IEC 60749-20-2020 pdf free download – Semiconductor devices – Mechanical and climatic test methods – Part 20: Resistance of plastic encapsulated SMDs to the combined effect of moisture and soldering heat.
6Procedure
6.1 Initial measurements6.1.1 Visual inspection
Visual inspection,as specified in lEC 60749-3，shall be performed before the test.Specialattention shall be paid to external cracks and swelling,which will be looked for under amagnification of 40x.
6.1.2 Electrical measurement
Electrical testing shall be performed as required by the relevant specification.6.1.3lnternal inspection by acoustic tomography
Unless otherwise detailed in the relevant specification, internal cracks and delamination in thespecimen shall be inspected by acoustic tomography in accordance with IEC 60749-35.
6.2Drying
Unless otherwise detailed in the relevant specification，the specimen shall be baked at125°C± 5 °C for at least 24 h.
NOTE1 This time/ltemperature is modified if desorption data on the particular device under test shows that adifferent condition is required to obtain a “dry”package when starting in the wet condition for 85 °C/85 % RH.
NOTE 2 lf a bake test is interrupted for more than 15 min, then the total time of the interruption is excluded fromthe bake time.The interruption time is taken into account (if no greater than 1 h) then re-incorporated to ensure aminimum of 24 h. For instance, if the interruption was 45 min, then the total bake test time would be 24 h and45 min. If greater than 1 h the bake is restarted for a full 24 h.
6.3 Moisture soak
6.3.1General
Unless otherwise detailed in the relevant specification，moisture soak conditions shall beselected on the basis of the packing method of the specimen (see A.1.1，Annex A). If bakingthe specimen before soldering is detailed in the relevant specification, the specimen shall bebaked instead of being subjected to moisture soak.
6.3.2Conditions for non-dry-packed sMDs
The moisture soak condition shall be selected from Table 1， in accordance with thepermissible limit of actual storage (see A.1.2.1 ).
6.3.3Moisture soak for dry-packed sMDs6.3.3.1General
Moisture soak conditions for dry-packed SMDs may be used as specified in method A, Table 2,or method B,Table 3. Moisture soak conditioning for dry-packed SMDs consists of two stages.The first stage of conditioning is intended to simulate moisturizing SMDs before opening thedry pack/dry cabinet. The second stage of conditioning is to simulate moisturizing SMDsduring storage after opening the dry pack for soldering (floor life).Moisture soak conditioningfor dry-packed SMDs shall be selected from method A or B.Method A shall be used when therelative humidity in the dry pack or dry cabinet is specified by the manufacturer as beingbetween 10 % and 30 %.Method B shall be used when the relative humidity in the dry pack ordry cabinet is specified by the manufacturer as being below 10 %.
6.3.3.2Method A
Unless otherwise detailed in the relevant specification, the first stage conditioning of A2,asshown in Table 2, shall be performed.Subsequently, the second stage conditioning of A2,asshown in Table 2, shall be performed within 4 h of finishing the first stage of conditioning(see A.1.2.2).
The relative humidity of the first stage conditioning shall be the same as the upper limit of therelative humidity inside the moisture barrier bag. The relative humidity of the second stageconditioning shall be the same as the conditions of floor life.
Where required in the relevant specification, test conditions other than those of the moisturebarrier bag and floor life conditions may be specified in the moisture soak conditions ofTable 2.IEC 60749-20 pdf download.