Water Soluble Cleaning Process

To save product cost and shorten lead times, Emin uses No-clean solder paste for PCB assembly if customers do not specify the requirement of cleaning all flux residues. If required by customers, Emin will use water soluble solder paste and water wash process for PCB assemblies for products where flux residues must not be left on the PCB.

To ensure long-term reliability and durability for some specific electronic products, cleaning flux residue thoroughly from the PCB is important. Water soluble solder paste is more active and needs to be cleaned off the board for reliability. The major reason being the flux residue from water soluble paste is corrosive after soldering and needs to be completely eliminated, as any residues left on the board can cause failures in the board over time due to their corrosive nature, which causes corrosion and can affect the overall performance of components and the board itself.

Still, there are a few specific reasons why customers might want their PCB assemblies to be cleaned and the flux residue to be eliminated completely. Cases like:

• If Conformal coatings are applied, the flux residues may fail the interaction between the conformal coatings on the board.
• When the PCB assemblies are being shown as end products or your customers are going to see the board as is, flux residues can make the board unappealing cosmetically. 
• When using No-clean fluxes, it leaves a little residue on the board, the residue left by no clean flux will not be removed, as a result, it will most likely provide a conductive path for sensitive circuits, such as high impedance analog circuits.
• Flux residues may prevent the probability of making contact with the pads as it gets in the way when testing the electricity and circuit connectivity of the assembled boards.
• Flux residues from No-clean solder processes can cause corrosion in humid environments. Leakage currents and product failures may occur in humid environments. Also remaining ester oil can collect dust, which can act as a humidity absorber.

If you prefer your PCB assemblies in certain projects to be thoroughly cleaned, contact us to learn how Emin can help you with our outstanding experience in processing water wash PCB assemblies.