A water phase hole sealing treatment method for selected PCBs

Abstract

A water phase hole sealing treatment method for selected PCB, the selected PCB is printed circuit board after chemical nickel-gold plating treatment and before OSP surface treatment, comprising the following steps: S1, preparing water phase hole sealing agent medicine: the water phase hole sealing agent is alkaline aqueous solution system, the mass percentage concentration is 5%-15%, the pH value is 8.5-9.5; S2, soaking treatment: the selected PCB after chemical nickel-gold plating treatment is soaked in the water phase hole sealing agent medicine prepared in step S1 under room temperature, the soaking time is 1-2 minutes, the water phase hole sealing agent penetrates into the micropore inside the nickel-gold layer, complexing passivation is carried out on the micropore defect site, and a protective film is formed on the surface of the nickel-gold layer; S3, DI water washing: the selected PCB after soaking treatment in step S2 is soaked in deionized water for 1-2 minutes; S4, OSP treatment: the selected PCB after water washing in step S3 is subjected to OSP treatment.

Description

Technical Field

[0001] This invention relates to the field of PCB board technology, specifically to a method for aqueous sealing treatment of PCB boards. Background Technology

[0002] When performing OSP surface treatment on a chemical PCB (surface treatment of chemical nickel-gold plating + OSP), the nickel-gold layer at the solder pad position cannot resist the attack of the micro-etching solution, resulting in corrosion of the nickel-gold layer and blackening, which affects the appearance and soldering effect. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for aqueous via sealing of PCBs, wherein the PCB to be treated with OSP surface treatment after chemical nickel-gold plating is subjected to the following steps: S1, Preparation of aqueous sealing agent solution: The aqueous sealing agent is an alkaline aqueous solution system with a mass percentage concentration of 5%~15% and a pH value of 8.5~9.5; S2, Immersion treatment: The selected PCB after chemical nickel-gold immersion treatment is immersed in the aqueous sealing agent solution prepared in step S1 at room temperature for 1 to 2 minutes, so that the aqueous sealing agent can penetrate into the micropores of the nickel-gold layer, complex and passivate the defective parts of the micropores, and form a protective film on the surface of the nickel-gold layer. S3, DI water wash: Immerse the selected PCB after soaking in step S2 in deionized water for 1-2 minutes; S4, OSP treatment: The selected PCB after water washing in step S3 is subjected to OSP treatment.

[0004] In some embodiments, the aqueous sealing agent in step S2 comprises a penetrant, a complexing agent, and a film-forming agent, and the penetration process includes the following steps: S21, penetrates, exchanges, and cleans trace residues deep within the micropores of the coating; S22, performs layer-by-layer complexation passivation on the exposed metal surface at the micropore defect location; S23 forms a dense protective film on the surface of the nickel-gold layer and inside the micropores through hydrogen bonding.

[0005] In some embodiments, step S4 sequentially includes degreasing, micro-etching, pre-immersion, and OSP treatment. Beneficial effects

[0006] This invention provides a method for selectively sealing vias in PCBs using a aqueous phase. Compared with existing technologies, it offers the following advantages: This invention adds an aqueous sealing agent treatment step before OSP treatment. Utilizing the strong permeability and wettability of the aqueous sealing agent, the active ingredients penetrate deep into the micropores of the nickel-gold layer, complexing and passivating the defective areas of the micropores and forming a protective film on the coating surface and inside the micropores. This fundamentally blocks the channels for acid radical ions in the micro-etching solution to penetrate into the pores of the coating, completely solving the technical problem of corrosion and blackening of the nickel-gold layer of PCB during OSP treatment. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0008] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0009] Please see Figure 1 This invention provides a technical solution: a method for aqueous sealing of PCBs, wherein the PCB is a printed circuit board that has undergone chemical nickel plating and is to be subjected to OSP surface treatment, comprising the following steps: S1, Preparation of aqueous sealing agent solution: The aqueous sealing agent is an alkaline aqueous solution system with a mass percentage concentration of 5%~15% and a pH value of 8.5~9.5; S2, Immersion treatment: The selected PCB after chemical nickel-gold immersion treatment is immersed in the aqueous sealing agent solution prepared in step S1 at room temperature for 1 to 2 minutes, so that the aqueous sealing agent can penetrate into the micropores of the nickel-gold layer, complex and passivate the defective parts of the micropores, and form a protective film on the surface of the nickel-gold layer. S3, DI water wash: Immerse the selected PCB after soaking in step S2 in deionized water for 1-2 minutes; S4, OSP treatment: The selected PCB after water washing in step S3 is subjected to OSP treatment.

[0010] In this embodiment, the aqueous sealing agent in step S2 comprises a penetrant, a complexing agent, and a film-forming agent, and the penetration process includes the following steps: S21, penetrates, exchanges, and cleans trace residues deep within the micropores of the coating; S22, performs layer-by-layer complexation passivation on the exposed metal surface at the micropore defect location; S23 forms a dense protective film on the surface of the nickel-gold layer and inside the micropores through hydrogen bonding.

[0011] In this embodiment, step S4 sequentially includes degreasing, micro-etching, pre-immersion, and OSP treatment.

[0012] This application develops a novel process for producing PCBs using an aqueous sealing agent to protect the nickel-gold layer from corrosion, thereby ensuring the product quality of the PCBs.

[0013] Specifically, selective PCBs refer to printed circuit boards with two or more surface treatment processes. One type of selective PCB produced by our company undergoes a surface treatment process of first chemically deposited nickel-gold followed by OSP treatment. This requires depositing an OSP film on the copper surface without depositing it on the gold surface, as this would cause corrosion or discoloration. However, during the micro-etching process in OSP treatment, the nickel-gold layer of the selective PCB is easily attacked by the micro-etching solution, causing gold surface corrosion and discoloration, affecting the product's appearance and soldering performance. The root cause of the corrosion of the nickel-gold layer in selective PCBs by micro-etching solutions is that the nickel-gold layer after selective PCB immersion gold plating contains numerous micropores. During the micro-etching process in OSP treatment, acid ions in the micro-etching solution penetrate into the plating pores, causing corrosion and blackening of the nickel-gold layer.

[0014] To prevent acid radicals in the micro-etching solution from penetrating the pores of the coating and causing corrosion and blackening of the nickel-gold layer, the existing process method is to increase the deposition thickness of the nickel-gold layer during the immersion nickel-gold surface treatment. Although this method can make the coating denser and reduce porosity, a large number of pores will still exist in the coating. Although it can alleviate the corrosion and blackening of the nickel-gold layer to a certain extent, it cannot fundamentally solve the problem. In addition, increasing the thickness of the nickel-gold layer will increase production costs.

[0015] The traditional process is as follows: pre-process → pre-treatment for nickel-gold plating → nickel plating → gold plating → forming → electrical testing → FQC → OSP → post-process. The main reason for the corrosion and blackening of the nickel-gold layer is the entry of acid radicals into the gold layer pores in the micro-etching solution. Therefore, how to effectively prevent acid radicals from entering the gold layer pores and causing corrosion and blackening of the nickel-gold layer is the technical problem that needs to be solved. To address this issue, this application develops a novel manufacturing process that adds an aqueous sealing agent treatment step before OSP surface treatment. This completely solves the problem of acid ions entering the gold layer pores, leading to corrosion and blackening of the nickel-gold layer. This specific aqueous sealing agent possesses superior permeability and wettability, allowing it to penetrate deep into the micropores of the plating layer. Its working principle is as follows: A) It penetrates, exchanges, and cleans trace residues deep within the micropores of the plating layer; B) It performs layer-by-layer complexation and passivation of various metals at defective areas. C. Finally, hydrogen bonds are formed on the coating surface. This film can effectively prevent the nickel-gold layer from being corroded and blackened by micro-etching solutions, and will not hinder the normal coating of copper surfaces that need OSP surface treatment.

[0016] The process flow is as follows: pre-process → pre-treatment of nickel-gold plating → nickel plating → gold plating → molding → electrical testing → FQC → aqueous sealing agent treatment → OSP → post-process.

[0017] This invention primarily involves adding an aqueous sealing agent treatment step before OSP (Optical Sealant Processing) to form a protective film on the surface of the nickel-gold layer of the PCB. After DI (Dissolved Injection) washing, the PCB undergoes OSP line treatment, thus solving the problem of corrosion and blackening of the nickel-gold layer by micro-etching solutions during OSP. Compared with existing technologies that increase the thickness of the nickel-gold layer, this invention not only completely solves the problem of corrosion and blackening of the nickel-gold layer of the PCB by micro-etching solutions during OSP, but also does not hinder the normal film application on the copper surface that requires OSP surface treatment, and further reduces production costs.

[0018] According to testing by the internationally recognized testing organization SGS, the aqueous sealing agent described in this invention fully complies with the EU RoHS standard, and the waste liquid generated can be treated as general electroplating wastewater, making it safe and environmentally friendly.

[0019] Among them, chemical nickel-gold plating includes the following steps: nickel-gold pretreatment, nickel plating, and gold plating; The aqueous phase sealing agent treatment includes the following steps: preparing the aqueous phase sealing agent solution, manual soaking, and DI water washing; OSP treatment includes the following steps: degreasing, micro-etching, pre-immersion, and OSP treatment. The procedure for aqueous sealing agent treatment is as follows: 1. Prepare the aqueous phase sealing agent solution, that is, prepare 20L of aqueous phase sealing agent solution with a concentration of about 10% in a solution tank with a volume of about 25L; 2. Manual soaking: Use a slatted frame to immerse the chemical selection plate in the prepared aqueous sealing agent for about 90 seconds at room temperature. 3. DI water wash: Immerse the selection plate treated with aqueous sealing agent in DI water for 1-2 minutes.

[0020] Process conditions for aqueous sealing agent treatment: Drug concentration 5%-15% 10% pH value 8.5-9.5 9.0 Soaking time 1-2 min 90s temperature room temperature / Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

Claims

1. A method for water-phase sealing of PCBs, characterized in that: The PCB selected for OSP surface treatment is a printed circuit board that has undergone chemical nickel-gold plating and is about to be processed. The process includes the following steps: S1, Preparation of aqueous sealing agent solution: The aqueous sealing agent is an alkaline aqueous solution system with a mass percentage concentration of 5%~15% and a pH value of 8.5~9.5; S2, Immersion treatment: The selected PCB after chemical nickel-gold immersion treatment is immersed in the aqueous sealing agent solution prepared in step S1 at room temperature for 1 to 2 minutes, so that the aqueous sealing agent can penetrate into the micropores of the nickel-gold layer, complex and passivate the defective parts of the micropores, and form a protective film on the surface of the nickel-gold layer. S3, DI water wash: Immerse the selected PCB after soaking in step S2 in deionized water for 1-2 minutes; S4, OSP treatment: The selected PCB after water washing in step S3 is subjected to OSP treatment.

2. The method for water-phase sealing of PCBs according to claim 1, characterized in that: The aqueous sealing agent in step S2 comprises a penetrant, a complexing agent, and a film-forming agent, and the penetration process includes the following steps: S21, penetrates, exchanges, and cleans trace residues deep within the micropores of the coating; S22, performs layer-by-layer complexation passivation on the exposed metal surface at the micropore defect location; S23 forms a dense protective film on the surface of the nickel-gold layer and inside the micropores through hydrogen bonding.

3. The method for water-phase sealing of PCBs according to claim 1, characterized in that: Step S4 includes degreasing, micro-etching, pre-immersion, and OSP treatment in sequence.

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