Immersion Silver Storage and Handling
Printed circuit boards that are coated with immersion silver must be handled with care and stored properly. The shelf life of immersion silver is typically 12 months. Properly stored boards protected from the environment can far exceed that limit. The following considerations must be taken into account in order to preserve the solderability of the finish.
- Apply immersion silver as a last operation. Boards are removed from the process panel and processed through the immersion silver process in piece or pallet form. The finish dried, inspected and packaged as soon as possible. This minimizes prolonged exposure to the environment. The potential of handling damage from the manufacturing process is also minimized.
- Package the boards properly. Slip sheet boards with sulfur free and ph neutral paper. Slip sheet in between boards stacked together. Place a slip sheet on the top and bottom of the stack. Shrink wrap the stack in a way that eliminates contact to the environment. The plastic shrink wrap used should have moisture barrier properties.
- Properly packaged boards can be stored in environments below 35°C (95°F) and 85% R.H. Lower would be better.
- Do not use desiccant when storing the product! Desiccant can contain sulfur bearing compounds that shall attack the immersion silver finish.
- Avoid tape, sticky labels and rubber bands. These items are also sources of sulfur bearing compounds.
- Unpacked boards shall only be handled when wearing non-fibrous gloves. Keep the skin from coming into contact with the product. Oils, creams and moisture from the hands must be prevented from coming into contact with the immersion silver surface.
- Unassembled boards must be immediately repackaged to minimize exposure to the environment.