How does solder paste work?
Solder paste is a mixture of metallic alloy in powder form and flux. It can be applied via stencil printing, needle dispensing, direct dipping or jetting. After applying the solder paste, the entire substrate undergoes reflow process in an oven. Flux activates the solder powder to promote metal coalesces such that the parts are fused together for an electrical connection.
Which solder paste is the best for which use?
There are various types of solder paste for applications in communications and consumer electronics, like wireless and Bluetooth modules, but also medical technology or the automotive sector. For form factor sensitive devices, System in Package (SiP) substrates in varying sizes have more stringent requirements on solder pastes. The smaller the pad size on the substrates, the smaller the solder powder size is used for the solder paste application. For highly dense SiP applications, the spaces between components are less than 60um in width and the pad sizes are less than 100um. The corresponding powder size type must be used for effective and reliable connections. And at Heraeus, we have developed water soluble solder paste in Type 4, 6 and 7 to address customer’s needs.