Brown oxidation method and substrate

Abstract

The invention discloses a browning method and a substrate, and the method comprises the steps: covering a protective film on a board surface in different regions before the board surface starts to be browned, enabling only non-browned regions with the same required browning strength to be exposed on the board surface, then selecting a browning liquid medicine according to the browning strength required by the non-browned regions, and carrying out the browning of the board surface through the browning liquid medicine, after each browning is completed, sequentially removing the protective film according to the browning strength required by each area covered with the protective film so as to expose a new non-browning area, and after each time of removal of the protective film, selecting a browning liquid medicine according to the browning strength required by the exposed new non-browning area, and browning the board surface again by using the browning liquid medicine until the browning of all areas of the board surface is completed. In this way, the areas are separately browned, the binding force of some areas after browning is guaranteed, meanwhile, the dielectric performance of other areas is not damaged, and the binding force and the dielectric performance are both considered on the same board.

Description

Technical Field

[0001] The present invention relates to the technical field of substrate manufacturing, and particularly relates to a browning method and a substrate. Background Art

[0002] With the upgrading of high-speed and high-frequency products, the number of layers, thickness, and dielectric properties of PCB manufacturing are continuously optimized. In order to improve the dielectric properties of products, the roughness of copper foil on copper-clad laminates continues to decrease, and mechanical properties such as browning peel strength continue to weaken. This results in delamination and blistering of multilayer boards during high-temperature thermal shock, seriously affecting product stability.

[0003] Therefore, how to balance the dielectric properties of products and the interlayer bonding force has become an urgent problem to be solved in substrate manufacturing. Summary of the Invention

[0004] Based on this, in view of the above technical problems, it is necessary to provide a browning method and a substrate to reduce the loss of dielectric properties while improving the bonding force of the board after browning.

[0005] In a first aspect, a browning method is provided. The method includes: covering a protective film on the surface of the substrate to be browned in a divided area, and exposing an un-browned area with the same required browning intensity; selecting a browning solution according to the required browning intensity of the un-browned area, and using the browning solution to brown the surface of the board; after each browning is completed, successively removing the protective film according to the required browning intensity of each area covered with the protective film to expose a new un-browned area; selecting a browning solution according to the required browning intensity of the new un-browned area, and using the browning solution to brown the surface of the board until the browning of all areas of the board surface is completed.

[0006] In an embodiment of the present application, the required browning intensity of the un-browned area is determined according to the required roughness and / or bonding force on the surface of the un-browned area.

[0007] In an embodiment of the present application, after selecting the browning solution according to the required browning intensity of the new un-browned area, it further includes: covering a protective film on the already browned area.

[0008] In an embodiment of the present application, the covering a protective film on the already browned area includes: determining whether the browning solution is used to reduce the surface roughness; if so, covering a protective film on the already browned area.

[0009] In an embodiment of the present application, the step of, after each browning is completed, successively removing the protective film according to the required browning intensity of each area covered with the protective film to expose a new un-browned area includes: after each browning is completed, successively removing the protective film from high to low according to the required browning intensity of each area to expose a new un-browned area.

[0010] In an embodiment of the present application, the substrate surface includes a drilling area, a wiring area, and a non-wiring area. A protective film is covered on the substrate surface to be browned in regions, and an un-browned area with the same required browning strength is exposed, including: covering the protective film on the drilling area and the wiring area, and exposing the non-wiring area as the un-browned area.

[0011] In an embodiment of the present application, after each browning is completed, the protective film is removed in sequence according to the required browning strength of each area covered with the protective film to expose a new un-browned area, including: after the browning of the non-wiring area is completed, removing the protective film of the wiring area; after the browning of the wiring area is completed, removing the protective film of the drilling area.

[0012] In an embodiment of the present application, the required roughness of the wiring area is less than that of the non-wiring area.

[0013] In an embodiment of the present application, the browning solution used in the wiring area is a silane coupling agent.

[0014] In a second aspect, a substrate is proposed. The substrate is subjected to surface browning according to the browning method described in any one of the embodiments of the first aspect above.

[0015] In any of the above-provided solutions, before starting to brown the surface, a protective film is first covered on the surface in regions so that only an un-browned area with the same required browning strength is exposed on the surface. Then, according to the required browning strength of the un-browned area, a browning solution is selected, and the surface is browned with the browning solution. After each browning is completed, then in sequence according to the required browning strength of each area covered with the protective film, the protective film is removed to expose a new un-browned area. After each removal of the protective film, again according to the required browning strength of the newly exposed un-browned area, a browning solution is selected, and the surface is browned again with the browning solution until the browning of all areas on the surface is completed. In this way, browning is carried out separately for areas with different required browning strengths, and when browning them, a browning solution is selected according to their required browning strength, so as to meet the requirements for the browning effect of different areas on the same substrate surface. Compared with the undifferentiated browning of the same substrate surface in the prior art, the present application can ensure the bonding strength of some areas after browning without damaging the dielectric properties of other areas, and achieve the balance of bonding strength and dielectric properties on the same substrate surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 Flow chart of the brownification method shown in an exemplary embodiment of the present application; Figure 2 Schematic diagram of the board surface after the protective film is covered shown in an exemplary embodiment of the present application; Figure 3 For an exemplary embodiment of the present application Figure 2 Schematic diagram of the board surface after the board surface shown is brownified; Figure 4 Schematic diagram of the board surface after the protective film in the wiring area is removed shown in an exemplary embodiment of the present application; Figure 5 For an exemplary embodiment of the present application Figure 4 Schematic diagram of the board surface after the board surface shown is brownified; Figure 6 Schematic diagram of the board surface after the protective film in the drilling area is removed shown in an embodiment of the present application; Figure 7 For an exemplary embodiment of the present application Figure 6 Schematic diagram of the board surface after the board surface shown is brownified. Detailed implementation manners

[0018] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0019] It should be understood that the embodiments described below represent the necessary information that enables those skilled in the art to implement the embodiments and illustrate the best mode of implementing the embodiments. After reading the following description with reference to the drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize the applications of these concepts that are not specifically mentioned herein. It should be understood that these concepts and applications fall within the scope of the present disclosure and the appended claims.

[0020] It should also be understood that terms such as "upper", "lower", "left", "right", "front", "rear", "bottom", "middle", "top", etc. may be used herein to describe various elements. The orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, these elements should not be limited by these terms.

[0021] Further understanding, when the terms "comprising" and "including" are used herein, they specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0022] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that the terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0023] The brownification method proposed in the embodiments of this application can be applied to the brownification process in the substrate manufacturing process to perform zonal brownification on the board surface to be brownified, meeting the requirements for the brownification effect in each area.

[0024] Figure 1 It is a flowchart of the brownification method shown in an exemplary embodiment of this application.

[0025] As Figure 1 shown, the brownification method may include the following steps: S101, covering a protective film on the board surface of the substrate to be brownified in zones, and exposing un-brownified areas with the same required brownification intensity.

[0026] In the brownification process of substrate manufacturing, for the board surface of the substrate that needs to be brownified, a protective film is covered on this board surface. For example, through the method of selective film covering, a removable protective film can be covered for different processing areas. After film covering, un-brownified areas with the same required brownification intensity are exposed on the board surface.

[0027] Exemplarily, if one board surface of the substrate includes a wiring area, a non-wiring area, and a drilling area, the following method can be used to perform film covering on this board surface: Cover the protective film on the wiring area and the drilling area, and do not cover the protective film on the non-wiring area, so that the non-wiring area is exposed as an un-brownified area. As Figure 2 shown, it is a schematic diagram of the board surface after protective film covering.

[0028] It should be noted that the un-brownified areas that need to be exposed after film covering on the board surface can be determined according to actual needs, and this application does not make any limitations.

[0029] S102, select a brownification chemical solution according to the required brownification intensity of the un-brownified areas, and use the brownification chemical solution to brownify the said board surface.

[0030] Select a brownification chemical solution according to the brownification intensity required for the un-brownified areas exposed in the above-mentioned step S101, and use this brownification chemical solution to brownify the board surface. Since only the un-brownified areas are exposed on the board surface and other areas are covered with protective films, when using the brownification chemical solution to brownify the board surface, the brownification chemical solution will only act on the un-brownified areas and will not brownify the areas covered with protective films.

[0031] After the brownification is completed, the un-brownified areas exposed before the brownification become brownified areas, while the areas covered with protective films remain un-brownified areas.

[0032] Among them, the brownification intensity can also be called the brownification degree. It is not difficult to understand that brownification forms a uniform brown oxide layer on the surface of the copper foil through chemical oxidation, and its functions can include: increasing the bonding force between the copper foil and the substrate, improving the interlayer bonding strength, improving the subsequent welding performance, and so on.

[0033] The brownification intensity can be understood as the thickness and tightness of this oxide layer, and is usually represented by surface roughness and bonding force.

[0034] In some embodiments, the brownification intensity required for the un-brownified areas can be determined according to the required surface roughness and / or bonding force of the un-brownified areas.

[0035] In one example, the brownification intensity that the brownification chemical solution can provide can be adjusted by adjusting the composition of the brownification chemical solution and the proportion of each component. For example, adjust the concentration of the persulfate / sulfuric acid system in the brownification chemical solution. Of course, the brownification intensity achieved by the brownification chemical solution on the board surface can also be adjusted by changing other process parameters. For example, adjust the reaction temperature of the brownification chemical solution, the treatment duration of the brownification chemical solution, and so on.

[0036] S103, after each brownification is completed, remove the protective films in sequence according to the brownification intensity required for each area covered with the protective film to expose new un-brownified areas.

[0037] After one brownification is completed, continue to remove the protective films in other areas on the board surface to expose new un-brownified areas with the same brownification intensity for the next brownification. Among them, the brownification intensity of the newly exposed un-brownified areas is the same each time brownification is performed.

[0038] For example, after the first brownification of the Figure 2 shown board surface, the un-wired area has undergone one brownification treatment, and this area has become the brownified area described in this application. Figure 3 For Figure 2 shown is a schematic diagram of the board surface after brownification. From Figure 3It can be seen that the wiring area and the drilling area on the board surface that are still covered with the protective film have not been browned yet. After the first brownization is completed, the protective film on the wiring area is removed, and the exposed wiring area is used as the non-browned area for the second brownization, as shown in Figure 4 is a schematic diagram of the board surface for removing the protective film on the wiring area. In addition, after the second brownization is completed, the protective film on the drilling area can be removed, and the exposed drilling area is used as the non-browned area for the third brownization.

[0039] S104. According to the brownization intensity required for the new non-browned area, select the brownization chemical solution, and use the brownization chemical solution to brown the board surface until the brownization of all areas of the board surface is completed.

[0040] After the treatment in step S103 above, before each brownization, a new non-browned area will be newly exposed, and the brownization intensities of the newly exposed non-browned areas are the same.

[0041] During each brownization, according to the brownization intensity required for the newly exposed non-browned area, select the brownization chemical solution, and use the brownization chemical solution selected for this non-browned area to brown the board surface. In this way, after each brownization treatment, at least one area can be browned. The process of selecting the brownization chemical solution according to the brownization intensity required for the new non-browned area and using the brownization chemical solution to brown the board surface in step S103 and step S104 is cyclically implemented until the brownization of all areas of the board surface is completed.

[0042] For example, after brownizing the board surface shown in Figure 4 , the browned board surface shown in Figure 5 can be obtained. Then, remove the protective film on the drilling area of the board surface; Figure 6 is a schematic diagram of the board surface for removing the protective film on the drilling area. Then, according to the brownization intensity required for the drilling area, select the brownization chemical solution, and brown the board surface shown in Figure 6 to obtain the browned board surface shown in Figure 7 , thus completing the brownization of all areas of the board surface.

[0043] In summary, for the brownification method proposed in this application, before starting the brownification of the board surface, a protective film is first covered in regions on the board surface, so that only the un-brownified regions with the same required brownification intensity are exposed on the board surface. Then, according to the brownification intensity required for the un-brownified regions, a brownification chemical solution is selected, and the board surface is brownified using this brownification chemical solution. After each brownification is completed, then in sequence according to the brownification intensity required for each region covered with the protective film, the protective film is removed to expose a new un-brownified region. After each removal of the protective film, again according to the brownification intensity required for the newly exposed un-brownified region, a brownification chemical solution is selected, and the board surface is brownified again using this brownification chemical solution until the brownification of all regions of the board surface is completed. In this way, brownification is carried out separately for regions with different required brownification intensities, and when brownifying them, a brownification chemical solution is selected according to the brownification intensity required for them, so as to meet the requirements for brownification effects in different regions on the same board surface. Compared with the undifferentiated brownification of the same board surface in the prior art, this application can ensure the bonding strength in some regions after brownification while not damaging the dielectric properties of other regions, achieving the balance between bonding strength and dielectric properties on the same board surface.

[0044] In some embodiments, after "selecting a brownification chemical solution according to the brownification intensity required for the new un-brownified region" in step S104 above and before "brownifying the board surface using the brownification chemical solution" in step S104, a protective film can also be covered on the brownified region of the board surface.

[0045] For example, for a board surface including a non-trace region, a trace region, and a drilling region, before the first brownification, the non-trace region is exposed, a brownification chemical solution is selected according to the brownification intensity required for the non-trace region, and the board surface is brownified using this brownification chemical solution. Before the second brownification, the protective film on the trace region is removed, a brownification chemical solution is selected according to the brownification intensity required for the trace region, and a protective film is covered on the already brownified non-trace region, and then the board surface is brownified using the brownification chemical solution selected for the trace region.

[0046] In this embodiment, before the next brownification, covering a protective film on the brownified region can prevent the brownification chemical solution used in the subsequent brownification process from acting on the brownified region, so as to better meet the differentiated requirements for brownification effects in each region on the same board surface.

[0047] It should be noted that the step of covering a protective film on the brownified region can be implemented at any time node before the next brownification. Covering a protective film on the brownified region after selecting the brownification chemical solution is only an exemplary implementation manner.

[0048] In some embodiments, after determining the brownification chemical solution for the next brownification, it can be determined whether the brownification chemical solution is used to reduce the surface roughness. If so, a protective film is covered on the brownified region.

[0049] For example, the brownification solution of the silane coupling agent type can reduce the surface roughness of the board. Traditional brownification solutions enhance the interlayer bonding force by forming a rough structure on the board surface, but this rough structure will cause dielectric loss during signal transmission. However, the brownification solution of the silane coupling agent type can enhance the interlayer bonding force based on its chemical properties while reducing the roughness. Therefore, the brownification solution of the silane coupling agent type is widely used in the production of substrates with strict requirements for signal integrity, such as high-frequency communication and HDI.

[0050] In this embodiment, if the brownification solution used for the next brownification can reduce the surface roughness, the brownified area on the current board is covered with a film, so as to ensure that this brownification solution will not affect the roughness of the brownified area and ensure the required brownification effect for each area.

[0051] In some embodiments, the required roughness of the wiring area on the board surface is less than that of the non-wiring area. Before brownification, a protective film can be covered on the wiring area and the drilling area, then the non-wiring area is exposed, and the brownification solution is selected according to the required brownification intensity of the non-wiring area to brownify the board surface. Then, the already brownified non-wiring area is covered with a protective film again, and the protective film on the wiring area is removed. Then, the board surface is brownified with a silane coupling agent. Since only the exposed wiring area on the board surface, the silane coupling agent only acts on the wiring area and will not affect the surface roughness of the non-wiring area and the drilling area.

[0052] In some embodiments, the step "after each brownification is completed, successively remove the protective film according to the required brownification intensity of each area covered with the protective film to expose the new non-brownified area" in the above step S103 may include the following steps: after each brownification is completed, remove the protective film successively from high to low according to the required brownification intensity of each area to expose the new non-brownified area.

[0053] For example, when covering the board surface with a film before brownification, only the area with the highest required brownification intensity is exposed, and all other areas are covered with a protective film. Then, after each brownification, the area with the highest required brownification intensity is selected from the non-brownified areas, and the protective film of this area is removed so that this area can be brownified in the next brownification process. In this way, even if the protective film is not re-covered on the already brownified area, the brownification solution with a smaller brownification intensity used in the subsequent brownification process will not overly affect the brownification effect of the already brownified area.

[0054] The present invention can be applied to brownify various materials on high-density circuit boards, especially the copper surface with local property requirements. The present invention brownifies different parts of the copper surface selectively with different solutions through multiple local brownification methods to meet the property requirements of each part of the copper surface. While improving the bonding force of the board after brownification, it reduces the impact on the dielectric properties of the board, ensuring the long-term reliability and signal integrity of the PCB.

[0055] The present application also provides a substrate, and the surface of the substrate is browned by any of the above-mentioned brownification methods.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A brownification method, characterized in that, The method includes: Cover the surface of the substrate to be browned with a protective film in regions, and expose the un-browned regions with the same required browning intensity. Select a browning chemical solution according to the required browning intensity of the un-browned regions, and use the browning chemical solution to brown the surface of the substrate. After each browning is completed, remove the protective film in sequence according to the required browning intensity of each region covered with the protective film, so as to expose the new un-browned regions. Select a browning chemical solution according to the required browning intensity of the new un-browned regions, and use the browning chemical solution to brown the surface of the substrate until the browning of all regions of the surface is completed.

2. The brownification method according to claim 1, characterized in that, The required browning intensity of the un-browned regions is determined according to the required roughness and / or adhesion on the surfaces of the un-browned regions.

3. The brownification method according to claim 1, wherein After selecting the browning chemical solution according to the required browning intensity of the new un-browned regions, it further includes: Cover the protective film on the already-browned regions.

4. The brownification method according to claim 3, wherein The covering of the protective film on the already-browned regions includes: Judge whether the browning chemical solution is used to reduce the surface roughness. If so, cover the protective film on the already-browned regions.

5. The brownification method according to claim 1, characterized in that, The removing of the protective film in sequence according to the required browning intensity of each region covered with the protective film after each browning is completed, so as to expose the new un-browned regions, includes: After each browning is completed, remove the protective film in descending order according to the required browning intensity of each region, so as to expose the new un-browned regions.

6. The brownification method according to claim 1, wherein The surface of the substrate includes a drilling area, a wiring area, and a non-wiring area. The covering of the protective film on the surface of the substrate to be browned in regions and exposing the un-browned regions with the same required browning intensity includes: Cover the protective film on the drilling area and the wiring area, and expose the non-wiring area as the un-browned region.

7. The brownification method according to claim 6, wherein, The removing of the protective film in sequence according to the required browning intensity of each region covered with the protective film after each browning is completed, so as to expose the new un-browned regions, includes: After the browning of the non-wiring region is completed, remove the protective film of the wiring area. After the browning of the wiring area is completed, remove the protective film of the drilling area.

8. The brownification method according to claim 6, characterized in that, The required roughness of the wiring area is less than the required roughness of the non-wiring area.

9. The brownification method according to claim 8, characterized in that, The browning chemical solution used in the wiring area is a silane coupling agent.

10. A substrate, characterized in that, The substrate is browned on its surface according to the browning method described in any one of the above claims 1-9.

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