A method for fabricating embedded device PCBs

Abstract

This invention discloses a method for processing embedded component PCBs, relating to the PCB industry, including the following steps: pad fabrication, component placement, core board provision, stacking, lamination, peeling, etching, solder mask removal and desoldering, and post-processing. In this invention, after solder mask removal and desoldering, prepreg is used to fill the bottom of the component and the desoldered area of ​​the pad with adhesive, effectively solving the problem of voids in the adhesive filling at the bottom of the component. This avoids delamination between the solder mask layer and the PCB, and after a single lamination and peeling process, two embedded component substrates can be directly processed, improving production efficiency.

Description

Technical Field

[0001] This invention relates to the field of PCBs, and in particular to a method for processing embedded device PCBs. Background Technology

[0002] Embedding electronic components inside the PCB enables high-density miniaturization, while shortening the line length between components, reducing transmission losses, effectively reducing the size of the printed circuit board, reducing a large number of solder joints on the printed circuit board surface, thereby improving the reliability of the package, reducing costs, and providing better product confidentiality.

[0003] Existing device embedding technologies mainly include:

[0004] 1. The process involves fabricating circuitry using an inner core board, printing solder mask, SMT soldering components, and laminating prepreg or core board grooves after milling. The resulting product is as follows: Figure 11 The structure shown is as follows. This method involves directly pressing the solder mask layer into the finished embedded component printed circuit board after printing. Because the surface of the soldering ink is relatively smooth and has a different coefficient of expansion than resin materials such as prepreg, delamination and delamination are prone to occur after pressing. Furthermore, due to the very small gap between the bottom of the component and the carrier board after soldering, voids can easily appear when applying PP adhesive or filling with high-temperature resistant adhesive, significantly impacting the reliability of the PCB. For example, in the invention patent "A Processing Technology for Embedded Embedded Component Printed Circuit Board," application number 202010300991.0, the solder mask layer is directly pressed into the finished board after soldering the components. The soldering ink, solder paste, and solder resist remain in the printed circuit board. Simultaneously, when filling with high-temperature adhesive, the small gap between the bottom of the component and the carrier board makes it difficult to fill, posing a risk of voids and delamination, affecting the reliability of subsequent products.

[0005] 2. Embedded components are peeled off after soldering and embedded into the circuit board, then filled with adhesive. This method requires individual peeling and embedding of each component, resulting in low processing efficiency. For example, in the invention patent application number 202011197915.8, the embedded components require multiple peelings of the substrate. Furthermore, the components are small in size and numerous, making peeling difficult and inefficient, hindering mass production. Additionally, the alignment accuracy of the embedded components during lamination is difficult to guarantee, affecting subsequent component positioning. Summary of the Invention

[0006] The purpose of this invention is to provide a method for processing embedded PCBs to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for processing embedded component PCBs, comprising the following steps:

[0008] S1. Making pads: Provide a carrier board, make solder mask layers on the front and back of the carrier board, and make solder mask openings on the solder mask layers on the front and back of the carrier board according to the pad pattern. The carrier board includes a support substrate, a first copper foil layer located on the front and back of the support substrate, an adhesive layer, and a separable second copper foil layer. The second copper foil layer is bonded to the first copper foil layer by the adhesive layer.

[0009] S2, Surface Mount: Print solder paste on the corresponding pads on the front and back sides of the carrier board. The thickness of the solder paste is 5μm to 25μm, and then mount the components.

[0010] S3. Provide core board: Provide a first core board and a second core board. According to the position of the pads on the front and back of the carrier board, mill grooves on the first core board and the second core board to process slots for embedding components.

[0011] S4, Stacking: The first core board is placed on the front side of the support plate, and the second core board is placed on the back side of the support plate, so that the components are placed in the slots one by one. The filler is filled into the slots on the first core board and the second core board to process the board to be pressed.

[0012] S5. Pressing: Add layers to the plates to be pressed according to the stacking sequence, and press them together to produce the plates to be peeled off.

[0013] S6. Peeling: Peel the board to be peeled off to remove two embedded component substrates.

[0014] S7. Etching, Solder Mask Removal and Tin Stripping: Removes the second copper foil layer, solder mask layer, solder paste and flux residue from the embedded component substrate;

[0015] S8. Post-processing: Layer stacking is performed according to the stacking sequence, and the prepreg is bonded to the surface after desoldering and then pressed together. After pressing, it is processed according to conventional procedures. Laser blind vias are used to connect the circuits and the device pads to make them conductive, resulting in two embedded device printed circuit boards.

[0016] When solder paste is cured, flux remains on the medium around the pads, affecting the reliability of subsequent products. The present invention performs etching and solder resist removal after the embedded component substrate is separated from the carrier board. Solder paste and residual flux are removed by the solder stripping line, which can avoid the delamination of the solder resist layer and PCB, and effectively improve the quality of embedded component products.

[0017] Furthermore, the gap between the bottom of the component and the carrier board is small, which can easily lead to voids in the adhesive filling. After removing the solder mask, solder paste and residual flux from the bottom of the component, the voids in the adhesive filling will be exposed. The embedded component substrate, prepreg and other structural layers are pressed together according to the stacking sequence. The adhesive is then applied to the bottom of the component and the solder pad unsoldering area through the prepreg flow, which effectively solves the problem of voids in the adhesive filling at the bottom of the component and achieves high-reliability embedded component PCB manufacturing.

[0018] The present invention can directly produce two embedded component printed circuit boards through a single pressing and peeling process, thereby improving production efficiency.

[0019] Further, in step S6, the peeling process of the board to be peeled includes peeling between the second copper foil layer and the adhesive layer of the board to be peeled.

[0020] The first core board and the carrier board are peeled off, so that the second copper foil layer and the adhesive layer between the first core board and the carrier board are separated from each other, thereby forming the first embedded component substrate; the second core board and the carrier board are peeled off, so that the second copper foil layer and the adhesive layer between the second core board and the carrier board are separated from each other, thereby forming the second embedded component substrate. After one pressing and peeling process, two embedded component substrates can be directly processed, improving production efficiency.

[0021] Furthermore, step S3 also includes: the thickness of the first core board is based on the component size plus a compensation value A, and the thickness of the second core board is based on the component size plus a compensation value B, where 0.1mm ≤ compensation value A ≤ 0.15mm and 0.1mm ≤ compensation value B ≤ 0.15mm.

[0022] The thickness of the first core board and the thickness of the second core board are selected based on the thickness of the components. Grooves are milled into the first and second core boards to create slots for embedding the components. The depth of the slots in the first core board is equal to the thickness of the first core board, and the depth of the slots in the second core board is equal to the thickness of the second core board. The depth of the slots is 0.1~0.15mm greater than the thickness of the components to meet the embedding requirements of the components while saving core board material.

[0023] Furthermore, step S3 also includes: when milling grooves on the first core board and the second core board, the groove size is based on the component size plus a compensation value C, where 1mm ≤ compensation value C ≤ 5mm.

[0024] The first core board, the second core board and the prepreg used in the lamination process are milled to create slots for embedding components. The length of the slot is 1-5 mm longer than the length of the component, and the width of the slot is 1-5 mm wider than the width of the component. The size of the slot meets the embedding requirements of the component and facilitates thermosetting resin filling.

[0025] Furthermore, in step S4, the filler includes thermosetting resin, and after filling, it is checked whether the thermosetting resin is fully filled. After the check is completed, a pressure thermosetting treatment is performed in a vacuum environment.

[0026] After the first and second core boards are stacked and riveted, the slots on the first core board are filled with thermosetting resin, followed by vacuum and pressure thermosetting treatment. After the first core board on one side of the support plate has cured, the plate is flipped over to fill the second core board on the other side. After both the first and second core boards are filled with thermosetting resin, pre-cured sheets and copper foil are placed on top and bottom and pressed together. Thermosetting resin fills the gaps between the embedded components and the slots, and pre-fixes the core board and components, so that the components are initially embedded in the slots on the core board, avoiding misalignment between the components and the core board during subsequent pressing, effectively improving the embedding quality of the components.

[0027] Furthermore, in step S4, positioning holes for rivets to pass through are machined at the process edges of the first core plate, the second core plate, and the support plate. The first core plate is set on the front side of the support plate by rivets, and the second core plate is set on the back side of the support plate by rivets.

[0028] The first core board is riveted to the front of the support plate, and the second core board is riveted to the front of the support plate. Positioning holes are drilled in the first core board, the second core board, and the support plate. The positioning holes work with rivets to facilitate quick installation of the first core board and the second core board. The positioning holes also work with rivets to accurately position the first core board, the second core board, and the support plate, thereby improving product accuracy.

[0029] Furthermore, in step S5, the maximum pressing temperature is less than or equal to 200 degrees Celsius, and the pressure is 25~27 kg / cm². 2 After one side of the carrier plate is filled with adhesive and thermo-cured under pressure, the plate is flipped over, and the other side is filled with adhesive and thermo-cured under pressure before being pressed together. The maximum pressing temperature and pressure are controlled to prevent carbonization of the thermosetting resin and to avoid excessive temperature and pressure affecting the quality of the filler. The temperature is controlled to not exceed 200 degrees Celsius, and the pressure is controlled within the range of 25~27 kg / cm², allowing the thermosetting resin to pre-cur and complete curing during the pressing process. This improves production efficiency and enables high-reliability embedded component PCB fabrication.

[0030] Furthermore, in step S8, the maximum pressing temperature is less than or equal to 200 degrees Celsius, and the pressure is 25~27 kg / cm². 2 The maximum temperature of the embedded component substrate during lamination should not exceed 200 degrees Celsius, and the pressure should be between 25 and 27 kg / cm². This allows the thermosetting resin to pre-cure and fill the slots of the embedded components, preventing quality problems caused by excessive temperature and pressure.

[0031] Furthermore, in step S8, the process of stacking and pressing the layers according to the stacking sequence includes stacking the upper copper foil, prepreg, embedded component substrate, and release film in sequence.

[0032] After removing the solder mask, solder paste, and residual flux from the bottom of the component, the filler voids at the bottom of the component will be exposed. The embedded component substrate, prepreg, and other structural layers are stacked and pressed together according to the stacking sequence. The prepreg is used to fill the bottom of the component and the solder pad unsoldering area, effectively solving the problem of filler voids at the bottom of the component and achieving high-reliability embedded component PCB manufacturing.

[0033] Furthermore, the removal of the second copper foil layer, solder resist layer, and residues on the embedded component substrate includes: acid etching to remove the second copper foil layer of the embedded component substrate, alkaline solution immersion to remove the solder resist layer of the embedded component substrate, and desoldering wire treatment to remove solder paste and flux residues from the embedded component substrate.

[0034] Removing the solder mask, solder paste, and residual flux from the bottom of the component exposes the filler voids on the bottom of the component, making it easier to fill the voids with prepreg adhesive later, effectively solving the problem of filler voids on the bottom of the component.

[0035] The beneficial effects of this invention are as follows:

[0036] 1. The present invention performs solder resist removal and desoldering after the embedded component substrate is separated from the carrier board. The bottom of the component and the desoldering area of ​​the pad are filled by the prepreg flow adhesive. The solder paste and residual flux are removed by the desoldering line, which can avoid the delamination of the solder resist layer and PCB, and effectively improve the product quality of embedded components.

[0037] 2. The embedded component substrate, prepreg, and other structural layers are laminated according to the stacking sequence. The prepreg is used to fill the bottom of the component and the solder pad unsoldering area, effectively solving the problem of filling voids at the bottom of the component. This can avoid filling voids in the PCB and achieve high-reliability embedded component PCB manufacturing.

[0038] 3. The present invention can directly produce two embedded component substrates through a single pressing and peeling process, thereby improving production efficiency. Attached Figure Description

[0039] The accompanying drawings further illustrate the invention, but the embodiments in the drawings do not constitute any limitation on the invention.

[0040] Figures 1-10 This is a schematic diagram of a method for fabricating an embedded device PCB according to an embodiment of the present invention;

[0041] Figure 11 This is a schematic diagram of the processing in the prior art.

[0042] Figures 1 to 10The reference numerals in the figures are: 1-supporting substrate, 31-first copper foil layer, 2-adhesive layer, 32-second copper foil layer, 4-solder resist layer, 5-component, 6-first core board, 7-second core board, 8-prepreg, 9-outer copper layer. Detailed Implementation

[0043] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0044] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on the other component or may have an intervening component present. When a component is referred to as "connected to" another component, it can be directly connected to the other component or may have an intervening component present.

[0045] In this invention, unless otherwise stated, directional terms such as "up," "down," "left," and "right" generally refer to... Figure 1 The directions shown are up, down, left, and right. "Inner" and "outer" refer to the inner and outer parts of a specific outline. "Far" and "near" refer to the distance or proximity relative to a particular component.

[0046] Example 1

[0047] like Figures 1-10 As shown in the figure, an embodiment of the present invention provides a method for processing an embedded device PCB, comprising the following steps:

[0048] S1. Create solder pads: (e.g.) Figures 1-2 As shown, a carrier board is provided, and solder mask layers are formed on the front and back sides of the carrier board. Solder mask openings are made on the front and back sides of the carrier board according to the solder pad pattern. The carrier board includes a support substrate, a first copper foil layer located on the front and back sides of the support substrate, an adhesive layer, and a separable second copper foil layer. The second copper foil layer is bonded to the first copper foil layer by the adhesive layer, and the thickness of the second copper foil layer is less than the thickness of the outer copper layer of the embedded device printed circuit board.

[0049] S2, Patch: such as Figure 3 As shown, solder paste is printed on the corresponding pads on the front and back sides of the carrier board. The thickness of the solder paste is 5μm to 25μm, and components are then mounted.

[0050] S3. Provide core boards: Provide a first core board and a second core board. The thickness of the first core board is the component size plus a compensation value A, and the thickness of the second core board is the component size plus a compensation value B. According to the pad positions on the front and back of the carrier board, mill grooves on the first core board and the second core board to process slots for embedding components. When milling the first core board and the second core board, the slot size is the component size plus a compensation value C, where 0.1mm ≦ compensation value A ≦ 0.15mm, 0.1mm ≦ compensation value B ≦ 0.15mm, and 1mm ≦ compensation value C ≦ 5mm.

[0051] S4, Stacked plates: such as Figure 4 As shown, the first core board is placed on the front side of the carrier plate, and the second core board is placed on the back side of the carrier plate, so that the components are placed one-to-one in the slots. Figure 5 As shown, the filler is filled into the slots on the first core board and the second core board. The filler includes thermosetting resin. After filling, it is checked whether the thermosetting resin is fully filled. After the check is completed, it is subjected to pressure thermosetting treatment in a vacuum environment to process the board to be pressed.

[0052] The first core board is set on the front of the support plate by rivets, and the second core board is set on the back of the support plate by rivets. Positioning holes for rivets to pass through are machined on the process edges of the first core board, the second core board and the support plate.

[0053] S5, Pressing: such as Figure 6 As shown, the copper foil and the prepreg are stacked on the plate to be pressed in the order of stacking, and then pressed together. The maximum pressing temperature is less than or equal to 200 degrees Celsius, and the pressure is 25~27 kg / cm2, and the plate to be peeled is pressed out.

[0054] S6, peeling: such as Figure 7 As shown in the figure, the board to be peeled is peeled off between the second copper foil layer and the adhesive layer of the board to be peeled off, thereby peeling off two embedded component substrates.

[0055] S7, Etching, Solder Removal and Tin Removal: such as Figure 8 As shown, acid etching removes the second copper foil layer of the substrate with embedded components, as... Figure 9 As shown, the solder mask layer of the embedded component substrate is removed by immersion in an alkaline solution, and the solder paste and flux residue of the embedded component substrate are removed by desoldering wire treatment.

[0056] S8. Post-processing: such as... Figure 10As shown, the layer stacking is performed in the stacking sequence, so that the upper copper foil, prepreg, embedded component substrate and release film are stacked in sequence, and the prepreg is attached to the surface of the detinning treatment in step S7 and pressed together. The maximum pressing temperature is less than or equal to 200 degrees Celsius and the pressure is 25~27 kg / cm2. After pressing, the circuit is connected to the component pad by laser blind hole connection to make it conductive. The subsequent processing is carried out according to conventional process to obtain two embedded component printed circuit boards.

[0057] In step S5 of this embodiment, the copper foil, the prepreg, and the plate to be pressed are stacked and pressed together. However, those skilled in the art can make several modifications and improvements to this stacking design without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0058] In step S8 of this embodiment, the upper copper foil, prepreg, embedded component substrate and release film are stacked and pressed together. However, those skilled in the art can make several modifications and improvements to this stacking design without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0059] Example 2

[0060] An embodiment of the present invention provides a method for processing an embedded component PCB, comprising the following steps:

[0061] S1. Making pads: Provide a carrier board, make solder mask layers on the front and back of the carrier board, and make solder mask openings on the solder mask layers on the front and back of the carrier board according to the pad pattern. The carrier board includes a support substrate, a first copper foil layer located on the front and back of the support substrate, an adhesive layer, and a separable second copper foil layer. The second copper foil layer is bonded to the first copper foil layer by the adhesive layer.

[0062] S2, Surface Mount: Print solder paste on the corresponding pads on the front and back sides of the carrier board. The thickness of the solder paste is 5μm to 25μm, and then mount the components.

[0063] S3. Provide core board: Provide a first core board and a second core board. According to the position of the pads on the front and back of the carrier board, mill grooves on the first core board and the second core board to process slots for embedding components.

[0064] S4, Stacking: The first core board is set on the front side of the support plate by rivets, and the second core board is set on the back side of the support plate by rivets, so that the components are set in the slots one by one. Positioning holes for rivets to pass through are machined on the process edges of the first core board, the second core board, and the support plate. Thermosetting resin is filled into the slots on the first core board and the second core board. Layering is carried out on the board to be pressed according to the stacking sequence. Positioning holes for rivets to pass through are drilled on the first core board, the second core board, and the support plate. Alignment holes for rivets to pass through are also drilled on the structural layers stacked during the layering process. The board to be pressed is then processed.

[0065] S5. Pressing: Pressing is performed to press out the plate to be peeled off;

[0066] S6. Peeling: Peel the board to be peeled off to remove two embedded component substrates.

[0067] S7. Etching, Solder Mask Removal and Tin Removal: Acid etching removes the second copper foil layer of the embedded component substrate, alkaline solution immersion removes the solder mask layer of the embedded component substrate, and tin stripping line treatment removes solder paste and flux residues from the embedded component substrate.

[0068] S8. Post-processing: Layer stacking is performed according to the stacking sequence, and the prepreg is bonded to the surface after desoldering and then pressed together. After pressing, laser blind vias are used to connect the circuits to the device pads for conductivity. Subsequent processing is carried out according to conventional procedures to obtain two embedded device printed circuit boards.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for fabricating an embedded component PCB, characterized in that: Includes the following steps: S1. Fabricating solder pads: Provide a carrier board, fabricate solder mask layers on the front and back sides of the carrier board, and make solder mask openings on the solder mask layers on the front and back sides of the carrier board according to the solder pad pattern. The carrier board includes a support substrate and a second copper foil layer located on the front and back sides of the support substrate. The carrier board includes a support substrate, a first copper foil layer located on the front and back sides of the support substrate, an adhesive layer, and a separable second copper foil layer. The second copper foil layer is bonded to the first copper foil layer by the adhesive layer. S2, Surface Mount: Print solder paste on the corresponding pads on the front and back sides of the carrier board. The thickness of the solder paste is 5μm to 25μm, and then mount the components. S3. Provide core board: Provide a first core board and a second core board. According to the position of the pads on the front and back of the carrier board, mill grooves on the first core board and the second core board to process slots for embedding components. S4, Stacking: The first core board is placed on the front side of the support plate, and the second core board is placed on the back side of the support plate, so that the components are placed in the slots one by one. The filler is filled into the slots on the first core board and the second core board to process the board to be pressed. S5. Pressing: Add layers to the plates to be pressed according to the stacking sequence, and press them together to produce the plates to be peeled off. S6. Peeling: Peel the board to be peeled off to remove two embedded component substrates. S7. Etching, Solder Mask Removal and Tin Stripping: Removes the second copper foil layer, solder mask layer, solder paste and flux residue from the embedded component substrate; S8. Post-processing: Layer stacking is performed according to the stacking sequence, and the prepreg is bonded to the surface after desoldering and then pressed together. After pressing, it is processed according to conventional procedures. Laser blind vias are used to connect the circuits and the device pads to make them conductive, resulting in two embedded device printed circuit boards.

2. The fabrication method of the embedded device PCB according to claim 1, characterized in that: In step S6, the peeling process of the board to be peeled includes peeling between the second copper foil layer and the adhesive layer of the board to be peeled.

3. The method for processing embedded device PCBs according to claim 1, characterized in that: Step S3 further includes: the thickness of the first core board is based on the component size plus a compensation value A, and the thickness of the second core board is based on the component size plus a compensation value B, where 0.1mm ≤ compensation value A ≤ 0.15mm and 0.1mm ≤ compensation value B ≤ 0.15mm.

4. The method for processing embedded device PCBs according to claim 1, characterized in that: Step S3 also includes: when milling grooves on the first core board and the second core board, the groove size is based on the component size plus a compensation value C, where 1mm ≤ compensation value C ≤ 5mm.

5. The method for fabricating an embedded device PCB according to claim 1, characterized in that: In step S4, the filler includes thermosetting resin, and after filling, it is checked whether the thermosetting resin is fully filled. After the check is completed, a pressure thermosetting treatment is performed in a vacuum environment.

6. The method for processing embedded device PCBs according to claim 1, characterized in that: In step S4, positioning holes for rivets to pass through are machined at the process edges of the first core plate, the second core plate, and the carrier plate. The first core plate is set on the front side of the carrier plate by rivets, and the second core plate is set on the back side of the carrier plate by rivets.

7. The method for fabricating an embedded component PCB according to claim 1, characterized in that: In step S5, the maximum pressing temperature is less than or equal to 200 degrees Celsius, and the pressure is 25~27 kg / cm². 2 .

8. The method for processing embedded device PCBs according to claim 1, characterized in that: In step S8, the maximum pressing temperature is less than or equal to 200 degrees Celsius, and the pressure is 25~27 kg / cm². 2 .

9. The method for processing embedded device PCBs according to claim 1, characterized in that: In step S8, the layering process according to the stacking sequence includes stacking the upper copper foil, prepreg, embedded component substrate, and release film in sequence.

10. The method for processing embedded device PCBs according to claim 1, characterized in that: The process of removing the second copper foil layer, solder mask layer, and residues from the embedded component substrate includes: acid etching to remove the second copper foil layer of the embedded component substrate, alkaline solution immersion to remove the solder mask layer of the embedded component substrate, and desoldering wire treatment to remove solder paste and flux residues from the embedded component substrate.

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