Targeted Application-Specific Cleaning with IPA Wipers Simplified

This technical brief provides information on the optimal concentrations of isopropyl alcohol (IPA) in pre-wetted wipers for different cleaning applications. It also explains why different wetting levels are used in pre-wetted wipers to achieve optimal cleaning results.

Introduction: 

Pre-wetted wipers or presaturated wipes are products commonly used for contamination control activities in cleanrooms. They are a convenient delivery system that combines cleanroom wipers with the right amount of cleaning liquid—typically used to wipe down environmental surfaces, such as bench tops, counters, carts, trays, etc., that are not involved in product contact. In addition, you can use different pre-wetted wiper products to clean process equipment and surfaces that come into contact with the manufactured product. Some applications require the lowest linting and highest-performing wipes in the world’s most critical cleanrooms, labs, and other controlled environments.

Cleaning Liquid in Pre-wetted Wipers 

Isopropyl alcohol (IPA) is a commonly used cleaning liquid in pre-wetted wipers. It is readily available, reasonably priced, and has excellent soil removal capabilities, making it an ideal choice for cleaning. Most importantly, IPA evaporates entirely without leaving any residue on the surface. It is considered the universal wetting liquid for pre-wetted wiper products. However, verifying the quality of the IPA used by checking the product specifications and conducting testing, just like any other consumable, is essential. A high-purity IPA with extremely low ion profiles is necessary for the electronic industry.

In contrast, IPA must be free from viable or non-viable organisms for the healthcare industry, achieved through sub-micron filtration before wetting the wipers. It’s worth noting that filtration cannot remove dissolved ions. Therefore, you should use electronic grade IPA rated 99.5% pure or better as it offers the lowest level of all contaminants.

What is the Optimal IPA Concentration? 

Cleanroom operators often ask about the optimal concentration of isopropyl alcohol (IPA) for pre-wetted wipers. While there are many possible IPA concentrations, we only need to consider three: 6%, 70%, and 100% IPA. These three concentrations cover almost all cleanroom cleaning requirements. However, determining which concentration to use depends on the nature of the manufactured products and the surface to be cleaned.

Wipers for the Healthcare Industry 

The healthcare industry encompasses pharmaceutical and biotechnology products and services, medical devices, pharmaceutical compounding laboratories, and animal care products. These industries have a common requirement of keeping their manufacturing and support areas free from contamination caused by microorganisms such as bacteria, viruses, and fungi. A sanitizing solution is required to avoid contamination, and in the healthcare industry, a 70% IPA solution is the most effective. This solution comprises 70% isopropyl alcohol and 30% deionized water (DIW). The water content in the solution helps to penetrate the cell nucleus of microorganisms to kill them. However, it’s worth noting that 70% IPA solutions do not kill spores, and other treatment methods are available to deal with them. An added benefit of using a 70% IPA solution is that it reduces surface tension, making it easier to dissolve or remove soils and residues from surfaces. It’s important to note the flammable classification on pre-wetted wipers containing 70% IPA; therefore, you must handle, transport, store, use, and dispose of them carefully. For more information about the flammability of 70% IPA solutions, please refer to the flammability chart below.

IPA Wipes for Other Industries

The cleaning requirements for cleanrooms in microelectronics, aerospace, flat panel displays, hard drives, etc., allow for 6% IPA or 100% IPA solutions.

Wipes with a Low IPA Concentration 

Pre-wetted wipers with 6% IPA solutions are mainly used to clean environmental surfaces (as shown in the examples above). These surfaces are expected to get cleaned every day or shift, so they are unlikely to have accumulated significant contamination levels since their last cleaning. Therefore, pre-wetting wipers with 6% IPA are sufficient to remove and capture surface particulate matter into the wiper. The 6% IPA concentration ensures that the liquid acts as a bacteriostat, inhibiting mold growth in the product. It is also well below the 10% IPA concentration, which would require a flammable classification of the pre-wetted product. A 6% IPA concentration allows the product to be classified as combustible, which makes it easier and less costly to store and dispose of. The 6% IPA solution helps reduce the surface tension of the wetting liquid, but the wiping action is the primary mechanism for surface particle removal. Another advantage of using 6% IPA solutions is that it minimizes Volatile Organic Compounds (VOCs) in the cleaning product, which is essential for an organization’s environmental control department.

High IPA Concentrated Wipes.

Industries outside of healthcare also need to clean various surfaces, including product and production surfaces that come into contact with the product. Removing soils or residues at regular intervals is necessary to avoid product contamination. A pre-wetted wiper with 100% IPA is the best option for cleaning in such cases because it reduces surface tension and has a high cleaning power. The 100% IPA wetting liquid contains no water. It acts as a drying agent if any water on the surface needs cleaning, which is especially important in the semiconductor industry, where vacuum process equipment must always be free of water and water vapor. If the surface requiring cleaning can tolerate water, a pre-wetted wiper with 70% IPA can clean soiled surfaces.

Why Only Those Simple Few Options? 

Have you ever wondered why intermediate concentrations of IPA, such as 9%, 40%, or 85%, are not commonly used as wetting solutions? You must balance several factors simultaneously, including cleaning capability, flammability rating (as shown in the chart above), and the amount of Volatile Organic Carbon (VOCs).

Quick clarity about VOCs:

IPA stands for isopropanol alcohol, a substance containing carbon (along with hydrogen and oxygen). Because IPA evaporates so readily, it is termed volatile, and because it contains organic carbon, the EPA classifies it as a Volatile Organic Carbon or VOC. The EPA requires that all users disclose the quantity of VOCs from IPA (as well as from other volatile solvents) they use and discharge into the environment. The concern is that the VOCs become precursors for smog once released into the atmosphere. The greater the amount of IPA, the greater the VOCs, as shown in the graph below. Minimizing IPA concentration and usage will reduce overall VOC levels. Check with your local municipalities for any regulatory requirements for your area.

Packaging Options For IPA Wipers

IPA presaturated pouch wipers come in re-sealable, solvent-resistant packaging with wipers in a c-folded configuration for single withdrawal. The pre-wetted format in an easy-to-dispense recyclable canister provides a cost-effective and convenient option compared to traditional bulk handling of solvents. These types of IPA-pre-saturated wipers can reduce the mixing of chemicals, lower VOCs, and eliminate the inconsistent wetting and cleaning associated with wetting a dry wiper. Your packaging should reflect an increased efficiency for cleanroom and industrial operators.