TEC (Thermoelectric Cooler) for prefabricating gold-tin solder and preparation process thereof

Abstract

The invention discloses a TEC (Thermoelectric Cooler) for prefabricating gold-tin solder and a preparation process thereof, and relates to the technical field of thermoelectric refrigerators. Patterning manufacturing is separated during gold electroplating, solder mask manufacturing is carried out before gold plating, damage to the aluminum nitride ceramic substrate caused by subsequent laser gold scanning or gold and tin overflowing caused by non-uniform gold scanning are avoided, corresponding surface treatment is carried out on activation before gold plating, and the quality of the aluminum nitride ceramic substrate is improved. A product with an extremely fine line is completely electrolyzed and activated to improve the binding force of a nickel-gold layer, so that the reliability and yield of a power semiconductor device connecting material are further improved, the reliability is higher, and the defects of poor binding force and poor patterns caused by raw materials, processes and the like in the machining process can be reduced; the gold-tin solder layer is prefabricated in advance, so that the fine design of the pattern is improved, the electroplated platinum layer is used for patterned solder resist, the gold scanning step is omitted, and the yield is improved.

Description

A pre-formed gold-tin solder TEC and its preparation process Technical Field

[0001] This invention relates to the field of thermoelectric cooler technology, specifically a TEC with pre-formed gold-tin solder and its preparation process. Background Technology

[0002] Thermoelectric coolers (TECs) are solid-state heat pumps based on the Peltier effect. Due to their advantages such as small size, high controllability, and no moving parts, they are widely used in laser temperature control, precision instrument cooling, and optoelectronic module temperature control. The interface connection process is a key technology for the efficient and reliable integration of TECs into systems.

[0003] Existing technologies such as thermally conductive adhesives, conductive adhesives, and traditional tin-based solder paste (e.g., SnAgCu) reflow processes suffer from adverse effects such as high thermal resistance, high porosity, and poor reliability. Gold-tin eutectic bonding, on the other hand, is costly, complex, and requires extremely high material surface flatness, making it difficult to simultaneously meet the "high thermal conductivity, high strength, high reliability, low thermal resistance, and hermeticity" requirements of high-power, long-life optoelectronic devices for TEC interfaces. Furthermore, during pattern fabrication, laser gold sweeping can damage the aluminum nitride ceramic substrate or result in uneven gold sweeping, leading to gold-tin overflow. Therefore, this invention proposes a pre-fabricated gold-tin solder TEC and its fabrication process to solve the aforementioned technical problems. Summary of the Invention

[0004] The purpose of this invention is to provide a TEC with pre-formed gold-tin solder and its preparation process to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a process for preparing a TEC with pre-formed gold-tin solder, comprising the following steps: S1: taking an aluminum nitride ceramic substrate, magnetron sputtering titanium copper to form a titanium copper layer; S2: sequentially passing the aluminum nitride ceramic substrate obtained in step S1 through film lamination, exposure, and development for the first pattern transfer; S3: immersing the aluminum nitride ceramic substrate obtained in step S2 into a copper plating solution for copper plating to form a thickened copper layer; S4: grinding and sandblasting the aluminum nitride ceramic substrate obtained in step S3; S5: first immersing the aluminum nitride ceramic substrate obtained in step S4 into a nickel plating solution to form a nickel layer, and then sequentially passing it through film lamination, exposure, and development for the first pattern transfer; S6: The aluminum nitride ceramic substrate obtained in step S5 is immersed in a platinum plating solution to form a platinum (Pt) layer; S7: The aluminum nitride ceramic substrate obtained in step S6 is stripped using a stripping solution; S8: The aluminum nitride ceramic substrate obtained in step S7 is sequentially subjected to photoresist coating, photolithography, and development, and then subjected to plasma treatment; S9: The aluminum nitride ceramic substrate obtained in step S8 is immersed in a gold-tin plating solution to form a pre-formed gold-tin solder layer; S10: The aluminum nitride ceramic substrate obtained in step S9 is sequentially subjected to resist removal and etching to obtain TEC.

[0006] Furthermore, the aluminum nitride ceramic substrate is cleaned and dried before use in step S1. The specific cleaning process steps are as follows: the aluminum nitride ceramic substrate is sequentially subjected to alkaline washing, spray water washing, acid washing, spray water washing again, and ultrasonic water washing. The specific drying process steps are as follows: hot air drying is carried out in a nitrogen atmosphere at a temperature of 140~160℃ for 2~4 hours.

[0007] Furthermore, in step S1, the specific process steps of the magnetron sputtering are as follows: using a dual-target interactive sputtering process, first depositing titanium to form a titanium layer, and then depositing copper to form a copper layer. The thickness of the titanium layer is 0.1~0.2μm, and the thickness of the copper layer is 1.5~3μm.

[0008] Furthermore, in step S2, the specific process of applying the film is as follows: a dry film is applied using a laminating machine, and the thickness of the dry film is 35~40μm.

[0009] Furthermore, in step S3, the electroplating copper solution comprises the following components by mass: 180~220g / L sulfuric acid, 50~80g / L copper sulfate, and 40~60ml / L sodium potassium tartrate.

[0010] Furthermore, the thickened copper layer is plated with a thickness increased by 25% to 35% based on a single-sided copper thickness of 20 to 30 μm, leaving a single-sided thickness of 3 to 5 μm for grinding.

[0011] Furthermore, in step S4, the specific process steps of the grinding and sandblasting are as follows: a horizontal grinding process is adopted, using a ceramic brush and a non-woven brush for grinding in sequence; a horizontal wet blasting process is adopted for sandblasting, with a 500~1000 mesh diamond grinding wheel as the blasting medium, an upper pressure of 1.2~1.5MPa, a lower pressure of 1.0~1.2MPa, and a linear speed of 0.8~1.5m / min.

[0012] Furthermore, in step S5, the electroplating nickel solution comprises the following components by mass: 70-90 g / L nickel sulfate, 10-14 g / L nickel chloride, 30-40 g / L boric acid, 3-7 ml / L plating starter, and 3-5 ml / L wetting agent, using deionized water as the solvent.

[0013] Furthermore, in step S5, the specific process steps for electroplating gold are as follows: the aluminum nitride ceramic substrate obtained in the previous step is activated by positive and negative pulse electrolysis for 10~30s, washed with water, and then sequentially immersed in the pre-plating gold solution and the electroplating gold solution for electroplating gold.

[0014] Furthermore, the thickness of the nickel layer is 3~7μm.

[0015] Furthermore, the thickness of the gold layer is 1.2~1.5μm.

[0016] Furthermore, the electroplating platinum solution comprises the following components by mass: 3-5 g / L of chloroplatinic acid hexahydrate, 10-30 g / L of diammonium hydrogen phosphate, and 80-100 g / L of disodium hydrogen phosphate, using deionized water as the solvent.

[0017] Furthermore, the thickness of the platinum layer is 0.2~0.4μm.

[0018] Furthermore, in step S8, the specific process steps for the homogenization are as follows: a positive homogenization process is used, and the homogenization thickness is 20~40μm.

[0019] Furthermore, in step S9, the electroplating gold-tin solution comprises the following mass components: using deionized water as a solvent, gold ions 8~12L, tin ions 8~15g / L.

[0020] Furthermore, in step S9, the thickness of the pre-made gold-tin solder layer is 6~9μm.

[0021] Furthermore, in step S10, the specific process steps for removing the photoresist are as follows: NMP (N-methylpyrrolidone) is used to remove the photoresist, and the board surface is cleaned with IPA (isopropanol); the specific process steps for etching are as follows: the copper layer is etched with alkali, the titanium layer is etched with 3~5wt% HF (hydrofluoric acid) solution, and then cleaned and dried.

[0022] Furthermore, the alkaline solution used in the alkaline etching process is a 25-30 wt% ammonia solution.

[0023] In the above technical solution, compared with the previous DPC (direct copper plating) ceramic substrate preparation process, the present invention has a higher level of reliability and can reduce defects such as poor bonding and pattern defects caused by raw materials and processes during processing. The patterning is carried out separately during the gold plating process, and the solder resist is prepared in advance before the gold plating. This avoids the need for subsequent laser gold sweeping, which may damage the aluminum nitride ceramic substrate or cause gold and solder overflow due to uneven gold sweeping. Appropriate surface treatment is performed for activation before gold plating. The product with extremely fine circuits is fully electrolytically activated to improve the bonding strength of the nickel-gold layer, which further improves the reliability of the connection material of power semiconductor devices. The pre-fabrication of the gold and solder layer improves the fineness of the pattern design. The electroplated Pt layer is used for patterned solder resist, skipping the gold sweeping step and improving the yield.

[0024] Furthermore, the electroplating gold solution also includes 3-5 g / L of thiolated polydopamine and 0.02-0.05 g / L of organophosphorus surfactant.

[0025] Furthermore, the thiolized polydopamine is prepared by the following process: Step 1: Dopamine hydrochloride is dissolved in deionized water, the pH is adjusted to 7.5-8.0, and nitrogen gas is introduced to obtain a dopamine hydrochloride solution; Step 2: Dimercaptopropanol is dissolved in anhydrous ethanol and added to the dopamine hydrochloride solution. After reacting at room temperature for 3-4 hours, the temperature is raised to 80-90℃ and refluxed for 1-3 hours. After cooling to room temperature, the pH is adjusted to 8.5-9.0, and stirring is continued for 6-8 hours to obtain thiolized polydopamine.

[0026] Furthermore, the concentration of the dopamine hydrochloride solution is 1.8~2.2 mg / mL.

[0027] Furthermore, the mass ratio of dimercaptopropanol, anhydrous ethanol, and dopamine hydrochloride solution is (0.3~0.6):(5~8):1.

[0028] Furthermore, the organophosphorus surfactant is prepared by the following process: Step (1) Polyoxyethylene ether and sodium chloroacetate are mixed, anhydrous ethanol is added, the temperature is raised to 40~50℃ and stirred for 10~20 min, sodium hydroxide is added and the temperature is raised to 45~55℃ and reacted for 2~4 h to obtain carboxymethylated epoxy compound; Step (2) Carboxymethylated epoxy compound is dissolved in xylene, phosphorus trichloride is slowly added dropwise at room temperature, the temperature is raised to 55~65℃, the reaction is stirred for 20~40 min, the temperature is raised to 100~120℃, deionized water is added, the temperature is kept for 2~3 h, the temperature is lowered to 70~90℃, hydrolysis is carried out for 20~40 min, the lower layer product is retained, and the product is rotary evaporated to obtain organophosphorus surfactant.

[0029] Furthermore, the molar ratio of polyoxyethylene ether, sodium chloroacetate, and sodium hydroxide is 1:(1.05~1.1):(1.0~1.2).

[0030] Furthermore, the mass ratio of polyoxyethylene ether to anhydrous ethanol is 1:(20~25).

[0031] Furthermore, the mass ratio of carboxymethylated epoxy compound, phosphorus trichloride, and xylene is (7~9):1:(50~80).

[0032] Furthermore, in step (2), the dripping rate is 1~2 drops / s.

[0033] In the above technical solution, in step S5, to avoid the risk of circuit board soldering failure due to excessive corrosion of the nickel layer, this invention introduces mercapto-polydopamine as a highly efficient corrosion inhibitor. The mercapto groups in its molecular chain can bond with charged metal surfaces, forming a barrier that prevents corrosive ions from entering the metal interior, thus enhancing the protection and corrosion inhibition of the plating layer. Adding mercapto-polydopamine can improve the stability of the gold plating solution, but more importantly, it improves the morphology of the deposit. This can be achieved by adding organophosphorus surfactants, which can act as accelerators to improve gold plating efficiency and as dispersants to improve the dispersibility of mercapto-polydopamine. Furthermore, organophosphorus surfactants have weaker adsorption capacity on gold electrodes than chloride ions and mercapto groups, and can synergistically interact with mercapto-polydopamine to increase the adsorption capacity of mercapto-polydopamine. The desorption of amines improves the purity and density of the gold layer, resulting in fine-grained and smooth characteristics. The synergistic effect significantly optimizes the microstructure and physical properties of the electroplated gold layer, enabling the regulation of the growth rate of gold nuclei, promoting the uniform formation and growth of nuclei, forming a nanoscale fine-grained structure, and resulting in a denser structure on the coating surface. By increasing the desorption of thiol polydopamine, the purity of the coating is improved, giving it lower porosity and stronger corrosion resistance. At the same time, the high-purity gold layer has lower contact resistance, ensuring the conductivity of TEC. The optimized electroplating gold solution has better gold plating uniformity, achieving uniform coating deposition even in complex geometries such as micropores and grooves on circuit boards, avoiding excessively thick coatings or scorching at edges or tips due to concentrated current density.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention has a higher level of reliability than the previous DPC ceramic substrate preparation process, and can reduce defects such as poor bonding and poor patterning caused by raw materials and processes during processing; the patterning is carried out separately during electroplating gold, and the solder resist is prepared in advance before gold plating, avoiding damage to the aluminum nitride ceramic substrate caused by subsequent laser gold sweeping, or gold and tin overflow caused by uneven gold sweeping. Appropriate surface treatment is carried out in the activation before gold plating, and the product with extremely fine circuits is fully electrolytically activated to improve the bonding force of the nickel-gold layer, which further improves the reliability and yield of the connection material of power semiconductor devices.

[0035] 2. This invention enhances the protection and corrosion inhibition of the plating layer by introducing thiolated polydopamine as a highly efficient corrosion inhibitor. By adding organophosphorus surfactants, it can act as an accelerator to improve gold plating efficiency and as a dispersant to improve the dispersibility of thiolated polydopamine. In addition, the organophosphorus surfactants and thiolated polydopamine have a synergistic effect, increasing the desorption of thiolated polydopamine, thereby improving the purity and density of the gold layer and exhibiting fine-grained and smooth characteristics. Attached Figure Description

[0036] Figure 1 is a process flow diagram of an embodiment of the present invention; Figure 2 is a structural schematic diagram of an embodiment of the present invention. Detailed Implementation

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the following specific embodiments, the catalyst is FFP, the wetting agent is HN-5, the polyoxyethylene ether has an average molecular weight of 500, and the stripping solution is an organic neutral stripping solution, model HY-66. Example 1:

[0039] A process for preparing a pre-formed gold-tin solder TEC includes the following steps: S1: An aluminum nitride ceramic substrate is sequentially subjected to alkaline washing, spray water washing, acid washing, re-spray water washing, ultrasonic water washing, and hot air drying. Drying is performed in a nitrogen oven at 150°C for 3 hours. Titanium-copper is then sputtered using a dual-target alternating sputtering process with magnetron sputtering, resulting in a 0.1μm titanium layer and a 2μm copper layer. S2: The aluminum nitride ceramic substrate obtained in step S1 is sequentially subjected to lamination, exposure, and development. Lamination is performed using a laminator to press a 38μm dry film for the first pattern transfer. S3: The aluminum nitride ceramic substrate obtained in step S2 is immersed in an electroplating copper solution for copper plating to form a thickened copper layer. The electroplating copper solution comprises the following mass components: 180g / L sulfuric acid, 50 g / L copper sulfate, 40 ml / L potassium sodium tartrate; the thickness of the thickened copper layer is 27 μm; S4: The aluminum nitride ceramic substrate obtained in step S3 is ground and sandblasted using a horizontal grinding process, using a ceramic brush and a non-woven brush in sequence; the sandblasting uses a horizontal wet blasting process, using a 1000-mesh diamond abrasive wheel as the blasting medium, with an upper pressure of 1.2 MPa, a lower pressure of 1.0 MPa, and a linear speed of 1 m / min; S5: The aluminum nitride ceramic substrate obtained in step S4 is first immersed in a nickel plating solution to form a 3 μm nickel layer, and then sequentially undergoes film lamination, exposure, development, and a second pattern transfer. Finally, it is sequentially subjected to 20 s of positive and negative pulse electrolytic activation, water washing, and then immersed in a pre-plating gold solution and a gold plating solution. Electroplating with gold to form a 1.5 μm gold layer; the pre-plating gold solution includes the following components by mass: 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as solvent, chloroauric acid 50 g / L, hydantoin 5 g / L; the electroplating gold solution includes the following components by mass: 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as solvent, chloroauric acid 100 g / L, hydantoin 5 g / L; S6: Immersing the aluminum nitride ceramic substrate obtained in step S5 into the platinum plating solution to plating Pt, forming a 0.3 μm Pt layer; the platinum plating solution includes the following components by mass: deionized water as solvent, chloroplatinic acid hexahydrate 3 g / L, diammonium hydrogen phosphate 10 g / L, disodium hydrogen phosphate 80 g / L; S7: The aluminum nitride ceramic substrate obtained in step S6... The aluminum ceramic substrate is stripped using a stripping solution; S8: The aluminum nitride ceramic substrate obtained in step S7 is sequentially subjected to photoresist coating, photolithography, and development, using a positive photoresist process with a photoresist coating thickness of 30μm. The photomask is then used for patterning and development, followed by plasma treatment; S9: The aluminum nitride ceramic substrate obtained in step S8 is immersed in an electroplating gold-tin solution to form a 6μm pre-fabricated gold-tin solder layer; S10: The aluminum nitride ceramic substrate obtained in step S9 is sequentially subjected to photoresist removal, etching, and cleaning. NMP is used to remove the photoresist, and the board surface is cleaned with IPA. A 25wt% ammonia solution is used to etch the copper layer, and a 3wt% HF solution is used to etch the titanium layer. Finally, the substrate is cleaned and dried to obtain TEC. Example 2:

[0040] This embodiment provides a process for preparing TEC with pre-made gold-tin solder. In step S5, the electroplating gold solution also includes 3 g / L of thiolized polydopamine and 0.02 g / L of organophosphorus surfactant. The thiolized polydopamine is prepared by the following process: Step 1: Dissolve dopamine hydrochloride in deionized water, adjust the pH to 7.5, and purge with nitrogen to obtain a dopamine hydrochloride solution. The concentration of the dopamine hydrochloride solution is 1.8 mg / mL. Step 2: Dissolve dimercaprol in anhydrous ethanol and add it to the dopamine hydrochloride solution. After reacting at room temperature for 3 hours, heat to 80°C and reflux for 2 hours. Cool to room temperature, adjust the pH to 8.5, and continue stirring for 6 hours to obtain thiolized polydopamine. The mass ratio of dimercaprol, anhydrous ethanol, and dopamine hydrochloride solution is 0.3:5:1. The organophosphorus surfactant is prepared by the following process: Step (1) (1) Mix polyoxyethylene ether and sodium chloroacetate, add anhydrous ethanol, heat to 45°C and stir for 15 min, add sodium hydroxide and heat to 50°C and react for 2 h to obtain carboxymethylated epoxy compound; the molar ratio of polyoxyethylene ether, sodium chloroacetate and sodium hydroxide is 1:1.05:1.0; the mass ratio of polyoxyethylene ether and anhydrous ethanol is 1:20; Step (2) Dissolve the carboxymethylated epoxy compound in xylene, add phosphorus trichloride dropwise at a rate of 1 drop / s at room temperature, heat to 55°C, stir and react for 20 min, heat to 100°C, add deionized water, keep warm for 2 h, cool to 70°C, hydrolyze for 20 min, retain the lower layer product, and rotary evaporate to obtain organophosphorus surfactant; the mass ratio of carboxymethylated epoxy compound, phosphorus trichloride and xylene is 7:1:50, and the rest of the method is the same as in Example 1. Example 3:

[0041] This embodiment provides a process for preparing TEC with pre-made gold-tin solder. In step S5, the electroplating gold solution also includes 4 g / L of thiolized polydopamine and 0.03 g / L of organophosphorus surfactant. The thiolized polydopamine is prepared by the following process: Step 1: Dissolve dopamine hydrochloride in deionized water, adjust the pH to 7.5, and purge with nitrogen to obtain a dopamine hydrochloride solution. The concentration of the dopamine hydrochloride solution is 2.1 mg / mL. Step 2: Dissolve dimercaprol in anhydrous ethanol and add it to the dopamine hydrochloride solution. After reacting at room temperature for 3 hours, heat to 80°C and reflux for 2 hours. Cool to room temperature, adjust the pH to 8.5, and continue stirring for 6 hours to obtain thiolized polydopamine. The mass ratio of dimercaprol, anhydrous ethanol, and dopamine hydrochloride solution is 0.5:6:1. The organophosphorus surfactant is prepared by the following process: Step (1) (1) Mix polyoxyethylene ether and sodium chloroacetate, add anhydrous ethanol, heat to 45°C and stir for 15 min, add sodium hydroxide and heat to 50°C and react for 3 h to obtain carboxymethylated epoxy compound; the molar ratio of polyoxyethylene ether, sodium chloroacetate and sodium hydroxide is 1:1.05:1.1; the mass ratio of polyoxyethylene ether and anhydrous ethanol is 1:22; Step (2) Dissolve the carboxymethylated epoxy compound in xylene, add phosphorus trichloride dropwise at a rate of 1 drop / s at room temperature, heat to 60°C, stir and react for 30 min, heat to 110°C, add deionized water, keep warm for 2 h, cool to 80°C, hydrolyze for 30 min, retain the lower layer product, and rotary evaporate to obtain organophosphorus surfactant; the mass ratio of carboxymethylated epoxy compound, phosphorus trichloride and xylene is 8:1:60, and the rest of the method is the same as in Example 1. Example 4:

[0042] This embodiment provides a process for preparing TEC with pre-made gold-tin solder. In step S5, the electroplating gold solution also includes 5 g / L of thiolized polydopamine and 0.05 g / L of organophosphorus surfactant. The thiolized polydopamine is prepared by the following process: Step 1: Dopamine hydrochloride is dissolved in deionized water, the pH is adjusted to 8.0, and nitrogen gas is introduced to obtain a dopamine hydrochloride solution. The concentration of the dopamine hydrochloride solution is 2.2 mg / mL. Step 2: Dimercaprolactone is dissolved in anhydrous ethanol and added to the dopamine hydrochloride solution. After reacting at room temperature for 4 h, the temperature is raised to 90°C and refluxed for 3 h. After cooling to room temperature, the pH is adjusted to 9.0, and stirring is continued for 8 h to obtain thiolized polydopamine. The mass ratio of dimercaprolactone, anhydrous ethanol, and dopamine hydrochloride solution is 0.6:8:1. The organophosphorus surfactant is prepared by the following process: Step (1) (1) Mix polyoxyethylene ether and sodium chloroacetate, add anhydrous ethanol, heat to 50°C and stir for 20 min, add sodium hydroxide and heat to 55°C and react for 4 h to obtain carboxymethylated epoxy compound; the molar ratio of polyoxyethylene ether, sodium chloroacetate and sodium hydroxide is 1:1.1:1.2; the mass ratio of polyoxyethylene ether and anhydrous ethanol is 1:25; (2) Dissolve the carboxymethylated epoxy compound in xylene, add phosphorus trichloride dropwise at room temperature at a rate of 2 drops / s, heat to 65°C, stir and react for 40 min, heat to 120°C, add deionized water, keep warm for 3 h, cool to 90°C, hydrolyze for 40 min, retain the lower layer product, and rotary evaporate to obtain organophosphorus surfactant; the mass ratio of carboxymethylated epoxy compound, phosphorus trichloride and xylene is 9:1:80, and the rest of the method is the same as in Example 1.

[0043] Comparative Example 1: A process for preparing a TEC (Electrodeionization Chromium Nitride) substrate includes the following steps: S1: An aluminum nitride ceramic substrate is sequentially subjected to alkaline washing, spray water washing, acid washing, further spray water washing, ultrasonic water washing, and hot air drying. Drying is performed in a nitrogen oven at 150°C for 3 hours. Titanium-copper is then deposited using a dual-target alternating sputtering process with magnetron sputtering, resulting in a 0.1 μm titanium layer and a 2 μm copper layer. S2: The aluminum nitride ceramic substrate obtained in step S1 is sequentially subjected to lamination, exposure, and development. A 38μm dry film is laminated using a laminator for the first pattern transfer; S3: The aluminum nitride ceramic substrate obtained in step S2 is immersed in a copper plating solution to form a thickened copper layer; the copper plating solution comprises the following components by mass: 180g / L sulfuric acid, 50g / L copper sulfate, and 40ml / L potassium sodium tartrate; the thickness of the thickened copper layer is 28μm; S4: The aluminum nitride ceramic substrate obtained in step S3 is ground and sandblasted using a horizontal grinding process, sequentially utilizing ceramic... Abrasive grinding with brushes and non-woven fabric brushes; sandblasting adopts a horizontal wet blasting process, using a 1000-mesh diamond abrasive wheel as the blasting medium, with an upper pressure of 1.2MPa, a lower pressure of 1.0MPa, and a linear speed of 1m / min; S5: The aluminum nitride ceramic substrate obtained in step S4 is first immersed in a nickel plating solution to form a 3μm nickel layer, then immersed in a pre-plating gold solution to form a 0.5μm layer, and then sequentially undergoes film lamination, exposure, and development for a second pattern transfer, followed by immersion in a gold plating solution for gold plating. A 1.2 μm gold layer is formed. The pre-plating gold solution includes the following components by mass: 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as solvent, chloroauric acid 50 g / L, and hydantoin 5 g / L. The electroplating gold solution includes the following components by mass: 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid as solvent, chloroauric acid 100 g / L, and hydantoin 5 g / L. S6: The aluminum nitride ceramic substrate obtained in step S5 is immersed in the platinum electroplating solution to plate Pt, forming a 0.3μm Pt layer; the platinum plating solution includes the following components by mass: 3g / L chloroplatinic acid hexahydrate, 10g / L diammonium hydrogen phosphate, and 80g / L disodium hydrogen phosphate, using deionized water as solvent; S7: The aluminum nitride ceramic substrate obtained in step S6 is stripped using a stripping solution; S8: The aluminum nitride ceramic substrate obtained in step S7 is sequentially subjected to spin coating, photolithography, and development, using a positive photoresist process with a spin coating thickness of 30μm, photolithography patterning on a mask, development, and then plasma treatment; S9: The aluminum nitride ceramic substrate obtained in step S8 is... An aluminum ceramic substrate is immersed in a gold-tin plating solution to form a 6μm pre-formed gold-tin solder layer; S10: The aluminum nitride ceramic substrate obtained in step S9 is sequentially subjected to photoresist removal, etching, and cleaning. NMP is used to remove the photoresist, and the board surface is cleaned with IPA. A 25wt% ammonia solution is used to etch the copper layer, and a 3wt% HF solution is used to etch the titanium layer. Finally, the substrate is cleaned and dried; S11: The aluminum nitride ceramic substrate obtained in step S10 is subjected to laser gold scanning using a UV nanosecond laser gold scanning process to create a patterned TEC.

[0044] Comparative Example 2: This comparative example provides a process for preparing TEC with pre-made gold-tin solder. In step S5, the gold plating solution includes 3 g / L of thiolated polydopamine and no organophosphorus surfactant is added; the rest of the method is the same as in Example 2.

[0045] Comparative Example 3: This comparative example provides a process for preparing TEC with pre-made gold-tin solder. In step S5, the gold plating solution includes 0.02 g / L of organophosphorus surfactant and does not add thiolized polydopamine; the rest of the method is the same as in Example 2.

[0046] Comparative Example 4: This comparative example provides a process for preparing TEC with pre-made gold-tin solder. In step S5, 0.5 g / L of 2-benzylimidazoline and 0.09 g / L of 3-amino-6-methylpyridazine are used in the gold plating solution to replace thiolated polydopamine and organophosphorus surfactant. The rest of the method is the same as in Example 2.

[0047] Experiment: TEC samples obtained from Examples 1-4 and Comparative Examples 1-4 were prepared, and their performance was tested and the results were recorded: Peel strength test: Under the conditions of 25℃ temperature and 60% humidity, the pre-formed gold-tin solder layer of the sample was cut into strips of 60mm×5mm size. The strips were fixed on the test fixture, and the strips were peeled off from the sample surface along the 90° direction using a universal testing machine. The peel force and the width of the peeled strip were recorded, and the peel strength was calculated; Thermal stability test: The sample was baked at 350℃ for 10 minutes, and the condition of the coating was observed to see if blistering or peeling occurred.

[0048] Table 1 Performance Comparison Table

[0049] Based on the data in the table above, the following conclusions can be clearly drawn: Compared with the TEC obtained in Examples 1-4, the TEC obtained in Examples 1-4 has stronger bonding force and better thermal stability.

[0050] Compared with Example 2, the TEC bonding strength and thermal stability obtained in Comparative Example 1 were significantly reduced, indicating that when gold plating was placed before pattern transfer and without positive and negative pulse electrolytic activation, the TCE electroplated bonding layer prepared after gold sweeping had interface defects, reduced plating density, and significantly reduced bonding strength and thermal stability, demonstrating the technical advantages of the preparation process of the present invention.

[0051] Compared with Example 2, the TEC bonding strength and thermal stability obtained in Comparative Examples 2-3 were reduced, indicating that adding thiolized polydopamine or organophosphorus surfactant to the gold plating solution improved the bonding strength and thermal stability compared with other comparative examples. This shows that adding a single thiolized polydopamine or organophosphorus surfactant has a certain enhancing effect on the density of the gold plating layer, but the effect of using it alone is not as good as the composite organophosphorus surfactant of the present invention.

[0052] Compared with Example 2, the bonding strength and thermal stability obtained in Comparative Example 4 were reduced, indicating that adding conventional corrosion inhibitors and accelerators to the electroplating solution has a certain effect on adjusting the grain structure of the electroplated gold layer, but it is not as effective as the thiolized polydopamine and organophosphorus surfactant prepared in this invention. This verifies the necessity of the preparation process of thiolized polydopamine and organophosphorus surfactant in this invention.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A process for preparing TEC with pre-formed gold-tin solder, characterized in that: Including the following processes: S1: Take an aluminum nitride ceramic substrate and magnetron sputter titanium copper to form a titanium copper layer; S2: The aluminum nitride ceramic substrate obtained in step S1 is sequentially subjected to film lamination, exposure, and development to perform the first pattern transfer. S3: Immerse the aluminum nitride ceramic substrate obtained in step S2 into a copper plating solution to form a thickened copper layer; S4: Grind and sandblast the aluminum nitride ceramic substrate obtained in step S3. S5: The aluminum nitride ceramic substrate obtained in step S4 is first immersed in a nickel plating solution to form a nickel layer. Then, it goes through film lamination, exposure, development, and a second pattern transfer. Finally, gold is electroplated to form a gold layer. S6: Immerse the aluminum nitride ceramic substrate obtained in step S5 into a platinum plating solution to form a platinum layer; S7: Remove the aluminum nitride ceramic substrate obtained in step S6 using a stripping solution; S8: The aluminum nitride ceramic substrate obtained in step S7 is sequentially subjected to homogenization, photolithography, development, and then plasma treatment. S9: Immerse the aluminum nitride ceramic substrate obtained in step S8 into an electroplating gold-tin solution to plating gold-tin, forming a pre-made gold-tin solder layer; S10: Sequentially remove the adhesive and etch the aluminum nitride ceramic substrate obtained in step S9 to obtain TEC.

2. The preparation process of TEC with pre-formed gold-tin solder according to claim 1, characterized in that: The thickness of the nickel layer is 3~7μm; the thickness of the gold layer is 1.2~1.5μm; the thickness of the platinum layer is 0.2~0.4μm; and the thickness of the pre-made gold-tin solder layer is 6~9μm.

3. The preparation process of TEC with pre-formed gold-tin solder according to claim 1, characterized in that: In step S1, the specific process steps of the magnetron sputtering are as follows: using a dual-target interactive sputtering process, first depositing titanium to form a titanium layer, and then depositing copper to form a copper layer. The thickness of the titanium layer is 0.1~0.2μm, and the thickness of the copper layer is 1.5~3μm.

4. The preparation process of TEC with pre-formed gold-tin solder according to claim 1, characterized in that: In step S2, the specific process of applying the film is as follows: a dry film is applied using a laminating machine, and the thickness of the dry film is 35~40μm.

5. The preparation process of a pre-formed gold-tin solder TEC according to claim 1, characterized in that: In step S4, the specific process steps of the grinding and sandblasting are as follows: a horizontal grinding process is adopted, and a ceramic brush and a non-woven fabric brush are used for grinding in sequence. Sandblasting is performed using a horizontal wet blasting process. The blasting medium is a 500~1000 mesh diamond grinding wheel, with an upper pressure of 1.2~1.5MPa, a lower pressure of 1.0~1.2MPa, and a linear speed of 0.8~1.5m / min.

6. The preparation process of TEC with pre-formed gold-tin solder according to claim 1, characterized in that: In step S5, the specific electroplating gold process steps are as follows: the aluminum nitride ceramic substrate obtained in the previous step is subjected to positive and negative pulse electrolytic activation for 10~30s, washed with water, and then immersed in the pre-plating gold solution and the electroplating gold solution in sequence for electroplating gold.

7. The preparation process of a pre-formed gold-tin solder TEC according to claim 5, characterized in that: The electroplating gold solution also includes 3-5 g / L of thiolated polydopamine and 0.02-0.05 g / L of organophosphorus surfactant.

8. The preparation process of a pre-formed gold-tin solder TEC according to claim 7, characterized in that: The thiolized polydopamine is prepared by the following process: Step 1: Dissolve dopamine hydrochloride in deionized water, adjust the pH to 7.5-8.0, and purge with nitrogen to obtain a dopamine hydrochloride solution; Step 2: Dissolve dimercaprol in anhydrous ethanol and add it to the dopamine hydrochloride solution. React at room temperature for 3-4 hours, then heat to 80-90℃ and reflux for 1-3 hours. Cool to room temperature, adjust the pH to 8.5-9.0, and continue stirring for 6-8 hours to obtain thiolized polydopamine.

9. The preparation process of a pre-formed gold-tin solder TEC according to claim 7, characterized in that: The organophosphorus surfactant is prepared by the following process: Step (1) Polyoxyethylene ether and sodium chloroacetate are mixed, anhydrous ethanol is added, the temperature is raised to 40~50℃ and stirred for 10~20 min, sodium hydroxide is added and the temperature is raised to 45~55℃ and reacted for 2~4 h to obtain carboxymethylated epoxy compound; Step (2) Carboxymethylated epoxy compound is added to xylene to dissolve, phosphorus trichloride is slowly added dropwise at room temperature, the temperature is raised to 55~65℃, the reaction is stirred for 20~40 min, the temperature is raised to 100~120℃, deionized water is added, the temperature is kept for 2~3 h, the temperature is lowered to 70~90℃, hydrolysis is carried out for 20~40 min, the lower layer product is retained, and the product is rotary evaporated to obtain organophosphorus surfactant.

10. A TEC with pre-formed gold-tin solder, characterized in that: Prepared by the preparation process according to any one of claims 1-9.

Images