Comparisons with Competing Cleaning Technologies

• Differences from Other Cleaning Systems
• Aqueous and Semi-Aqueous Cleaning Problems
• Aqueous Cleaning Versatility
• Aqueous Cleaning and the Environment
• Cost Analysis on Aqueous Cleaning

A Summary of Differences with Other Cleaning Technologies

This is a big generalization, but in general when comparing a typical MicroCare vapor degreaser with a competing aqueous, semi-aqueous or hydrocarbon cleaning system, the competing systems will tend to be:

• much larger than the vapor degreaser while accomplishing the same cleaning task...
• more complex than the vapor degreaser to operate and maintain...
• Use more complex chemistries than the vapor degreaser to accomplish the same degree of cleanliness...
• Deliver less consistent cleaning than the vapor degreaser because the cleaning results from an aqueous system varies as the chemistry changes, while solvent cleaning is extremely consistent...
• require more intricate water handling systems (for both pre-treatment and waste-handling post-treatment systems)...
• be more expensive to operate and maintain than the vapor degreaser,
• consume more energy than the vapor degreaser,
• take up more floor space than the vapor degreaser, and
• clean more slowly than a similarly-sized vapor degreaser (slower through-put).

Aqueous and semi-aqueous cleaners are inherently less cost-effective than solvent cleaners because they use a more complex chemistry. It's very hard to produce good, consistent cleaning with an aqueous system.

Back to Top

Aqueous and Semi-Aqueous Cleaning Problems

There are many subtle issues here, and to simply say water is good or bad is to over-simplify a very complex issue. In fact, in many non-critical industrial cleaning applications, water may be the best choice.

In general, aqueous cleaning systems are used most often for (a) cleaning parts that are not very complicated in form (e.g., few blind holes or complicated geometry), or (b) the cleaning requirement is not very stringent; i.e., minor surface residue is acceptable, or (c) the parts are very large or the production volume is extremely high.

Simple metal stampings are a great example of a product which can be successfully cleaned in a aqueous system. A typical stamping is reasonably flat, thin and does not have any tight cavities or spaces into which the aqueous solvents could be trapped. A bare circuit board or a circuit board populated with only "through-hole" components would be a similarly suitable application.

So where does aqueous cleaning have problems?

Aqueous cleaning usually is not successful for one or more of the following reasons:

• Size & Spacing: Aqueous solvents typically have difficulty getting into and cleaning in and around parts that are extremely small or have extremely small spaces. Water has a very high surface tension that limits its ability to penetrate tight spaces (see "wetting index"). This can be somewhat ameliorated by additives in the water or higher pressures, but these work-arounds cause problems of their own (residues, damage, higher energy costs, higher acquisition costs).
   
• Effectiveness: Many common types of contamination are not soluble in water, so no amount of water, pressure and heat can remove them. Common work-arounds include more additives, higher pressures, and higher temperatures.
  
• Entrapment: If the water does manage to get into some tight spaces, how does it get out? It can often be difficult to get the aqueous cleaners out of tiny spaces, such as under a BGA component. Water also can be trapped in a filter, or locked inside a tiny female electrical connector. Symptoms of the problem include residues and corrosion. Typical work-arounds include extra processing, such as baking the products in ovens to drive the water out of the traps.
   
• Spots: Water often leaves unacceptable water spots. Common work-arounds include more additives to reduce the surface tension or enhance drying, more aggressive heating and powerful air knives. Less commonly, a final rinse in a solvent cleaner is often used (see: solvent drying).
   
• Compatibility: Water cleaning often is not suitable because some components or products are sensitive to the high pressures of water cleaning, the heat of washing and/or drying, or the minor surface residues mentioned above. There are no common work-arounds that can solve compatibility problems.
   
• Environmental Problems: Water cleaners require a great deal of water and electricity, and produce a continuous discharge of contaminated water. The most common work-around is an expensive water treatment system to be installed alongside the cleaning system itself. Aqueous systems require hard-to-get waste water discharge permits which can entail extensive paperwork and government oversight. For more details, see the FAQ pages about water cleaning and the environment.
   
• Costs: While water is usually cheaper than solvents on a per-pound basis, the costs of buying, installing and operating the machines can be far higher than a solvent-cleaning system. (see: Capital Costs and Operating Costs in this Learning Center). In addition, download the cost calculator to see how the total-cost-per-part-cleaned is calculated, and how it might change using MicroCare^® solvents.

Back to Top

Aqueous Cleaning Versatility

In general, solvent systems will be more versatile than aqueous cleaning systems. Let's look at the facts:

Effectiveness: The problem here is density. Many common types of contamination are not soluble in water, so no amount of water, pressure and/or heat can remove them. However, since the MicroCare cleaning fluids are much heavier than water they often can remove solid particulate (contamination that cannot be dissolved); the particulate simply "floats" off the surface, just as a ship floats on the ocean. For example, solder balls or metal finings are easily cleaned in MicroCare cleaning fluids. The platters and hubs inside disk drives must be perfectly clean; solvent systems easily remove the tiny particles of metal and/or oil that accumulate on those surfaces during manufacturing. Semiconductor makers also use solvents to clean wafers at different times in their processes.

Size & Spacing: The problem here is viscosity and surface tension. Because the surface tension of water is high, aqueous solvents typically have difficulty getting into and cleaning in and around parts which are extremely small or have extremely small spaces, such as the BGA chip, above. Because the surface tension of all the MicroCare cleaning fluids is low, the solvent is easily able to get in and around complex parts and tight-fitting spaces. This advantage is an inherent characteristic of solvents that no quantity of heat, high-pressure sprays and expensive additives can completely transcend. To learn more about this issue, click here for a discussion of the wetting index.

Entrapment & Spots: The problem here is the latent heat of evaporation. Suppose the aqueous cleaner has forced the water under a tight-fitting electronic component or into an ultra-narrow blind via. Because of its high surface tension and high heat of evaporation, water will resist coming out of such tiny spaces.

Another problem is spotting. Since water dries so slowly, it often leaves unacceptable water spots. In contrast, the MicroCare cleaning fluids will go into the spaces but, because they evaporates easily, will come right out – usually with no extra heating or processing. Solvent cleaning rarely, if ever, leaves spots because the solvent is quickly removed completely in the cleaning machine. These are inherent advantages of solvent cleaning.

Compatibility: Water cleaning often is not suitable because some components or products are sensitive to the high pressures of water cleaning, the heat of washing and/or drying, or the minor surface residues mentioned above. There are no common work-arounds that can solve these compatibility problems.

Back to Top

Aqueous Cleaning and the Environment

There is a perception that water cleaning is "green." That's an over-simplifcation of a very complex issue. In fact, in many instances, MicroCare cleaning fluids are a better choice environmentally because they offer a reduced carbon footprint. Let's look at the details:

Safe for Ground Water: MicroCare cleaning fluids should always be disposed properly; they must never be dumped onto the ground or into rivers. But aqueous cleaning systems have exactly the same problem. Once water is mixed with cleaning additives, oils, fluxes or other contamination, it too must be treated before disposal. But there is one crucial difference: MicroCare cleaning fluids are easily recycled and distilled inside the same machine that does the cleaning; it's an inherent part of the process. In contrast, water cleaning machines need complex and expensive additional filtration and treatment systems.

Renewable Resources: Aqueous cleaning systems need a lot of water (which is becoming scarce in some areas) and a lot of electricity (which is expensive and contributes to global warming). It takes a lot of floor space and technology to keep even a small aqueous system running. In contrast, the cleaning systems that use MicroCare cleaning fluids are simple. The use no water at all, and the smaller systems can run on household electricity. Even the big vapor degreaser systems use only a tiny fraction of the electricity required for aqueous systems.

Ozone-Safe: While it is true that old-style solvents depleted the ozone-layer, that is not true about today's technology. MicroCare cleaning fluids contain no free chlorine, so they do very little harm to the stratospheric ozone. This is generally considered a good thing. But the environmental story no longer ends with the ozone layer: global warming is a big issue.

Global Warming: MicroCare cleaning fluids offer a sustainable global warming potential or "GWP." The GWP index is a scale that ranges from one to 50,000 or higher, and measures the impact a chemical might have on global warming when compared to carbon dioxide. A lower GWP rating is better. There are a few chemicals with GWP ratings of 200-500. The MicroCare cleaning fluids generally rate between 300 and 1,500, which would be considered “moderate” and is a big improvement over old-style cleaners.

Aqueous systems use vast quantities of electricity, most of which is generated by the burning of fossil fuels, which directly related to global warming. This is a major drawback of aqueous systems.

Smog from Volatile Organic Compounds (VOCs): It turns out that almost all of the chemicals that are not global warmers have short atmospheric lifetimes (measured in weeks or months). These are called volatile organic compounds or "VOCs". This category of cleaners includes alcohols, ketones, hydrocarbons and many other classes of chemicals. Almost without exception these products are photochemically reactive and contribute to ground-level air pollution ("smog"). Because MicroCare offers such a wide variety of choices, MicroCare can help clients select the best choice for each region.

Back to Top

Cost Analysis on Aqueous Cleaning

Aqueous cleaning systems usually need to be very large to accomplish the cleaning and drying processes, and the water treatment system consumes even more floor space. In total, the equipment is much more expensive, consumes more energy, takes up more floor space, and takes longer to process parts than the typical the MicroCare cleaning system. So, when looking at the TOTAL COST PER PART CLEANED, a system using the MicroCare cleaning fluids often is less expensive to buy and operate.

Installation costs are a large part of aqueous systems. Up-front capital costs include the actual cost of the machine, freight, site preparation and set-up costs. Most engineers also include building renovations, ventilation enhancements, electrical upgrades and water-treatment subsystems required to support the new system. These expenses can be as costly as the cleaning machine itself, so be sure to include the facilities manager, health and safety people, environmental people and the fire safety team as well as the production people in developing these plans.

Engineers should include the cost of the funds that will be tied up in the machinery. With a spreadsheet, it's easy to use the "Payment" (PMT) financial function to estimate the cost-per-month of the equipment, which can easily be converted into a cost-per-part factor.

Another consideration is the cost of the space required by the cleaning machine and the support systems it requires. Almost without exception, aqueous, semi-aqueous and hydrocarbon-based cleaning systems require more floor space than solvent-based equivalents. Aqueous systems require water-treatment facilities which can be as large as the cleaners themselves. Aqueous systems also have slower cycle times, so more space is needed for work-in-progress, supplies, conveyor systems and access aisles.

The floor space requirement usually is described as a multiple of the physical size of the machine. A general rule of thumb is to multiply the basic size of the cleaning machine by a "footprint factor" of 4X or more. For example, an aqueous cleaner with a 200 sq. ft. "footprint" on the factory floor will require 800-1,000 sq ft. of total floor space (200 x 4 = 800). For vapor systems, the same 4X factor would be a reasonable rule-of-thumb, which doesn't seem to be a big deal except that vapor degreasers are an order of magnitude smaller than comparable aqueous cleaners.

To estimate floor space costs, use the "fully-loaded per-foot costs" for the space in which the system will be installed. This usually will be expressed as a "triple-net" rent per square foot. Included this number should be the cost of the space itself, plus heating, cooling and lighting costs, and some portion of the cost of shared facilities, like aisles.

Total one-time costs should be "calibrated" to reflect the productivity of the machine. For example, if the machine is planned to clean 100 parts per year for ten years, it will clean a total of 1,000 parts in its economic lifespan. The total one-time costs should be divided by the throughput (in this case, 1,000 parts) to calculate the true "total one-time costs per part cleaned."

MicroCare offers a handy spreadsheet which enables apples-to-applies cost comparisons.

Back to Top