Why Use Desiccants with Moisture Barrier Bags?

What is Desiccant?



Desiccant is a drying agent that is used to absorb moisture from the air inside moisture barrier bags. Desiccant absorbs moisture vapor (humidity) from the air left inside that barrier bag after is has been sealed. Any moisture that penetrates the bag will also be absorbed. Desiccant remains dry to the touch even when it is fully saturated with moisture vapor.

Why are Electronics Moisture Sensitive?


Certain kinds of electronic devices called “Surface Mount Devices” or SMD’s are mounted on a circuit card by high temperature soldering. The body of the SMD is made from plastic that absorbs moisture from the air. When the case is heated during soldering, the moisture inside turns to steam and may break the device as the steam escapes. Keeping SMD’s dry before soldering means that the devices will not be damaged.

How is Desiccant Purchased?

Desiccant is sold by the “Unit” or fractional Unit. One unit of desiccant will absorb a specific amount of moisture. A unit weighs about 28 grams or 1 ounce. The pouches of desiccant are placed into metal pails to keep the desiccant dry during shipping and storage.

How is Desiccant Packaged?

Desiccant is packaged in small sealed pouches made from a white plastic called “Tyvek”, or brown “Kraft” paper. Tyvek pouches are very clean and sulfur free. Kraft pouches are economical.

How Much Desiccant Do I Need?

Method 1 (per MIL-P-116)

1. Formula: Unit = 0.011 x bag area in square inches

2. Example: 10″ x 20″ barrier bag

3. Find Bag Area: 10″ x 20″ x 2″ sides = 400 sqin

4. Apply Formula: Units = 0.011 x 400 sqin = 4.4

Use 4.5 Units of desiccant

Method 2 (per EIA 583. This formula allows you to tailor the desiccant to your specific needs)

What do you need to know?

Bag area, Bag MVTR, Months of Storage, Maximum Interior Humidity (MIH)


Units = 0.231 x Bag Area x Bag MVTR x Months divided by Moisture Capacity


For a 10″ x 20″ bag with a 0.02 MVTR, a 12 month storage time and a MIH of 20%

Apply formula Units =

0.231 x 400 sqin x 0.02 MVTR x 12 divided by 4.8g / unit = 4.6

Use 4.5 Units of Desiccant

Moisture Capacity

10% MIH: 3.0 g/unit

20 MIH: 4.8 g/unit

30% MIH: 5.8 g/unit

40% MIH: 6.2/unit

For more information on desiccant packs and moisture barrier bags, visit ProtektivePak.com





About Protektive Pak

Protektive Pak is a leading manufacturer of ESD Material Handling and Packaging solutions. We offer a complete line of ESD Packaging products for transporting, storing and shipping of static sensitive assemblies. Our products include Storage Containers, Circuit Board Shippers, Open Bin boxes, Reel Storage Containers, Trays, Foam, Tape, Shielding Bags and much more! We also have custom manufacturing capabilities to your meet your special needs, including Thermoforming requirements. Protektive Pak offers a unique “Impregnated” corrugated material that provides greater durability than “painted” corrugated material. The buried shielding layer protects ESD sensitive items (ESDS) and minimizes sloughing and rub-off contamination. We also offer Plastek Industrial Fluted Plastic, an economical alternative to injection molded products and ideal for use where corrugated and /or paper products cannot be used. For further information, please visit our website at www.ProtektivePak.com

Posted on February 16, 2016, in Articles, Desiccant, Moisture Barrier Bags, Uncategorized and tagged , , . Bookmark the permalink. Leave a comment.

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