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70 SMT007 MAGAZINE I MAY 2024 internal delamination will play a role in warp- age levels over reflow. Package warpage is gen- erally accepted to be mainly driven by CTE mismatch between package materials, thus an additional force, such as vapor pressure, is expected to have some level of impact. How- ever, the impact of vapor may not be statisti- cally relevant and may be within the noise of measurement resolution and/or test variation. One common method for identifying inter- nal package delamination is scanning acous- tic microscopy (SAM) 4 . is method can look inside a package for delamination. SAM, or C-SAM, is performed in water and is not used for behavior of a package through reflow tem- peratures. A previous iNEMI study "Recent Trends of Package Warpage Characteristic," also asked the question of relations between mois- ture exposure and warpage 5 . However, this study was unable to find any statistically rele- vant relation between moisture exposure and warpage. Further studies related to MSL lev- els have also found that the length of a reflow profile can play a role in the effects of moisture exposure on reliability 6 . Component warpage is a well-established reliability and yield concern for electronics packaging. Multiple industry standards define allowable warpage levels and component test- ing best practices, including JEDEC JESD22- B112B 7 , JEITA ED-7306 8 , and IPC-7095D9. ese standards are used for testing approaches within this study, as well as data analysis. Additionally, numerous published studies show the relationship between component thermal warpage and surface mount defects. ese studies include such titles as, "Reflow Warpage Induced Interconnect Gaps between Package/PCB and PoP Top/Bottom Pack- ages" 10 and "Effect of Package Warpage and Composite CTE on Failure Modes in Board- Level ermal Cycling" 11 , to name a few. METHODOLOGY: Moisture Exposure All samples were subjected to a 24hr 125°C prebake to establish a starting "dry" moisture condition. Aer this point, samples were tested in four different tracks: control, MSL3, MSL3 "reset track" (samples are baked 24 hours at 125°C aer moisture exposure), MSL4. Sam- ples were always tested within six hours of each exposure condition end. e moisture expo- sure and preheat path of each track is summa- rized in Figure 2 below. Figure 2: Moisture exposure tracks test samples.