A method for detecting deviation of PCB forming gong plate

Abstract

The present invention discloses a method for detecting the deviation of a PCB forming gong plate, comprising the following steps: when making each layer of circuits on a production board, a detection unit is made on a process edge, the detection unit comprising two first PADs arranged in parallel and a second PAD spaced apart and arranged at one end of the first PAD, the second PAD being perpendicular to the first PAD; a solder mask is made on the production board, and a window is opened in the solder mask at a position corresponding to the detection unit to reveal the detection unit; in the process of forming the gong plate, a gong groove is made between the two first PADs and between the first PAD and the second PAD to gong through the production board to form a detection groove; the vertical distance between the groove edge of the detection groove and the first PAD and the second PAD is less than the minimum vertical distance between the copper inside the board and the outer edge; by observing whether there is exposed copper on the groove wall, it is determined whether the board is gong-biased. The method of the present invention can replace the measurement, inspection and screening of products by two-dimensional machine equipment with visual inspection, thereby improving product disposal efficiency and reducing costs.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, and in particular to a method for detecting the deviation of a PCB forming gong plate. Background Art

[0002] PCB gong board forming is a common machining method. The board from the previous process is placed on the gong machine, and the high-speed rotation and vacuum adsorption of the gong knife are used to separate the SET board or PCS board and the substrate on the circuit board, thereby realizing the forming of the circuit board; in the PCB industry, the distance from the outer edge (i.e. the cutting edge) to the copper inside the board is designed to be ≤0.2mm, and the outer dimension tolerance from edge to edge is ±0.1mm. The outer dimension requirements are high, and the gong is not allowed to deviate from the position and expose the copper. When the gong board is made in the forming process, the gong board operation is generally performed according to the expansion and contraction coefficient provided by the previous process. This processing method has the advantages of high efficiency and low cost, and is widely used in the PCB manufacturing industry.

[0003] However, the above production method has the following disadvantages:

[0004] During the PCB production process, due to problems with the characteristics of materials, processes, etc., some processes produce different amounts of expansion and contraction. If the operation is only based on the expansion and contraction coefficient of the previous process, there is a large mismatch between the expansion and contraction coefficient of the previous process and the actual expansion and contraction coefficient during the PCB production process. If the production process is completely in accordance with the expansion and contraction coefficient provided by the previous process, it is very easy to cause the product to be scrapped due to PCB deviation. When the board is PCB-deflected and copper is exposed, there is a lack of a method that can warn of the risk of PCB deviation in advance, and use visual inspection after the PCB deviation is found to quickly screen out unqualified products. Usually, the entire outer edge of each molded board is measured with a two-dimensional measuring device for product selection and disposal, which is inefficient and has high labor costs. It is also impossible to give a PCB deviation warning in advance, and the problem can only be dealt with after the PCB deviation and copper exposure occurs. Summary of the Invention

[0005] In view of the above-mentioned existing technical defects, the present invention provides a method for detecting the deviation of PCB forming gong plates, which can replace equipment measurement with visual inspection, improve efficiency and reduce costs.

[0006] In order to solve the above technical problems, the present invention provides a method for detecting the deviation of a PCB forming gong plate, comprising the following steps:

[0007] S1. When fabricating each layer of circuits on a production board, a detection unit is fabricated on a process edge. The detection unit comprises two parallel first PADs and a second PAD spaced apart from one end of the first PADs, wherein the second PAD extends perpendicular to the first PAD.

[0008] S2. Making a solder mask layer on the production board, and opening a window in the solder mask layer at a position corresponding to the detection unit to reveal the detection unit;

[0009] S3. During the forming process of the gong board, gong grooves are simultaneously performed between the two first PADs and between the first PAD and the second PAD to gong through the production board to form a test groove; the vertical distance between the groove edge of the test groove and the first PAD and the second PAD is less than the minimum vertical distance between the copper inside the board and the outer edge;

[0010] S4. Observe and inspect whether there is exposed copper on the wall of the slot to determine whether the board is deflected.

[0011] Furthermore, in step S1, when each layer of circuits is produced on the production board, at least one detection unit is produced on the process edge of each set board.

[0012] Furthermore, in step S1, when each layer of circuits is produced on the production board, at least one detection unit is produced on the process edge of each PCS board.

[0013] Furthermore, in step S1 , both ends of the second PAD are respectively located on one side of the ends of the two first PADs, so that the area between the two first PADs and the second PAD forms a T-shaped area.

[0014] Furthermore, in step S2, a window is opened in the solder resist layer at the middle position corresponding to the T-shaped area to form a T-shaped groove area, and the outer periphery of the groove area is retracted by 1-2 mm relative to the outer periphery of the T-shaped area.

[0015] Furthermore, in step S3, during the process of forming the gong plate, the plate at the gong groove area is cut and removed to form a T-shaped detection groove.

[0016] Furthermore, in step S3, the vertical distance between the groove edge of the detection groove and the first PAD and the second PAD is 0.025 mm smaller than the minimum vertical distance between the copper inside the board and the outer edge.

[0017] Furthermore, in step S1, the second PAD is located on one side of an end portion of one of the first PADs, and the length of the second PAD is greater than or equal to the width of the first PAD.

[0018] Furthermore, the length of the first PAD and the width of the second PAD are both 3 mm and 0.7 mm.

[0019] Furthermore, the production board is a multi-layer board in which the inner core board and the outer copper foil are pressed together by a semi-cured sheet, and the multi-layer board has undergone the processes of drilling, copper deposition, full-board electroplating and outer layer circuit production in sequence.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] In the present invention, first, when making each layer of circuit, a detection unit including the first PAD and the second PAD is made in the process edge, and then a groove is made in the internal area of ​​the detection unit in the forming process to form a detection groove, so that the exposed copper condition of the groove wall of the detection groove can be visually inspected to identify whether the product has the risk of exposed copper, instead of the existing method of using equipment measurement, thereby improving inspection efficiency and reducing costs; and because the vertical distances between the groove edge of the detection groove and the first PAD and the second PAD are both less than the minimum vertical distance between the copper in the board and the outer edge, when the detection groove is found to be exposed copper When there is exposed copper on the groove wall, it means that the board has a problem of gong deviation and is judged as a risky product, which serves as an early warning of gong deviation. However, it does not mean that there is exposed copper on the outer edge of the board. Further visual inspection is required to determine whether there is exposed copper on the entire outer edge, and a full inspection should be conducted on the outer edges of all the gonged boards to determine whether there is exposed copper. The defective products should be picked out and disposed of. After the product has gong deviation and copper exposure, it can be quickly inspected and disposed of, thereby improving efficiency. In addition, the deviation direction can be confirmed by detecting whether the exposed copper on the groove wall deviates from the position of the first PAD or the second PAD, and the subsequent gong board processing parameters can be adjusted according to the deviation direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a detection unit fabricated on the process edge of each circuit layer of a production board in an embodiment;

[0023] Figure 2 This is a schematic diagram of the embodiment after a solder mask layer is formed on a production board and a window is opened in the middle of a detection unit to form a gong groove area;

[0024] Figure 3 This is a schematic diagram of the embodiment after the inspection groove is gonged out of the gong groove area of ​​the production board;

[0025] Figure 4 Schematic diagram of a detection unit in another embodiment when the second PAD does not cover the two ends of the first PAD;

[0026] Figure 5 Schematic diagram of a detection unit in another embodiment in which a second PAD is provided on each side of both ends of the first PAD. DETAILED DESCRIPTION

[0027] In order to more fully understand the technical content of the present invention, the technical solution of the present invention will be further introduced and illustrated in conjunction with specific embodiments below.

[0028] Example

[0029] The present embodiment shows a method for manufacturing a circuit board, which includes a process for solder resisting with a variegated ink, and includes the following processing steps in sequence:

[0030] (1) Cutting: Cut the core board according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm, and the thickness of the copper layer on both surfaces of the core board is 0.5oz. Multiple unit boards are formed on the core board according to preset rules.

[0031] (2) Inner layer circuit production (negative film process): Inner layer pattern transfer, use a vertical coating machine to coat the photosensitive film, the film thickness of the photosensitive film is controlled at 8μm, and a fully automatic exposure machine is used to complete the exposure of the inner layer circuit with a 5-6 grid exposure ruler (21 grid exposure ruler). After development, the inner layer circuit pattern is formed, and at least one detection unit pattern is formed on the process edge of each set board or pcs board; inner layer etching, the exposed and developed core board is etched to etch the inner layer circuit and the detection unit on the process edge. The inner layer line width is measured to be 3mil; inner layer AOI, and then check the inner layer circuit for defects such as open and short circuits, circuit gaps, and circuit pinholes. Defective products are scrapped, and products without defects are sent to the next process.

[0032] Among the above, Figure 1 As shown, the detection unit includes two first PAD1 arranged in parallel and a second PAD2 spaced apart at one end of the first PAD1 , and the extension direction of the second PAD2 is perpendicular to the extension direction of the first PAD1 .

[0033] In one embodiment, both ends of the second PAD are located on one side of the ends of the two first PADs, that is, the second PAD can span and cover the ends of the two first PADs, so that the area between the two first PADs and the second PAD forms a T-shaped area.

[0034] In one embodiment, the length of the first PAD1 and the width of the second PAD2 are both 3 mm and 0.7 mm.

[0035] In one embodiment, the set board is the shipping unit after post-forming and cutting, which includes at least one unit board (ie, PCS board), so that the detection unit is used to realize the deviation detection of each shipping unit.

[0036] In one embodiment, when the shipping unit after forming and cutting is a PCS board (ie, a unit board), at least one inspection unit needs to be manufactured on the process edge of each PCS board.

[0037] In another embodiment, Figure 4 As shown, the second PAD2 can also be located on one side of the end of one of the first PAD1, and the length of the second PAD ≥ the width of the first PAD, that is, the second PAD does not need to cover the ends of the two first PADs, and the detection groove formed during the subsequent molding is correspondingly L-shaped.

[0038] In yet another embodiment, Figure 5As shown, two second PAD2s can also be set, and the two second PAD2s are respectively arranged on one side of the two ends of the first PAD1, and the length of the second PAD2 covers the ends of the two first PAD1s, so that an I-shaped area is formed between the four PADs, and the detection groove gonged out during the subsequent molding is correspondingly I-shaped.

[0039] (3) Lamination: The browning speed is based on the browning thickness of the bottom copper. The core board, prepreg, and outer copper foil are laminated in sequence as required. Then, appropriate lamination conditions are selected according to the Tg of the sheet material to press the laminated board to form a production board.

[0040] (4) Drilling: Based on existing drilling technology, drilling is performed on the production board according to design requirements.

[0041] (5) Copper plating: A thin layer of copper is deposited on the board surface and the hole wall using the chemical copper plating method. The backlight test is level 10, and the thickness of the copper plating in the hole is 0.5μm.

[0042] (6) Full-board electroplating: Full-board electroplating is performed at a current density of 18ASF for 120 minutes to thicken the copper layer on the hole and the board surface.

[0043] (7) Production of outer layer circuits (positive film process): Transfer of outer layer patterns, using a fully automatic exposure machine and positive film circuit film, with a 5-7 grid exposure ruler (21 grid exposure ruler) to complete the exposure of the outer layer circuit, after development, the outer layer circuit pattern is formed on the production board, and at least one detection unit pattern is formed on the process edge of each set board or pcs board; electroplating of the outer layer pattern, and then copper plating and tin plating respectively on the production board, setting the electroplating parameters according to the required copper thickness, copper plating is 1.8ASD current density electroplating for 60 minutes on the whole board, tin plating is 1.2ASD current density electroplating for 10 minutes, tin thickness 3-5μm; then stripping, etching and tin stripping are carried out in sequence, etching the outer layer circuit on the production board and etching the detection unit on the process edge; outer layer AOI, using an automatic optical inspection system, by comparing with the CAM data, detect whether the outer layer circuit has defects such as open circuit, gap, incomplete etching, short circuit, etc.

[0044] In the above description, the detection pattern in the outer layer circuit is identical to the detection unit in the inner layer and is located at the same vertical projection position.

[0045] In another embodiment, the positions of the detection units in the outer circuit layer may be different from those in the inner circuit layer.

[0046] (8) Solder mask and silk screen characters: After silk screen printing solder mask ink on the surface of the production board, it is sequentially subjected to pre-curing, exposure, development and heat curing treatment to solidify the solder mask ink into a solder mask layer, and the solder mask layer is opened at the position corresponding to the detection unit and at the middle position corresponding to the T-shaped area to reveal the detection unit and the T-shaped groove area 3 (such as Figure 2 As shown in the figure, the periphery of the gong groove area is retracted by 1-2mm relative to the periphery of the T-shaped area, that is, the distance between the edge of the gong groove area and the detection unit is 1-2mm, and the vertical distances between the edge of the gong groove area and the first PAD and the second PAD are both smaller than the minimum vertical distance between the copper in the board and the outer edge; specifically, the solder mask ink on the TOP surface and the characters on the TOP surface add "UL mark", so that a layer is coated on the circuits and substrates that do not need to be soldered to prevent bridging between circuits during soldering, provide a permanent electrical environment and a protective layer against chemical corrosion, and at the same time beautify the appearance.

[0047] Preferably, the vertical distance between the edge of the groove area and the first PAD and the second PAD is 0.025 mm smaller than the minimum vertical distance between the copper in the board and the outer edge. The minimum vertical distance from the copper in the board to the outer edge is the minimum vertical distance from the circuit copper layer in the set board or pcs board to the outer edge.

[0048] (9) Surface treatment (nickel-gold deposition): The copper surface of the pad at the solder mask window position is chemically deposited with a nickel layer and a gold layer of a certain required thickness. The nickel layer thickness is 3-5μm; the gold layer thickness is 0.05-0.1μm.

[0049] In one embodiment, in order to reduce costs, a coating resist may be first formed on the detection unit to prevent the first PAD and the second PAD from being plated with a nickel-gold layer; the coating resist may preferably be a dry film, which is then affixed to the board and then exposed and developed.

[0050] (10) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0051] (11) Molding: According to the existing technology and the design requirements of the gong shape, the shape tolerance is + / -0.05mm, and the delivery unit set plate or pcs plate is made; in the process of forming the gong plate, cutting is performed along the edge of the gong groove area to cut through the plate and remove the plate at the gong groove area to form a T-shaped detection groove 4 (such as Figure 3 As shown in FIG, the vertical distance between the edge of the detection slot and the first PAD and the second PAD is designed to be 0.025 mm smaller than the minimum vertical distance between the copper inside the board and the outer edge.

[0052] In the above, whether there is exposed copper on the wall of the inspection tank can be observed to determine whether there is a problem of plate deviation. When exposed copper is found on the wall of the inspection tank, it means that the board has a problem of plate deviation and is judged as a risky product, which serves as an early warning of plate deviation. However, it does not mean that there is exposed copper on the outer edge of the board. Further visual inspection is required to determine whether there is exposed copper on the outer edge, and a full inspection should be carried out on the outer edges of all the boards that have been plated to determine whether there is exposed copper. The defective products will be picked out and disposed of, and the product can be quickly inspected and disposed of after plate deviation and copper exposure occurs, thereby improving efficiency. When no exposed copper is found on the wall of the tank, the board is not deflected and is judged as an OK product.

[0053] In addition, by cooperating with two parallel first PADs and the detection slot therebetween, it is possible to observe which side of the first PAD the slot wall is close to where the exposed copper is, so that the left and right side deviation directions can be known, thereby realizing the identification of the left and right side deviation conditions; and by cooperating with the first PAD and the second PAD and the detection slot therebetween, it is possible to observe whether the slot wall is close to the end of the first PAD or the slot wall is close to the second PAD, so that the front and rear side deviation directions can be known, thereby realizing the identification of the front and rear side deviation conditions, thereby finally confirming the deviation direction of the gong shape, and then adjusting the subsequent gong plate processing parameters according to the deviation direction.

[0054] (12) FQC: Inspect the appearance of the circuit board according to the customer's acceptance standards and our inspection standards. If there are any defects, repair them in time to ensure that we provide customers with excellent quality control.

[0055] (13) FQA: Re-test the appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness of the circuit board to see if they meet the customer's requirements.

[0056] (14) Packaging: According to the packaging method and packaging quantity required by the customer, the circuit board is sealed and packed, and desiccant and humidity card are placed before shipment.

[0057] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for detecting the deviation of a PCB forming gong plate, characterized in that: The following steps are involved: S1. When making each layer of circuits on the production board, at least one detection unit is made on the process edge of each set board or PCS board. The detection unit includes two parallel first PADs and a second PAD spaced apart at one end of the first PAD. The extension direction of the second PAD is perpendicular to the extension direction of the first PAD; the two ends of the second PAD are respectively located on one side of the end of the two first PADs, so that the area between the two first PADs and the second PAD forms a T-shaped area. S2. Making a solder mask layer on the production board, and opening a window in the solder mask layer at a position corresponding to the detection unit to reveal the detection unit; S3. During the forming process of the gong board, gong grooves are simultaneously performed between the two first PADs and between the first PAD and the second PAD to gong through the production board to form a test groove; the vertical distance between the groove edge of the test groove and the first PAD and the second PAD is less than the minimum vertical distance between the copper inside the board and the outer edge; S4. Observe the groove wall of the inspection groove to see if there is any exposed copper to determine whether the board is skewed. If exposed copper is found on the groove wall of the inspection groove, it means that the board has a skew problem and is judged as a risky product, which serves as an early warning of skew. However, it does not mean that there is exposed copper on the outer edge of the board. Further visual inspection is required to determine whether there is exposed copper on the outer edge of the board, and all the outer edges of the boards that have been skewed should be inspected to see if there is exposed copper. The defective products will be picked out and disposed of. If no exposed copper is found on the groove wall, the board is not skewed and is judged as an OK product.

2. The method for detecting the deviation of the PCB forming gong plate according to claim 1, characterized in that: In step S2, a window is opened in the solder resist layer at the middle position corresponding to the T-shaped area to form a T-shaped groove area, and the outer periphery of the groove area is retracted 1-2 mm relative to the outer periphery of the T-shaped area.

3. The method for detecting the deviation of the PCB forming gong plate according to claim 2, characterized in that: In step S3, during the process of forming the gong plate, the plate at the gong groove area is cut and removed to form a T-shaped detection groove.

4. The method for detecting the deviation of a PCB forming gong plate according to any one of claims 1 to 3, characterized in that: In step S3, the vertical distance between the groove edge of the detection groove and the first PAD and the second PAD is 0.025 mm smaller than the minimum vertical distance between the copper inside the board and the outer edge.

5. The method for detecting the deviation of the PCB forming gong plate according to claim 1, characterized in that: In step S1 , the second PAD is located at one end of one of the first PADs, and the length of the second PAD is greater than or equal to the width of the first PAD.

6. The method for detecting the deviation of the PCB forming gong plate according to claim 1, characterized in that: The length of the first PAD and the second PAD are both 3 mm, and the width are both 0.7 mm.

7. The method for detecting the deviation of the PCB forming gong plate according to claim 1, characterized in that: The production board is a multi-layer board in which the inner core board and the outer copper foil are pressed together by a semi-cured sheet, and the multi-layer board has undergone the processes of drilling, copper deposition, full-board electroplating and outer layer circuit production in sequence.

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