If left untreated, contaminants on the surface of a PCB can have devastating effects on the shelf-life and performance of your finished product. Thorough cleanings are essential to ensure the integrity of any High-Quality PCBs, but take care not to damage your fragile boards during the cleaning process! This article outlines the proper methods for cleaning harmful contaminants from the surface of a PCB to ensure that your project always operates at its full potential.
Before we dive into the specifics of cleaning methods, it is helpful to note the types of common contaminants that can be harmful to your PCBs. Knowing the source of these problems can help you to protect against contamination and offer some foresight into when cleaning will be required.
Solder Flux Residue: Often left on a PCB after the PCB Assembly Process, this contaminant appears as a viscous yellowish/brownish substance near solder points. Bittele Electronics always ensures that your boards are clear of harmful residue before shipping them out to you, but you should watch out for this contaminant if you need to do any Manual Soldering or PCB Rework after the fact. Uncleaned solder flux residue can lead to issues such as corrosion and electrical leakage on your PCB.
Dry Contaminants: Small particles of dust and dirt often accumulate on the surface of a PCB over time, depending upon storage or environmental conditions. Watch out for these types of contaminants if your PCBs are stored for any extended period of time in a dry environment. Dust and dirt might seem harmless, but they can still cause electrical leakage in some circumstances, and they might even be a fire hazard in High Voltage PCBs.
Wet Contaminants: Oils and other wet contaminants can accumulate when PCBs are stored in humid environments, or simply due to an accidental spill. Never allow these contaminants to go unattended, as they can easily cause devastating short circuits. The presence of wet contaminants on a PCB can also attract even more dry contaminants to compound the issue.
Manual Cleaning Methods
Brushing is the simplest cleaning method, and it can be quite effective for dry contaminants. It takes a fair measure of finesse, but a soft, fine-tip brush can be used to wipe away dust and dirt. The only issue with this method is that it might be difficult or impossible to reach some areas on the board, even with a very small brush.
Compressed Air addresses the reach issues of brushing, but a hard stream of compressed air can potentially damage sensitive components or connections. Use this method sparingly and with caution.
Component Vacuums with ESD Protection for their tips are offered by some electronics manufacturers. Take care not to jostle any of your boards components while you try to reach into any tight spaces with these devices; otherwise, this is a fine option for cleaning dry contaminants.
Isopropyl Alcohol (IPA) is a common solution for cleaning wet contaminants and solder flux residue. Use a Q-tip, a cotton swab, or a small brush with IPA to wipe down the problem areas. Make sure to use this method in a well-ventilated area or under a fume hood to deal with toxic fumes. Acetone can also be used in the same way.
Demineralized Water can be used in place of IPA to avoid the harsh chemicals noted above, but this method does require some extra care to ensure that the PCB is fully dried before use.
Ultrasonic PCB Cleaning
Specialized ultrasonic PCB cleaners offer the most extreme solution for cleaning PCBs. This method involves sealing the boards in a tank filled with cleaning solution, which is then bombarded with high-frequency sound waves. This process results in an effect called cavitation, where bubbles in the cleaning solution collapse and create a shock wave strong enough to pull contaminants from the surface of the PCB.
Ultrasonic PCB cleaners can be purchased as smaller benchtop devices for individual PCB cleaning, or you can send your boards to a company that specializes in this technique for large-scale batch decontamination. Ultrasonic PCB cleaning is effective at removing contaminants in the most hard-to-reach spaces on your boards, but it comes with its own risks. The physical force that allows for cleaning can damage components or reduce the integrity of solder joints.