28-layer 8-step ultra HDI and fabrication method therefor

Abstract

The present invention relates to the technical field of the processing of printed circuit boards, and provides a 28-layer 8-step Ultra HDI and a fabrication method therefor. The method comprises: lamination, involving: stacking and laminating 12 sheets of RTF copper foil and 8 sheets of PP 1037; copper reduction and browning, involving: laminating a sheet of the RTF copper foil on each of the two sides, separating the two sheets of the RTF copper foil by using a sheet of PP, and reducing the thickness of copper on the outermost layer to 4-6 μm by means of copper reduction; laser drilling, involving: designing 6-8 inner laser drilling targets, wherein the diameter of a laser-drilled microvia is 70±5 μm; plasma degumming; electroless copper plating; microvia filling and electroplating; film pasting of a circuit, wherein a special dry film for MSAP is used; acid etching on a negative electrode sheet; and judgment, wherein if 16 sheets of the RTF copper foil have been laminated in the above steps, the process ends, and if not, the process starts from copper reduction and browning. The present solution uses techniques such as ultra-fine circuit fabrication, ultra-thin dielectric layer lamination, blind microvia fabrication and interlayer alignment, the trace width and spacing reach 30 μm / 20 μm, the thickness of a dielectric layer is 30 μm, and the diameter of blind microvias is 75 μm.

Description

A 28-layer 8-level Ultra HDI and its manufacturing method

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on March 12, 2024, with application number 202410276404.7 and invention name “A 28-layer 8-level Ultra HDI and its manufacturing method”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the technical field of printed circuit board processing, and in particular to a 28-layer 8-step Ultra HDI and a manufacturing method thereof. Background Art

[0003] Ultra High Density Interconnector, or Ultra HDI for short, refers to products with line widths and spacings less than 50μm, dielectric layer thickness less than 50μm, and blind via diameters less than 75μm. Ultra HDI has driven the development of HDI towards greater sophistication, enabling the rapid market adoption of smart mobile devices and smart wearables, and the rapid introduction of new products.

[0004] Conventional HDI product manufacturing presents the following challenges: The copper foil used has a smooth side and a roughened side. The roughened side is typically bonded to the resin, while the smooth side is used for dry film application. However, the smooth side has poor adhesion, making it difficult to adhere to the dry film and fabricate fine circuits. Furthermore, during drilling, the laser typically has only four internal targets, and alignment needs to be improved. This application improves the drilling and circuit fabrication processes, using specialized copper foil and dry film to produce a 28-layer, 8-step Ultra HDI product with a line width and spacing of 30μm / 20μm, a 30μm dielectric layer, and a 75μm blind via diameter. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present application provides a 28-layer 8-step Ultra HDI and its manufacturing method, with a line width and line spacing of 30μm / 20μm, a dielectric layer of 30μm, and a blind hole diameter of 75μm.

[0006] In order to achieve the purpose of this application, the following scheme is proposed:

[0007] A method for manufacturing a 28-layer 8-step Ultra HDI includes the following steps:

[0008] S1. Lamination: Provide 12 sheets of RTF copper foil with a surface roughness assessment parameter of Rz ≤ 2μm and a copper thickness of 12μm; provide 8 sheets of PP 1037; stack the RTF copper foil and PP 1037, from top to bottom, the 9th and 10th layers, the 11th and 12th layers, the 13th and 14th layers, the 15th and 16th layers, the 17th and 18th layers, and the 19th and 20th layers of RTF copper foil are separated by one sheet of PP 1037, and the 14th and 15th layers of RTF copper foil are separated by two sheets of PP 1037; press together, and the dielectric layer thickness after lamination shall not exceed 30μm;

[0009] S2, copper reduction and browning: A piece of RTF copper foil is laminated on the top and bottom of the laminated structure prepared in the previous step, and each is separated from the laminated structure by a piece of PP; the copper thickness of the outermost layer is reduced to 4μm-6μm;

[0010] S3. Laser drilling: 6-8 laser internal targets are designed; the laser aperture is 70μm±5μm, and is confirmed by automatic optical inspection (AOI);

[0011] S4, plasma degumming: remove surface residues after laser drilling;

[0012] S5, copper plating;

[0013] S6, hole filling plating: the copper thickness after electroplating ranges from 15μm to 20μm;

[0014] S7, Circuit film: The film uses MSAP special dry film with a thickness of 15μm and a resolution of 10μm / 10μm, which means that the minimum line width of the dry film reaches 10μm. The dry film adhesion test meets 10μm / 10μm, which means that after etching, the dry film will not fall off the circuit with a line width of 10μm;

[0015] S8, negative film acid etching: after etching, the blind hole diameter is 75μm, and the line width and line spacing are 30μm / 20μm;

[0016] S9, judgment: If the above steps have already laminated 16 sheets of RTF copper foil, then the process ends; if not, then continue to execute from S2;

[0017] In step S2 , the ninth layer of RTF copper foil is separated by a sheet of PP 1037; the twenty-first layer of RTF copper foil is separated by a sheet of PP 1037; and the remaining layers of RTF copper foil are separated by a sheet of PP 1017.

[0018] Furthermore, the film laminating parameters in step S7 are: roughening speed in pre-treatment 1.5 m / min, film laminating speed 1.5 m / min, film laminating temperature 110°C ± 5°C, and laminating pressure 1.5 Kg / cm2.

[0019] Furthermore, in step S7, the MSAP-specific dry film is selected from Asahi Kasei's ADH-158 model.

[0020] Furthermore, in step S8, the exposure machine used in the etching process is a Core MAS 8.

[0021] Furthermore, in step S8, the outer layer circuit exposure uses the laser inner target as the alignment target hole for segmented exposure: the PE value and the JE value are both set to 10 μm.

[0022] Furthermore, the size of the blind via is consistent with the size of the pad.

[0023] A 28-layer 8-step Ultra HDI is manufactured using the 28-layer 8-step Ultra HDI manufacturing method, comprising 28 sheets of RTF copper foil, 14 sheets of PP 1017, and 10 sheets of PP 1037 laminated together;

[0024] From top to bottom, the 1st to the 8th layers of RTF copper foil are separated by a sheet of PP 1017; the 8th to the 10th layers of RTF copper foil are separated by a sheet of PP 1037 respectively, the 11th and 12th layers, the 13th and 14th layers, the 15th and 16th layers, the 17th and 18th layers, the 19th and 20th layers, and the 20th and 21st layers are separated by a sheet of PP 1037, and the 14th and 15th layers are separated by two sheets of PP 1037; the 21st to the 28th layers of RTF copper foil are separated by a sheet of PP 1017.

[0025] The beneficial effects of this application are:

[0026] 1. Using technologies such as ultra-fine circuit production, ultra-thin dielectric layer lamination, micro blind hole production, and inter-layer alignment, 28-layer 8-step Ultra HDI products can be produced.

[0027] 2. Regarding the production of ultra-fine circuits: a special RTF copper foil is used, and both sides are roughened. The surface roughness evaluation parameters are small, and better etching effects can be obtained during subsequent etching. When reducing copper browning, the thickness of the outermost layer of copper is reduced to 4μm-6μm, and the substrate will not be leaked. After subsequent hole filling electroplating, it can also meet the circuit requirements. The use of a special MSAP dry film and the combination of semi-additive dry film and negative acid etching is conducive to the production of fine circuits.

[0028] 3. Regarding blind hole production and alignment: the size of the blind hole is consistent with the size of the pad, which simplifies the blind hole processing technology; when etching, 6-8 laser inner targets are used as alignment target holes for outer layer circuit exposure, which can improve alignment; after etching, the alignment between the blind hole and the circuit pad is ≤5μm.

[0029] 4. Beneficial effects of ultra-fine lines on circuit boards and their performance: (1) Miniaturization and lightweighting: Due to finer lines, the distance between components is greatly reduced, which allows the size of the circuit board to be significantly reduced while reducing the overall weight, making it suitable for use in portable and wearable devices; (2) Improved integration: Higher wiring density allows more electronic components to be placed in a limited space, thereby improving the integration of the circuit board and enabling the design of more complex systems; (3) Enhanced signal integrity: Fine line design helps reduce loss and delay during signal transmission, improves signal integrity and system timing performance, and supports higher frequency components and faster data transmission rates, such as in 5G communications and high-speed memory interfaces.

[0030] 5. The beneficial effects of ultra-thin dielectric layer on circuit boards and their performance: The dielectric layer refers to the layer used as an insulating isolation material between adjacent conductive layers. The ultra-thin dielectric layer can shorten the transmission time of signals between different layers. For high-speed signals, it means lower signal delay and improved signal transmission speed.

[0031] 6. The beneficial effects of tiny blind vias on circuit boards and their performance: they greatly save space, enhance the three-dimensional wiring capabilities of circuit boards, reduce interference, and improve signal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 shows a schematic diagram of a blind hole design in the prior art;

[0033] FIG2 shows a schematic diagram of a blind hole design in this embodiment;

[0034] FIG3 shows a schematic diagram of the design of the laser internal target;

[0035] FIG4 shows a schematic diagram of a 12-layer copper foil laminated structure;

[0036] FIG5 shows a schematic diagram of a 28-layer copper foil structure. DETAILED DESCRIPTION

[0037] Example 1

[0038] This embodiment provides a method for manufacturing a 28-layer 8-step Ultra HDI, including the following steps:

[0039] S1. Lamination: As shown in Figure 4, 12 sheets of copper foil are provided. The copper foil uses a special RTF copper foil with a copper thickness of 12μm and a surface roughness assessment parameter of Rz≤2μm. Because both sides of the RTF copper foil are roughened and the surface roughness assessment parameter of the RTF copper foil is small, better etching effects can be obtained during subsequent etching. 8 sheets of PP 1037 are provided. PP stands for semi-cured sheet in Chinese. The RTF copper foil and PP 1037 are stacked. Because Ultra HDI has a total of 28 layers, the 12 sheets of RTF copper foil laminated in this lamination step correspond to the 9th to 20th layers of the 28 layers. From top to bottom, the 9th and 10th layers, the 11th and 12th layers, the 13th and 14th layers, the 15th and 16th layers, the 17th and 18th layers, the 19th and 20th layers, and the 20th and 21st layers of RTF copper foil all use one sheet of PP. The 14th and 15th layers are separated by two sheets of PP 1037; the dielectric layer is laminated, and the thickness of the dielectric layer after lamination is 30μm.

[0040] S2. Copper reduction and browning: As shown in FIG5 , a piece of RTF copper foil is stacked on the top and bottom of the laminated structure obtained in the previous step, and each is separated from the laminated structure by a piece of PP. RTF copper foil is usually used in communication products to eliminate the skin effect and is not often used in the copper reduction and browning process. Then, the copper thickness of the outermost layer is reduced to 4μm-6μm, with a median of 5μm. The existing technology generally reduces the copper to 6μm-8μm. Through experiments in this embodiment, it was found that too thin copper thickness is easy to leak through the substrate, while too thick copper thickness cannot meet the circuit requirements after subsequent hole filling electroplating.

[0041] S3. Laser drilling: A Mitsubishi laser machine is used. The existing technology generally designs four laser internal targets. In order to increase the alignment, 6-8 laser internal targets are designed here, as shown in Figure 3; the laser aperture is 70μm±5μm, which is confirmed by automatic optical inspection (AOI).

[0042] S4. Plasma degumming: Remove surface residues after laser drilling. Plasma degumming is an existing technology and will not be elaborated here.

[0043] S5. Copper deposition: This is an existing technology and will not be elaborated here.

[0044] S6, hole filling electroplating: the copper thickness increases by 12μm after electroplating. In this step, the copper thickness should be controlled within the range of 15μm-20μm, and the electroplating range should be controlled within ±1.5μm.

[0045] S7. Circuit film: The film uses MSAP special dry film, selected from Asahi Kasei's ADH-158 model, with a dry film thickness of 15μm. The dry film adhesion test meets 10μm / 10μm and the resolution meets 10μm / 10μm.

[0046] Film laminating parameters: roughening speed in pre-treatment 1.5m / min, film laminating speed 1.5m / min, film laminating temperature 110℃±5℃, film pressing pressure 1.5Kg / cm2.

[0047] S8, Negative Acid Etching: The resulting blind vias have a diameter of 75μm and a line width and spacing of 30μm / 20μm. In this step, the exposure machine used was a Core Chi MAS 8. The outer layer circuit exposure used a laser internal target as the alignment target for segmented exposure. Both the PE and JE values ​​were set to 10μm. PE stands for Pitch Error, and JE stands for Jogging Error. The smaller the JE value, the more precise the circuit.

[0048] The MSAP special dry film is a semi-additive dry film. This embodiment combines the semi-additive dry film with negative acid etching, which is beneficial to the production of fine circuits.

[0049] S9, judgment: If the above steps have already stacked 16 sheets of RTF copper foil, including 8 sheets on the top and 8 sheets on the bottom, then the production process ends; if not, continue to execute from S2.

[0050] It should be noted that in step S2, the 9th layer of RTF copper foil is separated from the 8th layer by a sheet of PP 1037; the 21st layer of RTF copper foil is separated from the 20th layer by a sheet of PP 1037; and the remaining layers of RTF copper foil are separated by a sheet of PP 1017.

[0051] Regarding blind via fabrication, as shown in FIG1 , the size of the blind via designed in the prior art is smaller than the pad, and the hole ring size of the blind via is B / 2-A / 2. As shown in FIG2 , the size of the blind via designed in this embodiment is consistent with the pad size, simplifying the blind via fabrication process. During etching, the outer layer circuit exposure uses a laser inner target as the alignment target hole. After etching, the alignment degree between the blind via and the circuit pad is ≤5μm.

[0052] In summary, by adopting technologies such as ultra-fine circuit production, ultra-thin dielectric layer lamination, tiny blind hole production, and interlayer alignment, it is possible to produce 28-layer 8-step Ultra HDI products with a line width and line spacing of 30μm / 20μm, a dielectric layer of 30μm, and a blind hole diameter of 75μm.

[0053] Example 2

[0054] This embodiment provides a 28-layer 8-step Ultra HDI, which is manufactured using the manufacturing method of Example 1. The Ultra HDI structure is shown in Figures 4 and 5, including 28 stacked RTF copper foils, 14 PP 1017 sheets, and 10 PP 1037 sheets.

[0055] From top to bottom, the 1st to the 8th layers of RTF copper foil are separated by a sheet of PP 1017; the 8th to the 10th layers of RTF copper foil are separated by a sheet of PP 1037 respectively, the 11th and 12th layers, the 13th and 14th layers, the 15th and 16th layers, the 17th and 18th layers, the 19th and 20th layers, and the 20th and 21st layers are separated by a sheet of PP 1037, and the 14th and 15th layers are separated by two sheets of PP 1037; the 21st to the 28th layers of RTF copper foil are separated by a sheet of PP 1017.

[0056] The above embodiments are only used to illustrate the technical ideas and features of the present application and are not intended to be exclusive or limit the present application. It should be understood by those skilled in the art that various changes or equivalent replacements made to the present application without departing from the scope of the present application are within the scope of protection of the present application.

Claims

1. A 28-layer 8-step Ultra HDI manufacturing method, characterized in that: The following steps are involved: S1. Lamination: Provide 12 sheets of RTF copper foil with a surface roughness assessment parameter of Rz ≤ 2μm and a copper thickness of 12μm; provide 8 sheets of PP 1037; stack the RTF copper foil and PP 1037, from top to bottom, the 9th and 10th layers, the 11th and 12th layers, the 13th and 14th layers, the 15th and 16th layers, the 17th and 18th layers, and the 19th and 20th layers of RTF copper foil are separated by one sheet of PP 1037, and the 14th and 15th layers of RTF copper foil are separated by two sheets of PP 1037; press together, and the dielectric layer thickness after lamination shall not exceed 30μm; S2, copper reduction and browning: a piece of RTF copper foil is stacked on the top and bottom of the laminated structure prepared in the previous step, and each is separated from the laminated structure by a piece of PP; the copper thickness of the outermost layer is reduced to 4μm-6μm; S3. Laser drilling: 6-8 laser internal targets are designed; the laser aperture is 70μm±5μm, confirmed by automatic optical inspection; S4, plasma degumming: remove surface residues after laser drilling; S5, copper plating; S6, hole filling plating: the copper thickness after electroplating ranges from 15μm to 20μm; S7, Circuit film: The film is made of MSAP special dry film with a thickness of 15μm. The dry film adhesion test meets 10μm / 10μm and the resolution meets 10μm / 10μm. S8, negative film acid etching: after etching, the blind hole diameter is 75μm, and the line width and line spacing are 30μm / 20μm; S9, judgment: If the above steps have already laminated 16 sheets of RTF copper foil, then the process ends; if not, then continue to execute from S2; In step S2 , the ninth layer of RTF copper foil is separated by a sheet of PP 1037; the twenty-first layer of RTF copper foil is separated by a sheet of PP 1037; and the remaining layers of RTF copper foil are separated by a sheet of PP 1017.

2. The 28-layer 8-step Ultra HDI manufacturing method according to claim 1, characterized in that: The film laminating parameters in step S7 are: roughening speed in pre-treatment 1.5 m / min, film laminating speed 1.5 m / min, film laminating temperature 110°C ± 5°C, and laminating pressure 1.5 Kg / cm2.

3. The 28-layer 8-step Ultra HDI manufacturing method according to claim 1, characterized in that: In step S7, the MSAP-specific dry film is selected from Asahi Kasei's ADH-158 model.

4. The method for manufacturing a 28-layer 8-step Ultra HDI according to claim 1, wherein: In step S8, the exposure machine used in the etching process is a Core MAS 8.

5. The method for manufacturing a 28-layer 8-step Ultra HDI according to claim 4, wherein: In step S8 , the outer layer circuit exposure uses the laser inner target as the alignment target hole for segmented exposure: the PE value and the JE value are both set to 10 μm.

6. The method for manufacturing a 28-layer 8-step Ultra HDI according to claim 1, wherein: The size of the blind hole is consistent with the size of the pad.

7. A 28-layer 8-step Ultra HDI, characterized by: The 28-layer 8-step Ultra HDI manufacturing method according to any one of claims 1 to 5 is adopted, comprising 28 sheets of RTF copper foil, 14 sheets of PP 1017 and 10 sheets of PP 1037 laminated together; From top to bottom, the 1st to the 8th layers of RTF copper foil are separated by a sheet of PP 1017; the 8th to the 10th layers of RTF copper foil are separated by a sheet of PP 1037 respectively, the 11th and 12th layers, the 13th and 14th layers, the 15th and 16th layers, the 17th and 18th layers, the 19th and 20th layers, and the 20th and 21st layers are separated by a sheet of PP 1037, and the 14th and 15th layers are separated by two sheets of PP 1037; the 21st to the 28th layers of RTF copper foil are separated by a sheet of PP 1017.

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