What methods of conformal coating removal from circuit boards can you use apart from soldering through the coating?
Stripping of unwanted conformal coating from a printed circuit board (PCB) can be a simple process or a very messy difficult job. It depends on what coating you need to remove, where the coating is and the type of components on the board.
The simplest coatings to remove are the acrylics. They have little chemical resistance and therefore are the easiest to remove with proprietary stripping fluids or even the thinners that the coatings are diluted in. These coatings generally re-dissolve back into solution so a combination of soaking and gentle mechanical abrasion works well.
The simplest process for local area rework around a device for instance is a cotton bud soaked in stripping fluid and then rubbed gently across the area to be removed which will dissolve the coating. If the coating is fresh, it comes off in a matter of seconds whereas if the coating is old, having been coated many years ago, then it could take a little longer and patience is required!
If the area to be removed is larger or the whole board is to be stripped then submersion in a tank correctly selected stripping fluid and abrasion using a soft bristle brush will also dissolve the coatings. A word of warning must be given here. First, when submerging in a stripping material check there are no compatibility issues with the PCB. Stripping fluid could attack components and or writing on the boards occasionally although for acrylic coatings the stripping fluids tend to be less aggressive.
The other issue that can be a major headache with full stripping of a board is that because the coating re-dissolves into the stripper, there will now be coating residue all over the PCB even where you didn’t want it. This can be a real problem with certain components such as low profile connectors! To remove these residues you will need several tanks of stripping fluid and the PCB will need to be fully rinsed in each, gradually flushing the residue out of the wrong areas. Once completed the PCB should then be cleaned in a cleaning system to remove any unwanted ionics.
These two processes also work for conformal coatings such as polyurethanes and silicones although since they have chemical resistance they are tougher to remove. Correct stripping solution selection is critical and using the correct proprietary stripping fluid can be very important.
SCH Technologies carries out specialist Conformal Coating Removal and Rework of printed circuit boards (PCBs) as a subcontract coating service for customers where the stripping materials may be hazardous or the process is just too inconvenient to complete. We also provide Conformal coating Stripping Systems that have been designed for complete removal & stripping of conformal coatings, paints and lacquers from products such as printed circuit boards (PCBs).
Contact us now to discuss your conformal coating removal.