CHAPTER 3 SOLDERING CONDITIONS
3.2 Heat Resistance
3.2.2 Package Moisture Absorption
| (1) Absorption control standard settings |
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The plastic package is made of epoxy-based mold resin. Because the molecules of this epoxy resin are coarse, the package absorbs a small amount of moisture contained in are if it is stored at room temperature. Figures 3-2-2 and 3-2-3 show examples of the moisture absorption behavior. These figures indicate that a thin type SMD absorbs moisture up to 0.36% when it is stored outdoors, and up to 0.27% when stored indoors (in Tokyo).
The maximum moisture absorption when the sample is stored outdoors is equivalent to a saturated absorption rate at about 30°C, 75%RH, and that when the sample is stored indoors is equivalent to a saturated absorption rate at about 25°C, 65%RH.
The maximum value was observed in summer when the temperature and humidity rise, and the minimum value was recorded in winter when the temperature drops. |
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Based on these data, NEC Electronics specifies the moisture processing test conditions as fellows.
- the products for which moisture control is unnecessary ...... 30°C, 85%RH *
- the products for which moisture control is necessary .......... 30°C, 70%RH
(Both conditions are determined by taking into consideration areas where temperature and humidity are high.)
| *: |
Because it takes a long time to test under conditions of 30°C, 85%RH, the test time is shortened by actually conducting an equivalent test at 85°C, 85%RH so that the same amount of moisture is absorbed. |
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| Figure 3-2-2. Moisture Absorption Behavior of Package Stored Outdoors for One Year |
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| Figure 3-2-3. Moisture Absorption Behavior of Package Stored Indoors for One Year |