All PCBs should be stored in a moisture barrier bag (MBB) that’s vacuum sealed. In addition to the luggage, Desiccant Packs and Dampness Indicator Cards must be used for proper dampness protection. This ‘package’ is also known as a dry package.
Most manufacturers of the Moisture Very sensitive Devices (MSD) will determine how their product should be stored, shipped, etc . However, the IPC/JEDEC J-STD-033B standard describes the standard levels of floor life exposure for moisture/reflow-sensitive SMD packages along with the handling, packing and shipping and delivery requirements necessary to avoid moisture/reflow-related failures. The ESD Handbook ESD TR20. 20 mentions the significance of humidity barrier bags in area 5. 4. 3. 2 . not 2 Temperature: “While only specialized materials and buildings can control the interior temperature of a package, it is important to take possible temperature direct exposure into account when shipping electronic parts. It is especially important to think about what happens to the interior of a package if the environment has high humidity. If the temperature varies across the dew point of the established inside environment of the bundle, condensation may occur. The interior of a package should either contain desiccant or the air should be evacuated from the bundle during the sealing process. The package itself needs to have a low WVTR. ”
Aspects of a dry package deal
A dry package has four parts:
1. Humidity Barrier Bag (MBB)
3. Humidity Indicator Card (HIC)
4. Humidity Sensitive Label (MSL)
Humidity Barrier Bag (MBB)
Moisture Barrier Bags (MBB) work by enclosing a device with a metal or plastic shield that keep moisture vapour from getting inside the bag. They will have specialised layers of film that control the Moisture Vapour Transfer Level (MVTR). The bag also provides static shielding safety.
Desiccant is a drying agent which is packaged inside a porous pouch so that the moisture can get through the pouch and be absorb by the desiccant. Desiccant absorbs moisture vapour (humidity) from the air left inside the buffer bag after it has been closed. Moisture that penetrates the bag will also be absorbed. Desiccant remains dried out to the touch even when it is fully saturated with moisture vapour. The suggested amount of desiccant is dependent on the internal area of the handbag used. Use thisdesiccant calculator to determine the minimum amounts of desiccant for use with Moisture Barrier Bags.
Moisture Indicator Cards (HICs)
Humidity Indicator Cards (HICs) are printed with moisture delicate spots which respond to various levels of humidity with a noticeable color change from blue to pink. The humidity inside barrier bags can be monitored by the HIC inside. Examining the credit 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.
The Moisture Very sensitive Level (MSL) label informs you how long the devices can stay outside the bag before they should be soldered onto the board. This label is put on the outside of the bag. If the “level” box is blank, look on the barcode tag nearby.
The Moisture Very sensitive Level (MSL) label