Anti-skip printing mark detection method for PCB multi-layer printing process

Abstract

The invention relates to the technical field of PCB (Printed Circuit Board) processing, in particular to an anti-skip printing mark detection method for a PCB multilayer printing process, which comprises the following steps of: planning a mark area on a PCB; when a first line layer printing process is carried out on the PCB, a first mark is printed in the mark area at the same time; when a second insulating layer printing procedure is carried out on the PCB, a second mark is printed in the mark area at the same time, and the second mark partially covers the first mark in the vertical projection direction; the mark state of the mark area is judged, if the first mark and the second mark are overlapped, it is judged that no through printing exists, and if the first mark and the second mark are not overlapped, it is judged that through printing exists. And an effect of visual detection is achieved.

Description

Technical Field

[0001] This invention relates to the field of PCB processing technology, and in particular to a method for detecting missing markings in PCB multilayer printing processes. Background Technology

[0002] Printed circuit boards (PCBs) are indispensable basic components in modern electronic devices. The manufacturing process of PCBs often involves multi-layer printing processes. For example, circuit layers are printed first, followed by insulating layers. Ensuring that both circuit and insulating layers are printed correctly is crucial for product quality. Missing a step in any process can affect the electrical or physical protection performance of the PCB. Therefore, this invention aims to provide a marking detection method for PCB multi-layer printing processes to address potential missing printing issues in existing PCB multi-layer printing technologies. Summary of the Invention

[0003] To address the problems in the prior art, this application provides a method for detecting missing markings in PCB multilayer printing processes.

[0004] The present invention provides a method for detecting missing markings in PCB multilayer printing processes, which adopts the following technical solution: A method for detecting missing markings in PCB multilayer printing processes includes the following steps: S1: Design the marking area on the PCB board; S2: During the first circuit layer printing process on the PCB board, a first mark is printed simultaneously in the marking area; S3: During the second insulating layer printing process on the PCB board, a second mark is simultaneously printed in the marking area, and the second mark partially covers the first mark in the vertical projection direction; S4: Determine the marking status of the marking area. If the first mark and the second mark overlap, determine that there is no missing print. If the first mark or the second mark does not overlap, determine that there is a missing print.

[0005] Preferably, the first mark and the second mark are two mirror-image triangular symbols.

[0006] Preferably, the first mark and the circuit layer are printed using the same material, and the second mark and the insulating layer are printed using the same material.

[0007] Preferably, the marked area is located in the non-functional edge area of ​​the PCB board.

[0008] Preferably, the first mark is two groups of electrodes, the second mark is a solid covering block, and the second mark covers the same ends of the two groups of electrodes of the first mark in the vertical projection direction.

[0009] Preferably, two test leads are respectively led out from the two groups of electrodes of the first mark, and the two test leads extend to the edge of the mark area.

[0010] Preferably, S4 includes: S41: After printing and curing, perform the panel cutting process. In the panel cutting process, while cutting the process edge area of the PCB board, also cut the mark area to obtain mark blocks. Then, number the separated mark blocks and collect them into an off-line detection tray; S42: In off-line detection, put the mark blocks into a test fixture and measure the capacitance value between the two groups of electrodes; S43: If the measured capacitance value is C1 based on the insulation dielectric constant, it is determined that there is no missing printing. If the measured capacitance value is C2 that is not based on the insulation dielectric constant and C2 < C1, it is determined that there is missing printing, and trace the corresponding batch of PCB boards according to the number of the mark block; S44: After the detection is completed, centrally scrap the detected mark blocks.

[0011] Preferably, in S43, further analyze whether C2 is the capacitance value based on the air dielectric constant. If so, it is determined that the insulation layer is missing printed. If not, it is determined that the circuit layer is missing printed.

[0012] Preferably, in S42 and S43, group and connect in parallel multiple mark blocks of the same batch into the same detection circuit. If the capacitance value of a certain group is abnormal, then detect each of the multiple mark blocks in this group one by one.

[0013] Preferably, in S42 and S43, first perform multiple groups of test measurements, and determine C1 according to the statistical mean of the test measurement groups. C1 is the mean ± ε, where ε is the error amount.

[0014] The beneficial effects of the present invention are as follows: Without occupying the functional blocks of the PCB board and without additionally using printing materials other than the circuit layer and the insulation layer, it is possible to observe whether there is an overlapping area between the first mark and the second mark by means of manual visual inspection or an image detection device, so as to quickly determine whether there is a missing printing situation on the PCB board, having an intuitive detection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the principle of the mark detection method in Embodiment 1; Figure 2 is a schematic diagram of the principle of the mark detection method in Embodiment 2; Figure 3 This is a schematic diagram illustrating the principle of the marker detection method in the other embodiments.

[0016] Explanation of reference numerals in the attached diagram: 1. Circuit layer; 2. Insulation layer; 3. First mark; 31. Test lead; 4. Second mark; 5. Marking area; 6. Marking block. Detailed Implementation

[0017] The following will combine Figures 1-3 The present invention will be further illustrated by the embodiments.

[0018] Example 1 This embodiment discloses a method for detecting missing markings in PCB multilayer printing processes.

[0019] Reference Figure 1 The method for detecting missing markings in PCB multilayer printing processes includes the following steps: S1: Mark area 5 on the non-functional board edge area of ​​the PCB, such as the process edge area or other non-functional areas; S2: When the first circuit layer 1 is printed on the PCB board using circuit material, the first mark 3 is printed in the marking area 5 at the same time. The first mark 3 uses the same circuit material as the circuit layer 1. S3: When the second insulating layer 2 is printed on the PCB board using insulating material, a second mark 4 is printed in the marking area 5 at the same time. The second mark 4 uses the same insulating material as the insulating layer 2, and the second mark 4 partially covers the first mark 3 in the vertical projection direction. S4: Determine the marking status of the marking area 5. If the first mark 3 and the second mark 4 overlap, it is determined that there is no missing print. If the first mark 3 or the second mark 4 do not overlap, it is determined that there is a missing print.

[0020] Based on the above steps, without occupying the functional blocks of the PCB board or using additional printing materials other than the circuit layer 1 and the insulating layer 2, the first mark 3 and the second mark 4 can be observed by manual visual inspection or image inspection equipment to determine whether there is an overlapping area, thereby quickly determining whether there is a missing print on the PCB board, which has the effect of intuitive detection.

[0021] Furthermore, in this embodiment, the first mark 3 and the second mark 4 are two mirror-image triangular symbols. In this case, the logic of visual inspection or image detection is to observe whether the vertices of the two triangular symbols coincide. Compared with other shapes, the vertices of the triangular symbols are unambiguous positioning points in a single direction, thereby making the judgment of visual inspection or image detection devices more sensitive.

[0022] Example 2 This embodiment also discloses a method for detecting missing printing marks in PCB multilayer printing process. Compared with the first embodiment, this embodiment uses circuit detection to determine whether there is an overlapping area between the first mark 3 and the second mark 4. Since it no longer relies on manual visual inspection or image detection, the first mark 3 and the second mark 4 include, but are not limited to, the use of triangular symbols.

[0023] Reference Figure 2 The method for detecting missing markings in PCB multilayer printing processes includes the following steps: S1: Mark area 5 on the non-functional board edge area of ​​the PCB, such as the process edge area or other non-functional areas; S2: When the first circuit layer 1 is printed on the PCB board using circuit material, the first mark 3 is printed on the marking area 5 at the same time. The first mark 3 uses the same circuit material as the circuit layer 1. The first mark 3 consists of two sets of electrodes. In this embodiment, the gap between the heads of the two sets of electrodes is preferably 0.2-0.3mm. Test leads 31 are led out from the roots of the two sets of electrodes of the first mark 3, and the two test leads 31 extend to the edge of the marking area 5. S3: When the second insulating layer 2 is printed on the PCB board using insulating material, the second mark 4 is printed in the marking area 5 at the same time. The second mark 4 uses the same insulating material as the insulating layer 2. The second mark 4 is a solid covering block. The second mark 4 covers the heads of the two sets of electrodes of the first mark 3 in the vertical projection direction. S4: Determine the marking status of marking area 5. If the first mark 3 and the second mark 4 overlap, determine that there is no missing mark. If the first mark 3 or the second mark 4 does not overlap, determine that there is a missing mark. Specifically, S4 includes: S41: After the printing has cured, the board separation process is carried out. During the board separation process, the process edge area of ​​the PCB board is cut off and the marking area 5 is also cut off to obtain the marking block 6. Then, the separated marking block 6 is numbered and collected into the offline inspection tray. Through this step, the markings on the PCB board can be removed while removing the process edge of the PCB board. The marking effect can be achieved without additional printing removal process, thus avoiding the presence of additional markings on the PCB board. S42: In offline inspection, the marker block 6 is placed in the test fixture, and the capacitance value between the two sets of electrodes is tested. Through offline inspection, the anti-missing print inspection step is removed from the PCB board processing production line, reducing the impact on the production line cycle and greatly improving production efficiency. It should be noted that since the probability of missing print is low, even if the inspection action is later than the subsequent processing work, and the corresponding PCB board is traced and processed after the missing print is detected, the cost is relatively controllable, because the benefits brought by the efficiency improvement far outweigh the cost of scrap. S43: If the measured capacitance value is C1 (C1 is a range value) based on the insulation dielectric constant of the insulating material, it is determined that there is no missing printing. If the measured capacitance value is C2 which is not based on the insulation dielectric constant of the insulating material and C2 < C1, it is determined that there is missing printing, and the corresponding batch of PCB boards is traced according to the number of the marking block 6; S44: After the detection is completed, the detected marking blocks 6 are centrally scrapped.

[0024] The above steps do not need to introduce foreign substances outside the circuit layer 1 and the insulating layer 2, and completely use the original materials of the PCB board. Based on the conductivity brought by the same material of the first marking 3 and the circuit layer 1 and the insulation performance brought by the same material of the second marking 4 and the insulating layer 2, a marking detection method for the electrical detection overlapping area is provided. Compared with manual visual inspection and image detection equipment, the capacitance detection method has the advantages of anti-pollution, anti-interference and low cost. In addition, in the above detection steps, the production line beat can be accelerated by performing the detection actions offline, and it can also ensure that there is no redundant marking residue on the PCB boards leaving the factory. Finally, while achieving the anti-missing printing detection effect, the production efficiency and the quality of the PCB boards leaving the factory are also improved.

[0025] In S43, it can further analyze whether C2 is the capacitance value based on the air dielectric constant. If so, it is determined that the insulating layer 2 is missing printing. If not, it is determined that the circuit layer 1 is missing printing. At this time, the detection circuit is open and the capacitance value is close to 0. In addition, in S43, by judging whether the capacitance value is too large, it can also be judged whether there is repeated printing of the insulating layer 2.

[0026] In S42 and S43, multiple marking blocks 6 of the same batch are grouped and connected in parallel into the same detection circuit. If the capacitance value of a certain group is abnormal, then the multiple marking blocks 6 of this group are detected one by one. On the one hand, the capacitance value can be amplified through group detection, thereby reducing the use of high-precision instruments and lowering the detection consumable cost. On the other hand, the detection efficiency can be greatly improved through group detection, ensuring that the missing printing problem can be discovered in time.

[0027] In S42 and S43, multiple group tests are first carried out, for example, at least 5 group tests, and C1 is determined according to the statistical mean of the test groups. C1 is the mean ± ε, where ε is the error amount, so that C1 is a range value. Based on this step, the judgment threshold is made more in line with the current batch, improving the judgment accuracy.

[0028] Furthermore, when planning the marking area 5 in S1, the subsequent cutting shape is planned in advance, and finally when cutting the marking block 6 in S41, one corner of the marking block 6 is cut into a chamfer shape, forming an asymmetric marking block 6, which is convenient for correctly loading into the test fixture during testing.

[0029] In addition, refer to Figure 3In other embodiments, the two sets of electrodes of the first mark 3 can also be designed in a shape similar to interdigitated electrodes, thereby significantly increasing the capacitance value and further reducing the difficulty of testing.

[0030] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for detecting missing printing marks in PCB multilayer printing processes, characterized in that, It includes the following steps: S1: Plan a marking area (5) on the PCB board; S2: When performing the first printing process of the circuit layer (1) on the PCB board, simultaneously print a first mark (3) in the marking area (5); S3: When performing the second printing process of the insulating layer (2) on the PCB board, simultaneously print a second mark (4) in the marking area (5), and the second mark (4) partially covers the first mark (3) in the vertical projection direction; S4: Determine the marking status of the marking area (5). If the first mark (3) and the second mark (4) overlap, it is determined that there is no missing printing. If the first mark (3) or the second mark (4) does not overlap, it is determined that there is missing printing.

2. The method for detecting missing markings in PCB multilayer printing process according to claim 1, characterized in that: The first mark (3) and the second mark (4) are two triangular symbols that are mirror images of each other.

3. The method for detecting missing markings in PCB multilayer printing process according to claim 1, characterized in that: The first mark (3) is printed with the same material as the circuit layer (1), and the second mark (4) is printed with the same material as the insulating layer (2).

4. The method for detecting missing markings in PCB multilayer printing process according to claim 1, characterized in that: The marking area (5) is located in the non-functional board edge area of the PCB board.

5. The method for detecting missing markings in PCB multilayer printing process according to claim 3, characterized in that: The first mark (3) is two groups of electrodes, and the second mark (4) is a solid covering block. The second mark (4) covers the same ends of the two groups of electrodes of the first mark (3) in the vertical projection direction.

6. The method for detecting missing printing marks in PCB multilayer printing process according to claim 5, characterized in that; Two test leads (31) are respectively led out from the two groups of electrodes of the first mark (3), and the two test leads (31) extend to the edge of the marking area (5).

7. The method for detecting missing printing marks in PCB multilayer printing process according to claim 6, characterized in that, S4 It includes: S41: After printing and curing, perform a board separation process. In the board separation process, while cutting the process edge area of the PCB board, also cut the marking area (5) to obtain a marking block (6). Then, number the separated marking block (6) and collect it into an offline detection tray; S42: In offline detection, place the marking block (6) into a test fixture and test the capacitance value between the two groups of electrodes; S43: If the measured capacitance value is C1 based on the insulation dielectric constant, it is determined that there is no missing printing. If the measured capacitance value is C2 that is not based on the insulation dielectric constant, and C2 < C1, it is determined that there is missing printing, and trace the corresponding batch of PCB boards according to the number of the marking block (6); S44: After the detection is completed, centrally scrap the detected marking blocks (6).

8. The method for detecting missing markings in PCB multilayer printing process according to claim 7, characterized in that: In S43, further analyze whether C2 is a capacitance value based on the air dielectric constant. If so, it is determined that the insulating layer (2) is missing printing. If not, it is determined that the circuit layer (1) is missing printing.

9. The method for detecting missing markings in PCB multilayer printing process according to claim 8, characterized in that: In S42 and S43, group and connect in parallel multiple marking blocks (6) of the same batch into the same detection circuit. If the capacitance value of a certain group is abnormal, then perform individual detection on the multiple marking blocks (6) of that group.

10. A method for detecting missing markings in PCB multilayer printing process according to claim 9, characterized in that: In S42 and S43, first perform multiple groups of trial measurements, and determine C1 based on the statistical mean of the trial measurement groups. C1 is the mean ± ε, where ε is the error amount.

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