PCB Cleaning FAQ – Expert Answers from ZESTRON

PCB cleaning is the process of removing flux residues, solder paste residues, oils, and ionic contamination from printed circuit board assemblies after soldering. These contaminants can cause corrosion, electrical leakage, and long-term reliability failures if not properly removed.

PCB cleaning improves electrical performance, prevents corrosion, and increases the long-term reliability of electronic assemblies. Residues left on circuit boards can lead to leakage currents, short circuits, and premature product failure in demanding applications.

PCB cleaning removes several types of contamination, including:

• Flux residues

• Solder paste residues

• Oils and greases

• Ionic contamination

• Dust and particulates

Each type of residue can negatively affect performance and must be removed to meet reliability standards.

Yes. No-clean flux residues can still leave harmful films and ionic contamination on PCB surfaces. Proper cleaning chemistry and validated processes can effectively remove no-clean, rosin-based, and water-soluble flux residues.

The correct cleaning chemistry depends on:

• Flux type

• Level of contamination

• Board materials

• Component sensitivity

• Cleaning equipment used

Process selection should be based on testing and qualification to ensure compatibility and performance.

Common PCB cleaning methods include:

• Aqueous cleaning

• Semi-aqueous cleaning

• Solvent-based cleaning

• Batch cleaning systems

• Inline cleaning systems

The best method depends on production volume, contamination type, and cleanliness requirements.

PCB cleanliness can be verified using analytical and electrical tests such as:

• ROSE (Resistivity of Solvent Extract) testing

• FTIR (Fourier Transform Infrared Spectroscopy)

• Surface Insulation Resistance (SIR) testing

• Visual inspection under magnification

These methods confirm that residues are below acceptable limits.

PCB cleaning is recommended when:

• Using high-reliability electronics

• Producing high-voltage assemblies

• Manufacturing medical or aerospace electronics

• Experiencing field failures or corrosion

• Changing flux or solder paste materials

In many cases, cleaning is necessary even when using no-clean materials.

PCB cleaning provides several key benefits:

• Improved electrical reliability

• Reduced leakage currents

• Lower risk of corrosion

• Better coating and conformal coating adhesion

• Increased product lifetime

Clean boards lead to more stable and predictable performance.

Yes. PCB cleaning processes can be qualified through laboratory testing and process development. Qualification ensures the selected chemistry and equipment achieve the required cleanliness level before full-scale production begins.