Automobile circuit board and tinning treatment method thereof

Abstract

The present application provides an automotive circuit board and a tinning treatment method thereof. The above-mentioned tinning treatment method for automotive circuit boards includes the following steps: photocuring the ink layer on the circuit board to obtain a photocured circuit board; degreasing the photocured circuit board to obtain a degreasing circuit board; microetching the degreasing circuit board to obtain a microetched circuit board; prepregging the microetched circuit board to obtain a prepreg circuit board; sequentially adjusting the temperature and complex concentration of the tinning solution to make the temperature of the tinning solution reach 66°C to 70°C and the complex concentration reach 140g / L to 160g / L; placing the prepreg circuit board into the adjusted tinning solution for chemical tinning. The above-mentioned tinning treatment method for automotive circuit boards has the advantages of being able to reduce the attack of the solution on the solder resist ink and reduce the depth of side etching while ensuring the deposition rate.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit boards, in particular to an automobile circuit board and a tinning treatment method thereof. Background Art

[0002] At present, with the improvement of environmental governance, new energy vehicles have been vigorously promoted by the government as pollution-free means of transportation. Modern cars have developed from being completely mechanized in the past to a combination of mechanics and electronics, and from being a simple means of transportation to a multifunctional platform integrating transportation, entertainment, office, etc. The domestic demand for automotive printed circuit boards in new energy vehicle power systems and ADAS systems has increased significantly.

[0003] In the circuit board manufacturing process, since copper often exists in the form of oxides in the air and cannot be kept as original copper for a long time, the circuit board needs to be surface treated to ensure good solderability or electrical performance of the circuit board. Circuit board surface treatment refers to the process of forming a surface layer on components and electrical connection points that has mechanical, physical and chemical properties different from those of the substrate. Currently, common surface treatment processes include hot air leveling, organic coating, chemical nickel plating / immersion gold, immersion silver, immersion tin, etc. Immersion tin, also known as chemical tin, changes the chemical potential of copper to cause a chemical replacement reaction of stannous ions in the solution. The reduced tin metal is deposited on the surface of the copper substrate to form a tin coating, and the metal complex adsorbed on the immersion tin coating catalyzes the reduction of tin ions to metallic tin, so that the tin ions continue to be reduced to tin.

[0004] However, in the actual production process, due to the chemical tin process's own chemical characteristics, high acid concentration, thiourea concentration, high working temperature, immersion time and other superimposed factors, the solder mask ink is easily attacked by the chemical solution and peeled off, resulting in short circuits and other problems after mounting. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an automotive circuit board and a tinning treatment method thereof which can reduce the attack of the solution on the solder resist ink and reduce the depth of the side etching while ensuring the deposition rate.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A method for treating an automobile circuit board with tinning comprises the following steps:

[0008] Performing a photocuring operation on the ink layer on the circuit board to obtain a photocured circuit board;

[0009] Degreasing the light-cured circuit board to obtain a degreasing circuit board;

[0010] Performing micro-etching operation on the degreased circuit board to obtain a micro-etched circuit board;

[0011] Performing a prepreg operation on the micro-etched circuit board to obtain a prepreg circuit board;

[0012] The tin solution is subjected to temperature adjustment and complex concentration adjustment in sequence, so that the temperature of the tin solution reaches 66° C. to 70° C. and the concentration of the complex reaches 140 g / L to 160 g / L;

[0013] The pre-preg circuit board is placed in the adjusted tin solution to perform chemical tinning operation.

[0014] In one embodiment, an acidic degreasing agent is used in the degreasing operation.

[0015] In one embodiment, the acidic degreasing agent includes an inorganic acid, a corrosion inhibitor, a wetting agent and a stabilizer.

[0016] In one embodiment, the temperature during the degreasing operation is 30°C to 40°C.

[0017] In one embodiment, the oil removal operation lasts for 5 to 7 minutes.

[0018] In one embodiment, the micro-etching agent in the micro-etching operation is a sodium persulfate solution.

[0019] In one embodiment, the concentration of the sodium persulfate solution is 55 g / L to 65 g / L.

[0020] In one embodiment, the micro-etching operation lasts for 18 seconds to 22 seconds.

[0021] In one embodiment, the temperature during the prepreg operation is 40°C to 50°C.

[0022] The present application also provides an automotive circuit board, which is prepared by using the tinning treatment method for the automotive circuit board described in any of the above embodiments.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] 1. In the tinning treatment method for automobile circuit boards of the present invention, the ink layer on the circuit board is first photocured to achieve a hardening effect on the ink layer of the circuit board, and the hardened ink layer can effectively reduce the attack of the tinning solution; then the circuit board after photocuring is degreased, which can not only remove the residual film and glue of the ink, but also remove the grease and oxides on the copper surface, so that the copper surface is clean and the wettability is increased; further, by micro-etching the circuit board after degreasing, it can further ensure that the oxides on the copper surface are completely removed, and at the same time, the copper surface of the circuit is cleaned and roughened, so as to ensure the bonding force between the pattern electroplated copper and the primary copper, and facilitate the subsequent electroplating operation of the circuit board; and the pre-impregnation operation can reduce the introduction of harmful and polluting substances into the tinning tank, so as to extend the life of the solution in the tinning tank.

[0025] 2. In the tinning treatment method for automobile circuit boards of the present invention, the temperature adjustment operation and the complex concentration adjustment operation are performed on the tinning solution in sequence, so that the temperature of the tinning solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L. While ensuring the deposition rate, by adjusting the complex concentration and the operating temperature in the tinning tank solution, under the conditions that the temperature of the tinning solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L, the side etching depth of the circuit board by the tinning solution can be effectively reduced, and the attack of the tinning solution on the solder resist ink can be reduced, thereby effectively alleviating the problem of easy detachment of the solder resist layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 The present invention is a flow chart of a method for treating an automotive circuit board with tin in one embodiment.

[0028] Figure 2 To adopt Figure 1 A schematic diagram of the ink side etching depth of a circuit board obtained by the tinning treatment method for an automobile circuit board.

[0029] Figure 3 Not adopted Figure 1 A schematic diagram of the ink side etching depth of a circuit board obtained by the tinning treatment method for an automobile circuit board. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0031] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0033] The present application provides a tinning treatment method for automobile circuit boards. The above-mentioned tinning treatment method for automobile circuit boards includes the following steps: performing a photocuring operation on the ink layer on the circuit board to obtain a photocured circuit board; performing a degreasing operation on the photocured circuit board to obtain a degreasing circuit board; performing a microetching operation on the degreasing circuit board to obtain a microetched circuit board; performing a prepreg operation on the microetched circuit board to obtain a prepreg circuit board; performing a temperature adjustment operation and a complex concentration adjustment operation on the tinning solution in sequence, so that the temperature of the tinning solution reaches 66°C to 70°C, and the complex concentration reaches 140g / L to 160g / L; placing the prepreg circuit board into the adjusted tinning solution for chemical tinning.

[0034] In the above-mentioned tinning treatment method for automobile circuit boards, the ink layer on the circuit board is first photocured to harden the ink layer of the circuit board, and the hardened ink layer can effectively reduce the attack of the tinning solution; then the circuit board after photocuring is degreased, which can not only remove the residual film and glue of the ink, but also remove the grease and oxides on the copper surface, so that the copper surface is clean and the wettability is increased; further, by micro-etching the circuit board after degreasing, it can be further ensured that the oxides on the copper surface are completely removed, and at the same time, the copper surface of the circuit is cleaned and roughened, so as to ensure the bonding strength between the pattern electroplated copper and the primary copper, so as to facilitate the subsequent electroplating operation of the circuit board; and the pre-impregnation operation can reduce the introduction of harmful and polluting substances into the tinning tank, so as to extend the life of the solution in the tinning tank. Furthermore, the temperature and complex concentration of the tin-plating solution are adjusted in sequence to make the temperature of the tin-plating solution reach 66°C to 70°C and the complex concentration reach 140g / L to 160g / L. While ensuring the deposition rate, by adjusting the complex concentration and the operating temperature in the tin-plating tank solution, under the conditions that the temperature of the tin-plating solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L, the side etching depth of the tin-plating solution on the circuit board can be effectively reduced, and the attack of the tin-plating solution on the solder resist ink can be reduced, thereby effectively alleviating the problem of easy detachment of the solder resist layer.

[0035] In order to better understand the tinning treatment method of the automobile circuit board of the present invention, the tinning treatment method of the automobile circuit board of the present invention is further explained below. Figure 1 As shown, a method for treating an automotive circuit board with tinning in one embodiment includes some or all of the following steps:

[0036] S100, performing a photocuring operation on the ink layer on the circuit board to obtain a photocured circuit board.

[0037] It is understandable that due to the chemical tin process's own characteristics of the solution, high acid concentration, thiourea concentration, high working temperature, soaking time and other superimposed factors, the solder resist ink is susceptible to the attack of the solution to form peeling, resulting in short circuits after mounting, and other problems, especially the ink layer that has just been coated is more susceptible to the attack of the tin solution. In order to reduce the attack of the tin solution on the solder resist ink layer, in this embodiment, the ink is cured by the ultraviolet light of the UV machine. Under ultraviolet irradiation, ultraviolet light of different wavelengths and energies is used to form a film and dry the ink, so that the circuit board ink layer achieves a hardening effect. The hardened ink layer can effectively reduce the attack of the tin solution. Further, by using different ultraviolet spectra, different energies can be generated to polymerize monomers in different ink binders into polymers, so that the color film of the UV ink has good mechanical and chemical properties. UV ink also has the advantages of good water resistance, solvent resistance and wear resistance. The photoinitiator in the UV ink is a compound that is easily excited by light. After absorbing light, it is excited into free radicals, and the energy is transferred to the photosensitive molecules or photocrosslinking agents, so that the UV ink undergoes a photocuring reaction. UV ink is environmentally friendly and can effectively reduce the emission of pollutants. In addition to being solvent-free, UV ink also has advantages such as not easy to smear the plate, clear dots, bright and bright ink color, excellent chemical resistance, and low dosage.

[0038] S200, performing a degreasing operation on the light-cured circuit board to obtain a degreasing circuit board.

[0039] It is understandable that during the processing of the circuit board, grease and oxides are easily present on the copper surface of the circuit board, resulting in poor cleanliness and wettability of the copper surface of the circuit board. In order to improve the cleanliness and wettability of the copper surface of the circuit board, in this embodiment, after the ink layer of the circuit board is photocured, the circuit board after photocuring is degreased, which can not only remove the residual ink film and glue, but also remove the grease and oxides on the copper surface, making the copper surface clean and increasing wettability, thereby effectively improving the cleanliness and wettability of the copper surface of the circuit board, while ensuring the bonding strength between the primary copper and the pattern electroplated copper or nickel.

[0040] S300, performing micro-etching operation on the degreased circuit board to obtain a micro-etched circuit board.

[0041] It is understandable that after the circuit board is degreased, the copper surface of the circuit board may still have oxides that cannot be removed by the degreaser, thereby affecting the bonding strength of the copper surface of the circuit board and also affecting the effect of chemical tinning of the circuit board. In order to further improve the cleanliness of the circuit board surface and the bonding strength of the circuit board surface, in this embodiment, after the circuit board is degreased, a micro-etching agent is used to perform micro-etching on the circuit board in a micro-etching tank. The micro-etching function is to remove the oxides on the copper surface, provide fresh copper, and also roughen the copper surface so that the copper surface has good adhesion with the OSP layer. The micro-etching process can further ensure that the oxides on the copper surface are completely removed, and at the same time clean and roughen the copper surface of the circuit, ensure the bonding strength between the pattern electroplated copper and the primary copper, and facilitate the subsequent chemical tinning and electroplating operations of the circuit board.

[0042] S400, performing a prepreg operation on the micro-etched circuit board to obtain a prepreg circuit board.

[0043] It is understandable that during the processing of the circuit board, it is easy to carry harmful and polluting substances from the external environment, so that when the micro-etched circuit board is tinned in the chemical tinning tank, it is easy to destroy the tinning effect, and it will also shorten the life of the solution in the tinning tank. In order to further reduce the harmful and polluting substances brought into the tinning tank and extend the life of the solution in the tinning tank, in this embodiment, before the circuit board is placed in the chemical tinning tank for tinning, the micro-etched circuit board is pre-dipped so that the circuit board and the slots in the circuit board are fully infiltrated. The pre-dip operation can reduce the harmful and polluting substances brought into the tinning tank, and at the same time can protect the tinning solution to extend the life of the solution in the tinning tank.

[0044] S500, sequentially performing temperature adjustment operations and complex concentration adjustment operations on the tin solution, so that the temperature of the tin solution reaches 66° C. to 70° C. and the complex concentration reaches 140 g / L to 160 g / L.

[0045] It is understandable that chemical tinning changes the chemical potential of copper to cause a chemical replacement reaction of stannous ions in the solution. The reduced tin metal is deposited on the surface of the copper substrate to form a tin coating, and the metal complex adsorbed on the tin coating catalyzes the reduction of tin ions to metallic tin, so that the tin ions continue to be reduced to tin. However, in the actual production process, due to the chemical tin process's own characteristics, high acid concentration, thiourea concentration, high working temperature, immersion time and other superimposed factors, the solder mask ink is easily attacked by the solution to form peeling, resulting in short circuits after mounting and other problems. In order to reduce the attack of the solution on the solder resist ink and reduce the depth of lateral etching while ensuring the deposition rate, in this embodiment, the temperature adjustment operation and the complex concentration adjustment operation are performed on the tin solution in sequence, so that the temperature of the tin solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L. While ensuring the deposition rate, by adjusting the complex concentration and the operating temperature in the tin solution, under the conditions that the temperature of the tin solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L, the lateral etching depth of the tin solution on the circuit board can be effectively reduced, and the attack of the tin solution on the solder resist ink can be reduced, thereby effectively alleviating the problem of the solder resist layer falling off easily. Further, the median acidity of the tin solution is 5.2mol / l to 5.6mol / l.

[0046] S600, placing the pre-preg circuit board into the adjusted tin solution for chemical tinning operation.

[0047] In one embodiment, an acidic degreasing agent is used in the degreasing operation. It is understandable that by degreasing the circuit board after light curing, not only can the residual ink film and glue be removed, but also the grease and oxide on the copper surface can be removed, so that the copper surface is clean and the wettability is increased, thereby effectively improving the cleanliness and wettability of the copper surface of the circuit board, and at the same time ensuring the bonding force between the primary copper and the electroplated copper or nickel of the pattern. However, the ink in the circuit board has poor alkali resistance. If an alkaline degreasing agent is used, or the acidity median value of the degreasing agent, that is, the pH value is high, it is easy to damage the graphic circuit, and at the same time affect the effect of chemical tinning and damage the solder mask ink layer. In order to further improve the effect of chemical tinning and better protect the solder mask ink layer, in this embodiment, an acidic degreasing agent is used in the degreasing operation. The acidic degreasing agent is used to degreasing the circuit board after light curing, which can not only remove the residual film and glue of the ink, but also remove the grease and oxides on the copper surface, make the copper surface clean and increase the wettability, thereby effectively improving the cleanliness and wettability of the copper surface of the circuit board, and at the same time ensuring the bonding force between the primary copper and the pattern electroplated copper or nickel. Furthermore, the acidic degreasing agent can also play a certain protective effect on the pattern ink on the circuit board, thereby effectively reducing the attack of the liquid on the ink during chemical tinning.

[0048] Furthermore, the acidic degreasing agent includes an inorganic acid, a corrosion inhibitor, a wetting agent and a stabilizer. It is understandable that although most of the existing acidic degreasing agents can achieve a degreasing effect, they still have the following disadvantages: 1. The acidity of organic acids such as oxalic acid and citric acid is generally weak, and it is difficult to achieve the effect of rust removal, oil removal and oxide removal. A larger concentration of organic acid is required to have a significant degreasing effect, thereby increasing the material cost; 2. Amine compounds are often added to acidic degreasing agents as additives to improve the degreasing effect, but their ammonia nitrogen content is high and easy to cause pollution. In order to further improve the degreasing effect, environmental protection and stability of the acidic degreasing agent, in this embodiment, the acidic degreasing agent includes an inorganic acid, a corrosion inhibitor, a wetting agent and a stabilizer. The inorganic acid in the component can dissolve and remove the grease and oxides on the copper surface; the corrosion inhibitor mainly protects the surface of the circuit board, forms a stable acid-resistant adsorption protective film on the metal surface, and reduces the corrosion ability of the inorganic acid on the surface metal; the wetting agent mainly reduces the surface tension or interfacial tension of the solution. When the solution contacts the surface of the circuit board, the lipophilic group adheres to the surface of the board, and the hydrophilic group extends outward into the liquid, so that the surface of the circuit board can be wetted by the solution, thereby improving the degreasing performance; the stabilizer can maintain the chemical balance between the components, prevent light, thermal decomposition or oxidative decomposition, etc., thereby improving the stability of the solution and enabling the solution to maintain an excellent degreasing effect for a long time.

[0049] In one embodiment, the temperature in the degreasing operation is 30°C to 40°C. It is understandable that by degreasing the circuit board after light curing, not only can the residual ink film and glue be removed, but also the grease and oxide on the copper surface can be removed, so that the copper surface is clean and the wettability is increased, thereby effectively improving the cleanliness and wettability of the copper surface of the circuit board, and at the same time ensuring the bonding force between the primary copper and the electroplated copper or nickel of the pattern. However, if the temperature in the degreasing operation is too low, it is easy to cause poor degreasing effect; if the temperature in the degreasing operation is too high, it is easy to damage the ink layer of the circuit board, and affect the subsequent pre-dip operation and tinning operation. Too high a temperature is easy to accelerate the attack of the tinning solution on the ink layer. In order to further improve the stability of the circuit board, in this embodiment, the temperature in the degreasing operation is 30°C to 40°C, preferably, the temperature is 35°C. Under the above temperature conditions, the removal effect of grease and oxide on the copper surface of the circuit board can be effectively improved, and the stability of the tinning treatment of the circuit board can be further improved.

[0050] Furthermore, the degreasing operation time is 5 minutes to 7 minutes. It is understandable that if the degreasing operation time is short, the degreasing effect is poor, the grease and oxide residues on the copper surface are increased, and the cleanliness and wettability of the copper surface are poor; if the degreasing operation time is long, the degreasing agent is likely to cause adverse effects on the circuit board, such as corrosion of the circuit board material. In order to further improve the stability of the degreasing operation of the circuit board and enhance the degreasing effect, in this embodiment, the degreasing operation time is 5 minutes to 7 minutes, preferably, the degreasing operation time is 6 minutes. Under the above-mentioned degreasing operation time, the removal effect of grease and oxide on the copper surface of the circuit board can be effectively improved, the cleanliness and wettability of the copper surface of the circuit board can be further improved, and the stability of the tinning treatment of the circuit board can be further improved.

[0051] In one embodiment, the microetching agent in the microetching operation is a sodium persulfate solution. It is understandable that by performing a microetching operation on the circuit board in the microetching tank, it is possible to further ensure that the oxide on the copper surface is completely removed, and at the same time, the copper surface of the roughened circuit is cleaned, ensuring the bonding force between the graphic electroplated copper and the primary copper, and facilitating the subsequent chemical tinning operation and electroplating operation of the circuit board. However, some of the existing microetching agents used in this application are prone to problems such as difficult to control the etching rate, poor etching quality, and poor roughening effect. In order to further improve the stability and roughening uniformity of the microetching operation, in this embodiment, the microetching agent in the microetching operation is a sodium persulfate solution. The sodium persulfate solution has good stability in this application, can better control the roughening efficiency, and improve the roughening uniformity. At the same time, the sodium persulfate solution has good water washability. Furthermore, the sodium persulfate solution includes sodium persulfate (SPS) and sulfuric acid series. The micro-etching solution of sodium persulfate and sulfuric acid can evenly etch a very thin layer of copper (about 1 to 2 μm) on the surface of the copper substrate, and can also remove oxides and other impurities on the copper surface of the substrate, thereby obtaining a chemically cleaned rough surface, which makes the bonding effect of chemical tin deposition better.

[0052] Furthermore, the concentration of the sodium persulfate solution is 55 g / L to 65 g / L. It is understandable that if the concentration of the sodium persulfate solution in the micro-etching operation is too low, problems such as poor etching quality and poor roughening effect are likely to occur; if the concentration of the sodium persulfate solution in the micro-etching operation is too high, the sodium persulfate solution is likely to cause adverse effects on the circuit board, such as corroding the circuit board material. In order to further improve the stability of the micro-etching operation while ensuring the etching quality and roughening effect, in this embodiment, the concentration of the sodium persulfate solution is 55 g / L to 65 g / L, preferably, the concentration of the sodium persulfate solution is 60 g / L, so that the etching quality and roughening effect can be effectively improved, while further improving the stability of the micro-etching operation.

[0053] In one embodiment, the micro-etching operation time is 18 seconds to 22 seconds. It is understandable that if the micro-etching operation time is too short, problems such as poor etching quality and poor roughening effect are likely to occur; if the micro-etching operation time is too long, the micro-etching liquid is likely to cause adverse effects on the circuit board, such as corroding the circuit board material. In order to further improve the stability of the micro-etching operation while ensuring the etching quality and roughening effect, in this embodiment, the micro-etching operation time is 18 seconds to 22 seconds, preferably, the micro-etching operation time is 20 seconds, so that the etching quality and roughening effect can be effectively improved, while further improving the stability of the micro-etching operation.

[0054] In one of the embodiments, the temperature in the pre-dip operation is 40°C to 50°C. It is understandable that after the micro-etched circuit board is pre-dip, the circuit board and the slots in the circuit board are fully infiltrated. The pre-dip operation can reduce the introduction of harmful and polluting substances into the tinning tank, and at the same time protect the tinning solution to extend the life of the solution in the tinning tank. However, if the temperature in the pre-dip operation is too low, the problem of insufficient wetting is likely to occur; if the temperature in the pre-dip operation is too high, it is easy to damage the ink layer of the circuit board. In addition, if the temperature in the pre-dip operation is too different from the temperature in the tinning operation, the circuit board is prone to thermal expansion and contraction during the tinning process, thereby increasing the attack damage of the tinning solution activity on the ink layer, and then the ink layer falls off. In order to improve the stability of the pre-dip operation and reduce the damage of the tinning solution to the ink layer, in this embodiment, the temperature in the pre-dip operation is 40°C to 50°C, so that the circuit board can be fully infiltrated, further reducing the introduction of harmful and polluting substances into the tinning tank, and protecting the tinning solution to extend the life of the solution in the tinning tank. In addition, the temperature in the pre-dip operation is close to the temperature of the tinning solution in the tinning tank, avoiding the circuit board from easily expanding and contracting during the tinning process, thereby reducing the damage of the tinning solution to the ink layer.

[0055] In one embodiment, the temperature of the tin solution is 67° C. to 69° C. It is understood that chemical tinning is to change the chemical potential of copper to cause a chemical replacement reaction of stannous ions in the solution, and the reduced tin metal is deposited on the surface of the copper substrate to form a tin coating, and the metal complex adsorbed on the tin coating catalyzes the reduction of tin ions to metallic tin, so that the tin ions continue to be reduced to tin. If the temperature of the tinning solution is too low, the reaction during the chemical tinning process will be slow, the adhesion of the low tin will be weak, and the density will be poor, so that the tinning solution is easier to penetrate into the gaps of the circuit board, thereby enhancing the side etching reaction and deepening the side etching depth, making the solder mask ink layer susceptible to the attack of the solution to peel off, resulting in short circuits after mounting and other problems; if the temperature of the tinning solution is too high, thermal expansion reaction is likely to occur on the circuit board, making the adhesion of the bottom tin on the circuit board poor, and gaps are likely to occur in the circuit board, making the tinning solution easier to penetrate into the gaps of the circuit board, thereby enhancing the side etching reaction and deepening the side etching depth, making the solder mask ink layer susceptible to the attack of the solution to peel off, resulting in short circuits after mounting and other problems. In addition, the tinning solution temperature that is too low or too high is likely to damage the surface of the circuit board. In order to further reduce the damage of the tinning solution to the ink layer and improve the stability of the chemical tinning operation, in the present embodiment, the temperature of the tinning solution is 67°C to 69°C. While improving the adhesion of the base tin and the lattice density, it can also prevent the circuit board from thermal expansion and contraction during the tinning process, thereby ensuring the structural stability of the circuit board and making it more difficult for the tinning solution to penetrate into the gaps of the circuit board, thereby reducing or avoiding the side corrosion reaction, thereby further reducing the damage of the tinning solution to the ink layer and improving the stability of the chemical tinning operation.

[0056] In one embodiment, after the steps of adjusting the temperature and the complex concentration of the tin solution in sequence so that the temperature of the tin solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L, and before the step of placing the prepreg circuit board into the adjusted tin solution for chemical tinning, the tinning treatment method for the automotive circuit board of the present application also includes the following steps: preheating the prepreg circuit board with hot water, and the temperature during the hot water preheating operation is 62°C to 66°C. It is understandable that the temperature of the tin solution in the tinning tank is 66°C to 70°C, while the temperature of the circuit board at room temperature is below 28°C. It can be seen that the temperature of the circuit board at room temperature is quite different from the temperature of the tin solution in the tinning tank. If the circuit board is directly placed in the tinning tank for tinning, the circuit board is prone to thermal expansion and contraction due to the large temperature difference, resulting in poor adhesion of the bottom tin on the circuit board. At the same time, gaps are easily generated in the circuit board, making it easier for the tinning solution to penetrate into the gaps of the circuit board, thereby enhancing the side etching reaction, deepening the side etching depth, and making the solder mask ink layer susceptible to attack by the solution to form peeling, resulting in short circuits after mounting and other problems. In order to further reduce the damage of the tin solution to the ink layer and improve the stability of the chemical tinning operation, in this embodiment, the pre-impregnated circuit board is placed in a hot water tank for hot water preheating. On the one hand, the temperature of the circuit board can be steadily increased to 62°C to 66°C by hot water preheating instead of using heating means such as hot air. At the same time, immersing the circuit board in hot water for heating can prevent the circuit board from contacting with air during the heating process, thereby preventing oxidation problems. On the other hand, preheating the circuit board in hot water instead of tin solution or other reagents can effectively prevent the circuit board from reacting with the tin solution or other reagents in advance, thereby affecting the tinning effect.

[0057] Furthermore, after the step of preheating the prepreg circuit board with hot water, and before the step of placing the prepreg circuit board into the adjusted tin-plating solution for chemical tinning, the tinning treatment method for the automobile circuit board of the present application also includes the following steps: drying the circuit board after hot water preheating. It is understandable that after the circuit board after hot water preheating is taken out, some hot water beads will remain on the circuit board. If the circuit board is directly placed in the tinning tank for tinning, the residual moisture on the circuit board will directly dilute the tin-plating solution, thereby affecting the tinning effect. In order to reduce the attack and damage of the tin-plating solution to the ink layer, while improving the stability of the tinning operation and the tinning effect, in this embodiment, the circuit board after hot water preheating is dried to remove the residual moisture of the circuit board after hot water preheating, and prevent the residual moisture on the circuit board from diluting the tin-plating solution, thereby reducing the attack and damage of the tin-plating solution to the ink layer, while improving the stability of the tinning operation and the tinning effect.

[0058] In one embodiment, the specific method of the drying operation is to wipe the circuit board preheated with hot water using a sponge member slightly soaked in 66°C to 70°C tin solution. It is understandable that after the circuit board is taken out after being preheated with hot water, some hot water beads will remain on the circuit board. If the circuit board is directly placed in the tin sink for tinning, the residual moisture on the circuit board will directly dilute the tin solution, thereby affecting the tinning effect. If air drying or direct wiping is adopted, on the one hand, it is easy to cause oxidation problems due to contact with air; on the other hand, when the above drying method is used for drying, the temperature of the preheated circuit board will be reduced, so that the temperature of the circuit board during tinning is greatly different from the temperature of the tin solution in the tin sink. The circuit board is prone to thermal expansion and contraction due to the large temperature difference, which makes the adhesion of the bottom tin on the circuit board poor. At the same time, gaps are easily generated in the circuit board, so that the tin solution is easier to penetrate into the gaps of the circuit board, thereby enhancing the side etching reaction and deepening the side etching depth, making the solder mask ink layer susceptible to the attack of the solution to form peeling, resulting in short circuits after mounting. In order to maintain the dryness of the circuit board and the temperature stability of the circuit board after preheating, in this embodiment, a detachable sponge is set at the entrance of the tin sinking tank. Before wiping the preheated circuit board, the detachable sponge is placed in the tin solution taken from the tin sinking tank for micro-immersion operation. The composition, temperature and concentration of the tin solution are consistent with the tin solution of the tin sinking tank. After the micro-immersion operation is completed, one-half to two-thirds of the solution in the detachable sponge is squeezed out, while ensuring that the environmental factors of the detachable sponge are consistent with the tin sinking tank, and also creating a water absorption space for the detachable sponge. Then, the detachable sponge is installed at the entrance of the tin sinking tank, thereby effectively removing the residual moisture in the preheated circuit board, while ensuring the temperature of the preheated circuit board and avoiding other factors from interfering with the tin solution, thereby maintaining the dryness of the circuit board and maintaining the temperature stability of the circuit board after preheating. Further, the number of detachable sponges is 2 to 5, and the detachable sponges are arranged in sequence at the entrance of the tin sinking tank, thereby further ensuring that the residual moisture in the preheated circuit board is fully absorbed.

[0059] Example 1

[0060] The ink layer on the circuit board is subjected to a photocuring operation, and the ink is cured by ultraviolet light of a UV machine to obtain a photocured circuit board; after the ink layer on the circuit board is subjected to a photocuring operation, the circuit board subjected to the photocuring operation is then subjected to a degreasing operation, wherein the temperature of the degreasing operation is 30°C and the time of the degreasing operation is 5 minutes; after the degreasing operation on the circuit board, a microetching agent is then used to perform a microetching operation on the circuit board in a microetching tank to obtain a microetched circuit board, wherein the microetching agent is a sodium persulfate solution with a concentration of 55g / L, and the time of the microetching operation is 18 seconds; before the circuit board is placed in a chemical tinning tank for tinning, the microetched circuit board is pre-impregnated to obtain a pre-impregnated circuit board, wherein the temperature of the pre-impregnation operation is 40°C; the tin solution is subjected to a temperature adjustment operation and a complex concentration adjustment operation in sequence, so that the temperature of the tin solution reaches 66°C, the complex concentration reaches 140g / L, and the median acidity is 5.2mo1 / l; finally, the pre-impregnated circuit board is placed in the adjusted tin solution for chemical tinning. The solder resist ink used in this embodiment is "Rongda H-8100MBKHF001".

[0061] Example 2

[0062] The ink layer on the circuit board is subjected to a photocuring operation, and the ink is cured by ultraviolet light from a UV machine to obtain a photocured circuit board; after the ink layer on the circuit board is subjected to a photocuring operation, the circuit board subjected to the photocuring operation is then subjected to a degreasing operation, wherein the temperature of the degreasing operation is 40°C, and the time of the degreasing operation is 7 minutes; after the degreasing operation on the circuit board, a microetching agent is then used to perform a microetching operation on the circuit board in a microetching tank to obtain a microetched circuit board, wherein the microetching agent is a sodium persulfate solution with a concentration of 65g / L, and the time of the microetching operation is 22 seconds; before the circuit board is placed in a chemical tinning tank for tinning, the microetched circuit board is pre-impregnated to obtain a pre-impregnated circuit board, wherein the temperature of the pre-impregnation operation is 50°C; the tin solution is subjected to a temperature adjustment operation and a complex concentration adjustment operation in sequence, so that the temperature of the tin solution reaches 70°C, the complex concentration reaches 160g / L, and the median acidity is 5.5mo1 / l; finally, the pre-impregnated circuit board is placed in the adjusted tin solution for chemical tinning. The solder resist ink used in this embodiment is "Rongda H-9100SK01HF01 (halogen-free and silicone-free)".

[0063] Example 3

[0064] The ink layer on the circuit board is subjected to a photocuring operation, and the ink is cured by ultraviolet light from a UV machine to obtain a photocured circuit board; after the ink layer on the circuit board is subjected to a photocuring operation, the circuit board subjected to the photocuring operation is then subjected to a degreasing operation, wherein the temperature of the degreasing operation is 35°C, and the time of the degreasing operation is 6 minutes; after the degreasing operation on the circuit board, a microetching agent is then used to perform a microetching operation on the circuit board in a microetching tank to obtain a microetched circuit board, wherein the microetching agent is a sodium persulfate solution with a concentration of 60g / L, and the time of the microetching operation is 20 seconds; before the circuit board is placed in a chemical tinning tank for tinning, the microetched circuit board is pre-impregnated to obtain a pre-impregnated circuit board, wherein the temperature of the pre-impregnation operation is 45°C; the tinning solution is subjected to a temperature adjustment operation and a complex concentration adjustment operation in sequence, so that the temperature of the tinning solution reaches 68°C, the complex concentration reaches 150g / L, and the median acidity is 5.6mo1 / l; finally, the pre-impregnated circuit board is placed in the adjusted tinning solution for chemical tinning. The solder resist ink used in this embodiment is "Rongda H-9100SK01HF01 (halogen-free and silicone-free)".

[0065] Comparative Example 1

[0066] The ink layer on the circuit board is subjected to a photocuring operation, and the ink is cured by ultraviolet light of a UV machine to obtain a photocured circuit board; after the ink layer on the circuit board is subjected to a photocuring operation, the circuit board subjected to the photocuring operation is then subjected to a degreasing operation, wherein the temperature of the degreasing operation is 40°C, and the time of the degreasing operation is 7 minutes; after the degreasing operation on the circuit board, a microetching agent is then used to perform a microetching operation on the circuit board in a microetching tank to obtain a microetched circuit board, wherein the microetching agent is a sodium persulfate solution with a concentration of 65g / L, and the time of the microetching operation is 22 seconds; before the circuit board is placed in a chemical tinning tank for tinning, the microetched circuit board is pre-impregnated to obtain a pre-impregnated circuit board, wherein the temperature of the pre-impregnation operation is 50°C; the tin solution is subjected to a temperature adjustment operation and a complex concentration adjustment operation in sequence, so that the temperature of the tin solution reaches 71°C, the complex concentration reaches 170g / L, and the median acidity is 6.5mo1 / l; finally, the pre-impregnated circuit board is placed in the adjusted tin solution for chemical tinning. The solder resist ink used in this embodiment is "Rongda H-9100SK01HF01 (halogen-free and silicone-free)".

[0067] Comparative Example 2

[0068] The ink layer on the circuit board is subjected to a photocuring operation, and the ink is cured by ultraviolet light of a UV machine to obtain a photocured circuit board; after the ink layer on the circuit board is subjected to a photocuring operation, the circuit board subjected to the photocuring operation is then subjected to a degreasing operation, wherein the temperature of the degreasing operation is 40°C, and the degreasing operation time is 7 minutes; after the degreasing operation on the circuit board, a microetching agent is then used to perform a microetching operation on the circuit board in a microetching tank to obtain a microetched circuit board, wherein the microetching agent is a sodium persulfate solution with a concentration of 65g / L, and the microetching operation time is 22 seconds; before the circuit board is placed in a chemical tinning tank for tinning, the microetched circuit board is pre-impregnated to obtain a pre-impregnated circuit board, wherein the pre-impregnation temperature is 50°C; the tin solution is subjected to a temperature adjustment operation and a complex concentration adjustment operation in sequence, so that the temperature of the tin solution reaches 72°C, the complex concentration reaches 175g / L, and the median acidity is 6.6mo1 / l; finally, the pre-impregnated circuit board is placed in the adjusted tin solution for chemical tinning. The solder resist ink used in this embodiment is "Rongda H-9100SK01HF01 (halogen-free and silicone-free)".

[0069] The circuit obtained by the processing method of the above embodiment 2 is as follows Figure 2 As shown, the circuit obtained by using the processing method of the above comparative example 1 is as follows Figure 3 As shown, according to Figure 2 and Figure 3 It can be seen that Figure 2 The ink lateral erosion depth, that is, the attack depth of the liquid medicine is small; Figure 3 The side etching depth of the ink, that is, the attack depth of the solution, is relatively large. It can be seen that the tinning treatment method for automobile circuit boards of the present application can effectively reduce the side etching depth of the circuit board by the tinning solution, and reduce the attack of the tinning solution on the solder mask ink, thereby effectively alleviating the problem of the solder mask layer falling off easily, by adjusting the complex concentration and operating temperature in the tinning tank solution while ensuring the deposition rate, under the conditions that the tinning solution temperature reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L.

[0070] Compared with the prior art, the present invention has at least the following advantages:

[0071] 1. In the tinning treatment method for automobile circuit boards of the present invention, the ink layer on the circuit board is first photocured to achieve a hardening effect on the ink layer of the circuit board, and the hardened ink layer can effectively reduce the attack of the tinning solution; then the circuit board after photocuring is degreased, which can not only remove the residual film and glue of the ink, but also remove the grease and oxides on the copper surface, so that the copper surface is clean and the wettability is increased; further, by micro-etching the circuit board after degreasing, it can further ensure that the oxides on the copper surface are completely removed, and at the same time, the copper surface of the circuit is cleaned and roughened, so as to ensure the bonding force between the pattern electroplated copper and the primary copper, and facilitate the subsequent electroplating operation of the circuit board; and the pre-impregnation operation can reduce the introduction of harmful and polluting substances into the tinning tank, so as to extend the life of the solution in the tinning tank.

[0072] 2. In the tinning treatment method for automobile circuit boards of the present invention, the temperature adjustment operation and the complex concentration adjustment operation are performed on the tinning solution in sequence, so that the temperature of the tinning solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L. While ensuring the deposition rate, by adjusting the complex concentration and the operating temperature in the tinning tank solution, under the conditions that the temperature of the tinning solution reaches 66°C to 70°C and the complex concentration reaches 140g / L to 160g / L, the side etching depth of the circuit board by the tinning solution can be effectively reduced, and the attack of the tinning solution on the solder resist ink can be reduced, thereby effectively alleviating the problem of easy detachment of the solder resist layer.

[0073] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for treating automobile circuit boards by immersion tinning, characterized in that: The following steps are involved: Performing a photocuring operation on the ink layer on the circuit board to obtain a photocured circuit board; Degreasing the light-cured circuit board to obtain a degreasing circuit board; The degreased circuit board is micro-etched to obtain a micro-etched circuit board; wherein the micro-etching agent in the micro-etching operation is a sodium persulfate solution; the sodium persulfate solution includes sodium persulfate (SPS) and a sulfuric acid series, and the concentration of the sodium persulfate solution is 55 g / L to 65 g / L; the time is 18 seconds to 22 seconds, so as to evenly etch away a thin layer of copper with a thickness of 1 to 2 μm on the surface of the copper substrate; Performing a prepreg operation on the micro-etched circuit board to obtain a prepreg circuit board; wherein the temperature during the prepreg operation is 40° C. to 50° C.; Performing a hot water preheating operation on the prepreg circuit board, wherein the temperature of the hot water preheating operation is 62° C. to 66° C.; The circuit board preheated by hot water is dried; the specific method of the drying operation is to wipe the circuit board preheated by hot water with a detachable sponge member that has been slightly dipped in a tin solution at 66°C to 70°C; wherein the detachable sponge member is provided at the entrance of the tin sinking tank, and before wiping the preheated circuit board, the detachable sponge member is placed in the tin solution taken from the tin sinking tank for slight dipping, and after the slight dipping operation is completed, one-half to two-thirds of the solution in the detachable sponge member is squeezed out, and then the detachable sponge member is installed at the entrance of the tin sinking tank; The tin solution is subjected to temperature adjustment and complex concentration adjustment in sequence, so that the temperature of the tin solution reaches 66° C. to 70° C., and the complex concentration reaches 140 g / L to 160 g / L; the median acidity of the tin solution is 5.2 mol / L to 5.6 mol / L; The pre-preg circuit board is placed in the adjusted tin solution to perform chemical tinning operation.

2. The tinning treatment method for automobile circuit boards according to claim 1, characterized in that: An acidic degreasing agent is used in the degreasing operation.

3. The tinning treatment method for automobile circuit boards according to claim 2, characterized in that: The acidic degreasing agent comprises an inorganic acid, a corrosion inhibitor, a wetting agent and a stabilizer.

4. The tinning treatment method for automobile circuit boards according to claim 1, characterized in that: The temperature in the degreasing operation is 30°C to 40°C.

5. The tinning treatment method for automobile circuit boards according to claim 1, characterized in that: The degreasing operation time is 5 minutes to 7 minutes.

6. An automotive circuit board, characterized in that: The automobile circuit board is prepared by using the tinning treatment method for automobile circuit boards as described in any one of claims 1 to 5.

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