Due to the trend of switching to Pb-free solder along with recent changes in JEDEC standards that apply to MSL and preconditioning testing, an explanation of the differences between MSL and pre-conditioning testing is warranted.

IPC/JEDEC J-STD-020C is the standard used to initially identify the classification level of nonhermetic solid state surface mount devices (SMDs) that are sensitive to moisture-induced stress so that they can be properly packaged, stored, and handled to avoid damage during assembly solder reflow attachment and/or repair operations. It is usually performed at two levels chosen to bracket the expected level of capability.

JESD22-A113D is the test method that establishes an industry standard preconditioning sequence for non-hermetic solid state surface mount devices (SMDs) that are subjected to multiple solder reflow operations. The SMDs should be subjected to the appropriate preconditioning sequence of this document prior to being submitted to specific reliability testing to evaluate the long term reliability.

MSL should be established for the SMD prior to subjecting the part to the preconditioning sequence. This level will dictate storage times for unsealed devices awaiting assembly.

Note: The tests should be performed at the highest temperature that the SMD is expected to see during its’ actual assembly.

The sequence of tests for each of the standards is listed below. Although both standards have similar tests and conditions, there are subtle differences, particularly in the MSL reflow process temperatures for Pb-free solder. The reflow temperatures are dependent on package thickness and volume in all cases.

Sequence:

** Exact conditions vary with moisture sensitivity level

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