Moisture Sensitivity Level/Pre-Conditioning Testing

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-020D.1 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 they can be properly packaged, stored, and handled to avoid damage during assembly solder reflow attachment. 

It is usually performed at two levels chosen to bracket the expected level of capability.

JESD22-A113F 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:

                   MSL                                                                 Preconditioning

                    Initial Visual Inspection                                               Visual Inspection 
                    1st Acoustical Microscope                                          
Temp Cycle - 5 cy (Optional)      
                    Bake- 24 hr. - 125 C                                                   
Bake - 24 hr. - 125 C 
                    Moisture Soak (see 1&2)                                             
Moisture Soak (see 1&2)
                    Reflow 3X                                                                 Reflow 3X
                    Final Visual Inspection                                                Flux + Clean (see 3)
                    2nd Acoustical Microscope                                          Dry