Method for thermoelectrically separating a copper substrate and copper substrate

Abstract

The application belongs to the technical field of metal substrate of thermoelectric separation, and discloses a method for thermoelectric separation of copper substrate and the copper substrate. The method comprises copper base boss development, exposure and etching; RCC of the back adhesive copper foil is changed into FR4 core plate, and the FR4 core plate is cut; the outer layer circuit of the cut FR4 core plate is developed, exposed and etched; low flow adhesive is pasted on the outer layer circuit after the development, exposure and etching, then laser windowing is carried out according to the expansion and contraction size of the copper base boss after the development, exposure and etching, and the windowing size is adjusted so that the copper base boss is consistent with the windowing size of the FR4 core plate; after the laser windowing, the copper base boss and the FR4 core plate are pressed, targeted and subjected to the next process. The application solves the problem that the edge of the finished product is flat (without step difference) and the size meets the customer's requirements. After the customer pastes the part, there is no side light problem.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric separation of metal substrates, and particularly relates to a method for thermoelectric separation of copper substrates and the copper substrate itself. Background Technology

[0002] In the existing technology, copper substrate separation technology includes: copper-based boss development, exposure and etching, RCC windowing of adhesive copper foil, lamination, target bonding, outer layer circuit development, exposure and etching and the next process.

[0003] Based on the above analysis, the existing technology has the following problems and defects: poor RCC window processing yield, large deviation in the alignment of the boss and copper foil pressing, resulting in a large gap between the boss and copper foil, and ultimately the size deviation between the heat dissipation pad and the positive and negative electrode pads, affecting the customer's assembly and soldering. Summary of the Invention

[0004] To overcome the problems existing in related technologies, the present invention discloses a method for thermoelectric separation of a copper substrate and a copper substrate. The technical solution is as follows: A method for thermoelectric separation of a copper substrate, comprising the following steps: S1, copper-based boss development, exposure, and etching; S2, change the adhesive-backed copper foil RCC to FR4 core board, and perform FR4 core board cutting; S3, after the FR4 core board is cut, the outer layer circuit is developed, exposed and etched; S4, after development, exposure and etching, apply low-flow adhesive to the outer circuit, and then perform laser windowing according to the expansion and contraction dimensions of the copper-based bosses after development, exposure and etching, and adjust the window size to make the copper-based bosses consistent with the window size of the FR4 core board. S5 involves laser windowing followed by pressing the copper-based boss with the FR4 core board, target drilling, and the next process.

[0005] Furthermore, the outer layer circuit development, exposure, and etching processes for the FR4 core board after cutting include: S301, Exposure; Maskless digital lithography, LDI direct laser imaging; S302, a developer, features an optimized formula for an environmentally friendly developer solution. It uses a closed-loop control system to monitor the conductivity and temperature of the developer solution in real time and automatically replenish the solution. S303, etching.

[0006] Furthermore, maskless digital lithography uses digital micromirror devices to project patterns onto photoresist using ultraviolet light, and controls the exposure energy. The optical resolution formula is: In the formula, For optical resolution, The wavelength of the light source, Numerical aperture; The exposure dose is dynamically adjusted to match different linewidth requirements. The exposure energy control formula is as follows: In the formula, In order to expose energy, Light intensity, This refers to the duration of illumination.

[0007] Furthermore, LDI direct laser imaging includes: using an ultraviolet laser beam to directly scan and image on the photoresist, combined with an automatic alignment system, the alignment accuracy model is as follows: In the formula, This is the alignment precision value. For mechanical error coefficient, This represents the temperature fluctuation value. Through temperature control Controlled within ±1.5μm.

[0008] Furthermore, the environmentally friendly developer formulation optimization includes: replacing strongly alkaline solutions with sodium carbonate at a concentration of 0.8-1.2%, adding surfactants to enhance wettability, and achieving a residue removal rate of: In the formula, This is the initial residual amount. for Residual amount at any time Residue removal rate; The developer solution conductivity and temperature are monitored in real time by a closed-loop control system, and the solution is automatically replenished. The replenishment amount is: In the formula, To replenish the volume of the medicine solution, The attenuation coefficient is... for conductivity at time t. The initial conductivity, The area is the board area.

[0009] Furthermore, the etching includes: ① Before etching, a rosin-BTA mixed solution is applied to form a protective film covering the top and sidewalls of the circuit. The expression for controlling the side etching amount is: In the formula, This represents the lateral erosion value. For mechanical error coefficient, For the moment during etching, Etching rate; ② Dynamic control of acid etching: real-time adjustment of the etching solution based on redox potential (ORP). Concentration; ORP feedback model is: In the formula, As an adjustment constant, Etching solution The concentration, maintain At 150±10g / L.

[0010] Furthermore, laser windowing includes: Phase 1, Basic Data Modeling; Phase 2 involves constructing a dynamic compensation system for laser windowing based on convolutional neural networks; and adjusting the design dimensions of the copper-based boss window. The pressing temperature T and the material CTE library are input into the pre-compensation calculator, which then generates the compensated window opening size. Based on the generated compensated window size The laser component is controlled by a laser controller to perform laser etching and laser windowing. The copper-based boss and the FR4 core board after the windowing are measured and verified, and feedback correction coefficients are applied to make the window size of the copper-based boss and the FR4 core board consistent. Phase 3 involves laser windowing and parameter control.

[0011] Furthermore, basic data modeling includes: (a) Determination of material expansion coefficient; The thermal expansion coefficients of the copper-based boss and the FR4 core board were measured and a database was established; (b) Historical process data analysis; collection of dimensional changes of multiple sets of copper-based bosses before and after lamination. With FR4 expansion and contraction The corresponding relationship is used to fit the regression curve; In Phase 2, a laser windowing dynamic compensation system based on convolutional neural networks is constructed. The pre-compensation calculator adjusts the window size after compensation through a multi-factor compensation model. The size is expressed as: In the formula, To compensate for the rear window size, Dimensions for window design on copper-based bosses For structural stress factor, For the temperature rise during the pressing process, The coefficient of thermal expansion of FR4 core board. The coefficient of thermal expansion of the copper-based boss. The coefficient of frictional decay is the rheological decay coefficient of the adhesive. This refers to the curing time of the adhesive layer. This is the system error constant of the equipment.

[0012] Furthermore, in Phase 2, a dynamic compensation system for laser windowing is constructed, in which the correction coefficient is fed back in real time. include: In the formula, For the first This is the correction factor after opening the window. For measurement difference, For the target difference, The standard deviation is denoted as .

[0013] Furthermore, in stage 3, laser windowing is performed, and parameter control is implemented, including: For adhesive layer curing control, the viscosity of low-flow adhesive needs to be stable at 2000±50cP, and the curing temperature curve gradient should be ≤3℃ / min. The positioning benchmark was optimized by using an optical target plus CCD positioning. Laser parameter adjustment: wavelength 355nm, spot overlap rate ≥30%, depth control error ≤2μm; The correction factor value is dynamically adjusted for each batch based on the CPK value.

[0014] Another object of the present invention is to provide a copper substrate that is separated using the aforementioned thermoelectric separation method.

[0015] Combining all the above technical solutions, the beneficial effects of this invention are as follows: By adjusting the product stacking structure, this invention changes the adhesive-backed copper foil RCC to a core board. Instead of opening windows in the adhesive-backed copper foil RCC and then laminating it before fabricating the outer layer circuitry, the core board is used to fabricate the outer layer circuitry first, then adhesive is applied, windows are opened, and then it is laminated. After applying adhesive to the core board, laser opening is used, which can be adjusted according to the expansion and contraction dimensions of the copper substrate of the boss, ensuring that the window size of the boss and the copper foil on the core board are consistent, and the distance between the boss and the copper foil is minimized. This invention solves the problem of finished board edges being flat (without step differences) and dimensions meeting customer requirements. Customers will not experience side lighting issues after component mounting. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure; Figure 1 This is a flowchart of the thermoelectric separation method for copper substrates provided in an embodiment of the present invention; Figure 2 This is a flowchart of the process of developing, exposing, and etching the outer layer circuitry of the FR4 core board after it has been cut, as provided in an embodiment of the present invention. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] Example 1: The method for thermoelectric separation of copper substrate provided in this embodiment of the invention, such as... Figure 1 As shown, it includes: S1, copper-based boss development, exposure, and etching; S2, change the adhesive-backed copper foil RCC to FR4 core board, and perform FR4 core board cutting; S3, after the FR4 core board is cut, the outer layer circuit is developed, exposed and etched; S4, after development, exposure and etching, apply low-flow adhesive to the outer circuit, and then perform laser windowing according to the expansion and contraction dimensions of the copper-based bosses after development, exposure and etching, and adjust the window size to make the copper-based bosses consistent with the window size of the FR4 core board. S5 involves laser windowing followed by pressing the copper-based boss with the FR4 core board, target drilling, and the next process.

[0019] For example, such as Figure 2 In step S3, the outer layer circuit development, exposure, and etching of the FR4 core board after cutting includes: S301, exposed; including: (1) Maskless digital lithography (DLP technology): Digital micromirror devices (DMD) are used to replace traditional photomasks, and the pattern is transferred directly onto the photoresist by ultraviolet light projection.

[0020] The formula for optical resolution is: In the formula, For optical resolution, The wavelength of the light source, Numerical aperture; DLP technology can achieve .

[0021] The exposure dose is dynamically adjusted to match different linewidth requirements. The exposure energy control formula is as follows: In the formula, In order to expose energy, Light intensity, The illumination time is adjusted. The resolution is improved to ≤2μm, with an accuracy 30% higher than traditional contact exposure; the mask production is eliminated, shortening the production cycle by more than 50%.

[0022] (2) LDI (Laser Direct Imaging) technology; Ultraviolet laser beams are used to directly scan and image the photoresist, combined with an automatic alignment system. The alignment accuracy model is as follows: In the formula, This is the alignment precision value. For mechanical error coefficient, This refers to temperature fluctuation values; temperature control will... Controlled within ±1.5μm, reducing pattern offset defects and improving yield by 8%-12%; supports high-density interconnect (HDI) boards with ≤30μm line width / spacing.

[0023] S302, developer; includes: 1) Optimized formulation of environmentally friendly developer; Steps: Replace the strong alkaline solution with a low concentration of sodium carbonate (0.8-1.2%) and add a surfactant to enhance wettability.

[0024] The residue removal rate is: In the formula, This is the initial residual amount. for Residual amount at any time Residue removal rate; after optimization This reduces the COD value of wastewater and lowers treatment costs; it also improves the uniformity of development and avoids jagged edges on the lines.

[0025] 2) Closed-loop control system; real-time monitoring of developer conductivity and temperature, and automatic replenishment of reagents.

[0026] The developer solution conductivity and temperature are monitored in real time by a closed-loop control system, and the solution is automatically replenished. The replenishment amount is: In the formula, To replenish the volume of the medicine solution, The attenuation coefficient is... for conductivity at time t. The initial conductivity, This refers to the plate area. It extends the lifespan of the chemical solution, reducing downtime for maintenance.

[0027] S303, etching, including: ① Corrosion inhibitor film technology; Steps: Before etching, a rosin-BTA mixed solution is applied to form a protective film covering the top and sidewalls of the circuit. The expression for controlling the side etching amount is: In the formula, This represents the lateral erosion value. For mechanical error coefficient, For the moment during etching, Etching rate; after optimization (The traditional process is 15μm), the yield of precision circuits (≤0.1mm) is improved by 15%; the risk of copper foil over-etching is reduced and the impedance stability is improved.

[0028] ② Dynamic control of acid etching: real-time adjustment of the etching solution based on redox potential (ORP). Concentration; ORP feedback model is: In the formula, As an adjustment constant, Etching solution The concentration, maintain At 150±10 g / L, the etching uniformity is ≤5%, avoiding localized unetched / over-etched areas; the etching rate is stabilized at 25±2 μm / min, increasing production capacity by 20%.

[0029] As can be seen from the above embodiments, the FR4 core board after the material is cut in step S3 undergoes outer layer circuit development, exposure, and etching. The technical effect is compared with the existing technology, as shown in Table 1.

[0030] Table 1. Comparison of Technological Effects parameter Traditional crafts Improved Increase Minimum line width 50μm 15μm 70% Lateral erosion 15μm ≤8μm 47% Etching uniformity ±15% ≤±5% 67% wastewater ammonia nitrogen discharge 120mg / L ≤50mg / L 58%↓ Overall yield 82% ≥95% 13% The material innovations of this invention include: rosin-BTA etching inhibitor film and low-toxicity developer to reduce environmental impact; intelligent equipment: DLP / LDI exposure and ORP dynamic control to improve accuracy and stability; and integrated processes: closed-loop control of development and etching to achieve full-process parameter optimization. After development, exposure, and etching, low-flow adhesive is applied to the outer layer circuitry. Then, laser windowing is performed based on the expansion and contraction dimensions of the copper-based bosses after development, exposure, and etching, and the window size is adjusted to ensure consistency between the copper-based bosses and the window size on the FR4 core board. Laser windowing includes: Phase 1, basic data modeling, including: (a) Determination of the coefficient of thermal expansion of materials; Measured copper-based bosses (CTE) Cu ≈17ppm / ℃) and FR4 core board (CTE) FR4 The coefficient of thermal expansion (≈14-18ppm / ℃) was used to establish a database.

[0031] (b) Historical process data analysis; The correlation between the dimensional changes ΔLCu of copper-based bosses before and after pressing and the expansion and contraction ΔLFR4 of FR4 was collected, and regression curves were fitted.

[0032] Phase 2 involves constructing a laser windowing dynamic compensation system based on convolutional neural networks, including inputting the copper-based boss windowing design size D0, pressing temperature T, and material CTE library into the pre-compensation calculator. The compensated window size is generated using the pre-compensation calculator. Based on the generated compensated window size The laser component is controlled by a laser controller to perform laser etching and laser windowing. The copper-based boss and the FR4 core board after the windowing are measured and verified, and feedback correction coefficients are applied to make the window size of the copper-based boss and the FR4 core board consistent. Phase 3 involves laser windowing and parameter control. Adhesive curing control: The viscosity of low-flow adhesive needs to be stable at 2000±50 cP, and the curing temperature gradient should be ≤3℃ / min; Positioning reference optimization: Optical target + CCD positioning is adopted, with an accuracy of ±5μm; Laser parameter adjustment: wavelength 355nm, spot overlap rate ≥30%, depth control error ≤2μm; For example, in Phase 2, in the laser windowing dynamic compensation system based on convolutional neural networks, the pre-compensation calculator adjusts the window size after compensation through a multi-factor compensation model. Size; In the formula, To compensate for the rear window size (target value). Dimensions for window design on copper-based bosses For structural stress factor, Temperature rise (°C) during the pressing process. The coefficient of thermal expansion of FR4 core board. The coefficient of thermal expansion of the copper-based boss. The coefficient of frictional decay is the rheological decay coefficient of the adhesive. This represents the curing time of the adhesive layer (min). This is the equipment system error constant (obtained through calibration).

[0033] For example, in the phase 2 construction of the laser windowing dynamic compensation system, the real-time feedback correction coefficient K includes: In the formula, For the first This is the correction factor after opening the window. For measurement difference, For the target difference, Standard deviation; The correction factor value is dynamically adjusted for each batch based on the CPK value; in scenarios where the correction factor value is dynamically adjusted, the CPK value is usually used as the basis for adjustment. The formula for calculating the correction factor K value is: Wherein, CP is the process capability index (an index that does not consider the deviation between the process center and the specification center), and A is the correction coefficient, reflecting the degree of deviation between the process center and the specification center. When the CPK value is low, it indicates that there is a deviation or large fluctuation in the process. At this time, it is necessary to increase the CPK value by adjusting process parameters, optimizing the process, etc., and then dynamically correct the value to ensure the stability of the production process and the consistency of product quality.

[0034] To verify that the copper-based boss and the window size of the FR4 core board are consistent, the following experiment was conducted. The experimental design is shown in Table 2.

[0035] Table 2 Experimental Matrix Variable factors Level 1 Level 2 Level 3 detection indicators Pressing temperature 180℃ 190℃ 200℃ Uniformity of copper hole thickness Adhesive layer thickness 40μm 60μm 80μm Thermal stress warpage Laser scanning speed 2m / s 3m / s 4m / s Window edge roughness Ra Expansion / Contraction Compensation Rate 90% model 100% model 110% model Offset between copper-based boss and window center Verification methods: Microscopic inspection, SEM observation of the window sidewall angle (target 85°-88°), X-ray measurement of the overlap between the copper-based boss and the window (requirement ≥95%); Reliability testing: TCT test (-55℃). After 1000 cycles at 125℃, the impedance change was measured to be ≤5%; the risk of adhesive layer delamination was assessed by high-pressure boiling test (121℃ / 100%RH, 96hr).

[0036] This invention develops a size prediction model based on machine learning, with training data from: 1000+ sets of historical production data and finite element thermal stress simulation results (ANSYS model); adhesive layer interface control technology, adding 5% nano-silica to improve CTE matching, and developing a stepped curing process to reduce internal stress; laser-vision closed-loop control, employing a real-time image processing algorithm (convolutional neural network); pseudocode example: while etching: img = CCD.capture() offset = CNN_detect(img,template) # Detect positional deviation if offset > 5μm: galvo.adjust(offset * 0.8) # Dynamically adjust the optical path record(offset, temperature).

[0037] Moreover, this invention completed the construction of the CTE database and verified the compensation formula in a small batch during the first phase. The second phase deployed a laser-vision joint control system, increasing CPK to 1.33. The third phase achieved fully automatic compensation, with a yield of ≥98% and a cost reduction of 22%. This invention breaks through the traditional "trial and error" adjustment mode. By digitizing material properties, modeling process parameters, and intelligentizing equipment control, it solves the problem of expansion and de-extension matching between copper-based bosses and FR4 in high-frequency and high-speed PCBs. It is suitable for high-end fields such as 5G base station / AI chip packaging.

[0038] Example 2: The present invention also provides a copper substrate, which is separated using the aforementioned thermoelectric separation method for copper substrates. Furthermore, the present invention is applicable to all thermoelectrically separated metal substrates.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for thermoelectric separation of a copper substrate, characterized in that, The method includes the following steps: S1, copper-based boss development, exposure, and etching; S2, change the adhesive-backed copper foil RCC to FR4 core board, and perform FR4 core board cutting; S3, after the FR4 core board is cut, the outer layer circuit is developed, exposed and etched; S4, after development, exposure and etching, apply low-flow adhesive to the outer circuit, and then perform laser windowing according to the expansion and contraction dimensions of the copper-based bosses after development, exposure and etching, and adjust the window size to make the copper-based bosses consistent with the window size of the FR4 core board. S5 involves laser windowing followed by pressing the copper-based boss with the FR4 core board, target drilling, and the next process.

2. The method for thermoelectric separation of copper substrate according to claim 1, characterized in that, In step S3, the outer layer circuit development, exposure, and etching of the FR4 core board after cutting includes: S301, Exposure; Maskless digital lithography, LDI direct laser imaging; S302, a developer, features an optimized formula for an environmentally friendly developer solution. It uses a closed-loop control system to monitor the conductivity and temperature of the developer solution in real time and automatically replenish the solution. S303, etching.

3. The method for thermoelectric separation of copper substrate according to claim 2, characterized in that, In step S301, maskless digital lithography uses a digital micromirror device to project a pattern onto the photoresist using ultraviolet light, and controls the exposure energy. The optical resolution formula is: In the formula, For optical resolution, The wavelength of the light source, Numerical aperture; The exposure dose is dynamically adjusted to match different linewidth requirements. The exposure energy control formula is as follows: In the formula, In order to expose energy, Light intensity, This refers to the duration of illumination.

4. The method for thermoelectric separation of copper substrate according to claim 2, characterized in that, In step S301, LDI laser direct imaging includes: using an ultraviolet laser beam to directly scan and image on the photoresist, combined with an automatic alignment system, the alignment accuracy model is: In the formula, This is the alignment precision value. For mechanical error coefficient, This represents the temperature fluctuation value. Through temperature control Controlled within ±1.5μm.

5. The method for thermoelectric separation of a copper substrate according to claim 2, characterized in that, In step S302, the optimization of the environmentally friendly developer formulation includes: replacing the strongly alkaline solution with sodium carbonate at a concentration of 0.8-1.2%, adding a surfactant to enhance wettability, and achieving a residue removal rate of: In the formula, This is the initial residual amount. for Residual amount at any time Residue removal rate; The developer solution conductivity and temperature are monitored in real time by a closed-loop control system, and the solution is automatically replenished. The replenishment amount is: In the formula, To replenish the volume of the medicine solution, The attenuation coefficient is... for conductivity at time t. The initial conductivity, The area is the board area.

6. The method for thermoelectric separation of a copper substrate according to claim 2, characterized in that, In step S303, etching includes: ① Before etching, a rosin-BTA mixed solution is applied to form a protective film covering the top and sidewalls of the circuit. The expression for controlling the side etching amount is: In the formula, This represents the lateral erosion value. For mechanical error coefficient, For the moment during etching, Etching rate; ② Dynamic control of acid etching: real-time adjustment of the etching solution based on redox potential (ORP). Concentration; ORP feedback model is: In the formula, As an adjustment constant, Etching solution The concentration, maintain At 150±10g / L.

7. The method for thermoelectric separation of a copper substrate according to claim 1, characterized in that, In step S4, laser windowing includes: Phase 1, Basic Data Modeling; Phase 2 involves constructing a dynamic compensation system for laser windowing based on convolutional neural networks; and adjusting the design dimensions of the copper-based boss window. The pressing temperature T and the material CTE library are input into the pre-compensation calculator, which then generates the compensated window opening size. Based on the generated compensated window size The laser component is controlled by a laser controller to perform laser etching and laser windowing. The copper-based boss and the FR4 core board after the windowing are measured and verified, and feedback correction coefficients are applied to make the window size of the copper-based boss and the FR4 core board consistent. Phase 3 involves laser windowing and parameter control.

8. The method for thermoelectric separation of a copper substrate according to claim 7, characterized in that, In Phase 1, basic data modeling includes: (a) Determination of material expansion coefficient; The thermal expansion coefficients of the copper-based boss and the FR4 core board were measured and a database was established; (b) Historical process data analysis; collection of dimensional changes of multiple sets of copper-based bosses before and after lamination. With FR4 expansion and contraction The corresponding relationship is used to fit the regression curve; In Phase 2, a laser windowing dynamic compensation system based on convolutional neural networks is constructed. The pre-compensation calculator adjusts the window size after compensation through a multi-factor compensation model. The size is expressed as: In the formula, To compensate for the rear window size, Dimensions for window design on copper-based bosses For structural stress factor, For the temperature rise during the pressing process, The coefficient of thermal expansion of FR4 core board. The coefficient of thermal expansion of the copper-based boss. The coefficient of frictional decay is the rheological decay coefficient of the adhesive. This refers to the curing time of the adhesive layer. This is the system error constant of the equipment.

9. The method for thermoelectric separation of a copper substrate according to claim 8, characterized in that, Phase 2 involves constructing a dynamic compensation system for laser windowing, with real-time feedback of correction coefficients. include: In the formula, For the first This is the correction factor after opening the window. For measurement difference, For the target difference, Standard deviation; In stage 3, laser windowing is performed, and parameter control is carried out, including: For adhesive layer curing control, the viscosity of low-flow adhesive needs to be stable at 2000±50cP, and the curing temperature curve gradient should be ≤3℃ / min. The positioning benchmark was optimized by using an optical target plus CCD positioning. Laser parameter adjustment: wavelength 355nm, spot overlap rate ≥30%, depth control error ≤2μm; The correction factor value is dynamically adjusted for each batch based on the CPK value.

10. A copper substrate, characterized in that, It is separated using the thermoelectric separation method for copper substrates as described in any one of claims 1-9.

Images