Greg Barron, Actum Group director

To protect PCBs from both ESD and moisture, they should be stored in a vacuum-sealed moisture barrier bag. To complete a dry-packaging system, desiccant packs and humidity indicator cards should be used in addition for best storage conditions.

Steps to a dry-packaging system:

1. Moisture barrier bags work by enclosing a device with a metal or plastic shield that keeps moisture vapour from getting inside. These bags have specialised layers of film that control the moisture vapour transfer rate. The bag also provides static shielding protection.

2. Desiccants are drying agents which are packaged inside a porous pouch so that the moisture can get through and be absorbed by the desiccant. They absorb humidity from the air still inside the barrier bag after it has been sealed and moisture that subsequently penetrates the bag. The desiccant remains dry to the touch even when it is fully saturated with moisture vapour.

3. Humidity indicator cards (HIC) are printed with moisture-sensitive spots which respond to various levels of humidity with a visible colour change, from blue to pink or yellow to brown. The humidity inside barrier bags can be monitored by the HIC inside. Examining the card when you open the bag will indicate the humidity level the components are experiencing so the user can determine if baking the devices is required.

For more information contact Actum Group on +27 11 608 3001 or email: [email protected]

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