Selective electroplating method for ceramic copper-clad substrate
Through double mask exposure technology and selective electroplating nickel-gold process, the problems of conductive bridge structure damage and ink contamination in ceramic copper clad substrate processing are solved, and efficient and accurate circuit production is achieved.
Patent Information
- Application Number
- CN202510605147.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-12
- Publication Date
- 2025-07-18
AI Technical Summary
In the traditional ceramic copper clad substrate processing technology, the conductive bridge structure is prone to edge serration effect during the exposure and development stage, resulting in damage to pattern integrity, and the ink coating method in the solder resist process is prone to contamination and long production cycle.
The dual mask exposure technology is used to position the through holes at the edge of the substrate as the paraposition reference, combining selective plating and single etching to achieve selective plating of nickel gold, simplifying the process flow, and avoiding damage to the conductive bridge structure and ink contamination.
Significantly shorten the production cycle, improve the accuracy of graphic engraving, avoid damage to copper edge gaps, solve the problem of substrate pollution caused by ink splashing and adhesion, and ensure circuit integrity.
Smart Images
Figure CN120330830A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of ceramic copper-clad substrate processing, and in particular to a ceramic copper-clad substrate selective electroplating method. Background Art
[0002] The traditional surface treatment process of ultra-thick copper substrate is: to form the circuit outline through graphic etching, and to achieve electrical conduction of each independent copper area by reserving copper conductive bridges during the etching process. After the etching is completed, photosensitive ink needs to be printed. This step requires accurate filling of the circuit grooves formed by etching to save precious metal consumption, and at the same time, physical isolation of the electroplating area and the non-electroplating area. After the nickel-gold electroplating is completed, the ink needs to be chemically de-washed, the photosensitive ink needs to be re-printed, and the circuit area needs to be completely filled. At this time, the reserved conductive copper bridge structure needs to be removed by secondary etching.
[0003] However, this process has the following problems: First, in terms of the conductive bridge structure processing, the ultra-thick copper substrate is prone to edge sawtooth effects during the exposure and development stage, resulting in damage to the integrity of the conductive bridge pattern. This graphic defect will be geometrically magnified in the subsequent etching process, eventually resulting in residual conductive bridges or over-etching gaps, seriously affecting the electrical performance of the circuit. Secondly, in the solder mask process, the traditional ink coating method relies on repeated printing to fill between lines, which not only increases the production cycle, but also is more likely to cause adjacent line contamination problems caused by ink overflow. In addition, the ink dewashing takes a long time, and it is difficult to maintain a stable dewashing rate under mass production conditions. It is easy to have incomplete dewashing or over-corrosion, which directly affects the bonding strength of the secondary solder mask layer. Summary of the invention
[0004] Based on this, it is necessary to provide a selective electroplating method for ceramic copper-clad substrates to address the problems of complex electroplating processes and incomplete and gapped copper strip patterns.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:
[0006] A method for selective electroplating of a ceramic copper-clad substrate comprises the following steps:
[0007] Copper and ceramic sheets are used to make alignment targets, which are then cleaned and sintered into substrates. Liquid photosensitive ink with a thickness of 10-30 μm is applied to the surface of the substrate by spin coating, and then baked to form a rigid dry film.
[0008] The alignment target on the substrate is aligned with the film with a pre-set reference mark, and a UV light source with a wavelength of 436nm is used for selective exposure, followed by development to form a plating window and electroplating nickel and gold, and an organic alkaline solution is used to strip the film;
[0009] Press the photosensitive dry film on the substrate after film stripping. After standing still, align and calibrate it again with the film with reference marks through the alignment target points of the substrate. Use ultraviolet light with a wavelength of 365 nm for pattern transfer. The electroplated nickel-gold is covered by the dry film and the etching area is exposed;
[0010] Develop and etch the circuit on the substrate with the exposed etching area. Use an alkaline solution to remove the solder and strip the film. After cleaning, cut the optical fiber to obtain the required circuit board.
[0011] Furthermore, when making alignment target points on the copper sheet and porcelain sheet, use an optical fiber cutting machine and a drilling machine to drill holes on the porcelain sheet and copper sheet respectively, and the hole diameter is 1.95 - 2.05 mm.
[0012] Furthermore, spin-coat the substrate with a liquid photosensitive ink with a solid content of 60%, and bake it in a hot air circulation oven at 80 °C for 30 min to form a rigid dry film with a Shore D hardness of 82 - 88.
[0013] Furthermore, when aligning and calibrating the substrate with the film pre-set with reference marks through the alignment target points on the substrate, fix the substrate and the film with pins for positioning.
[0014] Furthermore, when aligning and calibrating the substrate with the film pre-set with reference marks through the alignment target points on the substrate, load the substrate onto an exposure machine with an AOI vision system, and align and calibrate it through the alignment target points and the reference marks on the film.
[0015] Furthermore, the specific steps for loading the substrate onto an exposure machine with an AOI vision system and aligning and calibrating it through the alignment target points and the reference marks on the film are as follows:
[0016] Establish a physical coordinate system based on the platform where the substrate is located and obtain the physical coordinates of the alignment target points. The exposure machine with an AOI vision system identifies the substrate to establish a vision coordinate system, captures the alignment target points of the substrate in real time, calculates the displacement difference from the reference marks on the film after coordinate transformation, and then adjusts the position of the substrate to align the alignment target points of the substrate with the reference marks on the film.
[0017] Furthermore, when selectively exposing the substrate with an ultraviolet light source with a wavelength of 436 nm, the energy density used is 80 mj / cm 2 ; when using ultraviolet light with a wavelength of 365 nm for pattern transfer, the energy density is adjusted to 60 mj / cm 2 .
[0018] Furthermore, when developing the substrate, use a sodium carbonate developer solution with a concentration of 1.5% to spray and develop for 60 s to form an electroplating window area, and the opening rate ≥ 85%.
[0019] Furthermore, when electroplating nickel-gold on the substrate, use NI2+ A nickel sulfate electroplating solution with a concentration of 300 g / L or CI - A nickel chloride electroplating solution with a concentration of 60 g / L, the thickness of the nickel plating layer is controlled at 3 - 5 μm, and the gold plating layer is controlled at 0.05 - 0.1 μm.
[0020] Further, a photosensitive dry film is laminated on the substrate after film stripping. After standing for 15 - 60 min, it is aligned and calibrated again with the film with reference marks through the alignment target points of the substrate.
[0021] Compared with the prior art, the beneficial effects of the present invention include:
[0022] 1. By adopting a double - mask exposure technology to replace the traditional three - mask process and completing the pattern formation through single - time etching, the production cycle is greatly shortened, mass production can be achieved, the production speed is fast, there is no need for the cumbersome process of ink printing, and there is no need for etching of reserved conduction copper bars. It will not cause the notch at the copper edge to damage the integrity of the substrate circuit pattern, and solve the problem of substrate pollution caused by ink splashing and adhesion.
[0023] 2. Using the high - precision positioning through - holes at the edge of the substrate as the spatial reference for two - mask exposures, the alignment accuracy is high, ensuring the pattern overlay accuracy. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The disclosure of the present invention will be described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them:
[0025] Figure 1 is a flowchart of a selective electroplating method for a ceramic - copper - clad substrate of the present invention;
[0026] Figure 2 is a schematic diagram of the alignment and calibration of the film and the substrate. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0027] It is easy to understand that according to the technical solution of the present invention, without changing the essence of the present invention, those of ordinary skill in the art can propose various alternative structural forms and implementation methods. Therefore, the following detailed embodiments and the accompanying drawings are only illustrative descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction on the technical solution of the present invention.
[0028] As Figure 1 shown, a selective electroplating method for a ceramic - copper - clad substrate includes the following steps:
[0029] S1. Make alignment targets on the copper sheet and porcelain sheet, clean them and sinter them into a substrate. Use the spin coating method to coat a liquid photosensitive ink with a thickness of 10 - 30 μm on the surface of the substrate, and bake it to form a rigid dry film.
[0030] Specifically: Use a fiber optic cutting machine and a drilling machine to drill holes in the porcelain sheet and copper sheet respectively. The positioning through holes serve as alignment targets, with a hole diameter of 0.2 ± 0.05 mm. Other marks can also be made. Subsequently, clean the copper sheet and porcelain sheet, perform solder printing, and sinter them into a substrate. Then clean the surface of the substrate, use the spin coating method to coat a liquid photosensitive ink (solid content 60%) with a thickness of 10 - 30 μm on the surface of the substrate, and bake it in an 80°C hot air circulation oven for 30 min to form a rigid dry film (hardness Shore D 85 ± 3).
[0031] S2. Align and calibrate the substrate with a film pre - set with reference marks through the alignment targets on the substrate, use a UV light source with a wavelength of 436 nm for selective exposure, then develop to form an electroplating window and electroplate nickel - gold, and use an organic alkaline solution to strip the film.
[0032] Specifically: Fix the position through pins or load the substrate onto an exposure machine with an AOI vision system (resolution < 5 μm), align and calibrate through the positioning through holes and the reference marks on the film (alignment accuracy ≤ 20 μm), then use a UV light source with a wavelength of 436 nm for selective exposure, with an energy density of 80 mj / cm 2 . Spray - develop with a sodium carbonate developer solution (concentration 1.5%) for 60 s to form an electroplating window area (opening rate ≥ 85%). In a nickel sulfate / nickel chloride electroplating solution (NI 2+ concentration 300 g / L, CI - concentration 60 g / L), control the nickel plating layer thickness at 3 - 5 μm and the gold plating layer at 0.05 - 0.1 μm. Use an organic base solution to wash and strip the photosensitive film. After rinsing, there should be no chemical residues, which will not affect the copper and nickel - gold on the surface of the substrate.
[0033] The following details the alignment and calibration:
[0034] One way is that the reference mark on the film is a through - hole, and a pin is set in the through - hole. The pin enters the positioning through - hole of the substrate to achieve the positioning of the substrate and the film.
[0035] Another way is to load the substrate onto an exposure machine with an AOI vision system for alignment and calibration and then exposure. Obtain the physical coordinates of the center of the through - hole of the substrate through probe contact or laser ranging. High - precision sensors can also be used to provide real - time feedback on the displacement of the platform. The exposure machine with an AOI vision system comes with an industrial camera to identify the substrate. Establish a physical coordinate system (X m , Y m , Zm ) and obtain the physical coordinates (x p , y p , z p ) of the center of the alignment target. Based on the camera imaging plane, establish a vision coordinate system (X v , Y v , Z v ) and obtain the hole center coordinates (x v , y v , z v ). Through the calibration matrix, the conversion between the two coordinate systems can be realized, align the timestamps of the mechanical and vision data, convert the vision coordinates to physical coordinates, calculate the residuals and perform dynamic compensation, synchronously identify the fiducial marks on the film, calculate the displacement difference from the fiducial marks on the film, and then adjust the substrate position to align the alignment target on the substrate with the fiducial marks on the film. After alignment calibration, perform the exposure operation.
[0036] S3. Press and laminate a photosensitive dry film on the substrate after film removal. After standing still, align and calibrate again through the alignment target on the substrate and the film with fiducial marks. Use ultraviolet light with a wavelength of 365 nm for pattern transfer. The electroplated nickel-gold is covered by the dry film and the etching area is exposed.
[0037] Specifically: On the substrate that has completed electroplating nickel-gold, perform the masking process again. After masking is completed, let it stand for 15 - 60 minutes. Then, use the original positioning through holes and the fiducial marks on the film for double calibration and alignment. Use ultraviolet light with a wavelength of 365 nm for pattern transfer, and adjust the energy density to 60 mj / cm 2 . Through the hierarchical design of the film, make the electroplated area completely covered by the dry film, so as to protect the electroplated nickel-gold area from being eroded by the acidic etching solution and accurately expose the etching area.
[0038] S4. Develop and etch the circuit on the substrate with the exposed etching area. Use an alkaline solution to remove the solder and strip the film. After cleaning, perform fiber cutting to obtain the required circuit board.
[0039] Specifically: Develop and etch the circuit on the substrate with the exposed etching area. Use an etching solution containing sodium chlorate and hydrochloric acid for etching. Use an alkaline solder removal solution to remove the solder exposed on the circuit. While removing the solder, also remove the photosensitive dry film laminated for the second time. Then, perform surface cleaning and fiber cutting to obtain the required circuit board.
[0040] As Figure 2 shown, the key points of this embodiment are:
[0041] Substrate pretreatment and positioning hole machining:
[0042] Machine positioning through holes on the edge of the substrate as the alignment reference for two masking exposures.
[0043] First Masking and Electroplating:
[0044] Coat photosensitive film → Align and expose through alignment holes → Develop to form electroplating window → Electroplate nickel-gold → Strip the film with alkaline solution.
[0045] Second Masking and Etching:
[0046] Press and laminate photosensitive dry film for the second time → Align and expose using the reused alignment holes → Develop to cover the gold-plated area and expose the copper layer to be etched → Etch the copper layer → Remove residual solder with alkaline solution.
[0047] First stage (definition of electroplating area): Align the first mask through the alignment vias, expose and develop to form an electroplating window → Electroplate nickel-gold → Strip the film with organic alkaline solution;
[0048] Second stage (definition of etching area): Reuse the same set of alignment holes to align the second mask, expose and develop to cover the gold-plated area → Etch the copper layer → Remove solder with alkaline solution.
[0049] The first mask focuses on the transfer of electroplating patterns, and the second mask emphasizes etching protection. The process of selective electroplating nickel-gold can be achieved in a relatively simple way, with no alkaline substance residue on the copper surface.
[0050] In this embodiment, the double-masking exposure technology is adopted to replace the traditional three-masking process, and the pattern formation is completed by single etching, greatly shortening the production cycle. Batch production can be realized, with a fast production speed. There is no need for the cumbersome process of ink printing, nor the etching of reserved conduction copper bars. It will not cause the notch at the copper edge to damage the integrity of the substrate circuit pattern, and solves the problem of substrate pollution caused by ink splashing and adhesion; Using the high-precision alignment vias at the edge of the substrate as the spatial reference for the two-masking exposures, the alignment accuracy is high, ensuring the accurate pattern registration.
[0051] The technical scope of the present invention is not limited to the content described above. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.
Claims
1. A selective electroplating method for ceramic copper-clad substrates, characterized in that, It includes the following steps: Make alignment targets on the copper sheet and ceramic sheet, clean them and sinter them into a substrate. Use the spin coating method to coat a liquid photosensitive ink with a thickness of 10 - 30 μm on the surface of the substrate, and bake it to form a rigid dry film. Perform alignment calibration on the substrate through the alignment targets on the substrate and the film with reference marks preset. Use a UV light source with a wavelength of 436 nm for selective exposure, then develop to form an electroplating window and electroplate nickel - gold, and use an organic alkaline solution to strip the film. Laminte a photosensitive dry film on the substrate after film stripping. After standing, perform alignment calibration again through the alignment targets on the substrate and the film with reference marks. Use UV light with a wavelength of 365 nm for pattern transfer. The electroplated nickel - gold is covered by the dry film and the etching area is exposed. Develop and etch the circuit on the substrate with the etching area exposed. Use an alkaline solution to remove the solder and strip the film. After cleaning, perform fiber cutting to obtain the required circuit board.
2. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, characterized in that When making alignment targets on the copper sheet and ceramic sheet, use a fiber optic cutting machine and a drilling machine to drill holes on the ceramic sheet and copper sheet respectively, and the hole diameter is 1.95 - 2.05 mm.
3. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, wherein Use a liquid photosensitive ink with a solid content of 60% to spin - coat on the substrate, and bake it in a hot air circulation oven at 80 °C for 30 min to form a rigid dry film with a Shore D hardness of 82 - 88.
4. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, wherein When performing alignment calibration on the substrate through the alignment targets on the substrate and the film with reference marks preset, fix the substrate and the film for positioning through pins.
5. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, wherein When performing alignment calibration on the substrate through the alignment targets on the substrate and the film with reference marks preset, load the substrate onto an exposure machine with an AOI vision system, and perform alignment calibration through the alignment targets on the substrate and the reference marks on the film.
6. The selective electroplating method of the ceramic copper-clad substrate according to claim 5, characterized in that, The specific steps of loading the substrate onto an exposure machine with an AOI vision system and performing alignment calibration through the alignment targets on the substrate and the reference marks on the film are as follows: Establish a physical coordinate system based on the platform where the substrate is located and obtain the physical coordinates of the alignment targets. The exposure machine with an AOI vision system identifies the substrate to establish a vision coordinate system, captures the alignment targets on the substrate in real - time, calculates the displacement difference from the reference marks on the film after coordinate conversion, and then adjusts the position of the substrate to align the alignment targets on the substrate with the reference marks on the film.
7. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, characterized in that When selectively exposing the substrate with an ultraviolet light source having a wavelength of 436 nm, the energy density used is 80 mj / cm 2 ; when performing pattern transfer with ultraviolet light having a wavelength of 365 nm, the energy density is adjusted to 60 mj / cm 2 .
8. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, characterized in that, When developing the substrate, use a sodium carbonate developer with a concentration of 1.5% to spray - develop for 60 s to form an electroplating window area, and the opening rate ≥ 85%.
9. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, wherein When electroplating nickel and gold on the substrate, use NI 2+ nickel sulfate electroplating solution with a concentration of 300 g / L or CI - nickel chloride electroplating solution with a concentration of 60 g / L. The thickness of the nickel plating layer is controlled at 3 - 5 μm, and the gold plating layer is controlled at 0.05 - 0.1 μm.
10. The selective electroplating method of the ceramic copper-clad substrate according to claim 1, wherein Laminte a photosensitive dry film on the substrate after film stripping. After standing for 15 - 60 min, perform alignment calibration again through the alignment targets on the substrate and the film with reference marks.