THEY CALL ME THE “CLEANING LADY” because of my activities in optimizing industrial critical cleaning processes, but what is critical cleaning? Soil is often described as “matter out of place” and critical cleaning is the removal of matter out of place from the surfaces of high-value product. High value may mean high-priced, or it may simply mean that undesirable consequences can result from inappropriate surface residue or surface properties. While surface quality or surface attributes are theoretically separable from critical cleaning, in common industrial practice, all are considered together.
The community involved in critical cleaning is diverse, and each individual has his or her own experience-based views on the subject. Therefore, to provide readers of Controlled Environments Magazine with a broad perspective on cleaning issues, I selected nine individuals, all with extensive relevant experience. I asked them what they saw as the most important critical cleaning challenges over the next three to ten years. They had the option of commenting on anyor all of the following issues:
• competitiveand economic costs
Of our nine experts, four are directly involved in manufacturing and/or maintenance of critical product. One of those is in the military and another has a background in manufacturing and is now an independent consultant. We also included five vendor/suppliers. Three are involved in the manufacture and/or sales of cleaning products. Two are employees of companies that supply cleaning agents and/or metal-working fluids. In addition, this month’s “In and Out of the Cleanroom” column covers a few of our own thoughts about the futureof critical cleaning.1
Safety and Environmental
Safety and environmental considerations may not be uppermost in the mind of the fabricator, but they definitely influence the availability, costs, andperformance of both cleaning agents and cleaning processes.
“What’s driving the cleaning process? The environmental issues are huge,” explains Owen Briles. Owen, who now heads Briles Consulting Services Inc., Cherry Valley, IL, has extensive experience in the manufacture of aerospace components. Owen describes the difficulties of working with various lists of materials of concern, explaining that “large companies scrutinize all processes, including the cleaning process. We are constantly being asked: why do you have to use this? What else can you use? Each industrial site is given goals to reduce the use of environmentally-unfriendly material by a certain amount. If the site fails to reach the goals, it is rated lower by corporate. Asa result, we are driven to a small subset of possible options.”
Among chemicals of concern, Owen notes that reduction in the use of volatile organic compounds (VOCs) is a constant challenge. VOCs react with UV light to form tropospheric ozone, popularly referred to as smog, and they include nearly all organic compounds of interest. In addition, there is a concern with the use of cadmium and with hexavalent chromium. Recent announcements of low allowable worker exposure levels by OSHA have resulted in scrutiny of an array of industrial processes. Briles notes that there is an ongoing struggle to find a suitable replacement for hexavalent chromium on aluminum.
International directives, such as European Union’s “Restriction of Hazardous Substances” (RoHS), have increased the urgency to find substitutes for hexavalent chromium, as well as mercury, cadmium, chlorinated biphenyls, and polybrominated diph-enyl ethers, and lead. Owen points out that “we have been working for ten to fifteen years to find a replacement for lead solder in aerospace. So far, some replacements have been found. However, we have not found across-the-board, drop-in replacements for lead solders; so at least some processes will have to be modified.”
Environmental issues are also of concern in developing critical cleaning applications in the military. Dr. El Sayed Arafat is a chemist at the Naval Air Warfare Center (NAVAIR), Patux-ent River (Pax River), MD. As a member of JS3WG2, he faces the challenge of evaluating the suitability of alternative cleaning agents as environmentally-preferred substitutes for an array of processes for Naval Aviation applications.
El Sayed says his biggest challenge is “finding a cleaning agent that has the desired performance properties while at the same time meeting the safety and environmental regulations. This is becoming more and more difficult. If you change the composition of the cleaning agents to meet the environmental requirements, you are apt to introduce flammability and other worker safety issues.
“The VOC level will become a big issue, particularly with solvents. As with other environmental issues, the decreasing allowable VOC level is moving from the West Coast to the East Coast. PRF 680 has 800 g/L VOCs. California has a 25 g/L limit for most applications. Even on the East Coast, many states are lowering the allowable VOC level. As the VOC level is lowered, the choices become more limited and the costs increase.”
Greg Bruce is a Technical Service Chemist at LPS Laboratories in Tucker, GA, a formulator of lubricants and cleaning agents. Bruce sees the two major issues as environmental regulation and pricing in California and in the Ozone Transport Commission (OTC) states. “The two drivers are diametrically opposed. It is difficult to find chemistries that clean effectively, comply with strict regulations, and that are not too expensive for consumer use.” Bruce adds that the California Air Resources Board (CARB) continues to decrease the allowable g/L VOC in various products, seemingly on a daily basis. The OTC is a group of 13 states in the Northeast that are regulating chemicals contributing to poor air quality, including VOCs.
JoAnn Quitmeyer, Director of R&D at Kyzen Corporation, Nashville, TN, is involved in the formulation and development of an array of aqueous- and solvent-based cleaning agents. JoAnn is also of the opinion “that environmental issues will continue to be at the forefront as reduced VOC, COD (chemical oxygen demand), and BOD (biological oxygen demand) limits spread across the United States and around the world.” She adds that “government legislation dictates performance. Responsible chemical suppliers use the materials that best meet these regulations. More aqueous technology is being used. Where needed hydrocarbons are carefully selected for performance optimization. Users select formulated compositions that have the lowest VOC, COD, and BOD available without sacrificing performance.”
LPS’s Greg Bruce concludes that “common sense, sound science, and regulatory requirements must all intersect. There needs to be a happy medium, but where that is, I don’t know.”
Critical cleaning is sometimes referred to as
cleaning components that already look clean.
Economic Considerations and Consequences
Equipment and Chemical Costs
Art Gillman is President of Unique Equipment Corporation, a manufacturer ofcleaning equipment based in Montrose, CA. He sees cost-concerns as impacting the decisions of both small and large companies. “Right now, for solvent cleaning, the biggest issue is cost-containment.” Art explains that “not long ago, if you asked a customer how much solvent they used each month, they had no clue. That’s all changed now; and the motivation is not environmentalrequirements.”
Art goes on to explain that accountants are taking a more important role in a field that used to be dominated by design and engineering. In his opinion, in some cases, bad decisions are being made. “For example, an engineer may express a desire to clean with alcohol. Why? Because alcohol is relatively inexpensive. However, on asking for more details, we find that the contaminant is grease. If the alcohol does not remove the grease effectively,it becomes a very costly choice.
“Or, you get customers who are using exotic chemicals (i.e., expensive chemical blends). They are aware of everyounce that is lost. Therefore, our current concerns are about designing the primarycontrols around cost containment.”
Environmental initiatives, such as
RoHS, may necessitate additional
cleaning or rinsing.
George Parsons of Production Cleaning Systems LLC, Irvine, CA, represents manufacturers of cleaning equipment for solvent and aqueous processes; he also provides contract cleaning services. “To a large degree, we have systems that clean effectively, but all capital equipment is costly. Even small batch or in-line consoles for aqueous cleaning requirean investment of $30,000 to $40,000.”
While there is a potential for product damage, advances in ultrason-
ics technology will increasingly enable effective cleaning of delicate
George adds that “the amount of manufacturing that has fled the country is astounding. There are many advantages of moving from Southern California to Tijuana. The costs of operation decrease to 20%; and this includes wages and benefits. It also includes chemical and process costs.” George explains that a high-purity chlorinated solvent might cost under $10/gallon. However, to use the product, because of environmental constraints, there would be a substantial investment in capital equipment. A newer VOC-exempt solvent that would be compliant in California (many hydrofluorocarbons, HFCs, or hydrofluoroethers,HFEs) could cost easily twenty times more than a chlorinated solvent.
Labor and Automation
As Plant Manager at Western Hydrostatics, Riverside, CA, Patrick Maluso oversees both general and critical cleaning applications and exacting surface requirements for diverse materials of construction. “On an economic basis, labor is the most important consideration in cleaning applications.” Pat explains that the labor force will dwindle as baby-boomers get older and cleaning is an entry-level position. Therefore, there will be a demand for labor for cleaning applications. With people there are issues of moods, thequality of training, and ongoing compliance with process and process control. Who conducted the training course? Was the titration actually performed? Pat notes that “there will be a great impact on procedures and performance from the loss of experienced workers. The procedures may continually change and evolve. However, much of those changes are handed down in the productionenvironment without informing the person making the policies and procedures.”
While Pat indicates the importance of training, education, and documentation, he sees automation as the solution to the labor crunch. “I foresee more manufacturers adopting automated cleaning equipment. Automated equipment does not take sick days; automated equipment does not have attitude problems. Automation will also reduce worker’s compensation claims, thus reducing premiums. In terms of quality and cleaning standards, a more automated process is more readily benchmarked.” Pat concludes that “we can achieve greater efficiency only by eliminating worker variability. Automated cleaning willhelp to achieve both goals.”
Innovation and Process Control
As a perhaps desirable by-product of cost issues, George Parsons notes an increasing concern with water cleanliness and a growing enthusiasm for closed-loop aqueous systems. Removing the additional grain of hardness using a closed-loop system may add $15,000 to $25,000 to the equipment costs. However, George asserts that “for critical cleaning applications, some manufacturers have concluded that recently-recycled deionized water provides the best quality, control,and eliminates a significant amount of waste.”
“More and more users are screening viable candidate technologies in an effort to minimize the cost/gallon and/or cost/widget manufactured,” adds JoAnn Quitmeyer. She sees a number of approaches to process-oriented cost control. Chemical loss through evaporation and atomization can be reduced through temperature reduction and installation of demis-ters. Chemical carry-over or dragout can be reduced through appropriate parts fixturing, nozzle design and positioning,and curtains. Cleaning chemistries that reject or release soils can be regenerated for re-use. Last but not least, JoAnn notes the importance of identifying methods for optimizing contamination removal. Many of us would agree that an optimized cleaning process is essential for achieving both a quality productand cost-savings.
As a designer, Art Gillman also sees these demands as having a positive aspect. “Thecustomer is more demanding; the system has to do more for less money; and ithas to use less – less air, less water, less chemical. This is not necessarilya bad thing. I enjoy these demands. It forces me to think of the system as adesigner.”
Art adds that considering critical cleaning as part of the overall manufacturing and monitoring process can save money. “For example, one engineer discussed a requirement for three processes: gross contaminant removal, particle removal, and particle counting. It would be more effective and ultimately more economical to combine the particle removal and particle counting processes, recirculating the solutions until the component is acceptably clean.”
Costs and environmental considerations may influence acceptance of advanced cleaning technologies. Nathan Jonjevic, Manager of Operations at Adapt Laser Systems, sees achieving performance in a challenging regulatory and economic climate as influencing the manufacturers’ process consideration. Nathan explains that while laser technology offers specific performance advantages “for small, high technology companies, the benefits of laser technology must be weighed against its costs.” However, he notes that “controlling the effluent for anything that comes in contact with hexavalent chromium will become increasingly urgent as OSHA lowers the permissible exposure limit,” adding that laser cleaning can provide an important and effective tool in controlling the effluent.
As a consultant with a background in analytical chemistry, I am intrigued by the use of advanced, innovative techniques to control cleaning processes,to understand component surfaces, and to resolve contamination control problems.
Pamela Morrison, a hard disc drive ESD Contamination Manager, who is involved in the manufacture of microelectronics, reminds us that the basic tests can be the most useful. Pam views gravimetric analysis (nonvolatile residue, NVR) and particulate counting as the most useful cleaning metrics. She cautions that sensitivity and specificity must be related to value to the process and to costs. “The tests can always become more detailed, but there is always the cost tradeoff. In addition, some tests that speciate are destructive. In terms of particles, we could always look for nanoparticles, but there is still room for improvement in using the current tests. You need sufficient sensitivity that you detect potential failures; but there is no inherent value in sensitivitythat allows you to see everything in minute detail.”
While NVR and particulate analysis remain important, for some applications, JoAnn Quitmeyer sees the increased sophistication of Q.C. techniques and instrumentation as contributing to increased requirements for cleanliness and contamination control. “Allowed residual soil contaminants [are] being reduced as we are able to measure organic and inorganic materials in the ppm and ppb levels due to more sophisticated laboratory instrumentation. We also use high powered microscopes to visually identify residues at the sub-micron level. The use of non-destructive testingis increasing to ensure product quality during production.”
Given the environmental regulatory and economic drivers as well as requiredstandards, it is all too easy to ignore the fact that the ultimate goal of critical cleaning is to achieve surfaces with the appropriate characteristics and attributes and, ultimately, to have a product that performs reliably andto customer expectations.
El Sayed Arafat summarizes, “If it doesn’t clean, it’s notuseful.” He adds that “there are many performance variables and thesevariables are highly application-dependent.” For example, PRF 680, a commonly-usedmilitary designation for a hydrocarbon-based cleaning agent, is an importanttool for contamination control where corrosion protection is an issue. “However,the mineral spirits in PRF 680 deposit a surface residue. This residue may beunacceptable for other applications.”
Pam Morrison’s charter, and her biggest challenge, is to find effective cleaning and contamination control processes for components that are becoming increasingly small and more fragile. Pam explains that “there is a need for cleaning and the status quo simply won’t cut it. Some people favor simply using more aggressive cleaning agents. It’s not that simple. The issue is not simply stronger cleaning; it’s better cleaning.
It’s the cleaning process, not just the cleaning agent. For example, withultrasonics, you can’t just aggressively clean. It would be great if youcould just turn everything up and make the product cleaner, but there is a potentialfor product damage.”
Pam adds that “cleaning, contamination control, materials change, and engineering metrics all have to be considered together; and they have to be considered at all stages of product build. The issues have to be balanced. For example, it does no good to achieve a cleaner product, only to find that the electrical properties have been compromised by the process change.”
New Contaminants and Process Control
The interaction of environmental and performance requirements are apparent to many in the field. JoAnn Quit-meyer notes that at the same time as environmental requirements are increasing (and, in part as a result of changing environmental requirements), soils are becoming more challenging to remove. Typical soils that she sees as challenging to clean include synthetic lubricants, mold-releases, adhesives, and lead-free solders. She adds that parts that were not cleaned now must be processed. Examples included cleaning of “no-clean” fluxesand increased cleaning required as lead-free solders are introduced.
JoAnn adds that as soils become more complex and more sophisticated, techniques to increase bath-life will continue to be adopted. “Bath skimming and filtration are techniques used to remove contaminants from cleaning solutions. Very few machines are being built today without some means of routinely removing contaminants.” She also voices the concern that the devices to enhance bath life require routinemaintenance, “something many users fail to do.”
Challenges of Aqueous Cleaning
Aqueous cleaning is useful for many, but not for all, applications. El Sayed notes that, “it’s good to switch to aqueous where possible; butsometimes, we need solvents for performance.”
Owen Briles views the loss of halo-genated solvents as a problem. “I have not changed my opinion that water is not a good solvent for all applications. I don’t see a good substitute for halo-genated solvents. n-propyl bromide (NPB) has been a good substitute; I don’t know if it will be environmentally acceptable. Flammable solvents work, but process control is more complex, so the process becomes more cumbersome. We use a hydro-fluoroether. It is exceedingly costly; so much so that the use has to be justified. Typically, such products are used in small systems; and, without additives, most suchsolvents do not effectively dissolve soils of interest.
My biggest concerns with aqueous cleaning are involving solubility, achieving adequate drying, and the potential for corrosion. To achieve sol-ubility for many contaminants, you need organics. Without adequate drying, residual moisture can be trappedbehind a component or a liner; and you detect corrosion later.”
Pat Maluso has successfully used aqueous cleaning for years. “I don’t enjoy aqueous cleaning, and this may surprise you.” I was a bit surprised because Pat and I had presented a report outlining his successful process change.3 “I’m still enthusiastic about water; but I don’t enjoy cleaning with water. The drying issue still remains to be resolved.” Echoing George Parson’s comments, he adds that “industry will have to deal with an abundance of dirty water, by reprocessing for reuse or for disposal,particularly if energy costs continue to climb.”
The Flat Earth Society
To assure a smooth transition when critical cleaning processes are being developed, we often suggest that our clients develop a cleaning team. A non-inclusive list of team members would include engineering, operations, management, facilities, Q.C., and safety/environmental. However, teams are not a substitute for rationality. Art Gillman points out the problems resulting from decision by committee. “The members are focusing on costs, not on performance. This happens in the selection of solvent and aqueous processes. Even for simple aqueous equipment, the initial cost of equipment may be considered, without thinking about the over all operating costs.” Art concluded that, “In decision by committee, consensus is easy; analysis is harder.”
Pat Maluso sees a need to modifying the paradigm of maximizing immediate return to the company and the stockholder. “Businesses will wise-up. In the next three to ten years, corporations will develop goals of greater productivity and of increased company growth.” He adds that “it makes no sense to make a profit today without investing in the company infrastructure. Without long-term investment in performance, there may be no company; all of theworkers will be out of a job.”
We have views regarding critical cleaning provided by nine people with knowledgeand practical experience in the field of critical cleaning. Obtaining and assembling their comments was valuable, because given the disparity of their fields and for a variety of other logistical considerations, this is perhaps the only way that readers of Controlled Environments Magazine may have to compare and contrast their thoughts. As might be suspected, the interaction of the performance/contamination control, economic, and safety/environmental considerations is likely to increase. Because performance is a given, it also appears to me that we face many challenges in additional development of new critical cleaning processes and in integration of those processes into the overall manufacturing environment. Hopefully you, the reader, will have acquiredfood for thought as you assess your own critical cleaning requirements.
1.Kanegsberg, B. and E. Kanegsberg, “Cleaning Challenges,”Controlled Environments Magazine, October, 2006.
2.Kanegsberg B. and E. Kanegsberg, “Joint Services Solvent Substitution Working Group,” Controlled Environments Magazine, April, 2006.
3.Maluso, P. and B. Kanegsberg, “Hydrostatic Pump Rebuild: Implementing Aqueous, Steam, and Solvent Free Processes,” presentation, Tenth Annual International Workshop on Solvent Substitution and the Elimination of Toxic Substances and Emissions, Scottsdale, AZ, September 13 – 16, 1999.
Barbara Kanegsberg is an independent consultant in critical cleaning,surface quality,and contamination control.Her projects include an array of areas such as microelectronics,aerospace, and medical devices.She can be reached at BFK Solutions LLC,310-459-3614,Barbara@bfksolutions.com;www.bfksolutions.com
Photo credit:Photos courtesy of BFK Solutions, LLC (David Kanegsberg,photographer)