Soldering is not a new technology by any stretch of the imagination. It used to involve hammers, anvils and blacksmiths, heating up metals and pummeling them until they were welded together. But we've come a long way since then.
Solder pastes, solder preforms, solder spheres, solder bars and preforms are only some of the tools we have today to create connections regardless of substrate and temperature. From sealing and low temperature soldering to braze and high temperature applications, soldering materials and alloys cover the entire range.
Solder Powder Particle Sizes | Powder Description | Description | Particle size |
| Type 3 | AGS | 20 - 45 |
| Type 4 | DAP | 25 - 38 |
| Type 4.5 (4A) | DAP+ | 20 - 32 |
| Type 5 | KBP | 10 - 25 |
Solder flux
Flux is used to remove oxidizing metals, seal out air to prevent oxidization and enhance the wetting characteristics of the substrate to improve amalgamation.
Soldering materials that contain flux are divided into Clean and No Clean materials. Flux can be corrosive so the Clean (meaning Clean it) category needs cleaning while the No Clean category suggests that it can be used without the extra cleaning step.
For "No Clean" flux, this is indeed the case for most applications since they leave little to no residue that doesn't affect the circuits. There are some specific applications environments though where even though the residue is minimal, it can potentially interfere with testing or other accompanying processes. So for high clock speed electronics, to improve the substrate adhesion of packages that will be underfilled and for cosmetic reasons, assemblers tend to go against the grain and clean the "no clean".
Halide containing, "Clean" fluxes, while leaving more residues, are easier to clean within a short wash cycle. Ironically enough the halide free "No clean" flux chemistry makes it harder to remove so a proper saponified solution must be used.
