From Global SMT
Over the past 28 years, the electronics assembly cleaning industry has gone through three distinct periods. There was the period before 1989 when virtually all assemblies were cleaned after soldering. Then there was the period between 1989 and 2005 when cleaning was nearly exclusive realm of military, aerospace and medical (high-reliability assemblers). Now is the current period – 2005 to present – where, according to industry poles, two thirds of all assemblies and 52 percent of all no-clean solder paste application result in cleaning.
Anthropologists believe that the great plagues of the middle ages can be attributed, in part, to the decline in cleanliness standards including personal hygiene in that era. It seems that throughout history, the lack of cleanliness results in undesirable outcomes. Ironic, to say the least, is the fact that in our modern society cleanliness is valued greatly. There is, however, one area in which we pay little attention to cleanliness. This area affects almost every aspect of our lives. This area affects how we communicate, travel, protect ourselves, play, work, eat, and even how we access medical care. This area is electronics. It is nearly impossible to think of life without electronics. We depend on electronics assemblies in nearly every aspect of our lives. Why then do we not demand a higher level of cleanliness with electronics assemblies?
Unfortunately, the answer to that question is common. When industry-favorite solvents were banned due to environmental concerns in 1989, the industry, rather than switching to environmentally responsible alternative solvents chose instead of adopt a no-clean approach. New low-residue flux formulations were introduced, leaving only small amounts of flux residue on the assemblies. the volume of resides left on the assemblies was, at that time, considered to be acceptable. the industry weighed the cost of switching to alternative solvents and compatible equipment against accepting small amounts of residues on assemblies. Cost savings won. But not everyone abandoned cleaning. Military, medical, aerospace and other high-reliability maintained a cleaning program. Most of these industries switched to alternative cleaning technologies, most often aqueous-based cleaning methods. It seems that cleaning is required only when reliability is paramount.
This dual alternate universe, 100 percent leaning of every assembly with high-reliability assemblers vs. 100 percent not-cleaning of commercial assemblers, lived mostly happily side by side for many years. over time, however, many commercial assemblers have adopted a cleaning process. As referenced earlier, two thirds of all assemblers state that they clean between 25-100 percent of their assemblies. Of the multitude of commercial assemblers using no-clean solder pastes, 52 percent of them are cleaning after reflow. What is the driver for the rapid rise in the amount of assemblers adopting or readopting a cleaning process?
There are many factors that drive our industry back to cleaning. In fact, the primary driver is identical to the one that, 24 years ago, steered assemblers away from cleaning in the first place - economics.
One frequently overlooked factors is that when assemblers stopped removing flux from their assemblies due to the implementation of low-residue fluxes, all cleaning stopped. Contamination from the bare board fabrication, component fabrication and assembly processes were allowed to remain on the assembly along flux residues. The fact is that modern miniaturized, lead-free assemblies cannot tolerate as much contamination as assemblies of the past. Smaller assemblies, higher densities, lower component standoff heights, faster speeds, and higher reflow temperatures all combined to create the perfect storm of events that are causing electrical migration and electrical leakage failures on assemblies throughout the world. In field assembly, failure is costly in terms of both economic and reputation concerns. A measurable percentage of the electronics industry has determined that it is more cost effective to remove contamination than to reap the cost of contamination related failures.
There are many perceived challenges when one considers the adaptation of a cleaning process: What is the cost of cleaning (cost per assembly)? What is the cost to the environment (kudos to those who consider the environment)?
So, what is the cost of cleaning? Many assemblers have discovered that it is surprisingly low. There are many cleaning methods, machines and processes available from which to choose. the correct specific method is determined by several variables including desired throughput, types of contamination being removed, environmental restrictions, etc. While there is no "one size fits all" solution, there are a handful of solutions that fit almost all assemblers. We spend a lot of time talking about a "properly optimized process" (the correct machine to match the required throughput, equipment readiness, cleanliness requirement and discharge configuration). When one has a properly optimized process, one may except total cleaning costs per assembly to be under USD $0.06 per assembly for low discharge cleaning applications (environmentally beneficial) to USD $0.16 per assembly for zero-discharge (environmentally responsible).
Many assemblers have resisted cleaning processes for strictly environmental reasons. Many have been concerned that by solving one issue (assembly failures), they would exchange that issue for another (environmental regulatory issues). The fact is that recent advances in cleaning technology have allowed assemblers to clean assemblies, regardless of flux type, and operate in a completely zero-discharge configuration. By operating a cleaning process that reuses the cleaning chemical, lowering operational costs, without a connection to a drain, and bypassing environmental regulations, one can experience an optimized cleaning process that eliminates contamination-caused assembly failures while obtaining an acceptable cost per cleaned assembly, and a total avoidance of environmentally-based regulation. This is a win-win scenario.
Manncorp offers a range of batch-format PCB cleaning and defluxing equipment that are capable, cost-effective and environmentally friendly. All defluxers feature built-in cleanliness level testing and the ability to clean PCB assemblies to a user-set level of cleanliness. They also come standard with SPC data logging for traceability and process improvement.
