The electroless plating process is considered to be more convenient and cheaper. It is most suitable for depositing on parts with a large number of holes, splits, bends, curves, abnormal shapes, threads, etc. It is effective and economical. Click here to download the full text with images
Electroless plating uses redox reactions to deposit metal on objects without passing current. Redox reactions include reduction and oxidation reactions. One metal is reduced from its salt, and the other metal is oxidized to a metal salt.
Electroless plating technology has been used for decades. They involve the use of a mild reducing agent (usually formaldehyde) to reduce the complex metal.
For example, the following reaction can be used to make a mirror:
R-CHO 2 [Ag (NH3)2]OH → 2 Ag(s) RCOONH4 H2O 3 NH3 where R is an organic group or hydrogen. This reaction deposits a shiny layer of elemental silver on the walls of the container.
Electroless plating is an autocatalytic reaction. Autocatalytic reactions are chemical reactions in which at least one reactant is also a product. And the chemical reaction in which the product (or reaction intermediate) also acts as a catalyst. In such reactions, it is often found that the observed reaction rate increases with time from its initial value.
As an autocatalytic and electrochemical redox process, the formulation and control of bath stability, deposition consistency and bath maintenance have become critical and sometimes difficult. The possibility of metal deposition due to the settling of the plating solution-"seeds"-on the walls, pipes and other parts of the plating vessel/tank, resulting in loss of metal and plating solution components, forced to clean the tank and pipes, resulting in chemical costs and time Loss.
Of course, electroless metal plating does not require the use of electricity and metal anodes, because it is an autocatalytic process that reduces metals in the presence of precious metal catalysts. However, the solution preparation, maintenance, plating tank design and arrangement of heaters, cooling coils, stirring systems, etc. have become very critical in order to obtain consistent plating quality, uniform metal deposition rate and constant productivity because of the need to release metal Ions are evenly plated on the required parts, and the lost metal is added according to the loss rate of the plating solution. In addition to these surface preparations, special attention should be paid to the catalytic preparation of the surface to obtain metal adhesion and electroless plating.
The advantages of electroless plating include:
The metals listed below can be deposited on various substrates by electroless plating techniques, as shown below:
The metals deposited by electroless plating techniques are: 1. Copper, 2. Nickel, or a. Nickel-boron alloy B. Nickel-phosphorus alloy, c. Nickel-Teflon composite materials, Nickel-Sic, Nickel-Al2O3, etc., 3 arsenic, 4. cobalt, 5. chromium, 6. iron, etc., on various substrates, as shown in the following figure:
1. Electroless copper is deposited on ferrous and non-ferrous metals, namely brass, bronze, unless conductive substrates-ABS plastics and other electroplating grade plastics, glass epoxy materials for printed circuit boards, ceramics, SiO2, etc., used The catalyst is a solution containing Pdcl2 and Sncl2 and Hcl, and the reducing agent is formaldehyde-HCHO.
CuSO4 2HCHO 4NaOH→ Cu Na2SO4 H2 2H2O 2HCOONa
2a. Electroless nickel is deposited on ferrous metals, ie iron, tool steel or low carbon steel, with or without an electroless copper undercoat. The catalyst used is a solution containing Pdcl2 and Sncl2 and HCl. The reducing agent used is sodium hypophosphite or boron hydride.
2b. Electroless nickel plating on tool steel with or without copper primer is to improve wear resistance. It is used in brass, bronze or copper electrical parts and auto parts switches, mobile phone parts and other electrical and electronic equipment , Components, etc. to improve wear resistance. Conductivity with reduced contact resistance. Therefore, the application of electroless copper plating and electroless nickel plating is very extensive.
2c. In addition to these other special electroless plating has been reported in the literature, that is, nickel containing 5%, 7%, 9% Teflon, nickel containing SiC, nickel containing diamond, etc. are used for special applications of automotive parts and other parts. , To improve its performance and application-hardness, wear resistance, wear resistance, etc.
2 days. For aerospace applications, chemical plating composite materials are making new developments.
The history of electroless nickel plating:
In 1844, Wurtz first used electroplating of metallic nickel from aqueous solutions in the presence of hypophosphite as a chemical accident.
In 1911, Roux reported that metals inevitably precipitate in powder form; however, these works have not been used in practice. In its early stages, progress in this field has been slow until the Second World War. In 1946, Brenner and Riddell developed a process for electroplating the inner wall of a tube with a nickel-tungsten alloy, which was derived from a citrate bath using an insoluble anode, resulting in hypophosphite Unusual reduction performance.
The US Patent Office stated that the difference between its patent issued in 1950 and earlier patents is that the Roux reaction is spontaneous and complete, while the Brenner and Riddell process is a controlled catalytic process, so the deposition only occurs in the immersion bath On the catalytic surface.
Brenner later wrote that his patent was an accidental discovery similar to the work of Wurtz and Roux, but stated that he had issued a patent to protect the rights of the US government. In fact, a declassified U.S. Army technical report written in 1963 extensively introduced the work of Wurtz and Roux, and attributed more discoveries to them than to Brenner. This electroplating process is attributed to the chemical reduction of nickel ions.
During 1954-59, Gutzeit of GATC (American General Transportation Company) was committed to the comprehensive development of electroless plating using only chemical reduction as an alternative to traditional electroplating.
Initially, Odekerken conducted particle co-deposition in 1966 to electrodeposit Ni-Cr.
In this study, in the intermediate layer, fine powder particles such as alumina and polyvinyl chloride (PVC) resin are distributed in the metal matrix. One layer of the coating is composite, but the other parts of the coating are not.
The first commercial application of their work was the use of electroless Ni-SiC coatings on Wankel internal combustion engines, and in 1981 they co-deposited another commercial composite containing polytetrafluoroethylene (Ni-P-PTFE) . However, compared with composites containing Al2O3 or SiC, the co-deposition of diamond and PTFE particles is more difficult. The feasibility of adding sub-micron to nanometer-sized second phase fine particles to the metal/alloy matrix has initiated a new generation of composite coatings.
Possible mechanism of eNi deposition:
According to Scholder and Heckel, the deposit consists of a mixture of pure metals and metal phosphides. They made the following reaction:
NiO H3PO2 → Ni H3PO3
3H3 PO2 → H3PO3 2P 3H2O
2Ni P → Ni2P6
The author did not link the reduction of Ni with the evolution of H2.
Luke's theory gives a satisfactory explanation for the simultaneous reduction of nickel and hydrogen, as follows:
H2PO2-- H2O → HPO3 2-- 2H H-- (in acid solution)
H2PO2-- 2 OH-- → HPO3 2-- H2O H-- (in alkaline solution)
Ni2 2 H-- → Ni0 2H
Due to the complexity of the deposition process, many theories have been proposed for the chemical deposition mechanism of Ni.
Table 1: Electroless nickel deposit types with different phosphorus content
Heat treatment temperatureᵒC
LPEN-low phosphorus e nickel
Uniform coating, most resistant to alkaline environment, best solderability
MPEN-Medium Phosphorus and Nickel
HPEN- High Phosphorus e Ni
Super corrosion protection, most resistant to acid environment
Increase lubricity and low reflectivity
Electroless nickel plating can also be non-magnetic, making it the best choice for electromagnetic shielding.
An important aspect of electroless nickel plating is that it can produce deposits with very high thickness uniformity. It is very useful for coating on complex parts with critical dimensions, such as ball valves or threaded parts. This is because no current is involved and related current distribution problems will not arise.
The formula of electroless nickel on copper:
I tried several EN plating formulations. In this technical paper, after more than a year of continuous use in the mass production of machinery and automotive parts, the most successful chemical nickel plating formulations are discussed in detail.
The following bath-I is selected from the literature because it has a good effect on copper and electroless copper-plated steel parts for electroless nickel plating, as shown below:.
1) Nickel chloride Nicl2 .6H2O-20 grams per liter
2) Sodium hypophosphite, NaH2PO2.H2O-15 grams per liter
3) Acetic acid, CH3COOH-20 ml per liter
4) DL-malic acid, CH2 (COOH).CH (OH).COOH -20 g/L
5) Glycine NH2CH2COOH-5 grams per liter
6) Boric acid H3BO3 - 2 grams per liter
pH – 6.5 to 6.7 (adjusted with NaOH and Hcl)
Temperature-70 to 72 o C
Time to get 5 to 6 micron eNickel on copper – 25 to 30 minutes
The process sequence for non-ferrous metal parts made of copper, brass and bronze is as follows: 1) degreasing 2) alkaline cleaner 3) soaking 4) acid soaking 5) thorough soaking 6) pre-activator 7) activator 8) Running water 9) After activator 10) Thorough running water 10) Electroless nickel plating 11) Running water 12) Hot water immersion 13) Drying.
The process sequence of ferrous metal parts made of steel, tool steel, etc. is as follows: 1) Degreasing 2) Alkaline washing 3) Rinse 4) Acid leaching 5) Thorough rinsing 6) Pre-activator 7) Activator 8) Thorough leaching Washing 9) After activator 10) Washing 11) Electroless copper plating 12) Washing 13) Electroless nickel plating 14) Washing 15) Hot water immersion 16) Drying
The process sequence for ABS plastics with electroless copper plating coating is as follows: 1) Chromic acid etching 2) Soaking 3) Thorough soaking 4) Pre-activator 5) Activator 6) Thorough soaking 7) Post activator 8) Soaking 9 ) Electric-less copper plating 10) Water washing 11) Electroless nickel plating 12) Water washing 13) Hot water immersion 14) Drying.
After electroless nickel plating, a thicker bright nickel deposit is deposited as follows:
1. Fixture and load 2. Watt nickel plating (5 to 10 minutes to obtain 4 to 5 microns) 3. Swill 4. Bright nickel plating 25-30 tons to obtain 20 microns of nickel 5. Swill 6. Bright chrome plating for 10 Rice 7. Rinse 8. Dry 9. Unload.
By changing the chemical composition of various components, Bath.1- has been further studied. Draw a chart to find the best conditions to get the best and fast deposition results of electroless nickel on copper.
Each time the concentration of one chemical component of the 6 chemicals is different and the study is conducted at 70 o C, 75 o C and 80 o C.
A clean, pre-weighed 1"x1" size copper sample was used throughout the experiment, and the nickel deposition thickness was obtained and calculated by the weight gain method. This was cross-checked with an X-ray fluorescence thickness tester, and the result was within ±5%. the difference. Plot the results of the thickness measured by the weight gain method to find the best conditions for the chemical composition of the plating solution.
These best results are shown in Table 2
Table 2: Description of the best composition of eNi Bath-II
Chemical composition of electroless nickel plating bath
NaH2PO2H2O
Acetic acid CH3COOH
8 micron nickel, 19 ml/l
CH2(COOH).CH(OH)-COOH
Glycine NH2CH2COOH
Boric acid H3BO3
The best composition of eNi bath (Bath II):
Nickel chloride, Nicl2 .6H2O-15 grams per liter
Sodium hypophosphite, NaH2PO2H20 – 14 grams per liter
Acetic acid, CH3COOH-22 ml per liter
DL-malic acid, CH2 (COOH). CH (OH). COOH-18 g/l
Glycine, NH2CH2COOH-7 grams per liter
Boric acid, H3BO3 -2 g/l
pH – 6.8 to 6.9 (adjusted with NaOH and Hcl)
Temperature-70 to 72 o C
Thickness: 6.74 to 9.0 microns of nickel in 30 minutes
Time-30 to 35 minutes
Final (optimal) composition of eNi bath at 80 o C (after temperature study:
Nickel chloride, Nicl2 .6H2O-15 grams per liter
Sodium hypophosphite, NaH2PO2H20 – 14 grams per liter
Acetic acid, CH3COOH-22 ml per liter
DL-malic acid, CH2 (COOH). CH (OH). COOH-18 g/l
Glycine, NH2CH2COOH-7 grams per liter
Boric acid, H3BO3 -2 g/l
pH – 6.8 to 6.9 (adjusted with NaOH and Hcl)
Temperature-80 to 82 o C can get 9.44 microns of nickel
Time-25 to 30 minutes
The bath is prepared and used for 12 months to verify and confirm the results, and it is consistent to provide 8-9 microns of nickel in 25-30 minutes at 80 o C.
EDAX analysis was performed on the deposited nickel to understand its composition. The results are shown in Figures 15 and 16. The phosphorus content can be clearly seen in the EDAX diagram. The deposit contains 12.23% to 13.74% phosphorus.
These best results are shown in Table 3
Table 3: The best composition description of eNi Bath-III
At the optimum temperature from 80oC to 82oC
Chemical composition of electroless nickel plating bath
Nicl2 .6H2O (g/l)
NaH2PO2.H2 O (g/l)
OK
Acetic acid CH3COOH
80oC; 30 minutes: 8 microns of nickel, 19 ml/liter
CH2(COOH).CH(OH)-COOH
NH2CH2COOH (g/l)
H3BO3 (g/l)
This formulation is very useful for electroless nickel plating in rack and barrel plating for mass production of automobiles and industrial parts.
The properties of the obtained eNi deposit:
1. The plating thickness ranges from 8.5 to 9 microns and can be obtained within 25 to 30 minutes. The thickness is measured by weight gain method and verified by X-ray fluorescence thickness gauge.
2. The co-deposited phosphorus is 12.23 to 13.74%.
In addition, the content of P in the sediment can be reduced by changing the content of sodium hypophosphite in the solution.
3. The hardness of baking or heat treatment after plating is as high as 70Rc.
4. Salt spray corrosion test (1000 hours of high-phosphorus eNi deposit;
250 hours, containing medium phosphorus eNi deposits)
In the case of lubricating wear, the wear resistance of electroless nickel plating is very good. The wear index of different deposits is shown in Table 4, from Taber Abrader/Abraser.
Table 4: Taber Abrader's wear index comparison:
Electroless nickel (when deposited)
Electrolytic nickel from Watts Bath (when deposited)
Electrodeposition of hard chromium (when deposited)
The advantages of this bathtub are:
1. Electroplating of racks and barrels is possible
2. Selective surface plating can be masked. Masking is done by screen printing ink, peelable solder mask or by photo printing.
3. The deposited eNi contains 12.23-13.74% P, which is strongly recommended for the hardness requirements of the deposit after heat treatment.
This is achieved by heat treating the deposited eNi at C for 1.5 to 2 hours.
4. After simulating electroplating, adding chemicals after analysis and adjusting the pH value to the working pH value, the plating solution can be easily maintained and restarted at any time.
By regularly analyzing and adding the chemical composition of the bath liquid, the content of the bath liquid can be easily maintained. In this case, the key components to be analyzed are 1) nickel or nickel chloride and 2) sodium hypophosphite.
A sort of. Concentrated ammonia
Murexide indicator: Grind 0.2 gm murexide AR and 100 gms sodium chloride AR into a fine powder in a mortar, and store it in a clean glass or polyethylene bottle; mark the content and date correctly.
c.0.05 M EDTA C10H14N2Na2O8 ·2H2O
Standard solution of disodium ethylenediaminetetraacetic acid:
Dissolve 10 grams of sodium hydroxide-NaOH AR in 200 ml of deionized water in a 1-liter volumetric flask. Weigh 18.6 grams of disodium EDTA AR and record the exact weight. Transfer it to the flask and stir until completely dissolved. Dilute to the mark with deionized water, mix well and transfer it to a clean polyethylene container, mark with EDTA molarity and date.
M of EDTA = weight of EDTA / 372
1. Draw 2 ml of electroplating solution in a 250 ml Erlenmeyer flask.
2. Add 100 ml of deionized water or distilled water.
3. Add 10 ml of concentrate. ammonia.
4. Add 0.2 g of Murexide indicator.
5. Titrate with 0.05 M EDTA standard solution while adding EDTA solution while rotating the flask. The color change is the end point from yellow to purple.
6. Note the amount of EDTA consumed.
The amount of nickel present = the number of milliliters of the EDTA solution X the molar concentration of EDTA X 29.35 = g/liter-"A"
(Note: The atomic weight of Ni = 58.69 and the molecular weight of Nicl₂.6H₂O = 237.70)
The content of Nicl₂.6H₂O: = "A" (237.70 / 58.69) = "A' x 4.05 = g/L
2. Nickel chloride Nicl2.6H2O
a. 20% ammonium acetate-CH 3 COONH 4: In a clean glass beaker, dissolve 200 g of ammonium acetate CH 3 COONH 4 in 1000 ml of deionized water by stirring. Store it in a glass or polyethylene bottle; mark it with content and date.
Sodium chromate-Na₂CrO₄ indicator: add 2.0 g of sodium chromate to 100 ml of deionized water, stir to fully dissolve. Transfer and store it in a clean polyethylene bottle, mark the contents and date.
C. 0.1 N Ag NO₃ (silver nitrate) standard solution: Add 700 ml of distilled water to a 1 liter volumetric flask, and add 5 ml of Conc. Nitric acid₃. Add 17 grams of silver nitrate Ag NO₃ to AR, stir well until it is completely dissolved. After mixing well, dilute to the mark with distilled water. Store in an amber glass bottle, indicating the concentration and date. This must be standardized using 0.1 N KCl (potassium chloride) as follows:
1. Pipette 25 ml 0.1N KCl into an Erlenmeyer flask
2. Add 25 ml deionized water and 5 ml 20% ammonium acetate
3. Add 1 ml of sodium chromate indicator.
4. Stir and titrate with silver nitrate until the precipitated silver chromate turns pink.
Ag NO₃ equivalent = KCl ml XKCl equivalent / AgNO₃ ml
Nicl₂.6H₂O procedure:
1. Pipette 5 ml of electroplating solution in a 250 ml Erlenmeyer flask.
2. Add 100 ml of deionized water or distilled water.
3. Add 10 ml of 20% ammonium acetate.
3. Add 2 ml of sodium chromate indicator solution.
4. Titrate with 0.1 N Ag NO₃ standard solution to the permanent pale pink end point, because silver chromate will be formed. Ag₂CrO₄.
5. Write down the volume of 0.1 N Ag NO₃ consumed.
ml Ag NO₃ X Ag NO₃ X 23.75 equivalent = g/L Nicl₂.6H₂O - "B"
Note: The molecular weight of Nicl2.6H2O = 237.70; the atomic weight of Ni = 58.69
a) Concentrated hydrochloric acid, LR or AR grade
Make a slurry of 3 grams of soluble starch in a small amount of cold water, then add it to about 300 ml of boiling water and stir well to mix well. Boil for 3 to 5 minutes. Cool to room temperature and store it in a clean glass or polyethylene bottle with an appropriate label and date. A small amount of mercury oxide can be added to prevent mold growth.
c) 0.1 N iodine (standard volume solution):
Dissolve 40 g of KI (potassium iodide) in 30 ml of distilled water in a 250 ml beaker. Accurately weigh 12.69 grams of iodine crystals, add them to the above KI solution and stir to dissolve them until they are completely dissolved. Transfer this solution to a 1000 ml volumetric flask and make up to volume with distilled or deionized water. Transfer this solution to a brown bottle. After marking the concentration of the iodine solution with grams per liter and the date, place the solution in a dark place on the table.
Use a 0.1 N As2 O3 solution to standardize this solution as follows:
Standardization of I2 solution:
Take 30 grams of arsenic oxide in the weighing bottle. Heat at 110oC for 2 hours. Cool in a desiccator. Add 4 g of KOH to 50 ml of deionized water in a 250 ml beaker. Dissolve it by stirring. Weigh out 4.9 to 5.0 grams of As2 O3 and record the exact weight. Add it to the above KOH solution to dissolve, and heat to lukewarm. After it is completely dissolved, carefully add 50% H2SO4 solution dropwise until the solution is neutral to phenolphthalein (dissolve 1 g of phenolphthalein in 100 ml of isopropanol and place it in a dropper bottle) and the indicator becomes colorless. Cool and transfer it to a 1000 ml volumetric flask, and fill up to the mark with distilled or deionized water. Transfer and store it in a glass or polyethylene bottle with the concentration, grams per liter and date on the label.
Transfer 25.0 ml of As2 O3 solution to a 250 ml Erlenmayer flask, and add about 2 gms sodium bicarbonate, 50 ml distilled or deionized water and 2 to 3 drops of 1% starch indicator. While rotating, titrate with iodine to the first blue end point, which is maintained for at least 30 to 60 seconds.
N = the number of milliliters of As2 O3 XN of As2 O3 / milliliters of I2.
d) 0.1 N Na2S2O3.5 H2O-sodium thiosulfate solution:
Dissolve 24.8 g of Na2S2O3.5 H2O in 700 ml of pre-boiled and cooled distilled or deionized water in a 1000 ml volumetric flask. Stir, dissolve and dilute to the mark. Mix well and transfer it to a glass or polyethylene bottle. Mark with the normality of Na2S2O3.5 H2O and gm/L, mark the date and save it.
Use 0.1N KIO3 solution to standardize 0.1 N Na2S2O3 as follows:
Preparation of 0.1 N KIO3 solution:
Draw 25.0 ml KIO3 potassium iodate standard solution in a 250 ml Erlenmeyer flask. Add 30 ml distilled water or DI water and 1 gm KI-potassium iodide and 10 ml 25% H2SO4 solution. Rotate with the above 0.1 N sodium thiosulfate solution to light yellow. Add 2 ml starch reagent and continue titration until the blue color disappears.
Calculation: N of Na2S2O3=ml of KIO3×N of KIO3/ml of Na2S2O3
Preparation of KIO3 standard solution:
Dry approximately 30 grams of KIO3 AR in a weighing bottle at 180oC for 2 hours, and then cool in a desiccator. Dissolve 1 g of NaOH and 10 g of KI in 200 ml of distilled water in a 500 ml beaker. Weigh 3.5 grams of KIO3 and add it to the beaker and stir to dissolve. Transfer this solution to a 1000 ml volumetric flask and dilute to the mark. Store it in a glass bottle and label it with N. of KIO3 and gms/L of KIO3.
N of KIO3 = weight of KIO3 / 35.67
Analysis steps of sodium hypophosphite:
1. Pipette 5.0 ml of bath (pre-cooled) into an iodine bottle.
2. Add 50 ml of concentrated hydrochloric acid.
3. Transfer 50.0 ml of 0.1 N iodine into the flask. Stopper the flask and shake.
4. Place in a dark cabinet for 30 minutes.
5. Titrate with 0.1 N sodium thiosulfate to a pale straw color.
6. Add a few drops of newly prepared 1% starch indicator solution and continue titration
To a clear end.
g/L Sodium Hypophosphite = {(ml of I2 XN of I2)-(ml of thio x N ofthio)} x 10.6
DI = deionized water; AR = analytical reagent; wt = weight; gm(s) = grams (s); ml = milliliters; N = normality; M = molar concentration; gpl or gms/L = grams per liter ; Mpl or ml/L = milliliters/liter.
Maintenance of working fluid:
After the analysis, the smaller amount can be compensated by adding a solution of nickel chloride and sodium hypophosphite.
Stock solution A:
Dissolve the following chemicals in 10 liters of DI water, and store them in a 2 X 5 liter capacity PVC bottle with a lid, place in a cool place, label it as solution "A", and indicate the date:
2. DL-malic acid-180 g
3. Boric acid-20 grams
Stock Solution B: Dissolve the following chemicals in 10 liters of DI water, and store them in a 2 X 5 liter capacity PVC vial with a lid, place in a cool place, label it as solution "B" and indicate the date:
1. Sodium hypophosphite-140 g
2. Acetic acid – 220 ml
3. Glycine-70 grams
The stock solutions "A" and "B" can be stored for 3 to 6 months if they are capped and stored properly.
After removing the load, add solutions "A" and "B" according to the analysis report. Adjust the solution to the desired pH value.
It is not recommended to add chemicals when loading or working in the tank, which may cause coarse deposition of eNi and/or spontaneous precipitation of spongy nickel at the high temperature of the working bath.
Precautions to be taken before the working tank is closed and started:
1. Before shutting down, cool the solution to below the working temperature, such as 50o to 55oC, and then add 100 ml of glycine solution (1 g per liter of glycine stock solution) to the working electroless nickel bath to avoid possible automatic deposition of nickel on On the walls of process vessels, pipes, cooling coils, etc. With this precaution, the bath can be easily maintained for more than 100 days.
2. Lower the pH value below the working pH value before closing the bath.
3. Always use a suitable pH meter to check the pH by electrical measurement.
4. When the solution is not in use, it must be covered with a suitable cover to prevent dust particles from falling into the bath.
5. When closing, do not leave any work or dummy in the bathtub unattended.
6. In order to obtain a better effect and a stable bath life, the solution can be cooled and transferred to a clean storage tank, and the air can be stirred gently to store it when the bath is not in use.
7. No trace of activator enters the bath.
8. Before starting the bath, analyze the nickel content and sodium hypophosphite content and pH. According to the analysis report, add the required nickel chloride solution and sodium hypophosphite solution, adjust the pH with 10% NaOH or 20% Hcl solution, and heat the solution to working temperature.
9. When working in solution, do not add maintenance chemical solution. Remove the work and add the necessary chemical solutions under stirring to maintain the bath.
10. Keep the hooks and fixtures clean; peel them off and clean them before loading.
11. Do not drag the solution into the working solution along with the job. This is to maintain the pH of the working solution.
12. Check the pH value of each batch of electroplating solution and adjust it with NaOH or hydrochloric acid solution if necessary. While adding 10% NaOH solution, stir well to avoid the formation of Ni(OH)2 nickel precipitate; continuous stirring may dissolve it.
13. Start electroplating on the model for 20-25 minutes, and then you can load regular jobs for eNi. plating.
14. It is recommended to use rod motion for gentle air agitation.
The addition of chemicals and the life of the bath completely depend on the production volume taken out and the careful maintenance of the bath after chemical analysis. At the most attention should be paid to avoid the unnecessary "seeding" phenomenon caused by dust and dirt falling into the bath.
When the bath is not in use, lower the working pH and close the lid.
This formula is very useful for the mass production of eNi plating of automotive, electrical, electronic and mechanical parts.
Tiny parts-washers, screws, etc., can be easily plated with eNi by barrel plating, while larger parts-bumpers, and mechanical parts of the machine can be plated with rack plating.
Dr. Krishna Ram Thoguluva Seshadri is an expert with 4 years of experience in the fields of electroplating, metal surface treatment, anodizing, surface treatment, electroless copper plating, electroless nickel plating, ENIG for PCB, tin sinking, and silver sinking. He is currently an expert consultant for printed circuit boards, electroplating and surface treatment in India and South Africa.
Prior to this, he served as the deputy general manager of the government department of ECIL-India Electronics Corporation Limited-A. Worked in the Ministry of Atomic Energy of India for 33 years and served as CEO (Technical Business) at Meena Circuits Pvt. Ltd., Vadodara, India for 3.5 years; now staying in Johannesburg, South Africa as a senior electroplating and PCB consultant. He is the Vice President of Impex Innovations in India and South Africa, an excellent import and export company. Contact: drtskram@yahoo.com
1. Edited by Arthur K. Graham, Electroplating Engineering Manual, Second Edition, 1962.
2. Kenneth E. Langford, Analysis of Electroplating and Related Solutions, 4th Edition, Teddington, Draper, 1971.
3. Jothi Sudagar, Jianshe Lian, Wei Sha, "Electroless Nickel, Alloys, Composites, and Nano-Coatings-A Critical Review" Journal of Alloys and Compounds, Vol. 571, (2013), 183-204. http://dx.doi.org/10.1016/j.jallcom.2013.03.107
4. A. Brenner, GE Riddell, Proc. Yes. Electrician Society. 33 (1946) 16–19
5. GG Gawrilov, chemical (electroless) nickel plating, Portcullis Press, Redhill, UK, 1979
6. GO Mallory, JB Hajdu, Electroless Plating: Basics and Applications, William Andrew, 1990
7. http://corrosion-doctors.org/MetalCoatings/Electroless.html
8. ASTM B733-04(2009) Standard Specification for Autocatalytic (Electroless) Nickel Phosphorus Coating on Metal
9. The electroless plating of Glenn O Mallory and Juan B Hajdu, ISBN 10: 0815512175;
10. Wolfgang Riedel's electroless nickel plating. ISBN-10: 0904477126;
ISBN-13: 978-0904477122
11. Chemical (Electroless Plating)-Nickel Plating, Georgi G Gavrilov, 1979
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