What is Drying Time
Drying time is the duration required for a solvent-based acrylic conformal coating to dry out as the solvents evaporate. Unlike other types of conformal coatings that undergo both drying and curing processes, the acrylic resin in this specific coating does not polymerize or cure. Instead, it simply dries out over time. This unique characteristic allows the coating to be re-dissolved back into the evaporated solvents and reform the coating.
Drying time is a critical factor to consider when working with components and PCBs as it directly impacts their functionality and reliability. The IPC (Institute for Printed Circuits) has established the IPC-STANDARD JSTD 033C, which provides guidelines and regulations for determining the recommended drying times for components. It is important to note that the drying time may vary depending on the Moisture Sensitivity Level (MSL) of the components or PCBs. MSL is a classification system used in the PCB industry to assess the level of sensitivity of components to moisture.
The complexity of a PCB’s structure, including the number of surface layers and the presence of copper divisions, can also influence the drying time. In cases where PCBs have numerous surface layers and copper divisions, the thickness must be multiplied by a factor of 2 before determining the drying time. Additionally, the speed of dehumidification can be affected by these layers and divisions.
To accurately determine the drying time for a specific PCB, it is recommended to conduct a PCB-specific dehumidification test. This test takes into account the unique characteristics and requirements of the PCB, ensuring that the drying time is accurately assessed.