[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.
[0025] With the continuous advancement of science and technology, electronic products are constantly changing, and the PCB board as the carrier of the electrical connection of electronic components is also constantly updated. However, in the PCB electroplating process, due to the sharp effect of the current, the conductive part of the stainless steel hanger will form a thick copper and/or tin coating, which brings great inconvenience to the electroplating of the PCB. At this time, if you need to use the hanger again, you need to remove the plating on the hanger before you can use it. In the prior art, methods for deplating the surface of the hanger mainly include chemical deplating and electrolytic deplating. Among them, the chemical stripping method has a long stripping time, poor stripping effect, easy to damage the substrate, and a large amount of waste water is generated, which pollutes the environment; while the existing electrolytic stripping method cannot achieve copper plating on the rack At the same time as the efficient removal of tin plating and/or tin plating, the efficient recycling of copper plating and/or tin plating on the hanger is realized, and the corrosion phenomenon of the substrate occurs, which generates a lot of waste water.
[0026] Based on this, in order to solve the above technical problems, an embodiment of the present invention proposes an electrolytic deplating solution, which includes: nitrate, sulfuric acid, accelerator, copper corrosion inhibitor, hexamethylenetetramine , Urea and glycerin, the solvent is water. The copper corrosion inhibitor is one or a combination of benzotriazole, carboxybenzotriazole, tolyl benzotriazole, hydroxybenzotriazole or pyrrolidone.
[0027] In this embodiment, in order to achieve good electrical conductivity of the electrolytic deplating solution, nitrate is designed as the main medium of the deplating electrolyte, specifically, sodium nitrate is selected. At the same time, in order to enhance the oxidizability in the deplating electrolyte and to facilitate the removal of the tin plating layer, an accelerator is designed to promote the transformation of the dissolved divalent tin into the tetravalent tin insoluble in the electrolyte. Preferably, this embodiment In the example, ferric nitrate is used. In addition, in order to protect the metal copper layer deposited on the cathode stainless steel plate from being back-corroded when the power is off, a copper corrosion inhibitor is designed. Specifically, benzotriazole is selected in this embodiment. And through the synergy between hexamethylenetetramine, urea and glycerin, to achieve the corrosion protection and polishing effect on the substrate of the rack, so that the substrate of the rack automatically enters the passivation state after the deplating is completed. Not damaged by deplating electrolyte.
[0028] Further, the concentration of each of the above components is as follows:
[0029]
[0030] In another embodiment of the present invention, the electrolytic deplating solution includes the following components:
[0031]
[0032] The present invention also proposes a method for removing the copper layer and the tin layer on the hanger at the same time, using the electrolytic stripping solution according to claims 1-5, and the method includes the following steps:
[0033] 1) Put the rack with deplating into the electrolytic deplating solution and electrically connect the positive electrode of the rectifier as the anode, and put the stainless steel plate into the deplating solution and electrically connect the negative electrode of the rectifier as the cathode to form an electrolytic deplating system;
[0034] 2) Turn on the rectifier, apply DC voltage to the electrolytic deplating system, and start electrolytic deplating. The copper and/or tin coating on the surface of the rack begins to dissolve, and the metal copper ions in the electrolytic deplating solution gradually deposit on the stainless steel plate. The metal tin ions in the deplating solution form stannic acid that is insoluble in the electrolytic deplating solution, and the current of the electrolytic deplating system keeps decreasing;
[0035] 3) When the current of the electrolytic deplating system drops to a stable value, take it out and observe. If all the substrates of the rack are exposed, the electrolytic deplating process is complete;
[0036] 4) Take out the hanger for cleaning, and collect the copper layer on the surface of the stainless steel plate;
[0037] 5) The stannic acid in the electrolyte is precipitated, filtered, and recovered, and the supernatant electrolytic deplating solution after the stannic acid is treated is pumped into the electrolytic deplating system for deplating again.
[0038] Further, the electrolytic cell used in the electrolytic deplating system is made of PP and/or PPV. In step 2), the DC voltage output by the rectifier is 2-5V; and the initial anode current density of the electrolytic deplating system is 2-8A/dm 2.
[0039] In order to better illustrate the effects of the electrolytic deplating solution involved in the present invention, the following examples of specific components are selected as reference in the present invention.
[0040] The experimental components selected in the example group are as follows:
[0041]
[0042]
[0043] In this embodiment group, the selection control group component table is as follows:
[0044]
[0045] Wherein, the copper withdrawal speed (g/AH) is:
[0046]
[0047] The deplating conditions are electrolysis with a current of 1A, the mass unit is g, and the deplating time unit is H.
[0048] The stripping speed (g/AH) is:
[0049]
[0050] The deplating conditions are electrolysis with a current of 1A, the mass unit is g, and the deplating time unit is H.
[0051] The corrosion degree of stainless steel (g/AH) is:
[0052]
[0053] The deplating conditions are electrolysis with a current of 1A, the mass unit is g, and the deplating time unit is H.
[0054] The copper deposition purity (%: mass percentage) is obtained by X-ray detection of the copper layer recovered to the cathode.
[0055] The recovery rate (%: mass percentage) of the tin is:
[0056] The tin sludge is filtered and precipitated. After the filter residue is dried, the total mass of the tin sludge is weighed as M (unit: g), and the tin sludge with mass m (unit: g) is taken as a sample to obtain the tin sludge The mass percentage of tin w (%). Dissolve m (unit: g) tin sludge under high temperature conditions with sodium hydroxide and hydrogen peroxide, add hydrochloric acid to make the volume V (unit: L), and analyze the tetravalent tin concentration C (unit: g/L) by titration ), find:
[0057] The mass percentage of tin in tin mud
[0058] The recovery rate (%: mass percentage) of the tin is:
[0059]
[0060] The pungent odor is judged as follows: Fill the two climate chambers (A is a blank chamber, B is an experimental chamber) with the same amount of gas (A chamber is filled with clean air, and B is filled with a deplating liquid for deplating The ambient air at the same time), and evaluated according to the following odor evaluation standards, and the average value of 6 odor assessors was used as the evaluation of the pungent odor (the odor evaluation grade is expressed as an integer or half).
[0061] Smell criterion:
[0062] Level 1: Odorless
[0063] Level 2: Slight smell, but can be felt
[0064] Grade 3: Odor, but no strong discomfort
[0065] Level 4: strong unpleasant smell
[0066] Grade 5: pungent and uncomfortable smell
[0067] The deplating effect of using the deplating solution of the present invention in the above example group is as follows: (wherein% means: the mass percentage of the substance component in the electrolytic deplating solution)
[0068]
[0069]
[0070] The deplating effect of using the deplating solution of the present invention in the above-mentioned control group is as follows: (wherein% means: the mass percentage of the substance component in the electrolytic deplating solution)
[0071]
[0072]
[0073] According to the deplating effect data of the above-mentioned example group and control group, it is shown that as the concentration of sulfuric acid increases, the purity of the copper deposit of the electrolytic deplating solution and the recovery rate of tin have a certain promotion effect. When the concentration of sulfuric acid reaches 20g/ After L, the promotion effect remains basically unchanged, and as the concentration of sulfuric acid increases, the pungent odor produced by the electrolytic deplating solution is also increasing; as the concentration of sodium nitrate in the electrolytic deplating solution increases, the copper removal rate and The speed of tin stripping has a certain promotion effect; the iron nitrate in the electrolytic stripping solution has a certain promotion effect on the recovery rate of tin. With the further increase of the concentration of iron nitrate, the recovery rate of tin is further improved; The content of azole has a certain influence on the purity of the copper deposit in the electrolytic deplating solution. With the increase of the concentration of benzotriazole, the purity of copper in the copper deposit becomes higher and higher, reaching more than 94%; With the further increase in the concentration of hexamethylenetetramine, the corrosion rate of the stainless steel substrate also further decreases; glycerin also has a certain inhibitory effect on the corrosion of the stainless steel substrate, although the overall corrosion resistance effect is not as strong as that of hexamethylenetetramine , But glycerin has a good inhibitory effect on the pitting corrosion of the stainless steel substrate; with the increase of the urea concentration, the pungent odor that can be detected in the deplating environment is significantly weakened. When the urea concentration reaches a certain value, the The pungent odor is almost imperceptible, which effectively improves the harsh working environment where the pungent odor reaches level 5 in the existing deplating environment.
[0074] Optionally, when the concentration of sulfuric acid in the electrolytic deplating solution reaches 20 g/L, the concentration of ferric nitrate reaches 2 g/L, the concentration of sodium nitrate reaches 120 g/L, and the concentration of benzotriazole reaches 0.2 g/L in an embodiment of the present invention , When the concentration of hexamethylenetetramine reaches 2g/L, the concentration of urea reaches 2g/L, and the concentration of glycerol reaches 10g/L, the electrolytic deplating solution has the best copper and/or tin stripping effect, and the highest copper Purity and the maximum recovery of tin. At this time, the copper removal rate can reach 1.17g/AH, and the tin removal rate can reach 1.6g/AH; the purity of the copper deposition layer can reach 94% (mass percentage), and the tin recovery rate can reach 92 %. At the same time, it has the greatest protective effect on the stainless steel substrate and produces the least irritating gas. At this time, the corrosion degree of the stainless steel is 0.067g/AH, and the irritating smell is almost imperceptible.
