Issue link: https://iconnect007.uberflip.com/i/1537054
JULY 2025 I SMT007 MAGAZINE 45 T H E K N OW L E D G E BAS E (if available) and confirm that drying cycles are long enough to remove water from under components. Validate and monitor. Process validation tools include: • SIR testing (for process validation and IPC- required objective evidence) • Resistivity of solvent extract (ROSE) testing (for IPC-required process monitoring) • Visual inspection • In situ rinse water resistivity measurement With the new IPC J-STD-001J, manufacturers are now expected to produce objective evidence of cleanliness via surface insulation resistance (SIR) testing and process monitoring via ionic contamina- tion (ROSE) testing, not just pass a test at the end. Coating Best Practices: Seal the Deal Once a board is clean, it's ready to be coated. But that doesn't mean the hard part is over. Pick the right coating. Each material has trade-offs: • Acrylics: Easy to apply and rework, but permeable • Urethanes: Tougher, more chemical resistant • Silicones: High temperature, moisture resistant • Parylenes: Best barrier, vacuum deposited, expensive Base your choice on the actual environment the assembly will face, not just what's on the datasheet. Control the environment. Apply coatings in a clean, controlled area. Dust, oils, and humidity can all interfere with adhe- sion and create defects. Apply correctly. Spray, dip, brush, or vapor-deposit: each method has pros and cons. Robotic selective spray systems provide precision and repeatability. What- ever the method, ensure: • Proper thickness (typically 25–75 µm) • Full coverage without bridging or voids • Avoidance of trapped air and bubbles Cure thoroughly. Some coatings air-dry. Others require heat or UV. Incomplete cure means incomplete protec- tion. Always follow the material specs and confirm final properties through testing. Clean and Coat: When You Need Both There are environments where cleaning alone might suffice. But when the stakes are high, when you're building for aerospace, defense, automo- tive, industrial controls, or mission-critical con- sumer devices, you don't want to guess. You clean to eliminate the root causes of failure. You coat to protect against what's coming. Together, they provide layered protection. Alone, they may leave gaps. A Word on Standards If you haven't already studied the latest changes in section 8 of IPC J-STD-001J, it's time. The industry has moved away from legacy subjective "pass/fail" cleanliness limits and toward objective evidence and process monitoring. That means manufactur- ers need to understand their cleaning process in a far more detailed way than ever before. Likewise, IPC-CC-830 and IPC-HDBK-830 pro- vide critical guidance on coating material perfor- mance, inspection criteria, and defect prevention. 6 1 2 3 4