Step bonding pad structure, PCB and manufacturing method

Abstract

The invention relates to the technical field of PCBs, in particular to a step bonding pad structure, a PCB and a manufacturing method. The PCB comprises a first daughter board and a second daughter board, the first daughter board is provided with a first through hole, the second daughter board is provided with a second through hole, the second daughter board and the first daughter board are overlapped through a prepreg, the first through hole and the second through hole are communicated and form a step groove, and the aperture of the first through hole is larger than that of the second through hole. A step surface is formed at the joint of the first through hole and the second daughter board, the hole wall of the first through hole is plated with a first metal layer, the hole wall of the second through hole is plated with a second metal layer, the second through hole is a component plug-in hole, and the first metal layer and the second metal layer respectively extend to the step surface and are isolated by an insulated isolation ring. According to the PCB, the bonding pad can be manufactured in the step groove, specific electrical characteristics or signal isolation in the step groove is achieved, and the applicability of the PCB is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of PCBs, and in particular to a step pad structure, a PCB board and a manufacturing method thereof. Background Art

[0002] In the manufacturing process of PCB (printed circuit board), through-hole is a very important connection method, which allows the pins of electronic components to pass through the PCB board to achieve electrical connection between different layers. The production method of through-hole and the copper plating process have a direct impact on the performance and reliability of PCB. Through-hole is mainly plated with copper by copper plating to achieve electrical connection. The quality of copper plating process directly affects the conductivity and mechanical strength of through-hole.

[0003] At present, copper plating on through-holes is the most basic copper plating method. Copper is evenly plated throughout the depth of the through-hole to ensure that the through-hole has good conductive properties, but the function of the through-hole is relatively single.

[0004] In the production of multi-layer PCB boards, step grooves are used to connect through holes of different layers. However, due to the small diameter of the through holes and the limitations of the copper deposition process, it is currently difficult to make discontinuous copper deposition through holes in the step grooves. Currently, only the following can be achieved: First, uniform copper deposition in the step grooves. Although it can ensure the stable and reliable electrical connection between different layers, specific electrical characteristics or signal isolation cannot be achieved in the step grooves; second, copper deposition in the bottom hole of the step groove. This method is to perform local copper deposition in the bottom hole of the step groove to meet specific design requirements, such as reducing the use of copper or optimizing signal transmission performance, but specific electrical characteristics or signal isolation cannot be achieved in the step groove. Third: Since this type of product is an uneven surface, it is necessary to prevent the tin from not being etched on the copper surface and the part that is not etched is in the concave ring. Therefore, the existing dry film pasting technology cannot meet the processing quality of the pads in the metallized cavity. Summary of the invention

[0005] One of the purposes of the present invention is to avoid the deficiencies in the prior art and provide a step pad structure, which can manufacture pads in a step groove of a PCB board, achieve specific electrical characteristics or signal isolation in the step groove, and improve the applicability of the PCB board.

[0006] A second object of the present invention is to provide a method for manufacturing a step pad structure.

[0007] To achieve one of the above purposes, the present invention provides the following technical solutions: A step pad structure is provided, comprising: a first sub-board, wherein the first sub-board is provided with a first through hole, a second sub-board, wherein the second sub-board is provided with a second through hole, the second sub-board is overlapped with the first sub-board through a prepreg, the first through hole is connected with the second through hole and forms a step groove, the aperture of the first through hole is larger than the aperture of the second through hole, and a step surface is formed at the connection between the first through hole and the second sub-board, The hole wall of the first through hole is plated with a first metal layer, the hole wall of the second through hole is plated with a second metal layer, the second through hole is a component insertion hole, the first metal layer and the second metal layer respectively extend to the step surface and are isolated by an insulating isolation ring, and a pad connected to the second metal layer is formed on the step surface.

[0008] Beneficial effects of a step pad structure of the present invention: A step pad structure of the present invention has a first metal layer on the hole wall of a first through hole in a step groove, and a second metal layer on the hole wall of a second through hole in the step groove, wherein an isolation ring is provided on the step surface at the connection between the first through hole and the second through hole, so that a pad connected to the second metal layer is formed on the step surface, so that two different components can be independently connected in the step groove, and specific electrical characteristics or signal isolation can be achieved, that is, the flat installation of special-shaped components can be met, and different levels can be interconnected and conductive through metallized steps, thereby overcoming the problem of single function of traditional PCB boards due to the small through hole diameter.

[0009] In order to achieve the second purpose above, a PCB board with a step pad structure is provided, and the step pad structure is the step pad structure mentioned above.

[0010] To achieve the third objective above, the present invention provides the following technical solutions: A method for manufacturing the PCB board having the above-mentioned step pad structure is provided, comprising the following steps: Step 1: manufacturing a first sub-board and a second sub-board pressed together, opening a first through hole on the first sub-board and a second through hole on the second sub-board, so that the first through hole and the second through hole are connected to form the step groove; Step 2: performing copper electroplating on the inner wall of the step groove to form a first metal layer in the first through hole, a first metal layer in the second through hole, and the first metal layer and the second metal layer extend to the step surface; Step 3: printing a character frame on the step surface along the distribution position of the preset isolation ring; Step 4: sequentially perform outer layer pattern production, pattern electro-tinning treatment and character frame removal, followed by alkaline etching treatment to remove the metal layer corresponding to the character frame position, so that the step surface forms an isolation ring and a solder pad is obtained on the step surface.

[0011] In some embodiments, the width of the character frame is ≥50 μm.

[0012] In some embodiments, in step 1, before the first sub-board and the second sub-board are pressed together, the first sub-board has the first through hole, and the second sub-board has the second through hole.

[0013] In some embodiments, in step 2, when printing the character frame, a text printer is selected to print back and forth on the step surface at least three times.

[0014] In some embodiments, the first sub-plate and the second sub-plate are pressed together by PP glue. After pressing together, a first laser carbonization is used to remove the PP residual glue overflowing from the inner wall of the step groove.

[0015] In some embodiments, the manufacturing method of the first sub-board includes: selecting a plurality of first board layers, performing baking treatment, inner layer circuit manufacturing, and acid etching on each first board layer in turn, and then laminating the processed first board layers to obtain a first sub-board, and milling a first through hole on the first sub-board.

[0016] In some embodiments, the manufacturing method of the second sub-board includes: selecting a plurality of second board layers, baking the second board layers, manufacturing inner layer circuits, and acid etching the second board layers in sequence, and then laminating the processed second board layers to obtain a second sub-board, and drilling a second through hole on the second sub-board.

[0017] In some embodiments, a second laser is used to remove the character box.

[0018] In some embodiments, the second laser is a microsecond laser with the following parameters: frequency of 5600 Hz to 100 Hz and energy of 3 mJ to 6 mJ.

[0019] Beneficial effects of the manufacturing method of the step pad structure of the present invention: The present invention provides a method for manufacturing a step pad structure, which first deposits copper in a step groove to produce a continuous metal layer for a first through hole and a second through hole, then prints a character frame at the position of an isolation ring, and then performs electrotinning after printing the character frame. The tin layer cannot cover the character frame but covers the metal layer outside the character frame, thereby protecting the metal layer outside the isolation ring. Subsequently, the character frame is removed and alkaline etching is performed to remove the metal on the character frame to obtain an isolation ring, so that a pad is formed on the step surface. The pad is connected to the second metal layer, so that two independent component connection positions can be obtained in the narrow step groove.

[0020] Before electrotinning, characters or solder resist are printed to block the part of the edge of the pad in the metallized cavity that needs to be etched away, ensuring that the electrotinning process can effectively block the copper part that needs to be etched away. After electrotinning, laser is used to carbonize and remove the characters, ensuring that the pad in the metallized cavity can be effectively produced during alkaline etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a step pad structure according to a specific embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of making a character frame on a stepped surface according to a specific embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram of removing the character frame according to a specific implementation manner of the present invention.

[0024] Figure 4 It is a flow chart of a method for manufacturing a step pad structure according to a specific embodiment of the present invention.

[0025] Figure 5 It is a product diagram of a PCB board with a stepped pad structure according to a specific implementation mode of the present invention.

[0026] Figure 6 It is a product diagram of a step pad structure according to a specific embodiment of the present invention.

[0027] Reference numerals: 1. First sub-board; 2. Second sub-board; 3. First through hole; 4. Second through hole; 5. Solder pad; 6. First metal layer; 7. Second metal layer; 8. Step surface; 9. PP glue; 10. Isolation ring; 11. Tin layer; 12. Character frame; 13. Metal layer. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0029] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms of "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0030] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0031] Example

[0032] The PCB board with the pad 5 disposed in the metallized step groove disclosed in the embodiment, such as Figure 1~Figure 3 As shown, including: A first sub-board 1 is provided with a first through hole 3. Specifically, the first sub-board 1 is a core board with a first through hole 3 formed therein, and the first through hole 3 is formed on the first sub-board 1 .

[0033] The second sub-board 2 is provided with a second through hole 4. The second sub-board 2 is overlapped with the first sub-board 1 through a prepreg. The first through hole 3 is connected with the second through hole and forms a step groove. The aperture of the first through hole 3 is larger than the aperture of the second through hole 4. A step surface 8 is formed at the connection between the first through hole 3 and the second sub-board 2. Specifically, the second sub-board 2 is a core board with a second through hole 4, and the second through hole 4 is opened on the second sub-board 2, and then the first sub-board 1 and the second sub-board 2 are pressed and connected together through a semi-cured sheet, wherein the first through hole 3 is located above the second through hole 4, and the aperture of the first through hole 3 is larger than the aperture of the second through hole 4, so that a step groove is formed and a step surface 8 is formed at the connection between the first through hole 3 and the second sub-board 2, and the step groove facilitates the subsequent formation of a special through hole structure.

[0034] The hole wall of the first through hole 3 is plated with a second metal layer 6, and the hole wall of the second through hole 4 is plated with a second metal layer 7. The second through hole 4 is a component insertion hole. The second metal layer 6 and the second metal layer 7 extend to the step surface 8 respectively and are isolated by an insulating isolation ring 10. A solder pad 5 connected to the second metal layer 7 is formed on the step surface 8.

[0035] Specifically, a second metal layer 6 is arranged in the hole wall of the first through hole 3, and a second metal layer 7 is arranged in the hole wall of the second through hole 4, and the second metal layer 6 and the second metal layer 7 are separated by an isolation ring 10, so that a pad 5 is formed on the step surface 8, and the pad 5 is connected to the second metal layer 7. Therefore, two different components can be independently connected in the step groove, and specific electrical characteristics or signal isolation can be achieved, which can not only meet the flat installation of special-shaped components, but also realize mutual conduction of different levels through metallized steps, thereby overcoming the problem of single function of traditional PCB boards due to the small through-hole aperture.

[0036] The manufacturing method of the PCB board with the pad 5 arranged in the metallized step groove is as follows: Figure 4 As shown, the following steps are included: Step 1: manufacturing a first sub-plate 1 and a second sub-plate 2 pressed together, opening a first through hole 3 on the first sub-plate 1, and opening a second through hole 4 on the second sub-plate 2, so that the first through hole 3 and the second through hole 4 are connected to form the step groove; Specifically, the first sub-board 1 with the first through hole 3 and the second sub-board 2 with the second through hole 4 are first pressed together, and the first sub-board 1 and the second sub-board 2 are pressed together by the semi-cured sheet PP glue 9. Before pressing, the outer end of the semi-cured sheet located on the first through hole 3 needs to be partially hollowed out, and the depth of the hollowing is 0.2 mm to prevent the semi-cured sheet from overflowing excessively into the step groove after melting, thereby affecting the overall flatness of the step groove.

[0037] Step 2: copper electroplating is performed on the inner wall of the step groove to form a second metal layer 6 in the first through hole 3, a second metal layer 6 in the second through hole 4, and the second metal layer 6 and the second metal layer 7 extend to the step surface 8; Specifically, when copper electroplating is performed on the step groove, the inner wall of the entire step groove is electroplated.

[0038] Step 3, printing a character frame 12 on the step surface 8 along the distribution position of the preset isolation ring 10; Specifically, after copper electroplating, a printed character frame 12 is made on the step surface 8 , and the character frame 12 is used to cover the position where the isolation ring 10 is formed. The character frame 12 is made according to the final preset shape of the pad 5 .

[0039] In this embodiment, in the step 2, when printing the character frame 12, a text printer is selected to print back and forth on the step surface 8 at least three times, preferably three times.

[0040] Since the copper at the bottom of the character lines needs to be completely etched clean, the etched copper needs to be completely covered when the character lines are printed, and the number of character printings must be accurately controlled. When printing characters, the high-definition mode is used to print back and forth 3 times. It should be noted that the high-definition mode is relative to the normal mode. Due to the different equipment and models of different text printers, the resolution will vary, and the resolution is not limited here.

[0041] Specifically, the parameters of the printing character frame 12 are shown in Table 1: ; Step 4: The product after the characters is subjected to outer layer graphic production, electro-tinning treatment and removal of the character frame 12 in sequence, followed by alkaline etching treatment to remove the metal layer 13 surface corresponding to the position of the character frame 12, so that the step surface 8 forms an isolation ring 10, and a pad 5 is obtained on the step surface 8.

[0042] See specifically Figure 2~Figure 3 First, prepare the outer layer graphic circuit, then perform electro-tinning treatment so that the tin layer 11 is deposited on the metal layer 13, wherein the tin layer 11 cannot be deposited at the position of the character frame 12, so the character frame 12 is exposed, and then only the character frame 12 is processed to expose the metal layer 13 (copper layer) corresponding to the position of the character frame 12, and the exposed metal layer 13 can be effectively removed by alkaline etching to form an isolation ring 10, and then a pad 5 is prepared on the step surface 8.

[0043] The ring width of the character frame 12 is ≥50 μm, preferably 50-80 μm.

[0044] If the width of the character frame 12 is too small, the etching liquid cannot flow to the bottom of the character frame 12 for alkaline etching due to the narrow width of the character frame 12 , and the isolation ring 10 cannot be obtained.

[0045] In this embodiment, in the step 1, before the first sub-board 1 and the second sub-board 2 are pressed together, the first sub-board 1 is provided with the first through hole 3 , and the second sub-board 2 is provided with the second through hole 4 .

[0046] Specifically, before the first sub-board 1 and the second sub-board 2 are pressed together, the first through hole 3 and the second through hole 4 are respectively opened in the first sub-board 1 and the second sub-board 2 to avoid the problem that the lower through hole cannot be drilled due to the upper through hole being too small after pressing together, or the upper through hole is damaged when the drill needle is inserted from the upper through hole.

[0047] Specifically, in this embodiment, the first sub-plate 1 and the second sub-plate 2 are pressed together by the PP glue 9. After pressing together, the first laser carbonization is used to remove the PP residual glue overflowing from the inner wall of the step groove.

[0048] Specifically, since the PP glue 9 has fluidity, after the first sub-plate 1 and the second sub-plate 2 are pressed together, the overflowed PP residual glue is removed by laser carbonization to maintain the flatness of the inner wall of the step groove.

[0049] Furthermore, the laser parameters for processing PP residual adhesive are shown in Table 2: ; In this embodiment, the manufacturing method of the first sub-board 1 includes: selecting a plurality of first board layers, performing baking treatment, inner layer circuit manufacturing, and acid etching on each first board layer in turn, and then laminating the processed first board layers to obtain the first sub-board 1, and milling a first through hole 3 on the first sub-board 1.

[0050] In this embodiment, the manufacturing method of the second sub-board 2 includes: selecting a plurality of second board layers, baking each second board layer, making inner layer circuits, and acid etching in turn, and then laminating the processed second board layers to obtain the second sub-board 2, and drilling a second through hole 4 on the second sub-board 2.

[0051] The specific conditions for the baking plate are: baking at 150°C for 2 to 4 hours.

[0052] The inner layer circuit production is specifically as follows: the inner layer roughening method is used to roughen and clean the copper surface, double-sided dry film is applied, and the pattern is transferred by LDI laser imaging according to the MI inner layer circuit file, and the inner layer circuit pattern is obtained after development.

[0053] The specific operations of acid etching and other operations are as follows: According to the thickness of the inner copper layer of MI, matching parameters are selected for etching to corrode the copper surface without dry film protection; After the inner layer is etched, the surface dry film is removed by a horizontal film stripping machine. The inner line circuit after etching and film stripping is inspected by an AOI machine. The copper surface is roughened and cleaned by the inner layer browning line to improve the bonding strength of the lamination. Pre-stack according to the MI stacking structure, and then riveted. When riveting, all the encrypted tool holes on the edge of the board are riveted.

[0054] The pressing process is specifically as follows: according to the PP characteristics, a matching pressing program is selected to perform vacuum pressing; In this embodiment, the character frame 12 is removed using a second laser.

[0055] In this embodiment, the second laser is a microsecond laser, and its parameters are: frequency of 5600 Hz to 100 Hz, energy of 3 mJ to 6 mJ, and the laser parameters for removing the character frame 12 are shown in Table 3: ; pass Figure 5 , Figure 6It can be seen that a product image of a PCB board with a step pad structure is obtained, and the step welding structure is successfully manufactured on the PCB board.

[0056] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the application. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0057] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0058] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0059] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A step pad structure, characterized in that: include a first sub-board, wherein the first sub-board is provided with a first through hole, a second sub-board, wherein the second sub-board is provided with a second through hole, the second sub-board is overlapped with the first sub-board through a prepreg, the first through hole is connected with the second through hole and forms a step groove, the aperture of the first through hole is larger than the aperture of the second through hole, and a step surface is formed at the connection between the first through hole and the second sub-board, The hole wall of the first through hole is plated with a first metal layer, the hole wall of the second through hole is plated with a second metal layer, the second through hole is a component insertion hole, the first metal layer and the second metal layer respectively extend to the step surface and are isolated by an insulating isolation ring, and a pad connected to the second metal layer is formed on the step surface.

2. A PCB board with a step pad structure, characterized in that: The step pad structure is the step pad structure according to claim 1.

3. A method for manufacturing a PCB board with a step pad structure according to claim 2, characterized in that: The following steps are involved: Manufacturing a first sub-plate and a second sub-plate pressed together, opening a first through hole in the first sub-plate, and opening a second through hole in the second sub-plate, so that the first through hole and the second through hole are connected to form the step groove; Performing copper electroplating on the inner wall of the step groove to form a first metal layer in the first through hole, a first metal layer in the second through hole, and extending the first metal layer and the second metal layer to the step surface; Printing character frames on the step surface along the distribution positions of the preset isolation rings; The outer layer pattern production, pattern electrotin treatment and character frame removal treatment are carried out in sequence, followed by alkaline etching treatment to remove the metal layer corresponding to the character frame position, so that the step surface forms an isolation ring and a solder pad is obtained on the step surface.

4. The method for manufacturing a PCB board with a stepped pad structure according to claim 3, characterized in that: The width of the character frame is ≥50 μm.

5. The method for manufacturing a PCB board with a stepped pad structure according to claim 3, characterized in that: Before the first sub-board and the second sub-board are pressed together, the first sub-board is provided with the first through hole, and the second sub-board is provided with the second through hole.

6. The method for manufacturing a PCB board with a step pad structure according to claim 3, characterized in that: When printing the character frame, a text printer is selected to print back and forth on the step surface at least three times.

7. The method for manufacturing a PCB board with a step pad structure according to claim 3, characterized in that: The first sub-plate and the second sub-plate are pressed together by PP glue. After pressing together, the PP residual glue overflowing from the inner wall of the step groove is removed by first laser carbonization.

8. The method for manufacturing a PCB board with a stepped pad structure according to claim 7, characterized in that: The manufacturing method of the first sub-board includes: selecting a plurality of first board layers, performing baking treatment, inner layer circuit manufacturing, and acid etching on each first board layer in turn, and then laminating the processed first board layers to obtain a first sub-board, and milling a first through hole on the first sub-board.

9. The method for manufacturing a PCB board with a step pad structure according to claim 7, characterized in that: The manufacturing method of the second sub-board includes: selecting a plurality of second board layers, baking the second board layers, manufacturing inner layer circuits, and acid etching in sequence, and then laminating the processed second board layers to obtain the second sub-board, and drilling a second through hole on the second sub-board.

10. The method for manufacturing a PCB board with a step pad structure according to claim 3, characterized in that: The character frame is removed by using a second laser, wherein the second laser is a microsecond laser with the following parameters: a frequency of 5600 Hz to 100 Hz and an energy of 3 mJ to 6 mJ.

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