## 3 Experimental Method
The largest single void area per DCB was recorded at 0.58%. These values represent 100% in terms of void presence, serving as the standard for comparison (Figures 11 and 12). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Soldering** \\ **Program** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **C SAM: Average** \\ **Void Area per** \\ **DCB [\%]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **C SAM: MIN** \\ **Void Area per** \\ **DCB [\%]** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **C SAM: MAX** \\ **Void Area per** \\ **DCB [\%]** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **C SAM: the** \\ **Biggest Single** \\ **Void Area per** \\ **DCB [\%]** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **HCOOH Presence** \\ **[s] **(Flooding +** \\ **Dwell Time)** \\ \end{tabular} } \\ \hline Reference & 2.18 & 0.74 & 4.28 & 0.58 & 212 \\ \hline Test V1 & 1.21 & 0.29 & 2.62 & 1.07 & 281 \\ \hline Test V2 & 0.53 & 0.22 & 1.5 & 0.15 & 401 \\ \hline Test V3 & 0.47 & 0.14 & 1.24 & 0.15 & 420 \\ \hline Test V4 & 0.8 & 0.21 & 1.3 & 0.18 & 450 \\ \hline Test V5 & 0.55 & 0.25 & 0.88 & 0.18 & 608 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results from the soldering tests of six different solder programs. Figure 10: Photo example from the wetting test of the modules with and without potential de-wetting; comparison of the quality of two different preform surfaces. Test group 1, with an extended formic acid presence of 281 s, showed a substantial improvement in void reduction. The average void area decreased to 1.21%, marking an 80% improvement over the reference group. The maximum void area decreased to 2.62%, a 63% improvement, while the largest single void area increased slightly to 1.07%, indicating a 54% improvement. The formic acid exposure time increased by 33% compared to the reference group. In test group 2, with a formic acid presence of 401 s, the average void area further decreased to 0.53%, showing a remarkable 311% improvement. The maximum void area was  
Figure 11: Ratio between total void area per DCB and the largest single void area per DCB for different test programs. Visible impact of soft vacuum and cleaning time extension in chamber 1 and 2 on void area for test program V2, V3, and V4. Minimal measured values dispersion for test group V3 and V5. Figure 12: Ratio between total void area per DCB and the largest single void area per DCB for different solder preform batches. Visible impact of solder preform quality on resultant void area. Samples for BG4920 and BG5020 with yellowish surface and with Sb4O6 peak from diffraction analysis. reduced to 1.5%, a 185% improvement, and the largest single void area dropped to 0.15%, a 287% improvement. The formic acid exposure time increased by 89%, demonstrating the significant impact of prolonged exposure. Test group 3 continued this trend, with a formic acid presence of 420 s, achieving an average void area of 0.47%, a 364% improvement over the reference group. The maximum void area decreased to 1.24%, a 245% improvement, while the largest single void area remained at 0.15%, a 287% improvement. The formic acid exposure time increased by 98%. Test group 4, with a formic acid duration of 450 s, maintained low void areas, with an average void area of 0.8%, a 173% improvement. The maximum void area was 1.3%, a 229% improvement, and the largest single void area was 0.18%, a 222% improvement. The formic acid exposure time increased by 112%. Finally, test group 5, with the longest formic acid presence of 608 s, showed an average void area of 0.55%, a 296% improvement. The maximum void area was reduced to 0.88%, representing a 386% improvement, and the largest single void area was 0.18%, thus representing a 222% improvement. The formic acid exposure time increased by 187%.