Moisture Barrier Bags for MSDs - what matters most?
Moisture barrier bags (MBB) protect moisture sensitive devices (MSDs) from water vapour and static discharge. This guide explains the barrier film construction, the role of desiccant and humidity indicator card, and floor life under IPC/JEDEC J-STD-033.
View moisture barrier bagsHow is a moisture barrier bag built?
A moisture barrier bag is a multi-layer laminate of plastic and an aluminium or metallised barrier layer. This film blocks water vapour and at the same time dissipates static charge, so MSD components stay dry and ESD protected.
The key figure is the water vapour transmission rate (WVTR). High quality MBB films to EIA-583 stay well below 0.02 g/m² per day and thus keep their barrier effect for months, provided the bag is sealed correctly.
- Outer layer (PET): mechanical protection and printability.
- Middle aluminium or metallised layer: the actual water vapour and light barrier.
- Inner layer (PE): heat sealable and dissipative for ESD protection.
- Static dissipative surface with resistance in the 10⁶ to 10¹¹ Ω range.
What do the desiccant and indicator card do?
A sealed bag always needs a desiccant and a humidity indicator card. The desiccant absorbs the trapped residual moisture, while the indicator card makes the actual relative humidity inside the bag visible.
The required amount of desiccant is measured in units based on the bag area and barrier quality. One silica gel bag corresponds to a defined adsorption capacity; too little desiccant lets the humidity slowly rise again.
- Remove the desiccant from its barrier pack only just before sealing.
- Place the indicator card clearly visible against the inner wall.
- After closing, press out the air or vacuum-seal the bag.
What does floor life to J-STD-033 mean?
Floor life is the time an MSD component may stay outside the barrier bag in a typical factory environment (30 °C / 60 % RH) after opening, before it must be soldered. It depends on the Moisture Sensitivity Level (MSL) per J-STD-020 and is governed by J-STD-033.
If floor life is exceeded or the indicator card reads moist, the components must be dried (baked) per J-STD-033, for example at 125 °C for parts on heat resistant carriers. Only then is reflow soldering safe again, without the risk of delamination or the popcorn effect.
Frequently asked questions
What is a moisture barrier bag for?
It keeps water vapour away from moisture sensitive devices (MSDs) and also protects them from static discharge. That keeps the components dry and solderable until processing.
Do I always need a desiccant and indicator card?
Yes. The desiccant absorbs the trapped residual moisture and the indicator card shows the actual relative humidity. Without both you cannot verify dryness inside the bag.
What is floor life?
The time an MSD component may stay outside the barrier bag after opening before it must be soldered. It is set by the MSL and defined in J-STD-033.
What if the indicator card reads moist?
The components may be over-exposed and must be baked per J-STD-033 before reflow soldering, to avoid the popcorn effect during heating.
Looking for moisture barrier bags and accessories?
We supply MBB bags to EIA-583, matching desiccant and humidity indicator cards for handling MSD components to J-STD-033.
Tested barrier
MBB films to EIA-583 with low WVTR.
Packed dry
Desiccant and indicator card included.
Standard compliant
Handling to IPC/JEDEC J-STD-033.
Expert advice
ESD specialists help with the selection.