishing one surface from another surface. However, in actual application, the "first joint surface 110a" of the inner circuit structure 110 is not limited to being always facing upward, and the "second joint surface 110b" is not limited to being always facing downward. In addition, the number of the first drill hole 111 and the second drill hole 121 connected thereto is not limited to two as shown in FIG. 1, and can be changed according to design requirements, and the present invention does not limit it.

As shown in FIG. 1 , from another perspective, the first drill hole 111 of the inner layer circuit structure 110 and the first electroplated conductive layer 112 formed on the inner side wall of the first drill hole 111 are buried between the two outer layer circuit structures 120, and the second drill hole 121 is a blind hole connected to the first drill hole 111.

Furthermore, in this embodiment, the printed circuit board 100 has a plated through hole H (PTH) vertically penetrating the inner layer circuit structure 110 and the two outer layer circuit structures 120. In addition, at least one of the two outer layer circuit structures 120 has a laser blind hole V. In this embodiment, both of the two outer layer circuit structures 120 have the laser blind hole V.

Furthermore, as shown in FIG. 3 , in a projection area P projected along a normal vector of the printed circuit board 100 , a first outer contour of the first drill hole 111 falls on the inner side of a second outer contour of the second drill hole 121 .

According to the aperture relationship design of the above two drill holes (D1 and D2), the difficulty of the alignment operation of the second drill hole 121 and the first drill hole 111 can be effectively reduced, and the second electroplated conductive layer 122 can easily abut against the first electroplated conductive layer 112 to maintain electrical connection.

In addition, the printed circuit board of the embodiment of the present invention can meet the customer's demand for products with blind hole structures, and can further solve the problem of circuit board bending without increasing the thickness of the board of the original stacking design.

In some embodiments of the present invention, the thickness of the two outer wiring structures 120 is substantially the same. The thickness of each outer wiring structure 120 is less than the thickness of the inner wiring structure 110. In addition, the stress applied by one of the outer wiring structures 120 to the inner wiring structure 110 is substantially equal to the stress applied by the other outer wiring structure 120 to the inner wiring structure 110.

[Manufacturing method of printed circuit board with symmetrical pressed structure]

The above is a description of the structural features and material features of the printed circuit board with a symmetrical pressed structure of the embodiment of the present invention, and the following will describe the manufacturing method of the printed circuit board with a symmetrical pressed structure of the embodiment of the present invention.

Please refer to Figures 2A to 2K. The embodiment of the present invention provides a method for manufacturing a printed circuit board with a symmetrical pressed structure, which includes steps S101 to S111. It must be noted that the order and actual operation method of each step in this embodiment can be adjusted according to needs and are not limited to those in this embodiment.

As shown in FIG. 2A , step S101 includes: performing a first pressing operation to form an inner circuit structure 110 that is pressed once. The inner circuit structure 110 is formed by etching inner circuit patterns 116 on both sides of a plurality of inner core substrates 114 (FR4 substrates) coated with copper foil, and pressing them together through at least one inner adhesive layer 115 through a single pressing operation. The inner circuit structure 110 has a first bonding surface 110a and a second bonding surface 110b located on opposite sides.

As shown in FIG. 2B , the step S102 includes: performing a first drilling operation to form a first drilling hole 111 penetrating the first joint surface 110a and the second joint surface 110b in the inner layer circuit structure 110, which has a first aperture D1.

As shown in FIG. 2C , step S103 includes: performing a first electroplating operation to form a first electroplated conductive layer 112 on an inner wall of the first drill hole 111. In addition to being formed on the inner wall of the first drill hole 111, the first electroplated conductive layer 112 also extends to form on the first joint surface 110a and the second joint surface 110b of the inner layer circuit structure 110. The first electroplated conductive layer 112 electrically connects the multiple layers of the inner layer circuit patterns 116 of the inner layer circuit structure 110 to each other.

As shown in FIG. 2D , the step S104 includes: performing a first plugging operation to fill an inner space surrounded by the first electroplated conductive layer 112 on the inner wall of the first drilled hole 111 with a resin material 113 to prevent the Prepreg glue from entering during the secondary pressing process and causing glue shortage in the circuit.

As shown in FIG. 2E , the step S105 includes: performing a resin grinding operation to grind the resin material 113 overflowing from the first drill hole 111, so that the top surface of the resin material 113 is coplanar with the first electroplated conductive layer 112 on the first joint surface 110a of the inner layer circuit structure 110. And the bottom surface of the resin material 113 is also coplanar with the first electroplated conductive layer 112 on the second joint surface 110b of the inner layer circuit structure 110. The resin grinding operation is performed using an eight-axis grinder, but the present invention is not limited thereto.

As shown in FIG. 2F , the step S106 includes: performing a circuit formation operation to etch the first electroplated conductive layer 112 formed on the first bonding surface 110a of the inner layer circuit structure 110 and the first electroplated conductive layer 112 formed on the second bonding surface 110b into a circuit pattern through a lithography process, but the present invention is not limited thereto.

As shown in FIG. 2G , step S107 includes: performing a browning process to form a browning surface S on the first electroplated conductive layer 112 on the first bonding surface 110a of the inner layer circuit structure 110 and the first electroplated conductive layer 112 on the second bonding surface 110b. The browning surface S can be used to enhance the bonding strength between the two outer layer circuit structures and the inner layer circuit structure 110 in the secondary pressing process.

As shown in FIG. 2H , the step S108 includes: performing a second pressing operation to press the two outer circuit structures 120 symmetrically onto the first joint surface 110a and the second joint surface 110b of the inner circuit structure 110 through secondary pressing.

As shown in FIG. 2I , the step S109 includes: performing a second drilling operation to form a second drilling hole 121 on one of the two outer circuit structures 120 (such as the upper outer circuit structure 120 in FIG. 2I ) toward the inner circuit structure 110. The second drilling hole 121 corresponds to the first drilling hole 111 in position, and the second drilling hole 121 has a second hole diameter D2 greater than the first hole diameter D1.

As shown in FIG. 2J , the step S110 includes: performing a second electroplating operation to form a second electroplated conductive layer 122 on an inner wall of the second drill hole 121, and the second electroplated conductive layer 122 is directly connected to the first electroplated conductive layer 112 to be electrically connected to each other.

As shown in FIG. 2K , the step S111 includes: performing a second plugging operation to fill an inner space surrounded by the second electroplated conductive layer 122 with a solder mask ink 123 .

[Beneficial effects of the embodiment]

The printed circuit board with a symmetrical pressing structure and the manufacturing method thereof provided by the present invention can meet the customer's demand for a product with a blind hole structure, and can further solve the problem of board bending without increasing the thickness of the board of the original stacking design.

The above disclosed contents are only the preferred feasible embodiments of the present invention, and do not limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made by using the contents of the description and drawings of the present invention are included in the scope of the patent application of the present invention.

100:Printed circuit board

110: Inner circuit structure

110a: first joint surface

110b: Second joint surface

111: First drilling hole

112: First electroplating conductive layer

113: Resin material

114: Inner core substrate

115: Inner adhesive layer

116: Inner circuit pattern

D1: First aperture

120: Outer layer circuit structure

121: Second drilling hole

122: Second electroplating conductive layer

123: Solder mask ink

124: Outer dielectric substrate

125: Outer adhesive layer

126: Outer layer circuit pattern

D2: Second aperture

H: Electroplated vias

V: Laser blind via

Claims (11)

A printed circuit board with a symmetrical pressed structure comprises: an inner layer circuit structure; wherein the inner layer circuit structure is formed by a single press, the inner layer circuit structure has a first drill hole penetrating a first joint surface and a second joint surface thereof, the first drill hole is a mechanical drill hole, the first drill hole has a first aperture, and a first electroplated conductive layer is formed on an inner side wall of the first drill hole; and two outer layer circuit structures, which are symmetrically pressed to the inner layer circuit structure by a secondary press. On the first joint surface and the second joint surface; wherein one of the two outer layer circuit structures has a second drill hole, the second drill hole is a mechanical drill hole, the second drill hole corresponds to the first drill hole in position, the second drill hole is a blind hole connected to the first drill hole, the second drill hole has a second hole diameter greater than the first hole diameter, and an inner side wall of the second drill hole is formed with a second electroplated conductive layer directly connected to the first electroplated conductive layer. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein the two outer layer circuit structures are symmetrically pressed onto the first joint surface and the second joint surface of the inner layer circuit structure, respectively, thereby reducing the bending degree of the printed circuit board. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein, among the two outer circuit structures, the outer circuit structure disposed on the first joint surface of the inner circuit structure has the second drill hole, and an outer dielectric substrate of the outer circuit structure disposed on the second joint surface of the inner circuit structure is formed of a high-frequency material. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein, among the two outer layer circuit structures, the outer layer circuit structure disposed on the first joint surface of the inner layer circuit structure has the second drill hole, and an outer layer dielectric substrate of the outer layer circuit structure having the second drill hole is formed of a high frequency material. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein the first electroplated conductive layer is used to electrically connect the multi-layer circuits of the inner layer circuit structure, and an inner space surrounded by the first electroplated conductive layer is filled with a resin material. A printed circuit board with a symmetrical pressed structure as described in claim 5, wherein the first drill hole of the inner layer circuit structure and the first electroplated conductive layer formed on the inner side wall of the first drill hole are buried between the two outer layer circuit structures, and the second drill hole is a blind hole connected to the first drill hole. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein the printed circuit board has a plated through hole vertically penetrating the inner layer circuit structure and the two outer layer circuit structures; wherein at least one of the two outer layer circuit structures has a laser blind hole. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein the second electroplated conductive layer is used to electrically connect the different layers of the corresponding outer layer circuit structure, and is further electrically connected to the first electroplated conductive layer; wherein an inner space surrounded by the second electroplated conductive layer is filled with a solder mask ink. A printed circuit board with a symmetrical pressed structure as described in claim 1, wherein, in a projection area projected along a normal vector of the printed circuit board, a first outer contour of the first drill hole falls inside a second outer contour of the second drill hole. A method for manufacturing a printed circuit board with a symmetrical pressed structure, comprising: performing a first pressing operation to form an inner layer circuit structure which has a first joint surface and a second joint surface located on opposite sides after a first pressing operation; performing a first drilling operation to form a first drill hole which penetrates the first joint surface and the second joint surface in the inner layer circuit structure, and has a first aperture; wherein the first drill hole is a mechanical drill hole; performing a first electroplating operation to form a first electroplated conductive layer on an inner side wall of the first drill hole; performing a second pressing operation to symmetrically press two outer layer circuit structures to the inner layer circuit structure through a second pressing operation; The first joint surface and the second joint surface of the circuit structure are formed on the first joint surface of the circuit structure; a second drilling operation is performed to form a second drill hole on one of the two outer circuit structures; wherein the second drill hole is a mechanical drill hole, the second drill hole corresponds to the first drill hole in position, the second drill hole is a blind hole connected to the first drill hole, and the second drill hole has a second hole diameter greater than the first hole diameter; and a second electroplating operation is performed to form a second electroplated conductive layer on an inner side wall of the second drill hole, and the second electroplated conductive layer is directly connected to the first electroplated conductive layer to be electrically connected to each other. The method for manufacturing a printed circuit board as described in claim 10 further comprises: performing a first plugging operation between the first electroplating operation and the second pressing operation to fill an inner space surrounded by the first electroplated conductive layer on the inner wall of the first drilled hole with a resin material; and performing a second plugging operation after the second electroplating operation to fill an inner space surrounded by the second electroplated conductive layer on the inner wall of the second drilled hole with a solder resist ink.