Method for manufacturing optical identification points of PCB (Printed Circuit Board)

Abstract

The invention relates to the technical field of PCB identification, in particular to an optical identification point manufacturing method of a PCB and an optical point structure, and the method comprises the following steps: S1, adding a process edge on a long edge of the PCB, and arranging the optical point structure on the process edge; s2, melting the tin bar in a tin cylinder through high temperature to form soldering tin alloy slurry of copper, tin and nickel in a proper proportion; and S3, the PCB is immersed in a tin furnace for a period of time, relevant parameters of a tin spraying machine and an air knife are adjusted to a proper range, and hot air leveling is conducted on the PCB. And S4, the PCB is taken out, whether the tin spraying thickness meets the requirement or not is checked, and if not, the air pressure of the tin spraying machine is adjusted. And S5, fixing the PCB which is processed and meets the requirement, and adjusting a lens to identify the PCB. Compared with the prior art, the copper optical points on the surface of the PCB are exposed through the solder resist windowing of the point A, the color of the base material below the point A is exposed, identification is convenient, the point B adopts the NPTH hole, the solder resist windowing is also used, and the point A and the point B control the tin thickness meeting the requirement through the tin spraying process.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB identification, and more specifically to a method for manufacturing optical identification points on a PCB board. Background Art

[0002] In the field of PCB board processing, solder mask processing needs to be carried out first, and then lead-free solder spraying treatment is performed on the surface of the PCB board. The required solder spraying thickness is 2 - 40um. However, due to the reflection of the white solder mask ink, the production line equipment frequently has problems with the inability to identify optical points. Moreover, due to the relatively thick solder spraying thickness, water droplets may form on the surface of the optical points, resulting in the scattering of the identification light, and the equipment cannot clearly identify the contour of the optical points. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a method for manufacturing optical identification points on a PCB board. Two optical point structures are designed on a PCB board, increasing the color difference around the optical points, enabling us to distinguish the contour of the optical points during identification. The optical points form a tolerance for each other, reducing the waste of repeated identification and rework.

[0004] To achieve the above object, a method for manufacturing optical identification points on a PCB board is designed, including the following steps: S1: Add a process edge to the long side of the PCB board, and set an optical point structure on the process edge. The optical point structure includes optical point A, optical point B, and positioning holes. The optical points have various forms. S2: Melt the solder bar in a tin bath at high temperature to form a solder alloy paste of copper, tin, and nickel in a suitable proportion. S3: Immerse the PCB board in a tin furnace for a period of time, adjust the relevant parameters of the solder spraying machine and the air knife to a suitable range, and perform hot air leveling on the PCB board. S4: Take out the PCB board and check whether the solder spraying thickness meets the requirements. If not, adjust the air pressure of the solder spraying machine. S5: Fix the processed PCB board that meets the requirements, and adjust the lens to identify the PCB board.

[0005] For the optical point A described in S1, a solder mask opening process is adopted. The copper around the optical point A is etched away with a diameter of 4mm. The optical point B can be an NPTH hole, and the copper around the optical point B is also etched away with a diameter of 1.6mm by using a solder mask opening etching process.

[0006] The shapes of the optical point A and the optical point B described in S1 can be circular, square, diamond, or any shape with four or fewer sides.

[0007] The overall optical point structure needs to be staggeredly distributed at the four corners of the PCB board. The horizontal distance d1 between the center of the optical point A and the center of the positioning hole is d1≥11mm, and the horizontal distance d2 between the center of the optical point A and the center of the optical point B is d2≥8mm.

[0008] The centers of the optical point A and the optical point B are on the same horizontal line. The distance d3 between the center of the optical point A and the edge of the board is greater than 2 mm. The distance d4 between the center of the positioning hole and the edge of the board needs to differ from the distance d3 by more than 0.5 mm.

[0009] The solder bar described in S2 The solder bar described in S2 can be selected from SN100-1, SN100-2, SN100-3. The copper content of SN100-1 is 0.5-0.7%, and the nickel content is 0.040-0.070%. The copper content of the solder bar SN100-2 is 0-0.4%, and the nickel content is 0.040-0.070%. The copper content of the solder bar SN100-3 is 0-0.4%, and the nickel content is 0.13-0.17%.

[0010] The temperature of the solder furnace described in S2 is between 260°C and 280°C, and the stirring temperature of the solder alloy paste is controlled between 260°C and 280°C.

[0011] The dipping time of the PCB board described in S3 is controlled within 2-6 seconds, and the rising speed of the PCB board lifted from the solder alloy paste by the spray soldering machine's hanging board is about 600-1200 mm / s.

[0012] The blowing time for the PCB each time described in S3 is 1-3 seconds. The air knife parameters that need to be adjusted include: the temperature of the front and rear air knives is controlled between 385°C and 420°C, the pressure of the front and rear air knives is controlled between 6.5 kg / cm² and 2.5 kg / cm², the total air pressure output is controlled between 6 and 9 kg, the angle of the front air knife is controlled between 3° and 5°, and the angle of the rear air knife is controlled between 4° and 7°.

[0013] Compared with the prior art, in the present invention, the copper optical points on the surface of the PCB are exposed through the solder mask opening at point A, and the color of the underlying substrate is revealed for easy identification. Point B uses NPTH holes and also uses a solder mask opening. The tin thickness requirements for points A and B are met through the process control of spray soldering. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic structural diagram of a PCB board.

[0015] Figure 2 It is a schematic structural diagram of a narrow process edge.

[0016] Figure 3 It is a schematic structural diagram of a non-copper-plated PCB board.

[0017] Figure 4 It is a flow chart of the present invention.

[0018] See Figures 1 to 4 , 1 is the optical point A, 2 is the optical point B, and 3 is the positioning hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] As Figure 4 shown, the present invention includes the following steps: S1: Add a process edge to the long side of the PCB board, and set an optical point structure on the process edge. As Figure 1 shown, the optical point structure includes optical point A1, optical point B2, and positioning hole 3. The optical points have various forms. Setting two optical points can increase fault tolerance. When one cannot be recognized, the other optical point can still be recognized, reducing the inefficiency caused by repeated rework. The shapes of optical point A1 and optical point B2 can be circular, square, diamond, or any shape with less than or equal to four sides. The shape of the optical point should have less than 4 sides. A simpler optical point shape is more convenient for manual selection of points and lines to determine the center of the optical point. The area around optical point A1 uses the solder mask opening process. The copper around optical point A1 is etched away with a diameter of 4 mm of copper. Optical point B2 can be an NPTH hole. The same solder mask opening etching with a diameter of 1.6 mm of copper is also used around optical point B2. The purpose of the solder mask opening is to show the color of the original substrate with an obvious contrast to the color of the surrounding auxiliary copper for easy recognition and to prevent white ink from entering the hole. The optical point structure as a whole needs to be staggeredly distributed at the four corners of the PCB board, so that positioning can be more accurate. The horizontal distance d1 between the center of optical point A1 and the center of positioning hole 3 is d1≥11 mm, and the horizontal distance d2 between the center of optical point A1 and the center of optical point B2 is d2≥8 mm. This is to ensure that within the shooting range of the recognition lens, there is only the pattern of optical point A1 or optical point B2, avoiding recognition errors. The centers of optical point A1 and optical point B2 are on the same horizontal line, which is to facilitate the movement of the recognition lens. The distance d3 between the center of optical point A1 and the board edge is d3>2 mm, and the distance d4 between the center of positioning hole 3 and the board edge needs to differ from the distance d3 of the board edge by more than 0.5 mm. The purpose of doing this is to distinguish the coordinate positions of the optical point and the positioning hole.

[0021] S2: Mix and melt different types of solder bars SN100-1, SN100-2, and SN100-3 in a tin bath at high temperature, and stir to form a solder alloy paste with a suitable ratio of copper, tin, and nickel. The copper content of solder bar SN100-1 is 0.5 - 0.7%, and the nickel content is 0.040 - 0.070%. The copper content of solder bar SN100-2 is 0 - 0.4%, and the nickel content is 0.040 - 0.070%. The copper content of solder bar SN100-3 is 0 - 0.4%, and the nickel content is 0.13 - 0.17%. The contents of copper, tin, and nickel are controlled by adding different types of solder bars. SN100-1 is used to supplement the copper content when starting the bath, and the nickel content can be adjusted by adding SN100-3. The solder bars are melted into solder paste. Usually, the solder paste in the tin bath will be consumed during the normal processing of the PCB board. When the solder paste is insufficient, SN100-2 can be added continuously to supplement the solder paste.

[0022] S3: Immerse the PCB board into the tin furnace for 2 - 6 seconds, then use the hanging board of the spray tin machine to take out the PCB board. When taking out, the rising speed of the hanging board is about 600 - 1200 mm / s. Control the temperature of the front and rear air knives at 385°C - 420°C, the pressure of the front and rear air knives at 6.5 kg / cm² - 2.5 kg / cm², the total air pressure output at 6 - 9 kg, the angle of the front air knife between 3° - 5°, and the angle of the rear air knife between 4° - 7°. Blow hot air on the PCB board for 1 - 3 seconds.

[0023] S4: Take out the PCB board and inspect whether the spray tin thickness meets the requirements. If not, adjust the air pressure of the spray tin machine. The specific operation method is to reduce the air pressure of the air knife when the thickness of the tin is thinner, and increase the air pressure of the air knife when the thickness of the tin is thicker.

[0024] S5: Fix the processed PCB board that meets the requirements, and adjust the lens to identify the PCB board. The specific identification process is as follows: Manually move the optical point of the lens to ensure that there is only one image of the optical point inside the lens. Adjust the exposure of the lens to filter out the scattered light until a clear contour of the optical point can be obtained. Select 3 points on the edge of the contour, locate a circle from the 3 points, and select the center of the circle to obtain the coordinates of the optical point. After the identification process is completed, the moving path and the lens exposure can be saved. Subsequently, when facing similar optical point devices, the identification process will be automatically repeated for identification and positioning work.

[0025] During the specific PCB board processing, in order to ensure the utilization rate of the layout, the width of the process edge in S1 may be reduced. For example, Figure 2 as shown, when the width of the process edge is not enough to form a complete solder mask opening, it only needs to show the substrate in a relatively large area around the optical point A1. At this time, the ratio of the radius of the optical point A1 to the maximum radius of the solder mask opening is in the range of 1:3 to 1:6.

[0026] There may also be a situation where no copper is plated on the process edge. For example, Figure 3 as shown, at this time, a protection ring can be added around the optical point A. The protection ring is made of copper, the ring width w of the copper ring > 0.3 mm and is covered with ink to avoid the reduction of the finished diameter of the optical point caused by excessive etching of the optical point, resulting in the reduction of the positioning accuracy.

Claims

1. A method for manufacturing optical identification points of a PCB board, The following steps are involved: S1: adding a process edge to the long side of the PCB board, and setting an optical point structure on the process edge, the optical point structure including an optical point A (1), an optical point B (2), and a positioning hole (3), and the optical point has various forms; S2: mixing and melting different types of tin bars SN100-1, SN100-2, and SN100-3 in a tin tank at high temperature to form a solder alloy paste of copper, tin, and nickel in a suitable proportion; S3: immersing the PCB board in the tin furnace for a period of time, adjusting the relevant parameters of the tin spraying machine and the air knife to a suitable range, and performing hot air leveling on the PCB board; S4: Take out the PCB board and check whether the tin spraying thickness meets the requirements. If not, adjust the wind pressure of the tin spraying machine; S5: Fix the PCB board that has been processed and meets the requirements, and adjust the lens to identify the PCB board.

2. The method for manufacturing optical identification points of a PCB board according to claim 1, characterized in that: The optical point A (1) described in S1 is surrounded by a solder mask opening process, and copper with a diameter of 4 mm is etched away around the optical point A (1). The optical point B (2) can be a NPTH hole, and copper with a diameter of 1.6 mm is etched away around the optical point B (2) by the same solder mask opening process.

3. A method for manufacturing optical identification points of a PCB board according to claim 1 or 2, characterized in that: The shapes of the optical point A (1) and the optical point B (2) can be circular, square, diamond or any shape with less than or equal to four sides.

4. A method for manufacturing optical identification points of a PCB board according to claim 1 or 2, characterized in that: The optical point structure as a whole needs to be staggered and distributed at the four corners of the PCB board, the horizontal distance d1 between the center of the optical point A (1) and the center of the positioning hole (3) is ≥11 mm, and the horizontal distance d2 between the center of the optical point A (1) and the center of the optical point B (2) is ≥8 mm.

5. A method for manufacturing optical identification points of a PCB board according to claim 1 or 2, characterized in that: The center of the optical point A (1) and the center of the optical point B (2) are on the same horizontal line, the distance d3 between the center of the optical point A (1) and the edge of the board is greater than 2 mm, and the distance d4 between the center of the positioning hole (3) and the edge of the board needs to differ from the distance d3 of the edge of the board by more than 0.5 mm.

6. The method for manufacturing optical identification points of a PCB board according to claim 1, characterized in that: The tin bar S2 can be selected from SN100-1, SN100-2, and SN100-3. The copper content of SN100-1 is 0.5-0.7%, and the nickel content is 0.040-0.070%. The copper content of tin bar SN100-2 is 0-0.4%, and the nickel content is 0.040-0.070%. The copper content of tin bar SN100-3 is 0-0.4%, and the nickel content is 0.13-0.17%.

7. The method for manufacturing optical identification points of a PCB board according to claim 1, characterized in that: The temperature of the tin furnace described in S2 is between 260°C and 280°C, and the stirring temperature of the solder alloy paste is controlled between 260°C and 280°C.

8. The method for manufacturing optical identification points of a PCB board according to claim 1, characterized in that: The tinning time of the PCB board described in S3 is controlled at 2 to 6 seconds, and the rising speed of the PCB board lifted out of the solder alloy paste by the tin spraying machine hanging plate is about 600 to 1200 mm / s.

9. The method for manufacturing optical identification points of a PCB board according to claim 1, characterized in that: Each time S3 blows air to the PCB, the duration is 1 to 3 seconds. The air knife parameters that need to be adjusted include: the front and rear air knife temperatures are controlled at 385°C to 420°C, the front and rear air knife pressures are controlled at 6.5kg / cm² to 2.5kg / cm², the total air pressure output is controlled at 6 to 9kg, the front air knife angle is controlled between 3° and 5°, and the rear air knife angle is controlled between 4° and 7°.

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