Why Small Particles Stick – Clean the Cleanroom

We all know that the smaller the particle, the harder it is to clean. They always get stuck in those tiny, hard-to-reach spaces. Here’s why.

Dispersion forces. They make a gecko’s feet stick to walls. They also make small particles get stuck in really tiny places and cause them to be so hard to clean. Let’s see why this kind of force is making your life cleaning the cleanroom so difficult.

Molecules that have dipoles, or permanently positively and negatively charged sides are associated with polar and hydrogen bonding forces. However, dispersion forces are a property of all molecules regardless of an inherent dipole. Since electrons are always in motion, momentary fluctuations can occur when more electrons are on one side of a molecule than the other. This causes a momentary negative charge on the side with more electrons and a positive charge on the opposite side, creating a momentary dipole.

When a molecule comes close to a molecule with a momentary dipole, its electrons are compelled to move. This creates an attractive force between the molecules. If the colliding molecules don’t have enough energy to bounce back, they stick together. The dipole then lasts as long as the molecules are bound together. The pair becomes a dipole in itself, creating a chain reaction.

Since the molecules have to be very close together in order to adhere, crevices become fertile grounds for dispersion forces. This is also true when soil dries. Soil molecules that are in liquid become close enough together during evaporation to attract the dispersion force. Thus, dried soil is tougher to clean than wet.

You see why it is so important to perform critical cleaning as soon as possible. The longer you wait, the harder the job will be. You can’t beat science!

For cleanroom validation and certification, contact Gergig Engineering Company. Check out the services on our website for more information or contact us at: 888-628-0056; info@gerbig.com.

Cleaning the Components in Electronics Manufacturing

Electronic components in adverse environments require careful cleaning to remain compliant. This article explores the means of doing so.  

Thanks to no-clean fluxes and soldering pastes, the need to clean components in electronics manufacturing has decreased significantly. However, this is only the case for components used in non-critical atmospheric environments. Adverse environments, like humid or fluctuating temperatures, can erode the protective layer applied in the no-clean process. This releases ionizing substances that promote electro-migration and dendritic growth. You’ll find this in narrow spaces under components and between connections and contact surfaces. Additionally, fluxes, residues of soldering agents and adhesives, and dust need to be removed from electronic components.

In choosing a cleansing agent, you need to consider the subject material as well as the nature and quantity of the impurities to remove. Cleaning agents for electronics include solvents, water-based media containing alkaline surfactants, and water-based tenside-free solutions.

Solvent Options

Solvents for the electronics manufacturing industry contain non-halogenated hydrocarbons, modified alcohols, or hydrofluorethers (HFEs). HFEs are the alternative to chlorofluorocarbons (CFCs), which were found to have a high potential for breaking down ozone about 20 years ago. Both have similar properties, but HFEs don’t persist in the atmosphere and pose no danger to ozone. Monosolvent, bisolvent, and cosolvent systems use these solvents.

  • • Monosolvent: Using a pure HFE or azeotrope, these systems remove slight impurities like halogen compounds, particles, dust, light oils, and residue of easy-clean solvents.
  • • Bisolvent and Cosolvent: Both systems combine HFE with a low-volatility organic solvent. The solubility promoter of the organic solvent removes impurities while the HFE rinses them away. These are great for stubborn impurities like wax, adhesives, heavy oils, hot-melt glues, grease, and C-flux residues. The biggest difference between these two systems is that the solvent and rinsing agent are mixed together in a cosolvent and kept separate in a bisolvent.


Water-Based Cleaning Agents

  • • Ultrasound cleaning with water-based media offers practical solutions to electronics manufacturers. The electrical signals from the ultrasound influence the cleaning action for the cleansing agent. The lower the frequency, the more energy is released by sound waves. Cleaning tests will help you figure out the right combination of cleansing agent and ultrasound frequency.
  • • Carbon dioxide offers a nice dry alternative. Compressed carbon dioxide possesses excellent properties as a solvent on nonpolar impurities like grease and oil. With low viscosity and interfacial tension, supercritical CO2 has a strong capacity for penetrating crevices. This works well for small, drilled holes and other complex geometries. This environmentally-friendly, dry, residue-free procedure can clean complete PCBs and assemblies.
  • • The chemical, thermal, and mechanical properties of CO2 snow-jet cleaning removes surface films and particulate contamination without leaving residue. This type of cleaning can be used on contact points, in preparation for bonding processes, equipping PCBs and foil-PCBs, and manufacturing of metal-insulator semiconductors.
  • • Plasma is another medium used to clean electronics. The physical and chemical reaction during the cleaning procedure allows plasma to efficiently surface treat parts and components while cleaning away organic impurities like oils and grease and activate the surface. Depending on the application, low-pressure plasmas or inline-capable atmospheric pressure plasmas can be used.

For all water-based media, solutions will depend on your plant technology as well as the components that need cleaning. For other cleanroom solutions, like certification, validation, and modular construction, contact Gerbig Cleanrooms. Our experts understand compliance and electronic manufacturing: 888-628-0056; info@gerbig.com.

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