When it comes to selecting a new cleaning process, I feel sorry for the poor production engineers. Engineers are always expected to clean more boards while using less machinery, water, electricity and money. It is a tough bind, for two reasons.

First, electronic circuits are getting smaller and denser, which makes cleaning the circuit boards difficult. The boards feature many different types of contamination, including fluxes, glues, inks, epoxies, fingerprint oils and conformal coating residues. Usually, the cleanliness standard is very high, which makes the analysis even more difficult.

At the same time, manufacturers around the globe are being asked to change their processes to protect the environment.

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Air, water and soil issues
Some of the world’s most polluted cities are in India, according to the World Health Organization, and Kolkata ranks No. 2 in the World Pollution Index. But India is not the only country with environmental problems:

1. In the Philippines, there are nearly 5000 premature deaths each year due to respiratory and cardiovascular diseases from exposure to poor air quality.

2. In Jakarta, more than 300 million cubic metres of water are pulled from aquifers each year—about three times the rate of replenishment. Indonesia is bound to face a serious scarcity problem within three to five years unless an immediate action is taken to conserve water.

Fig. 1: Sports scoreboards
Fig. 1: Sports scoreboards

3. In Vietnam, only 4.26 per cent of all the industrial sewage and waste water is treated before being released.

4. Simple energy efficiency should be a goal everywhere. But Switzerland produces $9293 of domestic output for every tonne of CO2 released into the atmosphere whilst Thailand produces only $760/tonne and India produces $579/tonne.

This is not sustainable. Sooner or later, businesses will be required to pollute less and become more energy-efficient. In terms of cleaning circuit boards, the new requirement is for a cleaning process that is effective, consistent, versatile, safe, fast, sustainable and affordable.

A number of companies around the globe offer innovative, affordable and effective circuit board cleaning systems that minimise pollution and costs. But capabilities and costs of cleaning systems can differ dramatically. Look at just two contenders: water cleaning versus solvent cleaning. Aqueous cleaners are relatively slow but inexpensive, while vapour degreasers are fast but require expensive solvents. How can an engineer compare these disparate technologies in a fair and meaningful manner?

The answer is to use a procedure that balances the benefit of each option against its costs. We call it the ‘cleaning scoreboard.’

The cleaning scoreboard
When people talk about football, basketball or other ball games, the final score pretty much says it all. The same is true with electronics cleaning. Engineers can develop a cleaning ‘score’ that compares all the different cleaning technologies—aqueous cleaners, semi-aqueous cleaners, hydrocarbon cleaners and vapour cleaners–and makes meaningful comparisons between dissimilar systems. The best cleaning score is the lowest total-cost-per-part-cleaned (CPPC).

Fig. 2: Parts in a basket. Every cleaning scoreboard needs to be tailored to the task at hand. For example, cleaning large metal parts with simple shapes is an easy application that might be handled nicely by an aqueous or hydrocarbon cleaner. Conversely, as parts get smaller or more complex in their shapes, vapour degreasers have a performance edge
Fig. 2: Parts in a basket. Every cleaning scoreboard needs to be tailored to the task at hand. For example, cleaning large metal parts with simple shapes is an easy application that might be handled nicely by an aqueous or hydrocarbon cleaner. Conversely, as parts get smaller or more complex in their shapes, vapour degreasers have a performance edge

CPPC is a number, ranging from hundredths of a rupee to hundreds of them. This score summarises all of the direct cleaning costs, environmental inputs, labour costs and waste disposal costs into one simple question: how much does it cost to clean a single part? This cost becomes the tool that allows the savvy engineer to compare totally different cleaning technologies fairly.

So here’s the crucial teaching of this report: stop caring about prices. It is not the ‘rupee-per-litre’ that really matters; it is the ‘total-rupee-per-part-cleaned.’ That is where profits will be made or lost.

For the purpose of this discussion, the cost-per-part-cleaned rating is the most practical. However, customers may prefer cleaning-cost-per-day or cost-per-shift as an equally effective metric of efficiency. In general, boards-per-hour is optimal for most companies because most of the other operational expenses are either recorded as hourly numbers or can be easily converted into hourly costs.

Take a practice swing
When buying a new baseball bat, tennis racquet or golf club, people select the one that fits their strength, size and swing. Similarly, cleaning machines come in all different sizes and with varying features. It is important to select the cleaning system that best fits the company’s cleaning application. This requires a four-step process.

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Size. The first parameter is size. If a system is too small, there will be a backlog. If the system is too large, it will be sitting idle, which is money wasted. The ‘fit’ of a cleaning system is judged by its throughput, measured in boards-per-hour.

As an example—a batch aqueous machine that cleans 20 boards in 40 minutes has an average throughput of one board every two minutes, which means about 30 boards per hour. A batch vapour degreaser that cleans only five boards at a time but cleans them in five minutes, will have a throughput of 60 boards per hour.

Throughput affects operating expenses dramatically, especially as cleaning systems reach their operational limits. For example, a small, latest vapour degreaser should have solvent losses that do not exceed about 20 grams per hour. In standby mode, this drops to about 4 grams per hour. To compute total cleaning costs, engineers will need to estimate how many hours each day the system will be cleaning and how many hours the system will be idle.

Many factors affect throughput. For example, systems that need to pause while warming up will have longer cycles. Complex loading and unloading processes also delay the cycle. Drying times may delay cleaning cycles. Water-based machines often cycle quickly when cleaning large, simple shapes; vapour systems are faster when cleaning tight spaces or components with many voids.

 

Checklist of cleaning costs

Operating costs
1. Labour: Operator cost per hour (fully-loaded labour rate)
2. Electricity
3. Water, solvents or saponifiers
4. Consumables (filters, etc)
5. Water-treatment system consumables
6. Waste disposal

Indirect operating costs
1. Labour: System maintenance cost per hour
2. Floor space cost per square metre
3. Training of operators
4. Supervisory staff
5. Lighting, ventilation and other services

One-time capital costs
1. Cost of buying the cleaning system
2. Freight, duties, customs fees and insurance to get it delivered
3. Site engineering and architectural planning costs
4. On-site construction
5. Electrical changes
6. Water/plumbing changes
7. Ventilation changes
8. System setup and configuration (delivery)
9. Cost of capital

Performance. Engineers should explicitly define the level of cleanliness required and then ensure each system can achieve that requirement. Simple visual inspection may be sufficient in many instances; surface insulation testing may be essential for more demanding applications. Whatever the standard is, define it before the testing stage.

Convenience. Engineers must consider where the cleaning will occur. For example, benchtop machines are slow, small and cheap, so it’s easy to have them conveniently scattered around the plant. Centralised high-volume systems are larger, more capable, more efficient and more expensive, but technicians waste time taking PCBs over to the centralised cleaning system. Convenience is complex.

Test and verify. Lastly, it is essential to conduct real-world tests of the systems. Prepare a batch of products with typical contamination loads. Have each system manufacturer run them through their cleaning systems. Double-check to ensure that cleaning did not degrade components or leave residues in hard-to-reach locations. Each equipment manufacturer should be able to produce a brief written report describing the process, results, fluids, temperatures and times. Disqualify any system that cannot clean successfully.

At this point in your equipment search, the above four criteria should produce a short list of cleaning systems that fit your company’s requirements. Now comes the hard part: determining which system will produce clean parts at the lowest total cost.

Three types of costs
Once the throughput has been defined, the engineer must research the direct operating costs, the indirect operating costs and the fixed costs for each alternative. Direct operating costs include the cost of consumables and labour required by the cleaning system when it is operating. Importantly, when the machine stops, so do the costs. Direct costs are directly proportional to throughput.

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Indirect costs are those costs that occur even when the machine is not cleaning, such as rent and training.

Fixed costs are usually one-time installation capital costs.

Let’s take a look at each of these costs:

 

Cleaning scoreboards

There are many different types of sports scoreboards, but they all summarise the performance of the players and indicate who performed the best on that particular day. Engineers also need a scoreboard, to help compare the different types of cleaning systems.

There are four main types of cleaning systems used in electronics assembly—aqueous systems, semi-aqueous systems, hydrocarbon systems and vapour degreasing systems—and they vary widely in size, performance, operating costs, labour costs and more. A clever cleaning scoreboard helps engineers decipher these complexities and make apple-to-apple comparisons of very different types of machines.

Direct operating costs. Electrical costs are a big issue for most cleaning systems. Typically, the total electrical costs of an aqueous system are five to ten times the costs of a vapour degreaser due to the need to heat the water, pump the water, spray the water and dry the water. Waste-water treatment systems are also very energy-hungry.

Fig. 3: Vapour degreaser in laboratory
Fig. 3: Vapour degreaser in laboratory

Water is cheap to buy but expensive to re-purify. Solvents and saponifiers can be expensive and are subject to drag-out. (Drag-out is wasted cleaning fluid that is trapped inside or around the parts as they are removed from the cleaning system.) Vendors should be able to estimate fluid consumption based on the sample parts provided to them.

Big machines have big maintenance problems, and large aqueous systems have the most complexities. Filters must be checked and replaced. Blowers, motors and conveyors must be maintained. Complex water-treatment and recycling processes must be monitored. Alkaline additives boost the cleaning power of many systems; these additives coat the machine’s interior and cause additional maintenance problems. All of these should be included in the system’s direct operating costs.

Labour costs should be carefully tabulated. Most of the labour is involved in loading and unloading the systems, which is pretty straightforward. Also look for time wasted by technicians in performing auxiliary inspections, such as hand-spraying, re-cleaning or hand-drying products outside the machine. In today’s world, manual intervention should be rare. If it is not, something is wrong. To measure hourly labour costs, many companies use fully-loaded labour rate for the technicians who will operate the system.

Indirect costs. Indirect labour can be difficult to measure. This might include the cost of a supervising engineer’s time, the cost of training, the hourly cost of maintenance technicians and the cost of any chemical safety training. If employee turnover is a problem, add additional funds for quarterly supplemental training.

There is an essential element to indirect labour that is often ignored: the complexities of managing water-based cleaning systems require many hours of well-trained, experienced technical experts. Their time is spent managing the water purification systems, the pH and additives of the water in the system, and the resulting waste-water treatment systems. The commitment in engineering required to operate a water system properly typically results in ongoing costs that far surpass those of vapour systems.

Another indirect cost is floor space, and sometimes a large one. Aqueous and semi-aqueous systems require more floor space than solvent-based systems and water-treatment facilities. These systems can be as big as the cleaners themselves. They also have slower cycle times, so more space is needed for storage, work-in-progress, supplies, conveyor systems and access aisles.

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For example, I have seen an aqueous cleaning system that used 20 square metres of floor space in the factory. But the system actually consumed 140 square metres of floor space when work-in-progress and ancillary systems were included. That is a seven times floor-space factor (140 sq.m/20 sq.m). For comparable vapour systems, which are smaller with equivalent capacity, a 4x factor would be reasonable.

To estimate floor space costs, include the cost of the space itself, plus heating, cooling, lighting, and some portion of the cost of shared facilities like the lavatories. Assuming factory space in India rents for about 1000 rupee/sq.m/month, the cost of the large aqueous cleaner cited above would be approx. 136,600 rupees per month. If the system cleans 10,000 parts per month, that adds 13.6 rupees to the cost of each part cleaned.

Fixed acquisition and installation costs. The final costs to include are the fixed and acquisition costs.

Up-front capital costs should include the costs of the machine and sub-systems, freight, site preparation and setup, building renovations, ventilation enhancements, electrical upgrades and water-treatment subsystems required to support the new system. It is essential that all of the sub-systems are included in the cost analysis.

Savvy engineers also consider making extra investments in optional features that speed cleaning or reduce costs; trading up-front capital investment for lower operating costs. For example, aqueous systems have money-saving options such as air-knives and extra drying chambers that speed cleaning but increase electrical consumption.

Planners should include the cost of the funds that will be tied up in the investment. Use the payment financial function in a spreadsheet to estimate the cost-per-month of the equipment, which can easily be converted into a cost-per-part.

Once the total purchase and installation costs are determined, divide that cost by the total number of parts expected to be cleaned by the system over its operational life. For example, a large 10 million Indian rupees cleaning system might be expected to last 12 years and clean 10,000 boards/month. In that case, the cost-per-part-cleaned is about 6.94 rupees.

Fig. 4: One of the smallest vapour degreasing systems—the Unique Lab-Kleen degreaser—engineered for prototype labs, R&D and pre-production applications
Fig. 4: One of the smallest vapour degreasing systems—the Unique Lab-Kleen degreaser—engineered for prototype labs, R&D and pre-production applications

The winning score
As we have seen, there are many factors to tabulate when selecting a new cleaning system. A detailed spreadsheet is available for downloading (from the website ‘http://www.microcareprecisioncleaners.com/assets/documents/uploads/Degreaser_Costs_Compared.xls’) that could serve as a template for engineers planning this comparison. But, in general, use the following cleaning scoreboard to find the winning technology for your company:

1. Determine the likely cleaning requirements for today’s products as well as those of tomorrow. Average those requirements into an hourly rate of required throughput.

2. Compare different cleaning technologies. Send samples to the equipment makers to prove the ability of their systems to clean the components to your specifications.

3. From among the remaining candidate systems, collect comparative data on every important characteristic. Be sure to include up-front capital costs, plus the direct and indirect operational costs (supervisory and engineering labour costs, plus energy, water, solvent, labour and maintenance costs).

4. As the various costs are collected, divide them by the expected throughput of the system to calibrate them into a cost-per-part-cleaned index.

5. Sum all the data into a single performance index, the total cost-per-part-cleaned.

6. Select the system with the lowest total cost-per-part-cleaned.

Using standard statistical tools, engineers can model all the operating costs for systems of different types and sizes. If this process is completed accurately, thoroughly and impartially, the savvy engineer can be confident that the selected system will become a valued part of the production process for years to come.


The author is a vice president at MicroCare Corp.—a critical cleaning solutions provider. MicroCare’s products include water-based cleaners, a wide array of solvent, hydrocarbon and terpene cleaners, and innovative benchtop tools that help reduce cleaning costs

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