At present, electroplating technology is widely used in various fields of national production, and only careful operation can effectively save energy and protect the environment. Here is a brief introduction to some basic knowledge about electroplating process. Electroplating process classification: acid bright copper electroplating nickel/gold electroplating tin.
Process flow: pickling → full plate copper electroplating → acid degreasing → micro etching → pickling → tin plating → pickling → pattern copper plating → nickel plating → citric acid dipping → gold plating.
Process description.
(1) Pickle.
① Function and purpose: remove the surface oxides and activate the surface. The general concentration is about 5%~10%, mainly to prevent the unstable sulfuric acid content of the tank liquid caused by the introduction of water.
② C. P grade sulfuric acid shall be used, and the pickling time shall not be too long to prevent oxidation of the board surface; After a period of use, if the acid solution is turbid or the copper content is too high, it should be replaced in time to prevent pollution to the surface of the electroplating copper cylinder and plate.
(2) The whole plate is plated with copper.
① Function and purpose: Protect the thin chemical copper just deposited, prevent it from being eroded by acid, and add it to a certain extent by electroplating.
② Relevant process parameters of copper electroplating on the whole plate: the main components of the bath solution are copper sulfate and sulfuric acid. The formula of high acid and low copper is adopted to ensure the uniformity of the thickness distribution of the plate surface and the deep plating ability for deep holes during electroplating; The content of sulfuric acid is mostly 180 to 240 g/l; The content of copper sulfate is generally about 75g/L, and there can be a trace of chloride ions in the bath solution, which can be used as an auxiliary luster agent and a copper luster agent to play a luster effect together; The addition amount of copper polish is 3~5ml/L. The copper polish is generally supplemented according to the method of kiloampere hour or the actual production board effect; The current of full plate electroplating is generally calculated by multiplying 2 A/square decimeter by the electroplating area on the plate; The temperature of copper cylinder is generally controlled at 22~32 ℃.
③ Process maintenance: replenish copper polish according to kiloampere hours every day; Check whether the filter pump works normally; Wipe the cathode conducting rod with a clean wet rag every 2-3 hours; Regularly analyze every week and adjust the content of the polish through the Hall cell test; Clean the anode conducting rod and electric joints at both ends of the tank every week, and replenish the anode copper ball in the titanium basket in time; Check whether the titanium basket bag of anode is damaged every month and replace it in time; Check whether there is anode mud at the bottom of anode titanium basket; Whether major treatment is required depends on the tank liquid pollution condition every half a year or so; Replace the filter element of the filter pump every two weeks.
④ The anode copper ball contains a small amount of phosphorus to reduce the anodic dissolution efficiency and reduce the generation of copper powder.
⑤ When replenishing drugs, if a large amount of copper sulfate or sulfuric acid is added, it should be slowly added in several times; Otherwise, the temperature of the bath solution will be too high, the decomposition of the polish will be accelerated, and the bath solution will be polluted.
(3) Acid degreasing.
① Purpose and function: remove the oxide on the copper surface of the circuit, and ensure the adhesion between the primary copper and the pattern electroplating copper or nickel.
② When acid degreaser is used, only the concentration and time of the degreaser need to be controlled during production.
(4) Microetch.
① Purpose and function: Clean and roughen the copper surface of the circuit to ensure the binding force between the pattern electroplating copper and the primary copper.
② Sodium persulfate is used as the micro etchant.
(5) Pickle.
① Function and purpose: remove the oxides on the board surface to prevent the unstable sulfuric acid content of the tank liquor caused by the introduction of water.
② C. P grade sulfuric acid shall be used for pickling, and the time shall not be too long to prevent oxidation.
(6) Pattern electroplating copper, also called secondary copper.
Purpose and function: In order to meet the rated current load of each line, each line and hole copper needs to reach a certain thickness. Line copper plating is to thicken the hole copper and line copper to a certain thickness.
(7) Electrotinning.
① Purpose and function: The purpose of pattern electroplating of pure tin is to use pure tin as a metal anti-corrosive layer to protect the circuit etching.
② The bath solution is mainly composed of stannous sulfate, sulfuric acid and additives; The stannous sulfate content shall be controlled at about 35g/L, and the sulfuric acid content shall be controlled at about 10%; Tin plating additives are generally added according to the method of kiloampere hours or according to the actual production board effect; The current of electrotinning is generally calculated by multiplying 1.5 A/square decimeter by the electroplating area on the plate; The temperature of tin cylinder is maintained at room temperature, which is generally controlled at 22~30 ℃. Therefore, a cooling temperature control system can be installed in summer due to too high temperature.
③ Process maintenance: timely supplement tin plating additives according to kiloampere hours every day; Check whether the filter pump works normally; Clean the cathode conducting rod with a clean wet rag every 2-3 hours; Regularly analyze and adjust tin plating additive content through Hall cell test every week; Clean the anode conducting rod and electric joints at both ends of the tank every week; Check whether the anode bag is damaged every month and replace it in time; Check the anode mud at the bottom of the anode bag; Replace the filter element of the filter pump every two weeks.
④ The process of drug supplement is the same as above and will not be described in detail.
(8) Nickel plating.
① Purpose and function: The nickel plating layer is mainly used as the barrier between the copper layer and the gold layer to prevent the mutual penetration of gold and copper, affecting the weldability and service life of the board; At the same time, the nickel layer also greatly increases the mechanical strength of the gold layer.
② Relevant process parameters of copper electroplating for whole plate: nickel plating additives are generally added according to the method of kiloampere hours or according to the actual production effect of the plate, with the addition amount of about 200ml/KAH; The current of pattern nickel electroplating is generally calculated by multiplying 2 A/square decimeter by the electroplating area on the plate; The temperature of nickel cylinder is maintained between 40 and 55 degrees.
③ Process maintenance: timely supplement nickel plating additives according to kiloampere hours every day; Check whether the filter pump works normally; Clean the cathode conducting rod with a clean wet rag every 2-3 hours; Regularly analyze every week and adjust the content of nickel plating additives through Hall cell test to timely supplement; Clean the anode conducting rod and electric joints at both ends of the tank every week, replenish the anode nickel angle in the titanium basket in time, and electrolyze with low current for 6-8 hours; Check whether the titanium basket bag of anode is damaged every month and replace it in time; Check whether there is anode mud at the bottom of anode titanium basket; Replace the filter element of the filter pump every two weeks.
⑤ The process of drug supplement is the same as above and will not be described in detail.
(9) Electrogilding: divided into hard gold plating and water gold plating processes. The bath composition is basically the same. There are some trace elements such as nickel, cobalt and iron in the hard gold bath.
① Purpose and function: Gold is a precious metal, which has the characteristics of weldability, oxidation resistance, corrosion resistance, low contact resistance, and good wear resistance of alloy.
② At present, the circuit board is mainly electroplated with citrate gold bath, which is easy to maintain and operate.
③ The gold content in water is controlled at about 1g/L, the pH value is about 4.5, and the temperature is about 35 °.
④ The main additives include acid type adjustment salt, basic type adjustment salt, conductive salt, gold plating supplementary additive and gold salt.
⑤ After electroplating, the gold plate shall be washed with pure water as the recovery water, which can also be used to supplement the liquid level of the evaporation change of the gold cylinder.
⑥ Platinum plated titanium mesh shall be used as anode for the gold cylinder.
⑦ The organic pollution of the gold cylinder shall be continuously filtered by carbon core, and an appropriate amount of gold plating additives shall be added.