A kind of blind channel circuit board tin spraying surface treatment processing method

Abstract

The application relates to a kind of processing methods of tin spraying surface treatment of blind slot circuit board, the original blind slot method is processed using twice milling blind slot processing, first milling blind slot is milled a small blind slot, to expose the figure area of the original blind slot bottom surface area, then tin spraying surface treatment is carried out, at this time the figure area will be covered with tin protection layer, at the same time, tin beads will be hidden in the gap position of the side wall and the bottom edge of the small blind slot milled in the first time, then second milling blind slot is carried out, the second milling blind slot is to mill the side wall and the bottom edge position of the small blind slot milled in the first time to expose the base material area of the original blind slot, to realize the production of the original blind slot, since the second milling blind slot is to mill all the parts that may hide tin beads from the mechanical point of view, so the side wall and the bottom edge position of the blind slot after tin spraying produced by the method cannot have tin beads hidden, and the problem of short circuit caused by tin beads hidden after tin spraying surface treatment of blind slot is completely solved from the process level.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing, and in particular to a method for tin-plating surface treatment of blind slot circuit boards. Background Technology

[0002] With the development of electronic circuits and the demands of end-application scenarios, printed circuit boards (PCBs) are no longer simply flat surfaces. PCBs have evolved into diverse and multi-dimensional products. One type of product features a recessed design with traces and holes at the bottom, commonly known in the PCB industry as a blind slot. The bottom pattern of this type of blind slot can be treated with surface treatments such as gold plating, immersion gold plating, and tin plating. The mainstream processing method for lead-tin plating involves exposing the patterned area and substrate area at the bottom of the blind slot after its fabrication, and then plating the entire board with tin. This results in a tin protective layer being applied to the patterned area at the bottom of the blind slot, while the substrate area remains unplated (the patterned area at the bottom of the blind slot is located in the inner circle, and the substrate area is located in the outer circle). However, because the blind slot is a recessed groove, solder beads easily accumulate on the sidewalls and edge gaps at the bottom of the blind slot after tin plating. Subsequent cleaning methods often fail to completely remove these solder beads, leading to a short-circuit risk when components are installed at the bottom of the blind slot. Summary of the Invention

[0003] To overcome the above problems, the present invention provides a method for tin-plating surface treatment of blind slot circuit boards. The technical solution adopted by the present invention to solve its technical problems is as follows: A method for tin plating surface treatment of a blind slot circuit board includes the following steps: Step S1, providing an inner layer board with a patterned design, the inner layer board having a blind slot bottom area, and a resist tape positioned directly above the blind slot bottom area; Step S2, providing an insulating dielectric sheet and an outer layer board, the insulating dielectric sheet having a window corresponding to the position of the blind slot bottom area; Step S3, aligning and stacking the outer layer board, the window of the insulating dielectric sheet aligning with the resist tape; Step S4, pressing the above stacked layers together to obtain a circuit board, and then drilling and electroplating copper on the circuit board to create the outer layer pattern; Step S5, processing the circuit board after step S1... In step S4, the circuit board undergoes a first milling of blind slots, milling vertically downwards from the outer layer board to the inner layer board to expose the graphic area at the innermost edge of the blind slot bottom area; in step S6, after the circuit board has undergone solder resist treatment in step S5, the circuit board undergoes a tin plating surface treatment to cover the outer layer graphic area and the graphic area at the bottom of the blind slot with a tin protective layer; in step S7, the circuit board has undergone step S6, and the blind slots are milled a second time, also milling vertically downwards from the outer layer board to the inner layer board to expose the substrate area at the outermost edge of the blind slot bottom area, resulting in a blind slot circuit board with tin plating surface treatment.

[0004] Furthermore, the adhesive resistance tape is a high-temperature resistant PI tape.

[0005] Furthermore, in step S2, the width of the window on one side is 1-3 mil greater than the width of the bottom area of ​​the blind groove on one side.

[0006] Furthermore, in step S3, after the outer layer, insulating dielectric sheet and inner layer are aligned and stacked, the four corners of the stack are riveted and fixed.

[0007] Furthermore, in step S5, the first milling of the blind groove includes the following steps: Step S501, milling off the material directly above the graphic area with a material milling cutter to expose the adhesive tape directly above the graphic area; Step S502, cutting the adhesive tape along the edge of the graphic area with an adhesive tape milling cutter; Step S503, removing the adhesive tape directly above the graphic area to expose the graphic area.

[0008] Furthermore, in step S7, the second milling of the blind groove includes the following steps: Step S701, milling off the tin protective layer and board material directly above the substrate area using a board milling cutter to expose the resist tape directly above the substrate area; Step S702, cutting the resist tape along the edge of the substrate area using a tape milling cutter; Step S703, removing the resist tape directly above the substrate area to expose the substrate area.

[0009] Furthermore, in steps S502 and S702, the tape milling cutter is a laser milling cutter.

[0010] Furthermore, in step S502, the tape milling cutter cuts the connection between the resist tape directly above the graphic area and the resist tape directly above the substrate area; in step S702, the tape milling cutter cuts the connection between the resist tape directly above the substrate area and the insulating dielectric sheet.

[0011] Furthermore, step S7 is followed by step S8: the blind slot circuit board that has passed step S7 is subjected to texturing, testing, molding and final inspection processes to obtain the finished circuit board.

[0012] The beneficial effects of this invention are: This method for processing blind slot circuit boards using tin plating involves two milling processes. The first milling process involves milling a small blind slot to expose the graphic area of ​​the original blind slot's bottom surface. Then, tin plating is performed, covering the graphic area with a tin protective layer. At the same time, solder beads may be hidden in the gaps on the sidewalls and bottom edges of the small blind slot milled in the first milling. Then, a second milling process is performed to remove the sidewalls and bottom edges of the small blind slot milled in the first milling to expose the substrate area of ​​the large blind slot, thus creating the required blind slot. Since the second milling process mechanically removes all the parts that may hide solder beads, there will be no solder beads hidden on the sidewalls and bottom edges of the tin-plated blind slot. This completely solves the problem of short circuits caused by hidden solder beads after tin plating of blind slots from a process perspective. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a schematic cross-sectional view of the circuit board after lamination in step S4 of the present invention. Figure 2 This is an exploded cross-sectional view of the circuit board after lamination in step S4 of the present invention. Figure 3 This is a schematic cross-sectional view of the circuit board after step S501 of the present invention. Figure 4 This is a schematic cross-sectional view of the circuit board after step S503 of the present invention. Figure 5 This is a schematic cross-sectional view of the circuit board after step S6 of the present invention. Figure 6 This is a schematic cross-sectional view of the circuit board after step S701 of the present invention. Figure 7 This is a schematic cross-sectional view of the circuit board after step S703 of the present invention.

[0014] Figure number marking: 100. Inner layer board; 101. Blind groove bottom area; 1011. Graphic area; 1012. Substrate area; 102. Resistant tape; 200. Insulating dielectric sheet; 201. Window opening; 300. Outer layer panel; 400. Tin protective layer. Detailed Implementation

[0015] To better understand the purpose, structure, and function of this invention, the following detailed description of specific embodiments of the "Method for Tin Spraying Surface Treatment of Blind Slot Circuit Board" is provided in conjunction with the accompanying drawings.

[0016] The tin-spraying surface treatment method for blind slot circuit boards of the present invention mainly aims to solve the problem that tin accumulation on the sidewalls and bottom edges of the blind slot in traditional tin-spraying surface treatment methods may lead to short circuits in components. It should be noted that tin-spraying surface treatment includes leaded tin-spraying and lead-free tin-spraying. This processing method includes the following steps: Step S1, as follows Figure 2 As shown, an inner layer board 100 with a pattern is provided. The inner layer board 100 can be a regular upper layer board or a multilayer board. The inner layer board 100 has a blind groove bottom area 101. The blind groove bottom area 101 includes a pattern area 1011 and a substrate area 1012. An adhesive barrier tape 102 is provided directly above the blind groove bottom area 101. The adhesive barrier tape 102 covers the entire blind groove bottom area 101. Step S2, as follows Figure 2 As shown, an insulating dielectric sheet 200 and an outer layer plate 300 are provided. The insulating dielectric sheet 200 is a semi-cured sheet, which melts and flows when exposed to high temperature and forms an insulating cured sheet after cooling and solidification. The outer layer plate 300 can also be a double-sided or multi-layer board. The insulating dielectric sheet 200 has a window 201 at the position corresponding to the bottom area 101 of the blind groove. Step S3, as follows Figure 1 and Figure 2 The outer layer 300, insulating dielectric sheet 200 and inner layer 100 are aligned and stacked as shown in the figure, and the opening 201 of the insulating dielectric sheet 200 is aligned with the positioning barrier tape 102. Step S4, the above-mentioned layers are pressed together to obtain the following: Figure 1 The circuit board shown is used to create the outer layer pattern after drilling and copper plating. Step S5: Perform a first blind slot milling on the circuit board after step S4. Mill vertically downwards from the outer layer board 300 to the inner layer board 100 to expose the graphic area 1011 at the inner circle of the bottom surface area 101 of the blind slot, as shown below. Figure 4 As shown; Step S6: After performing solder resist treatment on the circuit board in step S5, the circuit board undergoes a tin plating surface treatment to cover the outer layer pattern and the pattern area 1011 of the blind slot bottom area 101 of the circuit board surface with a tin protective layer 400. Figure 5 As shown; Step S7: Perform a second blind slot milling on the circuit board after step S6. The second blind slot milling also involves milling vertically downwards from the outer layer board 300 to the inner layer board 100 to expose the substrate area 1012 at the outer ring of the bottom surface area 101 of the blind slot, resulting in the following... Figure 7 The blind slot circuit board shown is after tin plating surface treatment.

[0017] In summary, the method for processing blind slots in the tin-plating surface treatment of this blind slot circuit board uses two milling processes. The first milling process involves milling a small blind slot to expose the inner ring graphic area 1011 of the original blind slot bottom area 101. Then, tin plating is performed, at which point the graphic area 1011 is covered with a tin protective layer. At the same time, solder balls may be hidden in the gaps on the sidewalls and bottom edges of the small blind slot milled in the first milling. Then, the second milling process is performed to mill away the sidewalls and bottom edges of the small blind slot milled in the first milling to expose the substrate area 1012 of the large blind slot, thus achieving the desired blind slot fabrication. Since the second milling process mechanically removes all the parts that may hide solder balls, there will be no solder balls hidden on the sidewalls and bottom edges of the tin-plated blind slot. This completely solves the problem of short circuits caused by hidden solder balls after tin plating surface treatment of blind slots from a process perspective.

[0018] It should be noted that, in this embodiment, the resist tape 102 is preferably a high-temperature resistant PI tape, which can withstand high temperatures during pressure bonding and effectively block the melted dielectric layer. Furthermore, this method includes step S8 after step S7: performing subsequent conventional processes such as texturing, testing, molding, and final inspection on the blind slot circuit board obtained in step S7 to obtain the finished circuit board.

[0019] More specifically, in this embodiment, the width of one side of the window 201 in step S2 is 1-3 mil larger than the width of one side of the bottom area 101 of the blind groove, so as to ensure that the window 201 can completely expose the adhesive tape 102 without overlapping, and to prevent the insulating dielectric sheet 200 from melting and flowing directly above the bottom area 101 of the blind groove.

[0020] Furthermore, in this embodiment, after the outer layer plate 300, the insulating dielectric sheet 200 and the inner layer plate 100 are aligned and stacked in step S3, the four corners of the stack are riveted and fixed to ensure that the stack will not be misaligned during the pressing process.

[0021] See further Figure 3 and Figure 4 In this embodiment, the first milling of the blind groove in step S5 includes the following steps: Step S501, milling away the board material directly above the graphic area 1011 with a board milling cutter to expose the adhesive barrier tape 102 directly above the graphic area 1011, such as... Figure 3 As shown; Step S502, cut the adhesive barrier tape 102 along the edge of the graphic area 1011 using a tape milling cutter; Step S503, remove the adhesive barrier tape 102 directly above the graphic area 1011 to expose the graphic area 1011, as shown. Figure 4 As shown.

[0022] See also Figure 6 and Figure 7In this embodiment, the second milling of the blind groove in step S7 includes the following steps: Step S701, milling away the tin protective layer 400 and the board material directly above the substrate area 1012 with a board milling cutter to expose the adhesive resist tape 102 directly above the substrate area 1012, such as... Figure 6 As shown; Step S702, cut the adhesive barrier tape 102 along the edge of the substrate area 1012 using an adhesive tape milling cutter; Step S703, remove the adhesive barrier tape 102 directly above the substrate area 1012 to expose the substrate area 1012, as shown. Figure 7 As shown.

[0023] More specifically, in this embodiment, in steps S502 and S702, the tape milling cutter is preferably a laser milling cutter; and in step S502, the tape milling cutter cuts the connection between the resist tape 102 directly above the graphic area 1011 and the resist tape 102 directly above the substrate area 1012; in step S702, the tape milling cutter cuts the connection between the resist tape 102 directly above the substrate area 1012 and the insulating dielectric sheet 200; ensuring that the resist tape 102 can be perfectly cut without damaging other layers of the circuit board.

[0024] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this application, "multiple" and "several" are understood as "at least two." "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. A connected to B can represent: A and B directly connected, and A and B connected through C. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A method for tin plating surface treatment of blind slot circuit boards, characterized in that, Includes the following steps: Step S1: Provide an inner layer board (100) with a pattern, the inner layer board (100) having a blind groove bottom area (101), and a barrier tape (102) is provided directly above the blind groove bottom area (101). Step S2, providing an insulating dielectric sheet (200) and an outer layer plate (300), wherein the insulating dielectric sheet (200) is provided with a window (201) at a position corresponding to the bottom area (101) of the blind slot; Step S3: Align and stack the outer layer (300), insulating dielectric sheet (200) and inner layer (100), with the opening (201) of the insulating dielectric sheet (200) aligned with the adhesive tape (102). Step S4: The above-mentioned layers are pressed together to obtain a circuit board. The circuit board is then drilled and plated with copper to create the outer layer pattern. Step S5: Perform a first milling of blind slots on the circuit board that has passed through step S4. Mill the board vertically downward from the outer layer board (300) to the inner layer board (100) to expose the graphic area (1011) at the inner circle of the bottom surface area (101) of the blind slot. Step S6: After performing solder resist treatment on the circuit board that has passed through step S5, perform tin spraying surface treatment on the circuit board so that the outer layer pattern on the surface of the circuit board and the pattern area (1011) of the bottom area (101) of the blind slot are covered with a tin protective layer (400). Step S7: Perform a second blind slot milling on the circuit board that has passed through step S6. The second blind slot milling is also a vertical downward milling from the outer layer board (300) to the inner layer board (100) to expose the substrate area (1012) at the outer ring position of the bottom area (101) of the blind slot, and obtain the blind slot circuit board after tin spraying surface treatment.

2. The method for surface treatment of blind slot circuit boards by tin plating according to claim 1, characterized in that, The adhesive barrier tape (102) is a high-temperature resistant PI tape.

3. The method for surface treatment of blind slot circuit boards by tin plating according to claim 1, characterized in that, The width of the opening (201) in step S2 is 1-3 mil wider than the width of the bottom area (101) of the blind groove.

4. The method for surface treatment of blind slot circuit boards by tin plating according to claim 1, characterized in that, In step S3, after the outer layer plate (300), insulating dielectric sheet (200) and inner layer plate (100) are aligned and stacked, the four corners of the stack are riveted and fixed.

5. The method for surface treatment of blind slot circuit boards by tin plating according to claim 1, characterized in that, In step S5, the first milling of the blind groove includes the following steps: Step S501, milling off the plate material directly above the graphic area (1011) with a plate milling cutter to expose the adhesive barrier tape (102) directly above the graphic area (1011); Step S502, cutting the adhesive barrier tape (102) along the edge of the graphic area (1011) with an adhesive tape milling cutter; Step S503, removing the adhesive barrier tape (102) directly above the graphic area (1011) to expose the graphic area (1011).

6. The method for tin-plating surface treatment of a blind slot circuit board according to claim 5, characterized in that, In step S7, the second milling of the blind groove includes the following steps: Step S701, milling off the tin protective layer (400) and the board material directly above the substrate area (1012) with a board milling cutter to expose the adhesive resistance tape (102) directly above the substrate area (1012); Step S702, cutting the adhesive resistance tape (102) along the edge of the substrate area (1012) with an adhesive tape milling cutter; Step S703, removing the adhesive resistance tape (102) directly above the substrate area (1012) to expose the substrate area (1012).

7. The method for tin plating surface treatment of a blind slot circuit board according to claim 6, characterized in that, In steps S502 and S702, the tape milling cutter is a laser milling cutter.

8. The method for tin plating surface treatment of a blind slot circuit board according to claim 7, characterized in that, In step S502, the tape milling cutter cuts the connection between the adhesive barrier tape (102) directly above the graphic area (1011) and the adhesive barrier tape (102) directly above the substrate area (1012); in step S702, the tape milling cutter cuts the connection between the adhesive barrier tape (102) directly above the substrate area (1012) and the insulating dielectric sheet (200).

9. The method for tin-plating surface treatment of a blind slot circuit board according to claim 1, characterized in that, Step S7 is followed by step S8: the blind slot circuit board that has passed step S7 is subjected to texturing, testing, molding and final inspection processes to obtain the finished circuit board.

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