The temperature range settings change from one sample to another The initial

The temperature range settings change from one sample

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The temperature range settings change from one sample to another. The initial and final temperature chosen were selected within a 10 o C margin around the expected melting temperature. 3 Results DSC measurements produced heat flow peaks around the melting temperature of the solders, as it can be seen for the Eutectic SnPb solder in Figure 1 . Onset temperature and heat of fusion were determined by the software. 1
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Table 1: Composition, mass and melting temperature of the samples used Composition (%) Mass (mg) Theoretical Melting Temperature ( o C) [2] Pb 100 31.20 330 Sn 100 11.97 234 Sn Pb eutectic 11.97 182 Sn 95.5 Ag 3.8 Cu 0.7 10.97 220 Sn 97 Cu 3 28.35 233 Sn 99.3 Cu 0.7 47.9 232 The curves of all six different solders were combined in Figure 2 to easily see a comparison. As can be seen in Table 2 the melting temperature of the lead containing solder is lower by 40-50 o C than the lead-free Sn based solders. The pure lead solder has a melting temperature significantly higher than all other solders. Additionally, the pure lead and lead containing solders have a lower heat of fusion than the lead-free solders, which all have roughly the same heat of fusion. Figure 1: Eutectic Sn-Pb solder 2
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Figure 2: Comparison between the different solders Table 2: Onset temperature and heat of fusion of the samples used Composition (%) Melting temperature ( o C) Heat of fusion (J/g) Pb 100 326 22.4 Sn 100 231 59.2 Sn Pb eutectic 178 46.1 Sn 95.5 Ag 3.8 Cu 0.7 217 63.1 Sn 97 Cu 3 228 57.7 Sn 99.3 Cu 0.7 227 59.8 4 Discussion The melting temperature of the investigated lead-free solders is higher than the eutectic tin-lead solder, putting them just outside the range of low-temperature solders (up to 183 o C). However, they might still be suitable as a replacement for the lead containing solders previously used in electronics. A troubling issue with these solders, however, is their significantly higher heat of fusion. The surrounding electronics are also affected by the heat generated while soldering. With the higher heat of fusion, melting the solder and subsequent solidification will
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  • Spring '18
  • Dr. maarten bakker

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