A, the classification of electroplating process:

Acid bright copper, nickel, gold and tin plating.

2. Process flow:

Pickling → copper electroplating on the whole board → pattern transfer → acid degreasing → secondary countercurrent rinsing → micro-etching → secondary.

→ Pickling → Tin plating → Two-stage countercurrent rinsing.

Countercurrent rinsing → pickling → pattern copper electroplating → two-stage counter-current rinsing.

→ nickel plating → secondary water washing → citric acid soaking → gold plating → recycling →2-3 times pure water washing → drying.

Three. Process description:

(1) pickling

① Function and purpose:

Remove the oxide on the board surface and activate the board surface. Generally, the concentration is 5%, and some of it is kept at around 10%, mainly to prevent the sulfuric acid content in the tank solution from being unstable due to moisture.

(2) The acid leaching time should not be too long to prevent surface oxidation; After using for a period of time, if the acid solution is turbid or the copper content is too high, it should be replaced in time to prevent the surface of copper plating drum and plate from being polluted;

③ C.P grade sulfuric acid should be used here;

(2) Copper plating on the whole board: also known as primary copper plating and panel electroplating ① Functions and uses:

Protect the newly deposited thin chemical copper and prevent the chemical copper from being corroded by acid after oxidation, and add it to a certain extent through electroplating.

(2) Process parameters related to copper electroplating on the whole plate: the bath solution is mainly composed of copper sulfate and sulfuric acid, and the formula of high acid and low copper is adopted to ensure the uniformity of plate thickness distribution and deep plating ability for deep holes and small holes during electroplating; The content of sulfuric acid is mostly 180g/L, and most of them reach 240g/L; The content of copper sulfate is generally about 75g/L. Adding a small amount of chloride ion into the bath solution can be used as an auxiliary brightener and a copper brightener to exert the luster effect. The amount of copper brightener added or the amount of cylinder opening is generally 3-5ml/L, and the amount of copper brightener added is generally supplemented according to the method of thousand ampere hours or according to the actual production effect of the plate; Generally, the galvanometer for full-plate electroplating is calculated as 2a/ square decimeter multiplied by the electroplating area on the plate. The electricity consumption of the whole board is calculated as board length dm× board width dm×2×2A/ DM2; ; The temperature of the copper cylinder is kept at room temperature, generally not exceeding 32 degrees, and controlled at 22 degrees. Therefore, it is suggested to install a cooling temperature control system for the copper cylinder because the temperature is too high in summer.

③ Process maintenance:

Supplementing copper brightener in time every day according to thousand ampere hours, according to100-150ml/kah; Check whether the filter pump works normally and whether there is air leakage; Clean the cathode conductive rod with a clean wet rag every 2-3 hours; Regularly analyze the contents of copper sulfate (1 time/week), sulfuric acid (1 time/week) and chloride ion (2 times/week) in the copper cylinder every week, adjust the content of brightener through Hall cell test, and replenish relevant raw materials in time; Clean the electrical connectors at both ends of the anode conductive rod and groove every week, and replenish the anode copper balls in the titanium basket in time, using 0. 2—0。 5ASD electrolysis for 6-8 hours; Check whether the anode titanium basket bag is damaged every month, and replace it in time if it is damaged; And check whether there is anode mud accumulation at the bottom of anode titanium basket, and clean it in time if there is; Continuously filtering with carbon core for 6-8 hours, and removing impurities with small current; Every six months or so, according to the pollution situation of tank liquid, it is decided whether it is necessary to carry out large-scale treatment (activated carbon powder); Replace the filter element of the filter pump every two weeks; ]

④ Large-area treatment procedure: a. Take out the anode, pour it out, clean the anode film on the anode surface, then put it into a barrel for packaging the copper anode, roughen the copper corner surface to uniform pink with a micro-corrosive agent, then put it into a titanium basket and put it into an acid tank for later use. B, soak the anode titanium basket and anode bag in 10% alkaline solution for 6-8 hours, rinse them with water, and then use 5% alkaline solution. C, transferring the tank liquid to a standby tank, adding 30% hydrogen peroxide of 1-3ml/L, and starting heating; when the temperature reaches about 65 degrees, turning on the air to stir and keeping the temperature for 2-4 hours; D, turning off the air for stirring, slowly dissolving the activated carbon powder into the bath solution at the speed of 3-5g/L, and after the solution is completely dissolved, turning on the air for stirring and keeping the temperature for 2-4 hours; E, turning off the gas, stirring and heating, so that the activated carbon powder slowly precipitates to the bottom of the tank; F. When the temperature drops to about 40 degrees, use 10um PP filter element and filter powder to filter the bath solution into a clean working tank, turn on the air to stir, put it in the anode, hang it in the electrolytic plate, and press 0. 2-0。 5ASD current density, low current electrolysis for 6-8 hours, g. After laboratory analysis, adjust the contents of sulfuric acid, copper sulfate and chloride ion in the tank to the normal operating range; Judging the performance of the battery according to the test result of the Hall element; H. When the color of the electrolytic plate is uniform, stop the electrolysis, and then press 1- 1. Electrolytic film-forming treatment was carried out for 65438 0-2 hours at a current density of 5ASD until a uniform and dense black phosphorus film with good adhesion was formed on the anode; First, try plating OK;

⑤ Anode copper ball contains 0. 3—0。 6% phosphorus, the main purpose is to reduce the anode dissolution efficiency and reduce the production of copper powder;

⑥ When supplementing drugs, such as adding a lot of copper sulfate and sulfuric acid; Small current electrolysis is needed after adding; Pay attention to safety when adding sulfuric acid. When adding a large amount (10 liter or more), slowly add it several times; Otherwise, the bath temperature will be too high, which will accelerate the decomposition of photocatalyst and pollute the bath body;

⑦ Pay special attention to the addition of chloride ion, because the chloride ion content is particularly low (30-90ppm), and it must be accurately weighed with a measuring cylinder or a measuring cup before adding; 1 ml hydrochloric acid contains about 385ppm of chloride ions,

⑧ Dosing calculation formula:

Copper sulfate (unit: kg) =(75-X)× tank volume (liter)/1000.

Sulfuric acid (unit: liter) =( 10%-X) g/liter× tank volume (liter)

Or (unit: liter) =( 180-X)g/L× tank volume (liter)/1840.

Hydrochloric acid (unit: ml) =(60-X)ppm× tank volume (liter) /385.

(3) Acid degreasing

Usage and function: remove the oxidation on the surface of circuit copper and the residual glue of ink film, and ensure the bonding force between primary copper and copper or nickel plating on the pattern.

② Remember that the acid degreaser is used here, why not use the alkaline degreaser and the degreasing effect of the alkaline degreaser is better than that of the acid degreaser? main reason

2. Because graphic ink is not alkali-resistant, it will damage the graphic circuit, so only acidic degreasing agent can be used before graphic electroplating.

③ Only the concentration and time of degreasing agent need to be controlled in the production process. The concentration of degreasing agent is about 10%, and the time is guaranteed to be 6 minutes. A little longer time will not have adverse effects; The use and replacement of bath fluid are also in accordance with 15m2/L working fluid, and the supplementary addition is in accordance with 100m2. 5—0。 8L；

(4) Micro-etching:

Purpose and function: Clean the copper surface of the roughened circuit to ensure the bonding force between the patterned electroplated copper and the original copper.

② Sodium persulfate is mostly used as a micro-etchant, with stable and uniform coarsening rate and good washability. Generally, the concentration of sodium persulfate is controlled at about 60g/L, and the time is controlled at about 20s. The dosage is 65438+3-4kg/m2. The copper content is controlled below 20g/L; Other maintenance and cylinder replacement are the same as copper corrosion.

(5) curing

① Function and purpose:

Remove the oxide on the board surface and activate the board surface. Generally, the concentration is 5%, and some of it is kept at around 10%, mainly to prevent the sulfuric acid content in the tank solution from being unstable due to moisture.

(2) The acid leaching time should not be too long to prevent surface oxidation; After using for a period of time, if the acid solution is turbid or the copper content is too high, it should be replaced in time to prevent the surface of copper plating drum and plate from being polluted;

③ C.P grade sulfuric acid should be used here;

(6) Copper plating for patterns: also called secondary copper plating, copper plating for lines.

Purpose and function: in order to meet the rated current load of each line, each line and hole need to reach a certain thickness after copper plating. The purpose of copper plating on the line is to thicken the hole copper and line copper to a certain thickness in time;

(2) Other items are the same as the whole plate electroplating.

7) purpose and function of tin electroplating ①: The purpose of pattern electroplating of pure tin is mainly to use pure tin as a metal anticorrosion layer to protect circuit etching;

② The bath solution is mainly composed of stannous sulfate, sulfuric acid and additives; The content of stannous sulfate is controlled at about 35g/L, and the sulfuric acid is controlled at about 65438 00%. Tin plating additives are generally added according to the method of thousands of ampere hours or according to the actual production effect of the plate; At present, the calculation of tin electroplating is generally 1. 5 amps/square decimeter multiplied by the electroplating area on the board; The temperature of the tin tube is maintained at room temperature, generally not exceeding 30 degrees, and controlled at 22 degrees. Therefore, due to the high temperature in summer, it is recommended to install a tin tube cooling temperature control system.

③ Process maintenance:

Timely supplement tin plating additives according to thousand ampere hours every day; Check whether the filter pump works normally and whether there is air leakage; Every 2-3 hours, scrub the cathode conductive rod with a clean wet rag; Analyze stannous sulfate (1 time/week) and sulfuric acid (1 time/week) regularly every week, adjust the content of tin plating additives through Hall cell test, and replenish relevant raw materials in time; Clean the anode conductive rod and the electrical connectors at both ends of the groove every week; Use low current 0 every week. 2—0。 5ASD electrolysis for 6-8 hours; Check the anode package for damage every month, and replace it in time if it is damaged; And check whether there is anode mud accumulation at the bottom of the anode bag, and clean it in time if there is; Continuously filter with carbon core for 6-8 hours every month, and remove impurities with low current electricity at the same time; Every six months or so, according to the pollution situation of tank liquid, it is decided whether it is necessary to carry out large-scale treatment (activated carbon powder); Replace the filter element of the filter pump every two weeks;

⑨ Main treatment procedures: a. Take out the anode, take down the anode bag, clean the anode surface with a copper brush, rinse it with water, put it into the anode bag and put it into an acid tank for later use. B, soaking the anode in 10% alkali solution for 6-8 hours, washing it with water, soaking it with 5% dilute sulfuric acid, and washing it with water for later use; C. Transfer the bath solution to a standby bath, slowly dissolve the activated carbon powder into the bath solution at a speed of 3-5g/L, and after the solution is completely dissolved, adsorb for 4-6h, filter the bath solution with a PP filter core and filter powder of 10um, put it in the anode, and hang it in the electrolytic plate, and press 0. 2-0。 5ASD current density and low current electrolysis for 6-8 hours. D. After laboratory analysis, adjust the contents of sulfuric acid and stannous sulfate in the tank to the normal operating range; According to the results of Hall cell test, tin plating additives are supplemented; E, stopping electrolysis after the surface color of the electrolytic plate is uniform; F. the test plating is qualified.

(4) when adding drugs, such as adding a lot of stannous sulfate and sulfuric acid; Small current electrolysis is needed after adding; Pay attention to safety when adding sulfuric acid. When adding a large amount (10 liter or more), slowly add it several times; Otherwise, the bath temperature is too high, and stannous is oxidized, which accelerates the aging of the bath;

⑤ Dosing calculation formula:

Stannous sulfate (unit: kg) =(40-X)× tank volume (liter)/1000.

Sulfuric acid (unit: liter) =( 10%-X) g/liter× tank volume (liter)

Or (unit: liter) =( 180-X)g/L× tank volume (liter)/1840.

(9) Nickel plating

Usage and function: Nickel plating layer is mainly used as a barrier between copper layer and gold layer to prevent the mutual diffusion of gold and copper and affect the solderability and service life of circuit board; At the same time, the priming of nickel layer greatly increases the mechanical strength of gold layer;

(2) Process parameters related to copper electroplating on the whole plate: The addition of nickel plating additives is generally supplemented according to the method of thousand ampere hours or according to the actual production effect of the plate, and the addition amount is about 200 ml/kah; The current calculation of pattern nickel plating is generally calculated by multiplying the plating area on the plate by 2a/ square decimeter; The temperature of the nickel cylinder is maintained at 40-55 degrees, and the general temperature is about 50 degrees, so the nickel cylinder should be equipped with a heating and temperature control system;

③ Process maintenance:

Replenish nickel plating additives in time according to thousand ampere hours every day; Check whether the filter pump works normally and whether there is air leakage; Every 2-3 hours, scrub the cathode conductive rod with a clean wet rag; Periodically analyze the contents of nickel sulfate (nickel sulfamate) (1 time/week), nickel chloride (1 time/week) and boric acid (1 time/week) in the copper cylinder every week, adjust the contents of nickel plating additives through Hall cell test, and replenish relevant raw materials in time; Clean the electrical connectors at both ends of anode conductive rod and groove every week, and replenish the anode nickel angle in titanium basket in time, using 0. 2—0。 5ASD electrolysis for 6-8 hours; Check whether the anode titanium basket bag is damaged every month, and replace it in time if it is damaged; And check whether there is anode mud accumulation at the bottom of anode titanium basket, and clean it in time if there is; Continuously filtering with carbon core for 6-8 hours, and removing impurities with small current; Every six months or so, according to the pollution situation of tank liquid, it is decided whether it is necessary to carry out large-scale treatment (activated carbon powder); Replace the filter element of the filter pump every two weeks; ]

④ Large-scale treatment procedure: a. Take out the anode, pour it out, clean it, then put it into a barrel for packaging nickel horns, roughen the surface of nickel horns with a micro-corrosive agent until they are even pink, then put it into a titanium basket and put it into an acid tank for later use. B, soaking the anode titanium basket and anode bag in 10% alkali solution for 6-8 hours, washing with water and drying, and then using 5% dilute sulfuric acid. C, transferring the tank liquid to a standby tank, adding 1-3ml/L of 30% hydrogen peroxide, and starting heating; when the temperature reaches about 65 degrees, turning on the air for stirring and keeping the temperature for 2-4 hours; D, turning off the air for stirring, slowly dissolving the activated carbon powder into the bath solution at the speed of 3-5g/L, and after the solution is completely dissolved, turning on the air for stirring and keeping the temperature for 2-4 hours; E, turning off the gas, stirring and heating, so that the activated carbon powder slowly precipitates to the bottom of the tank; F. When the temperature drops to about 40 degrees, use 10um PP filter element and filter powder to filter the bath solution into a clean working tank, turn on the air to stir, put it in the anode, hang it in the electrolytic plate, and press 0. 2-0。 5ASD current density, low current electrolysis for 6-8 hours, g. After laboratory analysis, adjust the contents of nickel sulfate or nickel sulfamate, nickel chloride and boric acid in the tank to the normal operation range; Supplementing nickel plating additives according to the Hall cell test results; H. When the color of the electrolytic plate is uniform, stop the electrolysis, and then press 1- 1. Electrolytic treatment 10-20min at a current density of 5ASD to activate the anode; First, try plating OK;

⑤ When adding drugs, if the amount is large, such as nickel sulfate or nickel sulfamate, nickel chloride, etc., small current electrolysis should be carried out after adding; When boric acid is added, the amount of boric acid added should be put into a clean anode bag and hung in a nickel cylinder, and it is not allowed to be directly added into the tank;

⑥ After nickel plating, it is suggested to add a circulating water washing, open the cylinder with pure water, which can be used to supplement the liquid level of the heated and volatilized nickel cylinder, and then carry out a secondary countercurrent rinsing after circulating water washing;

⑦ Dosing calculation formula:

Nickel sulfate (unit: kg) =(280-X)× tank volume (liter)/1000.

Nickel chloride (unit: kg) =(45-X)× tank volume (liter)/1000.

Boric acid (unit: kg) =(45-X)× tank volume (liter)/1000.

(10) Gold plating: it can be divided into hard gold plating (gold alloy) and water gold plating (pure gold). The composition of hard gold electroplating bath and soft gold electroplating bath is basically the same, except that the hard gold electroplating bath contains some trace elements such as nickel, cobalt or iron.

Uses and functions: As a precious metal, gold has good weldability, oxidation resistance, corrosion resistance, low contact resistance and good alloy wear resistance.

(2) At present, gold plating on circuit boards is mainly carried out in gold citrate bath, which is widely used because of its simple maintenance and convenient operation;

③ The content of water gold is controlled around 1g/L, and the PH value is 4. 5. The temperature is 35 degrees, the specific gravity is about 14 Baume, and the current density is about1ASD;

④ The main drugs added are acid salts and basic salts for adjusting PH value, conductive salts for adjusting specific gravity, auxiliary additives for gold plating and gold salts.

⑤ In order to protect the golden urn, a citric acid soaking tank should be added in front of the golden urn, which can effectively reduce the pollution to the golden urn and keep the golden urn stable;

⑥ After gold plating, pure water cleaning should be used as recovery water cleaning, and it can also be used to supplement the evaporation change level of the gold cylinder. After the recycled water washing, it should be followed by two-stage countercurrent pure water washing. After washing the gold plate, it should be put into 10g/L alkaline solution to prevent the gold plate from oxidation.

⑦ Platinum-plated titanium mesh should be used as anode of gold cylinder. Generally, 3 16 stainless steel is easy to dissolve, which leads to the pollution of gold cylinder by metals such as nickel, iron and chromium, resulting in defects such as whitening, exposure and blackening of gold plating.

⑧ The organic pollution of gold cylinder should be continuously filtered with carbon core, and appropriate gold plating additives should be added.