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Measuring the Cost per Cleaned Part
December 31, 1969 |Estimated reading time: 3 minutes
By Harald Wack, Ph.D., ZESTRON
Cleaning processes in the electronics manufacturing industry are driven by two factors: achieving cleanliness requirements and optimizing economic efficiency. The only true method of analyzing a cleaning process is to use a systematic approach that analyzes the process with regard to four criteria: substrate being cleaned, contamination being removed, cleaning agent, and cleaning equipment.
A realistic reflection of cleaning cost can only be the dollar cost per square foot of board surface being cleaned, and not the cost per gallon of cleaning agent. Comparing the price per gallon is a mistake that many users make. Most "cheaper-by-the-drum" products have severe drawbacks, and at the end of the year, are more costly overall. This means that potential users must calculate the cost per cleaned part. As a result, users should ask for cost comparisons with detailed process costs divided. This is of particular importance for conveyorized in-line systems due to large sizes and throughput.
To analyze and compare different cleaning processes effectively, the user must account for all elements of pure cost associated with cleaning and rinsing agent usage, as well as hidden costs for disposal, power usage, compatibility, equipment maintenance, etc. Due to stricter budget control and cost-cutting efforts, most companies especially production managers are taking a closer look at overall economics. In a recent study based on processes with medium- to high-throughput operations, 1.3 million boards were used as the denominator to calculate the overall cost per cleaned part annually. Due to different brands of equipment available worldwide and the unique properties of each individual model, it can be argued that a fair average of the cost data available should be an appropriate reflection of average values.
Cleaning and rinsing agent costs the concentration and cost per gallon of cleaning agents for three different cleaning products were gathered. It should be noted that the cost breakdown of bath change, chemistry drag-out, and evaporation show that the evaporative losses were the most significant portion of this cost position.
General operating costs elements of this include floor-space costs, electrical costs, and staff (i.e. operator, maintenance).
Environmental costs users often are confronted with questions related to waste-water management. This includes both used product and drained effluent. A bi-weekly bath change, for example, was found for one product; for others, less-frequent changes were determined. Elements of this cost factor also include mixed beds and carbon filters for the drained effluent. The main effect on the carbon beds are the organic contents of the cleaning agent that are dragged into the rinse water and adsorbed. The main effect on the anion and cation beds is the polar-ionic contents of the rinse water. The relative cost of carbon and mixed beds was subsequently calculated. As mentioned, the cost of the cleaning media depends on the technology and whether or not the active cleaning components are depleted over time. Therefore, this has direct influence on the quantity purchased and their respective shipment costs. All values in this study are based on experimental results from various installed inline processes worldwide.
Equipment investment/depreciation this cost factor was determined by averaging investment costs of currently available equipment. The cost was divided by 5 (for a 5-year depreciation), and then divided by the number of annual boards processed. As a general point of reference, equipment investment factors include equipment quality, lifetime expectancy, maintenance requirements, ease of maintenance, and availability of spare parts worldwide. The effectiveness of the cleaning agent and its environmental impact can become determining factors. Each partial cost factor for these factors was then added to produce the final cost per cleaned part. The cost for one cleaned board calculated in this study ranges from $0.27 to $0.37. This represents a 37% cost deviation, depending on the cleaning agent technology used in all three cases.
ConclusionCleaning is an important value-added piece of the electronics manufacturing process. It affects cost, although significantly less than the costs of solder paste, for example. Cleaning costs are quantifiable and can eliminate board failures that usually price at 100X the cost of the board. For many, the complexity of each individual process quickly becomes apparent. For each user, proper process support is of utmost importance. This provision can, for example, include hands-on cleaning demonstrations, explain process limitations, and ample assistance in topics such as specific technical (i.e. cleanliness specifications and/or long-term reliability) and economic requirements. SMT
Harald Wack, Ph.D., an SMT Editorial Advisory Board member, is executive vice president and CEO of ZESTRON America. Wack has authored and published several scientific articles, and has provided technical information for various publications. He received his doctoral degree in organic chemistry from Johns Hopkins University. He may be contacted at (703) 393-9880; h.wack@zestronusa.com.