When choosing a moisture barrier bag there are two main specifications you need to consider, the puncture resistance and the Moisture Vapour Transmission Rate (MVTR). The lower the MVTR the more effective the bag is at preventing water vapour from being transmitted. It is the Foil, high barrier bags (Dri-Shield® series 3000, 3400 and 3700) that have the lowest MVTR, and that meet IPC/JEDECJ-STD-033 requirements. The puncture strength or resistance captures the maximum pressure the bag film can with stand before puncturing. Puncture strength is measured in pounds.

Most manufacturers of Moisture Sensitive Devices (MSD) will dictate how their product should be stored, shipped, etc.  However, the IPC/JEDECJ-STD-033C standard describes the standardised levels of floor life exposure for moisture/reflow-sensitive SMD packages along with the handling, packaging, and shipping requirements necessary to avoid moisture/reflow-related failures.

For help in selecting the right Moisture Barrier Bag for your application, visit our selection guide.

While there is no direct link between protection from ESD and protection from moisture, many devices and components require protection from both. Surface Mounted Devices (SMDs), for example, absorb moisture and then during solder re-flow operations, the rapid rise in temperature causes the moisture to expand and the delaminating of internal package interfaces, also known as “pop corning.” The result is either a circuit board assembly that will fail testing or can prematurely fail in the field.

Desco Europe’s Humidity Indicator Cards (HIC) are printed with moisture sensitive spots which change colour from blue to pink, or brown to yellow, when exposed to a relative humidity level. The HIC is typically used with Desiccant inside a Moisture Barrier Bag to protect static and moisture sensitive components noting the highest relative humidity level exposure. Our SCS brand manufactures Moisture Barrier Bags with different laminates having different moisture vapour transmission rates. SCS Dri-Shield® bags are designed to be used with Desiccant and a HIC for packaging surface mount devices (SMD) trays and reels. The bags are sealed, including being vacuum sealed, containing the SMD, or other content, along with the Desiccant and selected HIC. The HIC will note the highest relative humidity exposure, so the user can determine if baking the devices is required. Desco Europe recommends the user follow procedures defined in IPC/JEDEC J-STD-033.

In addition, a Moisture Sensitive Level (MSL) label is used to tell you how long the devices can stay outside the bag before they should be soldered onto the board. This label is applied to the outside of the bag. If the “level” box is blank, look on the barcode label nearby.