3MTM Desiccant
Desiccant in Plastic or Kraft Paper Pouch
DESICCANT, PLASTIC OR KRAFT POUCH
ITEM NUMBER
SEE PAGE
1
1110-H
DATASHEET
PRODUCT
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PRODUCT
DATA
SHEET
Page 2
Calculating Desiccant Loading
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 the barrier
bag after it has been sealed. Moisture that penetrates the bag will also be absorbed. Desiccant remains dry to the touch even when it is fully saturated with moisture vapor.
How much Desiccant do I need?
Desiccant is sold by the “Unit” or fractional Unit, or in grams. One unit of desiccant will absorb a specific amount of moisture. A unit weighs about 33 grams. There are several standards for calculating the desiccant
loading for bags. Each standard is for a specific application, and requires different amounts of desiccant for the same bag size. You must determine which standard most closely matches your particular application, if
any, and apply the appropriate formula, or ask your 3M representative for our spreadsheet Desiccant Calculator.
Why are electronic devices 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 helps prevent the devices from being damaged.
MIL-P-116
Application:
General dry packaging.
What You Need Know:
Bag Size
Formula:
Units = 0.011 x Bag Area in square inches.
Example:
8” x 10” inch Barrier Bag
Find Bag Area:
8” x 10” x 2 sides =160 sqin.
Apply Formula:
Units = 0.011 x 160 sqin = 1.8
Use 2 Units of desiccant.
IPC/JEDEC J-STD-033
Application:
Dry packaging for SMD’s.
What You Need Know:
Bag Size, Bag MVTR, Storage Time in Months.
Formula:
Units=
0.304 x Months x Bag MVTR x Bag Area
Moisture Capacity
Example:
8” x 10” inch Barrier Bag, with a 0.002 MVTR and a
12 month storage time.
Find Bag Area:
8” x 10” x 2 sides =160 sqin.
Apply Formula:
Units=
0.304 x 160 sqin x 0.002 MVTR x 12 months
6.6667 g/unit
Units = .2
Use 1/6 unit of Desiccant.
EIA 583
Application:
Dry packaging for SMD’s. Allows adjustment of environmental conditions.
What You Need Know:
Bag Area, Bag MVTR, Months of Storage, Maximum Interior Humidity
(MIH).
Formula:
Units=
0.231 x Bag Area x Bag MVTR x Months
Moisture Capacity
Example:
8” x 10” inch Barrier Bag, with a 0.02 MVTR, a 12 month storage time, and
a MIH of 20%.
Find Bag Area:
8” x 10” x 2 sides =160 sqin.
Select Moisture Capacity based on MIH:
10% MIH: 3.0 g/unit 20% MIH 4.8 g/unit 30% MIH 5.8 g/unit 40% MIH 6.2 g/unit
Apply Formula:
Units=
0.231 x 160 sqin x 0.02 MVTR x 12 months
4.8 g/unit
Units = 1.8 units
Use 2 units of desiccant.