Processing method of boss of metal-based printed circuit board
By combining laser processing and plasma activation with conductive carbon deposition, the problems of large boss errors and high precious metal loss in existing technologies have been solved, achieving high-precision boss processing and improving the stability of thermal and electrical conductivity and manufacturing efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG ELLINGTON ELECTRONICS TECH CO LTD
- Filing Date
- 2026-03-27
- Publication Date
- 2026-05-15
AI Technical Summary
In existing technologies, the etching and embedding process for preparing copper bosses results in large errors and high loss of precious metals. Chemical etching of grooves followed by electroplating filling leads to bonding problems between PP and copper bosses, and unstable or failed thermal and electrical conductivity.
The grooves are processed by laser, combined with plasma technology to activate the groove walls and two pattern transfers. Blind grooves are formed by UV laser ablation, and the adhesive is removed by plasma method. Conductive carbon is deposited to enhance the adhesion between the copper layer and PP, so as to achieve precise alignment and size control.
It significantly improves the positioning and dimensional accuracy of the boss, controlling it to ≤60μm, reducing precious metal loss, improving manufacturing efficiency and simplifying the process. It is suitable for a variety of PP materials, reducing environmental pressure and manual operation risks.
Smart Images
Figure CN122054462A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of printed circuit board manufacturing technology, and more specifically, to a method for processing bosses on metal-based printed circuit boards. Background Technology
[0002] Currently, there are two main process routes for manufacturing metal-based bosses on circuit boards: etching bosses + embedding method and additive method.
[0003] The first type of etching boss + embedding process is as follows: Figure 1 and Figure 2 As shown, a boss structure is first formed by etching a window on the copper substrate surface. Then, holes are drilled in the copper foil and PP board respectively, and the boss is embedded in the opening before pressing. This processing method has the following disadvantages: (1) Drilling holes in the copper foil, PP and copper substrate separately can easily lead to positioning deviations, resulting in failure to rivet or difficulty in rivet during pressing; (2) The boss is formed by etching, and its length, width and height are affected by the size of the window of the outer dry film, etching parameters and etching solution concentration. There are large errors between batches (industry experience tolerance ±75μm), which can easily lead to failure to embed the copper foil and PP in the later stage; (3) The cost of precious metal loss is high. The area of the boss generally accounts for no more than 10% of the total board area, which means that the copper loss on one side when etching the boss is 90% of the total area. For example, 1m 2 To create a 0.12mm high etched boss on a copper plate, the copper waste is 0.9 * 0.12 / 1000 * 8.96 * 1000000 = 967.68g. Given that the current international copper price is 80 RMB / kg, this means that for every 1m of etched boss, the copper waste would be... 2 The copper loss is 77.36 RMB; (4) When PP is RCC type (without glass fiber filling), ordinary mechanical milling machine cannot achieve mass production of milling grooves; (5) The bonding force between copper base and PP is easily affected by browning, pressing and other methods, and copper base bosses are easily separated from PP (only satisfying 3 times of thermal stress, 5 times of lead-free reflow at 290℃, and 500 hours of cycling at -45℃~125℃); (6) The overall production process is complicated and the production cost is high.
[0004] like Figure 3As shown, the specific process of the second chemical etching preparation of dielectric-free groove + electroplating filling (addition method) is as follows: (copper substrate + PP + copper foil) lamination → cutting → drilling → pattern transfer → etching window opening → chemical ablation (98% concentrated sulfuric acid) → sandblasting → second pattern transfer → pattern electroplating 1 → pattern electroplating 2 (turning the chuck) → film removal → third pattern transfer → etching (finished pattern area) → subsequent finished product process. This type of processing method has the following disadvantages: (1) It requires three pattern transfers to produce the boss heat-conducting PAD required by the customer. The alignment accuracy is poor. According to the single alignment accuracy of 50 / 50μm, the alignment deviation of the three pattern transfers reaches 150μm; (2) The boss windowing method uses etched copper foil. The windowing tolerance is greatly affected by the activity of the chemical and the etching time, and the size deviation will be larger (based on industry data, the etching windowing tolerance is ±30μm); (3) Using concentrated sulfuric acid to etch PP to prepare the groove will dehydrate, carbonize and change the molecular bond structure of the resin filler in pure rubber PP. The direct manifestation is that the resin in the tank wall will lose its activity, become loose and the tank wall will be uneven, resulting in poor quality. The thermal and electrical conductivity of the product is reduced or lost; when the dielectric layer is PP (prepreg) containing glass fiber, the concentrated sulfuric acid ablation method cannot remove the glass fiber, which will cause the glass fiber to protrude or connect, limiting the types of products it can be used for; concentrated sulfuric acid is a highly hazardous chemical, generally used for equipment maintenance or standard solution preparation after dilution. Direct use in PCB product production has disadvantages such as being environmentally unfriendly, difficult to judge the effectiveness of the solution, and highly dangerous (easily causing personnel to be injured by concentrated sulfuric acid corrosion, equipment corrosion, and deterioration of the workshop environment), making it almost impossible to enter mass production; if the PP on the tank wall is not cleaned, activated, and made conductive before pattern electroplating, the PP on the tank wall does not have conductive properties. Therefore, by connecting the electroplating clamps to the copper base layer (such as... Figure 4 As shown in the figure, the copper layer is filled by utilizing the conductivity of the copper substrate. However, there will be gaps between the electroplated copper layer and the PP wall of the tank. Voids are prone to appear inside the electroplated filling, which will lead to extremely unstable or direct failure of thermal and electrical conductivity.
[0005] In view of the above, this application is hereby submitted. Summary of the Invention
[0006] The existing technology has problems such as large errors and high loss of precious metals in the preparation of copper bosses by etching and embedding. In order to solve the above problems, chemical etching of grooves and electroplating filling are prone to bonding problems between PP and copper bosses, resulting in extremely unstable thermal and electrical conductivity or direct failure. In order to solve the above technical problems, this invention provides a processing method for metal-based printed circuit board bosses. It uses laser processing of grooves and activation of the inner wall of the grooves combined with two pattern transfers for alignment. The positioning accuracy and dimensional accuracy of the thermally conductive PAD are significantly improved. The positioning accuracy can be controlled within ≤60μm and the dimensional tolerance can be controlled within ±10μm.
[0007] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for processing bosses on a metal-based printed circuit board, comprising the following steps: S1, press the copper substrate with the PP board and copper foil to obtain the laminated board; S2, a blind groove extending to the copper substrate is formed by laser processing on the surface of the lamination plate; S3 uses plasma technology to activate and clean the walls and bottom of the blind tank; S4, a layer of conductive carbon is deposited on the tank wall through physical adsorption; S5, perform the first graphic transfer on the blind slot area; S6, the copper filling of the boss is completed in the blind groove of the pattern electroplating; S7, remove the film and use a grinding plate to flatten and reduce the height difference of the raised part around the copper boss in the blind groove; S8, the second graphic transfer.
[0008] This invention uses laser processing to form blind grooves through UV laser ablation, eliminating the need for additional etching and windowing. It achieves high alignment accuracy, ensuring precise groove alignment and dimensions. The resin and glass fiber in the groove wall are almost completely carbonized, eliminating the need for browning or copper breaking. This significantly improves the bonding strength between the copper layer and the groove wall after filling, greatly enhancing manufacturing efficiency.
[0009] This invention employs the plasma method for resin removal. By using N2 and CF4 plasma gases to activate the resin on the surface of the tank wall and clean the residual resin at the bottom of the tank, the bonding force between the subsequent copper plating and PP can be enhanced, thus avoiding gaps between the electroplated copper layer and the PP on the tank wall.
[0010] After cleaning the tank walls and bottom, the present invention blackens the tank walls, thereby depositing a very thin layer of conductive carbon on the tank walls. This mainly serves to pre-conduct the PP in the tank walls and enhance the bonding force between the electroplated copper layer and the dielectric layer.
[0011] This invention utilizes laser-processed grooves combined with two pattern transfer alignments to significantly improve the positioning and dimensional accuracy of the thermally conductive PAD. The positioning accuracy can be controlled within ≤60μm, and the dimensional tolerance can be controlled within ±10μm.
[0012] In a specific embodiment, in step S1, the specific method of lamination is as follows: first, the copper substrate is subjected to oxidation and surface roughening treatment, the equipment combination of which is 600# sanding belt + 400# non-woven fabric + 600# sandblasting, and the process parameters are linear speed 1.9m / min and pressure 1.5kg / cm. 2Stack the copper-based PP-copper foil in the following order, and then press them together using a regular hydraulic press. It is important to note that the high temperature should be maintained at 280℃ for 90 minutes and the cold pressing time should be ≥45 minutes. The other parameters can be the same as those for regular pressing.
[0013] In one specific implementation, in step S2, a blind groove is formed using UV laser ablation. The blind groove processing is achieved using a short-wavelength laser with a wavelength of 200 nanometers, divided into two laser beams. The first beam, with a small spot, breaks down the copper and cuts the polypropylene (PP), while the second beam, with a large spot, cleans the residual adhesive at the bottom. Electron microscopy and cross-section analysis show that minor copper damage of 3-5 μm is acceptable; damage exceeding this range requires adjustment of the energy and time of the second laser beam.
[0014] In a specific implementation, in step S3, N2 and CF4 plasma gases are used to activate the resin on the surface of the tank wall and clean the residual resin at the bottom of the tank. The treatment time is 15-20 minutes.
[0015] In a specific embodiment, the conductive carbon deposition method in step S4 is as follows: PI adjustment - micro-etching 1 - blackening 1 - micro-etching 2 - blackening 2 - anti-oxidation - drying.
[0016] In one specific embodiment, in step S4, the conductive carbon is a carbon functional group with a particle size of 100 μm.
[0017] In a specific implementation, the specific process of the first pattern transfer in step S5 is as follows: pretreatment - film application - LDI exposure - development, wherein the initial setting of the PE / JE value of the exposure machine during LDI exposure is 25 / 25μm, and an automatic expansion and contraction working mode is adopted, and the remaining processes can be carried out according to the industry's conventional process parameters.
[0018] In a specific implementation, the specific process of pattern electroplating in step S6 is as follows: Before filling the blind slots, they are soaked in a pre-impregnation solution, including a brightener and a wetting agent; Electroplating is performed in a blind tank using a filling solution: The hole-filling solution includes sulfuric acid 50-70g / L, copper ions 240-260g / L, polishing agent 3-5ml / L, chloride ions 75-100ppm, leveling agent 14-16ml / L, and wetting agent 18-22ml / L; The electroplating parameters are: current density of 65 ASF, copper plating time of 140-150 min, and copper plating rate of 1.35 μm / min; and 60-70 ASF, copper plating time of 140-150 min, and copper plating rate of 1.25-1.45 μm / min.
[0019] In a specific implementation, in step S7, the grinding plate is a combination of 400# ceramic, 240# abrasive belt and 600# non-woven fabric, with a linear speed of 1.9m / min and grinding 1-2 times until there is no obvious boundary between the raised area and the surface area of the copper boss.
[0020] In a specific implementation, the specific process of the second pattern transfer in step S8 is as follows: pretreatment - film application - LDI exposure - development - acid etching. During LDI exposure, the initial PE / JE value of the exposure machine is set to 25 / 25μm, and an automatic expansion and contraction working mode is adopted. After the second pattern transfer, etching is performed. During etching, the parameters are set according to the copper thickness. For the case where the copper thickness on the metal substrate is about 60-70, the etching speed is 3.5m / min and the upper and lower pressures are 2.5 / 2.8. The remaining parameters can be the industry's conventional process parameters.
[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention provides a method for processing bosses on metal-based printed circuit boards. The method uses laser processing to form blind grooves by UV laser ablation, without the need for additional etching and windowing. The alignment accuracy is high, ensuring the accuracy of groove alignment and dimensions. The resin and glass fiber in the groove wall are almost not carbonized, eliminating the need for browning and copper breaking. This significantly improves the bonding force between the copper layer and the groove wall after filling, greatly improving the manufacturing efficiency. 2. The present invention provides a method for processing metal-based printed circuit board bosses, which uses plasma method to remove adhesive. By using N2 and CF4 plasma gases to activate the resin on the surface of the tank wall and clean the residual resin at the bottom of the tank, the bonding force between the subsequent copper plating and PP can be enhanced, and gaps between the electroplated filler copper layer and the PP tank wall can be avoided. 3. The embodiment of the present invention provides a processing method for a metal-based printed circuit board boss. After cleaning the tank wall and bottom, the tank wall is blackened to deposit a very thin layer of conductive carbon on the tank wall. This mainly serves to pre-conduct the PP in the tank wall and enhance the bonding force between the electroplated copper layer and the dielectric layer. 4. The embodiment of the present invention provides a processing method for metal-based printed circuit board bosses, which utilizes laser processing of grooves combined with two pattern transfers for alignment, significantly improving the positioning accuracy and dimensional accuracy of the thermally conductive PAD. The positioning accuracy can be controlled within ≤60μm, the dimensional tolerance within ±10μm, and the height difference between the copper boss and the surface <5μm. 5. The processing method of the metal-based printed circuit board boss provided in the embodiment of the present invention was tested under the following conditions: 8 cycles of thermal stress, 10 cycles of lead-free reflow at 290℃, and 1000 hours of thermal shock at -55℃ to 125℃. The boss and PP did not separate and there were no cracks inside the boss. 6. The processing method for metal-based printed circuit board bosses provided in this embodiment of the invention has the shortest overall process, requiring only 11 processes to complete the semi-finished product production, and significantly reducing process and material costs. 7. The processing method for metal-based printed circuit board bosses provided in this embodiment of the invention is applicable to various types of PP materials, and can efficiently and stably process both RCC-type PP (pure PP) and glass fiber-containing PP. 8. The present invention provides a method for processing metal-based printed circuit board bosses, which does not require the preparation of a large number of hazardous chemicals on site, has low environmental pressure, and can be automated through equipment throughout the process, reducing the risk of manual operation and improving efficiency. Attached Figure Description
[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.
[0023] Figure 1 This invention provides a flowchart of the existing etching boss manufacturing process; Figure 2 This is a schematic diagram of the etched boss provided by the present invention; Figure 3 This is a schematic diagram of the chemical ablation groove + electroplating filling provided by the present invention; Figure 4 This is a schematic diagram of the chemical ablation electroplating pinch point provided by the present invention; Figure 5 This is a schematic diagram of the main process for preparing copper bosses using the blind slot addition method provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the boss provided in an embodiment of the present invention; Figure 7 This is a slice image of the green light picosecond laser processing of the boss provided in an embodiment of the present invention; Figure 8 This is a plan view of the green light picosecond laser processing of the boss provided in an embodiment of the present invention; Figure 9 This is a slice image of the boss pattern after electroplating, provided in an embodiment of the present invention. Figure 10 This is a plan view of the boss pattern after electroplating provided in an embodiment of the present invention; Figure 11 This is a schematic diagram of the electroplating clamp provided in an embodiment of the present invention. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.
[0025] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.
[0026] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0027] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this document; "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) can be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.
[0028] Currently, there are two main process routes for manufacturing metal-based bosses on circuit boards: etching bosses + embedding method and additive method.
[0029] The first type of etching boss + embedding process is as follows: Figure 1 and Figure 2As shown, a boss structure is first formed by etching a window on the copper substrate surface. Then, holes are drilled in the copper foil and PP board respectively, and the boss is embedded in the opening before pressing. This processing method has the following disadvantages: (1) Drilling holes in the copper foil, PP and copper substrate separately can easily lead to positioning deviations, resulting in failure to rivet or difficulty in rivet during pressing; (2) The boss is formed by etching, and its length, width and height are affected by the size of the window of the outer dry film, etching parameters and etching solution concentration. There are large errors between batches (industry experience tolerance ±75μm), which can easily lead to failure to embed the copper foil and PP in the later stage; (3) The cost of precious metal loss is high. The area of the boss generally accounts for no more than 10% of the total board area, which means that the copper loss on one side when etching the boss is 90% of the total area. For example, 1m 2 To create a 0.12mm high etched boss on a copper plate, the copper waste is 0.9 * 0.12 / 1000 * 8.96 * 1000000 = 967.68g. Given that the current international copper price is 80 RMB / kg, this means that for every 1m of etched boss, the copper waste would be... 2 The copper loss is 77.36 RMB; (4) When PP is RCC type (without glass fiber filling), ordinary mechanical milling machine cannot achieve mass production of milling grooves; (5) The bonding force between copper base and PP is easily affected by browning, pressing and other methods, and copper base bosses are easily separated from PP (only satisfying 3 times of thermal stress, 5 times of lead-free reflow at 290℃, and 500 hours of cycling at -45℃~125℃); (6) The overall production process is complicated and the production cost is high.
[0030] like Figure 3As shown, the specific process of the second chemical etching preparation of dielectric-free groove + electroplating filling (addition method) is as follows: (copper substrate + PP + copper foil) lamination → cutting → drilling → pattern transfer → etching window opening → chemical ablation (98% concentrated sulfuric acid) → sandblasting → second pattern transfer → pattern electroplating 1 → pattern electroplating 2 (turning the chuck) → film removal → third pattern transfer → etching (finished pattern area) → subsequent finished product process. This type of processing method has the following disadvantages: (1) It requires three pattern transfers to produce the boss heat-conducting PAD required by the customer. The alignment accuracy is poor. According to the single alignment accuracy of 50 / 50μm, the alignment deviation of the three pattern transfers reaches 150μm; (2) The boss windowing method uses etched copper foil. The windowing tolerance is greatly affected by the activity of the chemical and the etching time, and the size deviation will be larger (based on industry data, the etching windowing tolerance is ±30μm); (3) Using concentrated sulfuric acid to etch PP to prepare the groove will dehydrate, carbonize and change the molecular bond structure of the resin filler in pure rubber PP. The direct manifestation is that the resin in the tank wall will lose its activity, become loose and the tank wall will be uneven, resulting in poor quality. The thermal and electrical conductivity of the product is reduced or lost; when the dielectric layer is PP (prepreg) containing glass fiber, the concentrated sulfuric acid ablation method cannot remove the glass fiber, which will cause the glass fiber to protrude or connect, limiting the types of products it can be used for; concentrated sulfuric acid is a highly hazardous chemical, generally used for equipment maintenance or standard solution preparation after dilution. Direct use in PCB product production has disadvantages such as being environmentally unfriendly, difficult to judge the effectiveness of the solution, and highly dangerous (easily causing personnel to be injured by concentrated sulfuric acid corrosion, equipment corrosion, and deterioration of the workshop environment), making it almost impossible to enter mass production; if the PP on the tank wall is not cleaned, activated, and made conductive before pattern electroplating, the PP on the tank wall does not have conductive properties. Therefore, by connecting the electroplating clamps to the copper base layer (such as... Figure 4 As shown in the figure, the copper layer is filled by utilizing the conductivity of the copper substrate. However, there will be gaps between the electroplated copper layer and the PP wall of the tank. Voids are prone to appear inside the electroplated filling, which will lead to extremely unstable or direct failure of thermal and electrical conductivity.
[0031] To address the aforementioned problems, this invention provides a method for processing bosses on a metal-based printed circuit board, as detailed below.
[0032] Example like Figures 5-11 As shown, this invention provides a method for processing bosses on a metal-based printed circuit board, specifically a processing flow for boss PADs with a length and width of 3000-7000μm and a height of 100μm-150μm. The main process is as follows: (copper substrate + PP + copper foil) lamination → cutting → drilling → UV laser processing → Plasma → blackening → first pattern transfer → pattern electroplating → film removal + grinding → second pattern transfer → etching (finished pattern area) → subsequent finished product processes. The specific method is as follows: (1) Press copper-based material, PP and copper foil together Experimental board 1: 1.2mm copper base + 125μm RCC + 70μm copper foil lamination Experimental board 2: 1.2mm copper base + 150μm FR-4 + 70μm copper foil lamination (2) Laser processing of blind grooves on the surface of the press plate Tool design and parameter control: Green light picosecond photoplotting data: The processing area size is based on the original artwork; Outer graphic: The graphic window is 4 mil larger on each side than the laser area; Drilling: The purpose is to drill laser positioning holes and outer layer positioning holes. The parameters used are those for thick copper, and the drill bit life is set at 200 holes. Blind slotting: Green light picosecond equipment (short waveform laser equipment) is used to directly form the shape by UV laser ablation (wavelength 200 nanometers, processed by two laser beams, the first beam with a small spot is used to process the size of the blind slot, and the second beam with a large spot is used to clean the bottom). This greatly improves the production efficiency, ensures the accuracy of the slotting size, and the resin and glass fiber in the slot wall are almost not carbonized, which significantly improves the bonding force between the copper layer and the slot wall after filling.
[0033] (3) Plasma: Plasma method for removing adhesive. The main purpose of this step is to activate the resin on the surface of the tank wall with gases such as N2 and CF4, and to clean the residual resin at the bottom of the tank to enhance the adhesion after copper plating. The treatment time is generally 15-20 minutes. The specific parameters are shown in Table 1 below.
[0034] Table 1 .
[0035] (4) Blackening: This step involves depositing a very thin layer of conductive carbon on the tank wall through physical adsorption. This mainly serves to pre-conduct and enhance the bonding force between the electroplated copper layer and the dielectric layer. The detailed steps are: PI adjustment - micro-etching 1 - blackening 1 - micro-etching 2 - blackening 2 - anti-oxidation - drying. Among them, PI adjustment and blackening are the core steps. PI adjustment is a strong reducing functional group, and its main function is to convert the charge of PP on the tank wall to facilitate the subsequent adsorption of conductive carbon. Conductive carbon is a carbon functional group with a particle size of 100μm. The specific parameters are shown in Table 2 below.
[0036] Table 2 .
[0037] (5) First pattern transfer: Only the blind trench area is exposed, and the remaining areas are covered with dry film resist plating; it should be noted that the pretreatment stage of pattern transfer only needs to be acidic.
[0038] (6) Pattern filling: In this stage, the copper filling of the boss is completed in one electroplating step. It is necessary to ensure the copper filling height and speed, and to avoid the problem of voids in the boss. Therefore, the following optimizations are made to the electroplating solution, equipment and parameters: (6.1) Medicinal solution: Pre-impregnation before filling holes: Prepare a high-concentration brightener (a certain propane sulfonate) with a concentration of about 8 ml / L and a wetting agent of 5 ml / L. Immersing the blind tank in the pre-impregnation solution can improve the copper loading rate. Filling tank: sulfuric acid 60g / L, copper ions 250g / L, brightener controlled at 4ml / L (the brightener is a certain propane sulfonate which can accelerate the copper plating rate), chloride ions 90ppm, leveling agent 15ml / L, wetting agent 20ml / L, to improve the withstandable current density and copper plating uniformity.
[0039] (6.2) Equipment: Circulation equipment: It adopts a high-power pump with a circulation volume of 50 MTO per hour (the circulation volume of 50 tank-opening solutions per hour; for example, if the volume of a tank of solutions is 10,000L, 50 MTO / H is 500,000L / H). The high circulation volume maintains the stability of the concentration of copper ions and light-reducing agents in the solution. Spray design: bottom spray + side spray design, in which the bottom spray nozzle is 15° towards the cathode and the side spray nozzle is offset by 15° towards the cathode; the nozzle is designed as a trumpet type, which is intended to increase the spray flow rate to 4ml / L; Fixture design: Adjustable upper and lower clamps, with 4 clamps on each of the upper and lower electroplating edges during the test board electroplating process, thereby dispersing the current input and improving uniformity.
[0040] (6.3) Electroplating parameters: current density of 65 ASF (conventional electroplating current density ≤ 40 ASF), copper plating time of 140-150 min, copper plating rate of 1.35 μm / min (conventional copper plating rate of 0.5-0.8 μm / min). (7) Coating removal + grinding plate: Select a grinding plate combination of 400# ceramic + 240# sanding belt + 600# non-woven fabric, linear speed 1.9m / min, automatic pressure adjustment; grind the plate 1-2 times. Visually, there should be no obvious dividing line between the boss area and the copper surface area. Here, the main purpose is to use the grinding plate to flatten the raised part around the blind groove and further reduce the height difference. After actual testing, the height difference is <5μm.
[0041] (8) Second pattern transfer + etching: During pattern transfer, the exposure alignment PE value / JE value is set to 25μm / 25μm.
[0042] (9) Finished product manufacturing in the later stages: as per customer requirements.
[0043] Performance tests on the obtained boss revealed that under the following conditions: 8 cycles of thermal stress, 10 cycles of lead-free reflow at 290℃, and 1000 hours of thermal shock from -55℃ to 125℃, the boss did not separate from the PP and there were no cracks inside the boss.
[0044] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for processing bosses on a metal-based printed circuit board, characterized in that, Includes the following steps: S1, press the copper substrate with the PP board and copper foil to obtain the laminated board; S2, a blind groove extending to the copper substrate is formed by laser processing on the surface of the lamination plate; S3 uses plasma technology to activate and clean the walls and bottom of the blind tank; S4, a layer of conductive carbon is deposited on the tank wall through physical adsorption; S5, perform the first graphic transfer on the blind slot area; S6, the copper filling of the boss is completed in the blind groove of the pattern electroplating; S7, remove the film and use a grinding plate to flatten and reduce the height difference of the raised part around the copper boss in the blind groove; S8, the second graphic transfer.
2. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S1, the specific method of lamination is as follows: first, the copper substrate is subjected to oxidation and surface roughening treatment, then stacked in the order of copper base-PP-copper foil, and lamination is performed using a hydraulic press.
3. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S2, a blind groove is formed by UV laser ablation.
4. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S3, N2 and CF4 plasma gases are used to activate the resin on the surface of the tank wall and clean the residual resin at the bottom of the tank. The treatment time is 15-20 minutes.
5. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S4, the conductive carbon deposition method is as follows: PI adjustment - micro-etching 1 - blackening 1 - micro-etching 2 - blackening 2 - anti-oxidation - drying.
6. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S4, the conductive carbon is a carbon functional group with a particle size of 100 μm.
7. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S5, the specific process of the first pattern transfer includes pretreatment, film application, LDI exposure, and development. During LDI exposure, the initial PE / JE value of the exposure machine is set to 25 / 25μm, and an automatic expansion and contraction working mode is adopted.
8. The method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S6, the specific process of pattern electroplating is as follows: Before filling the blind slots, they are soaked in a pre-impregnation solution, including a brightener and a wetting agent; Electroplating is performed in a blind tank using a filling solution: The pore-filling solution includes sulfur (50-70 g / L), copper ions (240-260 g / L), polishing agent (3-5 ml / L), chloride ions (75-100 ppm), leveling agent (14-16 ml / L), and wetting agent (18-22 ml / L). The electroplating parameters are: current density of 60-70 ASF, copper plating time of 140-150 min, and copper plating rate of 1.25-1.45 μm / min.
9. A method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S7, the grinding plate is a combination of 400# ceramic, 240# abrasive belt and 600# non-woven fabric. The linear speed is 1.9m / min and the grinding plate is ground 1-2 times until there is no obvious dividing line between the raised area and the surface area of the copper boss.
10. A method for processing bosses on a metal-based printed circuit board according to claim 1, characterized in that, In step S8, the specific process of the second pattern transfer includes pretreatment, film application, LDI exposure, development, and acid etching. During LDI exposure, the initial PE / JE value of the exposure machine is set to 25 / 25μm, and an automatic expansion and contraction working mode is adopted.