Solder Powder

Solder powders are the key component of all solder pastes

Solder powders are the key component of all solder pastes. Pastes made with the same flux but with powders that differ in particle sizes often have different rheological/ physical properties resulting in differences in screen/ stencil printing, component placement and production yields. The powder constituent of solder paste, in fact, affects all stages of surface mount assembly from stability and printability of the paste, to the quality of the final fillet. Main CharacteristicsGood solder powder must have the following properties: a clean dry sand appearance, a gray- silver color vs. a charcoal- gray, which indicates presence of oxidation and good flow behavior go to functional test. Other important features include high powder density close to the theoretical density of the alloy and no internal voids or external satellites (microspheres attached to a single sphere) . The trained eye of a technician often evaluates some of those properties. Others are governed by formal test procedures. For example, powder flow can be tested according to ASTM B- 213, and the presence of voids can be checked by microscopic examination of cross section of individual particles. The user can identify the powder by both composition and type. Alloy composition refers to the main alloying elements; type to the range of particle (mesh) sizes.