Small Process, Great Impact: Dry Ice Cleaning

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What is Dry Ice Cleaning?

Dry ice cleaning, also known as low-temperature blasting or carbon dioxide blasting, is a highly efficient, dry, non-abrasive, and environmentally friendly cleaning technology. Its core principle can be summarized as the triple action of "thermal shock," "kinetic impact," and "sublimation."

Cleaning Medium: The cleaning medium consists of extremely low-temperature (-78.5°C) tiny pellets (dry ice pellets) made from solid carbon dioxide (dry ice).

Working Process: By specialized dry ice cleaning equipment, dry ice pellets are mixed with compressed air and high-velocity jetted onto the surface to be cleaned.

Triple Cleaning Mechanism:
1.Thermal Shock: Extremely low-temperature dry ice pellets rapidly freeze and embrittle contaminants, causing them to shrink and detach from the substrate.
2. Kinetic Impact: High-velocity dry ice pellets impact the contaminant surface, exerting a stripping effect similar to that of sandblasting.
3. Sublimation and Expansion: Upon impact, dry ice pellets directly sublimate from solid to gas (carbon dioxide gas), and their volume rapidly expands by nearly 800 times. This micro-explosion effect thoroughly dislodges and removes contaminants from the substrate.

Ultimately, contaminants are removed, and the dry ice vanishes completely, leaving only the detached waste material for disposal, thus achieving dry cleaning without secondary waste liquid.

Why is PCBA Cleaning Necessary?

After soldering, various contaminants typically remain on the surface of PCBAs (Printed Circuit Board Assemblies). These contaminants will pose serious reliability risks. Thereby cleaning is a critical process to ensure the long-term stable operation of electronic products. The primary reasons are as follows:

1. To prevent electrochemical failure (ionic contamination): Fluxes used during the soldering process can leave behind ionic substances (e.g., halide ions). These substances ionize in humid environments, forming tiny conductive paths between points of different electrical potential on the circuit board, which will lead to leakage current, short circuits, and even electrochemical migration, ultimately causing circuit failure.
2. To prevent corrosion: Residual acidic or alkaline substances will continuously corrode precise solder joints, component leads, and copper traces, leading to a decrease in solder joint strength, increased resistance, and even open circuits.
3. Impact on subsequent processes: If the PCBA subsequently requires conformal coating, contaminants on the board surface will severely reduce the adhesion of the conformal coating, easily leading to cracking and peeling, rendering the protective layer ineffective. Similarly, contaminants can also affect the contact reliability of connectors.
4.Aesthetics and Inspection: A clean board surface facilitates Automated Optical Inspection (AOI), while contaminants can interfere with inspection results. Moreover, a clean board is also a symbol of high quality.

When to Use Dry Ice Cleaning for PCBAs?

Dry ice cleaning does not replace all traditional cleaning methods; it offers unparalleled advantages in specific scenarios:

1.Online cleaning (without downtime maintenance): This is one of the greatest advantages of dry ice cleaning. It can be used to clean the guide rails, net plates, and residual flux and carbon deposits in the furnace chambers of pick-and-place machines, screen printing machines, reflow ovens, and wave soldering ovens. Traditional methods require downtime, disassembly, and cleaning, which is very time-consuming. However, dry ice cleaning can be carried out directly online after the equipment is slightly cooled, significantly reducing downtime and improving production efficiency.
2.Cleaning sensitive and complex components: For PCBA with components that should not come into contact with liquids (such as micro-motors, unsealed connectors, optical sensors), or for assembled complete products, the "dry" nature of dry ice cleaning perfectly avoids the risks of short circuits and damage that may be caused by liquid cleaning.
3.Precise cleaning and fragile structures: The non-abrasive nature of dry ice pellets makes it highly suitable for cleaning precise gold fingers, the bottom of QFP/BGA packages with fine pitch, and fragile ceramic components, without causing scratches or wear on the surface.
4. Stringent environmental requirements: Dry ice cleaning does not use any chemical solvents and has no VOCs (volatile organic compounds) emissions. The only waste produced is the contaminants that have been removed, which complies with increasingly strict environmental regulations.

In summary, PCBA cleaning is a necessary step to ensure reliability. For Kingsheng PCBA, investing in the dry ice cleaning technology is a strategic decision. It reflects the company's commitment to the ultimate pursuit of product quality and the green manufacturing concept. By adopting this advanced technology, Kingsheng PCBA can provide its customers (especially those in the fields of automotive electronics, medical equipment, aerospace, high-end communication, etc.) with PCBA products with extremely high reliability and longer lifespan, thereby establishing a strong technical barrier and quality reputation in the fierce market competition.