Cleaning and coating of PCB's
Recently, there has been a major increase in the demand for more complex assembly including the coating of printed circuit boards (larger) components. Combined with the increasing batch sizes, this requires a new approach centered around an automated coating operation. This is especially true for our ATEX projects related shipping and petrochemicals.
There is a video on YouTube that gives a further explanation of the process.
HumiSeal UV40-250 is the standard material we use to industrially coat electronic assemblies. It is UL certified and RoHS and IPC-CC-830 compliant. The decision to use this material was made after extensive research and benchmarking. The high degree of elasticity, strength and the UL label were important aspects affecting our choice. The eventual choice of the right coating, potting (casting) process depends on having an accurate picture of the application and climatic conditions in the field. Only when all this information is available can suppliers be contacted and asked about their experiences with the various coating/ potting methods and materials, based on their extensive testing. It is important to indicate that coating is required when the assembly application is made.
The specification of the substrate specifies the desired value of the surface tension. When HEAD receives the PCB, during the incoming goods reception process the surface tension of the solder mask is checked to ensure quality. It is also recommended that the design should take into account the fact that the PCB will be coated. The needle / head of the machine must have sufficient room to create protective dams. The absorption of some connectors make them extremely sensitive to the coating material so that if the material contaminates them they can be useless.
For an optimum coating process, a perfectly clean PCB is essential. Therefore HEAD has invested in a Miele IR6002 special cleaner for printed circuit boards. We chose the detergent we use based on tests which took place at Zestron in Switzerland. It is important to note that not every component on the PCB is able to withstand the washing process (some spools, batteries, etc.). We also know that silicone on the board negatively affects the quality of the covering (dewetting) and that it is not a solution to wash the board.
Therefore, it is highly recommended to, together, test the coating.