Method for metallizing glass substrate by adopting sol-gel method

Abstract

The invention discloses a method for metallizing a glass substrate by adopting a sol-gel method, relates to the technical field of circuit boards, and aims to improve the bonding problem of the glass substrate and a metal layer in the prior art. According to the method provided by the invention, the bonding force between the metal layer and the glass substrate is stronger through the processes of hydrolysis, condensation chemical reaction, high-temperature sintering and the like, equipment required by the method provided by the invention is simple, the process is stable and reliable, and the process cost of glass metallization is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards. Specifically, it is a preparation method for metallizing a glass substrate by the sol-gel method. Background Art

[0002] With the gradual increase in the demand for AI computing power and the high complexity of hardware circuits, both the previously widely used PCB organic substrates and the TSV technology for improving packaging density will become the bottlenecks restricting the production of high-performance computing power chips such as AI chips within a foreseeable period. Due to its natural electrical properties, excellent mechanical properties, good thermal conductivity, and low coefficient of thermal expansion, the glass substrate has become the focus of research for substrates of new advanced packaging technologies.

[0003] Glass is an amorphous inorganic non-metallic material, and its main components include silicon dioxide and other oxides, such as silicate double salts. The chemical composition of ordinary glass can be Na2SiO3, CaSiO3, SiO2, etc. The structure of glass is similar to that of quartz crystals, with silicon-oxygen tetrahedrons as the structural units. These polyhedrons are disorderly arranged in three-dimensional space to form a network structure. During the high-temperature sintering process, because the glass itself has a network structure of disorderly arranged silicon-oxygen tetrahedrons in three-dimensional space, the metal ions in the sol-gel can replace the metal ions such as Na and Ca filled in the silicon-oxygen tetrahedrons, further strengthening the bonding force between the metal layer and the glass substrate.

[0004] Due to the smooth surface of the glass, the adhesion of the metal layer to it is low, and it is easy to cause the metal layer to peel off and curl. Therefore, how to metallize the surface of the glass substrate is a major difficulty in the process. Before electroplating, the seed layer needs to be sputtered to form a coating first. According to HarborSemi, sputter coating mainly forms a plasma on the surface of the target, and uses the energetic particles in the plasma to bombard the target surface, so that the sputtered particles form a coating on the substrate surface, that is, a method of forming a film by using the sputtering phenomenon. The metal layer formed by magnetron sputtering is generally nanoscale. The glass substrate still needs to be electroplated with water to thicken the metal layer later. The cost of magnetron sputtering is high, and the yield of the bonding force between the metal layer formed by magnetron sputtering and the water-based electroplated layer is low. Summary of the Invention

[0005] To solve the above-mentioned problems, the present invention provides a technical solution as follows: A nano-based sol containing metal ions is uniformly coated on the surface of the glass substrate, and processes such as hydrolysis, condensation chemical reaction, and high-temperature sintering are carried out.

[0006] The key point of the sol-gel method is to form stable sol and gel, so metal salts, solvents and chelating agents should be reasonably selected. Organic matter containing metal ions forms a stable transparent sol system in the solution. After aging, the sol particles slowly polymerize to form a gel with a three-dimensional network structure. The gel network is filled with solvents that have lost fluidity to form a gel. The gel is dried and sintered at a high temperature of 400-500°C to prepare a nano-substructure material of metal oxide. Then the temperature is controlled at 600-800°C and hydrogen and other reducing gases are introduced to reduce the metal oxide to a metal element. After annealing, the metal element can be rearranged and condensed into a compact metal layer on the glass substrate.

[0007] The specific technical steps include:

[0008] 1. Preparation of sol-gel precursor

[0009] ① Take nitrate as metal salt and deionized water as solvent, weigh a certain amount of nitrate and dissolve it in deionized water, and stir with a magnetic stirrer until it is completely dissolved; the nitrate includes but is not limited to nickel nitrate, copper nitrate, silver nitrate, etc., and the concentration of the metal salt is controlled at 10-20wt%;

[0010] ② Weigh a chelating agent according to a molar ratio of nitrate to chelating agent citric acid of 1-2:1-2 (preferably 1:1) and add it to the above solution, continue stirring until the solution is clear and transparent, then slowly drop ammonia water while stirring to adjust the pH to between 6 and 7 (when the precipitate in the solution disappears slowly with stirring), and perform ultrasonic treatment for 10 minutes; the chelating agent includes but is not limited to citric acid, ethylene glycol, glutaraldehyde, arabinose, etc.

[0011] ③ Transfer the above solution to a glass beaker, put it into an oven, and dry it at 80-95°C for 1-2 hours until the water content in the solution gradually decreases and becomes semi-fluid. The baking temperature and time conditions are preferably 90°C for 2 hours.

[0012] 2. The steps for surface modification of glass substrate are as follows

[0013] ①Evenly coat the above gel on the surface of the glass substrate with a coating thickness of about 0.5-1mm.

[0014] ② Place the prepared glass substrate in an oven and dry it at 90°C-95°C for 1-3 hours. After the solvent is completely evaporated, a layer of dry gel will be attached to the surface of the glass substrate. The baking temperature and time conditions are preferably 95°C for 3 hours.

[0015] ③ Place the above glass substrate in a high-temperature tube furnace. Under the protection of an inert gas, control the temperature to sinter at 400 - 550 °C until no white gas is released from the horizontal tube furnace. Then, turn off the furnace under the protection of the inert gas and cool it to room temperature. The inert gas includes but is not limited to nitrogen, argon, helium, etc. The sintering temperature is preferably 500 °C;

[0016] ④ Introduce a reducing gas (such as hydrogen) into the high-temperature tube furnace for homogenization annealing. The annealing process is to heat up to 600 - 800 °C and hold for 7 - 10 h after placing the glass substrate, and then cool it to room temperature with the furnace under the atmosphere of the reducing gas. The annealing temperature and holding time are preferably 650 °C and 10 h;

[0017] ⑤ After the cooled glass substrate has a metal layer attached to its surface, conduct a bonding strength test on it.

[0018] The beneficial effects of the present invention are as follows: A metal layer (such as a nickel layer) is sintered and solidified on the surface layer of the glass substrate by the sol-gel method, and the bonding strength between the metal layer (such as the nickel layer) and the glass substrate is strong; the required equipment is simple, the process is stable and reliable, and the process cost of glass metallization is effectively reduced. Description of the Drawings

[0019] Figure 1 It is the XRD spectrum of the nickel layer in Example 1 and 2, and the red one is the standard spectrum of nickel.

[0020] Figure 2 In it, 2a is the bare glass substrate; 2b is the glass substrate with a nickel layer attached to its surface in Example 1; 2c is the glass substrate with a nickel layer attached to its surface in Example 2.

[0021] Figure 3 In it, 3a and 3b are the glass substrates after high-temperature baking in Example 1 and 2 respectively.

[0022] Figure 4 In it, 4a and 4b are the glass substrates after the cross-cut test in Example 1 and 2 respectively. Detailed Embodiments

[0023] Example 1

[0024] Weigh 10 mmol of nickel nitrate and dissolve it in 60 ml of deionized water. Stir with a magnetic stirrer until completely dissolved. Add 10 mmol of citric acid to the above solution and continue stirring until a clear and transparent solution is obtained. Then, while stirring, slowly dropwise add ammonia water to adjust the pH value between 6 and 7 (when the speed at which the precipitate appearing in the solution disappears with stirring becomes slower). Transfer the above solution to a glass beaker, place it in an oven, and dry it at 90 °C for 2 h until the moisture in the solution gradually decreases to a semi-fluid gel. Uniformly coat the above gel on the surface of the glass substrate and place it in the oven to bake again at 95 °C for 3 h until a bright green dry gel adheres to the surface of the glass substrate. Transfer the glass substrate to a high-temperature tube furnace. Under the protection of nitrogen, sinter it at a controlled temperature of 550 °C until no white gas is released in the horizontal tube furnace. After turning off the furnace and cooling under nitrogen protection, change the atmosphere to hydrogen, heat up to 650 °C and hold for 10 h, and then cool down to room temperature with the furnace in the hydrogen atmosphere.

[0025] Example 2

[0026] Weigh 10 mmol of nickel nitrate and dissolve it in 60 ml of deionized water. Stir with a magnetic stirrer until completely dissolved. Add 10 mmol of ethylene glycol citric acid to the above solution and continue stirring until a clear and transparent solution is obtained. Then, while stirring, slowly dropwise add ammonia water to adjust the pH value between 6 and 7 (when the speed at which the precipitate appearing in the solution disappears with stirring becomes slower). Transfer the above solution to a glass beaker, place it in an oven, and dry it at 95 °C for 1.5 h until the moisture in the solution gradually decreases to a semi-fluid gel. Uniformly coat the above gel on the surface of the glass substrate and place it in the oven to bake again at 95 °C for 3 h until a bright green dry gel adheres to the surface of the glass substrate. Transfer the glass substrate to a high-temperature tube furnace. Under the protection of argon, sinter it at a controlled temperature of 450 °C until no white gas is released in the horizontal tube furnace. After turning off the furnace and cooling under argon protection, change the atmosphere to hydrogen, heat up to 650 °C and hold for 10 h, and then cool down to room temperature with the furnace in the hydrogen atmosphere.

[0027] Figure 2 In [it], 2a is the bare glass substrate used, and 2b and 2c are the glass substrates with nickel layers attached to the surface by the technology of the present invention in Example 1 and Example 2 respectively. It can be clearly seen that there is a silver-white metal layer on the glass surface, proving that the nickel formed by sintering with the sol-gel method has successfully adhered to the substrate. Perform XRD testing on the metal layer on the surface of the glass substrate. The XRD spectrum is as Figure 1As shown, it can be seen that the diffraction peaks of the nickel layers made from the two samples correspond to the peak positions of standard nickel, and there are no impurity diffraction peaks of the second phase, indicating that the prepared nickel is elemental nickel and its phase is a stable body-centered cubic structure. The intensity of the diffraction peaks is significantly higher than that of the standard spectrum and is relatively sharp, indicating that there are many crystal grains and good crystallinity. This may be due to the reason that the lattice of nickel has undergone rearrangement during the high-temperature annealing process.

[0028] The bonding strength between the nickel layer and the substrate was tested by high-temperature baking test and cross-cut test. According to the conventional temperature and time requirements for chip soldering, the high-temperature baking test was set to bake at 320 °C on a hot stage for 5 minutes, and the results are as Figure 3 shown. The nickel layer on the surface of the glass substrate is in good condition, and there are no situations such as metal layer peeling, wrinkling, blistering, blackening, and cracking, and there is no obvious change in the nickel layer before and after baking. The cross-cut test is to use a cross-cut knife to cut through the nickel layer on the nickel layer surface according to the cross method, and then use 3M tape to closely adhere to the nickel layer and quickly tear it with a vertical force. Figure 4 It can be seen that the nickel layer in the grid does not peel off, and there is no warping or peeling at the edge of the scratch, proving that the bonding strength between the nickel layer and the substrate is good.

[0029] A preparation method and its application for metallizing a glass substrate by the sol-gel method are provided. A metal layer is prepared by sintering and curing on the surface layer of the glass substrate by the gel method. The bonding strength between the metal layer and the glass substrate is strong, and the bonding strength between the metal layer and the aqueous electroplating layer is good. The required equipment is simple, replacing the process of magnetron sputtering, and effectively reducing the process cost of glass metallization.

Claims

1. A method for metallizing a glass substrate using a sol-gel method, characterized in that the method comprises the following steps:

1. Preparation of sol-gel precursor 1.1) Weigh nitrate and dissolve it in deionized water, stirring with a magnetic stirrer until it is completely dissolved to prepare a nitrate solution with a concentration of 10-20wt%; 1.2) weighing a chelating agent in a molar ratio of nitrate to chelating agent of 1-2:1-2 and adding it to the above solution, continuing to stir until the solution is clear and transparent, then adjusting the pH to between 6-7, and performing ultrasonic treatment; 1.3) Transfer the above solution into an oven and dry it at 80-95°C until the water content in the solution gradually decreases and becomes semi-fluid; 2. Surface modification of glass substrate 2.1) The gel is evenly coated on the surface of the glass substrate with a coating thickness of about 0.5-1 mm; 2.2) drying the prepared glass substrate at 90°C-95°C, and after the solvent is completely evaporated, a layer of dry gel will be attached to the surface of the glass substrate; 2.3) Sinter at 400-550°C under inert gas protection until no more white gas is released, and then cool to room temperature under inert gas protection; 2.4) Then, a reducing gas is introduced to perform homogenization annealing treatment, the temperature is raised to 600-800°C and kept at this temperature for 7-10 hours, and the furnace is continuously cooled to room temperature in the reducing gas atmosphere.

2. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: The nitrate is one or more of nickel nitrate, copper nitrate and silver nitrate.

3. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: The chelating agent is one or more of citric acid, ethylene glycol, glutaraldehyde and arabinose.

4. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: The drying temperature in step 1.3) is 90°C.

5. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: The baking temperature in step 2.2) is 95° C. and the drying time is 3 h.

6. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: The inert gas in step 2.3) is nitrogen, argon or helium.

7. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: The sintering temperature in step 2.3) is preferably 500°C.

8. The method for metallizing a glass substrate by a sol-gel method according to claim 1, characterized in that: In step 2.4), the annealing temperature is 650° C. and the holding time is 10 h.

9. A metallized glass substrate prepared by the method for metallizing a glass substrate by the sol-gel method as claimed in claim 1.

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