OSP PCB surface processing process and advantages

OSP (Organic solderable preservatives) is a lead -free surface treatment process, which is mainly used for SMT surface -packed circuit boards. Compared to the traditional HASL (HOT Air Solder Leveling) process, the OSP process does not require high -temperature melting treatment, which can reduce the risk of metal corrosion, environmental pollution and electronic component damage, so it is widely used in the electronic manufacturing industry.

OSP principle

The basic principle of the OSP process is to coat a layer of organic substances on the PCB surface to form a protective layer to prevent copper surface oxidation and corrosion. This protective layer is generally mixed with chemicals such as organic acids and nitrogen. The main chemicals include:

1. Organic acid: such as acetic acid, propionic acid, etc., mainly used to regulate pH values and enhance chemical reactions.

2. Nitride compounds: such as nitric acid, nitrite, etc., which are mainly used to increase the adhesion and durability of the protective layer.

3. Other additives: such as surfactants, anti -oxidants, etc., to increase the stability and durability of the coating agent.

Step of OSP process

1. Pre -processing: Chemical treatment on the PCB surface, remove oxides and pollutants, so that the surface is clean and smooth, which is convenient for subsequent coating and response.

2. Coating: Apply a layer of OSP coating agent on the surface of the PCB, and form a protective layer through drying and other processes.

3. CIT of: Put PCB in a cured furnace, heated it to a certain temperature, so that the OSP coating agent is solidified to form a protective film.

4. Detection: The solidified PCB is detected, including testing of indicators such as adhesion, thickness, and flatness.

5. SMT Paste: Put the electronic component on the surface of the PCB processing after OSP processing.


The OSP process has the advantages of environmental protection, lead -free, and suitable for microelectronics manufacturing. However, its processing process is more complicated and requires strict control of the composition and quality of coating agents to ensure the quality and stability of PCB. When using the OSP process, you need to pay attention to the following issues:

1. The composition and quality of theOSP coating agent have an important impact on the quality and stability of PCB. It should be selected for the appropriate chemicals and suppliers to avoid using inferior coating agents.

2. The coating thickness of theOSP coating agent also has an important impact on the quality and stability of PCB. It should be selected different thickness according to different PCB requirements. Generally speaking, the thickness of OSP coating agent should be controlled at 0.2-0.5um. between.

3. The curing time and temperature of theOSP coating agent are also very important for the quality and stability of the PCB. You should choose the appropriate curing conditions according to different coating agents and PCB requirements.

4. The adhesion and durability of theOSP coating agent are also the key indicators of the quality of PCB. It should be ensured by strict quality testing and testing to ensure its quality and stability.

5.OSP process is a green and environmentally friendly lead -free surface treatment process. It uses organic polymers as coating agents to form a protective film on the PCB surface to protect the PCB surface without oxidation or corrosion. Compared with the traditional Hasl process, the advantage of the OSP process is that the coating agent is environmentally friendly, uniform coating, non -welded ball, and easy to weld. Therefore, in modern electronics manufacturing, the OSP process is widely used.

OSP advantage

The advantages of OSP can be summarized as:

• Simple process and reusable use: The circuit board with OSP can easily be re -made by PCB manufacturers. In this way, once the PCB preparation personnel find that the coating is damaged, the new coating can be used.

• Good wettability: When the welds encounter holes and pads, OSP coated circuit boards perform better in welded wetting.

• Environmental friendly: Because water -based compounds are applied in the generation of OSP, it will not cause harm to the environment, and it will only fall into people’s expectations for the green world. Therefore, OSP is the best choice for electronic products that meet green regulations such as ROHS Essence

PCB cost benefits: As simple compounds and simple manufacturing processes are applied during the OSP manufacturing process, the cost of OSP in all types of surface processing is very prominent. Its cost is lower, resulting in the lower cost of the final circuit board.

• Return welding suitable for double -sided SMT assembly: With the continuous development and progress of OSP, it has been accepted by single -sided SMT assembly and double -sided SMT assembly, which greatly expanded its application field.

• Low welding ink requirements: The storage requirements of OSP PCB for long storage time requirements Due to the very thin preservatives produced by OSP technology, it is easy to cut, so it must be very careful during transportation and transportation. OSP is exposed to high temperature and high humidity for a long time as a surface -processed PCB, which may occur on the surface of the PCB, which often causes low -weldability.

How OSP Manufactured

1.The first step is cleaning, which removes organic contaminants such as oil and oxidation films from the copper foil, the main component of the OSP. Insufficient cleaning can result in an uneven thickness of the created preservative. To achieve high-quality OSP films, the concentration of the cleaning liquid must be within a certain range according to laboratory standards. The cleaning process must be regularly monitored to ensure the required standard is met. If the desired results are not achieved, the cleaning liquid should be changed.

2.The second block is Topography Enhancement, where micro-etching is used to remove the oxidation produced on the copper foil that causes strong bonding between the copper foil and organic solderability preservative solution. The film build rate depends on the micro-etching speed. To achieve a smooth film thickness, the speed of micro-etching must be stable. The range for micro-etching speed is about 1.0 to 1.5 micrometers per minute.

3.The best option is to use a rinse before creating the preservative, as OSP solution can get polluted by ions, which can cause tarnishing after the completion of the reflow soldering process. In addition to that, DI rinse must be used after the creation of the preservative with a pH value of 4 to 7. If these parameters are not followed, the preservative can be destroyed due to pollution.

4.The OSP PCB coating is then applied to the cleaned copper surface through an adsorption process. The OSP solution contains organic compounds such as benzimidazoles, imidazoles, and benzotriazoles that form a thin layer on the copper surface. The thickness of the coating can be controlled by adjusting the concentration and immersion time of the solution.

5.After the coating is applied, the PCB is dried and cured in a controlled environment to remove any remaining moisture and to ensure proper adhesion of the OSP layer.

6.Once the coating is applied, the PCB is inspected for any defects or irregularities. The OSP-coated circuit boards are then subjected to various PCB tests to ensure their quality, reliability, and performance.