High-reliability POFV plate manufacturing process

Abstract

The invention discloses a manufacturing process of a high-reliability POFV plate. The manufacturing process comprises the following steps: a pre-process; drilling holes; first copper deposition; vCP electroplating is carried out; plugging the hole with resin; a ceramic grinding plate; depositing copper II; plate surface electroplating; drying the film; performing acid etching; and post-working procedures. According to the high-reliability POFV plate manufacturing process provided by the invention, the possibility of bubbling and layering phenomena of the POFV plate can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit boards, and in particular to a high-reliability POFV board manufacturing process. Background Art

[0002] PCBs, or printed circuit boards, are the support for electronic components. Almost every electronic device, from small electronic watches and calculators to large computers, communications equipment, and military weapon systems, that contains integrated circuits and other electronic components, requires a PCB to interconnect them. PCBs consist of an insulating base, connecting wires, and pads for assembling and soldering electronic components. They serve the dual purpose of conducting circuits and insulating base.

[0003] With the advancement of technology, circuit board manufacturing processes are constantly being updated to keep pace with these trends. Consequently, the application of the POFV process has become increasingly widespread. The POFV (Plated On Filled Via) process involves drilling holes in a circuit board and depositing copper inside them to create plated holes, enabling connectivity between corresponding circuit layers. The holes are then plugged with resin, and any excess resin removed from the openings. Finally, copper is deposited on the surface of the plugged holes. The POFV process can reduce board area, resolve wiring and routing issues, and increase wiring density.

[0004] However, the existing POFV process still has some shortcomings in practical applications. For example, the copper covering the surface of the POFV board with dense holes is prone to bubbling and delamination after the subsequent reflow soldering of electronic components, resulting in batch scrapping and affecting the yield rate. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a high-reliability POFV board manufacturing process that can effectively reduce the possibility of bubbling and delamination of POFV boards.

[0006] A high-reliability POFV board manufacturing process proposed in the present invention includes the following steps: S1: pre-process; S2: Drilling, drilling holes on the PCB board; S3: copper plating 1, performing copper plating treatment on the PCB board to form a copper layer on the surface of the PCB board and the surface of the hole wall; S4: VCP electroplating, using VCP equipment to electroplate the PCB board to thicken the copper layer on the surface of the PCB board and the surface of the hole wall; S5: Resin plugging, filling the copper-plated holes with resin plugging oil, without adding oil-opening water to the resin plugging oil; S6: Ceramic grinding plate: After the resin plugging oil is solidified, the plate is ground using a PCB grinding machine with a ceramic roller to grind away the resin overflowing from the hole; S7: copper plating 2, performing a second copper plating process on the PCB board to form a copper layer on the plugging resin surface and thicken the copper layer on the surface of the PCB board; S8: electroplating the PCB board for the second time to thicken the copper layer on the plugging resin surface and the surface of the PCB board; S9: Drying the film, transferring the circuit pattern from the film to the surface of the PCB through lamination, exposure, and development; S10: Acid etching, etching an outer layer circuit on the PCB board using an acid solution; S11: Post-process.

[0007] The high-reliability POFV board manufacturing process according to the embodiment of the present invention has at least the following beneficial effects: It is understandable that the inventors learned through DOE testing that the main causes of blistering on the surface of POFV boards and the copper-covered delamination phenomenon on slices are the following three: first, the addition of open-oil water to the resin plugging oil leads to a composition imbalance, insufficient bonding between the copper and resin, and delamination when heated; second, resin residue at the hole mouth affects the subsequent copper deposition and electroplating effects; and third, insufficient copper coverage on the PCB board surface, especially the plugging resin surface, leads to insufficient stress in the copper layer, which is insufficient to overcome the expansion of the board and resin after heating, resulting in delamination or even cracking. Therefore, to address the above technical problems, the present application optimizes the process by using resin plugging oil without open-oil water for resin plugging; grinding the board with a PCB brush using ceramic rollers to clean up the resin that overflows from the holes; and through two copper deposition and electroplating processes, a uniform and highly adherent copper layer is formed, thereby effectively reducing the possibility of blistering and delamination in the POFV board and improving the yield rate.

[0008] According to some embodiments of the present invention, in step S1, the preceding process includes cutting, inner layer wet film, inner layer etching, inner layer AOI, lamination, and milling.

[0009] According to some embodiments of the present invention, in step S11, the post-process includes outer layer AOI, solder mask, character, surface treatment, gong board, electrical testing, final inspection, FQA, packaging and warehousing.

[0010] According to some embodiments of the present invention, in step S3, before the copper plating treatment, the PCB board is pre-neutralized using a mixture of hydrogen peroxide and sulfuric acid, where the concentration of the hydrogen peroxide is 1-3%, and the concentration of the sulfuric acid is 1-3%.

[0011] According to some embodiments of the present invention, the concentration of the hydrogen peroxide is 2%, and the concentration of the sulfuric acid is 2%.

[0012] According to some embodiments of the present invention, the concentration of the hydrogen peroxide is 3%, and the concentration of the sulfuric acid is 3%.

[0013] According to some embodiments of the present invention, in step S8, the thickness of the electroplated copper covering the resin surface of the plug hole is ≥12 μm.

[0014] According to some embodiments of the present invention, the thickness of the electroplated copper on the resin surface of the plug hole is 12 μm.

[0015] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 Flowchart of a high-reliability POFV board manufacturing process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0018] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, 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, they cannot be understood as limitations on the present invention.

[0019] In the description of the present invention, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0020] In the description of the present invention, unless otherwise explicitly defined, terms such as "set," "install," and "connect" should be interpreted broadly. Those skilled in the art can reasonably determine the specific meanings of these terms in the present invention based on the specific content of the technical solution. In the description of the present invention, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In the description of this specification, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0021] Reference Figure 1 According to the present invention, a high-reliability POFV board manufacturing process includes the following steps: S1: pre-process; S2: Drilling, drilling holes on the PCB board; S3: Copper deposition 1: copper deposition is performed on the PCB board to form a copper layer on the surface of the PCB board and the surface of the hole wall; S4: VCP electroplating, using VCP equipment to electroplate the PCB board to thicken the copper layer on the PCB board surface and the hole wall surface; S5: Resin plugging, fill the copper-plated holes with resin plugging oil, and do not add oil-opening water to the resin plugging oil; S6: Ceramic grinding plate. After the resin plugging oil is solidified, use a ceramic roller PCB grinding machine to grind the plate to clean the resin overflowing from the hole. S7: Copper deposition 2: The PCB is subjected to a second copper deposition process to form a copper layer on the plug-hole resin surface and thicken the copper layer on the surface of the PCB board; S8: Surface electroplating: The PCB is electroplated for the second time to thicken the copper layer on the plugging resin surface and the PCB surface; S9: Dry film, transfer the circuit pattern from the film to the PCB board through film lamination, exposure and development; S10: Acid etching, etching the outer layer circuit on the PCB board through acid solution; S11: Post-process.

[0022] It is understandable that the inventors learned through DOE tests that the main causes of blistering on the surface of POFV boards and delamination of copper coating on slices are as follows: First, the addition of open oil water to the resin plugging oil leads to composition imbalance, insufficient bonding between copper and resin, and delamination when heated. Secondly, because open oil water acts as a diluent to change the viscosity and fluidity of the resin, the use of resin containing open oil water in the resin plugging process may lead to the generation of more volatile substances during the curing process. These substances may form bubbles or voids during curing, causing blistering in subsequent processes. Second, there is residual resin at the hole mouth. If there is still residual resin at the hole mouth that has not been cleaned, this will not only affect the subsequent copper deposition and electroplating results, but may also cause stress during heat treatment processes (such as reflow soldering) due to the difference in thermal expansion coefficients between the resin and copper layer, thereby causing blistering or delamination. Third, there is insufficient copper coating on the board surface, especially on the plugging resin surface. If the copper coating is not thick or is uneven, the stress in the copper layer is insufficient to overcome the expansion of the board and resin after heating, resulting in delamination or even cracking.

[0023] Therefore, in order to solve the above technical problems, the present application optimizes the process by using resin plugging oil without adding oil water for resin plugging, ensuring that the resin is fully filled and free of bubbles; grinding the plate with a PCB brush machine using a ceramic roller to grind away the resin overflowing from the hole, and before the second copper deposition, ensuring that the hole mouth and the board surface are thoroughly cleaned to remove any possible resin residues and improve the quality of the surface treatment; performing the first copper deposition and electroplating treatment before resin plugging to ensure that a uniform and highly adhesive copper layer is formed on the surface of the PCB board and the surface of the hole wall. Since the copper layer on the board surface of the PCB board may be worn during grinding, the second copper deposition and electroplating treatment is performed after the ceramic grinding plate to ensure that a uniform and highly adhesive copper layer is formed on the surface of the PCB board and the plugging resin surface, thereby effectively reducing the possibility of bubbling and stratification of the POFV board and improving the yield.

[0024] Preferably, in some embodiments, in step S6, after the resin plugging oil is solidified, a PCB grinding machine with a ceramic roller is used to perform fine grinding on the plate at least three times to grind away the resin overflowing from the hole, and a brush or other tool is used to clean the residual copper powder on the plugging resin surface.

[0025] It is understandable that the inventors learned through DOE tests that the reason why the appearance of the POFV board is bubbling and the copper-covered stratification phenomenon appears on the slices is also due to the fact that the residual copper powder on the resin surface of the plugged holes after the ceramic grinding plate is not cleaned before the second copper deposition and degreasing. If there is copper powder remaining on the resin surface at the dense hole position after the ceramic grinding plate, and the concentration of the pre-neutralization solution of the copper deposition line is low, the copper powder remaining on the resin surface cannot be effectively removed. When passing through the degreasing cylinder of the copper deposition line, the residual copper powder affects the treatment effect of the resin surface; and when passing through the micro-etching cylinder after degreasing, the copper powder on the resin surface is micro-etched clean. The resin position where the copper powder is micro-etched clean cannot adsorb palladium ions in the activation cylinder because it has not been treated with the degreasing cylinder solution, which ultimately affects the copper deposition effect, resulting in poor bonding between the copper deposition layer and the resin, insufficient bonding between copper and resin after electroplating, and easy stratification when heated.

[0026] Therefore, in order to solve the above technical problems, in one embodiment of the present invention, in step S6, after grinding the PCB using a ceramic roller PCB grinding machine, a brush or other tool is used to clean the residual copper powder on the plugging resin surface.

[0027] Preferably, according to some embodiments of the present invention, in step S1, the preceding process includes cutting, inner layer wet film, inner layer etching, inner layer AOI, lamination and milling.

[0028] Among them, cutting: select a suitable substrate and cut it into the required size according to the design specifications; inner layer wet film: coat the inner copper foil with a photosensitive chemical resist (wet film) for subsequent circuit pattern transfer; inner layer etching: transfer the designed circuit pattern to the inner layer board through exposure and development processes, and then use chemical etching to remove the unprotected copper to form a circuit path; inner layer AOI: use automatic optical inspection equipment to check whether the inner layer circuit has short circuits, open circuits or other defects; lamination: combine the treated inner layer with prepreg materials, outer copper foil, etc., and bond them together through a high temperature and high pressure process to form a multi-layer board structure; milling burrs: remove excess edge material generated during the lamination process to ensure that the board edge is smooth.

[0029] Preferably, according to some embodiments of the present invention, in step S11, the post-process includes outer layer AOI, solder mask, characterization, surface treatment, gong plate, electrical testing, final inspection, FQA, packaging and warehousing.

[0030] Among them, outer layer AOI: automatic optical inspection of the outer layer circuit to ensure that the quality meets the standards; solder mask: apply a layer of solder mask ink, exposing only the part that needs to be soldered, protecting the circuit from environmental influences; characters: printing identification symbols and text on the board to facilitate assembly and maintenance; surface treatment: such as hot air leveling (HASL), chemical nickel / immersion gold (ENIG), etc., to improve welding performance and durability; gong board: cutting PCB boards according to the final product size requirements; electrical test: verify whether all connections are correct through electrical testing to ensure that there is no short circuit or open circuit; final inspection: comprehensive inspection of product quality, including appearance, size, electrical performance and other aspects; FQA: separately test the appearance, hole copper thickness, dielectric layer thickness, green oil thickness, inner layer copper thickness, etc. of the finished product to see if they meet customer requirements; packaging: according to the packaging method and packaging quantity required by the customer, the finished board is sealed and packaged, and desiccant and humidity card are placed, and then shipped; warehousing: after completing all production steps, the product is stored in the warehouse and waits for shipment.

[0031] Preferably, according to some embodiments of the present invention, in step S3, before the copper plating treatment, the PCB board is pre-neutralized using a mixture of hydrogen peroxide and sulfuric acid, where the concentration of hydrogen peroxide is 1-3%, and the concentration of sulfuric acid is 1-3%.

[0032] It is understood that pre-neutralization treatment with a mixture of hydrogen peroxide and sulfuric acid can effectively remove oxides and other impurities from the PCB surface, improving the effectiveness of subsequent copper plating. This pretreatment method not only cleans the board surface but also strengthens the adhesion between the copper layer and the substrate, ensuring a more uniform and robust copper deposition, thereby enhancing the overall reliability and conductivity of the circuit board. Furthermore, the inventors have demonstrated through experiments that a concentration range of hydrogen peroxide and sulfuric acid of 1-3% ensures sufficient cleaning power without excessive corrosion, thus optimizing the treatment effect.

[0033] Preferably, according to some embodiments of the present invention, the concentration of hydrogen peroxide is 2%, and the concentration of sulfuric acid is 2%.

[0034] Preferably, according to some embodiments of the present invention, the concentration of hydrogen peroxide is 2.5%, and the concentration of sulfuric acid is 2.5%.

[0035] Preferably, according to some embodiments of the present invention, the concentration of hydrogen peroxide is 3%, and the concentration of sulfuric acid is 3%.

[0036] It is understandable that the above concentration can effectively remove surface oxides and contaminants while avoiding unnecessary damage to the substrate. This ratio helps achieve the best surface preparation state, allowing the copper layer to adhere more tightly to the PCB during the copper deposition process, thereby improving yield and product quality.

[0037] Preferably, according to some embodiments of the present invention, in step S8, the thickness of the electroplated copper covering the resin surface of the plug hole is ≥12 μm.

[0038] Understandably, the inventors concluded through experimentation that requiring a minimum 12μm copper plating thickness on the resin surface of the plugged vias significantly enhances the mechanical strength and electrical performance of the copper layer, particularly in high-current-density applications. A sufficiently thick copper layer can better withstand thermal and mechanical stresses, reducing the risk of delamination and blistering, improving the durability and reliability of the final product while also meeting stringent quality standards.

[0039] Preferably, according to some embodiments of the present invention, the thickness of the electroplated copper on the resin surface of the plug hole is 12 μm.

[0040] Preferably, according to some embodiments of the present invention, the thickness of the electroplated copper on the resin surface of the plug hole is 13 μm.

[0041] Preferably, according to some embodiments of the present invention, the thickness of the electroplated copper on the resin surface of the plug hole is 15 μm.

[0042] As you can understand, the above copper thickness ensures the necessary mechanical strength and electrical performance while avoiding the additional cost and processing complexity associated with excessively thick copper layers. Precisely controlling copper thickness helps maintain consistent and predictable production, ensuring that each product meets the expected high quality standards for both mass production and high-end applications. The specific values selected above are based on actual testing results and long-term user feedback, aiming to provide the optimal cost-effectiveness.

[0043] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the scope of the present invention.

Claims

1. A high reliability POFV board manufacturing process, characterized in that: The following steps are involved: S1: pre-process; S2: Drilling, drilling holes on the PCB board; S3: copper plating 1, performing copper plating treatment on the PCB board to form a copper layer on the surface of the PCB board and the surface of the hole wall; S4: VCP electroplating, using VCP equipment to electroplate the PCB board to thicken the copper layer on the surface of the PCB board and the surface of the hole wall; S5: Resin plugging, filling the copper-plated holes with resin plugging oil, without adding oil-opening water to the resin plugging oil; S6: Ceramic grinding plate: After the resin plugging oil is solidified, the plate is ground using a PCB grinding machine with a ceramic roller to grind away the resin overflowing from the hole; S7: copper plating 2, performing a second copper plating process on the PCB board to form a copper layer on the plugging resin surface and thicken the copper layer on the surface of the PCB board; S8: electroplating the PCB board for the second time to thicken the copper layer on the plugging resin surface and the surface of the PCB board; S9: Drying the film, transferring the circuit pattern from the film to the surface of the PCB through lamination, exposure, and development; S10: Acid etching, etching an outer layer circuit on the PCB board using an acid solution; S11: Post-process.

2. The high reliability POFV board manufacturing process according to claim 1, characterized in that: In step S1, the preceding process includes cutting, inner layer wet film, inner layer etching, inner layer AOI, lamination and milling.

3. The high reliability POFV board manufacturing process according to claim 1, characterized in that: In step S11, the post-process includes outer layer AOI, solder mask, character, surface treatment, gong board, electrical testing, final inspection, FQA, packaging and warehousing.

4. The high reliability POFV board manufacturing process according to claim 1, characterized in that: In the step S3, before the copper plating treatment, the PCB board is pre-neutralized using a mixture of hydrogen peroxide and sulfuric acid, where the concentration of the hydrogen peroxide is 1-3%, and the concentration of the sulfuric acid is 1-3%.

5. The high reliability POFV board manufacturing process according to claim 4, characterized in that: The concentration of the hydrogen peroxide is 2%, and the concentration of the sulfuric acid is 2%.

6. The high-reliability POFV board manufacturing process according to claim 4, characterized in that: The concentration of the hydrogen peroxide is 3%, and the concentration of the sulfuric acid is 3%.

7. The high reliability POFV board manufacturing process according to claim 1, characterized in that: In the step S8, the thickness of the electroplated copper covering the resin surface of the plug hole is ≥12 μm.

8. The high-reliability POFV board manufacturing process according to claim 7, characterized in that: The thickness of the electroplated copper on the resin surface of the plug hole is 12 μm.

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