When manufacturing/assembling PCBs
, several residues may remain on the board, posing threat to the efficiency and durability of the final assembly. IPC (the Association Connecting Electronics Industries) has proposed several guidelines that guide you clean PCBs efficiently.
Types of Contaminants
IPC lists several contaminants that affect the performance and service life of PCBs. According to IPC, the following contaminants must be removed from the board, utilizing cleaning techniques that are safe to workers and are environmentally sustainable.
- Polar Residues – Etching materials, solder flux constituents, chemicals from substrates, among others.
- Non-Polar Water Soluble Residues – Soldering oils and waxes
- Nonpolar Water Insoluble Residues – SMT adhesives, synthetic resins, greases, and release agents.
- Insoluble Residues – Silica and clay type fillers and glass fiber from the laminate.
- No reflowed Solder Paste
- Reflowed Flux Residue
- Uncured (Wet) SMT Adhesive
IPC Recommendations to Cleaning Residues
Consider the following when cleaning PCBs.
- Ensure to clean both sides of the PCBs. This is important, especially when using a spray-in air cleaning system.
- Use a spray-in air cleaning system which is equipped with a filter. This helps remove fine particles from the cleaning solution, enhancing the quality of the cleaning process.
- When cleaning inner electrical components, ensure that the rinse pressure and duration is properly maintained for a thorough cleaning.
- Correct positioning and firm holding of PCB is mandatory throughout the cleaning process. This smoothens the cleaning process, while not damaging PCB components due to any tremble or vibration.
- Cleaning systems that use ultrasonic technology must have ultrasonic frequency of 40 kHz or higher to ensure effective cleaning.
- Ensure that there are no adhesive residues on lands or in via holes. Via holes are one of the hard to reach places, where cleaning must be carried out carefully.
Debris can hamper the operational excellence and efficiency of PCBs. Also, messiness in the PCB will lead to its malfunction in the near future. Hence, IPC strongly emphasis on the need of cleaning PCBs, whilst not damaging them during the process. You can follow manual or bench top cleaning, ultrasonic and batch immersion cleaning, and spray-in-air cleaning method. However the selection of the cleaning process must be depended on the kind of the PCB materials, assembly process used, and types of components installed.