Preparation method of dimethylamino borane

Abstract

The invention relates to the technical field of preparation of PCB (Printed Circuit Board) electronic chemical materials, in particular to a preparation method of a reducing agent material dimethylamino borane for pretreatment of horizontal chemical copper deposition in a PCB process. The raw materials comprise dimethylamine hydrochloride, sodium borohydride, sodium hydroxide and a solvent. The preparation method comprises the following steps: adding a solvent into a flask, then adding dimethylamine hydrochloride, and keeping high-speed stirring; replacing air in the flask with nitrogen; adding sodium borohydride into the flask in batches; preparing a mixed solution, and cooling; adding the prepared mixed solution into the flask in batches for continuous reaction; adding a sodium hydroxide solution and filtering; drying the mother liquor and then filtering; evaporating the mother liquor to remove a solvent, and filtering; and drying in vacuum to evaporate out the solvent, and recrystallizing to obtain the high-purity dimethylamino borane.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PCB (printed circuit board) electronic chemical material preparation, and particularly relates to a preparation method of a reducing agent material dimethylaminoborane for PCB process level chemical copper deposition pretreatment. BACKGROUND

[0002] Dimethylaminoborane (DMAB) is a key reducing agent for PCB process level copper deposition pretreatment. Its core role is to reduce the ion palladium layer adsorbed on the non-conductive substrate in the hole and on the surface of the PCB material to a metal palladium layer, thereby providing an effective catalytic basis for the uniform deposition of chemical copper ions. However, the preparation of DMAB faces multiple technical challenges: the reaction conditions are harsh, and a low-temperature environment and inert atmosphere protection are required, otherwise a large amount of hydrogen gas will be released, which may cause an explosion risk, and excessive temperature will also cause an increase in side reactions; some raw materials and solvents are corrosive and toxic, increasing the operation protection cost; the product separation and purification process is long, and inorganic salt by-products need to be treated in multiple steps, which may cause product loss.

[0003] Existing related patent solutions still have obvious limitations. Although the Chinese patent CN108586266A reduces the safety risk through inert gas protection, the solubility of borohydride in organic solvents is limited, and adding water will cause the raw material to fail, and the by-product salt will also inhibit the dissolution of the raw material, hindering the reaction. The Japanese patent JPH0597866A uses an excess amount of sodium borohydride and a solvent containing water, which not only causes waste of raw materials, but also increases the consumption of sodium borohydride, resulting in poor economic effect. The American patent US6060623 relies on pure organic solvent reaction, and the dissolution of salt inhibits the dissolution of the raw material, resulting in slow reaction and a cycle of up to 24 hours. The Chinese patent CN112940022A directly reacts sodium borohydride with water, and the yield is only 70%, which cannot meet the demand of mass production.

[0004] These existing technologies either have low raw material utilization rate and poor reaction efficiency, or face the dilemma of insufficient product yield and complex process, and cannot meet the requirements of preparation safety, economy, and large-scale production. Therefore, developing a simple process, high yield, and high purity DMAB preparation scheme has become an urgent technical problem in the industry SUMMARY To solve the above technical problems, the present application provides a preparation method of dimethylaminoborane, comprising the following steps: S1, under a nitrogen environment, 600-800 mL of THF is added to a reaction container, and then the temperature is lowered; S2, 100-150 g of dimethylamine hydrochloride is added and stirred until completely dissolved; S3, 60-80 g of NaBH4 is evenly divided into 10-30 portions, the temperature is kept stable, and one portion is added every 10-45 min, and after the addition of NaBH4 is completed, the reaction is carried out for 1-6 h. S4, dissolve 5-10 g NaOH in 100 g water, divide the NaOH solution into 5-20 portions, add 5-10 mL THF to each portion of the NaOH solution, and then cool to -15-5℃ to obtain a NaOH / THF mixture; S5, add one portion of the NaOH / THF mixture to the reaction system every 10-30 min, and after all the NaOH / THF mixtures are added, react for 1-6 h; S6, dissolve 7-8 g NaOH in 50-60 g water to obtain an NaOH aqueous solution, add 10-20% of the total amount of the NaOH aqueous solution to the reaction system, stir for 10-30 min, then add the remaining NaOH aqueous solution, and stir for 1-3 min; S7, filter the reaction solution obtained in step S6, collect the filtrate and stand to separate the liquid, collect the upper organic phase; wash the solid with THF, and extract the lower aqueous solution after separation with the THF solution used for washing, and combine the THF solution after extraction with the upper organic phase; S8, add a drying agent to the organic phase, stir to dry, filter, and collect the filtrate; S9, distill the filtrate under reduced pressure, and collect the liquid phase to obtain a crude dimethylaminoborane; S10, vacuum dry the crude dimethylaminoborane, then dissolve it in THF to obtain a crude dimethylaminoborane solution, and recrystallize to obtain dimethylaminoborane.

[0005] As an implementable case, the cooling temperature in step S1 is -10-0℃.

[0006] The reaction of NaBH4 and dimethylamine hydrochloride releases a large amount of hydrogen gas. If the temperature is too high, the reaction rate will increase rapidly, resulting in a large amount of hydrogen gas generated in a short time, which may exceed the displacement and discharge capacity of nitrogen, causing the system pressure to rise suddenly and increasing the risk of explosion. Low temperature of -10-0℃ can slow down the reaction process and make the hydrogen gas release smoothly, and nitrogen protection can effectively control the safety hazard.

[0007] As an implementable case, the molar ratio of NaBH4 to dimethylamine hydrochloride is 1:(0.98-1.02).

[0008] Further, the molar ratio of NaBH4 to dimethylamine hydrochloride is 1:1.

[0009] The S4 step of the present application prepares a NaOH / THF mixed solution, which can promote the dissolution of raw materials while inhibiting the hydrolysis of NaBH4, thus ensuring efficient reaction. On the one hand, NaOH in the mixed solution can ionize hydroxide ions to neutralize hydrogen ions in the system, thus maintaining an alkaline environment and inhibiting the hydrolysis reaction of the key raw material NaBH4 with water from the source, avoiding the generation of hydrogen and sodium borate to cause raw material waste and reduce invalid consumption to ensure that more raw materials participate in the target reaction. On the other hand, THF can further dissolve solid raw materials such as dimethylamine hydrochloride and NaBH4, and NaOH can improve the compatibility of raw materials and solvents, assisting the uniform dispersion of solid raw materials in THF, solving the problem of incomplete reaction caused by the limited solubility of raw materials in single THF, shortening the reaction time and improving the conversion rate. At the same time, the NaOH / THF mixed solution needs to be cooled to -15~5℃, and low temperature can further slow down the hydrolysis rate of NaBH4, form a "double protection" with the hydrolysis inhibition effect of NaOH, and avoid the sudden rise of the system temperature when the mixed solution is added, preventing the occurrence of side reactions such as excessive hydrolysis of borane and carbonization of raw materials, ensuring that the reaction temperature is stable in the optimal interval of~10-0℃, and ensuring the purity of the product.

[0010] The present application limits the addition of NaOH / THF mixed solution in multiple batches, which can avoid the local concentration of single large addition, side reactions and raw material dispersion damage, combined with 15-30min interval, which can make THF gradually dissolve the material, NaOH slowly neutralize, inhibit hydrolysis and prevent hydrogen gas from increasing, maintain stable reaction, and ensure raw material conversion rate and product purity.

[0011] It should be noted that the NaOH / THF mixed solution prepared in the S4 step is reduced to an optimal temperature of 0-5℃ lower than the reaction temperature in the flask to avoid excessive temperature rise when added to the reaction kettle; the addition method in step S5 can be added at one time, and the optimal is to add dropwise through a dropping funnel, which is convenient for controlling time and temperature. In step S6, the solid NaOH is dissolved in water, which is not limited to increasing or decreasing the amount of the solution in actual operation, and the range can be 70%-200% of the amount of the solution.

[0012] As an implementable case, the desiccant includes one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate, calcium chloride, 3A molecular sieve or 4A molecular sieve.

[0013] As an implementable case, the amount of the desiccant is 8-20% of the total mass of the organic phase. If the amount of the desiccant exceeds 20%, a more dry effect can be obtained, and if it is less than 8% and within the water-saturated adsorption range, extending the drying time can also obtain good drying effect. However, if the amount of the desiccant exceeds 20%, the desiccant will have a small amount of adsorption on the product, which will eventually reduce the yield of the entire preparation process.

[0014] As an example of an feasible approach, the drying process takes 1 to 4 hours.

[0015] As an example of implementation, the vacuum drying temperature in step S10 is 30-40°C.

[0016] Furthermore, the vacuum drying time is 30-60 minutes; As an example of implementation, the mass concentration of the crude dimethylaminoborane solution is 60-80 wt%.

[0017] As an example of implementation, the recrystallization temperature is -10 to 10°C.

[0018] The crude dimethylaminoborane may contain unreacted raw materials, such as small amounts of dimethylamine hydrochloride, NaBH4, byproducts, and trace amounts of solvent. By dissolving the crude product in tetrahydrofuran to form a 60-80 wt% solution, and allowing the dimethylamine hydrochloride to crystallize preferentially at a low temperature of -10 to 10°C, the impurities remain in the mother liquor due to differences in solubility. This effectively separates and removes impurities, and the pure product meets the purity requirements of the reducing agent in the horizontal copper plating pretreatment process in PCB manufacturing. This avoids impurities affecting the reduction effect of the ionic palladium layer, thereby ensuring the uniformity of subsequent chemical copper deposition and the manufacturing quality of the PCB.

[0019] Beneficial effects (i) In this invention, the molar ratio of NaBH4, the raw material for preparing dimethylaminoborane, to dimethylamine hydrochloride is close to 1:1. Furthermore, the hydrolysis of NaBH4 is inhibited by an alkaline environment, which greatly reduces the waste of raw materials. This avoids the problem of excessive sodium borohydride in traditional methods, reduces raw material costs, and improves economic efficiency.

[0020] (ii) This invention optimizes the solvent system by using a NaOH / THF mixture, improves the solubility of solid raw materials in organic solvents, solves the problem of incomplete reaction and need to extend reaction time caused by insufficient dissolution of raw materials in traditional solutions, shortens the overall reaction process, and improves industrial production efficiency.

[0021] (iii) The present invention maintains a nitrogen atmosphere throughout the preparation process to reduce the possibility of side reactions caused by the product coming into contact with oxygen; at the same time, it controls the stable release of hydrogen by low temperature control and multiple batches of feeding to avoid the risk of explosion caused by a sudden increase in hydrogen and improve the safety of the preparation process.

[0022] (iv) The recrystallization step in this invention effectively removes impurities, and the high-purity product can meet the stringent requirements of the reducing agent in the horizontal copper plating pretreatment in the PCB manufacturing process, ensuring the subsequent catalytic effect.

[0023] (v) The key steps in the preparation of this invention, such as the amount of NaOH solution and the type of desiccant, have reasonable room for adjustment, which can not affect the reaction effect, but also adapt to the material supply and cost control needs of different production scenarios, and facilitate industrial promotion. Attached Figure Description

[0024] Figure 1 The image shows the UV spectrum of dimethylaminoborane from Example 1.

[0025] Figure 2 The image shows the UV spectrum of dimethylaminoborane from Example 2.

[0026] Figure 3 The image shows the UV spectrum of dimethylaminoborane, Comparative Example 1.

[0027] Figure 4 The image shows the UV spectrum of Comparative Example 2, dimethylaminoborane. Detailed Implementation

[0028] Example 1 This example provides a method for preparing 100g of dimethylaminoborane, specifically the following steps: S1. In a 2L straight four-necked flask, first replace the air in the flask with nitrogen, and then maintain a nitrogen input of 1L / 15min throughout the process; under nitrogen atmosphere, add 650mL THF, and then cool to -5℃; S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at high speed (150rpm) until completely dissolved; S3. Divide 65.5g (1.7mol) NaBH4 into 20 equal portions, keep the temperature stable (within ±3℃), add one portion every 15min, and react for 4h after all NaBH4 has been added. S4. Dissolve 8g NaOH in 100g water, divide it into 10 equal portions of NaOH solution, add 7mL THF to each portion of NaOH solution, and then cool to -8℃ to obtain NaOH / THF mixture. S5. Add 1 part of NaOH / THF mixture to the reaction system every 20 minutes. After all the NaOH / THF mixture has been added, react for 2 hours. S6. Dissolve 7.2g NaOH in 58g water to prepare NaOH aqueous solution. First, add 10% of the total amount of NaOH aqueous solution to the reaction system and stir for 10min. Then add the remaining NaOH aqueous solution and stir for 3min. S7. Filter the reaction solution obtained in step S6, collect the filtrate and let it stand to separate the layers, collect the upper organic phase; wash the solid with 150 mL THF, and extract the lower aqueous solution after separation with the washing THF solution, and combine the extracted THF solution with the upper organic phase. S8. Add the organic phase (850 mL) to a 2 L straight four-necked flask, then add 90 g of anhydrous magnesium sulfate, stir and dry for 2 h. Keep one flask opening continuously purged with nitrogen, one flask opening vented, one remaining opening used as a stirring port, and the other flask opening sealed. Then filter and collect the filtrate. S9. Place the collected filtrate into a three-necked flask, connect the vacuum distillation apparatus, and attach the heating apparatus to perform vacuum distillation. Collect the liquid phase (about 800 mL) to obtain crude dimethylaminoborane. S10. The crude dimethylaminoborane was dried under vacuum at 35°C to obtain 97g of solid, with a crude product yield of 97%. It was then dissolved in THF to obtain a 70wt% crude dimethylaminoborane solution. The solution was recrystallized at -5°C to obtain 91.2g of pure dimethylaminoborane, with a pure product yield of 91.2%. The mother liquor was retained and could be included in the next recrystallization preparation.

[0029] Example 2 This example provides a method for preparing dimethylaminoborane, specifically the following steps: S1. In a 2L straight four-necked flask, first replace the air in the flask with nitrogen, and then maintain a nitrogen input of 1L / 15min throughout the process; under nitrogen atmosphere, add 650mL THF, and then cool to -5℃; S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at high speed (150rpm) until completely dissolved; S3. Divide 65.5g (1.7mol) NaBH4 into 20 equal portions, keep the temperature stable (within ±3℃), add one portion every 30min, and react for 2h after all NaBH4 has been added. S4. Dissolve 8g NaOH in 100g water, divide it into 10 equal portions of NaOH solution, add 7mL THF to each portion of NaOH solution, and then cool to -8℃ to obtain NaOH / THF mixture. S5. Add 1 part of NaOH / THF mixture to the reaction system every 20 minutes. After all the NaOH / THF mixture has been added, react for 2 hours. S6. Dissolve 7.2g NaOH in 58g water to prepare NaOH aqueous solution. First, add 10% of the total amount of NaOH aqueous solution to the reaction system and stir for 10min. Then add the remaining NaOH aqueous solution and stir for 3min. S7. Filter the reaction solution obtained in step S6, collect the filtrate and let it stand to separate the layers, collect the upper organic phase; wash the solid with 150 mL THF, and extract the lower aqueous solution after separation with the washing THF solution, and combine the extracted THF solution with the upper organic phase. S8. Add the organic phase (850 mL) to a 2 L straight four-necked flask, then add 90 g of anhydrous magnesium sulfate, stir and dry for 2 h. Keep one flask opening continuously purged with nitrogen, one flask opening vented, one remaining opening used as a stirring port, and the other flask opening sealed. Then filter and collect the filtrate. S9. Place the collected filtrate into a three-necked flask, connect the vacuum distillation apparatus, and attach the heating apparatus to perform vacuum distillation. Collect the liquid phase (about 800 mL) to obtain crude dimethylaminoborane. S10. The crude dimethylaminoborane was dried under vacuum at 35°C to obtain 101g of solid, with a crude product yield of 101%. It was then dissolved in THF to obtain a 70wt% crude dimethylaminoborane solution. The solution was recrystallized at -5°C to obtain 92.8g of pure dimethylaminoborane, with a pure product yield of 92.8%. The mother liquor was retained and could be included in the next recrystallization preparation.

[0030] Comparative Example 1 This example provides a method for preparing dimethylaminoborane, specifically the following steps: S1. In a 2L straight four-necked flask, first replace the air in the flask with nitrogen, and then maintain a nitrogen input of 1L / 15min throughout the process; under nitrogen atmosphere, add 650mL THF, and then cool to -5℃; S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at high speed (150rpm) until completely dissolved; S3. Divide 65.5g (1.7mol) NaBH4 into 20 equal portions, keep the temperature stable (within ±3℃), add one portion every 15min, and react for 4h after all NaBH4 has been added. S4. Mix 30 mL of water and 70 mL of THF, divide the mixture into 10 equal portions, and obtain the H2O / THF mixture. S5. Add one part of H2O / THF mixture to the reaction system every 15 minutes. After all the H2O / THF mixture has been added, react for 2 hours. S6. Dissolve 15.2g of NaOH in 122g of water to prepare a NaOH aqueous solution, and then add it directly into the flask all at once and stir for 2 minutes. S7. Filter the reaction solution obtained in step S6, collect the filtrate and let it stand to separate the layers, collect the upper organic phase; wash the solid with 150 mL THF, and extract the lower aqueous solution after separation with the washing THF solution, and combine the extracted THF solution with the upper organic phase. S8. Add the organic phase (850 mL) to a 2 L straight four-necked flask, then add 90 g of anhydrous magnesium sulfate, stir and dry for 1 h. Keep one flask opening continuously purged with nitrogen, one flask opening vented, the remaining opening used as a stirring port, and the other flask opening sealed. Then filter and collect the filtrate. S9. Place the collected filtrate into a three-necked flask, connect the vacuum distillation apparatus, and attach the heating apparatus to perform vacuum distillation. Collect the liquid phase (about 800 mL) to obtain crude dimethylaminoborane. S10. The crude dimethylaminoborane was dried under vacuum at 35°C to obtain 97.2 g of solid, with a crude product yield of 97.2%. It was then dissolved in THF to obtain a 70 wt% crude dimethylaminoborane solution, which was recrystallized at 5°C to obtain 88.1 g of pure dimethylaminoborane, with a pure product yield of 88.1%. The mother liquor was retained and could be included in the next recrystallization preparation.

[0031] Comparative Example 2 This example provides a method for preparing dimethylaminoborane, specifically the following steps: S1. In a 2L straight four-necked flask, first replace the air in the flask with nitrogen, and then maintain a nitrogen input of 1L / 15min throughout the process; under nitrogen atmosphere, add 650mL THF, and then cool to -5℃; S2. Add 140g (1.7mol) of dimethylamine hydrochloride and stir at high speed (150rpm) until completely dissolved; S3. Divide 65.5g (1.7mol) NaBH4 into 20 equal portions, keep the temperature stable (within ±3℃), add one portion every 30min, and react for 2h after all NaBH4 has been added. S4. Mix 30 mL of water and 70 mL of THF, divide the mixture into 10 equal portions, and obtain the H2O / THF mixture. S5. Add one part of H2O / THF mixture to the reaction system every 30 minutes. After all the H2O / THF mixture has been added, react for 0.5 hours. S6. Dissolve 15.2g of NaOH in 122g of water to prepare a NaOH aqueous solution, and then add it directly into the flask all at once and stir for 5 minutes. S7. Filter the reaction solution obtained in step S6, collect the filtrate and let it stand to separate the layers, collect the upper organic phase; wash the solid with 150 mL THF, and extract the lower aqueous solution after separation with the washing THF solution, and combine the extracted THF solution with the upper organic phase. S8. Add the organic phase (850 mL) to a 2 L straight four-necked flask, then add 90 g of anhydrous magnesium sulfate, stir and dry for 2 h. Keep one flask opening continuously purged with nitrogen, one flask opening vented, one remaining opening used as a stirring port, and the other flask opening sealed. Then filter and collect the filtrate. S9. Place the collected filtrate into a three-necked flask, connect the vacuum distillation apparatus, and attach the heating apparatus to perform vacuum distillation. Collect the liquid phase (about 800 mL) to obtain crude dimethylaminoborane. S10. The crude dimethylaminoborane was dried under vacuum at 35°C to obtain 94.6 g of solid, with a crude product yield of 94.6%. It was then dissolved in THF to obtain a 70 wt% crude dimethylaminoborane solution, which was recrystallized at 5°C to obtain 86.8 g of pure dimethylaminoborane, with a pure product yield of 86.8%. The mother liquor was retained and could be included in the next recrystallization preparation.

[0032] The ultraviolet spectra of the dimethylaminoboranes prepared in Examples 1-2 and Comparative Examples 1-2 are shown below. Figures 1-4 As shown.

[0033] The yields of pure products in Comparative Examples 1 and 2 were 3-6% lower than those in Examples 1-2. The main difference lies in the fact that in the comparative examples, the H2O / THF mixture was added to the reaction system in batches to promote the dissolution of the reactants. The NaBH4 in the reactants reacted quite violently in the aqueous phase. Although the mixing of THF slowed down the direct contact and reduced the degree of reaction, a small amount of reactants still reacted. In contrast, Examples 1-2 maintained the alkaline state of the solvent in the NaOH / THF mixed solvent, effectively reducing the attack reaction of water ionized hydrogen ions on the sodium borohydride reactants. This avoided the hydrolysis reaction of sodium borohydride by water ionized hydrogen ions during the dissolution process, reduced the loss of reactants due to side reactions, and further improved the yield.

Claims

1. A method for preparing dimethylaminoborane, characterized in that, Includes the following steps: S1. Under nitrogen atmosphere, add 600~800mL THF to the reaction vessel and then cool down; S2. Add 100-150g of dimethylamine hydrochloride and stir until completely dissolved; S3. Divide 60-80g of NaBH4 into 10-30 equal portions, keep the temperature stable, and add one portion every 10-45 minutes. After the NaBH4 is added, react for 1-6 hours. S4. Dissolve 5-10g NaOH in 100g water, divide it into 5-20 equal portions of NaOH solution, add 5-10mL THF to each portion of NaOH solution, and then cool to -15~5℃ to obtain NaOH / THF mixture. S5. Add 1 part of NaOH / THF mixture to the reaction system every 10-30 minutes. After all the NaOH / THF mixture has been added, react for 1-6 hours. S6. Dissolve 7-8g NaOH in 50-60g water to prepare NaOH aqueous solution. First, add 10-20% of the total amount of NaOH aqueous solution to the reaction system and stir for 10-30 minutes. Then add the remaining NaOH aqueous solution and stir for 1-3 minutes to obtain the reaction solution. S7. Filter the reaction solution obtained in step S6, collect the filtrate and let it stand to separate the layers, collect the upper organic phase; wash the solid with THF, and extract the lower aqueous solution after separation, and combine the extracted THF solution with the upper organic phase. S8. Add a desiccant to the organic phase, stir to dry, filter, and collect the filtrate; S9. Distill the filtrate under reduced pressure and collect the liquid phase to obtain crude dimethylaminoborane. S10. The crude dimethylaminoborane is dried under vacuum and then dissolved in THF to obtain a crude dimethylaminoborane solution. The solution is then recrystallized to obtain dimethylaminoborane.

2. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The cooling temperature in step S1 is -10~0℃.

3. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The molar ratio of NaBH4 to dimethylamine hydrochloride is 1:(0.98-1.02).

4. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The desiccant includes one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate, calcium chloride, 3A molecular sieve, or 4A molecular sieve.

5. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The amount of the desiccant used is 8-20% of the total mass of the organic phase.

6. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The drying time in step S8 is 1 to 4 hours.

7. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The vacuum drying temperature in step S10 is 30-40℃.

8. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The vacuum drying time is 30-60 minutes.

9. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The mass concentration of the crude dimethylaminoborane solution is 60-80 wt%.

10. The method for preparing dimethylaminoborane according to claim 1, characterized in that, The recrystallization temperature is -10~10℃.

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