All You Need to Know About NoClean Solder Paste

1. All You Need to Know About NoClean Solder Paste Solder paste is important in the assembly of printed circuit boards for electronic devices. It is not merely an adhesive, but a material that enables electrical connections between the parts of the board. During application, it is typical for the paste to leave a residue, which needs to be removed or cleaned up to reduce defective circuits. To save time, some manufacturers consider no-clean solder paste, which is formulated to provide excellent printing performance and meet the latest performance demands and printing challenges of today’s electronics assembly processes. Using a no-clean solder paste may seem practical, but there are some things you need to know about this alternative to traditional solder pastes before you consider it. Cleaning may still be required post-assembly – Most printed circuit boards are already being assembled with a no-clean solder paste, but despite the name, it will still require cleaning. Manufacturers may have adjusted their assembly lines to accommodate the no-clean paste, but their processes may not be able to adapt to other kinds of paste. So, boards that were assembled with the no-clean paste may still have to be cleaned. The liquid flux can be difficult to remove – Flux residues from the no-clean solder paste will be hard to clean from a PCB, as the product itself is formulated to not be cleaned. For this reason, the so-called no- clean solder paste is more precisely described as ‘low-residue pastes’, as the flux will still leave a minimal amount of resinous, non-corrosive residue around or on the solder joints. The residue may vary in color, depending on the flux resin and the reflow temperature. The amount of residue will depend on the composition of the no-clean liquid flux – To be specific, it will depend on the volume of gelling agents, activators, and solids-resins. The less solids, the less flux residue will be left on a PCB. Most no-clean pastes these days have around 50 to 70 percent solids. Be mindful of the formulation – Some manufacturers of electronic bonding and soldering materials have formulated a range of no-clean solder paste products designed for reflow and ultra-fine feature printing applications. Their products are unlike the regular no-clean liquid flux, as they are ultra-cleanable, zero- halogen, and lead-free, making them ideal for reflow and printing Type 5 and Type 4 powders. This way, the product enables efficient print volume deposit repeatability to reduce board defects.