Humidity control is a frequently underestimated but critical aspect in electronics manufacturing of PCB design services, encompassing precise soldering and corrosion prevention tasks. Excessive moisture in the assembly environment may result in problems such as corrosion, while insufficient moisture can elevate the susceptibility to electrostatic discharge (ESD). Manufacturers are responsible for maintaining humidity within specific ranges stipulated by various industry standards.
Hence, it is essential to consider the ideal humidity level for your PCB design, and the following guidelines briefly explain how humidity level impacts effectively on PCB assembly.
How Humidity Level Impacts On PCB Assembly?
If the humidity level during PCB assembly changes from optimal levels, various issues can arise at different stages of the assembly process.
Electrostatic Discharge (ESI):
A significant issue linked to moisture levels in electronics manufacturing of PCB after you utilize a PCB layout services for your design is Electrostatic Discharge (ESD). ESD incidents are influenced by the humidity level in the surrounding air and the resultant of discharge current and electric field. Lower humidity environments pose a higher risk of ESD. It is advisable to ensure the humidity remains at or above 30% to mitigate the risk of ESD when handling assembled PCBs and components.
Impacts On Soldering:
Soldering rework can be challenging under varying humidity conditions. For instance, excessive humidity can result in the infiltration of solder paste, leading to incomplete soldering and residual paste left behind during standard reflow processes. Ideally, the environment where solder paste is applied should maintain a humidity level between 40% and 50% and temperatures of 65 to 75 °F. While these values are suitable for temperate zones, regions with arid or tropical climates may experience significant deviations from these parameters.
Condensation:
Condensation poses no issue when there are no moisture-sensitive components involved. However, if the condensation persists on the circuit board upon activation, it could trigger electrochemical processes, potentially resulting in corrosion. This corrosion tends to manifest on surface pads exposed to the surroundings, and it is particularly problematic in regions with closely spaced pads where voltage disparities might occur upon powering the device.
Moisture Sensitivity Level (MSL):
As mentioned, specific components come with a Moisture Sensitivity Level (MSL) rating. MSL ratings are determined by the duration of exposure to a humid environment and are not necessarily contingent on a specific humidity level. Moisture-sensitive components typically permit exposure to relative humidity levels of 40% to 60% in temperate climates without reducing allowable exposure time. Sunstream’s component engineering services has the capability of identifying MSL rating of all components used in your BoM.
Packaging & Storage:
While the design may successfully navigate the assembly process without any issues related to excessive moisture, it is essential to ensure that the assembled PCBs are appropriately packaged and stored to avoid excess humidity infiltration. By securely packing them with desiccants such as silica gel and storing them in a dry environment, the assembled PCBs can have an extended shelf life before further processing or being dispatched to a customer.
If you’re dealing with designs sensitive to moisture and requiring specific handling guidelines during assembly, crafting your design data package using OrCAD PCB designer is essential. Approach Sunstream, as we provide a complete circuit, IC, and PCB design tools suitable for various applications and complexities of your design needs.
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