The ever-increasing demand for reliability, continuing miniaturization, and the growing number of faults in electronic components manufactured in no-clean processes all combine to put the focus back on cleaning in electronics manufacturing. The industry offers a variety of solutions to finding the optimal cleaning process.
A key factor in achieving economy and efficiency in the cleaning process is the selection of a suitable cleansing agent. Selection criteria include the nature and quantity of the impurities to be removed, and the subject material. Cleaning agents currently used in electronics manufacturing include solvents, water-based media containing alkaline surfactants, and water-based tenside-free cleaning agents.
To ensure efficient and reproducible cleaning, it is essential to match the cleaning agent to the plant technology. That is why so many different cleaning systems are available, such as dipping plants with ultrasound or pressure flooding and spray cleaning plants. Solvents are used today in totally enclosed cleaning units.
Cleaning with compressed carbon dioxide provides an extension to the wet-chemical process. The term “compressed carbon dioxide” indicates CO2 that has been converted to liquid form (that is, into its supercritical phase) under pressure; in this form, it possesses excellent properties as a solvent upon a range of nonpolar impurities such as grease and oils. Supercritical CO2 has low viscosity and low interfacial tension, resulting in improved ability to penetrate crevices. This enables cleaning of components with highly complex geometries such as tiny drilled holes. In electronics manufacturing this technology offers the ability to clean such items as complete PCBs and assemblies, removing flux residues and cleaning away oils and grease from metallic components such as contacts. It meets the requirement for an environmentally friendly, dry, and residue-free procedure.
This cleanroom tip was taken from “Cleaning in Electronics Manufacturing” by Doris Schulz, which appeared in the June 2013 issue of Controlled Environments.
