High-stability fine copper circuit and preparation method thereof

Abstract

The application discloses a high-stability fine copper circuit and a preparation method thereof, and the preparation method comprises the following steps: performing photoetching on a fine copper circuit base material to obtain a base material with a curved structure on the surface; immersing the base material with the curved structure on the surface in a developer solution containing a chemical plating catalyst to perform first treatment, taking out and drying after the exposed area is completely covered with the chemical plating catalyst, and then immersing the base material in a copper plating solution to perform second treatment, so as to obtain the high-stability fine copper circuit. Through preparation of the fine copper circuit base material with the curved structure, the contact points of the base material and copper are increased during copper plating, the surface bonding force of copper and the fine copper circuit base material is improved, the service life of the fine copper circuit is prolonged, and continuous and efficient industrial production can be realized.

Description

Technical Field

[0001] This invention belongs to the field of circuit board technology, specifically relating to a high-stability fine copper circuit and its preparation method. Background Technology

[0002] As electronic devices become increasingly lightweight and highly integrated, higher demands are placed on the precision manufacturing of printed circuit boards (PCBs). Copper traces, as the core conductive layer of a PCB, directly affect the reliability and lifespan of the circuit due to the stability of their bonding with the substrate. However, in traditional chemical copper plating processes, insufficient interfacial bonding between copper and organic substrates (such as polyimide and epoxy resin) can easily lead to detachment, resulting in open or short circuits.

[0003] In existing technologies, methods to improve the adhesion between copper and substrate mainly include mechanical roughening, chemical etching, and plasma treatment. For example, etching the surface of polyimide with KOH / EDTA solution can form micron-sized pits, increasing the peel strength to 1.2 N / mm. However, this method damages the mechanical properties of the substrate (elastic modulus decreases by about 15%). In addition, plasma treatment requires a vacuum environment, which is costly and difficult to implement in continuous production.

[0004] Therefore, developing a method for fabricating highly stable copper circuits that does not require chemical etching and is suitable for industrial production remains a pressing technical challenge in this field. Summary of the Invention

[0005] To address the problems mentioned in the background section, the present invention aims to provide a highly stable fine copper circuit and its fabrication method. The present invention achieves precise control of the grating size on the substrate surface by using photomasks with different linewidths and spacings to alter the period of the bending structure on the substrate surface. Furthermore, the height of the bending structure is changed by varying the exposure time, exposure intensity, and development time. The micro-nano structure on the substrate surface increases the contact points between the substrate surface and copper, improving the adhesion between copper and the fine copper circuit substrate surface during copper plating. This solves the problems of open circuits and short circuits caused by copper circuit instability, extends the service life of the fine copper circuit, enables continuous and efficient industrial production, and is cost-effective.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a method for preparing highly stable fine copper circuits, comprising the following steps:

[0007] (1) Photolithography is performed on a fine copper circuit substrate to obtain a substrate with a curved surface structure;

[0008] (2) The substrate with a curved structure on the surface in step (1) is immersed in a developer solution containing a chemical plating catalyst for the first treatment. After the exposed area is completely covered by the chemical plating catalyst, it is taken out and dried. Then it is immersed in a copper plating solution for the second treatment to obtain a high-stability fine copper circuit.

[0009] Further, the fine copper circuit substrate mentioned in step (1) is selected from one of polyimide (PI), polyester (PET), polytetrafluoroethylene (PTFE), epoxy resin, and phenolic resin.

[0010] Furthermore, the polyimide includes PMDA-ODA type polyimide, photosensitive polyimide (PSPI), and BPDA-PPD polyimide.

[0011] Further, the photolithography in step (1) is to expose the fine copper circuit substrate surface with a mask having a set line width and line spacing using a parallel light source;

[0012] Preferably, the light source is an ultraviolet lamp with a wavelength of 365nm-405nm;

[0013] Preferably, the voltage of the light source is 1V-10V;

[0014] Preferably, the exposure time is 5s-200s.

[0015] Further, the line width of the bending structure in step (1) is 1μm-25μm, the line spacing of the bending structure in step (1) is 1μm-25μm, and the period of the bending structure in step (1) is 2μm-50μm.

[0016] Changing the period of the curved structure is achieved by altering the photomask: a photomask is a tool used in microelectronics manufacturing to form patterns and structures. This invention uses a pre-defined photomask placed on an exposure machine to photolithographically etch a curved structure, i.e., a grating, onto the surface of a fine copper circuit substrate. By adjusting the line spacing and linewidth parameters of the photomask, the period of the grating etched onto the surface of the fine copper circuit substrate is controlled, and the period of the grating etched onto the surface of the fine copper circuit substrate is equal to the designed line spacing of the photomask plus the linewidth of the photomask.

[0017] Furthermore, the components of the developer solution containing the chemical plating catalyst in step (2) include silver nitrate, ammonia, and deionized water;

[0018] Preferably, the ratio of silver nitrate, ammonia, and deionized water is (0.5g-10g):(20mL-400mL):(20mL-450mL).

[0019] Furthermore, the time for the first processing in step (2) is 10s-100s.

[0020] Furthermore, in step (2), the height of the curved structure after the first processing is 5nm-200nm.

[0021] Further, the components of the copper plating solution in step (2) include copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol 20000, potassium ferrocyanide, 2,2-bipyridine, sodium hydroxide, methanol, and deionized water.

[0022] Preferably, the ratio of copper sulfate pentahydrate (CuSO4·5H2O), ethylenediaminetetraacetic acid (EDTA), potassium sodium tartrate, polyethylene glycol 20000, potassium ferrocyanide, 2,2-bipyridine, sodium hydroxide, methanol, and deionized iron is 24g:21g:10g:1g:70mg:8mg:16g:10mL:1L.

[0023] Furthermore, the second treatment involves bubbling for 30-90 minutes using a bubble machine.

[0024] After the first treatment, copper is plated. The chemical plating catalyst can catalyze the bonding between the substrate and copper, improving the copper plating effect. During the copper plating process, copper seeds can be plated not only in the exposed areas (surface curved structure) but also in the non-exposed areas. This can effectively control the copper deposition in the non-exposed areas, avoiding uncontrollable copper deposition caused by incomplete contact between the copper in the non-exposed areas of the copper circuit and the circuit board, thus preventing short circuits.

[0025] On the other hand, the present invention provides a high-stability fine copper circuit, which is prepared by any of the preparation methods described above.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention, while employing existing electroless copper plating technology, utilizes the ultraviolet photosensitive properties of the substrate used to prepare highly stable fine copper circuits. By photolithography using a mask, the intermolecular forces are altered, and the periodic controllable construction of curved structures is achieved through localized volume contraction or expansion of the substrate. This increases the contact area between copper and the substrate surface during electroless copper plating, increasing the number of bonding sites and improving the adhesion between the copper and the substrate surface. This enhances the stability of the copper-substrate bond, prevents copper detachment, and significantly improves the adhesion strength compared to existing technologies, with a low rate of adhesion degradation after long-term aging. Furthermore, by altering the linewidth and spacing parameters of the mask, this invention constructs curved structures with different periods on the substrate surface, creating a substrate with curved structures. This not only solves the problem of reduced adhesion between Cu and the substrate surface during copper plating due to the substrate and Cu being different phases, but also achieves accurate and controllable construction of curved structures with different periods on the substrate surface, greatly improving the service life and stability of the fine copper circuits on the substrate surface. In summary, the preparation method provided by this invention can control the bending structure of the substrate surface, improve the stability of fine copper lines on the substrate surface, and be used for the industrial production of high-stability fine electronic circuit boards. Furthermore, the preparation method provided by this invention eliminates the need for chemical etching steps (such as KOH / EDTA treatment), reducing production energy consumption and avoiding material mechanical loss. Attached Figure Description

[0028] Figure 1 This is a side view of the curved structure obtained by photolithography using a photomask.

[0029] Figure 2 A top view schematic diagram of a curved structure obtained by photolithography using a photomask.

[0030] Figure 3 An optical microscope image of the high-stability fine copper circuit prepared in Example 1 of this invention;

[0031] Figure 4 This is a scanning electron microscope image of the high-stability fine copper circuit prepared in Example 1 of the present invention;

[0032] Figure 5 This is a scanning electron microscope image of the high-stability fine copper circuit prepared in Example 2 of the present invention;

[0033] Figure 6 This is a physical image of the high-stability fine copper circuit prepared in Example 3 of the present invention;

[0034] Figure 7 An optical microscope image of the highly stable fine copper circuit prepared in Example 3 of this invention;

[0035] Figure 8This is a scanning electron microscope image of the high-stability fine copper circuit prepared in Example 4 of the present invention. Detailed Implementation

[0036] To better understand the content of this invention, the following detailed description is provided in conjunction with specific implementation methods. However, the scope of protection of this invention is not limited to the following embodiments.

[0037] A side view diagram of the curved structure obtained by photolithography using a photomask is shown below. Figure 1 As shown, a top view of the curved structure is as follows: Figure 2 As shown. By using photomasks with different line widths and spacings, the period of the curved structure on the substrate surface can be changed, and the height of the curved structure can be changed by altering the exposure time, exposure intensity, and development time.

[0038] Example 1

[0039] The fabrication of highly stable, fine copper circuits includes the following steps:

[0040] (1) A mask with a line width of 1 μm and a line spacing of 1.5 μm was selected. The fine copper circuit substrate was selected as PMDA-ODA type polyimide based on pyromellitic dianhydride and 4,4'-diaminodiphenyl ether. The PMDA-ODA type polyimide film with a curved surface was obtained by exposing it on the surface of the PMDA-ODA type polyimide film using an exposure machine with a mask. The exposure light source was a 405nm ultraviolet lamp with a voltage of 10V and an exposure time of 30s.

[0041] (2) The PMDA-ODA type polyimide film with a curved surface in (1) is immersed in a developer solution containing a chemical plating catalyst for 40s, then taken out and air-dried in a natural environment, and then immersed in a copper plating solution and bubbled for 30 minutes to obtain a high-stability fine copper circuit.

[0042] The preparation of the developer solution containing the electroless plating catalyst is as follows: 0.5g of silver nitrate, 20mL of ammonia water and 20mL of deionized water are mixed evenly to prepare the developer solution containing the electroless plating catalyst.

[0043] Preparation of copper plating solution: Weigh 24g CuSO4·5H2O, 21g EDTA, 10g potassium sodium tartrate, 1g polyethylene glycol (20000), 70mg potassium ferrocyanide, 8mg 2,2-bipyridine, 16g NaOH and 10mL methanol, and add them to a 2L conical flask; add 1L of deionized water to the flask, stir thoroughly until completely dissolved, and the copper plating solution is obtained.

[0044] The high-stability fine copper circuit prepared in Example 1 was observed under an optical microscope, and the results are as follows: Figure 3 As shown. From Figure 3 As can be seen, there is a stable distribution of copper lines on the substrate.

[0045] The high-stability fine copper circuit prepared in Example 1 was scanned using a scanning electron microscope, and the results are as follows: Figure 4 As shown. From Figure 4 As can be seen, the linewidth of the curved structure is 1 μm, the line spacing is 1.5 μm, and the amplitude (height) is 61.8 nm.

[0046] Example 2

[0047] The fabrication of highly stable, fine copper circuits includes the following steps:

[0048] (1) Select a mask with a line width of 7μm and a line spacing of 3μm. Select epoxy resin as the fine copper circuit substrate. Use an exposure machine with a mask to expose the epoxy resin substrate to obtain an epoxy resin substrate with a curved surface. The exposure light source is a 365nm ultraviolet lamp with a voltage of 8V and an exposure time of 10s.

[0049] (2) Immerse the epoxy resin substrate with a curved surface in (1) in a developer solution containing a chemical plating catalyst for 10 seconds, then take it out and let it air dry in a natural environment, then immerse it in a copper plating solution and bubble it for 60 minutes using a bubble machine to obtain a high-stability fine copper circuit.

[0050] The preparation of the developer solution containing the electroless plating catalyst is as follows: 0.5g of silver nitrate, 20mL of ammonia water and 20mL of deionized water are mixed evenly to prepare the developer solution containing the electroless plating catalyst.

[0051] Preparation of copper plating solution: Weigh 24g CuSO4·5H2O, 21g EDTA, 10g potassium sodium tartrate, 1g polyethylene glycol (20000), 70mg potassium ferrocyanide, 8mg 2,2-bipyridine, 16g NaOH and 10mL methanol, and add them to a 2L conical flask; add 1L of deionized water to the flask, stir thoroughly until completely dissolved, and the copper plating solution is obtained.

[0052] The high-stability fine copper circuit prepared in Example 2 was scanned using a scanning electron microscope, and the results are as follows: Figure 5 As shown. From Figure 5 As can be seen, the linewidth of the curved structure is 7μm, the line spacing is 3μm, and the amplitude (height) is 31.4nm.

[0053] Example 3

[0054] The fabrication of highly stable, fine copper circuits includes the following steps:

[0055] (1) Select a mask with a line width of 9μm and a line spacing of 5μm. Select polyester as the fine copper circuit substrate. Use an exposure machine with a mask to expose the polyester substrate to obtain a polyester substrate with a curved surface. The exposure light source is a 405nm ultraviolet lamp with a voltage of 10V and an exposure time of 50s.

[0056] (2) The polyester substrate with a curved surface in (1) is immersed in a developer solution containing a chemical plating catalyst for 70 seconds, then taken out and air-dried in a natural environment, and then immersed in a copper plating solution and bubbled for 70 minutes to obtain a high-stability fine copper circuit.

[0057] The preparation of the developer solution containing the electroless plating catalyst is as follows: 0.5g of silver nitrate, 20mL of ammonia water and 20mL of deionized water are mixed evenly to prepare the developer solution containing the electroless plating catalyst.

[0058] Preparation of copper plating solution: Weigh 24g CuSO4·5H2O, 21g EDTA, 10g potassium sodium tartrate, 1g polyethylene glycol (20000), 70mg potassium ferrocyanide, 8mg 2,2-bipyridine, 16g NaOH and 10mL methanol, and add them to a 2L conical flask; add 1L of deionized water to the flask, stir thoroughly until completely dissolved, and the copper plating solution is obtained.

[0059] The high-stability fine copper circuit prepared in Example 3 was photographed, and the results are as follows: Figure 6 As shown, the high-stability fine copper circuit prepared in Example 3 was observed under an optical microscope, and the results are as follows. Figure 7 As shown. From Figure 6 and Figure 7 As can be seen, there is a stable distribution of copper lines on the substrate.

[0060] Scanning electron microscopy (SEM) was used to examine the high-stability fine copper circuit prepared in Example 3. The results showed that the linewidth of the bent structure was 9 μm, the line spacing was 5 μm, and the amplitude (height) was 97.6 nm.

[0061] Example 4

[0062] The fabrication of highly stable, fine copper circuits includes the following steps:

[0063] (1) A mask with a line width of 3μm and a line spacing of 2μm is selected. The fine copper circuit substrate is polytetrafluoroethylene. The mask is exposed on the surface of the polytetrafluoroethylene material using an exposure machine with a mask to obtain a polytetrafluoroethylene material with a curved surface. The exposure light source is a 405nm ultraviolet lamp with a voltage of 10V and an exposure time of 85s.

[0064] (2) Immerse the polytetrafluoroethylene material with a curved surface in (1) in a developer solution containing a chemical plating catalyst for 70s, then take it out and let it air dry in a natural environment, then immerse it in a copper plating solution and bubble it for 85 minutes using a bubble machine to obtain a high-stability fine copper circuit.

[0065] The preparation of the developer solution containing the electroless plating catalyst is as follows: 0.5g of silver nitrate, 20mL of ammonia water and 20mL of deionized water are mixed evenly to prepare the developer solution containing the electroless plating catalyst.

[0066] Preparation of copper plating solution: Weigh 24g CuSO4·5H2O, 21g EDTA, 10g potassium sodium tartrate, 1g polyethylene glycol (20000), 70mg potassium ferrocyanide, 8mg 2,2-bipyridine, 16g NaOH and 10mL methanol, and add them to a 2L conical flask; measure 1L of deionized water and add it to the flask, stir thoroughly until it is completely dissolved, and the copper plating solution is obtained.

[0067] The high-stability fine copper circuit prepared in Example 4 was scanned using a scanning electron microscope, and the results are as follows: Figure 8 As shown. From Figure 8 As can be seen, the linewidth of the curved structure is 3μm, the line spacing is 2μm, and the amplitude (height) is 167.1nm.

[0068] In summary, when using photolithography with masks of different line widths and line spacings, the bending structure of the photolithography will result in different cycles due to the different parameters of the mask. Furthermore, after copper plating, the bending structure on the surface of the fine copper circuit substrate increases the contact points between the copper and the surface of the fine copper circuit substrate, thereby improving the adhesion between the copper and the surface of the fine copper circuit substrate. Ultimately, this achieves the deposition of highly stable copper circuits on the surface of the fine copper circuit substrate.

[0069] The above description is only a specific embodiment of the present invention and not all embodiments. Any equivalent modifications made by those skilled in the art to the technical solutions of the present invention by reading the present invention specification shall be covered by the claims of the present invention.

Claims

1. A method for preparing a highly stable fine copper circuit, characterized in that: It comprises the following steps: (1) photoetching the fine copper circuit substrate to obtain a substrate with curved structure on the surface; (2) soaking the substrate with curved structure on the surface obtained in step (1) in a developer solution containing electroless plating catalyst for first treatment, taking it out and drying after the exposed area is completely covered with electroless plating catalyst, and then soaking it in a copper plating solution for second treatment to obtain a fine copper circuit with high stability; In step (1), the photoetching is performed by exposing the fine copper circuit substrate surface to parallel light source through a mask plate with set line width and line distance; In step (1), the line width of the curved structure is 1-25 μm, the line distance of the curved structure in step (1) is 1-25 μm, and the period of the curved structure in step (1) is 2-50 μm.

2. The production method according to claim 1, characterized by, The fine copper circuit substrate in step (1) is selected from one of polyimide, polyester, polytetrafluoroethylene, epoxy resin, and phenolic resin.

3. The production method according to claim 2, characterized by, The polyimide includes PMDA-ODA type polyimide, photosensitive polyimide, and BPDA-PPD polyimide.

4. The method of claim 1, wherein, The light source is selected from ultraviolet lamps with wavelength of 365-405 nm.

5. The preparation method according to claim 1, characterized in that, The voltage of the light source is 1-10 V.

6. The method of claim 1, wherein, The exposure time is 5-200 s.

7. The preparation method according to claim 1, characterized in that, The developer solution containing electroless plating catalyst in step (2) comprises silver nitrate, ammonia water, and deionized water.

8. The preparation method according to claim 7, characterized in that, The ratio between the silver nitrate, ammonia water, and deionized water is (0.5-10 g):(20-400 mL):(20-450 mL).

9. The method of claim 1, wherein, The first treatment time in step (2) is 10-100 s.

10. The method of claim 1, wherein, The height of the curved structure after the first treatment in step (2) is completed is 5-200 nm.

11. The method of claim 1, wherein, The copper plating solution in step (2) comprises copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol 20000, potassium ferrocyanide, 2,2-bipyridine, sodium hydroxide, methanol, and deionized water.

12. The method of claim 11, wherein, The ratio between the copper sulfate pentahydrate, ethylenediaminetetraacetic acid, potassium sodium tartrate, polyethylene glycol 20000, potassium ferrocyanide, 2,2-bipyridine, sodium hydroxide, methanol, and deionized water is 24 g:21 g:10 g:1 g:70 mg:8 mg:16 g:10 mL:1 L.

13. The method of claim 1, wherein, The second treatment is bubbling for 30-90 min using a bubble machine.

14. A high-stability fine copper wiring, characterized by, It is prepared by the preparation method of any one of claims 1-13.

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