What is Black Pad
Black pad is a specific defect that primarily affects BGA (Ball Grid Array) components. It refers to the corrosion and oxidation of the electroless nickel (EN) layer on the PCB, particularly at the boundaries of the nickel nodules. This corrosion gradually spreads, resulting in a black appearance on the surface of the PCB.
The black pad issue can have significant implications for the reliability and performance of the PCB. It can lead to reduced solderability, making it difficult for solder to properly adhere to the affected areas. This can result in weakly formed solder joints that are more prone to breaking under pressure. When these joints break, they expose the corroded nickel beneath, hence the term “black pad.”
The cause of black pad is often attributed to excessive phosphorus or contamination in the nickel plating bath during the ENIG (Electroless Nickel Immersion Gold) process. The presence of black pad can lead to solder joint failures, which can cause electrical connectivity issues and potentially result in the malfunctioning of the electronic device.
To address the black pad issue, manufacturers have developed strategies to minimize its occurrence. These strategies involve process optimization and control to reduce the risk of black pad formation. However, black pad remains a challenge in the PCB industry, and ongoing research and development efforts are focused on mitigating its impact and ensuring the reliability and quality of electronic devices.