The significance of cleaning printed circuit boards (PCBs) lies in removing residual conductive particles, flux, dust, and other contaminants to achieve insulation performance. This helps prevent poor contact, avoid defects during continuity testing, and mitigate corrosion. Therefore, the evaluation of PCB cleaning effects is crucial as it directly impacts the quality of the PCB after cleaning. Here are several key points for assessing the effects of PCB board cleaning:
- Reliability Assessment: It is essential to evaluate the reliability of PCBs after introducing cleaning processes and equipment. Conduct insulation resistance tests and accelerated aging experiments using experimental PCBs to assess reliability. Accelerated aging experiments can be conducted in natural environmental conditions using pressure furnaces.
- Impact on Electronic Components: Different electronic components may react differently to cleaning agents. Conduct cleaning experiments using various experimental components or materials to assess compatibility beforehand. Resin-based electronic components may experience discoloration, expansion, or issues like text fading and water ingress. During the drying phase using hot air, verify the surface temperature distribution of electronic components due to thermal stress.
When determining the specific specifications of each cleaning process, it is essential to conduct a comprehensive evaluation of the above issues. Common evaluation methods include:
- Visual Inspection: Direct visual inspection, microscopic inspection, or UV inspection to observe and identify foreign objects on the PCB.
- Ion Residue Acquisition Experiment: Use dynamic or washing methods to acquire ion residues, with equipment such as ion radiation cameras or ohmmeters. Evaluation of assembled board quality is often based on the USA military standard MIL-P-28809.
- Electrical Inspection: Conduct insulation resistance and continuity tests, referring to industrial standards such as JISC5012 in Japan.
- Humidity Resistance Test: Conduct environmental experiments including constant tests, cyclic tests, and pressure cooker tests.
- Solvent Resistance Test for Electronic Components: Assess component compatibility and print strength by conducting cleaning under specified conditions, evaluating issues such as color fading, bubbling, and character fading during printing or character printing.
These are the key points for assessing the effects of PCB board cleaning. I hope this helps.