So, You Need to Clean? A Defluxing Process Roadmap, Part II

Estimated reading time: 4 minutes

By Michael Konrad, Aqueous Technologies

Our roadmap consists of several key factors: type of flux, type of assembly, product flow, volume, staff competency, facility restrictions, environmental restrictions, and budget. In Part II, I discuss volume, staff competency, facility restrictions, environmental restrictions, and budget.

Read Part I of the Defluxing Process Roadmap.

We have witnessed the perfect storm of events that have combined to compel OEMs and contract assemblers to reinstate a long-abandoned practice of removing flux residues from circuit assemblies.

I have written at length about the forces that have combined to mandate a defluxing process. These modern trends include the adoption of lead-free alloys, board and component miniaturization, increased reliability expectations, increased reliance on quality standards, and even the increased level of product liability. Be it by requirement (military/IPC cleanliness specifications) or by necessity, defluxing is once again part of the mainstream assembly processes.

You need to implement a cleaning/defluxing strategy. Unlike in times past, there are a number of factors one must consider when choosing a defluxing process, hence the need for a practical roadmap. Our roadmap consists of several key factors. This article focuses on volume, staff competency, facility restrictions, environmental restrictions, and budget. The additional roadmap points type of flux, type of assembly, and product flow are addressed in Part I of the Defluxing Process Roadmap, in the July/August issue of SMT.

For the purpose of relevancy, I shall eliminate manual cleaning from this discussion as it represents a very small segment of the total defluxing processes and is more common in touch-up and repair.

VolumeIn years past, volume determined with technology one would purchase, batch or inline. Batch machines were designed for low-volume, high mix while inline defluxing systems were designed for high volumes. Today, this has changed. Batch format defluxing system, while still suitable for low volume, high mix applications have been engineered to produce throughput rates as great or greater than inline systems. This technological advance has pushed out the volume threshold used to justify one technology over the other. There are three choice configurations to choose from; batch, high-yield batch, and conveyorized (inline) defluxing systems. As energy consumption, water consumption, chemical consumption, and environmental noise are added to the usual list of technical considerations, and because most defluxing process are utilized in a batch format, more companies are choosing batch-format defluxing equipment.

As a general rule, a conveyorized defluxing system's throughput capabilities are based on conveyor speed and board length. On most batch-format defluxing systems, throughput rates are based on programmed cleanliness settings and board size.

Staff CompetencyThis is an oft-overlooked criteria. Modern defluxing equipment, like other assembly equipment, has become highly automated. Some equipment allow operators to only choose from a library of recipes (designed by the manufacturing or process engineer), reducing the chance of operator error. Modern defluxing systems are equipped with password protection, preventing an operator from modifying critical settings such as final cleanliness and desired chemical percentages. SPC functions record every cycle, including set and actual cleanliness, a valuable asset in today's TQM / ISO / Six Sigma world.

Different brands and configurations offer varying degrees of process control and user control. Regardless of the level of control and automation, one must ask, Who controls the process?

Facility RestrictionsEvery automated defluxing system requires the following items: electrical power, water (DI), drain or recycling equipment, and exhaust. The amount of these resources vary widely based in the defluxing system's configuration (batch or conveyorized).

Electrical power. Electrical utility requirements vary from 15 KW (high-performance batch) to 170 KW (high-performance conveyorized).

Water requirement. Water requirements vary from 30 gallons per hour (high-performance batch) to 300 gallons per hour (high performance in-line).

Drain or recycle equipment. Keep in mind, all water that goes in must go out. This means that the water input requirement must be matched with a like drain requirement or an equivalent recycle (closed-loop) capacity. Zero-discharge evaporators are a popular choice on batch configurations due to their low discharge rates.

Environmental RestrictionsEnvironmental liability is a modern concern. Many municipalities monitor the volume of industrial effluent being directed to drains. Every gallon sent to drain counts, even if it is relatively "clean."

In years past, many defluxing systems, particularly conveyorized models, operated on just water, no chemicals. Water-only defluxing systems were easily and efficiently closed-looped with traditional carbon and ion-exchange resin technology. Today, with chemical additives representing the conventional wisdom, close-looping the process is costly due to the fact that the defluxing chemicals must be completely segregated from the carbon and resin media, lest it destroy the expensive resins. This normally means that a separate isolation section must be added to conveyorized cleaners to provide better separation between the wash chemical and the rinse sections. This results in a longer machine and frequently a non-closed-loop section.

If a zero-discharge configuration is desired, a batch configuration is preferred as there is normally internal segregation of the wash and rinse sections which prevent excess cross contamination without the need for isolation drains. Because the total effluent volume is low, waste water evaporators can be connected in lieu of a drain.

BudgetAs equipment prices vary from the tens of thousands to the hundreds of thousands, the important calculation is the cost per clean board. If specified correctly, any defluxing process (batch or conveyorized) should yield a per board cost of mere pennies. Needless to say, the cost of contamination always exceeds the cost of cleaning.

Michael Konrad is an SMT Advisory Board member and president of Aqueous Technologies. Konrad also is an IPC SMEMA Council APEX Committee Member. He was a "High Performance Electronics Assembly Cleaning Symposium" panelist. Contact him at konrad@aqueoustech.com. Read Part I of the Defluxing Roadmap, So, You Need to Clean? A Defluxing Process Roadmap.