Learn how you can realistically predict how much the cost of cleaning will be for your company by not just focusing on how much a cleaning agent costs per gallon, but by looking at the dollar cost per square foot of board surface being cleaned.
Figure 2B: Schematic of a typical inline cleaning process.
Figure 3B: Overall costs in U.S. dollers per board.
Figure 1: Board valve versus failure rate: cost effectiveness of cleaning.
Cleaning processes in the electronics manufacturing industry are driven by two main factors: the achievement of cleanliness requirements and the optimization of economical efficiency. The only true method of analyzing a cleaning process is to use a systematic approach that analyses the cleaning process in regard to its four main criteria: substrate being cleaned, contamination being removed, cleaning agent and cleaning equipment used.
A realistic reflection of the cleaning cost as such can only be the dollar cost per square foot of board surface being cleaned and certainly not just the cost per gallon of cleaning agent. This analysis is based on customer requirements and outlines important factors to consider when analyzing a typical inline spray-in-air cleaning process. This analysis evaluates the true price of assembly cleaning for different chemical technologies commonly used today. This summary can and should be used to optimize existing processes by determining the overall process costs and by supporting the customer in minimizing them.
Is Cleaning Cheaper Than Not Cleaning at All?
As the packing densities of electronic boards increase and the long-term functionality aspect becomes more critical, so too does effective cleaning that should ensure the full functionality of the electronic assembly during its expected life cycle. As a result, the choices between various cleaning systems that directly impact the final cleaning result become very critical.
In high-end applications, the quality and long term reliability of the final product are usually more critical than the costs related to the cleaning process itself. The associated production costs per board are usually of secondary importance when considering the consequences of endangering the lives of human beings. This is in strict contrast to a contract manufacturing environment, in which the costs per assembled product are the primary driving force and far easier to manipulate and optimize since the failure of a home PC or other consumerable product is not as critical.
Sometimes, factors that we describe as hidden costs of cleaning are also difficult to quantify. This is due to the fact that variables, not directly measurable or immediately quantifiable in terms of the cleaning process, may manifest themselves only at a later point in time. Therefore, is cleaning cheaper than not cleaning at all? The answer simply depends on the relation of common failure rate in respect to the board, the end product value or the application. For most high-end electronic processes, cleaning is indeed the cheaper alternative (see Figure 1).
Inline Processes Up Close
In this article, only the latest type of conveyorized systems, namely water-based medium to high pressure spray-in-air with no flammability issues, will be taken into account. Most inline processes are water-based only solely to remove water-soluble fluxes and residues from different assemblies (see Figure 2 page 17). However, as much as 40 percent of all other inline based applications do require cleaning agents due to the inability to effectively remove the contamination (i.e. no-clean, lead-free residues).
The Cleaning Technology as The Key Process Parameter!
The cleaning process and the costs associated are partly impacted by the choice of the cleaning agent. For modern water-based medium to high pressure spray-in-air systems, a user generally has a choice of three different cleaning agent technologies: traditional surfactant-based cleaner (SBC), alcohol-water blend (AWB) based cleaner and micro phase technology-based cleaner (MPC). The associated process limitations required more advanced technologies due to new and more demanding applications. The latest technology takes the aforementioned product as well as process shortcomings into account and allows for wide process windows at significantly reduced, overall process costs.
The components of a traditional surfactant based cleaner attach themselves to the surface of the substrate and through surface tension reduction, remove the contamination from the surface of the substrate. The main characteristic of this type of product is that the active components of the cleaning agent are continuously depleted in the cleaning process and therefore, the cleaning results vary constantly. Bath replacement on a weekly or bi-weekly basis is usually required.
In an alcohol-water blend type cleaner, the components of the cleaning agent solubilize the contamination from the surface of the substrate. The main characteristic of this type of cleaner is that the active chemical components are not used up in the cleaning process; however, the cleaning medium becomes loaded with contamination over time. In other words, it has to be replaced.
In contrast, a micro phase cleaning technology is water-based with unique active ingredients that combine the advantages of traditional solvents and surfactants without their drawbacks. This distinctive active phase removes the contaminants from the substrate surfaces and transfers them to the surrounding aqueous phase. There the contamination is not soluble and can easily be filtered out of the cleaning bath. Due to this unique property, the contamination can be easily removed, thereby allowing the cleaning medium to be continuously regenerated.
Why Can’t I Generalize and Simply Compare?
The unique characteristics mentioned in the paragraph above significantly affect the overall economic picture, and in the case of high-end, high reliability applications, it determines the cleaning quality. It is therefore suggested that potential users evaluate the cleaning result prior to specifying the desired equipment at a stage where other “consumerable” items are specified.
The degree of removability oftentimes determines the effectiveness of both the machine and the cleaning agent. Even though watersoluble flux residues are theoretically easy to remove with DI-water, the water oftentimes cannot adequately penetrate small spaces due to its high surface tension. It is therefore already anticipated in the near future, that DI-water will not be sufficient anymore to clean water-soluble fluxes under tight component spacings, and thereby defeats the original purpose of this type of flux.
The Real Cost Factors Are…
To effectively analyze and compare different cleaning processes in more detail, the user has to take into account all the elements of pure cost associated with cleaning and rinsing agent usage as well as the associated hidden costs for disposal, power usage, compatibility, equipment maintenance, etc. Recently, due to stricter budget control and cost cutting efforts, most companies and especially production managers assessed that costs per board do include more than simply the per gallon cost of cleaning agent.
The cost calculation (see Figure 2A) was based on process information available for medium to high throughput in inline cleaning processes. Because many different brands and models are available worldwide and the unique properties of each individual model, the authors argue that a fair average of the cost data available should be the most appropriate reflection of average values. Five factors that should be considered when trying to determine how much a particular cleaning process will cost are:
1. Cleaning and Rinsing Agent Costs
The concentration and cost per gallon of cleaning agent for the three cleaning systems respectively were determined as follows: surfactant (15 percent at $ 22.8/gal), alcohol-water blend (30 percent at $27.28/gal) and MPC Technology (15 percent at $54.56/gal). Interesting to note is that the cost breakdown of bath change, drag out and evaporation showed that the evaporative losses are the most significant portion of this cost position as reflected in blue in Figure 3B.
2. Consumable Costs
As mentioned above, the cost of the cleaning media is mainly dependent on the technology and whether or not the active cleaning components are depleted over time. This then has direct effects on the number of barrels purchased and their respective shipping costs. All values that were determined as part of this study are based on experimental results through a statistical process sample in excess of five brands and 10 distinct inline processes installed worldwide. This survey was conducted over a period of two years and reflects consistent implications.
3. General Operating Costs
The elements of this cost are floor space costs, electrical costs and personnel costs (operator, maintenance, etc.).
4. Environmental Costs
These costs deal with the disposal of the spent cleaning agent. A bi-weekly bath change was assumed for a surfactant-based cleaner, a monthly bath change for the alcohol-water-blend based cleaner and no bath change was assumed for the MPC based cleaning agent.
5. Equipment Investment/Depreciation
This calculation was based on a total investment of $200,000 of inline equipment and a $30,000 water-treatment system.
For the equipment investment, factors to consider are: equipment build quality, lifetime expectancy, maintenance requirements, ease of maintenance and availability of spare parts. The effectiveness of the cleaning agent and, increasingly, the environmental impact of the cleaning agent, are the main determining factors. The consumable costs are primarily driven by the throughput and cleaning agent cost per percent concentration. The maintenance costs are primarily determined by the cleaning agent as well as its compatibility with the equipment itself. The transport, storage and environmental costs are also primarily driven by the cleaning agent selection.
Conclusion
Cleaning costs are quantifiable and an optimal solution can be found by utilizing the framework and concepts outlined above. Initial steps to process cost reduction are: • Examine all your process parameters • Request cleaning trial reports • Evaluate all available process alternatives • Implement improvements and start saving valuable resources
For many, the complexity of each individual process becomes quickly apparent. For each user, proper process support such as hands-on cleaning demonstrations, explanation of process limitations as well as ample assistance in topics such as specific and economic requirements are of utmost importance.
Executive Vice President of ZESTRON America, Dr. Harald Wack has been with the family held business most of his professional life. He received his M.S. and Ph.D. in Organic Chemistry from the Johns Hopkins University in Baltimore, MD. He has 17 years of global experience in the electronics manufacturing industry, and five ye a rs in academic research related to asymmetric catalysis. Dr.Wack holds numerous patents, over 10 scholarly publications as well as 10+ industry publications on topics related to precision cleaning. He is also active in various industry organizations and technical forums such as the IPC and SMTA. He can be reached at (703) 393-9880.
Umut Tosun, M.S.Ch.E is the Application Technology Manager at Zestron America. As an active member of the SMTA and IPC organizations , Tosun has presented a variety of technical papers and studies on topics such as “Lead-Free Cleaning” and “Climatic Reliability.” Tosun received a B.S. and M.S. degree in Chemical Engineering from the Technical University of Hamburg, Germany, and has been with Zestron America since 2000. He can be reached at (703) 393-9880.
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