Issue link: https://iconnect007.uberflip.com/i/1520213
80 SMT007 MAGAZINE I MAY 2024 samples transitioned from negative to posi- tive in heating between 175°C and 200°C and then back to negative in cooling from 200°C to 175°C. Maintaining good sample temperature uniformity is key to this transition happening consistently. Figure 16 shows 3S Warpage. e same transition can also be seen in the shape name variable at each temperature. e 40 x 40 mm sample at MSL4 exposure gener- ally transitions from dome (DM) shape to and bowl (BW) shape, but in the transition some other shapes begin to arise, "X-pipe" (XP) and upward twist (UT), as in Table 2. In some cases, the transition between posi- tive and negative has higher sample to sample variation and is more difficult to find a trend. Here the ability to look at the relative change of the sample is helpful. Figure 17 shows 3S warpage data for the 14 x 14 mm sample at MSL3. e vertical lines on the graph repre- sent "transitional" shapes in the sample data. Figure 16: 3S warpage, 40 x 40 mm, MSL4. Table 2: Shape names, 40 x 40 mm, MSL4 Figure 17: 3S warpage, 14 x 14 mm, MSL3.