Printed wiring board having cavities and method of manufacturing the same

Abstract

The application provides a manufacturing method of a printed circuit board with a cavity, comprising the following steps: S1, providing a hard board layer of the printed circuit board; S2, forming a conductive post by filling metal into a laser hole on the hard board layer; S3, laminating the hard board layer, a prepreg and a copper foil to obtain a four-layer printed circuit board; S4, forming a conductive post by filling metal into a laser hole on the four-layer printed circuit board, and setting a prepreg and a copper foil on both sides of the four-layer printed circuit board to form a six-layer printed circuit board; S5, repeating step S4 twice to obtain a ten-layer board, forming a conductive post by filling metal into a laser hole on the ten-layer board, and setting a conductive hole on one side of the ten-layer board to obtain a ten-layer printed circuit board by copper plating; S6, forming a cavity by depth forming a cavity body through a cavity forming machine in a cavity area; and S7, accurately drilling a hole downward along the bottom of the cavity body to the upper surface of the hard board to form the cavity. The application can effectively save the laser window burning operation time, and reduce the reliability abnormality of the board surface bulging caused by excessive laser window burning energy.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board processing technology, and in particular to a cavity in a printed circuit board and its manufacturing method. Background Technology

[0002] The part numbers of existing PCB cavity designs are becoming increasingly complex, and the cavity area on the board surface is not only large, but also increasingly deep.

[0003] Existing PCB cavities have the following disadvantages: 1. High production cost: Due to the specified depth and short distance between the cavity edge and the rigid board forming edge, the required precision of the specified cavity area on the board surface is high. Conventional designs use CO2 lasers to directly burn out the required patterns; 2. Long production cycle: The cavity area is made by stacking laser apertures. The larger the cavity and the deeper the hole, the more laser energy and the more laser shots are required, which means that the laser production time is longer; 3. Prone to board breakage during production: Since the deeper the cavity, the more laser energy and the more laser shots are required, the higher the energy at the bottom of the cavity will be. When the energy is high enough, the copper surface at the bottom of the cavity will be overheated, causing the board to break and bulge. Summary of the Invention

[0004] The purpose of this invention is to overcome and supplement the deficiencies in the existing technology, and to provide a cavity in a printed circuit board and its manufacturing method, which effectively saves laser window burning operation time and reduces the reliability abnormality caused by excessive laser burning energy leading to board surface bulging.

[0005] The technical solution adopted in this invention is: A method for manufacturing a printed circuit board with a cavity, wherein: S1. A rigid board layer for a printed circuit board is provided, the rigid board layer including a rigid board and rigid board copper foil disposed on the upper and lower surfaces of the rigid board; S2. Drill laser holes on the rigid board layer, fill the laser holes with metal to form conductive pillars, and make circuit patterns on the rigid board copper foil. S3. Provide prepreg and copper foil. Set prepreg on both the upper and lower surfaces of the rigid board layer. Set copper foil on the surface of the prepreg away from the rigid board layer. Press the rigid board layer, prepreg, and copper foil together according to the final structure of the printed circuit board to obtain a four-layer printed circuit board. S4. Drill laser holes on the upper and lower surfaces of the four-layer printed circuit board, fill the laser holes with metal to form conductive pillars, and make circuit patterns on copper foil. Then, set prepreg on both sides of the four-layer printed circuit board, and set copper foil on the surface of the prepreg away from the printed circuit board to form a six-layer printed circuit board. S5. Repeat step S4 twice to obtain a ten-layer board. Drill laser holes on the upper and lower surfaces of the ten-layer board, fill the laser holes with metal to form conductive pillars, and set a conductive hole on one side of the ten-layer board. Plate copper on the inner wall of the conductive hole, and then make circuit patterns on the copper foil of the top and bottom layers to obtain a ten-layer printed circuit board. S6. Design the cavity area of ​​the ten-layer printed circuit board, and form the cavity at a fixed depth using a blind forming machine at the location of the cavity area. The cavity width is >0.6mm. S7. A cavity is formed by precisely drilling a hole from the bottom of the cavity downwards to the top surface of the hard plate using a laser machine.

[0006] Preferably, in the method for manufacturing the printed circuit board with a cavity, the cavity depth is greater than 0.25 mm.

[0007] Preferably, in the method for manufacturing the printed circuit board with a cavity, the cavity is at a fixed depth of 2-4 mil to the upper surface of the hard board.

[0008] A printed circuit board with a cavity, comprising: a rigid board layer, a prepreg, and copper foil; the rigid board layer includes a rigid board and rigid copper foil disposed on the upper and lower surfaces of the rigid board, with circuits on the rigid copper foil; prepregs are disposed on both sides of the rigid copper foil, and copper foil is disposed on the side of the prepregs away from the rigid board layer; prepregs are disposed between adjacent copper foils; copper foil is disposed at the top and bottom of the printed circuit board; laser holes are disposed on adjacent copper foils and prepregs; metal is filled into the laser holes to form conductive pillars; a conductive pillar is disposed on one side of the printed circuit board; copper is plated on the inner wall of the conductive pillar; circuit patterns are disposed on the copper foil; and a cavity is formed in the depth direction of the printed circuit board.

[0009] Preferably, in the cavity printed circuit board, the number of layers of the prepreg is 8.

[0010] Preferably, in the cavity printed circuit board, the copper foil has 8 layers.

[0011] Preferably, the printed circuit board with a cavity is wherein at least one circuit pattern is exposed on the side wall of at least one rigid plate constituting the cavity region.

[0012] Advantages of this invention: (1) The method for manufacturing a cavity printed circuit board of the present invention manufactures a cavity printed circuit board by combining blind forming and laser burning process. This can effectively save laser burning operation time and reduce the reliability abnormality caused by excessive laser burning energy leading to board surface bulging. It can meet the different cavity depth requirements of customers, adapt to and meet the needs of modern process, and meet the customers' subsequent needs for larger and deeper cavities.

[0013] (2) The manufacturing method of the printed circuit board with cavity of the present invention uses laser direct burning of windows, which takes a long time and has poor board surface reliability. The current process of combining blind forming and laser burning can effectively reduce the laser burning time and avoid excessive laser energy causing bubbles on the board surface. Blind forming is not a simple blind forming equipment. The blind forming equipment uses optical principles to capture light spots to ensure that the offset between blind forming and laser burning is small. When the customer's cavity depth is >10mil and cavity width is >24mil, the blind forming + laser burning process can effectively reduce the product production time and reduce board reliability abnormalities. This combined process can effectively keep up with the increasingly stringent product quality requirements of customers and meet customer needs. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the rigid plate layer in Embodiment 1 of the present invention.

[0015] Figure 2 This is a schematic diagram of drilling laser holes on a rigid plate layer according to Embodiment 1 of the present invention.

[0016] Figure 3 This is a schematic diagram of a conductive post formed on a rigid plate layer in Embodiment 1 of the present invention.

[0017] Figure 4 This is a schematic diagram of the circuit pattern fabricated on the rigid copper foil of Embodiment 1 of the present invention.

[0018] Figure 5 This is a schematic diagram of a four-layer printed circuit board according to Embodiment 1 of the present invention.

[0019] Figure 6 This is a schematic diagram of drilling laser holes on the rigid layer of a four-layer printed circuit board according to Embodiment 1 of the present invention.

[0020] Figure 7 This is a schematic diagram of the conductive pillars formed on the rigid layer of a four-layer printed circuit board according to Embodiment 1 of the present invention.

[0021] Figure 8 This is a schematic diagram of the fabrication of circuit patterns on the rigid copper foil of a four-layer printed circuit board according to Embodiment 1 of the present invention.

[0022] Figure 9 This is a schematic diagram of a six-layer printed circuit board according to Embodiment 1 of the present invention.

[0023] Figure 10 This is a schematic diagram of a ten-layer plate according to Embodiment 1 of the present invention.

[0024] Figure 11 This is a schematic diagram of a conductive post set on a ten-layer plate according to Embodiment 1 of the present invention.

[0025] Figure 12This is a schematic diagram of copper plating on the inner wall of the conductive pillar on the ten-layer plate of Embodiment 1 of the present invention.

[0026] Figure 13 This is a schematic diagram of a cavity set on a ten-layer printed circuit board according to Embodiment 1 of the present invention.

[0027] Figure 14 This is a schematic diagram of the printed circuit board with a cavity according to the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0029] Example 1 like Figure 1-14 A method for manufacturing a printed circuit board with a cavity, wherein: S1. Provide a rigid board layer 1 for a printed circuit board, the rigid board layer including a rigid board 1-1 and rigid board copper foil 1-2 disposed on the upper and lower surfaces of the rigid board 1-1; S2. Drill laser holes 1-3 on the rigid board layer 1, fill the laser holes 1-3 with metal to form conductive pillars 1-4, and make circuit patterns on the rigid board copper foil 1-2. S3. Provide a prepreg 2 and a copper foil 3. Set the prepreg 2 on both the upper and lower surfaces of the rigid board layer 1. Set the copper foil 3 on the surface of the prepreg 2 away from the rigid board layer 1. Press the rigid board layer 1, the prepreg 2 and the copper foil 3 together according to the final structure of the printed circuit board to obtain a four-layer printed circuit board. S4. Drill laser holes 1-3 on the upper and lower surfaces of the four-layer printed circuit board, fill the laser holes 1-3 with metal to form conductive pillars 1-4, and make circuit patterns on copper foil 3. Then, set prepreg 2 on both sides of the four-layer printed circuit board, and set copper foil 3 on the surface of the prepreg 2 away from the printed circuit board to form a six-layer printed circuit board. S5. Repeat step S4 twice to obtain a ten-layer board. Drill laser holes 1-3 on the upper and lower surfaces of the ten-layer board. Fill the laser holes 1-3 with metal to form conductive pillars 1-4. Set a conductive hole 5 on one side of the ten-layer board. Plate copper on the inner wall of the conductive hole 5. Then make circuit patterns on the copper foil 3 of the uppermost and lowermost layers to obtain a ten-layer printed circuit board. S6. Design the cavity area of ​​the ten-layer printed circuit board, and form the cavity 6 at a fixed depth using a blind forming machine at the location of the cavity area. The width of the cavity 6 is > 0.6mm. S7. Using a laser machine, precisely drill holes downwards from the bottom of cavity 6 to the upper surface of rigid plate 1-1 to form cavity 7.

[0030] The blind reaming machine is used to first extract a large portion of the required cavity depth. For example, if the required depth is L1 to L5 copper layers, with a theoretical depth of 20mil, the blind reaming machine will first extract a depth of 17mil. The use of this blind reaming + laser window burning process requires the following conditions to be met: the cavity depth generally needs to be greater than 10mil. If the designed depth is too small, laser window burning can be used for direct production. The cavity width needs to be greater than the width of the 0.6mm milling cutter, because the minimum forming milling cutter is 0.6mm, so the window pattern cannot be smaller than 0.6mm.

[0031] The residual thickness of the cavity area is burned out using a laser machine to meet customer requirements; the blind reaming capability is min + / - 2mil. Blind reaming is a mechanical process, and reaming too deep will damage the copper surface at the bottom of the cavity, so a thickness of 3mil is left for laser reaming to create a window.

[0032] The blind forming process uses light spot alignment for production, and the laser window burning process also uses light spot alignment. Both the blind forming process and the laser window burning process use light spot alignment at the same time to reduce the difference between the two alignment systems. Normal processes can hardly achieve this design requirement. First, the machine capability must be considered, then the machine must be matched with the system, and finally the machine parameter design must be guaranteed.

[0033] Blind forming: CCD forming machine, the depth and width tolerance of blind forming can be controlled within 2mil (normal equipment 4mil); Laser window burning: CO2 laser machine, the window burning accuracy is controlled within 1mil; Alignment system: Both blind forming and laser window burning processes use the outer layer of light spot alignment. The two processes are produced using the same alignment system to avoid production deviation caused by different processes. Forming generally uses holes, while CCD forming can align light spots. The forming capability is generally 4mil, while CCD forming is 2mil.

[0034] Example 2 like Figure 14 A printed circuit board with a cavity, comprising: a rigid layer 1, prepreg 2, and copper foil 3; the rigid layer 1 includes a rigid board 1-1 and rigid copper foil 1-2 disposed on the upper and lower surfaces of the rigid board 1-1, with circuitry on the rigid copper foil 1-2; prepreg 2 is disposed on both sides of the rigid copper foil 1-2; copper foil 3 is disposed on the side of the prepreg 2 away from the rigid layer 1; prepreg 2 is disposed between adjacent copper foils 3; and copper foil 3 is disposed at the top and bottom of the printed circuit board. The copper foil 3 has laser holes 1-3 on adjacent copper foils 3 and prepregs 2. The laser holes 1-3 are filled with metal to form conductive pillars 1-4. A conductive hole 5 is provided on one side of the printed circuit board. The inner wall of the conductive hole 5 is plated with copper. The copper foils 3 have circuit patterns. A cavity 7 is formed in the depth direction of the printed circuit board. At least one circuit pattern is exposed on the side wall of at least one rigid plate 1-1 constituting the cavity 7 region. The prepreg 2 has 8 layers and the copper foil 3 has 8 layers.

[0035] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for manufacturing a printed circuit board with a cavity, characterized in that: Includes the following steps: S1. Provide a rigid board layer (1) for a printed circuit board, the rigid board layer including a rigid board (1-1) and rigid board copper foil (1-2) disposed on the upper and lower surfaces of the rigid board (1-1). S2. Drill laser holes (1-3) on the rigid board layer (1), fill the laser holes (1-3) with metal to form conductive pillars (1-4), and make circuit patterns on the rigid board copper foil (1-2); S3. Provide a prepreg (2) and a copper foil (3). Set the prepreg (2) on both the upper and lower surfaces of the rigid board layer (1). Set the copper foil (3) on the surface of the prepreg (2) away from the rigid board layer (1). Press the rigid board layer (1), the prepreg (2), and the copper foil (3) together according to the final structure of the printed circuit board to obtain a four-layer printed circuit board (4). S4. Drill laser holes (1-3) on the upper and lower surfaces of the four-layer printed circuit board (4), fill the laser holes (1-3) with metal to form conductive pillars (1-4), and make circuit patterns on copper foil (3). Then, set prepreg (2) on both sides of the four-layer printed circuit board, and set copper foil (3) on the surface of the prepreg (2) away from the printed circuit board to form a six-layer printed circuit board. S5. Repeat step S4 twice to obtain a ten-layer board. Drill laser holes (1-3) on the upper and lower surfaces of the ten-layer board. Fill the laser holes (1-3) with metal to form conductive pillars (1-4). Set a conductive hole (5) on one side of the ten-layer board. Plate copper on the inner wall of the conductive hole (5). Then make circuit patterns on the copper foil (3) of the uppermost and lowermost layers to obtain a ten-layer printed circuit board. S6. Design the cavity area of ​​the ten-layer printed circuit board, and form the cavity (6) at a fixed depth using a forming blind spot machine at the location of the cavity area. The width of the cavity (6) is > 0.6 mm. S7. Using a laser machine, precisely drill a hole from the bottom of the cavity (6) down to the upper surface of the hard plate (1-1) to form a cavity (7).

2. The method for manufacturing a printed circuit board with a cavity as described in claim 1, characterized in that: The cavity (6) has a depth of >0.25mm.

3. The method for manufacturing a printed circuit board with a cavity as described in claim 1, characterized in that: The cavity (6) is fixed to a depth of 2-4 mil to the upper surface of the hard plate (1-1).

4. A cavity-containing printed circuit board manufactured by the manufacturing method of a cavity-containing printed circuit board according to any one of claims 1-3, characterized in that: The circuit board includes a rigid board layer (1), a prepreg (2), and copper foil (3). The rigid board layer (1) includes a rigid board (1-1) and a rigid copper foil (1-2) disposed on the upper and lower surfaces of the rigid board (1-1). The rigid copper foil (1-2) has circuits. Prepregs (2) are disposed on both sides of the rigid copper foil (1-2). Copper foil (3) is disposed on the side of the prepreg (2) away from the rigid board layer (1). Prepregs (2) are disposed between adjacent copper foils (3). Copper foil (3) is disposed at the top and bottom of the printed circuit board. Laser holes (1-3) are disposed on adjacent copper foils (3) and prepregs (2). Metal is filled in the laser holes (1-3) to form conductive pillars (1-4). Conductive holes (5) are disposed on one side of the printed circuit board. Copper is plated on the inner wall of the conductive holes (5). The copper foils (3) have circuit patterns. A cavity (7) is formed in the depth direction of the printed circuit board.

5. The printed circuit board with a cavity as described in claim 4, characterized in that: The semi-cured sheet (2) has 8 layers.

6. The printed circuit board with a cavity as described in claim 4, characterized in that: The copper foil (3) has 8 layers.

7. The printed circuit board with a cavity as described in claim 4, characterized in that: At least one circuit pattern is exposed on the side wall of at least one rigid plate (1-1) constituting the cavity (7) region.

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