Gideon Analytical Laboratories received three central air conditioner hubs. These air conditioners can are built for commercial or residential use. Depending on their SEER ratings, they run between 66dB and 72dB and use Puron refrigerant. The hubs had corrosion on the PCB and had the appearance that some liquid flowing between the insulation and wire leading into the cavity. The goal was to discover the identity and cause of the corrosion.
Each PCB was corroded with a liquid that came out of the wire insulation, as shown in the picture at the top left. There were several locations where corrosion occurred, but always around the incoming wires. It was thought that we could remove the insulation from the wire and analyze the residual liquid next to the wire. Upon doing this, only a slightly brown residue was found, as pictured at the top right. FTIR and SEM-EDS analysis of the residue was initiated.
The analysis was carried out using FTIR with a high sensitivity MCT detector. Both the FTIR and SEM-EDS analysis both support the substance was water-soluble and entered via the wire insulation. The actual liquid medium has long since evaporated on all wires. All that could be analyzed is the residual solids under the insulation. The two elements presented by the SEM-EDS are magnesium and sulfur. The magnesium would suggest the fluid and solids are water-soluble. The by-product is most likely lead sulfate with small areas of copper sulfate. The FTIR would suggest a chemical called Flex Bond, an organic in a variety of industrial products. The FTIR also indicates the presence of ammonium salts, which are ubiquitous in cleaning products. Final analysis indicates the corrosion is a water-soluble fluid from an external source entering the cavity of the electronics by the sleeve of the wire. It is not amicable with the PCB process or operation and causes corrosion upon exposure.
With failure analysis performed by Gideon Analytical Laboratories, electronics companies can be informed of the cause and nature of failures. Gideon Analytical Laboratories has been solving problems and identifying causes of failure for over two decades. The goal has always been to provide companies with accurate and candid results that will help them better plan for their future in the industry.