Stepped printed circuit board preparation method and printed circuit board

Abstract

The invention relates to a stepped printed circuit board preparation method and a printed circuit board, and belongs to the technical field of printed circuit boards. The method comprises the following steps of: plugging through holes in a first sub-board and a second sub-board with resin and electroplating caps; performing pattern etching on the step region of the second sub-board; after the step area of the second daughter board is coated with solder resist ink and a glue-resistant protective material is placed, the first daughter board and the second daughter board are laminated to form a mother board; covering a dry film on the through hole which is plugged by resin in the step area, and performing thinning and copper reduction on the corresponding step area on the surface of the mother board; secondary drilling is carried out on the corresponding step area of the mother board, and resin in secondary drilling holes is removed; and drilling a step area on the first daughter board in a blind fishing mode to expose the pattern etched on the second daughter board. According to the method provided by the invention, solder leakage and impurities can be prevented from entering the through hole in the operation process, the through hole is effectively protected, and meanwhile, the etching precision of the golden finger pattern in the step region is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of printed circuit boards, and relates to a method for preparing a stepped printed circuit board and a printed circuit board. Background Art

[0002] In order to meet the requirements of modern devices for high-density and high-reliability connections, higher requirements are put forward for the design of printed circuit boards. It is necessary to design graphics and vias on different planes for soldering and plug-in components to meet the sufficient assembly area within a limited chassis space. Due to the fixed slot size limit of the high-speed serial computer expansion bus standard, it is necessary to design a stepped gold finger pattern to meet the assembly requirements of signal input and output.

[0003] Currently, for printed circuit boards with stepped patterns and vias, the industry usually forms the stepped surface by the method of blind drilling after lamination, and then realizes it by electroplating copper and tin, and then etching after tin removal. This method is affected by the diameter of the drilling needle, so it cannot meet the high-precision requirements of the stepped gold finger pattern. For the stepped gold finger pattern, the current implementation method is to make the gold finger pattern by image transfer on the inner layer, and use a resist material for protection. After lamination, the outer layer process is carried out, and finally the stepped fingers are formed by blind drilling. However, this method cannot completely protect the plug-in holes in the stepped surface during the operation process. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a method for preparing a stepped printed circuit board and a printed circuit board, which can improve the preparation effect of the plug-in holes and the gold finger pattern in the stepped area of the printed circuit board.

[0005] To achieve the above purpose, the present invention is implemented by the following technical solutions:

[0006] On the one hand, the present invention provides a method for preparing a stepped printed circuit board, the method comprising:

[0007] Resin plugging holes and electroplating caps on the vias of the first sub-board and the second sub-board;

[0008] Planning the shape and position of the stepped area on the surfaces of the first sub-board and the second sub-board;

[0009] Performing graphic etching on the stepped area of the second sub-board;

[0010] After applying solder resist ink and placing resist protection material on the stepped area of the second sub-board, laminating the first sub-board and the second sub-board to form a mother board;

[0011] After covering the dry film on the vias plugged with resin in the corresponding stepped area on the surface of the mother board, thinning and copper reduction are performed on the corresponding stepped area on the surface of the mother board;

[0012] Perform second drilling on the corresponding stepped area of the motherboard to remove the resin in the second drilled holes, and the positions of the second drilling correspond to the positions of some through holes on the second daughter board;

[0013] Drill a stepped area on the first daughter board by blind fishing according to the planned shape and position to expose the pattern etched on the second daughter board.

[0014] Furthermore, the first daughter board and the second daughter board are pre-pressed, drilled, and electroplated with holes according to the stacking method design of the printed circuit board.

[0015] Furthermore, resin plugging and electroplating capping are performed on the through holes on the first daughter board and the second daughter board, including:

[0016] Perform resin plugging on the through holes on the first daughter board and the second daughter board, and after baking the board to cure the resin, grind and remove the residual resin on the surface of the daughter board;

[0017] Clean, electroless copper plate, and electroplate the first daughter board and the second daughter board that have completed resin plugging to form an electroplated cap at the through holes of the daughter board.

[0018] Furthermore, the resin plugging is vacuum resin plugging.

[0019] Furthermore, the patterns etched at the stepped groove positions on the surface of the second daughter board include gold finger patterns and / or circuit patterns.

[0020] Furthermore, the resist protection material is a high-temperature resistant tape or a high-temperature resistant ink.

[0021] Furthermore, it also includes: after completing pattern etching in the stepped area of the second daughter board, perform electroplated hard gold treatment on the pattern surface.

[0022] Furthermore, performing second drilling on the corresponding stepped area of the motherboard includes: setting a plurality of calibration holes around the board edge of the corresponding stepped area of the motherboard, and using a CCD camera to capture the calibration holes to control the alignment accuracy of the drill bit.

[0023] Furthermore, drilling a stepped area on the first daughter board by blind fishing includes: setting the lower fishing depth according to the thickness of the first daughter board, and fishing to the position of the resist protection material between the first daughter board and the second daughter board.

[0024] On the other hand, the present invention also provides a printed circuit board prepared by the above stepped printed circuit board preparation method.

[0025] Compared with the prior art, the beneficial effects achieved by the present invention:

[0026] The present invention provides a method for manufacturing a stepped printed circuit board. Before operating on the daughter board, resin is used to fill the vias to prevent solder leakage and impurities from entering the vias, effectively protecting the vias. After the operation on the mother board is completed, a second drilling is carried out to remove part of the resin in the vias and form insertion holes in the stepped area; in the present invention, graphic etching is carried out in the pre-planned stepped area of the daughter board, and solder mask ink is coated after the graphic etching is completed. Finally, the graphics are exposed by the blind fishing method to achieve high-precision manufacturing of graphics such as gold fingers in the stepped area; when carrying out the second drilling in the present invention, by setting a plurality of calibration holes around the stepped area and using a CCD camera to capture the calibration holes to control the alignment accuracy of the drill bit, it can ensure that the copper thickness of the remaining hole walls on both sides of the insertion holes in the stepped area can meet the specification requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic flow chart of a method for manufacturing a stepped printed circuit board provided by an embodiment of the present invention;

[0028] Figure 2 is a schematic cross-sectional structure diagram of the first daughter board and the second daughter board in an embodiment of the present invention;

[0029] Figure 3 is a schematic cross-sectional structure diagram of the first daughter board and the second daughter board after resin plugging of the vias in an embodiment of the present invention;

[0030] Figure 4 is a schematic cross-sectional structure diagram of the second daughter board after electroplating caps at the vias in an embodiment of the present invention;

[0031] Figure 5 is a schematic cross-sectional structure diagram of the second daughter board after electroplating hard gold on the graphic surface and coating solder mask ink in the stepped area in an embodiment of the present invention;

[0032] Figure 6 is a schematic diagram of the corner mark position of the L20 surface of the first daughter board in an embodiment of the present invention;

[0033] Figure 7 is a schematic cross-sectional structure diagram of the mother board formed by laminating the first daughter board and the second daughter board in an embodiment of the present invention;

[0034] Figure 8 is a schematic cross-sectional structure diagram of the mother board after thinning and copper reduction in the stepped area in an embodiment of the present invention;

[0035] Figure 9 is a schematic diagram of the position of the calibration holes in an embodiment of the present invention;

[0036] Figure 10 is a schematic cross-sectional structure diagram of the mother board after the second drilling in the stepped area in an embodiment of the present invention;

[0037] Figure 11 Cross-sectional structure schematic diagram of the motherboard after drilling a stepped groove on the first daughter board in the embodiment of the present invention;

[0038] Figure 12 Schematic diagram of the structure of a printed circuit board provided by an embodiment of the present invention. Detailed implementation manners

[0039] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. The embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0040] The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after. The terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only used to explain the relative position relationship and movement conditions between components in a specific posture. If this specific posture changes, the directional indication will also change accordingly. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present disclosure / the present application.

[0041] In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0042] In the description of the present application, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0043] Embodiment 1:

[0044] As Figures 1 to 10 shown, the embodiment of the present invention provides a method for preparing a stepped printed circuit board. Figure 1 is a schematic flowchart of the method for preparing the stepped printed circuit board. This flowchart only shows the logical order of the method described in this embodiment. On the premise of not conflicting with each other, in other possible embodiments of the present invention, the steps shown or described can be completed in a different order from Figure 1 that shown.

[0045] Refer to Figure 1 , the method of the embodiment of the present invention specifically includes the following steps:

[0046] Step 1: Resin plug the vias on the first sub-board and the second sub-board and electroplate the caps.

[0047] Among them, the first sub-board and the second sub-board have been pre-operated such as substrate lamination, drilling, and electroplating the plated holes according to the stack design of the printed circuit board in this embodiment. As Figure 2 shown, in the embodiment of the present invention, the first sub-board is 20 layers (L1-L20), and the second sub-board is 16 layers (L21-L36). The thickness of the second sub-board is the thickness of a standard PCIe interface card slot. The L21 surface is designed with a gold finger pattern as the graphic layer of the stepped slot, and the gold finger pattern on the other side is designed on the L36 layer. The second sub-board is designed with ordinary vias and plug holes. The vias are in accordance with the hole copper specification of 1.0 mil Min, and the plug holes are in accordance with the hole copper specification of 2.5 mil Min. Therefore, in addition to the normal electroplating condition of 8 ASF * 110 MIN for electroplating all holes, a selective electroplating hole process is specially designed to electroplate the plug hole positions separately, and the electroplating condition is 9 ASF * 120 MIN * 2.

[0048] Resin plug all the vias on the first sub-board and the second sub-board, including ordinary vias and plug holes, and then bake the board to cure the resin and grind to remove the residual resin on the surface of the sub-board. In order to ensure the plug hole quality and prevent the occurrence of hole mouth depression and bubbles, the vacuum resin plug hole method is adopted.

[0049] Figure 3A cross-sectional schematic diagram of the first and second daughter boards with resin-filled vias is shown.

[0050] The first and second daughter boards with resin-filled vias are cleaned, electroless copper plated, and electroplated to form electroplated caps at the through-holes of the daughter boards. Among them, for the second daughter board, the cap electroplating process is designed, and the electroplating conditions are 14 ASF * 56.6 MIN, and the surface copper on the resin needs to meet 0.6 mil Min.

[0051] Figure 4 A cross-sectional schematic diagram of the second daughter board with the electroplated cap completed at the through-hole is shown.

[0052] Step 2: Plan the shape and position of the stepped area on the surfaces of the first and second daughter boards.

[0053] The first and second daughter boards will be laminated to form a mother board later, and then the stepped grooves will be blindly fished out according to the shape and position of the planned stepped area. Therefore, each of the first daughter board, the second daughter board, and the mother board corresponds to a stepped area.

[0054] Step 3: Perform pattern etching on the stepped area of the second daughter board.

[0055] In the embodiment of the present invention, a part of the L21 surface of the second daughter board is the stepped area, which is also the bottom of the stepped groove. Therefore, pattern etching is performed on the stepped area of the L21 surface of the second daughter board according to the design requirements. The pattern can include gold finger patterns, circuit patterns, and so on.

[0056] Step 4: After applying solder mask ink and placing a resist protection material in the stepped area of the second daughter board, laminate the first and second daughter boards to form a mother board.

[0057] After the pattern etching of the stepped area of the second daughter board is completed, the pattern needs to be surface-treated, generally electroplated with hard gold. In addition, the stepped area of the second daughter board needs to be coated with solder mask ink.

[0058] Figure 5 A cross-sectional schematic diagram of the second daughter board with the pattern surface electroplated with hard gold and the stepped area coated with solder mask ink on the L21 surface is shown.

[0059] After that, a resist protection material is placed in the stepped area of the second daughter board, and the L20 surface of the first daughter board is opposed to the L21 surface of the second daughter board, and they are laminated to form a mother board. The resist protection material can use high-temperature resistant tape or high-temperature resistant ink.

[0060] In the embodiment of the present invention, the resist protection material uses high-temperature resistant tape. The shape of the stepped area in this embodiment is concave. In order to improve the position accuracy of the high-temperature resistant tape, corner marks are set at the corresponding positions on the L20 surface of the first daughter board. The positions of the corner marks are as Figure 6As shown, the accuracy of the tape sticking position is determined by checking the alignment between the tape edge and the corner mark. After the tape is stuck, the browning and pressing processes are carried out, with the L20 surface of the first sub-board facing the L21 surface of the second sub-board, and the mother board is formed by pressing.

[0061] Figure 7 The cross-sectional schematic diagram of the mother board formed after the first sub-board and the second sub-board are pressed is shown.

[0062] Step 5: After covering the dry film on the through holes filled with resin in the corresponding stepped area on the surface of the mother board, the surface of the mother board in the corresponding stepped area is thinned and copper is reduced.

[0063] Since the outer fine circuit requires that the copper on the circuit board surface cannot be too thick, it is necessary to thin and reduce copper on the L1 and L36 surfaces after pressing into the mother board. The through holes filled with resin in the stepped area do not participate in this copper thinning and reduction, so the dry film is covered on these through holes for protection. Specifically, corresponding alignment holes need to be drilled on the board edge, and the alignment holes are grabbed for image transfer, so that the holes of the resin plugs at the stepped positions on the L36 surface are covered with dry film for protection when on the B board.

[0064] Figure 8 The cross-sectional schematic diagram of the mother board after the stepped area is thinned and copper is reduced is shown.

[0065] After thinning, the surface of the mother board needs to be optically inspected to check whether the hole pads are damaged to prevent the chemical solution from seeping into the through holes.

[0066] After that, processes such as drilling, electroplating, resin hole filling, pattern etching, solder resist ink printing, and surface treatment of the mother board can be completed according to the actual design requirements.

[0067] Step 6: Second drilling is carried out in the corresponding stepped area of the mother board to remove the resin in the second drilled holes, and the positions of the second drilling correspond to the positions of some through holes on the second sub-board.

[0068] Some of the through holes on the second sub-board are designed to be plug holes. Second drilling is carried out at the positions corresponding to these through holes to remove the resin filled in the second drilled holes. After the stepped grooves are drilled on the first sub-board, these second drilled holes become the plug holes in the stepped area.

[0069] Specifically, as Figure 9 shown, 4 calibration holes are set around the board edge in the corresponding stepped area of the mother board, and the CCD camera is used to grab the calibration holes to control the alignment accuracy of the drill bit, ensuring that the copper thickness of the remaining hole walls on both sides of the plug holes in the stepped area can meet the specification requirement of 1.0mil Min.

[0070] In addition, drilling will also be carried out at this time in the areas of the mother board other than the stepped area.

[0071] Figure 10Shows a cross-sectional schematic diagram of the mother board after the second drilling is completed in the stepped area.

[0072] Step 7: Drill a stepped groove on the first sub-board in a blind fishing manner according to the planned shape and position to expose the pattern etched on the second sub-board.

[0073] Set the fishing depth according to the remaining board thickness of 63 mil, fish to the position of the resist protection material between the first sub-board and the second sub-board, and no debris fishing treatment is required. Use a tool to pry up part A of the sub-board and remove it together with the high-temperature resistant tape to expose the pattern on the stepped surface.

[0074] Figure 11 Shows a cross-sectional schematic diagram of the mother board after the stepped groove is drilled on the first sub-board.

[0075] Embodiment 2:

[0076] As Figure 12 shown, the embodiment of the present invention provides a printed circuit board. The printed circuit board of the embodiment of the present invention is prepared by the stepped printed circuit board preparation method in the above embodiment, which will not be elaborated here. The printed circuit board includes a first sub-board and a second sub-board that are laminated. A stepped area is provided on the first sub-board to expose the gold finger pattern and / or circuit pattern etched on the surface of the second sub-board; a plug hole is provided in the stepped area.

[0077] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present disclosure / this application.

Claims

1. A method for preparing a stepped printed circuit board, characterized in that: include: Performing resin plugging and electroplating capping on the through holes on the first sub-board and the second sub-board; Planning the shape and position of the step area on the surfaces of the first sub-board and the second sub-board; Performing pattern etching in the step region of the second sub-plate; After applying solder resist ink and placing adhesive resist protective material on the step area of ​​the second sub-board, pressing the first sub-board and the second sub-board together to form a motherboard; After covering the through holes in the step area corresponding to the motherboard surface with resin plugging with dry film, the step area corresponding to the motherboard surface is thinned and copper is reduced; Perform secondary drilling on the corresponding step area of ​​the motherboard to remove the resin in the secondary drill hole, wherein the position of the secondary drill hole corresponds to the position of a part of the through hole on the second daughterboard; According to the planned shape and position, a step area is drilled on the first sub-board by blind drilling to expose the pattern etched on the second sub-board.

2. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: The first sub-board and the second sub-board are preliminarily subjected to substrate lamination, drilling and hole electroplating operations according to the stacking design of the printed circuit board.

3. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: The through holes on the first daughter board and the second daughter board are plugged with resin and capped with electroplating, including: The through holes on the first sub-board and the second sub-board are plugged with resin, and the resin remaining on the surface of the sub-boards is removed by grinding after the boards are baked to cure the resin; The first daughter board and the second daughter board with completed resin plugging holes are cleaned, copper deposited and electroplated to form electroplating caps at the through holes of the daughter boards.

4. The method for preparing a stepped printed circuit board according to claim 3, characterized in that: The resin plugging hole is a vacuum resin plugging hole.

5. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: The pattern etched at the step groove position on the surface of the second sub-board includes a gold finger pattern and / or a circuit pattern.

6. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: The adhesive resistance protection material is a high temperature resistant adhesive tape or a high temperature resistant ink.

7. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: Also includes: After the pattern etching is completed in the step region of the second sub-plate, the pattern surface is electroplated with hard gold.

8. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: Performing secondary drilling in the step area corresponding to the motherboard includes: setting a plurality of correction holes around the edge of the motherboard corresponding to the step area, and using a CCD camera to capture the correction holes to control the alignment accuracy of the drill bit.

9. The method for preparing a stepped printed circuit board according to claim 1, characterized in that: Drilling a stepped area on the first sub-board by blind scooping includes: setting a scooping depth according to a thickness of the first sub-board, and scooping to a position of the glue blocking protective material between the first sub-board and the second sub-board.

10. A printed circuit board, characterized in that: The printed circuit board is prepared by the method according to any one of claims 1 to 9.

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