A manufacturing method of a foldable embedded PCB and the PCB

Abstract

The application discloses a manufacturing method of a bendable embedded PCB and the PCB, and belongs to the technical field of PCB manufacturing. The manufacturing method comprises the following steps: single module preparation; pad preparation; sub-board preparation, the middle layer and the single module staggered lamination of the interlayer are laminated to form a sub-board, the middle layer of the left and right parts is a prepreg and an anti-adhesion sheet respectively; mother board preparation, the core board and the prepreg constituting the mother board are pretreated according to the size of the sub-board, so that the core board and the prepreg are staggered laminated to form a cavity; the sub-board is vertically embedded into the groove when the core board and the prepreg constituting the mother board are staggered laminated, and then the whole is laminated with the prepreg and the copper foil to form the mother board; layer-increasing plate preparation, the layer-increasing plate is laminated on the sidewall of the corresponding pad of the mother board, the BGA chip and the optical module are arranged on the layer-increasing plate, and the BGA chip and the optical module are connected and conducted with the pad through the laser hole arranged on the layer-increasing plate. The application realizes the electrical interconnection between the BGA chip and more optical modules through the vertical wiring of the sub-board and the optimization of the circuit layout.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a method for manufacturing a bendable embedded PCB and the PCB itself. Background Technology

[0002] In PCB design, BGA chips are typically electrically interconnected with multiple optical modules via multi-layer traces. The number of PCB trace layers is primarily determined by the arrangement of high-speed lines in the BGA chip's signal layers. Generally, each row of high-speed lines starts from the BGA pads, connects to the corresponding optical module, and is connected row by row using build-up technology. This design approach has a significant problem: when the innermost row of pads of the BGA chip connects to the high-speed lines, a relatively long neckdown area is required, which increases signal integrity (SI) loss. Furthermore, when more optical modules need to be connected, the number of BGA pads and build-up layers often needs to be increased to bring out more high-speed lines, resulting in limited routing space and consequently increasing the overall PCB size. As the number of components integrated on a PCB continues to increase, and the requirements for overall size become more stringent (smaller and thinner), engineers often have to reduce line width and spacing to achieve higher-density routing. However, this practice significantly increases SI loss, thus adversely affecting the long-term performance and reliability of the PCB product. While ensuring the integrity of SI signals, how to achieve electrical interconnection between PCB board BGA chips and more optical modules is an important issue. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for manufacturing a bendable embedded PCB and a PCB itself, solving the technical problem of how to achieve electrical interconnection between the PCB board BGA chip and more optical modules while ensuring SI signal integrity.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0005] In a first aspect, the present invention provides a method for manufacturing a bendable embedded PCB, comprising:

[0006] The single module is fabricated by stacking and laminating a signal layer and a ground layer in an alternating manner. One sidewall of the single module perpendicular to the ground layer is designated as the calibration sidewall. The two ends of the lines in the signal layer are located at the two ends of the calibration sidewall.

[0007] The pad preparation involves electroplating copper and tin onto the calibration sidewall of the single module, burning out the pads for the ground and signal layers through a tin-burning process, etching away the bottom copper of the calibration sidewall through an etching process, and finally performing a tin-removal process.

[0008] Sub-board fabrication involves laminating the intermediate layer and the single module in an alternating manner to form a sub-board. The sub-board is divided into left and right parts, with the intermediate layers of the left and right parts being a prepreg and an anti-adhesion sheet, respectively. The pads on the single module located on the left side of the sub-board are used to connect with the BGA chip, and each pad on the single module located on the right side of the sub-board is used to connect with an optical module.

[0009] The motherboard is prepared by pre-treating the core board and prepreg that make up the motherboard according to the size of the daughter board, so that they are staggered and stacked to form a cavity groove; when the core board and prepreg that make up the motherboard are staggered and stacked, the daughter board is vertically embedded into the cavity groove, the calibration sidewall is located at the opening of the cavity groove, and then the prepreg and copper foil are stacked together and pressed to form the motherboard;

[0010] The enhancement layer is fabricated by laminating the enhancement layer onto the sidewall of the motherboard corresponding to the pads. The BGA chip and the optical module are disposed on the enhancement layer and connected to the pads through laser holes opened on the enhancement layer.

[0011] Optionally, the lines in the signal layer are U-shaped differential pairs with a line spacing of 3 times the line width.

[0012] Optionally, the single module includes a first ground layer, an intermediate signal layer and a second ground layer stacked together, or a first ground layer, a first intermediate signal layer, a second ground layer, a second intermediate signal layer and a third ground layer stacked together.

[0013] Optionally, after electroplating the calibration sidewall with copper and tin, the single module may be integrally formed by milling according to the design dimensions.

[0014] Optionally, the step of forming the single module as a whole by milling also includes forming protrusions at both ends of the single module, and the pretreatment of the core board and prepreg that make up the mother board also includes forming a groove in the Cavity groove to fix the protrusions.

[0015] Optionally, the anti-adhesion sheet is a release film.

[0016] Optionally, during the pressing process to form the mother plate, the prepreg is partially mixed and pressed to allow the prepreg to flow and fill the Cavity groove to fix the subplate.

[0017] Optionally, when the add-on board is multi-layered, the BGA chip and the optical module are connected to the pads on the sub-board through laser-drilled vias.

[0018] Secondly, the present invention provides a PCB manufactured using the manufacturing method described above.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0020] This invention provides a method for manufacturing a bendable embedded PCB and the PCB itself. During the sub-board lamination process, a prepreg and an anti-adhesion sheet are used to make one part of the sub-board a multi-layer rigid board and the other part a flexible board dispersed into multiple modules. The flexible board can be bent within a certain range. The sub-board is vertically embedded into the cavity groove of the mother board. After lamination, BGA chips and optical modules are respectively connected through laser holes, ultimately realizing electrical interconnection between different areas of the PCB. The multi-layer rigid board part is connected to the BGA chip, and each flexible board is connected to an optical module. By using laser-stacked vias and vertical routing on the sub-board, horizontal wiring is changed to vertical wiring, optimizing the circuit layout and improving wiring density. The laser-stacked vias shorten the signal transmission path, solving the problem of limited space for long-distance high-density wiring, and enabling electrical interconnection between BGA chips and more optical modules. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the manufacturing method of a bendable embedded PCB provided in an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the signal layer cross-section of a single module provided in an embodiment of the present invention;

[0023] Figure 3 This is a side view of a single module provided in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the sub-plate pressing provided in an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the slotting of the motherboard provided in an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of the motherboard pressing provided in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the connection and conduction of a bendable embedded PCB provided in an embodiment of the present invention;

[0028] Figure 8 This is a three-dimensional schematic diagram of a bendable embedded PCB provided in an embodiment of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Example 1:

[0033] like Figure 1 As shown, this embodiment of the invention provides a method for manufacturing a bendable embedded PCB, including the following steps:

[0034] Step S1: Single module fabrication. The signal layer and ground layer are stacked and laminated in an alternating manner to form a single module. One sidewall of the single module perpendicular to the ground layer is designated as the calibration sidewall. The two ends of the lines in the signal layer are located at the two ends of the calibration sidewall.

[0035] The number of layers in a single module can be set to 3, 5, or more as required. A 3-layer module includes a first ground layer, an intermediate signal layer, and a second ground layer. A 5-layer module includes a first ground layer, a first intermediate signal layer, a second ground layer, a second intermediate signal layer, and a third ground layer. In this specific embodiment, a 3-layer single module is used as an example.

[0036] like Figure 2 As shown, the lines in the signal layer are U-shaped differential pairs, with a spacing of 3 times the line width. The wiring density is controlled by adjusting the line spacing, thereby regulating SI loss.

[0037] Step S2: Pad preparation. The calibration sidewall of the single module is electroplated with copper and tin. The pads leading out of the ground layer and signal layer are burned out by tin burning. Then, the bottom copper of the calibration sidewall is etched away by etching. Finally, the tin is removed.

[0038] Tin burning treatment, such as laser tin burning; etching treatment, such as alkaline etching.

[0039] After electroplating copper and tin onto the calibration sidewalls, the process also includes machining the single module as a whole using a milling cutter according to the design dimensions. For example... Figure 3 As shown, the length of the second single module is less than that of the first and third single modules.

[0040] Step S3: Sub-board preparation. The intermediate layer and single module are stacked and laminated to form a sub-board. The sub-board is divided into two parts, left and right. The intermediate layers of the left and right parts are a prepreg and an anti-adhesion sheet, respectively. The pads on the single module on the left side of the sub-board are used to connect with the BGA chip, and each pad on the single module on the right side of the sub-board is used to connect with an optical module.

[0041] The anti-adhesion sheet mainly serves to prevent adjacent single modules from sticking together during the pressing process. The protective layer is a release film or other protective material.

[0042] like Figure 4 As shown, taking the lamination of three single modules into a sub-board as an example, after lamination, part D is a multi-layer rigid board, and part E is a flexible board that is dispersed into multiple modules and can be bent within a certain range. Each module corresponds to an optical module. Therefore, the number of optical modules connected to the BGA chip determines the number of single modules in the sub-board.

[0043] Step S4: Motherboard preparation. According to the size of the daughterboard, the core board and prepreg that make up the motherboard are pretreated so that they are staggered and stacked to form a Cavity groove. When the core board and prepreg that make up the motherboard are staggered and stacked, the daughterboard is vertically embedded into the Cavity groove, and the sidewall is marked at the opening of the Cavity groove. Then the prepreg and copper foil are stacked together and pressed to form the motherboard.

[0044] like Figure 5 As shown, the width of Cavity-1 slot is equal to the thickness of the sub-board, and the length of Cavity-1 slot is equal to the length of part D of the sub-board. Cavity-2 slot has an irregular arc structure, with the width of slot equal to the thickness of each module and the length of slot equal to the length of part E of each module.

[0045] like Figure 6 As shown, the sub-board is vertically embedded into the Cavity groove (sidewall facing upwards), with part D embedded in Cavity-1 groove and part E embedded in Cavity-2 groove. Then, the PP and copper foil are stacked together to complete the pressing. The semi-cured sheet is flowed into the Cavity groove to fill the sub-board through local mixing and pressing to fix it.

[0046] To facilitate fixing the position of the single module, the single module is integrally formed by milling, which also includes forming protrusions at both ends of the single module. The pretreatment of the core board and prepreg that make up the mother board also includes forming grooves for fixing the protrusions in the Cavity groove.

[0047] Step S5: Add-on board preparation. The add-on board is laminated onto the sidewall of the corresponding pad on the motherboard. The BGA chip and optical module are placed on the add-on board and connected to the pad through the laser holes opened on the add-on board.

[0048] After the motherboard is prepared, an add-on board is needed to connect it to the BGA chip and optical module. The pattern circuits of the BGA chip area and the optical module area are made on the add-on board and connected to the pads through laser holes.

[0049] When the add-on board is multilayered, the BGA chip and optical module are connected to the pads on the daughterboard via laser-drilled vias or POFV vias. The number of layers and the type of vias on the add-on board can be set according to actual needs.

[0050] like Figure 7 As shown, taking a three-layer add-on panel as an example,

[0051] (1) After the first pressing, laser holes are made to connect the first layer of the superposition board and the sub-board, and then electroplating and graphic circuit fabrication are carried out.

[0052] (2) Secondary lamination, to make laser holes that connect the second layer of the superposition plate to the first superposition plate, to stack the laser drilled holes, and then to perform electroplating and graphic circuit fabrication.

[0053] (3) Three-stage lamination is performed to create laser holes that connect the third layer of the superposition plate to the second superposition plate. Laser drilling is then performed on the superposition plate, followed by electroplating and graphic circuit fabrication.

[0054] After the above graphic circuit is completed, as follows: Figure 8 As shown, the BGA chip area and the optical module area on the PCB are electrically interconnected through laser-drilled vias and vertical traces on the sub-board.

[0055] Example 2:

[0056] Based on the manufacturing method provided in Embodiment 1, this embodiment of the invention provides a PCB manufactured using the above-described manufacturing method.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing a foldable embedded PCB, characterized in that, The method comprises the following steps: Single module preparation: interleaving and laminating a signal layer and a ground layer to form a single module, and recording one side wall of the ground layer as a calibration side wall, and two ends of a circuit in the signal layer are located at two ends of the calibration side wall respectively; Pad preparation: electroplating copper and tin on the calibration side wall of the single module, burning out the pads of the ground layer and the circuit in the signal layer through tin burning treatment, etching away the bottom copper of the calibration side wall through etching treatment, and finally performing tin stripping treatment; Subboard preparation: interleaving and laminating an intermediate layer and the single module to form a subboard, the subboard is divided into left and right parts, and the intermediate layers of the left and right parts are prepreg and anti-adhesion sheet respectively; the pads on the single module in the left part are used for connecting with a BGA chip, and each pad on the single module in the right part is used for connecting with an optical module; Motherboard preparation: pretreating a core plate and a prepreg constituting a motherboard according to the size of the subboard, so that the core plate and the prepreg form a Cavity groove after being interleaved and laminated; vertically embedding the subboard into the Cavity groove when interleaving and laminating the core plate and the prepreg constituting the motherboard, and the calibration side wall is located at the opening of the Cavity groove, and then laminating the prepreg and a copper foil to form the motherboard; Layer-increasing plate preparation: laminating a layer-increasing plate on the side wall corresponding to the pad of the motherboard, and the BGA chip and the optical module are arranged on the layer-increasing plate and connected with the pad through a laser hole.

2. The method of claim 1, wherein, The circuit in the signal layer is a U-shaped differential double line, and the line spacing is 3 times the line width.

3. The method of claim 1, wherein the method further comprises: The single module comprises a first ground layer, an intermediate signal layer and a second ground layer which are laminated, or a first ground layer, a first intermediate signal layer, a second ground layer, a second intermediate signal layer and a third ground layer which are laminated.

4. The method of claim 1, wherein the method further comprises: After electroplating copper and tin on the calibration side wall, the method further comprises machining the single module as a whole according to the design size through a milling cutter.

5. The method of claim 4, wherein the method further comprises: The machining the single module as a whole through the milling cutter further comprises forming a protrusion at the end of the single module, and the pretreating the core plate and the prepreg constituting the motherboard further comprises forming a groove in the Cavity groove for fixing the protrusion.

6. The method of claim 1, wherein, The anti-adhesion sheet is a release film.

7. The method of claim 1, wherein the method further comprises: When laminating to form the motherboard, the prepreg flows and fills into the Cavity groove to fix the subboard through local mixed lamination.

8. The method of claim 1, wherein the method further comprises: When the layer-increasing plate is multi-layered, the BGA chip and the optical module are connected with the pad on the subboard through a laser stacking hole.

9. A PCB characterized by, The method is made by the manufacturing method in any one of claims 1-8.

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