Cleaning Flex PCB Manufacturings

PCBs can be damaged by any number of contaminants – dirt, dust, chemicals, moisture, acids, and even flux residue. Strict quality control and standard operating procedures during assembly, soldering, and final cleaning stages can go a long way to prevent contamination and ensure reliable operation for the life of the product. But, even with the best quality control, sometimes PCBs can suffer from contamination issues that require advanced techniques to resolve.

If a flex pcb manufacturing has been exposed to salt water, for example, the metal surfaces may develop oxides that don’t yield to gentle scrubbing or acidic cleansers. In such cases, it may be necessary to resort to special techniques like media blasting (glass or plastic-bead blasting) or brass-based deoxidizers.

Other contaminants that are more difficult to remove include those caused by poor fabrication or usage practices. For example, an openly ventilated package can allow dust to enter the circuit board and settle there, where it can wreak havoc on delicate components. An improperly sealed or plugged in package can also let airborne contaminants in, potentially damaging the board.

What Techniques Are Used for Cleaning Flex PCB Manufacturings?

The PCB’s location and type of coating or soldering process can also impact its cleanliness and ease of repair. For example, a tacky flux is more challenging to clean because it tends to leave more soil behind. It can also create flux dams under low stand-off components that prevent solvents from fully penetrating underneath them. Soldering temperatures that are higher than the recommended level can also be problematic, as they cause more bake-on residues.

A typical PCB cleaning process includes an acetone solution soak, followed by a banister brush scrub and absolute ethyl alcohol rinse with deionized water. Depending on the product, it may also be placed in an ultrasonic cleaner for 3 minutes with manual inspection and brushing before being dried with a nitrogen gas gun.

For larger production runs, automated cleaning is a preferred method. The boards are placed on a conveyor that passes through wash, rinse, and dry zones. Some systems use an inline flux remover that sprays the boards with solvent, while others use a vapor degreaser. For the most efficient and reliable results, it’s best to choose a system that provides both of these functions.

Before starting the cleaning process, it’s important to unplug and turn off any devices with which the PCB is associated. It’s also a good idea to take pictures of the device before disassembling it so that you can refer to them for reassembly. Once the board is disassembled, it’s a good idea to use a non-toxic cleaner such as baking soda and distilled water. This combination has mild abrasive properties that are better than abrasive chemicals like sandpaper or steel wool. Using the mixture will dissolve and then wipe away sticky residues without affecting the integrity of the board’s components. It is important to allow the board to completely dry before reassembling it to avoid any potential electrical issues.