Method for preparing fine-pitch single-sided thick copper circuit board based on screen printing process
By optimizing screen printing process parameters and pre-compensation design, the problem of stable production of fine-pitch lines on thick copper single-sided boards was solved, realizing low-cost fine line manufacturing, reducing manufacturing costs and enhancing product competitiveness.
Patent Information
- Application Number
- CN202512008189.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-02-13
AI Technical Summary
Existing technologies make it difficult to stably and mass-produce fine-pitch lines of 0.15mm and below on thick copper single-sided boards, which leads to the need to rely on more expensive pattern exposure processes, increasing production costs.
By employing optimized screen printing process parameters and pre-compensation design, combined with etching process control, fine-pitch lines can be achieved on thick copper single-sided boards through screen printing, including line pattern pre-compensation, screen printing, UV curing, etching, and film removal steps.
It successfully reduced manufacturing costs by 10%-15%, achieved fine-pitch line production with a line width/spacing of 0.15mm, met the needs of high-density electronic products, improved product competitiveness and yield, and is suitable for copper-clad substrates of CEM-1 and FR-4 materials.
Smart Images
Figure CN121531587A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of printed wiring board manufacturing, in particular to a method for preparing a fine-pitch single-sided thick copper wiring board based on a screen printing process. BACKGROUND
[0002] In the manufacturing process of a conventional single-sided printed wiring board, the formation of a wiring pattern mainly relies on two processes, namely, screen printing (screen printing) of an etching-resistant ink or exposure of a photoresist (wet film / dry film) pattern. In the screen printing process, the board material is pretreated, the wiring pattern is transferred, and the etching is performed to form the pattern, and then the film is removed. When the film is removed after etching, the etching-resistant material (liquid photoresist ink, dry film photosensitive resin, etc.) covering the surface of the formed copper wiring is removed by chemical dissolution or physical peeling, so that the surface of the copper wiring is clean and exposed, thereby preparing for subsequent processes such as solder mask printing, surface treatment (soldering or gold plating), etc. For conventional products with a line width / line pitch greater than 0.18 mm, the screen printing process is widely used due to its low cost and high efficiency. The traditional exposure process route includes substrate preparation, dry film / wet film lamination, exposure, development, etching, and film removal.
[0003] However, when the design requirement is upgraded to a fine pitch with a line width / line pitch ≤ 0.15 mm, it is difficult to achieve such high precision due to the penetration, diffusion characteristics of the screen printing ink on the screen, and the fluidity limitation in the printing process. Therefore, the industry generally believes that it is necessary to switch to a higher-cost pattern exposure process (including film lamination, exposure, development, etc.) to achieve a line width / line pitch of 0.15 mm or less, which increases the production cost by about 10%-15% compared to the screen printing process.
[0004] With the continuous development of electronic products towards miniaturization and high density, more precise circuits need to be carried on single-sided boards. If fine-pitch screen printing process can be realized on thick copper (such as 2 oz) single-sided boards at low cost, it will significantly improve product competitiveness and effectively reduce manufacturing costs. Currently, there is no public technology that can stably and in batches realize a line width / line pitch of 0.15 mm / 0.15 mm on a 2 oz thick copper board through standard screen printing process. SUMMARY
[0005] Based on the above, the purpose of the present application is to provide a method for preparing a fine-pitch single-sided thick copper wiring board based on a screen printing process, to solve the problem in the prior art that it is difficult to stably and in batches realize a fine-pitch line of 0.15 mm or less on a thick copper single-sided board using a screen printing process, resulting in the need to rely on a higher-cost pattern exposure process, thereby increasing production costs.
[0006] To solve the above technical problems, the present application adopts the following technical solutions:
[0007] The application provides a method for preparing a fine-pitch single-sided thick copper circuit board based on a silk-screen process, which comprises the following steps.
[0008] A single-sided copper-clad plate is selected, the copper thickness of the single-sided copper-clad plate is 2 ounces, and the single-sided copper-clad plate is cut into a production plate according to original circuit design data corresponding to a preset cutting drawing.
[0009] With the conveying direction of the plate for subsequent processing as a reference, a line in the original circuit perpendicular to the conveying direction is defined as a horizontal line, and a line parallel to the conveying direction is defined as a vertical line.
[0010] For the fine-pitch requirement of a target line width / line pitch ≤ 0.15 mm, size pre-compensation is performed on the original circuit pattern, wherein the compensation amount of the horizontal line is 0.025 mm, and the compensation amount of the vertical line is 0.035 mm, so as to offset the side etching effect in the etching process.
[0011] The silk-screen process is used to coat the etching-resistant ink, the film with the compensated circuit pattern is accurately attached to the plate, and silk-screen processing is performed.
[0012] The plate after the silk-screen processing is subjected to UV curing, and the curing energy is controlled to be 600-800 mJ / cm².
[0013] The etching speed is set to be 3.2-3.5 m / min, and the plate after the curing is subjected to etching processing.
[0014] The plate after the etching is subjected to film removal processing, and the surface etching-resistant ink is removed.
[0015] As an optional technical solution of the method for preparing a fine-pitch single-sided thick copper circuit board based on a silk-screen process, at least one side of the film and the plate edge is reserved with a process reserved area during the silk-screen processing, and the width of the process reserved area is not less than 8 mm.
[0016] As an optional technical solution of the method for preparing a fine-pitch single-sided thick copper circuit board based on a silk-screen process, the etching-resistant ink is not coated on the process reserved area.
[0017] As an optional technical solution of the method for preparing a fine-pitch single-sided thick copper circuit board based on a silk-screen process, after the single-sided copper-clad plate is selected, the cutting is performed, and the plate pretreatment step is further included: the single-sided copper-clad plate is placed in a 120℃ hot air circulation oven for constant temperature pre-baking for 4 hours, so that the water content of the plate is reduced to below 0.5%, and after the pre-treatment, the plate is stored in an environment with a temperature ≤ 25℃ and a relative humidity ≤ 50% for not more than 24 hours.
[0018] As an optional technical scheme of the method for preparing the single-sided thick copper circuit board with fine pitch based on the silk-screen process, preset parameters of the silk-screen process include that the screen is 120T-140T mesh, the screen tension is controlled at 23-25 N / cm2; the doctor blade is white rubber material, the hardness is 70 degrees, and the angle is 60-75 degrees; the printing speed is 3.3-4.0 m / min, the screen distance is 4-6 mm, and the ink film thickness after printing is controlled at 1.20 MIL (about 30 microns).
[0019] As an optional technical scheme of the method for preparing the single-sided thick copper circuit board with fine pitch based on the silk-screen process, the etching solution in the etching process is an acidic copper chloride solution.
[0020] As an optional technical scheme of the method for preparing the single-sided thick copper circuit board with fine pitch based on the silk-screen process, the copper ion concentration in the acidic copper chloride solution is 90 g / L, the hydrochloric acid concentration is 210 g / L, and the etching temperature is controlled at 45 DEG C.
[0021] As an optional technical scheme of the method for preparing the single-sided thick copper circuit board with fine pitch based on the silk-screen process, the etching-resistant ink is one of liquid photoresist ink or special model ultraviolet curing etching-resistant ink.
[0022] As an optional technical scheme of the method for preparing the single-sided thick copper circuit board with fine pitch based on the silk-screen process, the board material is pretreated after being selected and before being cut.
[0023] As an optional technical scheme of the method for preparing the single-sided thick copper circuit board with fine pitch based on the silk-screen process, the board material is batch-identified after being cut.
[0024] The beneficial effects of the present application are as follows:
[0025] 1. The present application successfully replaces the high-cost pattern exposure process with the low-cost silk-screen process by optimizing the silk-screen process parameters and introducing the pre-compensation design, omits the complex steps such as film pasting, exposure and development, and reduces the manufacturing cost of the single-sided board precision circuit by about 10%-15%, thereby greatly improving the market competitiveness of the product.
[0026] 2. The present application breaks through the precision limit of the traditional silk-screen process, stably realizes the fine pitch circuit production with a line width / line distance of 0.15 mm on a 2-ounce thick copper substrate, the circuit edge is regular, the size tolerance is controlled within ±10%, and the application requirements of high-density electronic products are met.
[0027] 3. The present application ensures the repeatability and stability of the process by the systematic solution of “engineering data pre-compensation + high-precision silk-screen parameters + controllable etching process”, the material utilization rate is more than 79.66%, the good product rate is high, and the present application is suitable for batch production.
[0028] 4、The method is not only suitable for CEM-1 and FR-4 material copper-clad substrates, but also can be popularized to other types of single-sided copper-clad plates, and has important significance for promoting the technical upgrading and product structure optimization of the entire single-sided plate industry.
[0029] 5、Compared with the graphic exposure process, the silk printing process steps of the application are less, the generated pollutants are less, the environmental protection treatment cost is lower, and the development trend of green manufacturing is met. BRIEF DESCRIPTION OF DRAWINGS
[0030] Figure 1 The whole method schematic diagram of the embodiment of the application is shown in the figure; DETAILED DESCRIPTION
[0031] The application will be further described in detail below in combination with the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the application, but not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings, not all the structures.
[0032] In the description of the application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication of two element
[0033] insides or the interaction relationship of two elements. For ordinary skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.
[0034] In the application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include the direct contact of the first and second features, or can include the contact of the first and second features through another feature between them. Moreover, the "upper", "upper" and "upper" of the first feature to the second feature include the vertical direction of the first feature above and oblique above the second feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature to the second feature include the vertical direction of the first feature below and oblique below the second feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.
[0035] In the description of the embodiment, the terms "upper", "lower", "left", "right" and other orientation or position relationship are based on the orientation or position relationship shown in the drawings, only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore cannot be understood as a limitation of the application.
[0036] In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more. In addition, the terms "first", "second" are only used to distinguish in the description, and have no special meaning.
[0037] The application discloses a method for preparing a fine-pitch single-sided thick copper circuit board based on a silk screen printing process, comprising the following steps:
[0038] A single-sided copper-clad plate is selected, the copper thickness of the single-sided copper-clad plate is 2 ounces, the single-sided copper-clad plate is cut into a production plate according to original circuit design data corresponding to a preset cutting drawing, a transmission direction of subsequent processing of the plate is taken as a reference, lines in the original circuit perpendicular to the transmission direction are defined as horizontal lines, and lines in the original circuit parallel to the transmission direction are defined as vertical lines, size pre-compensation is performed on the original circuit pattern for a fine-pitch requirement of a target line width / line pitch ≤0.15 mm, the compensation amount of the horizontal lines is 0.025 mm, and the compensation amount of the vertical lines is 0.035 mm, so as to offset a side etching effect in an etching process, resist etching ink is coated by using a silk screen printing process, a film on which the compensated circuit pattern is drawn is precisely attached to the plate and is subjected to silk screen printing treatment, the plate subjected to the silk screen printing is subjected to UV curing, the curing energy is controlled to be 600-800 mJ / cm2, the etching speed is set to be 3.2-3.5 m / min, the plate after curing is subjected to etching treatment, the etching liquid used in the etching treatment is an acidic copper chloride solution, the copper ion concentration of the acidic copper chloride solution is 90 g / L, the hydrochloric acid concentration of the acidic copper chloride solution is 210 g / L, and the etching temperature is 45°C, and the plate after etching is subjected to film removal treatment, and the surface resist etching ink is removed, so as to prepare for subsequent processes.
[0039] Specifically, in the embodiment, the plate material is CEM-1 epoxy paper copper-clad plate commonly used in the industry (FR-4 glass cloth copper-clad plate can also be selected according to actual requirements, and both kinds of plate materials can adapt to the process parameters of the application). When selected, the copper-clad plate needs to be comprehensively inspected, the surface of the copper-clad plate is observed through a 10-fold magnifying glass, it is ensured that the copper layer is free of scratches, oxidation spots and pits, the plate is free of cracks, bubbles and resin flow marks, and the edge is free of burrs or damage; the width dimension of the copper-clad plate is measured by using a two-dimensional image instrument, and it is ensured that the original plate size meets the cutting requirement of the preset cutting drawing.
[0040] Meanwhile, to ensure that the ink does not bubble, the copper layer does not peel off or the circuit is not deformed during the subsequent silk screen printing and etching process due to water evaporation, a board pretreatment step is required after the single-sided copper-clad board is selected and before cutting. In this embodiment, a precision hot air circulation oven dedicated to PCBs is used. This equipment has temperature uniformity control function (temperature control accuracy ±2°C), adjustable hot air circulation rate (1.5-2.0 m / s), and is equipped with an independent exhaust system to timely exhaust the water vapor evaporated in the oven. During pretreatment, the copper-clad board that has passed the incoming material inspection is stacked neatly according to the standard of "≤20 pieces per stack", with a gap of 5-8 mm between the boards to ensure uniform hot air penetration, and a hard epoxy pad is placed at both ends to prevent warping at high temperatures; then the oven is started and the target temperature is set to 120°C, and after preheating for 30 minutes and the temperature is stable (continuous 10 minutes fluctuation ≤±2°C), the stacked board is placed in the middle shelf of the oven, and the temperature is kept at 120°C for 4 hours, during which the oven should not be opened frequently; after the pre-baking is completed, the heating function is turned off and the hot air circulation is maintained, and the board is naturally cooled to below 60°C before being taken out, to avoid rapid moisture absorption of the high-temperature board. The moisture content of the pre-baked board should be detected by a Karl Fischer moisture meter (accuracy 0.01%), and 3 pieces of board are randomly taken from each batch, and samples are taken from the corners and the middle area (sample weight 5g). The moisture content should be reduced to below 0.5% by pyrolysis gravimetric method. If a sample exceeds the standard, the board in this batch should be re-baked for 1 hour and then re-tested until all samples meet the standard.
[0041] The pretreated board should be placed in a constant temperature and humidity storage cabinet in an environment with a temperature of ≤25°C and a relative humidity of ≤50%, and the board should be sealed in an anti-static and moisture-proof bag, with the pre-treatment completion time marked on each bag, to ensure that the interval between pre-treatment and cutting does not exceed 24 hours, to avoid secondary moisture absorption.
[0042] After the substrate pretreatment is completed, the cutting drawing confirmation and cutting equipment calibration should be completed before cutting. According to the original circuit design data (GERBER file) corresponding to the pre-set cutting drawing, the cutting size, the number of spliced boards and the position of the circuit function area are checked by engineering and technical personnel to ensure that the size of the cut board can adapt to subsequent film fitting, silk screen printing and other processes. After the board is cut, the board is batch marked to realize production process traceability. In this embodiment, a PCB dedicated laser marking machine is used to mark the board in the non-functional area (away from the circuit and the subsequent process reserved area) with a board edge of ≥5mm. The marking content includes batch number, production date, raw material batch number, board number, marking character height 1mm, line width 0.2mm, clear and distinguishable, no fuzzy pen, no falling after 5 times of 75% alcohol wiping, to realize the whole link traceability from raw materials to cutting board, facilitate subsequent quality problem investigation, and save scrap cost.
[0043] When printing, 8mm of process reserved area (8mm is the minimum requirement) is required on one side edge of the plate, which is used for hanging nail positioning in subsequent surface treatment. The anti-etching ink is not applied to the process reserved area. The process reserved area is covered with no ink through the film design and CCD visual positioning. If necessary, high-temperature resistant adhesive tape can be used for auxiliary shielding.
[0044] The anti-etching ink is one of liquid light-sensitive anti-etching ink or special model ultraviolet curing anti-etching ink. In this embodiment, ultraviolet curing anti-etching ink is selected. The ink has the advantages of high resolution, high anti-etching property, fast curing speed, etc. It is suitable for silk printing requirements of 120T-140T screen. The silk printing parameters are set as follows: 120T-140T screen is selected, the screen tension is controlled at 23-25N / cm² (measured by screen tension meter, the deviation of 5 test points is ≤1N / cm²), the screen is coated with 15μm thick photosensitive glue and the line pattern is transferred after exposure and development compensation, and the screen is cleaned with anhydrous ethanol before use; the scraper is selected to be white glue material with a hardness of 70°, the angle is adjusted to 60°-75°, and the pressure is set to 0.3MPa; the printing speed is 3.3-4.0m / min, and the screen distance is 4-6mm, so as to ensure that the ink film thickness after printing is controlled at 1.20MIL (about 30μm). In this embodiment, the line width is 0.15mm and the line distance is 0.2mm. The screen is 120T, the angle is adjusted to 65°, the screen distance is adjusted to 5mm, and the printing speed is 3.3m / min. The printing speed and screen distance are strictly controlled. The line width tolerance after etching is less than 0.2mm, which is controlled at ±10%.
[0045] Through the systematic process design of "substrate pretreatment → cutting and batch identification → line pre-compensation → silk printing anti-etching ink → UV curing → etching → film removal", combined with precise parameter control, the low-cost silk printing process successfully replaces the traditional pattern exposure process, breaks through the technical bottleneck of fine pitch production of thick copper single-sided board in the prior art, realizes stable batch production, and has significant economic value and industry application prospect.
[0046] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application is disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification made to the above embodiment based on the technical solution of the present application shall fall within the scope of the technical solution of the present application.
Claims
1. A method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process, characterized in that, Includes the following steps: Select a single-sided copper-clad laminate with a copper thickness of 2 ounces. Cut the single-sided copper-clad laminate into production boards according to the original circuit design data corresponding to the preset cutting drawings. Based on the conveying direction of the subsequent processing of the sheet metal, the lines perpendicular to the conveying direction in the original line are defined as horizontal lines, and the lines parallel to the conveying direction are defined as vertical lines. To meet the fine detail requirements of a target line width / spacing ≤ 0.15mm, the original circuit pattern is pre-compensated for size, with horizontal lines receiving a compensation of 0.025mm and vertical lines receiving a compensation of 0.035mm, in order to counteract the side etching effect during the etching process. The screen printing process is used to apply anti-etching ink, and the film with the compensated circuit pattern is precisely attached to the board material and then screen printed. UV curing is performed on the screen-printed board material, with the curing energy controlled at 600-800mJ / cm². The etching speed is set to 3.2-3.5 m / min, and the cured board material is etched. The etched board is then subjected to a film removal process to remove the surface anti-etching ink.
2. The method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 1, characterized in that, During screen printing, a process reservation area is reserved on at least one side of the film and the edge of the board, and the width of the process reservation area is not less than 8mm.
3. The method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 2, characterized in that, The anti-etching ink is not applied to the process reserved area.
4. The method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 1, characterized in that, After selecting a single-sided copper-clad laminate and before cutting, a pre-treatment step is also included: the single-sided copper-clad laminate is placed in a 120℃ hot air circulating oven for constant temperature pre-drying for 4 hours to reduce the moisture content of the laminate to below 0.5%. After pre-treatment, it is stored in an environment with a temperature ≤25℃ and relative humidity ≤50% for no more than 24 hours.
5. The method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 1, characterized in that, The preset parameters for screen printing include: screen size of 120T-140T, screen tension controlled at 23-25N / cm²; squeegee made of white rubber material, hardness 70°, angle 60°-75°; printing speed 3.3-4.0m / min, screen distance 4-6mm, and ink film thickness after printing controlled at 1.20MIL (approximately 30μm).
6. The method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 1, characterized in that, The etching solution used in the etching process is an acidic copper chloride solution.
7. A method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 5, characterized in that, The acidic copper chloride solution contains 90 g / L copper ions and 210 g / L hydrochloric acid, and the etching temperature is controlled at 45°C.
8. The method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to claim 1, characterized in that, The anti-etching ink is either liquid photoresist ink or a specific type of UV-curable anti-etching ink.
9. A method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to any one of claims 1, characterized in that, After selecting a single-sided copper-clad laminate, pre-treatment of the board material is carried out before cutting.
10. A method for preparing a single-sided thick copper circuit board with fine pitch based on screen printing process according to any one of claims 1, characterized in that, After cutting the sheet metal, batch identification management is implemented for the sheet metal.