IEC 60749-20:2020 pdf free download – Semiconductor devices – Mechanical and climatic test methods
4 General description
Package cracking and electrical failure in plastic encapsulated SMDs can result whensoldering heat raises the vapour pressure of moisture which has been absorbed into SMDsduring storage. These problems are assessed. In this test method，SMDs are evaluated forheat resistance after being soaked in an environment which simulates moisture beingabsorbed while under storage in a warehouse or dry pack.Moisture sensitivity level (MSL)ratings generated by this document are utilized to determine the soak conditions forpreconditioning in accordance with lEC 60749-30.
5.2 Reflow soldering apparatus
The infrared convection，the convection and the vapour-phase reflow soldering apparatusshall provide temperature profiles complying with the conditions of soldering heat defined in6.4.2 and 6.4.3. The settings of the reflow soldering apparatus shall be adjusted bytemperature profiling of the top surface of the specimen while it is undergoing the solderingheat process,measured as shown in Figure 1.
5.3 Holder
Unless otherwise detailed in the relevant specification，any board material,such as epoxyfibreglass or polyimide，may be used for the holder. The specimen shall be placed on theholder by the usual means and in a position as shown in Figure 1. If the position of thespecimen, as shown in Figure 1, necessitates changing the shape of terminations and resultsin subsequent electrical measurement anomalies, a position that avoids changing the shapeof terminations may be chosen, and this shall be specified in the relevant specification.
6.3.3.1General
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 packldry 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 %.
6.3.3.2 Method 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 of Table 2.