Method for improving printed circuit board (PCB) molding gong board grey

Abstract

The invention discloses a method for improving PCB (printed circuit board) molding routing grey, which comprises the following steps: when an inner layer circuit is manufactured on a PCB, a plurality of copper PADs arranged at intervals are formed in a corresponding in-board routing groove area, and the distance between the outermost copper PAD and the edge of a molding line on the periphery of the in-board routing groove area is greater than or equal to 1mm; and when an outer layer circuit is manufactured on the PCB, etching and removing the copper sheet in the outer layer corresponding to the milling groove area in the board. According to the method, by changing the copper laying design of the inner layer and the outer layer, the heat during groove milling is reduced to improve and solve the problem of board ash on the edge of the groove milling.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printed circuit board manufacturing, and particularly relates to a method for improving PCB forming plate dust. BACKGROUND

[0002] In the process of manufacturing a printed circuit board, various shaped grooves need to be milled in the board for subsequent use in clamping components or dividing the board; when there is a demand to mill off the shaped groove or a large groove (groove waste area) in the board, plate dust will appear on the edge of the groove after milling; of course, in the process of manufacturing a printed circuit board, a common method is to use a plate assembly method, that is, there are multiple set plates (SRT plates are composed of at least one unit plate) on a PNL production plate, and when the set plate is formed and cut and the inner groove is milled, the process edge between the adjacent two set plates is also prone to the problem of plate dust during forming and cutting.

[0003] The main reason for the generation of plate dust in the groove is that the inner groove empty area of the board is too large, and if copper is not laid, copper wrinkles will appear during pressing, so copper is usually laid in the inner groove empty area, the edge of the plate, and the set process edge of the inner layer, that is, an entire copper sheet is laid at these positions to ensure that the resin flows smoothly during pressing and to avoid copper wrinkles during pressing, and the outer layer copper sheet at the corresponding position is generally not removed. Firstly, a large amount of heat is generated during the milling process of the milling cutter on the glass epoxy resin and the filler on the PCB, and since copper is laid on the formed milling plate waste area, the heat is sharply increased when the milling cutter contacts the copper sheet during milling, and the dust generated during milling will form a binding material under the action of heat, that is, plate dust will form on the edge of the groove; secondly, the milling cutter will wear more during the process of cutting the copper sheet, and the more the copper sheet is cut, the greater the wear will be, which will reduce the sharpness and cutting performance of the milling cutter, that is, the service life of the milling cutter will be affected, and when the milling cutter continuously cuts, the cutting heat will be greater and more concentrated as the cutting time increases, and the probability of plate dust will increase significantly.

[0004] In addition, although the milling machine itself has a dust collection function during milling, the milled dust is sucked away through a dust collection pipe, but not all dust can be timely sucked away, and in order to ensure the stability of the milling size, the pressure cylinder of the milling machine presses the plate on the milling machine platform through the plate pressing brush to ensure the stability of the milling. However, since the plate pressing brush has a certain pressure during plate pressing, the pressure will squeeze and accumulate the dust that has not been timely sucked away on the edge of the groove, thereby more easily causing the quality problem of plate dust.

[0005] In the prior art, in order to reduce plate dust, the industry usually reduces the milling cutter speed, which greatly reduces the milling efficiency, and since the milling cutter has the characteristics of large cutting feed during milling, the feed speed and the rotational speed are adjusted (the conventional milling cutter speed is 18 mm / s, which is reduced to 5 mm / s; the rotational speed is 36 K rpm / min, which is reduced to 20 K rpm / min), but the problem of plate dust during milling cannot be fundamentally solved. Summary of the Invention

[0006] In view of the above-mentioned technical defects, the present invention provides a method to improve the board dust of PCB forming routers. By changing the copper pouring design of the inner and outer layers, the heat generated during routering is reduced, thereby improving and solving the problem of board dust appearing at the edge of the router groove.

[0007] To solve the above-mentioned technical problems, the present invention provides a method for improving the dust on PCB forming and routing boards. When making inner layer circuits on the PCB, a number of spaced copper PADs are formed at the corresponding routing groove area in the board, and the distance between the outermost copper PAD and the edge of the forming line on the outer periphery of the routing groove area in the board is ≥1mm. When making outer layer circuits on the PCB, the copper foil in the corresponding routing groove area in the outer layer is etched away.

[0008] Furthermore, the outer diameter of the copper PAD is 1.25 mm.

[0009] Furthermore, the spacing between two adjacent copper PADs is 0.25 mm.

[0010] Furthermore, the copper PADs are arranged in multiple rows, and adjacent rows of copper PADs are staggered.

[0011] Furthermore, when routing grooves on the PCB, a pilot hole is first drilled at the initial cutting position in the routing groove area inside the board.

[0012] Furthermore, the diameter of the pilot hole is ≥2.0mm.

[0013] Furthermore, when routing grooves on the PCB, several pre-drilled holes are first drilled in the routing groove area inside the board.

[0014] Furthermore, the diameter of the pre-drilled hole is ≥2.0mm.

[0015] Furthermore, the PCB has multiple set boards. When the distance between two adjacent set boards is less than 2.5mm, no copper is laid at the process edge of the inner and outer set boards. When the distance between two adjacent set boards is greater than or equal to 2.5mm, copper is laid at the process edge of the inner set board, and the distance between the edge of the copper and the edge of the forming line of the process edge of the set board is greater than or equal to 1mm.

[0016] Furthermore, when routing grooves on the PCB, a router bit with a diameter of ≤1.6mm should be used.

[0017] Compared with the prior art, the present invention has the following beneficial effects: In this invention, the copper plating design of the inner layer's hollow area is first optimized by changing the original large area of ​​copper foil to several spaced copper pads. This reduces the copper plating area of ​​the inner layer, decreases the contact area between the router and the inner copper foil during routerting, and thus reduces the heat generated during routerting and the wear of the router, ensuring that the cutting performance and service life of the router can be maintained for a longer period of time. Furthermore, the distance between the outermost copper pad and the edge of the forming line on the outer periphery of the router area is ≥1mm, so that when the router cuts along the forming line, it does not contact the inner copper or the contact area is minimized, avoiding board dust caused by excessive heat at the edge of the router. The outer layer of the hollow area is not plating copper, further reducing the cutting resistance and heat during cutting.

[0018] Secondly, several pre-drilled holes are added to the groove area inside the board to serve as chip removal and heat dissipation holes. Firstly, dust can be discharged from the pre-drilled holes or accumulate in the pre-drilled holes, reducing the problem of dust accumulation on the edge of the groove and the board surface during the cutting process. Secondly, it can increase the heat dissipation effect during the cutting process, reduce the heat of the groove, and reduce the problem of board dust caused by heat. Thirdly, the setting of pre-drilled holes reduces the amount of grooves to be cut later and improves the cutting efficiency. Detailed Implementation

[0019] To better understand the technical content of this invention, the technical solution of this invention will be further introduced and explained below in conjunction with specific embodiments.

[0020] Example This embodiment illustrates a PCB manufacturing method, which includes a method for improving the dust on the PCB molding board, comprising the following processing steps in sequence: (1) Cutting: Cut the core board according to the panel size of 520mm×620mm. The core board is 0.5mm thick and the copper layer thickness on both surfaces of the core board is 0.5oz. The core board contains multiple set boards arranged in a panel arrangement (such as a square array or a centrally symmetrical arrangement). The production board has a board edge around its perimeter and a process edge between adjacent set boards.

[0021] (2) Inner layer circuit fabrication (negative film process): Inner layer pattern transfer, photosensitive film is coated using a vertical coating machine, and the film thickness of the photosensitive film is controlled at 8μm. The inner layer circuit is exposed using a fully automatic exposure machine with 5-6 exposure rulers (21 exposure rulers). After development, the inner layer circuit pattern is formed; Inner layer etching, the inner layer circuit is etched out on the core board after exposure and development. The inner layer line width is measured to be 3mil; Inner layer AOI, and then the inner layer circuit is inspected for defects such as open circuits, short circuits, line gaps, and line pinholes. Defective products are scrapped, and defect-free products are sent to the next process.

[0022] In one embodiment, when fabricating the inner layer circuitry, several spaced copper pads are formed simultaneously in the corresponding routing groove area of ​​the board. Here, by optimizing the copper plating design of the inner layer routing empty area, the original large area of ​​copper skin is modified to several spaced copper pads, thereby reducing the copper plating area of ​​the inner layer and reducing the contact area between the routing cutter and the inner layer copper skin when routing grooves. This reduces the heat generation and wear of the routing cutter during routing, ensuring that the cutting performance and service life of the routing cutter can be maintained for a longer period of time. Furthermore, the distance between the outermost copper pad and the edge of the forming line on the outer periphery of the routing groove area of ​​the board is ≥1mm, so that when the routing cutter cuts along the forming line, the area that does not contact the inner layer copper or the contact area is minimized, avoiding board dust caused by excessive heat at the edge of the routing groove. The outer layer of the hollow area is not plating copper, further reducing the cutting resistance and heat during cutting.

[0023] In one embodiment, the outer diameter of the copper PAD is 1.25mm, and the spacing between two adjacent copper PADs is 0.25mm. This can avoid the problem of copper wrinkling while minimizing the copper area of ​​the inner layer cutout. In this way, when the router cutter cuts the cutout area, the contact amount and release area between the router cutter and the inner copper layer can be reduced.

[0024] In one embodiment, several copper PADs in the same slot area of ​​the board are arranged in multiple rows, and adjacent rows of copper PADs are staggered to ensure that the slot area of ​​the board is fully filled with glue during lamination, and to avoid the problem of insufficient glue filling due to excessive glue flow, which would lead to copper wrinkles during lamination.

[0025] In one embodiment, when the spacing between two adjacent set boards is <2.5mm, the size of the routing gap formed between the set boards is small, and no copper is needed at the process edges of the inner and outer set boards. The copper-free design greatly reduces the heat generated during routing, thereby improving and solving the problem of board dust generated when routing at the process edges of the set boards. When the spacing between two adjacent set boards is ≥2.5mm, copper is laid at the process edges of the inner set board, and the distance between the edge of the copper and the edge of the forming line of the process edge of the set board is ≥1mm. This ensures that when the router cuts along the forming line, it does not contact the inner copper or the contact area is as small as possible, avoiding board dust caused by excessive heat when routing at the edges.

[0026] (3) Lamination: The browning speed is based on the thickness of the bottom copper. The core board, prepreg, and outer copper foil are stacked in sequence as required. Then, according to the Tg of the board material, appropriate lamination conditions are selected to press the laminated board to form the production board.

[0027] (4) Drilling: Drilling is performed on the production board according to the design requirements based on the existing drilling technology.

[0028] In one embodiment, during drilling, a pilot hole is drilled at the initial cutting position in the slotting area within the board to ensure that there is no copper at the cutting position, reducing cutting resistance. The pilot hole can also be used as a chip removal hole, which facilitates cutting and chip removal during slotting, allowing dust from the pilot hole to be discharged or accumulated in the pre-drilled hole.

[0029] Specifically, the diameter of the pilot hole should be ≥2.0mm, which is larger than the diameter of the router bit, which is generally ≤1.6mm.

[0030] In one embodiment, during drilling, several pre-drilled holes are simultaneously drilled in the groove area within the board, serving as chip removal holes and heat dissipation holes. Firstly, dust can be discharged from or accumulate within the pre-drilled holes, reducing the problem of dust accumulation on the groove edge and board surface during cutting. Secondly, it can increase the heat dissipation effect during the cutting process, reducing the heat in the groove and thus reducing the problem of board dust caused by heat. Thirdly, the setting of pre-drilled holes reduces the amount of groove cutting required when cutting the groove area within the board later, improving the cutting efficiency.

[0031] Specifically, the diameter of the pre-drilled hole should be ≥2.0mm.

[0032] (5) Copper plating: A thin layer of copper is deposited on the board surface and hole walls using chemical copper plating. The backlight test is level 10, and the copper plating thickness in the hole is 0.5μm.

[0033] (6) Full-board electroplating: The production board is subjected to full-board electroplating treatment.

[0034] (7) Fabrication of outer layer circuits (positive film process): The outer layer pattern is transferred using a fully automatic exposure machine and positive film circuit film. The outer layer circuit is exposed using an exposure ruler of 5 to 7 divisions (21 divisions). After development, the outer layer circuit pattern is formed on the production board. The outer layer pattern is electroplated, and then copper and tin are plated on the production board respectively. The electroplating parameters are set according to the required copper thickness. Copper plating is performed at a current density of 1.8 ASD for 60 minutes, and tin plating is performed at a current density of 1.2 ASD for 10 minutes, with a tin thickness of 3 to 5 μm. Then, the film is removed, etched, and tin is removed in sequence to etch the outer layer circuit on the production board. The outer layer AOI is performed using an automatic optical inspection system. By comparing with the CAM data, the outer layer circuit is checked for defects such as open circuits, gaps, incomplete etching, and short circuits.

[0035] When fabricating the outer layer circuitry, the copper layer in the corresponding routing area and the edge of the set board process is removed by etching, ensuring that there is no copper foil in the outer layer of the routing area, which further reduces cutting resistance and heat during cutting.

[0036] (8) Solder resist and screen printing: After screen printing solder resist ink on the surface of the multilayer board, it is then subjected to pre-curing, exposure, development and heat curing treatment in sequence to cure the solder resist ink into a solder resist layer; specifically, the solder resist ink on the TOP side and the characters on the TOP side are added with "UL mark", thereby coating a layer on the lines and substrates that do not need to be soldered to prevent bridging between lines during soldering, provide a permanent electrical environment and chemical corrosion resistance, and at the same time beautify the appearance.

[0037] (9) Surface treatment (immersion nickel and gold): The copper surface of the solder pads of the solder mask opening position is uniformly deposited with a nickel layer and a gold layer of a certain required thickness through chemical principle. The thickness of the nickel layer is 3-5μm; the thickness of the gold layer is 0.05-0.1μm.

[0038] (10) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0039] (11) Molding: Based on existing technology and according to design requirements, the PCB is made with the external shape and internal groove of the PCB, with an external tolerance of + / -0.05mm.

[0040] (12) FQC: In accordance with the customer's acceptance standards and the applicant's inspection standards, inspect the appearance of the PCB to ensure the smoothness of the surface of the groove edge, meet the quality requirements of appearance, groove wall without residual glass fiber and board dust, etc., and repair any defects in a timely manner to ensure excellent quality control for the customer.

[0041] (13) FQA: Re-test the appearance of the PCB, the thickness of the hole copper, the thickness of the dielectric layer, the thickness of the green solder mask, the thickness of the inner layer copper, etc. to see if they meet the customer's requirements.

[0042] (14) Packaging: The PCBs are sealed and packaged according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in the packaging before shipment.

[0043] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for improving the dust on PCB molding boards, characterized in that, When fabricating inner layer circuits on a PCB, several spaced copper pads are formed at the corresponding slot area within the board, and the distance between the outermost copper pad and the edge of the forming line on the outer perimeter of the slot area is ≥1mm; when fabricating outer layer circuits on a PCB, the copper foil at the corresponding slot area within the board is etched away.

2. The method for improving PCB molding board dust according to claim 1, characterized in that, The outer diameter of the copper PAD is 1.25 mm.

3. The method for improving PCB molding board dust according to claim 1 or 2, characterized in that, The spacing between two adjacent copper PADs is 0.25mm.

4. The method for improving PCB molding board dust according to claim 1, characterized in that, The copper PADs are arranged in multiple rows, and adjacent rows of copper PADs are staggered.

5. The method for improving PCB molding board dust according to claim 1, characterized in that, When routing grooves on a PCB, first drill a pilot hole at the initial cutting position in the routing groove area on the board.

6. The method for improving PCB molding board dust according to claim 5, characterized in that, The diameter of the pilot hole is ≥2.0mm.

7. The method for improving PCB molding board dust according to claim 1, characterized in that, When routing grooves on a PCB, several pre-drilled holes are first drilled in the routing groove area inside the board.

8. The method for improving PCB molding board dust according to claim 7, characterized in that, The diameter of the pre-drilled hole is ≥2.0mm.

9. The method for improving PCB molding board dust according to claim 1, characterized in that, The PCB has multiple set boards. When the distance between two adjacent set boards is less than 2.5mm, no copper is laid at the process edge of the inner and outer set boards. When the distance between two adjacent set boards is greater than or equal to 2.5mm, copper is laid at the process edge of the inner set board, and the distance between the edge of the copper and the edge of the forming line of the process edge of the set board is greater than or equal to 1mm.

10. The method for improving PCB molding board dust according to claim 1, characterized in that, When routing grooves on a PCB, use a router bit with a diameter of ≤1.6mm.