Home > News > ultimate-pcb-cleaning-guide-methods-tips-best-practices.html

Ultimate PCB Cleaning Guide: Methods, Tips & Best Practices

02 Jul 2025 11:26:16 GMT PCBASAIL

Table of Contents

I. Introduction

Ordinary electronics have been in use for a long time, and their circuit boards inevitably become covered with dust. When dust accumulates excessively or the air humidity is high, it can corrode the board or even lead to a short circuit. Whenever you see a lot of dust on a PCB, it’s time to clean and maintain it. Even before leaving the factory, more complex boards—like system boards, graphics cards, sound cards, network cards, and so on—undergo cleaning. The purpose is to remove any flux residues, fingerprints (even though everyone handling these devices wears gloves), and other harmful substances that cling to the board during assembly.

In mass production, manufacturers use specialized cleaning fluids (commonly called “PCB wash”) and automated washing machines. For individual users, however, it’s impractical to operate like a board manufacturer; you only need to be careful and cautious during the cleaning process. Cleaning a PCB isn’t difficult or scary—it’s completely doable with the right approach.

II. Why PCBs Need Cleaning

Cleaning a PCB after manufacturing and soldering is a crucial part of the electronics assembly process. It directly affects the device’s overall durability, reliability, performance, and lifespan. During assembly and manufacturing, PCBs can become contaminated with flux or solder, handling or environmental dirt—such as residues, dust, moisture, resin or lacquer, fingerprints, or oxides. Some contaminants can even be corrosive, damaging circuit traces and connections, leading to shorts or malfunctions that shorten the device’s service life. Removing these kinds of debris ensures that functional failures don’t occur over time and extends the equipment’s usable life.

When cleaning assembled PCBs, the main goal is to remove resin and flux residues left on the board. Industries such as automotive, telecommunications, military, and aerospace require that PCB assemblies be completely free of any potential contaminants. A contaminant-free PCBA is essential before the next manufacturing steps—whether that’s underfill, epoxy staking, or conformal coating. If flux residue remains on the board, it can impair solder wetting and promote delamination. Additionally, a clean PCB simply looks more professional.

During inspections or future troubleshooting, having a clean, tidy PCB is also beneficial. When you clear away residual contaminants or stray solder, it’s much easier to spot defects or potential issues.

You may encounter “no-clean” fluxes advertised as not requiring PCB cleaning after application. However, even boards soldered with “no-clean” flux benefit from a cleaning step—it prevents leakage currents and improves appearance. Although these fluxes are designed to leave minimal residue, they don’t entirely eliminate the need for cleaning.

III. Main PCB Cleaning Methods

PCB cleaning typically employs different methods, each with its own advantages and potential drawbacks. The method you choose depends on factors such as board complexity and component density, available equipment, cost and budget, the number of boards to clean, environmental impact, and time constraints. The main cleaning methods are:

Manual Cleaning
Ultrasonic Cleaning
Vapor-Phase Cleaning
Deionized Water Cleaning

Below is an overview of each approach.

1. Manual Cleaning

One of the most common PCB cleaning methods is manual cleaning. As the name suggests, any contamination or leftover solder can be removed by physically cleaning the board with alcohol-based solutions and small brushes. Sometimes other tools are used alongside brushes to physically dislodge debris.

Typical procedure:

Soak the PCB in an acetone solution for about 10 minutes to loosen any contaminants or dirt.
After soaking, gently brush off unwanted particles using a small brush dipped in isopropyl alcohol (IPA).
Rinse the board in softened water for a few minutes to flush away any loosened debris.
Finally, use a nitrogen gun to dry the board completely.

Pros:

Simple and affordable: requires no specialized equipment, and supplies are easy to obtain.
Relatively low toxicity to humans and the environment.

Cons:

Lack of automation makes it time-consuming, especially for multiple boards.
Not ideal for high-volume production.
Brushes can only reach areas they physically fit into, so complex or densely populated boards may not get fully cleaned.

Manual cleaning is best suited for prototypes, small batches, or quick maintenance when thoroughness and speed aren’t critical.

2. Ultrasonic Cleaning

Ultrasonic cleaning uses a specialized machine designed for PCB cleaning. Like the manual method, you first soak the board in an IPA solution to free surface dirt, pollutants, or excess solder. Then you place it in the cleaning-fluid tank inside the ultrasonic cleaner. The machine emits high-frequency sound waves into the liquid, creating billions of microscopic cavitation bubbles. When these bubbles collapse, they physically strip contaminants from the PCB—a process known as cavitation.

Pros:

Excellent for very dense or complex boards: the cavitation bubbles reach every exposed surface point, including tight, hard-to-reach spots.
Fast and uniform cleaning without reliance on manual scrubbing.

Cons:

Ultrasonic waves can potentially damage sensitive components or solder joints if exposure is too long or too intense.
Requires investment in an ultrasonic cleaning machine and compatible cleaning fluids.

Ultrasonic cleaning is the go-to for boards that are too intricate for brushes but where you’re willing to accept a measured risk of component stress.

3. Vapor-Phase (Vapor Degreasing) Cleaning

Also called vapor degreasing or vapor-phase cleaning, this method boils a chemical solvent to generate vapor, which then dissolves dust and contaminants on the PCB. After the vapor condenses back into liquid form on the cooler board, gravity returns it to the boiling bath, completing a closed-loop cycle.

Pros:

Highly effective at dissolving a wide range of residues.
Closed-loop systems recycle solvent, reducing waste.
Only heats boards to the solvent’s boiling point, minimizing thermal stress.

Cons:

Requires specialized vapor degreasing equipment.
You must carefully select solvents based on boiling points, flammability, and environmental profile.
Additional drying steps may be needed to remove any remaining solvent.

Vapor-phase cleaning is common in industries with stringent cleanliness standards—such as medical or aerospace—thanks to its consistent, automated performance.

4. Deionized Water Cleaning

Deionized (DI) water is a safe, effective solution for removing water-soluble flux residues. If you use a water-soluble flux in your leaded or lead-free solder paste, you can rinse the PCB with DI water. Online or batch washers deliver high-temperature, high-pressure DI water (typically around 144 °F at 45 psi) to wash and rinse assemblies, followed by forced-air nozzles to dry the board. Ionic and resistivity tests verify cleanliness afterward.

In some cases—particularly with eco-friendly, water-based fluxes—you can manually soak assemblies in a water-based alcohol cleaner and then rinse with DI water. Since DI water is the purest form of water, quality-focused contract manufacturers often standardize on it for PCB washing.

Pros:

Non-toxic, non-flammable, and readily available.
Ideal for fluxes formulated for water wash processes.
Eliminates organic solvent handling and disposal concerns.

Cons:

Only works with compatible water-soluble fluxes.
Thorough drying is essential to prevent moisture-related failures.
Water treatment and disposal must comply with environmental regulations.

IV. Selecting Your Cleaning Method

When deciding which cleaning approach to use, consider these factors:

Component Complexity & Density: High-density boards favor ultrasonic or vapor methods.
Production Volume: Manual methods don’t scale well; automated systems shine at high throughput.
Budget & Equipment: Balance upfront investment against per-board labor and consumable costs.
Environmental & Safety Regulations: Solvent disposal, VOC emissions, and wastewater treatment all have legal requirements.
Drying Requirements: Some processes leave moisture that must be carefully removed.

For hobbyists or small labs, a practiced manual routine with IPA and soft brushes often suffices. As you scale up—or if you handle mission-critical or highly dense boards—you might invest in ultrasonic or vapor degreasing systems.

V. Best Practices & Tips

Always wear gloves (nitrile or latex) to avoid transferring oils and fingerprints.
Use lint-free brushes designed for electronics.
Keep cleaning solutions fresh—old, contaminated fluids clean poorly.
Test any new cleaning process on a scrap board before running valuable assemblies.
Document soak times, temperatures, and drying methods to reproduce consistent results.

VI. Conclusion

PCB cleaning may seem like an extra chore, but it’s a vital step to ensure your electronics perform reliably and last longer. Whether you choose manual scrubbing, ultrasonic cavitation, vapor-phase degreasing, or water rinsing, pick the method that matches your board’s complexity, production volume, and budget. With careful attention to technique and best practices, you can keep your PCBs looking pristine and functioning flawlessly for years to come.