Optical module circuit board based on back drilling lead wire technology

Abstract

The utility model discloses an optical module circuit board based on a back drilling lead wire technology, which is characterized in that a mode of drilling and breaking a gold-plated lead wire through shallow back drilling replaces a mode of etching the gold-plated lead wire, and then a back drilling hole is filled and leveled in a character fixed-point ink jet mode; the manufacturing process of the optical module circuit board based on the utility model comprises the following steps: 1, cutting, 2, inner layer manufacturing, 3, inner layer AOI, 4, pressing, 5, drilling, 6, copper deposition / electroplating, 7, outer layer manufacturing, 8, outer layer AOI, 9, solder mask, 10, character manufacturing, 11, chemical gold and gold plating, 12, back drilling, 13, character ink spraying, 14, forming, 15, testing and 16, final inspection, so that the problem that the cost is high when Dupont W250 dry films are used for three times is solved; and moreover, the production cost of chemical gold plating and nickel plating after resistance welding is saved by 30%, the number of stations passing through the gold-plated finger is small, finger scratches can be reduced by 40%, and the final inspection yield can be improved to 90% or above.

Description

Technical Field

[0001] This application relates to the technical field of optical module processing, and specifically relates to an optical module circuit board based on a back drilling lead process. Background Art

[0002] As the global demand for optical modules maintains a steady growth trend. According to the latest report on the global optical module market released by Lightcounting currently, the optical module market in 2020 was $8 billion, and institutions expect it to increase to $14.5 billion in 2026. The compound growth rate of the global optical module market from 2020 to 2026 is 10.4%. Currently, the domestic demand for optical modules accounts for a relatively small proportion. According to Yole's prediction, the demand for optical modules in China in 2022 was approximately 2.7 billion yuan, and it is expected to increase to 3.3 billion yuan in 2024. The compound growth rate of the Chinese optical module market from 2020 to 2024 is 10.6%, basically the same as the growth rate of the global optical module market.

[0003] An optical module is one of the key components in optical communication devices and is usually used for optoelectronic conversion devices. The main function of an optical module is to convert electrical signals and optical signals into each other to achieve high-speed data transmission. The design and manufacturing of an optical module circuit board need to particularly consider multiple aspects such as signal integrity, high-speed transmission, and thermal management.

[0004] The existing process flow of an optical module circuit board is as follows: 1. Cutting → 2. Inner layer → 3. Inner layer AOI → 4. Lamination → 5. Drilling → 6. Copper deposition / electroplating → 7. Outer layer → 8. Outer layer AOI → 9. Dry film image transfer (W250 dry film) → 10. Gold plating → 11. Stripping → 12. Dry film image transfer two (W250 dry film) → 13. Solder mask → 14. Lettering → 15. Dry film image transfer three (W250 dry film) → 16. Immersion gold → 17. Stripping → 18. Shaping → 19. Chamfering → 20. Testing → 21. Final inspection; In the original process flow, 3 times of DuPont W250 dry film image transfer are required for etching gold leads. The main purpose is to remove the unused gold leads to avoid introducing parasitic effects during high-speed signal transmission, which may cause signal reflection, attenuation, and impedance mismatch. However, the cost of 3 times of DuPont W250 dry film image transfer is relatively high, and the production cost cycle is relatively long. It is very difficult to control the quality such as scratches during the process, and it does not have an advantage in receiving orders in the market. The present invention can reduce the process, shorten the production cycle, and quickly meet customer needs. Summary of the Utility Model

[0005] Aiming at the deficiencies existing in the prior art, the purpose of this application is to provide an optical module circuit board based on a back drilling lead process to solve the problems raised in the above background art.

[0006] According to one aspect of the present application, an optical module circuit board based on a back-drilled lead process includes: a substrate, a back-drilled hole, a first copper layer, a second copper layer, and an inkjet layer. At least the first copper layer and the second copper layer are stacked in the substrate. The adjacent first copper layer and the second copper layer are not connected to each other, and an insulating layer is provided between the first copper layer and the second copper layer. A back-drilled hole is formed on one side surface of the substrate along its thickness direction. The back-drilled hole is a blind hole structure. The back-drilled hole drills through the first copper layer and is located above the second copper layer. The distance between the lower plane of the back-drilled hole and the lower plane of the first copper layer on one side thereof is L1. The distance between the lower plane of the back-drilled hole and the lower plane of the first copper layer on the other side thereof is L2. The distance between the lower plane of the back-drilled hole and the upper plane of the second copper layer is L3. The diameter size of the back-drilled hole is L4. The back-drilled hole is filled with an inkjet layer.

[0007] Preferably, the back-drilled hole is formed by shallow back-drilling with a CCD drill.

[0008] Preferably, the inkjet layer is formed by performing text fixed-point inkjet on the back-drilled hole and then baking.

[0009] Preferably, the upper surface of the inkjet layer is flush with the upper edge of the back-drilled hole.

[0010] Preferably, the ranges of L1 and L2 are 30μm - 40μm.

[0011] Preferably, the range of L3 is 40μm - 50μm.

[0012] Preferably, the range of L4 is 350μm - 450μm.

[0013] The advantages of the present application compared with the prior art are as follows: For an optical module circuit board based on a back-drilled lead process of the present application, the gold-plated lead (copper layer) is drilled off by shallow back-drilling, and then the back-drilled hole is filled and leveled by text fixed-point inkjet. Thus, the manufacturing process flow of the optical module circuit board based on the present application is: 1. Material cutting → 2. Inner layer → 3. Inner layer AOI → 4. Lamination → 5. Drilling → 6. Copper deposition / electroplating → 7. Outer layer → 8. Outer layer AOI → 9. Solder mask → 10. Lettering → 11. Immersion gold + gold plating → 12. Back-drilling → 13. Text inkjet → 14. Shaping → 15. Testing → 16. Final inspection. Thereby, the problem of high cost of using three times of DuPont W250 dry film is solved. And it also meets the requirement of gold plating on all four sides of the gold fingers. Moreover, the total nickel production cost of immersion gold + gold plating after solder mask is saved by 30%. After gold-plated fingers, the number of stations passed is less, the finger scratches can be reduced by 40%, and the final inspection yield can be increased to more than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure after back drilling of an optical module circuit board based on the back drilling and wire bonding process according to an embodiment of the present application.

[0015] Figure 2 It is a schematic diagram of the structure after inkjet printing of text on an optical module circuit board based on the back drilling and wire bonding process according to an embodiment of the present application.

[0016] Reference numerals: 1, substrate; 2, back drill hole; 3, first copper layer; 4, second copper layer; 5, inkjet layer. Detailed implementation manners

[0017] In order to make the content of the present application easier to be clearly understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the Figure 1 accompanying drawings, and the words "inner" and "outer" respectively refer to the directions towards or away from the geometric center of a specific component. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0018] Such as Figure 1 and Figure 2As shown in the figure, an optical module circuit board based on a back-drilled lead process includes: a substrate 1, a back-drilled hole 2, a first copper layer 3, a second copper layer 4, and an inkjet layer 5. The first copper layer 3 and the second copper layer 4 are stacked inside the substrate 1. The first copper layer 3 and the second copper layer 4 are formed by depositing a thin copper layer on the surface of the insulating substrate 1 through the electroless copper plating / electroplating process. The copper layer forms the basic conduction path of the circuit board and is used to achieve electrical connection between different components. Gold plating is performed on the surface of the copper layer to form a gold-plated lead. Since gold plating has high conductivity and strong corrosion resistance, it is used to enhance electrical performance and prevent oxidation, so it is used in key electrical contact areas, such as connector pads, via pins, and important wires in the signal path. The adjacent first copper layer 3 and the second copper layer 4 are not connected to each other, and an insulating layer is provided between the first copper layer 3 and the second copper layer 4. On one side surface of the substrate 1, a shallow back-drilling is performed along the thickness direction of the substrate 1 by a CCD drilling machine to form a back-drilled hole 2. The back-drilled hole 2 is a blind hole structure. The back-drilled hole 2 drills through and breaks the first copper layer 3 and is located above the second copper layer 4. The distance between the lower plane of the lower part of the back-drilled hole 2 and the lower plane of the first copper layer 3 on one side of it is controlled at about 35 μm. The distance between the lower plane of the lower part of the back-drilled hole 2 and the lower plane of the first copper layer 3 on the other side of it is also controlled at about 35 μm. The distance between the lower plane of the lower part of the back-drilled hole 2 and the upper plane of the second copper layer 4 is controlled at about 45 μm. The diameter size of the back-drilled hole 2 is controlled at about 400 μm to ensure that the back-drilled hole 2 can completely drill through and break the gold-plated lead formed by the first copper layer 3. Then, the back-drilled hole 2 is filled and leveled by the text fixed-point inkjet method, and baking is performed to form an inkjet layer 5 in the back-drilled hole 2.

[0019] In a specific implementation, first, use a CCD drilling machine, adjust its process parameters to a 0.4 mm flat head cutter for MASK point alignment, set the depth to 0.23 mm, and perform shallow back-drilling on the gold-plated lead at a specified point on the substrate 1 to drill it through. Then, use a gold plating washing line, adjust its process parameters to a line speed of 5 m / min and a pressure of 2 kg / cm 2 , and wash the substrate 1 after back-drilling. Then, use a printing device, and adjust its process parameters to:

[0020] Alignment method: CCD alignment;

[0021] Printing speed: 140 mm / second;

[0022] Printing method: flash printing;

[0023] Printing temperature: 48°;

[0024] UV energy: 6 mJ / cm 2 ;

[0025] Inkjet printing waveform: Pulse0: 3; 1; 6; 5 / Pulsel1: 2.7; 0.2; 5.4; 1.1;

[0026] Then, use the text fixed-point inkjet method to fill the back drill hole 2, and then use a vertical oven to bake it at a set temperature of 75°C for 35 minutes to complete.

[0027] In summary, for the optical module circuit board, by using the method of shallow back drilling to cut off the gold-plated leads (the first copper layer 3) instead of etching the gold-plated leads, and then using the text fixed-point inkjet method to fill the back drill hole 2, the manufacturing process flow of the optical module circuit board based on this application is as follows: 1. Material cutting → 2. Inner layer → 3. Inner layer AOI → 4. Lamination → 5. Drilling → 6. Copper deposition / electroplating → 7. Outer layer → 8. Outer layer AOI → 9. Solder mask → 10. Lettering → 11. Immersion gold + gold plating → 12. Back drilling → 13. Text inkjet → 14. Shaping → 15. Testing → 16. Final inspection. Thus, the problem of high cost of using DuPont W250 dry film three times is solved. It also satisfies the requirement of gold plating on all four sides of the gold fingers. And the total nickel production cost of immersion gold + gold plating after solder mask can be saved by 30%. After gold plating on the fingers, there are fewer stations passed, the finger scratches can be reduced by 40%, and the final inspection yield can be increased to more than 90%.

[0028] The above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, and are not intended to limit them. Although the embodiments of the present application have been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that without departing from the spirit and scope defined by the claims of the present application, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacement on some of the technical features.

Claims

1. A circuit board for an optical module based on a backdrilled lead process, comprising: A substrate (1), a back drill hole (2), a first copper layer (3), a second copper layer (4), and an inkjet layer (5), wherein at least the first copper layer (3) and the second copper layer (4) are stacked in the substrate (1), the adjacent first copper layer (3) and the second copper layer (4) are not connected to each other, and an insulating layer is provided between the first copper layer (3) and the second copper layer (4). A back drill hole (2) is formed on one side surface of the substrate (1) along its thickness direction. The back drill hole (2) is a blind hole structure. The back drill hole (2) breaks through the first copper layer (3) and is located above the second copper layer (4). The distance between the plane where the lower part of the back drill hole (2) is located and the plane where the lower part of the first copper layer (3) on one side thereof is located is L1. The distance between the plane where the lower part of the back drill hole (2) is located and the plane where the lower part of the first copper layer (3) on the other side thereof is located is L2. The distance between the plane where the lower part of the back drill hole (2) is located and the plane where the upper part of the second copper layer (4) is located is L3. The diameter size of the back drill hole (2) is L4. The back drill hole (2) is filled with the inkjet layer (5).

2. The optical module circuit board based on the back-drilled lead process according to claim 1, wherein The back drill hole (2) is formed by shallow back drilling with a CCD drill.

3. The optical module circuit board based on the backdrilled lead process according to claim 1, wherein The inkjet layer (5) is formed by performing text fixed-point inkjet on the back drill hole (2) and then baking it.

4. The optical module circuit board based on the back-drilled lead process according to claim 3, wherein, The upper surface of the inkjet layer (5) is flush with the upper edge of the back drill hole (2).

5. The optical module circuit board based on the back-drilled lead process according to claim 1, wherein The range of L1 and L2 is 30μm - 40μm.

6. The optical module circuit board based on the back-drilled lead process according to claim 1, wherein The range of L3 is 40μm - 50μm.

7. A light module circuit board based on a backdrill lead process according to claim 1, characterized in that, The range of L4 is 350μm - 450μm.

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