CN110777423B

CN110777423B - Tin stripping liquid and method for recovering tin

Info

Publication number: CN110777423B
Application number: CN201911045032.2A
Authority: CN
Inventors: 田宝龙; 杨保严; 王宗龙; 黄小露
Original assignee: Kunshan King Lead Environmental Protection Technology Co ltd
Current assignee: Suzhou Jinyide Environmental Protection Technology Co.,Ltd.
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2021-09-28
Anticipated expiration: 2039-10-30
Also published as: CN110777423A

Abstract

The invention discloses a tin stripping liquid and a method for recovering tin. The tin stripping liquid comprises 50g/L-340g/L of electrolyte, 5g/L-200g/L of tin salt, 1g/L-40g/L of antioxidant, and 1g/L-50g/L of stabilizer and dispersant, wherein the electrolyte comprises at least one of sulfuric acid and methanesulfonic acid. The tin stripping liquid does not contain nitric acid or contains a very small amount of nitric acid, so that the reaction is relatively smooth, a large amount of heat cannot be generated, and basically no gas is discharged, thereby reducing the pollution to the environment. In addition, the tin stripping liquid can recover tin in the tin stripping process, so that the operation cost is reduced, and the energy consumption is reduced.

Description

Tin stripping liquid and method for recovering tin

Technical Field

The invention belongs to the technical field of metal coating removal. In particular, the invention relates to a tin stripping solution and a method for recovering tin.

Background

Printed Circuit Boards (PCBs) are one of the important components in the electronics industry and are the supports for electronic components. Generally, a process of manufacturing a printed circuit board includes double-sided copper-clad → machining → copper-deposition → film-attachment → electrolytic copper-plating → electrolytic tin-plating → etching → tin-stripping → processing. In order to protect the conductive pattern from corrosion during the alkaline etching process, a corrosion-resistant tin metal is usually plated on the conductive pattern. When the etching is completed, the resist metal tin is removed.

In general, a tin stripping solution can be classified into three types, i.e., a fluoride type, a strong alkali type, and a nitrate type, according to its main components. The fluoride type tin stripping liquid mainly comprises hydrofluoric acid, villiaumite (ammonium bifluoride), peroxide and the like, and is basically eliminated due to poor environmental indexes (strong volatility of fluoride and serious pollution) and technical and economic indexes. The strong alkali type tin stripping liquid mainly comprises sodium hydroxide and sodium salt, or also comprises highly toxic cyanide and the like, and the strong alkali type tin stripping liquid is less used because the technical and economic indexes are general, the toxicity of the cyanide is high, and the harm to operators is great in the production process. The nitric acid type tin stripping liquid mainly comprises strong corrosive nitric acid, a corrosion inhibitor, a surfactant, a stabilizer and the like, and the total acid content in the nitric acid type tin stripping liquid is generally about 20-50%, so that the nitric acid type tin stripping liquid has the characteristics of high-speed tin stripping, high efficiency, durability, no damage to bottom copper, bright, ashless and white copper surface and the like.

Although the performance of the nitric acid type tin stripping solution is greatly improved in technical, economic and environmental indexes compared with fluoride type tin stripping solution and strong alkali type tin stripping solution, the nitric acid type tin stripping solution still has certain defects. Specifically, in the tin stripping process, nitric acid in the nitric acid type tin stripping liquid is reduced to NO₂、NO、NO_XNitrogen oxides and the like generate a large amount of toxic and harmful gases and the reaction process is severe; in addition, a large amount of heat is released, so that the temperature of the tin stripping solution rises rapidly, divalent tin ions are converted into metastannic acid white precipitates rapidly under the multiple actions of nitric acid, oxygen and temperature, and the tin stripping capacity of the nitric acid type tin stripping solution is reduced. From the tin stripping effect, in order to improve the tin stripping speed and the tin stripping capacity, the use amount of nitric acid is often increased, so that the reaction process of the nitric acid type tin stripping solution is violent and rapid, the plate surface after tin stripping is not fine enough, and particularly, the phenomenon of 'over-stripping' is easily caused, namely, certain corrosion is caused to copper while tin stripping is completed. Tin stripping is a process of generating the largest amount of waste liquid in PCB production enterprises, and the generated waste tin stripping liquid contains a large amount of residual nitric acid (15% -25%), by-product nitrous acid and other compounds, a certain amount of heterocyclic compounds, polycyclic aromatic additives and the like, so that the harm to the health and the ecological environment of a human body is very large. Therefore, the nitric acid type tin stripping liquid has the defects of large pollution, low efficiency, poor tin stripping effect, insufficient fineness, large waste liquid discharge amount, large harm and the like in the production process.

Therefore, a new tin stripping solution is needed.

Disclosure of Invention

The invention aims to provide a tin stripping solution and a method for recovering tin.

Another object of the present invention is to provide a tin stripping solution and a method of recovering tin that can solve at least one of the above problems.

According to one aspect of the invention, the tin stripping solution comprises 50g/L-340g/L of electrolyte, 5g/L-200g/L of tin salt, 1g/L-40g/L of antioxidant and 1g/L-50g/L of stabilizer and dispersant, wherein the electrolyte comprises at least one of sulfuric acid and methanesulfonic acid.

In an exemplary embodiment of the present invention, the electrolyte may include sulfuric acid and methanesulfonic acid, and the content of the sulfuric acid may be 20g/L to 120g/L and the content of the methanesulfonic acid may be 30g/L to 220g/L, based on the total volume of the solder stripper.

In exemplary embodiments of the present invention, the tin salt may include at least one of tin methanesulfonate and stannous sulfate.

In an exemplary embodiment of the present invention, the tin salt may include tin methanesulfonate and stannous sulfate, and the content of the tin methanesulfonate may be 2g/L to 120g/L and the content of the stannous sulfate may be 3g/L to 80g/L, based on the total volume of the tin stripping solution.

In exemplary embodiments of the present invention, the antioxidant may include at least one of carboxylic acid-based compounds and phenolic compounds.

In exemplary embodiments of the present invention, the carboxylic acid-based compound may include at least one of tartaric acid, citric acid, and salicylic acid, and the phenolic compound may include at least one of resorcinol, hydroquinone, and catechol.

In an exemplary embodiment of the present invention, the stabilizer may include at least one of hydrazine hydrate, phenolsulfonic acid and cresolsulfonic acid, and the dispersant may include at least one of polyoxypropylene ether, polyethylene glycol and gelatin, and the stabilizer may be included in an amount of 0.5g/L to 30g/L and the dispersant may be included in an amount of 0.5g/L to 20g/L, based on the total volume of the tin stripping solution.

In the exemplary embodiment of the invention, the tin stripping solution can further comprise sulfate with the content of 20g/L-30g/L based on the total volume of the tin stripping solution.

In an exemplary embodiment of the present invention, the sulfate may include at least one of sodium sulfate and potassium sulfate.

According to another aspect of the present invention, there is provided a method of recovering tin, the method comprising: (a) placing a base material with a tin-containing layer as an anode plate and a tin stripping solution as an electrolyte into tin stripping equipment comprising a cathode plate; (b) electrifying the anode plate and the cathode plate so as to remove the tin-containing layer from the substrate and simultaneously electroplate tin on the cathode plate, thereby recovering the tin, wherein the tin stripping solution comprises 50g/L-340g/L of electrolyte, 5g/L-200g/L of tin salt, 1g/L-40g/L of antioxidant and 1g/L-50g/L of stabilizer and dispersant, wherein the electrolyte comprises at least one of sulfuric acid and methanesulfonic acid.

In an exemplary embodiment of the present invention, it may be at a temperature of 25 deg.C-35 deg.C and 0.3A/dm³-4.5A/dm³Performing step (b) at the current density of (a).

In exemplary embodiments of the present invention, the tin-containing layer may be a tin layer, a tin-lead alloy layer, or a tin-copper alloy layer.

In an exemplary embodiment of the present invention, the cathode plate may be a titanium plate.

In an exemplary embodiment of the invention, the anode plate may be energized by a conductive brush of the tin stripping apparatus.

In an exemplary embodiment of the present invention, the conductive brush includes: a brush handle electrically connected to an external power source; brush filaments fixed and electrically connected to the brush holder; a support member overlapping the brush filaments and fixed to the brush holder together with the brush filaments to support the brush filaments; and a fixing part including a cover plate covering the brush wire and a portion of the support part and coupled to the brush holder to fix the brush wire and the support part between the brush holder and the fixing part.

According to the tin stripping solution and the method for recovering tin, at least one of the following effects can be obtained:

the tin stripping liquid is not only suitable for removing a tin layer, but also suitable for removing a tin-lead alloy layer and a tin-copper alloy layer, does not damage a substrate, and does not influence the glossiness of the substrate;

the tin stripping liquid has the advantages of large tin stripping capacity, durable tin stripping and the like;

the tin stripping liquid does not contain nitric acid or contains a very small amount of nitric acid, so that the reaction is relatively smooth, a large amount of heat cannot be generated, and basically no gas is discharged, so that the pollution to the environment is reduced;

according to the tin stripping liquid disclosed by the invention, in the tin stripping process, the tin stripping rate can be ensured under the condition that nitric acid is not contained or the nitric acid contains a very small amount by using the conductive brush;

according to the tin stripping liquid disclosed by the invention, tin can be recovered in the tin stripping process, so that the operation cost is reduced, and the energy consumption is reduced;

the tin stripping liquid is relatively simple in system, so that the tin stripping liquid is relatively stable, the service cycle is long, and the treatment capacity of waste liquid is reduced.

Drawings

These and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a perspective view of a tin stripping apparatus according to an exemplary embodiment of the inventive concept;

fig. 2 is a sectional view of a tin stripping apparatus taken along line I-I' of fig. 1 according to an exemplary embodiment of the inventive concept;

fig. 3 is a sectional view of a tin stripping apparatus taken along line II-II' of fig. 1 according to an exemplary embodiment of the inventive concept;

FIG. 4 is a cross-sectional view of a conductive brush according to an exemplary embodiment of the present invention; and

fig. 5 is a schematic view of a handle and cover plate of a conductive brush according to an exemplary embodiment of the present invention.

Detailed Description

The principle of the present invention will be described in further detail below with reference to exemplary embodiments to make the technical solution of the present invention clearer.

The tin stripping solution comprises 50g/L-340g/L of electrolyte, 5g/L-200g/L of tin salt, 1g/L-40g/L of antioxidant, and 1g/L-50g/L of stabilizer and dispersant. In a preferred embodiment, the tin stripping solution comprises 60g/L-340g/L of electrolyte, 40g/L-180g/L of tin salt, 1g/L-40g/L of antioxidant and 1g/L-30g/L of stabilizer and dispersant. In a more preferred embodiment, the tin stripping solution according to the invention comprises 60g/L to 280g/L of electrolyte, 50g/L to 150g/L of tin salt, 10g/L to 40g/L of antioxidant and 20g/L to 30g/L of stabilizer and dispersant in total, based on the total volume of the tin stripping solution. In the present invention, the unit "g/L" means the mass of the components contained in 1L of the tin stripping liquid.

The tin stripping solution according to the present invention contains the above-mentioned electrolyte as an active ingredient and solute, a tin salt, an antioxidant, and a stabilizer and dispersant, and water as a solvent. That is, the tin stripping solution according to the present invention is an aqueous tin stripping solution.

The electrolyte can play a role of dissolving a tin-containing layer (for example, a tin layer, a tin-lead alloy layer or a tin-copper alloy layer) and also plays a role of improving the conductivity and the dispersing ability of the solution and preventing stannous ions from being hydrolyzed.

According to an embodiment of the present invention, the electrolyte includes at least one of sulfuric acid and methanesulfonic acid, that is, may include only sulfuric acid, only methanesulfonic acid, or both sulfuric acid and methanesulfonic acid. In the exemplary embodiment of the invention, the content of the electrolyte in the tin stripping solution is 50g/L-340g/L, for example, 70g/L-320g/L, 100g/L-300g/L, 120g/L-270g/L, 150g/L-250g/L or 180g/L-220g/L, or any range defined by the above-mentioned values, for example, 70g/L-120g/L, 100g/L-270g/L, 120g/L-220g/L or 150g/L-180 g/L.

In an exemplary embodiment of the invention, the electrolyte comprises sulfuric acid and methanesulfonic acid, and the sulfuric acid may be present in an amount of 20g/L to 120g/L, for example, in an amount of 40g/L to 100g/L, 50g/L to 90g/L, or 60g/L to 80g/L, or any range defined by the values given above, for example, 40g/L to 90g/L, 50g/L to 80g/L, based on the total volume of the tin stripping solution; the amount of methanesulfonic acid can be from 30g/L to 220g/L, for example, from 50g/L to 200g/L, from 80g/L to 170g/L, or from 100g/L to 150g/L, or any range defined by the values given above, for example, from 50g/L to 150g/L, or from 80g/L to 100 g/L.

In the present invention, the methanesulfonic acid also has the effect of maintaining the acidity of the tin stripping solution and strengthening the tin stripping, and forms a complex with the divalent tin ion to stabilize the tin stripping solution. In the process of stripping tin, the tin is mainly Sn²⁺Is present in solution. Due to Sn²⁺Is easily oxidized to Sn by oxygen in the air⁴⁺And Sn⁴⁺Which is susceptible to hydrolysis to produce a beta-stannic acid precipitate that affects the removal of tin-containing layers (e.g., tin layers and copper-tin alloy layers). Therefore, in the present invention, the generation of the precipitate can be effectively suppressed by adding methanesulfonic acid.

The tin salt can be an auxiliary agent in the tin stripping solution, and can improve the conductivity of the solution, prevent the generation of side reaction at the cathode, improve the current efficiency and accelerate the reaction rate.

According to an embodiment of the present invention, the tin salt includes at least one of tin methanesulfonate and stannous sulfate, may include only tin methanesulfonate, may include only stannous sulfate, or may include both tin methanesulfonate and stannous sulfate. In exemplary embodiments of the invention, the tin salt is present in the tin stripping solution in an amount of from 5g/L to 200g/L, such as from 10g/L to 200g/L, from 30g/L to 190g/L, from 40g/L to 180g/L, from 60g/L to 160g/L, from 80g/L to 140g/L, or from 100g/L to 120g/L, or any range defined by any of the values set forth above, such as from 40g/L to 80g/L, from 60g/L to 120g/L, from 60g/L to 140g/L, or from 80g/L to 180 g/L.

In exemplary embodiments of the invention, the tin salt comprises tin methanesulfonate and stannous sulfate, and the tin methanesulfonate may be present in an amount of from 2g/L to 120g/L, for example, from 30g/L to 120g/L, from 40g/L to 110g/L, from 50g/L to 100g/L, from 60g/L to 90g/L, or from 70g/L to 80g/L, based on the total volume of the tin stripping solution, or any range defined by the values given above, for example, from 30g/L to 50g/L, from 40g/L to 90g/L, or from 60g/L to 120 g/L; the stannous sulfate may be present in an amount of from 3g/L to 80g/L, such as from 10g/L to 80g/L, from 20g/L to 70g/L, from 30g/L to 60g/L, or from 40g/L to 50g/L, or any range defined by the values set forth above, such as from 10g/L to 50g/L, from 20g/L to 40g/L, or from 30g/L to 80 g/L.

The antioxidant functions to prevent oxidation of the divalent tin to tetravalent tin.

If the content of the antioxidant is less than 1g/L based on the total volume of the tin stripping solution, oxidation of tin (II) to tin (IV) cannot be effectively prevented; based on the total volume of the tin stripping solution, the content of the antioxidant is higher than 40g/L, which causes unnecessary waste and increases the cost of raw materials. In exemplary embodiments of the invention, the antioxidant may be present in an amount ranging from 1g/L to 40g/L, 5g/L to 40g/L, 10g/L to 35g/L, 15g/L to 30g/L, or 20g/L to 25g/L, or any range defined by the values set forth above, such as, for example, 1g/L to 10g/L, 5g/L to 25g/L, or 10g/L to 40 g/L.

The antioxidant in the tin stripping solution according to the present invention may include at least one of a phenolic compound and a carboxylic acid compound, that is, may include only a phenolic compound, only a carboxylic acid compound, or both a phenolic compound and a carboxylic acid compound.

The carboxylic acid compound as the antioxidant can inhibit the hydrolysis of tetravalent tin by controlling the content of free acid in the tin stripping solution. In exemplary embodiments of the present invention, the carboxylic acid-based compound may include at least one of tartaric acid, citric acid, and salicylic acid, however, the present invention is not limited thereto.

Phenolic compounds as antioxidants protect the stannous tin from oxidation to the tetravalent tin by preferential oxidation by air. In an exemplary embodiment of the present invention, the phenolic compound may include at least one of resorcinol, hydroquinone, and catechol, however, the present invention is not limited thereto.

In an exemplary embodiment of the invention, the antioxidant comprises phenolic compounds and carboxylic acids, and the carboxylic acids may be present in an amount of 0.5g/L to 30g/L, for example, in an amount of 1g/L to 30g/L, 5g/L to 25g/L, 10g/L to 20g/L, or 15g/L to 25g/L, or any range defined by the values given above, for example, 1g/L to 10g/L, 5g/L to 15g/L, or 15g/L to 30g/L, based on the total volume of the solder stripper; the phenolic compound may be present in an amount of from 0.5g/L to 10g/L, for example in an amount of from 1g/L to 10g/L, from 2g/L to 9g/L, from 3g/L to 8g/L, from 4g/L to 7g/L or from 5g/L to 6g/L, based on the total volume of the solder stripper, or in any range defined by the values given above, for example in an amount of from 1g/L to 3g/L, from 3g/L to 8g/L, from 5g/L to 10 g/L.

The stabilizer and the dispersant are used as tin plating additives in the tin stripping solution, so that the stripped tin has better adhesion and flatness when being separated out from a cathode plate. According to an exemplary embodiment of the present invention, the stabilizer may include at least one of hydrazine hydrate, phenolsulfonic acid and cresolsulfonic acid, and the dispersant may include at least one of polyoxypropylene ether, polyethylene glycol and gelatin.

The dispersant can improve the cathode polarization, make the plating fine and improve the dispersion capability of the solution. In exemplary embodiments of the invention, the dispersant may be present in an amount of 0.5g/L to 20g/L, such as in the range of 1g/L to 20g/L, 3g/L to 18g/L, 5g/L to 16g/L, 7g/L to 14g/L, or 9g/L to 12g/L, or any range defined by the values given above, such as in the range of 1g/L to 5g/L, 5g/L to 14g/L, 14g/L to 20g/L, based on the total volume of the solder stripper.

The stabilizer can relieve the oxidation of divalent tin, stabilize the tin stripping liquid, improve the cathode polarization and ensure the uniform and fine plating layer. In an exemplary embodiment of the invention, the stabilizer may be present in an amount of 0.5g/L to 30g/L, for example, in an amount of 1g/L to 30g/L, 3g/L to 28g/L, 5g/L to 25g/L, 7g/L to 23g/L, 10g/L to 20g/L, 12g/L to 18g/L, or 14g/L to 16g/L, or any range defined by the above-mentioned values, for example, 1g/L to 5g/L, 5g/L to 18g/L, or 18g/L to 30g/L, based on the total volume of the solder stripper.

In exemplary embodiments where the tin plating additive includes both a stabilizer and a dispersant, the stabilizer and dispersant may act synergistically to promote better adhesion and flatness of the tin as it is deposited on the cathode plate.

In another exemplary embodiment of the present invention, the solder stripping solution may further include a sulfate. The sulfate has the main functions of enhancing the conductivity of the solution, accelerating the tin stripping rate and improving the current efficiency. In addition, the sulfate salt is used in combination with sulfuric acid and/or methanesulfonic acid to provide acidity to the solution.

Based on the total volume of the tin stripping liquid, if the content of sulfate is less than 20g/L, the conductive effect is poor; a sulphate content of more than 30g/L, based on the total volume of the tin stripping solution, reduces the solubility of tin. In exemplary embodiments of the invention, the sulfate salt may be present in an amount ranging from 20g/L to 30g/L, 21g/L to 29g/L, 22g/L to 28g/L, 23g/L to 27g/L, or 24g/L to 26g/L, or any range defined by the values set forth above, such as 21g/L to 27g/L, 22g/L to 28g/L, or 24g/L to 29 g/L.

The sulfate in the tin stripping liquid according to the present invention may include at least one of sodium sulfate and potassium sulfate, may include only sodium sulfate, may include only potassium sulfate, or may include both sodium sulfate and potassium sulfate.

In addition, the tin stripping solution can also comprise nitric acid. The nitric acid plays a role in assisting tin stripping, and if a large amount of nitric acid is added, the effect of tin plating is influenced, so that tin plating cannot be carried out, tin stripping and tin plating cannot be carried out simultaneously, and the using amount of the nitric acid must be strictly controlled. In an exemplary embodiment of the present invention, the content of the nitric acid may be 2 wt% to 3 wt% based on the total weight of the tin stripping solution. In the present invention, "nitric acid" means HNO as a solute₃. However, the present invention can use a nitric acid solution with a mass fraction of 60 wt% to 70 wt% to prepare the tin stripping solution, for example, the required amount of nitric acid in the tin stripping solution can be converted into an amount of nitric acid solution with a mass fraction of 60 wt% to 70 wt%, so as to determine the required amount of nitric acid solution with a mass fraction of 60 wt% to 70 wt% in the tin stripping solution.

Hereinafter, a method of removing a tin-containing layer on a substrate while recovering tin using the tin stripping liquid as described above will be described in detail.

Here, the substrate may refer to a substrate on which a tin-containing layer is electroplated on a base in order to manufacture a PCB, however, the present invention is not limited thereto. The tin-containing layer may be a tin layer, a tin-lead alloy layer or a tin-copper alloy layer.

In the present invention, the tin-containing layer on the substrate can be removed using an electrolytic method, while tin can be recovered while removing the tin-containing layer on the substrate using the electrolytic method.

Specifically, a substrate with a tin-containing layer as an anode plate and a tin stripping solution as an electrolyte are placed in a tin stripping device comprising a cathode plate; the anode plate and the cathode plate are energized so that the tin-containing layer is removed from the substrate while tin is electroplated on the cathode plate, thereby removing the tin-containing layer on the substrate and obtaining tin.

The substrate and the stripping solution as described above as electrolyte are first placed in a stripping apparatus, which may then be operated at a temperature of 25 ℃ to 35 ℃ and 0.3A/dm³-4.5A/dm³(e.g., 3.5A/dm)³-4.5A/dm³) The anode plate and the cathode plate are energized at a current density such that tin on the substrate is removed while tin is electroplated on the cathode plate.

The tin stripping apparatus 1000 will be described in detail below with reference to fig. 1 to 5.

Referring to fig. 1, a tin stripping apparatus 1000 according to an exemplary embodiment of the inventive concept may include a tin stripping bath assembly 1100 and a solution bath 1200.

As shown in fig. 1, the tin stripping bath assembly 1100 may at least partially overlap the solution bath 1200 in the Z-direction and may be disposed above the solution bath 1200. Tin stripping assembly 1100 may include

inlet ports

1171 and 1172 disposed at a side wall thereof. The tin stripping cell assembly 1100 may be an assembly that includes an electrolytic cell (or tin stripping cell) for performing a tin stripping (or tin recovery) process. During the tin stripping process, the tin stripping solution is injected into the tin stripping assembly 1100 through the

liquid inlets

1171 and 1172, the base material to be tin stripped is provided into the tin stripping assembly 1100, and then the tin plating layer and the copper-tin alloy layer on the base material are stripped by the electrochemical method by using the tin stripping solution of the invention. The specific structure of the tin stripping assembly 1100 will be described in detail later with reference to fig. 2 and 3.

As shown in fig. 1, the solution tank 1200 may be disposed at a lower portion of the tin stripping tank assembly 1100, and the solution tank 1200 may include a liquid inlet 1221 and a liquid outlet 1222 disposed at side walls thereof. The solution tank 1200 may be used to contain a tin stripping solution for stripping tin-plated and tin-copper alloy layers on a substrate.

In an embodiment according to the present invention, the tin stripping bath assembly 1100 and the solution bath 1200 may be disposed in fluid communication with each other. Specifically, the tin stripping bath assembly 1100 and the solution bath 1200 may be separate assemblies, respectively, or may be integrally formed with each other, and the tin stripping bath assembly 1100 and the solution bath 1200 may be in fluid communication with each other through a preset fluid passage. For example, the fluid pathway may be a flow-through channel disposed at the interface between the tin stripping bath assembly 1100 and the solution bath 1200, or may be a fluid delivery line for connecting the tin stripping bath assembly 1100 and the solution bath 1200.

According to an exemplary embodiment of the present invention, during the tin stripping process, the tin stripping solution is first delivered into the solution tank 1200 through the liquid inlet 1221 provided on the side wall of the solution tank 1200, and then delivered to the interior of the tin stripping tank assembly 1100 through the

liquid inlets

1171 and 1172 provided on the side wall of the tin stripping tank assembly 1100 by the circulation pump 1300. Next, the tin stripping solution after the predetermined tin stripping time in the tin stripping bath assembly 1100 can be transferred to the solution bath 1200 located below the tin stripping bath assembly 1100. Next, the tin stripping solution transferred into the solution tank 1200 may be transferred again into the tin stripping tank assembly 1100 by the circulation pump 1300 disposed on the solution tank 1200 and separated from the tin stripping tank assembly 1100, so that the tin stripping solution is circulated for a predetermined time. Under the condition, the tin stripping liquid can be fully used to reduce the consumption of the tin stripping liquid and simultaneously realize the purpose of reducing the cost. Then, the tin stripping liquid circulated in the solution tank 1200 for a predetermined time can be discharged through the liquid outlet 1222 provided on the side wall thereof for subsequent processing.

As shown in fig. 1, the tin stripping apparatus 1000 according to an exemplary embodiment of the inventive concept may further include a filter 1400. A filter 1400 can be disposed on the solution tank 1200 and separate from the tin stripping tank assembly 1100. The tin stripping solution can be delivered to the tin stripping bath 1110 after passing through the filter 1400. The filter 1400 can be used to filter impurities in the tin stripping solution (e.g., brush filaments of a conductive brush (see fig. 2 and 3), etc.) to prevent the impurities from entering the tin stripping solution along with the tin stripping solution into the tin stripping tank assembly 1100 and causing damage or contamination to the substrate.

Although the tin stripping apparatus 1000 according to the embodiment of the present invention has been described in detail by referring to fig. 1, the embodiment according to the present invention is not limited thereto. For example, the tin stripping apparatus 1000 may not include the solution tank 1200. In this case, the tin stripping liquid can be transported to the interior of the tin stripping assembly 1100 through a liquid inlet arranged on the tin stripping assembly 1100, and after a predetermined tin stripping time, the tin stripping liquid can be discharged from the tin stripping assembly 1100 through a liquid outlet arranged on the tin stripping assembly 1100.

Next, a specific structure of the tin stripping apparatus 1000 according to an embodiment of the present invention will be described in more detail with reference to fig. 2 and 3.

Fig. 2 is a sectional view of a tin stripping apparatus taken along line I-I' of fig. 1 according to an exemplary embodiment of the inventive concept. Fig. 3 is a sectional view of a tin stripping apparatus taken along line II-II' of fig. 1 according to an exemplary embodiment of the inventive concept.

Referring to fig. 2 and 3, the tin stripping assembly 1100 may include a tin stripping bath 1110, a housing 1120, a transfer portion 1130, and an electrode portion 1140.

The solder stripping bath 1110 may be disposed in the housing 1120. In other words, the housing 1120 may be disposed around the tin-stripping bath 1110 to isolate the tin-stripping bath 1110 from the outside. In addition, at least one of the sidewalls of the tin stripping bath 1110 may be spaced apart from the corresponding inner surface of the case 1120 by a predetermined distance. Tin-stripping channel 1110 may have a "U" shape (as shown in FIG. 3) when viewed in cross-section parallel to the plane defined by the Y-direction and Z-direction. Specifically, the tin-stripping bath 1110 may have a bottom plate and sidewalls protruding from edges of the bottom plate and extending in a direction perpendicular to the bottom plate, and may have an opening at the top. Wherein the bottom plate of the tin stripping bath 1110 may be integrally formed with the bottom of the tin stripping bath assembly 1100, or may be in contact with the bottom of the tin stripping bath assembly 1100. In addition, as shown in fig. 2, a pair of opposite side walls of the tin stripping tank 1110 and a corresponding pair of opposite side walls of the housing 1120 are respectively provided with openings as a feed inlet and a discharge outlet of the tin stripping tank assembly 1100, so that the base material to be subjected to tin stripping is supplied into the tin stripping tank assembly 1100 through the feed inlet and the base material subjected to tin stripping is conveyed to the outside of the tin stripping tank assembly 1100 through the discharge outlet. However, embodiments according to the present invention are not limited thereto, and for example, the tin stripping bath 1110 may further include a top plate, and the top plate includes a plurality of holes for overflowing the tin stripping liquid.

As shown in fig. 2, the conveyance 1130 may include a dilution roller (or referred to as a conveyance roller) 1131 and a manger roller 1132. The conveying portion 1130 may be used for conveying (e.g., in the X direction) the base material to be tin-stripped from the feed inlet of the tin stripping tank assembly 1100 to the discharge outlet of the tin stripping tank assembly 1100 through the tin stripping tank 1110. In other words, the conveying portion 1130 can provide a supporting force for the substrate and a driving force for the movement of the substrate during the tin stripping process.

Specifically, the evacuation rollers 1131 may be disposed at the feeding inlet and the discharging outlet of the tin stripping tank assembly 1100, so as to convey the substrate to be stripped from the feeding inlet into the tin stripping tank 1110, and send the stripped substrate out from the discharging outlet. The evacuation roller 1131 may also be disposed in the solder stripping trough 1110 to support and move the substrate toward the discharge opening. Each of the chop rollers 1131 may include a chop roller shaft (or referred to as a transfer line reel shaft, a line reel shaft) and at least one roller (or referred to as a roller plate, a line reel plate) that fits over the chop roller shaft. Both ends of the thin exhaust roller 1131 may be respectively connected to a pair of sidewalls facing each other of the tin-stripping bath 1110 where no opening is provided. In addition, the time consumed by the substrate passing through the tin stripping tank can be adjusted by controlling the rotation speed of the thin exhaust roller 1131, and further, the time for tin stripping treatment of the substrate can be adjusted. In this case, different substrate travel speeds may be provided by the payout roller 1131 depending on the tin layer thickness of the substrate, etc.

In addition, as shown in fig. 2, the rarefaction roller 1131 may be divided into a plurality of rarefaction roller groups, and each rarefaction roller group may include an upper rarefaction roller and a lower rarefaction roller disposed symmetrically to each other with respect to the substrate traveling direction. The number of the thin row roller groups can be set according to actual needs, and is not particularly limited. The plurality of banks of thinning rollers may be disposed to be spaced apart from each other by a predetermined distance in a traveling direction of the base material. In the tin stripping process, the upper surface and the lower surface of the base material are respectively contacted with the upper thin row roller and the lower thin row roller. In this way, the substrate can be supported and transferred more stably. In addition, the material forming the rarefaction roller 1131 is not particularly limited. In an embodiment according to the present invention, the roller shaft of the rarefaction roller 1131 may be preferably made of a metal material with a relatively large density, for example, to avoid being affected by the resistance caused by the solder stripping liquid.

In addition, the conveying part 1130 may further include a water blocking roller 1132. The water retaining roller 1132 may be respectively disposed at the discharge port and the feed port of the tin stripping tank assembly 1100 to prevent or reduce the outflow of the tin stripping liquid. Preferably, the water-blocking rollers 1132 may be respectively disposed at openings of the side walls of the tin stripping groove 1110 corresponding to the discharge port and the feed port, and may be disposed at the inner surfaces of the side walls of the tin stripping groove 1110. Similar to the rarefaction roller 1131, the water blocking roller 1132 may also be divided into a plurality of water blocking roller groups, and each of the water blocking roller groups may include an upper water blocking roller and a lower water blocking roller that are symmetrically disposed with respect to the substrate traveling direction. In this case, a water retaining roller set may be disposed at the inlet and outlet of the tin stripping groove assembly 1100. Except supporting the substrate and making the substrate advance towards the export, water blocking roller 1132 can also prevent or reduce the tin solution that moves back in the tin bath and reveal to guarantee to move back the stability of the liquid level in the tin bath and ensure moving back the steady progress of tin technology. In this case, when the tin stripping process is performed, the substrate is soaked in the tin stripping liquid, so that the contact between tin and air can be reduced in the tin stripping process, and the problem of tin oxidation is avoided. In addition, embodiments according to the inventive concept are not limited thereto, and for example, at least one water-retaining roller set may also be disposed in the tin stripping bath 1110, and in particular, between openings of the tin stripping bath 1110 corresponding to a feed inlet and a discharge outlet of the tin stripping apparatus (e.g., at an intermediate position of the tin stripping bath 1110). In this case, since the water blocking roller has a relatively large weight, the substrate is prevented from being adversely affected by buoyancy during traveling, and thus the substrate can be stably transferred.

In addition, although not shown in fig. 1 to 3, the transfer part 1130 may further include a driver providing a driving force for the rarefied exhaust roller 1131 and the water stop roller 1132.

Referring to fig. 2 and 3, the electrode part 1140 may include a cathode plate 1141 and a conductive brush 1142.

Specifically, the tin stripping bath 1110 may define a space where the tin stripping process is actually performed. As shown in fig. 2 and 3, a portion of the transfer portion 1130, a cathode plate 1141, and a conductive brush 1142 may be disposed in the tin stripping bath 1110. The tin stripping solution and the substrate may also be located within the tin stripping bath 1110 during the tin stripping process.

Cathode plate 1141 may be disposed at least one of the bottom and top of tin stripping bath 1110. Cathode plate 1141 may extend parallel to the direction of substrate travel (e.g., the X-direction), and the length and/or width of cathode plate 1141 is less than the length and/or width of tin stripping bath 1110. In other words, cathode plate 1141 may be spaced a predetermined distance from the inner surface of at least one sidewall of tin stripping bath 1110.

In an embodiment according to the present invention, because the substrate generally employs double-sided wiring, cathode plates 1141 may be disposed at the bottom and top of tin stripping bath 1110 and include upper cathode plates 1141a and lower cathode plates 1141 b. The upper cathode plate 1141a and the lower cathode plate 1141b may face each other and be disposed at the bottom and the top of the tin stripping bath 1110, respectively, parallel to the substrate traveling direction, and the transfer portion 1130 may be located between the upper cathode plate 1141a and the lower cathode plate 1141b facing each other. In other words, the transferring portion 1130 and the cathode plate 1141 may be disposed parallel to each other. However, an embodiment according to the present invention is not limited thereto, and for example, the cathode plate 1141 may include only the upper cathode plate 1141a disposed at the top of the tin stripping bath 1110.

Cathode plates 1141 may be fixed at the top and bottom of the tin stripping bath 1110 by cathode plate fixing rods 1143. Although it is illustrated in fig. 2 and 3 that the upper cathode plate 1141a and the lower cathode plate 1141b are fixed at the top and bottom of the tin stripping bath 1110 by three cathode plates 1141, respectively, embodiments according to the present invention are not limited thereto. For example, the upper cathode plate 1141a may be fixed at the top of the tin stripping bath 1110 by cathode plate fixing rods 1143, and the lower cathode plate 1141b may be directly connected to the bottom plate of the tin stripping bath 1110 by a cathode tap 1145 to be described below without using the cathode plate fixing rods 1143. For another example, when the tin stripping bath 1110 includes a top plate, both the upper cathode plate 1141a and the lower cathode plate 1141b can be directly fixed to the bottom plate and the top plate of the tin stripping bath 1110 by the cathode plug 1145.

Specifically, as shown in fig. 2 and 3, one end of the cathode plate fixing rod 1143 may be connected to one side wall of the tin stripping bath 1110, and the other end of the cathode plate fixing rod 1143 may be connected to the other side wall of the tin stripping bath 1110 facing the one side wall. The cathode plate 1141 may be connected to the cathode plate fixing rod 1143 by cathode taps 1145, for example, portions of the cathode plate fixing rod 1143 near both ends may be connected to the cathode plate 1141 by cathode taps 1145, respectively.

In addition, the cathode tap 1145 may be used to adjust a distance between the cathode plate and the anode plate (in the embodiment of the present invention, the substrate is used as an anode in the tin stripping process) in addition to the cathode plate 1141 and the cathode plate fixing rod 1143. In other words, cathode plate 1141 (e.g., upper cathode plate 1141a and/or lower cathode plate 1141b) may be moved toward and/or away from the anode plate (or transport portion 1130) by cathode peg 1145 to enable adjustment of the pole pitch, which in turn may control the rate of stripping. When the pole pitch is reduced, the tin stripping rate can be increased and the power consumption can be reduced, but too small a pole pitch can make tin stripping non-uniform and increase the risk of short circuit. When the pole pitch is increased, the tin stripping rate is slowed down and the power consumption is increased. In embodiments according to the invention, the pole pitch may be about 5cm to about 15 cm.

Cathode plate 1141 may be made of an electrically conductive metallic material or a non-metallic material. For example, cathode plate 1141 may be a metallic titanium plate, a metallic titanium mesh, a graphite plate, or the like. When cathode plate 1141 is in the shape of a plate made of a conductive material, cathode plate 1141 may include a plurality of holes so that the tin stripping liquid filling tin stripping bath 1110 can further overflow from the plurality of holes.

Referring again to fig. 2 and 3, a conductive brush 1142 may be disposed adjacent to the transmitting portion 1130 and between the upper cathode plate 1141a and the lower cathode plate 1141 b. However, when cathode plate 1141 includes only upper cathode plate 1141a, conductive brush 1142 may be located between upper cathode plate 1141a and the bottom plate of tin stripping bath 1110.

As shown in fig. 2 and 3, the conductive brushes 1142 may be arranged alternately with the rarefaction rollers 1131 in the direction of substrate travel. In other words, the conductive brushes 1142 may be respectively disposed between the rarefaction rollers 1131 (or rarefaction roller groups). The conductive brushes 1142 may be disposed spaced apart from each other at predetermined intervals in a substrate traveling direction (e.g., X direction), and may extend in a direction (e.g., Y direction) parallel to an extending direction of the switchback roller 1131 (or switchback roller set). In other words, both ends of the conductive brush 1142 may be respectively connected to a pair of side walls (as shown in fig. 3) facing each other of the tin stripping bath 1110 where no opening is provided.

During the de-tinning process, the conductive brush 1142 may be contacted with the substrate to apply a voltage to the substrate, thereby using the substrate as an anode to achieve electrochemical de-tinning.

Additionally, conductive brush 1142 may include a brush handle (e.g., 1142a-1 and 1142b-1 shown in FIG. 3) and brush filaments (e.g., 1142a-2 and 1142b-2 shown in FIG. 3). The brush holders and the brush filaments may be electrically connected to each other.

As shown in fig. 2 and 3, the conductive brushes 1142 may be divided into a plurality of conductive brush groups. Each conductive brush set may include an upper conductive brush 1142a and a lower conductive brush 1142b, and the upper conductive brush 1142a and the lower conductive brush 1142b may be in contact with the upper surface and the lower surface of the substrate, respectively. Each set of conductive brushes may be arranged alternately with each set of thinning rollers in the direction of travel of the substrate. The upper and lower

conductive brushes

1142a and 1142b in each conductive brush group may partially overlap each other, in other words, the upper and lower

conductive brushes

1142a and 1142b are staggered from each other by a predetermined distance (for example, the width of the non-overlapped portions of the upper and lower

conductive brushes

1142a and 1142b is about 3mm to 5mm) when viewed in a plan view. In this case, the running resistance of the base material can be reduced. Further, when viewed in a cross-sectional view, the upper conductive brush 1142a and the lower conductive brush 1142b may be partially overlapped, and specifically, the brush filaments 1142a-2 of the upper conductive brush 1142a and the brush filaments 1142b-2 of the lower conductive brush 1142b may be partially overlapped (for example, overlapped length is 5 mm). Therefore, the conductive brush can be ensured to be fully contacted with the substrate, and simultaneously, the conductive brush can be mechanically acted with the substrate in the tin stripping process to accelerate the tin stripping rate.

The conductive brush 1142 will be described in detail below with reference to fig. 4 and 5.

As shown in fig. 4, the conductive brush 1142 may include a brush shaft 1142-1, brush filaments 1142-2, a support member 1142-3, and a fixing member.

The handle 1142-1 may be connected to an external power source to receive a predetermined voltage from the external power source. The brush handle 1142-1 may apply the received voltage to the substrate through the brush filaments 1142-2. Thus, the brush handle 1142-1 may be made of a conductive material such as titanium, copper, aluminum, or alloys thereof. For example, in embodiments according to the invention, brush holder 1142-1 may be a titanium plate or a copper plate.

The filaments 1142-2 may be secured to the handle 1142-1 and electrically connected to the handle 1142-1. Specifically, the filaments 1142-2 may be directly attached to the handle 1142-1 at one end and may contact the substrate at the other end. Since the brush wires 1142-2 are in direct contact with the substrate, the brush wires 1142-2 may be made of a conductive and flexible material (such as carbon fiber wires, carbon fiber cloth, conductive cloth, titanium foil, etc.), thereby preventing the conductive brush 1142 from damaging the substrate.

The support member 1142-3 may overlap the filaments 1142-2 and be secured to the handle 1142-1 with the filaments 1142-2. Since the brush filaments 1142-2 have flexibility, the supporting member 1142-3 may serve to support the brush filaments 1142-2 to ensure that the brush filaments 1142-2 can be stably contacted with the substrate. In addition, the support member 1142-3 may be made of an insulating material (such as a silicone sheet, a PVC sheet, or a hot melt adhesive film). In this case, since the supporting member 1142-3 may function to shield the brush filaments 1142-2, the oxidation of the brush filaments 1142-2 may be prevented (or slowed) without the contact of the brush filaments 1142-2 with the substrate, and thus the service life and the use effect of the brush filaments 1142-2 may be improved.

The securing members may be used to secure the filaments 1142-2 and support members 1142-3 to the handle 1142-1 and include a cover plate 1142-4. A cover 1142-4 may cover the filaments 1142-2 and a portion of the support member 1142-3 and be coupled to the handle 1142-1 to secure the filaments 1142-2 and the support member 1142-3 between the handle 1142-1 and the cover 1142-4. In an embodiment according to the present invention, the cover plate 1142-4 may be made of a conductive metal material, for example, a titanium plate, a copper plate, a stainless steel plate, or an aluminum plate.

As shown in fig. 5, the brush handle 1142-1 may have protrusions at both ends in a length direction thereof. The protrusions may be respectively inserted into fixing grooves on the sidewalls of the tin-stripping bath 1110 facing each other, thereby fixing the conductive brush 1142 into the tin-stripping bath 1110.

The cover plate 1142-4 and the handle 1142-1 may include a plurality of holes corresponding to each other, respectively. In this case, the cover plate 1142-4 may be fixed to the brush holder 1142-1 via the plurality of holes corresponding to each other by screws and nuts (refer to 1142-5 in fig. 4). However, the embodiment according to the invention is not limited thereto, for example, the cover plate 1142-4 and the brush holder 1142-1 may be coupled to each other by a conductive paste. For example, the conductive paste may be a silver-based conductive paste, a copper-based conductive paste, or a graphite-based conductive paste.

When the cover plate 1142-4 and the brush holder 1142-1 may be coupled to each other by the screw and the nut through the plurality of holes corresponding to each other, a portion of the brush wire 1142-2 between the cover plate 1142-4 and the brush holder 1142-1 may be a carbon fiber cloth or a conductive cloth, and another portion of the brush wire 1142-2 extending from the portion beyond an edge of the brush holder may be a carbon fiber wire or a conductive wire extending therefrom. Thus, the brush filaments 1142-2 are prevented from loosening and falling off. However, when the cover plate 1142-4 and the brush holder 1142-1 may be combined with each other by a conductive paste, the arrangement of the brush filaments 1142-2 is not particularly limited. In addition, the length of the other portion of the filaments 1142-2 extending from the portion beyond the edge of the handle can be set as desired, too short a length will prevent the filaments from stably contacting the substrate, and too long a length will increase the resistance.

Further, during the tin stripping process, since the conductive brush 1142 is entirely immersed in the tin stripping liquid, in order to avoid corrosion of the metal conductor of the conductive brush by the tin stripping liquid, a sealing portion (not shown) may also be provided outside the conductive brush. The sealing portion may at least partially cover the brush holder 1142-1 and the cover plate 1142-4 of the conductive brush 1142 to isolate the brush holder 1142-1 and the cover plate 1142-4 from the solder stripping solution during the solder stripping process. However, embodiments according to the present invention are not limited thereto, and for example, when the brush holder 1142-1 and the cover plate 1142-4 are both formed of metallic titanium, the sealing portion may be omitted since titanium is not easily corroded by the solder stripping liquid.

Additionally, the conductive brush 1142 may further include an electrical connection 1142-6 electrically connecting the brush handle 1142-1 to an external power source. However, in another embodiment according to the present invention, the electrical connections 1142-6 may be omitted.

In the embodiment of the invention, the contact between tin and air is reduced in the tin stripping process by soaking the substrate into the tin stripping solution, so that the problem of tin oxidation is avoided. However, stripping tin by immersion reduces the stripping rate. Therefore, in the embodiment of the invention, the reaction rate can be further accelerated by an electrochemical method through the tin stripping device with the conductive brush, and the tin stripping rate can be further accelerated through the mechanical action of the conductive brush and the base material, so that the problem of the reduction of the reaction rate of soaking tin stripping is solved.

In addition, the tin stripping bath assembly 1100 may further include a liquid inlet pipe 1150 disposed at the bottom of the tin stripping bath 1110. The tin stripping liquid is injected into the tin stripping tank 1110 from

liquid inlets

1171 and 1172 on the side wall of the tin stripping tank 1110 through a liquid inlet pipe 1150 (as shown by the arrow in fig. 2). Then, the solder stripping solution injected into the solder stripping tank 1110 gradually fills the internal space of the solder stripping tank 1110, so that the electrode portion 1140 and the transmitting portion 1130 in the solder stripping tank 1110 are immersed in the solder stripping solution. As shown by arrows in fig. 2 and 3, after the predetermined time of tin stripping treatment, the tin stripping liquid overflows through an opening at the top of the tin stripping bath 1110 to a gap between the side wall of the tin stripping bath 1110 and the inner surface of the housing 1120, and then flows into the solution bath 1200 through the gap via a fluid passage between the tin stripping bath assembly 1100 and the solution bath 1200. In addition, the tin-stripping solution flowing into the solution tank 1200 may be re-injected into the tin-stripping tank 1110 by the circulation pump 1300, so that the tin-stripping solution is recycled to more fully utilize the tin-stripping solution. After a predetermined cycle time, the tin stripping solution can be drained from the solution tank 1200.

Further, referring to fig. 3, the solution tank 1200 may further have an inclined bottom surface. Specifically, the horizontal height of the portion of the bottom surface of the solution tank 1200 overlapping the tin stripping tank assembly 1100 is higher than the horizontal height of the portion of the bottom surface thereof overlapping the circulation pump 1300. In this way, the liquid level of the tin stripping liquid at the portion of the solution tank 1200 overlapping the circulation pump 1300 can be ensured, and thus the circulation of the tin stripping liquid can be stably performed.

In addition, the tin stripping apparatus according to the embodiment of the present invention may further include a power supply device (not shown), a support assembly 1500, a condensing device (not shown), a heating apparatus (not shown), and the like.

Specifically, the power supply device may be disposed outside the tin stripping apparatus, and may supply voltages of respective polarities to the cathode plate 1141 and the conductive brush 1142 during the tin stripping process, respectively. During the tin stripping process, the supply current can be regulated by the power supply device, so that the tin layers with different thicknesses can be stripped.

A condensing device (not shown) and a heating apparatus (not shown) may also be included in the solution tank 1200 to achieve temperature control of the tin stripping solution for improving tin stripping efficiency.

According to the embodiment of the invention, by adopting the conductive brush, the tin stripping rate can be further accelerated by the mechanical action of the conductive brush and the base material, and the problem of reduction of the reaction rate of soaking tin stripping is further solved. In addition, the tin stripping device adopting the conductive brush can realize at least one of the following effects: the stripping of tin layers with different thicknesses is easily achieved; reducing tin to air contact during tin stripping process, thereby preventing Sn²⁺Is oxidized into Sn by oxygen in the air⁴⁺(ii) a Provides a simple electrochemical tin stripping device; the pollution caused by tin stripping is avoided or reduced; the tin stripping liquid is easily recycled, the cost is saved, the energy consumption is reduced, and the tin recovery efficiency is also improved.

According to an exemplary embodiment of the present invention, a redox reaction occurs when electricity is applied, and the reaction mechanism is: anode (substrate with tin-containing layer) Sn-2e^-→Sn²⁺，

Cathode (titanium plate) Sn²⁺+2e^-→Sn。

In an exemplary embodiment of the present invention, the cathode plate may be a titanium plate; however, the present invention is not limited thereto.

The tin stripping solution according to the invention can be prepared simply by dissolving the components in water.

The tin stripping solution of the invention can contain no nitric acid or a very small amount of nitric acid, so the reaction is relatively smooth, a large amount of heat can not be generated, and basically no gas is discharged, thereby reducing the pollution to the environment. In addition, the conductive brush can also accelerate the tin stripping rate. In addition, the tin stripping liquid can recover tin in the tin stripping process, so that the operation cost is reduced, and the energy consumption is reduced. In addition, the tin stripping liquid is relatively simple in system, so that the tin stripping liquid is relatively stable, the service cycle is long, and the treatment capacity of waste liquid is reduced.

The solder stripping solution according to the present invention is described in more detail below with reference to examples.

Preparation example 1: preparation of tin stripping liquid

50g of sulfuric acid, 5g of stannous sulfate, 10g of tartaric acid, 3g of hydroquinone, 10g of phenolsulfonic acid and 10g of gelatin solution are dissolved in water to prepare 1L of tin stripping solution.

Preparation examples 2 to 16: preparation of tin stripping liquid

With the exception of the components and contents shown in Table 1, a tin stripping solution was prepared in accordance with the method of preparation example 1.

Comparative example 1: preparation of tin stripping liquid

A tin stripping solution was prepared by the method of preparation example 2, except that no dispersant was included.

Comparative example 2: preparation of tin stripping liquid

A tin stripping solution was prepared by the method of preparation example 4, except that no stabilizer was included.

Comparative example 3: preparation of tin stripping liquid

A tin stripping solution was prepared by following the method of preparation example 13, except that the amount of nitric acid was increased to 4.7 wt%.

TABLE 1

Evaluation examples

The tin-stripping solutions obtained in preparation examples 1 to 16 and comparative examples 1 to 3 were placed in the above tin-stripping apparatus at a temperature of about 30 ℃ and a current density of about 3.5A/dm³The anode and cathode are energized, and tin is stripped from the substrate and plated onto the cathode. The properties of the solder stripper were evaluated, and the results are shown in table 2 below.

TABLE 2

Referring to table 2, the tin recovery rate, the tin stripping effect and the tin plating effect of the cathode according to the preparation examples 1 to 16 of the present invention were all higher than those of the comparative examples 1 and 2.

Further, referring to table 2, the tin stripping solutions according to the present invention of preparation examples 2 and 4 were compared with comparative examples 1 and 2, respectively, and the dispersion agents and the stabilizers were contained, so that the tin plating quality was superior to that of comparative example 1. In addition, the tin plating effects of preparation examples 2, 9, 12, and 15 in which the dispersant was polyethylene glycol were better than those of preparation example 1 in which the dispersant was gelatin, but the effects were not as good as those of comparative example 1.

In addition, referring to table 2, when the nitric acid content of preparation example 13 according to the present invention is more than 3 wt% compared to comparative example 3, no tin is precipitated and it is impossible to simultaneously remove tin and recover tin; in the invention, when the content of the nitric acid is controlled to be less than 3 wt%, the tin stripping rate can be improved, and the tin can be recovered.

In addition, when the production examples 11 to 16 of the present invention were compared with the production examples 5, 9, 10, 3, 2 and 4 of the present invention, respectively, the tin stripping rate was improved by adding the sulfate and the nitric acid.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. The embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.

Claims

1. The tin stripping solution for stripping tin by an electrolytic method is characterized by comprising 50g/L-340g/L of electrolyte, 5g/L-200g/L of tin salt, 1g/L-40g/L of antioxidant, and 1g/L-50g/L of stabilizer and dispersant,

wherein the electrolyte is both sulfuric acid and methanesulfonic acid, the content of the sulfuric acid is 20g/L-120g/L, the content of the methanesulfonic acid is 30g/L-220g/L based on the total volume of the tin stripping solution for stripping tin by an electrolytic method,

wherein the stabilizer comprises at least one of hydrazine hydrate, phenol sulfonic acid and cresol sulfonic acid, and the dispersant comprises at least one of polyoxypropylene ether, polyethylene glycol and gelatin.

2. The electrolytic tin-stripping solution according to claim 1, wherein the tin salt comprises at least one of tin methanesulfonate and stannous sulfate.

3. The tin stripping solution for stripping tin by electrolytic process according to claim 2, characterized in that the tin salt comprises tin methane sulfonate and stannous sulfate,

based on the total volume of the tin stripping liquid for stripping tin by an electrolytic method, the content of tin methanesulfonate is 2g/L-120g/L, and the content of stannous sulfate is 3g/L-80 g/L.

4. The tin stripping solution for stripping tin by electrolysis according to claim 1, wherein the antioxidant comprises at least one of carboxylic acid compounds and phenolic compounds.

5. The tin stripping solution for electrolytic tin stripping according to claim 4, wherein the carboxylic acid compound comprises at least one of tartaric acid, citric acid and salicylic acid, and the phenolic compound comprises at least one of resorcinol, hydroquinone and catechol.

6. The tin stripping solution for electrolytic tin stripping according to claim 1, wherein the stabilizer is contained in an amount of 0.5g/L to 30g/L and the dispersant is contained in an amount of 0.5g/L to 20g/L, based on the total volume of the tin stripping solution for electrolytic tin stripping.

7. The tin stripping solution for electrolytic tin stripping according to claim 1, further comprising a sulfate in an amount of 20g/L to 30g/L based on the total volume of the tin stripping solution for electrolytic tin stripping.

8. The tin stripping solution for stripping tin by electrolysis according to claim 7, wherein the sulfate includes at least one of sodium sulfate and potassium sulfate.

9. A method for recovering tin, the method comprising the steps of:

(a) placing a base material with a tin-containing layer as an anode plate and a tin stripping solution for stripping tin by an electrolytic method as an electrolyte into tin stripping equipment comprising a cathode plate;

(b) energizing the anode plate and the cathode plate such that the tin-containing layer is removed from the substrate while tin is electroplated on the cathode plate, thereby recovering the tin,

the tin stripping liquid for electrolytic tin stripping comprises 50g/L-340g/L of electrolyte, 5g/L-200g/L of tin salt, 1g/L-40g/L of antioxidant, and a stabilizer and a dispersant with the total content of 1g/L-50g/L, wherein the electrolyte is both sulfuric acid and methanesulfonic acid, the content of sulfuric acid is 20g/L-120g/L and the content of methanesulfonic acid is 30g/L-220g/L based on the total volume of the tin stripping liquid for electrolytic tin stripping, the stabilizer comprises at least one of hydrazine hydrate, phenolsulfonic acid and cresolsulfonic acid, and the dispersant comprises at least one of polyoxypropylene ether, polyethylene glycol and gelatin.

10. The method of claim 9, wherein the tin-containing layer is a tin layer, a tin-lead alloy layer, or a tin-copper alloy layer.

11. A method according to claim 9, characterized in that the cathode plate is a titanium plate.

12. The method of claim 9, wherein the anode plate is energized by a conductive brush of a de-tinning apparatus.

13. The method of claim 12, wherein the conductive brush comprises: a brush handle electrically connected to an external power source; brush filaments fixed and electrically connected to the brush holder; a support member overlapping the brush filaments and fixed to the brush holder together with the brush filaments to support the brush filaments; and a fixing part including a cover plate covering the brush wire and a portion of the support part and coupled to the brush holder to fix the brush wire and the support part between the brush holder and the fixing part.