The HAKKO B2300 Heat-Resistant Pad is made of ESD safe heat-resistant silicone that contains between 9 and 12% silica, which contributes to the pad's ability to resist very high temperatures. The material is also impregnated with carbon. Under normal usage of the heat-resistant pads, we have not seen any contamination issues resulting in wetting difficulties or other issues with solder connections nor have we seen any adhesion issues when applying a urethane conformal coating. Silicone in this solid stable form generally does not deposit a residue that is then transferred to the PCB assembly. Contamination or residues due to offgassing were also not observed during use or during storage in close proximity to an assembly.