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72 SMT007 MAGAZINE I MAY 2024 Six different sample types were tested in this study. ree to four samples per test condition were tested depending on sample availability. Package type and size descriptions were kept generic to protect the component manufac- turer. For the same reason, some of the sample sizes are approximate and not exact. A range of different sample types were chosen to rep- resent a reasonable combination of different surface mount package types. Package type, size, and tested quantities are summarized in Table 1. Reflow Profile and Measurement Technique A typical lead-free reflow profile with peak at 250°C was used in this study. An example thermal output from a thermal warpage run is shown in Figure 3. For all tests an extra sample was used purely for capturing temper- ature within the system. e actual tempera- ture is defined by the red line, Process 1. Other oven commands, including warpage acqui- sitions are shown on the graphical output in Figure 3. All samples were subjected to a com- parable profile. Surface warpage measurements over temper- ature are taken using the shadow moiré (SM) technique with samples placed in an IR oven, in a metrology tool used for measuring surface shape over reflow temperatures. e SM tech- nique measures surface height by shining a line light through a grating glass. An interfer- ence pattern between the lines and shadow cast by the same lines creates a contour map used for measurement. e SM technique utilizes a phase stepping method, applied for increased resolution. Camera images are captured with different distances between the grating and Table 1: Test samples Figure 3: Example reflow profile output.