1. This article mainly introduces the organic solder protection film (OSP) technology used in printed circuit boards.

2. OSP stands for organic solder mask, also known as a copper protective agent. In English, it is referred to as Preflux.

3. Simply put, OSP involves applying a layer of organic film to a clean bare copper surface, providing anti-oxidation, heat resistance, and moisture resistance.

4. To prevent the copper surface from rusting (whether oxidized or vulcanized) in normal environments, the protective film must be quickly removed during subsequent high-temperature soldering.

5. This allows the exposed clean copper surface to bond with molten solder, forming a strong solder joint in a very short time.

6. In fact, OSP is not a new technology; it has been around for more than 35 years, longer than SMT.

7. The operating system offers many advantages, such as good flatness, no intermetallic compound (IMC) formation on the pad copper, and effective wetting during soldering.

8. It is also cost-effective (lower than HASL) and consumes less processing energy, among other benefits.

9. OSP technology is very popular in Japan, with about 40% of single-sided panels and nearly 30% of double-sided panels utilizing this technology.

10. In the US, OSP technology usage has also surged, increasing from 10% in 1997 to 35% in 1999.

1. There are three types of materials used for the operating system: Rosin, Active Resin, and Methazole. Currently, the most widely adopted is the prophazole operating system. The authentic OSP has undergone about five generations of improvements and is referred to as BTAIABIASBA, with the latest being APA.

2. The process flow of the PCB board operating system includes degreasing, secondary washing, micro-etching, secondary washing, pickling, DI washing, film forming, air drying, DI washing, and drying.

3. Degreasing is crucial. The effectiveness of the degreasing process directly influences the quality of the film. If the degreasing is inadequate, the film thickness will be inconsistent. Concentration can be controlled through solution analysis, and if the oil removal is insufficient, regular checks should be conducted.

4. Micro-etching aims to create a rougher copper surface for better adhesion. The thickness of the micro-etching significantly impacts the film formation rate, establishing a stable film thickness. Typically, the micro-etching thickness should be maintained between 1.0 and 1.5 μm. Before each shift, the micro-etching duration can be adjusted based on the micro-etching rate.

5. Membrane formation is critical. Prior to film application, washing with DI water is essential to prevent contamination. Post-film formation washing should also utilize DI water, with the pH level controlled between 4.0 and 7.0 to avoid pollution and damage to the film. A key aspect of the operating system process is regulating the thickness of the anti-oxidation layer. The film’s high-temperature resistance (190°-200°C) ultimately affects the soldering performance of the electronic assembly line. Poor solubility in the auxiliary solder can compromise soldering efficiency, so the film thickness should generally be kept between 0.2 and 0.5 μm.

6. Disadvantages of PCB OSP technology exist. OSP has its limitations, including the variability in actual formulations. Proper certification and supplier selection are essential.

7. One notable drawback of OSP technology is that the protective film is very thin and prone to scratches or bruising. Additionally, OSP film that has undergone multiple high-temperature soldering processes may discolor or crack, negatively impacting soldering performance and reliability.

8. The solder paste printing process must be executed well, as poorly printed boards cannot be cleaned with IPA without risking damage to the operating system layer.

9. Measuring the thickness of the transparent, non-metal OSP layer can be challenging, and assessing the transparency and coverage of the coating is not straightforward, making it difficult to evaluate the quality stability of PCB suppliers.

10. There is no intermetallic compound (IMC) isolation between the copper of the pad and the tin of the solder. The rapid growth of SNCU in lead-free technology affects the reliability of solder joints.

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