Solder paste is a blend of tiny solder particles and flux applied to PCB pads before parts are placed and heated during reflow. The flux cleans metal surfaces and helps the molten solder flow, while the paste holds components in position long enough for assembly.
It matters in cyber security because hardware trust starts at the board level. If paste is applied unevenly, joints can become weak, bridged, or intermittent, creating failures that are hard to diagnose in devices used for secure systems, sensors, or embedded controllers. In manufacturing and prototyping, solder paste is often used with stencils to control deposit size and location. Inspecting paste print quality, stencil alignment, and reflow results helps defenders catch assembly defects, spot counterfeit or tampered boards, and reduce the risk of unreliable hardware entering a trusted supply chain.