GB/T 4937.20-2018Semiconductor devices -- Mechanical and climatic test methods -- Part 20: Resistance of plastic encapsulated SMDs to the combined effect of moisture and soldering heat (English PDF)

4.1 Damp heat test chamber

The damp heat test chamber shall be capable of providing a temperature and relative humidity environment as specified in 5.3.

4.2 Reflow soldering equipment

The temperature profile provided by the infrared convection and gas phase reflow equipment shall be capable of complying with the welding heat conditions specified in 5.4.2 and 5.4.3. again

The temperature setting of the flow soldering equipment should be set according to the temperature curve, which refers to the surface temperature of the sample during the welding heat test, and the measuring method

As shown in Figure 1.

Note. Adhesives or thin tapes have good thermal conductivity.

Figure 1 Sample temperature curve measurement method

4.3 substrate

Except as otherwise provided in the relevant documents, any sheet, such as glass fiber or polyimide, can be used as the substrate. Use a conventional method to solidify the sample

Set on the substrate, as shown in Figure 1. If the shape of the sample terminal is changed according to Figure 1, and the electrical parameters are abnormal, it should be selected.

Choose the assembly method that avoids the shape change of the leading end and specify it in the relevant documents.

4.4 Wave soldering equipment

Wave soldering equipment shall meet the conditions specified in 5.4.4. Generally, molten solder should be able to flow.

4.5 Solvents for gas phase reflow soldering

Full fluorocarbons should be used.

4.6 Flux

Flux consists of 25% ethanol and 75% isopropanol, as specified in the relevant documents. See IEC 60068 for details.

2-20. Provisions of Appendix B of.2008.

4.7 solder

The solder composition specified in Table 1 of IEC 60068-2-20.2008 is used.

5.1 Initial test

5.1.1 Visual inspection

Before the test, the visual inspection shall be carried out under a 40-fold microscope in accordance with the provisions of IEC 60749-3, and special attention shall be paid to the cracks on the outer surface.

Drum kit.

5.1.2 Electrical test

Electrical performance tests shall be performed when required by relevant documents.

5.1.3 Acoustic scanning internal inspection

Unless otherwise specified in the relevant documents, the internal cracks of the sample are examined using an acoustic scanning microscope in accordance with IEC 60749-35.

Layered.

5.2 Drying

Samples shall be baked at 125 ° C +/- 5 ° C for at least 24 h, unless otherwise specified in the relevant documentation.

5.3 Water vapor impregnation

5.3.1 General requirements

Unless otherwise specified in the relevant documents, the conditions of water vapor impregnation should be selected according to the packaging method of the sample (see A.1.1). If related text

The sample is specified to be baked before welding, and the sample is directly baked without water vapor impregnation.

5.3.2 SMD test conditions for non-dry packaging

The water vapor impregnation conditions shall be selected from Table 1 in accordance with the actual allowable limit storage conditions (see A.1.2.1).

Table 1 Water vapor immersion conditions of non-dry packaging SMD

condition

temperature

Relative humidity

duration

Actual allowable limit storage

A1 or B1 85+/-2 85+/-5 168+/-24 < 30°C, 85% RH

Note. Conditions A1 and B1 are SMD water vapor impregnation conditions for non-dry packaging in Method A or Method B.

5.3.3 Dry packaging of SMD water vapor impregnation

5.3.3.1 General requirements

The SMD water vapor immersion conditions of the dry package are shown in Table 2 or Table 3. Dry-packed SMD water vapor impregnation involves two steps. step one

Is to simulate the wet condition of SMD before opening the dry packaging or drying the locker; the second step is to simulate the SMD to open the package to the welding period.

Wet conditions. The SMD water vapor impregnation conditions for dry packaging should be selected from Method A or Method B. When the contractor specifies the SMD drying package

When the relative humidity in the installed or dried locker is between 10% and 30%, select Method A and select Method B when the relative humidity is less than 10%.

5.3.3.2 Method A

Except as otherwise provided in the relevant documents, the first step of condition A2 in Table 2 shall be carried out first, and then the table shall be carried out within 4 hours after the completion of step one.

Step 2 of Condition A2 in 2 (see A.1.2.2).

The relative humidity condition of step one should be consistent with the upper limit of the relative humidity in the moisture barrier bag. The relative humidity of step 2 should be related to the life of the workshop.

The pieces are consistent.

Water vapor immersion conditions other than moisture storage bag storage and workshop life are specified in Table 2, and other test conditions need to be relevant.

As stated in the document.

Table 2 SMD water vapor immersion conditions for dry packaging (Method A)

Conditional water vapor impregnation conditions

Dry packaging and drying lockers

Allowable storage conditions

Workshop life conditions

A2 step one condition

(85+/-2) °C, (30+/-5)% RH

168 24-0h

5.3.3.3 Method B

The conditions for water vapor impregnation shall be selected from Table 3 and shall be consistent with the workshop life conditions specified in the relevant documents (see A.1.2.3).

Table 3 SMD water vapor immersion conditions for dry packaging (Method B)

Conditional water vapor impregnation conditions

From baking to dry packaging and drying

Packaging conditions for short opening

Workshop life conditions

B2

(85+/-2) °C, (60+/-5)% RH,

168 24-24h

< 30 ° C, 60% RH, 24 h < 30 ° C, 60% RH, 1 year

B2a

(30+/-2) °C, (60+/-5)% RH,

696 24-24h

< 30 ° C, 60% RH, 24 h < 30 ° C, 60% RH, 28d

B3

(30+/-2) °C, (60+/-5)% RH,

192 24-0h

< 30°C, 60% RH, 24h < 30°C, 60% RH, 168h

B4

(30+/-2) °C, (60+/-5)% RH,

96 24-0h

< 30 ° C, 60% RH, 24 h < 30 ° C, 60% RH, 72 h

B5

(30+/-2) °C, (60+/-5)% RH,

72 24-0h

< 30 ° C, 60% RH, 24 h < 30 ° C, 60% RH, 48 h

B5a

(30+/-2) °C, (60+/-5)% RH,

48 24-0h

< 30 ° C, 60% RH, 24 h < 30 ° C, 60% RH, 24 h

B6

(30+/-2) °C, (60+/-5)% RH,

6 24-0h

- < 30°C, 60% RH, 6h

Note 1. The water vapor immersion conditions of conditions B2 to B6 cover the conditions of Step 1 (30 ° C, 60% RH, 24 h) and the conditions of Step 2 (Workshop life).

Note 2. The relative humidity in the dry package exceeds 10% due to the moisture released by the wetted material and the degraded desiccant. Therefore, in SMD dry packaging

Items, IC reels, and other materials are thoroughly dried before being packaged in a moisture barrier bag. Relative humidity in dry packaging through humidity indicator card and SMD water

The steam content measurement is calibrated, see A.2.

Note 3. Because very low relative humidity cannot be obtained in dry lockers, it is not recommended to store SMD in a drying cabinet instead of a dry package.

Note 4. Condition B covers the entire SMD storage process from baking to soldering, including SMD from baking to packaging into dry packaging and dry packaging

Temporary opening and shelf life of the entire room temperature storage duration.

5.4 Welding heat

5.4.1 Overview

Unless otherwise specified in the relevant documents, the sample shall be subjected to a welding heat test within 4 hours after the completion of the water vapor impregnation or high temperature baking test.

According to the requirements of the relevant documents, the test methods and conditions for welding heat are selected from 5.4.2 to 5.4.4. No matter which test method you choose, soldering

The number of hot cycles is at least 1 time and up to 3 times. Except as otherwise provided in the relevant documents, the number of cycles of welding heat is one. If the number of cycles

More than 1 time, after the completion of one test, the temperature of the sample should be reduced to below 50 °C before the next test.

Note. If the sample is stored at room temperature for more than 4 hours without being affected by water vapor impregnation or baking, the storage time of more than 4 hours after water vapor impregnation or baking can be completed.

It is clearly stated in the relevant documents.

5.4.2 Heating method for infrared convection or convection reflow welding

5.4.2.1 Preparation

The sample is placed on a substrate.

5.4.2.2 Preheating

Except as otherwise provided in the relevant documents, the sample shall be placed in the reflow soldering equipment and preheated for 60 s in accordance with the temperature conditions specified in A.3.1.

120s.

5.4.2.3 Welding heat

After preheating, the temperature of the sample should first be raised to the peak temperature and then lowered to room temperature. According to the actual welding conditions, from Table 4 or Table 5

Select the heating conditions, which should be consistent with the relevant documents. See A.3.1 for temperature and time tolerances.

Note 1. In Tables 4 and 5, the test conditions of A are used for the temperature curve with a short actual welding time, and B is used for the temperature curve with a long actual welding time.

Note 2. After preheating, the sample temperature meets the requirements in Figure A.9, Figure A.10 or Table A.2.

Note 3. According to the context, the methods A and B in Table 4 and Table 5 and in the infrared convection reflow soldering are more suitable for condition IA and condition IB.

Table 4 Sn-Pb eutectic process---reflow soldering temperature classification

Package thickness

Mm

condition

Specified welding temperature

Test time

Corresponding volume temperature

< 350mm3 350mm3~2000mm3 >=2000mm3

< 2.5

A 10 240°C 240°C 225°C

B 20 240°C 225°C 225°C

>=2.5

A 10 240°C 240°C 225°C

B 20 225°C 225°C 225°C

Table 5 Lead-free process---Reflow soldering temperature classification

Package thickness

Mm

condition

Specified welding temperature

Test time

Corresponding volume temperature

< 350mm3 350mm3~2000mm3 >2000mm3

< 1.6

260°C 260°C 260°C

1.6~2.5

260°C 250°C 245°C

>2.5

250°C 245°C 245°C

5.4.3 Heating method for gas phase reflow soldering

5.4.3.1 Preparation

The sample should be mounted on a substrate.

5.4.3.2 Preheating

Unless otherwise specified in the relevant documents, the sample shall be placed in a gas phase reflow soldering apparatus and preheated for 60 s at a temperature of 100 ° C to 160 ° C.

120s.

5.4.3.3 Welding heat

After preheating, the temperature of the sample rises. When the sample temperature reaches 215 °C +/- 5 °C, keep 40s +/- 4s according to Table 6,

See A.3.2.

Table 6 Heating conditions for gas phase reflow soldering

condition

temperature

time

II-A 215+/-5 40+/-4

5.4.4 Wave soldering heating method

5.4.4.1 Preparation

The bottom surface of the sample is mounted on the substrate using an adhesive as specified in the relevant documentation. In addition to the relevant documents, in the sample and base

Do not use flux between the plates.

Note 1. If flux is used, vaporization of the solvent in the flux will affect the temperature rise of the sample. The flux cannot coat the body of the sample and is coated as much as possible

Pin and away from the sample body.

Note 2. If the pitch (the difference between the height of the bottom surface of the SMD body and the bottom surface of the lead) is less than 0.5 mm (the thickness of the SMD body is exceeded by using a heat sink to reduce the thermal resistance)

When the 2.0mm is excluded, it shall be tested by the welding heat test in A or B. When the thickness of the SMD body exceeds 3.0 mm, the welding heat in B is used.

Test conditions test. For SMD, the test conditions for A and B are more severe than the conditions for wave soldering III-A and III-B (refer to A.3.3).

Thus, conditions III-A and III-B are generally not employed.

5.4.4.2 Preheating

Except as otherwise provided in the relevant documents, the sample shall be placed in the welding equipment and preheated at 80 ° C ~ 140 ° C for 30 s ~ 60 s.

5.4.4.3 Welding heat

After preheating, the sample and substrate are immersed together in molten solder as shown in FIG. The infiltration conditions were selected from Table 7.

a) Infiltration begins b) End of infiltration

Figure 2 Wave soldering heating

Table 7 Wetting conditions of wave soldering

condition

Welding temperature

Infiltration time

Actual welding method

III-A 260+/-5 5+/-1 single peak

III-B 260+/-5 10+/-1 doublet

5.4.4.4 Cleaning

If flux is used, it should be removed according to the cleaning method specified in the relevant documents.

5.5 Recovery

If the recovery conditions are specified in the relevant documents, the samples shall be stored under standard atmospheric conditions for a specified period of time as required by the documentation.

Note. Wave soldering is not the welding method commonly used by the contractor. If the contractor does not have this equipment, the corresponding welding heat method is between the contractor and the user.

Provisions are made in the agreement between the two.

5.6 Final inspection

5.6.1 Visual inspection

After the test is completed, visual inspection is carried out under a 40-fold microscope in accordance with IEC 60749-3, and the cracks on the outer surface...