Archived Newsletters
Electronics in 2010+: Cleaning Challenges
Ed Kanegsberg and Barbara Kanegsberg
“It’s simple; we don’t have any cleaning problems. We just use water.”
For the better part of a generation, post-solder defluxing has been relatively simple.
History lesson
It wasn’t always the case. Rosin fluxes, traditionally used in military and other high-reliability applications, had to be cleaned with CFC-113 or trichloroethane. Ultrasonic cleaning was largely not acceptable.
Eliminating ozone depleting chemicals (ODC’s) required replacing chlorofluorocarbons (CFC’s). The replacement efforts, beginning in the late 1980’s, were arduous and challenging. Barbara was involved in those efforts; implementing replacements for ODC’s in electronics was part of the basis for her EPA Stratospheric Ozone Protection Award. In retrospect, it was an incredible experience that benefited industry and the environment. Options increased. Aqueous, semi-aqueous, and advanced solvent processes grew in popularity. RMA flux was supplanted by water-soluble OA flux or low-residue (no-clean) flux, even for many high-reliability applications. Manufacturers who had been in the electronic assembly field for many years saw cleaning problems go away. Ok, maybe the no-clean flux requires a bit of cleaning. However, water or dilute aqueous cleaners did the job.
New times mean new challenges
• Design requirements
• Performance requirements
• Economic requirements
• U.S. and international environmental regulations
Design requirements
Design for manufacturability is a wonderful goal; such design generally involves simplicity. If the components of a circuit board assembly could be compared to a city, it is desirable to have open spaces and to avoid an overly dense population. Because of performance requirements, design for manufacturability may be a relative term. The architecture becomes complex, with tightly spaced components and low standoff. In critical cleaning applications, the physical properties of the assembly at the micro level meet the impasse of the physical properties of water, water with additives, and even some solvents. Important physical properties of the cleaning agent include the surface tension, density, and viscosity. For components with low standoff, roughly speaking below 5 mil, aqueous cleaning is a challenge. The challenge can often be met by prolonged force; this translates into slower speeds and longer in-line systems.
For more of what you need for successful electronics assembly including
Product & cleaning processes requirements
Lead-Free
Future regulation and restrictions
Pathway to possibilities
IPC and Cleaning
Product & cleaning process performance requirements
High reliability electronics in aerospace, military, medical, and other critical requirements require long-term performance. In fact, for products associated with medical devices, expectations of long-term reliability are increasing. The performance of the cleaning process is important for both short term and long term reliability. This means careful selection, validation, and monitoring of all new processes.
Conventional wisdom is that consumer electronics do not necessarily require careful cleaning. The product may not have a long expected lifetime; inexpensive may trump quality. Given global competition and movements toward sustainability, the paradigm may again shift.
Component miniaturization will continue to create challenges. As we have indicated, miniature components, close spacing and small boards are more difficult to clean, especially with conventional aqueous processes. Water just doesn’t penetrate into small spaces effectively due to its high surface tension. Adding wetting agents, such as surfactants, can help get the chemistry into the spaces, but the challenge is how to get it out, i.e. how to rinse.
Cleaning and contamination removal challenges are not limited to flux removal. Circuit board and component materials can have compatibility issues with cleaning chemicals. The entire fabrication process must be considered in terms of residual contamination, surface properties, and product integrity.
Lead-Free
The move to lead-free solders was spurred by the European Union (EU) directive Restriction of the use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS). The RoHS directive affects electronic components sold in the EU, but lead-free is also being mandated in other areas of the world, including California in the US.
The impact of lead-free on electronic cleaning is primarily associated with the higher temperatures required with lead-free solders. High temperatures can bake residues on a surface; baked-on residues are more adherent and more difficult to clean.
If some of the product line can be produced with more traditional solders and fluxes, there is still the issue of multiple assembly and cleaning processes.
Future regulation and restrictions
The impact of Greenhouse Gas emissions is very likely to affect all manufacturing, especially cleaning processes. California recently passed advanced legislation in the area. Activities in California cannot be dismissed elsewhere. In fact, California now has a liaison with offices in Washington, D.C. Based on initial indications, the goal is to make California regulations the norm throughout the U.S. In addition, the DOD is issuing policy on climate change.
Energy use may be restricted by regulation or through economic pressure. Many critical cleaning processes need large amounts of energy, notably when large quantities of heated water are used and for drying operations.
Water is a valuable, increasingly scarce resource. Water use may be subject to restrictions through direct regulation or economic pressure, especially in drier climate regions such as the American Southwest. Solvent processes that declined in use after the CFC phase-out may experience a resurgence when energy and water costs increase. Well designed solvent equipment can now better contain emissive vapors, decreasing the risk to workers and the environment.
At the same time, other restrictions on cleaning agents are increasing; and these restrictions may impact solvent cleaning plans. Most cleaning and defluxing agents contain at least some VOC’s. There is pressure to reduce VOC’s (smog producers), and not just in California. At the DoD level, the Joint Services Solvent Substitution Working Group (mercifully referred to as JS3WG or JS3) is tasked with eliminating HAP’s and minimizing or eliminated VOC’s across the board (Army Air Force, Navy, Coast Guard, NASA).
Pathway to possibilities
As with the replacement of ODC’s – which we sometimes refer to as “The Great Freon Phaseout – these restrictions can be recast and in fact exploited to achieve more effective, reliable electronics defluxing and critical cleaning. In the course of studies performed for University of Massachusetts, Lowell, we unearthed studies indicating the performance and economic advantages of insulation. Initial investments in well-insulated equipment, adoption of less emissive cleaning equipment, recycling, and closed-loop processes are likely to yield benefits not only in lower costs but also in superior process performance.
IPC and Cleaning
The IPC Cleaning Handbook is under revision to achieve a consolidated and updated Handbook. Barbara Kanegsberg is a member of the IPC “Cleaning and Alternatives Task Group.” IPC 5-30, Cleaning and Alternatives, is chartered with providing guidance on cleaning materials and cleaning processes. We will give you an occasional “heads up” about our activities regarding cleaning and surface quality for electronics assembly. For additional information, please see:
http://www.ipc.org/CommitteeDetail.aspx?Committee=5-30
How We Help You
For 15 years, BFK Solutions LLC has helped manufacturers like you achieve superior product through efficient, effective, high-quality cleaning and assembly processes. Depending on your needs, specifics involve evaluating new cleaning agents and equipment, troubleshooting, educational/training programs and process validation. Our clients benefit from our experience in diverse areas including medical devices, electronics, military/aerospace, precision optics, and metal fabrication and finishing. As independent consultants, we work with both manufacturers and suppliers; we do not accept commissions or referral fees.
We welcome your comments on issues impacting electronics cleaning in the decade to come. Contact us at
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