Background[1][2]
Chemical Plating is a technology that realizes metallization of non-conductor surfaces. It is widely used in surface modification, printed circuit manufacturing, electromagnetic shielding technology, electronic component packaging and other fields. Since electroless plating uses the principle of self-catalytic oxidation-reduction reaction of metal salts and reducing agents in the same solution on the surface of a catalytically active substrate without external current, chemical deposition forms a metal or alloy coating on the surface of the substrate. It is a surface treatment technology, so it is also called autocatalytic plating, electroless plating or electroless plating, etc.
According to the type of metal obtained by electroless plating, electroless plating can be divided into: electroless silver plating, electroless copper plating, electroless nickel plating and other types. Among them, electroless copper plating metal has the advantages of mature technology, good coating bonding, high conductivity reliability, heat resistance and electromagnetic shielding, uniform coating thickness, and reasonable price, and is the most widely used in electroless plating technology.
Research on using other reducing agents to replace formaldehyde in electroless copper plating solutions to achieve electroless copper plating has been reported in literature and patents. The main alternative reducing agents include dimethylamine borane (DMAB), glyoxylic acid, Sodium phosphate, etc. Among them, the electroless plating system using sodium hypophosphite as the reducing agent has the characteristics of low pH value, low cost and relative safety, and has great development value and application prospects.
Reduction mechanism[1]
Sodium hypophosphite reduction electroless copper plating has the same chemical essence as other electroless copper plating processes. It also uses a suitable reducing agent to reduce the free copper ions (II) in the copper plating solution into solid copper crystals and then plate them. An electroless copper plating method that covers the surface of a substrate to form a nano- or micron-scale copper plating. At present, the sodium hypophosphite reduction electroless copper plating process that has been researched and developed is very similar to the formaldehyde reduction electroless copper plating process, but the reaction mechanism is much more complex.
This is because pure metallic copper does not have catalytic activity for the oxidation reaction of sodium hypophosphite. When using it as a reducing agent for electroless copper plating, it cannot produce copper particles and ions through the activation and sensitization stages like the formaldehyde system. Silver particles realize self-catalytic electroless plating reaction. In order for the electroless copper plating reaction of the sodium hypophosphite system to continue, a substance with catalytic activity for the electroless plating reaction must be added.
The current way to solve this technical problem is to learn from the process principle of electroless nickel plating, add nickel ions to the plating solution, and obtain a copper coating containing a small amount of nickel element through the co-deposition of metallic nickel and copper, and the deposited nickel The particles can catalyze the reaction of sodium hypophosphite to reduce Cu2+, thereby ensuring the continuous progress of the electroless copper plating reaction and ultimately obtaining high-quality copper plating. The chemical reaction equation of the electroless plating system adding Ni2+ particles is as follows.
Apply[2][3][4][5]
Sodium hypophosphite is used as an analytical reagent and is often used as a strong reducing agent. It is also used in clinical testing and electroplating. Examples of its applications are as follows:
1. Preparation of nano-copper particles by sodium hypophosphite reduction method.
In recent years, metal nanoparticles have shown extremely important application value in various fields due to their good electrical and thermal conductivity. Copper is the only metal that can be produced naturally in large quantities and is found in various ores; it is second only to aluminum in the consumption of non-ferrous metal materials. As an important industrial raw material, nano-copper particles can greatly reduce industrial costs in the production of high-grade lubricants, conductive slurries, and high-efficiency catalysts instead of precious metal powders, and have broad application prospects.
Therefore, research on copper nanoparticles has attracted widespread attention at home and abroad in recent years. Some studies have used a two-step liquid phase reduction method, using oleic acid as the extraction agent and protective agent, glucose and sodium hypophosphite to reduce copper sulfate pentahydrate to cuprous oxide and elemental copper respectively, and prepared a particle size of about 50-100 nanometers. Uniformly dispersed spherical copper nanoparticles were characterized by XRD, SEM and TEM. The results show that under the protection of oleic acid, spherical nano-copper particles with good dispersion and antioxidant properties can be obtained by using a two-step liquid phase reduction method.
2. Used for electroless nickel plating.
Electroless nickel plating, especially the system using sodium hypophosphite as the reducing agent, is widely used in the current industry. Research has disclosed a chemical plating solution for drilling drill pipes based on nickel sulfate, which is prepared by using the following raw materials by weight: nickel sulfate, 60 to 80 parts; sodium hexametaphosphate, 20 to 30 parts; ethylenediamine Disodium tetraacetate, 10 to 20 parts; sodium citrate, 4 to 6 parts; citric acid, 6 to 8 parts; copper sulfate, 3 to 5 parts; sodium acetate, 2 to 4 parts; thiourea, 0.1 to 0.3 parts ; Water, 900 to 1100 parts; sodium hypophosphite and zinc borate total 7 to 9 parts, and the weight ratio of sodium hypophosphite and zinc borate is 6 to 8:1.
The electroless plating liquid PVC resin powder provided by the present invention has stable quality and can significantly improve the corrosion resistance of drilling drill pipes after treatment. This technical effect is similar to that of sodium hypophosphite and sodium hypophosphite in the raw materials. The weight ratio of zinc borate is related. When the weight ratio of sodium hypophosphite and zinc borate is 6 to 8:1, the anti-corrosion effect on drill pipe is optimal.
3. Used in the preparation of olanzapine intermediates.
Preparation method of olanzapine intermediate 4-amino-2-methyl-10H-thiophene [2,3-b][1,5]-benzodiazepine hydrochloride: in ethanol mediumIn the mass, 2-(2-nitroanilino)-5-methylthiophene-3-nitrile is reduced and condensed under the action of hydrochloric acid, sodium hypophosphite and stannous chloride to prepare 4-amino-2-methyl- 10H-thiophene [2,3-b][1,5]-benzodiazepine hydrochloride; the above method uses the cleaning reagent sodium hypophosphite monohydrate to reduce the amount of highly toxic reagent stannous chloride dihydrate , the molar ratio of 2-(2-nitroanilino)-5-methylthiophene-3-nitrile and stannous chloride in the prior art is reduced from 1:3.36 to 1:0.2, and the product yield and purity are Compared with the existing technology, the method of the present invention greatly reduces environmental pollution and is suitable for industrial production.
Preparation[6]
React yellow phosphorus (or white phosphorus) and excess calcium hydroxide aqueous solution at 98°C: the phosphine produced in the reaction is drawn out and absorbed with 10% copper sulfate solution. After the reaction is completed, cool, add carbon dioxide until the pH value of the solution is 7.5-8.0, and precipitate excess calcium hydroxide. Filter out the precipitate and wash it with water several times. The washing liquid is merged into the filtrate, and then 20% sodium carbonate solution is added in small portions until the solution becomes weakly alkaline to phenolphthalein: filter, and the filtrate is vacuum evaporated and concentrated to a density of 1.16, and then filtered again. The filtrate is evaporated and concentrated for the second time until a crystallized film appears. It is cooled and crystallized. After drying, it is dried at 80-95°C to prepare sodium hypophosphite. The mother liquor can be recycled.
Main reference materials
[1] Wu Jing, Wang Shouxu, Zhang Min, et al. Research and prospects on sodium hypophosphite reduction electroless copper plating process [J]. Printed Circuit Information, 2010 (7): 26-29.
[2] Wen Jin, Li Jie, Chen Qiyuan. Preparation of nanometer copper particles by sodium hypophosphite reduction method [J]. Functional Materials, 2011, 42(1): 189-192.
[3] Wang Meiyuan, Kuang Yafei. Research progress on electroless nickel plating with sodium hypophosphite system[J]. Corrosion and Protection, 1999, 20(12): 533-536.
[4] CN201610590469.4 A chemical plating solution for drilling drill pipes based on nickel sulfate
[5] CN201110 Bactericidal preservative 078928.8 Preparation method of olanzapine intermediate
