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How to analyze and restore storm-damaged boards.

Hurricane Katrina subjected many large and hard-to-replace circuit card assemblies to severely adverse conditions. For one particular company, thousands of boards were submerged in standing water with heavy contaminants. Even though this company had plans in place to ultimately replace the aging systems, the newer units were still in the design phase at the time of the disaster and not ready to be implemented as replacements. The company opted to salvage and repair the existing systems.

The process flow diagram (Figure 1) determined what cleaning process would be applied to a given piece of hardware, depending on the type of board, its components and the level of contamination. Boards were unpacked from their boxes and antistatic bags, then placed in trays on a multitude of racks. The bags and desiccant were discarded due to contamination. New antistatic bags were ordered that would accommodate even larger boards, if necessary. New desiccant was also acquired to be used within each new bag. Repackaging procedures followed new product standards.

All boards were then inspected by a technician for levels of particulate matter, process compatibility and to assess whether the boards were recoverable. The history of each board's storage and exposure conditions was evaluated, with a focus on original date of manufacture and time in storage. Severity of exposure, storage location (e.g., in crates at the floor level, shelved above the water line, etc.) and any processing or recovery operations performed after exposure to the conditions created by the storm were also examined (Figure 2).

Most small boards were immediately sent to Cleaning (I). These boards were lightly contaminated and did not have special components. Clean DI water at 130°F in an inline aqueous cleaning system was used with a saponifier.

Many boards went to a Disassembly and Component Removal phase, in which all socketed components were removed. When corrosion was severe on the leads, this ensured that contaminants were cleaned from within the socket. All daughtercards were removed, for the same reason. Other components were also removed and separated, including paper insulators, all ICs, displays and batteries.

Boards and components that were heavily contaminated went to a Pre-wash (II) phase to remove particulates. Boards were soaked for several minutes, lightly brushed and then rinsed in cleaner baths of solution. Afterward, the boards went to Cleaning (Figure 3).

Boards underwent 100% visual inspection for cleanliness. Every 100th board underwent ionic cleanliness testing using resistivity of solvent extract (ROSE), with the maximum requirement of 10.06 µg of NaCl equivalents/in². All boards were then baked dry at 60°C for 8 hrs.

Boards then went to Component Reassembly. Socketed components and daughtercards that were removed and separately cleaned were reinstalled in accordance with customer-supplied documents. The boards were then packed in new bags with fresh desiccant, and shipped priority to the customer for further reassembly and testing at its facility.

The American Competitiveness Institute (aciusa.org) is a scientific research corporation dedicated to the advancement of electronics manufacturing processes and materials for the Department of Defense and industry. This column appears monthly.