Laser-induced liquid applicable to various dielectric materials and method for preparing copper circuit by using laser-induced liquid

Abstract

The invention discloses a laser-induced liquid applicable to various dielectric materials and a method for preparing a copper circuit by using the laser-induced liquid. The laser-induced liquid can be applied to various non-metal dielectric substrates, a pattern seed layer is obtained by using a laser-induced liquid phase deposition method subsequently, then a conductive pattern is manufactured through chemical copper plating, pretreatment of a substrate material is not needed, and the laser-induced liquid has the advantages of being high in adhesive force, high in conductivity and high in conductivity. And the thickness of the copper layer can be regulated and controlled by adjusting the copper plating time, the induction liquid is recycled, the technological process is simple, and large-breadth multi-dimensional manufacturing can be achieved. The surface of the dielectric material does not need to be pretreated, and the preparation of the graphic copper link has the advantages of high flexibility, micron-grade and submicron-grade precision, wide applicability of various dielectric materials and unlimited size of the dielectric materials; a series of problems that the technological process is tedious, the pattern flexibility is poor, a substrate material needs to be pretreated, and the size is limited are solved.

Description

Technical Field

[0001] The present invention relates to the field of copper plating technology, and in particular to a laser induction liquid suitable for various dielectric materials and a method for preparing copper circuits using the same. Background Art

[0002] Demand for fabricating high-precision copper circuits on dielectric surfaces is growing in electronics manufacturing, communications, automotive electronics, photovoltaic cells, medical devices, and aerospace. Examples include high-speed communication modules, high-precision sensors, high-frequency RF modules, wearable devices, high-density interconnect circuits, advanced semiconductor packaging, and BC photovoltaic cells. Laser processing, a maskless, flexible manufacturing technology, has seen rapid growth in recent years due to its advantages, including high precision, contactless processing, high manufacturing efficiency, and enhanced flexibility.

[0003] In the photovoltaic field, solar panel electrodes are currently manufactured using screen printing and laser transfer methods. With the pursuit of cost reduction and efficiency improvement, the trend toward silver removal and silver-free production is inevitable, with copper replacing silver as the preferred alternative. Lasers used to create copper electrodes on photovoltaic silicon substrates offer the advantages of high precision, reduced process steps, and improved production efficiency.

[0004] Currently, existing technologies use laser-induced liquid deposition technology to perform high-precision copper plating circuits on the surface of dielectric materials. However, this technology can only be performed on limited substrates, has low substrate compatibility, and is inefficient. Some technical solutions even have complex preparation steps, and the product has poor adhesion and conductivity, which greatly limits its application.

[0005] Therefore, it is necessary to develop an induction liquid that can directly perform laser-induced liquid deposition in the induction liquid, has micron-level precision, and can be used with a variety of dielectric materials, as well as to prepare copper circuits with strong adhesion based on the induction liquid. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a laser induction liquid applicable to a variety of dielectric materials and a method for preparing a copper circuit using the same.

[0007] According to one aspect of the present invention, a laser induction fluid suitable for a variety of dielectric materials is provided, including

[0008] A first mixed liquid and a monohydric alcohol, wherein the weight ratio of the first mixed liquid to the monohydric alcohol is 2-5:0.5-2; the first mixed liquid includes copper salt, copper oxide nanoparticles and dihydric alcohol, wherein the weight ratio of the copper salt, copper oxide nanoparticles and dihydric alcohol is 1.5-3.5:1-3:2.5-5.

[0009] The beneficial effects are as follows: the laser-induced liquid applied in the present invention can be applied to a variety of non-metallic dielectric substrates. A graphic seed layer is subsequently obtained using laser-induced liquid deposition, and then a conductive pattern is produced through chemical copper plating. No pretreatment of the substrate material is required, and the invention has the advantages of strong adhesion and conductivity. The thickness of the copper layer can be controlled by adjusting the copper plating time, the induction liquid can be recycled, the process flow is simple, and large-scale, multi-dimensional production is possible. Furthermore, the dielectric material surface does not require pretreatment, and the preparation of graphic copper links simultaneously possesses the advantages of high flexibility, micron- and submicron-level precision, wide applicability of various dielectric materials, and unlimited dielectric material size. This solves a series of problems such as complicated process flow, poor pattern flexibility, the need for substrate pretreatment, and size limitations.

[0010] In some embodiments, the copper salt is one or more of copper nitrate, copper sulfate, and copper acetate. Advantageously, the copper salts described herein have high solubility in organic solvents, enabling rapid formation of a uniform copper ion solution, improving reaction efficiency, and providing sufficient copper ion raw material for the reaction within the laser-induced light spot area. The copper salts completely decompose during the reaction, leaving few residual impurities, thereby helping to increase the copper content of the seed layer. Compared to chlorine-containing copper salts, the copper salts described herein are less toxic, offering safety and reliability.

[0011] In some embodiments, the monohydric alcohol is one or a combination of methanol and ethanol. This has the following beneficial effects: the monohydric alcohol in this application can effectively dissolve copper salts, improve reaction uniformity, and promote the dissolution and reaction of ionic reactants. As a small molecule alcohol, it has high reactivity and a certain degree of reducing power. Within the laser spot area, it can quickly reduce copper ions and form a copper seed layer. During the reaction, it is easily volatilized, leaving few residual impurities, which helps to increase the copper content of the seed layer.

[0012] According to another aspect of the present application, a method for preparing a copper circuit using the aforementioned laser-induced liquid is provided.

[0013] Step 1: immersing the dielectric material in the induction liquid or spreading the induction liquid on the surface of the dielectric material;

[0014] Step 2: irradiating a laser beam onto the surface of the dielectric material;

[0015] Step 3: Forming a conductive seed layer on the surface of the dielectric material according to the pattern preset by the software;

[0016] Step 4: Remove excess induction liquid from the surface of the dielectric material;

[0017] Step 5: Immerse the dielectric material with the conductive seed layer in step 4 in a chemical copper plating solution to obtain the desired copper circuit.

[0018] The method of the present invention has the following beneficial effects: it can increase the thickness of the copper layer in the pattern seed layer and enhance its conductivity. Because the laser induction liquid mentioned above is black, it has a strong absorption effect on light. Therefore, two mechanisms occur within the laser spot area: one is laser-induced photochemical liquid phase deposition, and the other is laser-induced photothermal chemical liquid phase deposition. During the laser induction process, the induction liquid in the local area of the spot absorbs photon energy and reduces copper ions to elemental metal. At the same time, the black induction liquid also absorbs a large amount of heat. When laser induction is carried out in an air environment, the copper salt is thermally decomposed into copper oxide and mixed with the copper oxide nanoparticles originally in the induction liquid. Monohydric alcohols are highly volatile when heated, and dihydric alcohols are organic solvents that easily dissolve copper salts. The combination of monohydric alcohols and dihydric alcohols maintains the fluidity of the induction liquid. When heated within the spot area, an oxidation reaction quickly occurs, generating aldehydes with strong reducing properties, which reduce copper oxide to elemental copper to form a seed layer, increasing the copper content of the seed layer. The absorbed heat also enhances the adhesion of the seed layer. Based on the combined effect of the two mechanisms, the induction liquid formula of the present invention is suitable for various dielectric materials and has strong compatibility. In addition, the laser induction liquid applied for by the present invention can be applied to a variety of non-metallic dielectric substrates, and the seed layer is subsequently obtained by the method of laser-induced liquid deposition, and then the conductive pattern is produced by chemical copper plating, without the need for pretreatment of the base material. It has the advantages of strong adhesion, conductivity and copper layer thickness can be regulated by adjusting the copper plating time, recycling of the induction liquid, simple process flow, and large-scale multi-dimensional production. Moreover, the surface of the dielectric material does not require pretreatment, and the preparation of the graphic copper link has the advantages of high flexibility, micron and submicron precision, wide applicability of various dielectric materials, and no restrictions on the size of the dielectric material, which solves a series of problems such as complicated process flow, poor pattern flexibility, the need for pretreatment of the base material, and size restrictions.

[0019] In some embodiments, the distance from the surface of the inducing liquid to the surface of the dielectric material in step 1 is 0.1 mm to 1.5 mm.

[0020] Its beneficial effects are: for substrate materials with low light absorption rates, higher power is required for multiple scans. Under the action of laser photothermal, the evaporation of the induction liquid is large. The thicker induction liquid can be replenished at any time by utilizing the fluidity of the induction liquid to prevent the phenomenon of burning out in the spot area; for substrate materials with higher light absorption rates, lower power is required and the number of scans is reduced, so the thickness of the induction liquid is reduced; in addition, if the thickness of the induction liquid is outside 0.1mm-1.5mm, it is very easy to burn out in the laser spot area, or the laser beam cannot pass through the induction liquid to act on the substrate.

[0021] In some embodiments, clean water is used to remove excess induction liquid from the dielectric surface in step 4. This has the beneficial effect of: the components of the induction liquid in the present invention have good compatibility with water, the induction liquid is easily dissolved in clean water, and the cost of clean water is low, so using clean water for cleaning has good economic benefits.

[0022] In some embodiments, the immersion time in step 5 is 15-20 minutes.

[0023] Its beneficial effects are: chemical copper plating on the seed layer on the surface of the dielectric material, the immersion time is 15-20 minutes, ensuring that the copper layer on the surface of the seed layer is uniform; if the immersion time is less than 15 minutes, pattern plating is missed, the copper plating layer is discontinuous, the plating surface has many pores, and the copper circuit is broken; if the immersion time is more than 20 minutes, overflow plating occurs, the plating surface has many pores, and the copper circuit is short-circuited.

[0024] In some embodiments, the temperature of the induction solution in step 1 is maintained at 10°C-40°C.

[0025] The beneficial effects are: maintaining the induction liquid temperature between 10°C and 40°C ensures more efficient seed layer induction under laser action while maintaining environmental stability. If the induction liquid temperature is less than 10°C, the seed layer quality will be poor and discontinuous due to the low temperature; if the induction liquid temperature is greater than 40°C, the induction liquid will be severely oxidized during laser induction due to the high temperature and easily deteriorate in the environment.

[0026] In some embodiments, the dielectric material in step 1 is glass, silicon wafer, ceramic, polyimide film, or polyester film. This has the beneficial effect of exhibiting low dielectric loss in high-frequency circuits, high resistivity, and effective electrical insulation to isolate current and prevent electrical short circuits. These materials can provide excellent electrical insulation, thermal stability, mechanical properties, and chemical stability, while being environmentally friendly and economically beneficial. These materials have broad application prospects in fields such as microelectronics, photovoltaics, optical devices, flexible electronics, and high-temperature devices.

[0027] In some embodiments, the laser beam wavelength is one of 515nm, 532nm, 1030nm, and 1064nm, with a pulse width of 20ns-600fs, a frequency of 50kHz-1000kHz, and a single pulse energy of 1μJ-0.15mJ. The beneficial effects are as follows: wavelengths of 515nm and 532nm are in the green light band, with higher photon energy and lower thermal energy. Within the laser spot area, the laser-induced photo-chemical liquid phase deposition mechanism is dominant, supplemented by the laser-induced photo-thermal-chemical liquid phase deposition mechanism; the wavelength of 1030nm is in the infrared light band, with higher thermal energy and lower photon energy. Within the laser spot area, the laser-induced photo-thermal-chemical liquid phase deposition mechanism is dominant, supplemented by the laser-induced photo-chemical liquid phase deposition mechanism; therefore, all four laser wavelengths can be used to induce a laser seed layer. The pulse widths range from 20ns to 600fs in descending order, and the thermal impact of the laser beam gradually decreases. When the processing accuracy is not high but the processing efficiency is high, a larger pulse width can be used; when processing brittle and hard materials or heat-sensitive materials with submicron or nanometer precision, a smaller pulse width can be used. The frequency is 50-1000kHz in order from small to large. The higher the frequency, the less heat accumulation and the smaller the heat-affected zone. It is suitable for processing brittle or heat-sensitive materials. For materials with low light absorption, the frequency needs to be lowered to maintain sufficient heat. The single pulse energy is 1μJ-0.15mJ in order from small to large, and its thermal impact also increases from small to large. For high-precision micro-nano processing, a lower single pulse energy is required, especially for heat-sensitive and brittle and hard materials; if it is to improve processing efficiency and used for large-scale production, the single pulse energy needs to be increased.

[0028] In some embodiments, the spot diameter of the laser beam is 5 μm-100 μm.

[0029] The beneficial effect is that the spot diameter of the laser beam is 5μm-100μm, which can achieve micron-level to submicron-level precision processing.

[0030] In some embodiments, the laser processing speed is 10 mm / s to 100 mm / s.

[0031] Its beneficial effect is that the laser processing speed can be adjusted according to the laser output power to improve the processing efficiency. If the laser processing speed is outside 10mm / s-100mm / s, there will be a large thermal impact or insufficient heat.

[0032] In some embodiments, the copper plating bath temperature is maintained at 50°C.

[0033] The beneficial effects are: the copper plating solution temperature is maintained at 50°C, ensuring that the copper plating solution is at the appropriate reaction temperature and ensuring the stability of the copper plating solution. If the temperature is lower than 50°C, the solution reaction becomes slower and the copper plating efficiency decreases; if the temperature is higher than 50°C, the solution reacts too quickly, the copper plating solution will undergo autocatalysis, and the solution will easily deteriorate.

[0034] According to another aspect of the present application, a copper circuit is manufactured according to the aforementioned method.

[0035] Its beneficial effects are: it is compatible with a variety of materials (such as polymers, ceramics, glass), has significant advantages such as high conductivity, high thermal conductivity, versatility, high stability and excellent high-frequency performance, and can be used in photovoltaics, flexible circuits, sensors, antennas, electromagnetic shielding and other devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a photo of the copper circuit product produced in Example 1 of the present application;

[0037] Figure 2 yes Figure 1 A magnified view of a copper circuit under a microscope;

[0038] Figure 3 This is a photo of the copper circuit product produced in Example 5 of the present application;

[0039] Figure 4 This is a photo of the copper circuit product produced in Example 9 of the present application;

[0040] Figure 5 This is a photo of the copper circuit product produced in Example 13 of the present application;

[0041] Figure 6 is a microscope photograph of the seed layer induced by the induction liquid laser in Example 1;

[0042] Figure 7 This is a microscope photograph of the seed layer induced by the induction liquid laser in Comparative Example 1; DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0044] 1. Preparation of laser induction fluid

[0045] Dissolve an appropriate amount of copper salt and copper oxide nanoparticles in ethylene glycol, stir and mix thoroughly, then add ethanol and mix thoroughly to obtain an induction solution. Refer to Tables 1-4 for specific components and amounts.

[0046] The raw materials copper salt, copper oxide nanoparticles, monohydric alcohol and dihydric alcohol can be purchased commercially.

[0047] 2. Preparation of copper plating solution

[0048] The component of copper plating solution is copper sulfate 20g / L, disodium edetate 35g / L, sodium hypophosphite 26g / L, polyethylene glycol 0.3g / L, 2-2 pyridine 0.02g / L, and sodium hydroxide is adjusted to pH 12.7. First copper sulfate is completely dissolved in order, then disodium edetate is added and stirred to completely dissolved, then sodium hypophosphite is slowly added and continuously stirred to dissolved, and it is 12.7 to add sodium hydroxide to regulate pH value, finally polyethylene glycol and 2-2 pyridine are added, deionized water is added after all dissolving and constant volume is carried out, finally filter impurity is filtered using filter paper, and is used for the copper plating of each embodiment. Raw materials are all commercially available.

[0049] In the induction liquid, both ethylene glycol and propylene glycol have high polarity and can dissolve many ionic compounds and polar substances. Both methanol and ethanol have high polarity and can dissolve many ionic compounds and polar substances, and both have reducing properties and can be used for reduction reactions. Therefore, in the following embodiments, ethylene glycol is used as an example of diol and ethanol is used as an example of monool. In the laser induction process of the present invention, the laser spot area is mainly based on the laser light-thermal-chemical mechanism. The beam is focused to generate heat, promote the decomposition of diols and monools, and reduce copper ions. Therefore, in the embodiment, the laser wavelength is 1064nm as an example, and the frequency, speed, and output power of the laser are adjusted according to the properties of different substrate materials. See Tables 1-4 for details.

[0050] Based on the above prepared induction solution and copper plating solution, the following copper circuit preparation method is used to make the following specific explanation:

[0051] Step 1: Immerse the dielectric material in the laser induction liquid or spread the induction liquid on the surface of the dielectric material;

[0052] Step 2: irradiating a laser beam onto the surface of the dielectric material;

[0053] Step 3: Forming a conductive seed layer on the surface of the dielectric material according to the pattern preset by the software;

[0054] Step 4: Remove excess induction liquid from the surface of the dielectric material;

[0055] Step 5: Immerse the dielectric material with the conductive seed layer in step 4 in a chemical copper plating solution to obtain the desired copper circuit.

[0056] 3. The dielectric materials of Examples 1-4 and Comparative Examples 1-4 are photovoltaic-grade silicon wafers;

[0057] Specific parameters are shown in Table 1: Place a silicon wafer with a size of 50mm×50mm×0.15mm in a liquid tank, pour in the induction liquid, control the distance from the induction liquid level to the material surface to be 0.5mm, use a laser to induce three times at a speed of 55mm / s according to the designed route, take it out of the induction liquid and rinse it with clean water, put it in the prepared copper plating solution for 20 minutes, take it out and rinse it, and obtain a copper circuit with a line width of 50μm.

[0058] The laser parameters used above are: a 20W picosecond laser with a wavelength of 1064nm, a pulse width of 15 picoseconds, a frequency of 950kHz, a focused spot diameter of 35μm, and a single pulse energy of 6.8μJ at an output power of 6.5W. Photovoltaic-grade silicon wafers were used as the substrate material, and the laser power and frequency were controlled to minimize the heat-affected zone and avoid material melting or thermal damage.

[0059] Except that monohydric alcohol was not used, other parameters of Comparative Examples 1-4 corresponded to and were the same as those of Examples 1-4.

[0060] Copper circuit board effect test: Test the resistance and adhesion within 1cm, where the adhesion level is 5B. Specific effect data are shown in Table 1.

[0061] The copper circuit product obtained in Example 1 is shown in FIG. Figure 1 and Figure 2 ; The specific examples of the seed layer induced by the induction liquid laser in Example 1 and the seed layer induced by the induction liquid laser in Comparative Example 1 are shown in FIG. Figure 6 and Figure 7 , it can be seen that the seed layer obtained by the induction liquid of Example 1 is significantly larger than that of the induction liquid of Comparative Example 1, and the conductivity of the copper wire of Example 1 is improved by 30%-40% compared with that of Comparative Example 1. In addition, based on the same comparison method, the comparison results between the following other embodiments and comparative examples are similar to those of Example 1 and Comparative Example 1, and will not be repeated hereafter. This shows that the use of monohydric alcohol and dihydric alcohol in combination maintains the fluidity of the induction liquid, and an oxidation reaction occurs rapidly when heated in the spot area to generate aldehydes with strong reducing properties, reducing copper oxide to copper element to form a seed layer, thereby increasing the copper content of the seed layer, and the absorbed heat will also enhance the adhesion of the seed layer. Based on the combined effect of the two mechanisms of action, the induction liquid formula of the present invention is suitable for various dielectric materials and has strong compatibility.

[0062] Table-1 Specific example parameters when photovoltaic-grade silicon wafers are used as dielectric materials

[0063]

[0064]

[0065] In Examples 1-4 of Table 1, photovoltaic-grade silicon wafers were used as the substrate material. Copper nitrate, copper sulfate, copper acetate, and a combination of copper nitrate and copper acetate were used as the copper salts in the laser-induced liquid. Ethylene glycol was used as the diol, and ethanol was used as the monool. With ethylene glycol as the primary solvent, copper nitrate has a higher solubility than copper sulfate and copper acetate, resulting in a lower content of copper sulfate and copper acetate in the copper salts compared to copper nitrate. With all other quantities remaining constant, a laser-induced seed layer was then followed by electroless copper plating to produce a conductive pattern. Due to the lower solubility of copper sulfate and copper acetate, the resulting laser-induced seed layer was of poor quality, resulting in a thin copper coating within the specified time, and consequently, a high resistance within 1 cm of the conductive pattern.

[0066] In comparative examples 1-4, ethanol was not added to the induction solutions of different types of copper salts. With other parameters unchanged, the resistance within 1 cm of the conductive pattern finally obtained was much greater than that of the induction solution containing ethanol, indicating that ethanol has a significant impact on the quality of the seed layer during laser induction.

[0067] Since photovoltaic-grade silicon wafers are only 0.15 mm thick and very prone to brittle cracking, smaller laser power and single pulse energy are used to reduce the thermal impact of the laser.

[0068] 4. Alumina ceramics are used as dielectric materials in Examples 5-8 and Comparative Examples 5-8

[0069] Specific parameters are shown in Table 2: Place alumina ceramics with a size of 50mm×50mm×1mm in a liquid tank, pour in the induction liquid, control the distance from the induction liquid surface to the material surface to be 1mm, use a laser to induce 4 times at a speed of 50mm / s according to the designed route, take it out of the induction liquid and rinse it with clean water, put it in the prepared copper plating solution for 20 minutes, take it out and rinse it, and obtain a copper circuit with a line width of 240μm. The resistance within 1cm is measured to be less than 1Ω, and the adhesion level is 5B.

[0070] The laser parameters used above are: a 20W picosecond laser with a wavelength of 1064nm, a pulse width of 15 picoseconds, a frequency of 450kHz, a focused spot diameter of 50μm, an output power of 15.4W, and a single pulse energy of 34.2μJ. Alumina ceramics have a low absorption rate for light at a wavelength of 1064nm, high hardness, and are difficult to process. Material removal requires high energy density, requiring high laser power.

[0071] Except for whether monohydric alcohol is used, other parameters of Comparative Examples 5-8 correspond to and are the same as those of Examples 5-8.

[0072] Copper circuit effect test: Test the resistance and adhesion within 1cm, where the adhesion level is 5B. Specific effect data is shown in Table 2.

[0073] The copper circuit product obtained in Example 5 is shown in FIG. Figure 3 Table-2 Parameters of specific embodiments of dielectric materials using alumina ceramics

[0074]

[0075]

[0076] In Examples 5-8 of Table 2, alumina ceramic was used as the substrate material. Copper salts selected for the laser-induced liquid included copper nitrate, copper sulfate, copper acetate, and a combination of copper nitrate and copper acetate. Ethylene glycol was selected as the diol, and ethanol was selected as the monool. With ethylene glycol as the primary solvent, copper nitrate has a higher solubility than copper sulfate and copper acetate, resulting in a lower content of copper sulfate and copper acetate in the copper salts compared to copper nitrate. With all other quantities remaining constant, a laser-induced seed layer was then followed by electroless copper plating to produce a conductive pattern. Due to the lower solubility of copper sulfate and copper acetate, the quality of the laser-induced seed layer was poor, resulting in a thinner copper coating within the specified time, leading to a higher resistance within 1 cm of the conductive pattern.

[0077] In comparative examples 5-8, ethanol was not added to the induction solutions of different types of copper salts. When other parameters remained unchanged, the resistance within 1 cm of the conductive pattern finally obtained was much greater than that of the induction solution containing ethanol, indicating that the addition of ethanol significantly improved the quality of the laser-induced seed layer.

[0078] Alumina ceramics have strong heat resistance, so the laser power and single pulse energy are large, and greater heat is obtained to improve the quality of the seed layer.

[0079] V. In Examples 9-12 and Comparative Examples 9-12, the dielectric material used is polyimide film;

[0080] Specific parameters are shown in Table 3. A polyimide film with a size of 50mm×50mm×0.2mm is placed in a liquid tank, and the induction liquid is poured in. The distance from the liquid surface of the induction liquid to the material surface is controlled to be 1mm. The laser is used to induce the film 5 times at a speed of 55mm / s according to the designed route. The film is taken out of the induction liquid and rinsed with clean water. It is placed in the prepared copper plating solution for 20 minutes, taken out and rinsed to obtain a copper circuit with a line width of 120μm.

[0081] The laser parameters used above are: a 20W picosecond laser with a wavelength of 1064nm, a pulse width of 15 picoseconds, a frequency of 600kHz, a focused spot diameter of 50μm, an output power of 4.8W, and a single pulse energy of 8μJ. Polyimide film is susceptible to thermal decomposition or carbonization under high-energy laser light, requiring lower laser power.

[0082] Except that monohydric alcohol is not used, the other parameters of Comparative Examples 9-12 correspond to and are the same as those of Examples 9-12.

[0083] Copper circuit effect test: Test the resistance and adhesion within 1cm, where the adhesion level is 5B. Specific effect data are shown in Table 3.

[0084] The copper circuit product obtained in Example 9 is shown in FIG. Figure 4 .

[0085] Table 3: Specific example parameters when polyimide film is selected as the dielectric material

[0086]

[0087]

[0088] In Examples 9-12 of Table 3, a polyimide film was used as the substrate material. Copper nitrate, copper sulfate, copper acetate, and a combination of copper nitrate and copper acetate were used as the laser-induced liquid, respectively. Ethylene glycol was used as the diol, and ethanol was used as the monool. With ethylene glycol as the primary solvent, copper nitrate has a higher solubility than copper sulfate and copper acetate, resulting in a lower content of copper sulfate and copper acetate in the copper salts compared to copper nitrate. With other quantities remaining constant, a laser-induced seed layer was then followed by electroless copper plating to produce a conductive pattern. Due to the lower solubility of copper sulfate and copper acetate, the quality of the laser-induced seed layer was poor, resulting in a thinner copper coating within the specified time, leading to a higher resistance within 1 cm of the conductive pattern.

[0089] In comparative examples 9-12, ethanol was not added to the induction solutions of different types of copper salts. When other parameters remained unchanged, the resistance within 1 cm of the conductive pattern finally obtained was much greater than that of the induction solution containing ethanol, indicating that ethanol has a significant impact on the quality of the seed layer during laser induction.

[0090] Polyimide film can withstand high temperatures, but large thermal effects can cause carbonization of the material, so smaller laser power is required.

[0091] VI. Examples 13-16 and Comparative Examples 13-16: Transparent Glass as Dielectric Material

[0092] Specific parameters are shown in Table 4: Place a glass with a size of 50mm×50mm×1mm in a liquid tank, pour in the induction liquid, control the distance from the induction liquid level to the material surface to be 1mm, use a laser to induce 4 times at a speed of 50mm / s according to the designed route, take it out of the induction liquid and rinse it with clean water, put it in the prepared copper plating solution for 20 minutes, take it out and rinse it, and obtain a copper circuit with a line width of 150μm.

[0093] The laser parameters are: a 20W picosecond laser with a wavelength of 1064nm, a pulse width of 15 picoseconds, a frequency of 100kHz, a focused spot diameter of 50μm, an output power of 7.5W, and a single pulse energy of 75μJ. Transparent glass has a low absorption rate for light at a wavelength of 1064nm, so the laser power needs to be increased appropriately; excessive power can easily cause cracks.

[0094] Except that monohydric alcohol was not used, the other parameters of Comparative Examples 13-16 corresponded to and were the same as those of Examples 13-16.

[0095] Copper circuit board effect test: Test the resistance and adhesion within 1cm, where the adhesion level is 5B. Specific effect data are shown in Table 4.

[0096] The copper circuit product obtained in Example 13 is shown in FIG. Figure 5 .

[0097] Table 4: Specific parameters of the embodiment when transparent glass is used as the dielectric material

[0098]

[0099]

[0100] In Examples 13-16 in Table 4, glass was used as the substrate material. Copper nitrate, copper sulfate, copper acetate, and a combination of copper nitrate and copper acetate were used as the laser-induced liquid, respectively. Ethylene glycol was used as the diol, and ethanol was used as the monool. With ethylene glycol as the primary solvent, copper nitrate has a higher solubility than copper sulfate and copper acetate, resulting in a lower content of copper sulfate and copper acetate in the copper salts compared to copper nitrate. With other quantities remaining constant, a laser-induced seed layer was then followed by electroless copper plating to produce a conductive pattern. Due to the lower solubility of copper sulfate and copper acetate, the quality of the laser-induced seed layer was poor, resulting in a thin copper coating within the specified time, and consequently, a high resistance within 1 cm of the conductive pattern.

[0101] In comparative examples 13-16, ethanol was not added to the induction solutions of different types of copper salts. When other parameters remained unchanged, the resistance within 1 cm of the conductive pattern finally obtained was much greater than that of the induction solution containing ethanol, indicating that the addition of ethanol significantly improved the quality of the laser-induced seed layer.

[0102] Glass is very brittle and has a low absorption rate for 1064nm laser. Therefore, by reducing the frequency and increasing the energy of single pulse, the heat absorption of glass is increased, thereby enhancing the laser photothermal effect and improving the quality of the seed layer.

[0103] As can be seen from the above examples and comparative examples, the laser induction liquid mentioned above in this application is black, so it has a strong absorption effect on light. Therefore, two mechanisms of action occur in the laser spot area: one is laser-induced photo-chemical liquid deposition, and the other is laser-induced photo-thermal-chemical liquid deposition. During the laser induction process, the induction liquid in the local area of the spot absorbs photon energy and reduces copper ions to metal elements; at the same time, the black induction liquid also absorbs a large amount of heat. When laser induction is carried out in an air environment, the copper salt is thermally decomposed into copper oxide and mixed with the copper oxide nanoparticles originally in the induction liquid. Monohydric alcohol has strong volatility when heated, and dihydric alcohol is an organic solvent that easily dissolves copper salts. The combination of monohydric alcohol and dihydric alcohol maintains the fluidity of the induction liquid. When heated in the spot area, an oxidation reaction quickly occurs, generating aldehydes with strong reducing properties, which reduce copper oxide to copper element to form a seed layer, increasing the copper content of the seed layer. The absorbed heat also enhances the adhesion of the seed layer. Based on the combined effect of the two mechanisms of action, the induction liquid formula in this application is suitable for various dielectric materials and has strong compatibility. In addition, the laser induction liquid of this application can be applied to a variety of non-metallic dielectric substrates, and the seed layer is subsequently obtained by the method of laser-induced liquid deposition, and then the conductive pattern is made by chemical copper plating, without the need for pretreatment of the substrate material. It has the advantages of strong adhesion, conductivity and copper layer thickness can be regulated by adjusting the copper plating time, recycling of the induction liquid, simple process flow, and large-scale multi-dimensional production. Moreover, the surface of the dielectric material does not require pretreatment, and the preparation of the graphic copper link has the advantages of high flexibility, micron and submicron precision, wide applicability of various dielectric materials, and unrestricted size of the dielectric material, which solves a series of problems such as complicated process flow, poor pattern flexibility, need for pretreatment of the substrate material, and size restrictions.

[0104] The above are only some embodiments of the present invention. It should be pointed out that for ordinary technicians in this field, other variations and improvements can be made without departing from the creative concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A laser induction fluid suitable for various dielectric materials, characterized in that: include A first mixed liquid and a monohydric alcohol, wherein the weight ratio of the first mixed liquid to the monohydric alcohol is 2-5:0.5-2; The first mixed solution includes copper salt, copper oxide nanoparticles and diol, wherein the weight ratio of copper salt, copper oxide nanoparticles and diol is 1.5-3.5:1-3:2.5-5.

2. The laser induction liquid applicable to various dielectric materials according to claim 1, characterized in that: The copper salt is one or more combinations of copper nitrate, copper sulfate and copper acetate.

3. The laser induction liquid applicable to various dielectric materials according to claim 1, characterized in that: The monohydric alcohol is one or a combination of methanol and ethanol.

4. A method for preparing a copper circuit using the laser induction liquid according to any one of claims 1 to 3, characterized in that: Step 1: immersing the dielectric material in the induction liquid or spreading the induction liquid on the surface of the dielectric material; Step 2: irradiating a laser beam onto the surface of the dielectric material; Step 3: Forming a conductive seed layer on the surface of the dielectric material according to the pattern preset by the software; Step 4: Remove excess induction liquid from the surface of the dielectric material; Step 5: Immerse the dielectric material with the conductive seed layer in step 4 in a chemical copper plating solution to obtain the desired copper circuit.

5. The method according to claim 4, characterized in that In step 1, the distance from the surface of the inducing liquid to the surface of the dielectric material is 0.1 mm to 1.5 mm.

6. The method according to claim 4, characterized in that In step 4, clean water is used to remove excess induction liquid on the surface of the dielectric.

7. The method according to claim 4, characterized in that The immersion time in step 5 is 15-20 minutes.

8. The method according to claim 4, characterized in that The temperature of the induction solution in step 1 is maintained at 10°C-40°C.

9. The method according to claim 4, characterized in that In step 1, the dielectric material is glass, silicon wafer, ceramic, polyimide film or polyester film.

10. The method according to claim 4, characterized in that The laser beam has a wavelength of one of 515 nm, 532 nm, 1030 nm and 1064 nm, a pulse width of 20 ns-600 fs, a frequency of 50 kHz-1000 kHz, and a single pulse energy of 1 μJ-0.15 mJ.

11. The method according to claim 4, characterized in that The spot diameter of the laser beam is 5 μm-100 μm.

12. The method according to claim 4, characterized in that The laser processing speed is 10 mm / s-100 mm / s.

13. The method according to claim 4, characterized in that The temperature of the copper plating solution was maintained at 50°C.

14. Copper circuit produced according to the method of claims 4-13.

Images