Method for saving soft gold salt in PCB / SUB machining process

Abstract

The invention relates to the technical field of circuit board processing, in particular to a method for saving soft gold salt in a PCB / SUB processing process, which comprises the following steps of: after an AOI (Automatic Optic Inspection) detection of a SUB jointed board is finished, cutting off electroplating lead connection between the unqualified Units and qualified Units in the SUB jointed board; and then, only qualified Units are subjected to soft gold electroplating treatment, and unqualified Units do not participate in the subsequent electroplating process. Selective electrical isolation is implemented before soft gold electroplating, so that the scrapped Units are completely separated from an electroplating loop and are prevented from participating in current distribution in the electroplating process, invalid deposition of gold salt on the scrapped Units is prevented, electroplating resources are intensively used for qualified Units, and the overall electroplating efficiency and consistency are improved. On the premise of not adding an extra complex electroplating process, the material cost is obviously saved, and good economic benefits are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit board processing, and particularly relates to a method for saving soft gold salt in PCB / SUB processing. BACKGROUND

[0002] In the manufacturing process of printed circuit boards (PCB) and substrates (SUB), the surface treatment process has an important influence on the welding performance, electrical connection reliability and corrosion resistance. Among them, the electroplated nickel-gold process is a widely used surface treatment method, which is commonly referred to as a soft gold process in the industry. In the soft gold plating process, a nickel layer is first formed on the surface of the circuit as a barrier layer and a bonding layer, and then a gold layer is deposited on the surface of the nickel layer through electrolysis. The basic reaction principle is that under the action of an external power source, the circuit to be plated is connected to the cathode, and the gold ions (Au + ) in the solution are reduced to deposit a gold layer on the surface of the circuit after obtaining electrons. Because the standard electrode potential of gold is high, and the price of metal gold is expensive, gold is not used as a soluble anode in actual production, but an insoluble anode of titanium plated with platinum is selected, and gold salt is continuously supplemented into the electroplating solution as the source of gold ions. Gold salt is a chemical product made of high-purity gold, containing precious metal gold, and its cost is extremely high. In the cost structure of PCB / SUB manufacturing, the cost of a single process of electroplated nickel-gold usually accounts for about 30% of the selling price of the finished product, which has become one of the important factors restricting the cost control of products. Therefore, how to effectively reduce the consumption of gold salt and improve the utilization rate of gold salt while ensuring the quality and reliability of gold plating has always been the focus and continuous optimization direction of processing enterprises in the industry.

[0003] In view of the above problems, various improvement means have been proposed in the prior art, for example: (1) appropriately reducing the concentration of gold ions in the electroplating solution; (2) optimizing the electroplating process parameters to improve the uniformity of the thickness distribution of the gold layer; (3) setting a gold-containing wastewater recovery and precious metal recovery device at the end of the production line. However, these means mainly focus on electroplating solution management and end-of-line recovery, and there is still a problem of invalid consumption of gold salt for product units that have completed gold plating but are determined to be scrap in subsequent detection.

[0004] In the existing PCB / SUB processing process, an automatic optical inspection (AOI) procedure is usually arranged after electroplating is completed, for appearance and circuit defect detection of the SUB panel processed. For the Unit determined as unqualified by detection, the prior art generally only executes recording the position code of the Unit in the SUB panel and outputs the corresponding scrap reason, and then enters the overall scrap or rework process. Since the scrapped Unit is still in electrical connection state with the qualified Unit in the same SUB panel through the electroplating lead, in the subsequent process or repair process, it may still continuously participate in electroplating or cause further invalid consumption of gold salt, thereby reducing the actual utilization efficiency of gold salt. SUMMARY

[0005] In view of the technical problems of high consumption of gold salt and low actual utilization efficiency in the existing soft gold process, the present application provides a method for saving soft gold salt in the PCB / SUB processing process, which shields or removes the electrical connection path of the scrapped Unit, effectively avoids the deposition and consumption of gold salt in the invalid area, thereby improving the utilization efficiency of gold salt and reducing the production cost. The specific technical scheme is as follows: A method for saving soft gold salt in the PCB / SUB processing process, comprising: after completing the AOI detection, cutting off the electroplating lead connection between the Unit determined as unqualified and the qualified Unit in the SUB panel; then only electroplating the qualified Unit with soft gold, and the unqualified Unit does not participate in the subsequent electroplating process. By implementing selective electrical isolation before soft gold electroplating, the scrapped Unit is completely separated from the electroplating circuit, avoiding its participation in current distribution during electroplating, thereby preventing invalid deposition of gold salt on the scrapped Unit, ensuring that electroplating resources are concentrated on the qualified Unit, and improving the overall electroplating efficiency and consistency.

[0006] Further, the AOI detection method is: the AOI machine analyzes and compares the defect area with CAM, finds the inconsistent with the drawing, and determines the scrap position; the AOI machine outputs the coordinates and defect name of the scrapped Unit, and takes a photo of the defect position for file as the basis for manual determination. Through automatic comparison of AOI and CAM data, accurate positioning and determination of the scrapped Unit are realized, manual experience dependence is reduced, the accuracy and traceability of unqualified Unit identification are improved, and a reliable data basis is provided for the subsequent automatic cutting-off procedure.

[0007] Further, the cutting method is as follows: the SUB panel is placed on the laser panel burning machine, the scrap coordinates output by the AOI machine are read, and the scrap unit is found. The laser panel burning machine is used to burn the scrap position unit to break the gold-plated lead. The laser cutting method realizes non-contact precise cutting, avoids the stress damage and position deviation caused by traditional mechanical methods, and can quickly and accurately isolate the scrap unit electrical connection path without affecting the surrounding circuit.

[0008] Further, the typical defects determined by AOI detection as unqualified include: pad missing or shape abnormality, fine line breakage or short circuit, and pad offset exceeding the design tolerance ±15μm. By defining the typical defect determination standard, the identification of scrap units has uniformity and quantifiable basis, avoiding misjudgment or omission due to ambiguous determination standard, so as to ensure that only the units that cannot be repaired or cannot meet the reliability requirements are isolated.

[0009] Further, the laser panel burning machine uses ultraviolet laser with wavelength of 330-380nm, single point action time of 20-40μs, and broken line width not greater than 50μm. The ultraviolet laser short pulse burning method can complete the line cutting in a very small heat affected zone, effectively avoiding damage to adjacent fine lines and pads caused by heat diffusion, and ensuring the structural integrity and electrical reliability of high-density fine line SUB panels.

[0010] Further, a data communication interface is established between the AOI machine and the laser panel burning machine, and the laser panel burning machine can automatically receive the coordinate information of the scrap unit and generate the corresponding laser burning path. Through the data connection and automatic control between devices, the error caused by manual positioning and manual operation is avoided, the consistency and repeatability of the cutting operation are improved, and it is suitable for large-scale, high-speed industrial production scenes.

[0011] Further, the cutting position is set at the common electroplated lead or branch lead of the SUB panel, and a cooling interval time of 0.8-1.2s is set between adjacent burning points, so as to ensure that the internal circuit structure and functional integrity of the qualified unit are not affected, and facilitate subsequent panel separation or scrap processing.

[0012] Further, after cutting the electroplated lead, the electrical continuity of the burned area is detected, and the resistance value ≥10MΩ is considered as complete electrical isolation, confirming that the scrap unit and the qualified unit in the SUB panel are completely electrically isolated, avoiding the gold salt loss caused by micro-current conduction in the subsequent soft gold electroplating process.

[0013] Further, the SUB panel after soft gold plating is subjected to secondary AOI or visual inspection review, focusing on whether the cutting area and adjacent circuit exist ablation, splashing or residual conductive material, and timely find and exclude the side effects of laser cutting to ensure the plating quality and product reliability.

[0014] Further, it also includes data statistics and traceability analysis of the number of scrapped units, corresponding saved soft gold salt dosage and processing batch information, which is used to evaluate the gold saving effect and optimize the AOI determination threshold and burnout strategy. Through the statistics and analysis of the gold saving data, the gold saving effect under different products and different defect types can be quantitatively evaluated, which provides data support for process parameter optimization and management decision, and promotes the continuous optimization and standardized implementation of the gold saving scheme.

[0015] The beneficial effects of the present application are: The method for saving soft gold salt in the PCB / SUB processing provided by the present application can effectively avoid the deposition of gold salt in the invalid area by precisely electrically isolating the scrapped unit before soft gold plating, thereby significantly improving the utilization efficiency of soft gold salt. Without adding additional complex plating process, the present application combines AOI automatic determination and laser burnout process to realize the automation, refinement and high consistency of the gold saving measures, which is suitable for the production of high-density and high-value PCB / SUB products, realizes obvious material cost saving, and has good economic benefits. At the same time, the cutting position is reasonable and the thermal influence is controllable, which does not affect the structure and electrical performance of the qualified unit, thereby ensuring the product quality and reliability. In addition, through the data statistics and traceability analysis mechanism, the quantifiable evaluation and continuous optimization of the gold saving effect are realized, which has good industrial promotion value. DETAILED DESCRIPTION

[0016] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with preferred embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0017] Embodiment 1 The size of the SUB panel used in this embodiment is 510mmx415mm, and the single SUB panel contains 20 units. Each unit is connected to the peripheral gold plating bus of the SUB panel through a common gold plating lead, the target thickness of soft gold plating is 0.05-0.10μm, and the plating process adopts direct current soft gold plating.

[0018] The embodiment provides a method for saving soft gold salt in a PCB / SUB processing process, which comprises the following steps: (1) After completing the line, solder mask and pretreatment processes, the SUB panel enters an AOI detection process; an AOI machine adopts an industrial camera with a resolution of not less than 5 μm to scan the line pattern, pad opening and key plating area of each unit one by one, and compare and analyze the CAM design data. If the pad is missing or the shape is abnormal, the fine line is broken or short-circuited, the pad offset exceeds the design tolerance ± 15 μm, or other defect positions inconsistent with the design drawing are detected, the corresponding unit is determined as an unqualified unit. At the same time, the AOI machine outputs the specific coordinates (X, Y values) of the unqualified unit in the SUB panel coordinate system, labels the defect type, and automatically saves the defect area image for manual review.

[0019] (2) After completing the AOI detection, the SUB panel is sent to a laser burning panel process. The laser burning panel machine implements a burning-off process at the connection between the corresponding unqualified unit and the common gold-plated lead according to the coordinate information output by the AOI. The burning-off process adopts ultraviolet laser with a wavelength of 355 nm, and the single-point action time is 30 μs. The burning-off line width is not greater than 50 μm. After the burning-off is completed, the lead is completely disconnected through visual inspection, so that the unqualified unit no longer participates in the subsequent plating circuit in an electrical manner. Then, the processed SUB panel is sent to a soft gold plating process, and only the qualified unit participates in the plating.

[0020] Through detection, the unqualified rate of the units in the SUB panel is about 15% on average. According to statistics, compared with the soft gold plating process of the SUB panel without implementing the above method, the consumption of soft gold salt in the embodiment is reduced by about 13%, and the gold salt waste of the scrapped area is effectively reduced under the premise of ensuring the consistency of the product plating thickness.

[0021] Embodiment 2 The embodiment provides a method for saving soft gold salt in a PCB / SUB processing process, which comprises the following steps: (1) After completing the line, solder mask and pretreatment processes, the SUB panel enters an AOI detection process; an AOI machine adopts an industrial camera with a resolution of not less than 5 μm to scan the line pattern, pad opening and key plating area of each unit one by one, and compare and analyze the CAM design data. If the pad is missing or the shape is abnormal, the fine line is broken or short-circuited, the pad offset exceeds the design tolerance ± 15 μm, or other defect positions inconsistent with the design drawing are detected, the corresponding unit is determined as an unqualified unit. AOI machine, laser burning panel machine and MES system establish a data communication interface. After the AOI detection is completed, the coordinates of the unqualified unit, the defect type and the SUB panel number are automatically uploaded to the MES system and simultaneously sent to the laser burning panel machine control module.

[0022] (2) After AOI inspection, the SUB panel is sent to the laser burn-in process. The control module of the laser burn-in machine automatically parses the coordinate data and generates the corresponding burn-in path to avoid positioning errors caused by manual input. Burn-in treatment is performed at the connection between the corresponding non-conforming Unit and the common gold-plated lead. The burn-in treatment uses a 340nm wavelength ultraviolet laser with a single-point action time of 20μs and a burn-in line width of no more than 50μm.

[0023] In this embodiment, after the burn-out is completed, the SUB panel enters the online electrical continuity testing process, where the resistance value between each unqualified unit and the common bus is tested. A resistance value ≥10MΩ is considered as complete electrical isolation; units that do not meet the standard will trigger a secondary burn-out process. Subsequently, the processed SUB panel is sent to the soft gold electroplating process, where only qualified units participate in the electroplating.

[0024] In this embodiment, the laser ablation path adopts the shortest common lead priority strategy, that is, the laser is preferentially cut at the branch lead close to the SUB panel busbar to reduce the thermal impact of the laser on the local circuit.

[0025] This embodiment introduces AOI-laser burn-in online control and electrical continuity detection, significantly improving process stability and automation. Statistical analysis of 100 SUB panels in a batch of continuous production showed that each SUB panel had an average of 2.4 scrapped units, an average saving of approximately 25% in soft gold salt, and a uniformity of plating thickness of 3σ ≤ ±0.01μm for qualified units. The results indicate that this embodiment improves gold-saving performance without affecting the plating quality of qualified products, making it suitable for large-scale mass production.

[0026] Example 3 This embodiment provides a method for saving soft gold salts during PCB / SUB processing, including: (1) After completing the circuit, solder mask and pretreatment processes, the SUB panel enters the AOI inspection process. The AOI machine uses an industrial camera with a resolution of not less than 5μm to scan the circuit pattern, pad openings and key electroplating areas of each unit one by one, and compares and analyzes them with the CAM design data. If any defects are detected that are inconsistent with the design drawings, such as missing or abnormally shaped pads, broken or short-circuited thin lines, or pad offset exceeding the design tolerance ±15μm, the corresponding unit is determined to be a non-conforming unit. When the AOI inspection determines that there are multiple non-conforming units in the same SUB panel, the AOI machine summarizes and outputs the coordinate information of all non-conforming units, and the laser burn-off machine burns off the gold-plated leads corresponding to each non-conforming unit in the order of coordinates. In order to prevent local substrate damage caused by multiple laser actions, the laser burning-off sequence adopts the path planning method from the outside to the inside, and the cutting is carried out at the position of the common electroplated leads or branch leads of the SUB panel, and a cooling interval of 0.8~1.2s is set between adjacent burning-off points.

[0027] (2) After AOI inspection, the SUB panel is sent to the laser burn-out process. The laser burn-out machine, based on the coordinate information output by AOI, burns off the connection between the corresponding non-conforming unit and the common gold-plating lead. The burn-out process uses a 380nm ultraviolet laser with a single-point action time of 40μs, and the burned-out line width is no greater than 50μm. After burn-out, visual inspection confirms that the lead is completely disconnected, ensuring that the non-conforming unit no longer participates in the subsequent electroplating circuit. Subsequently, the processed SUB panel is sent to the soft gold electroplating process, where only the qualified units participate in the electroplating.

[0028] In this embodiment, after the burn-out is completed, the SUB panel undergoes a second AOI inspection, focusing on checking for any residual conductive material in the burn-out area, whether adjacent qualified lines show signs of ablation or misalignment, and the integrity of the gold-plated lead breaks. Once no abnormalities are confirmed, the SUB panel enters the soft gold plating process, with only the remaining qualified units participating in the plating reaction.

[0029] In this embodiment, after electroplating is completed, the number of scrapped units, the amount of soft gold salt saved, and the corresponding production batch of the batch of SUB panels are statistically recorded. The statistical results are used to analyze the impact of different defect types on gold salt loss, thereby providing data support for subsequent optimization of AOI judgment rules and SUB panel design.

[0030] Production data statistics show that, using the method of this embodiment, the soft gold plating area of ​​a single SUB panel can be reduced by up to approximately 35%, and the overall gold salt consumption can be reduced by more than 30%. The overall scrap rate of the SUB panel did not increase due to the lead cutting process. Furthermore, through correlation analysis between defect types and gold-saving effects, it was found that pad defects contribute the most to gold salt waste, providing data support for optimizing pad processes in subsequent front-end manufacturing processes.

[0031] With the process refinement and data support of the above embodiments 1 to 3, the method provided by the present invention can be stably implemented under different levels of automation and different scrap rates, significantly reducing the consumption of soft gold salts, taking into account both electroplating quality and production efficiency, and has good engineering feasibility and industrial promotion value.

[0032] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for saving soft gold salts during PCB / SUB processing, characterized in that, include: After the SUB panel completes AOI inspection, the electroplating lead connection between the unqualified unit and the qualified unit in the SUB panel is cut off. Subsequently, only qualified units undergo soft gold plating, while unqualified units are excluded from subsequent plating processes.

2. The method as described in claim 1, characterized in that, The AOI inspection method is as follows: The AOI machine analyzes the defect area and compares it with the CAM data. If any discrepancies are found with the drawings, the area is determined to be scrapped. The AOI machine outputs the coordinates and defect name of the scrapped unit and takes a photo of the defect location for record-keeping as a basis for manual judgment.

3. The method as described in claim 1, characterized in that, The cutting method is as follows: Place the SUB panel on the laser burnout machine, read the scrap coordinates output by the AOI machine, find the scrapped Unit, and use the laser burnout machine to burn off the gold-plated leads of the Unit at the scrapped location.

4. The method as described in claim 1 or 2, characterized in that, Typical defects that are deemed unacceptable by AOI inspection include: missing or abnormally shaped pads, broken or short-circuited fine lines, and pad offset exceeding the design tolerance of ±15μm.

5. The method as described in claim 1, characterized in that, The laser burn-off machine uses an ultraviolet laser with a wavelength of 330~380nm, a single-point action time of 20~40μs, and a burn-off line width of no more than 50μm.

6. The method as described in claim 1, characterized in that, An AOI machine and a laser burning-out machine establish a data communication interface. The laser burning-out machine can automatically receive the coordinate information of the scrapped unit and generate the corresponding laser burning-out path.

7. The method as described in claim 1, characterized in that, The cutting point is set at the common electroplating lead or branch lead of the SUB panel, and a cooling interval of 0.8~1.2s is set between adjacent burn-off points.

8. The method as described in claim 1, characterized in that, After cutting off the electroplating leads, electrical continuity testing is performed on the burned-out area. A resistance value ≥10MΩ is considered complete electrical isolation.

9. The method as described in claim 1, characterized in that, A second AOI or visual inspection is performed on the SUB panels that have completed soft gold plating, with a focus on checking whether there is ablation, splashing or residual conductive matter in the cut area and adjacent lines.

10. The method as described in claim 1, characterized in that, Also includes: The number of scrapped units, the corresponding amount of soft gold salt saved, and the batch information of the processed units are statistically analyzed and traced back to evaluate the gold-saving effect and optimize the AOI judgment threshold and burn-off strategy.