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80 SMT007 MAGAZINE I OCTOBER 2018 Discussion Paste A indeed provides better voiding under the same processing conditions. Paste A produced 40 percent lower number of physi- cal voids and provided an average of 9 percent voiding per total area when compare to 19% for Paste B. The presence or absence of vari- ous useful ingredients exist for both Paste A and Paste B which can impact voiding in either direction as seen in the results. As a general guideline, it is important to understand the trade-offs between a paste that delivers low voiding and the other paste characteristics that could be impacted. This decision will be dependent on the acceptable voiding crite- ria for a given application / customer require- ments. Conclusions Voids are an area of concern for the long- term durability and functionality of elec- tronic devices. Voids near or at the interface of surface mount technology (SMT) component input/outputs (I/O's), or the circuit board substrate can be highly probable initiators of crack propagation, leading to the high possi - bility of a field failure. Also, voids are very good insulators of heat, leading to thermal issues with heat sinks and thermal pads often used in LED packages. Figure 13: X-ray voiding images of paste A vs. paste B. Table 8: Voiding size and frequency.