Traditions of the Season and Process Change

To The Cleaning Lady, nostalgia includes hand-grating potatoes for Chanukkah latkes; and bandaging the inevitable minor knuckle scrapes. Nostalgia includes one lonely Menorah with orange candles set high on a mantlepiece (the elders were afraid that the Cleaning Lady would set fire to the house). Nostalgia for The Rocket Scientist includes parents attempting to conceal a decorated Christmas tree from the Rabbi by dragging it up to the third floor, leaving a tell-tail residue of tinsel and pine needles on each stair tread. It includes latkes from the deli arranged on a Limoges platter. 

Just as you as an individual have fond memories of the look, sounds tastes and aromas of the holidays, as a manufacturer of components and products, you also have cherished traditions and nostalgic recollections of critical product cleaning in the “good old days.” Critical product cleaning was not always perfect or trouble-free, not even during the era of Freon and trichloroethane. Consider that your manufacturing facility may benefit by honoring the good old days, and then moving forward.

We assert that you are likely to invest in new cleaning processes in the next two to five years. The process of process change costs money (1); cutting corners costs even more money (2). Some manufacturers will have to change the cleaning process because the U.S. EPA is proposing to restrict or even ban effective solvents, notably trichloroethylene, methylene chloride, perchloroethylene, and n-propyl bromide (3). Trans-DCE, blended with fluorinated chemicals to inert the flashpoint, can be used. However, there are physical and chemical properties that inherently limit the way the blends are used. Both trans-DCE and fluorinated chemicals may also become regulated in the near future (4).

Most electronics assemblers remember when they could use no-clean flux without having to clean it. More mature electronics assemblers recall the joys of removing RMA (Rosin Mildly Activated) flux with CFC-113 (on commercial product was Freon-113). Residue removal was referred to as “defluxing,” not cleaning. The main issue was to minimize conductive residue on the finished product. The spacing of components on the base board would be considered generous by today’s standards. In fact, assemblies having components with a stand-off less than mil (0.005 inch) were considered to be a cleaning challenge. Largely in response to environmental pressures, notably the destruction of the ozone layer, many assemblers moved to no-clean fluxes or to organic acid (OA) fluxes. OA fluxes must be rinsed with water to avoid unacceptable conductive residue. While RMA flux is still used for specialized applications, beginning in the 1980s and 1990s, more and more product was built using so-called “no-clean” flux, a term Barbara has always loathed. No-clean implies “no-residue.” This is misleading. There was always some residue, but it was acceptable for most applications. 

Changing the soil, the solder flux, transformed the landscape of cleaning requirements. Problem solved – for a time. For most assemblers, the concept of using no-clean flux with either no post-reflow cleaning or at most simple rinsing is a distant memory. In short order, manufacturers of high-reliability product discovered that assemblies soldered with no-clean flux had a much lower failure rate if the assemblies were sprayed with water, often by placing them on conveyor belts in in-line cleaning machines. At first, anointing electronics assemblies with deionized water was considered the icing on the cake – a final insurance policy. 

Boards became more miniaturized, more densely populated. Designers of electronics assemblies have long been accused of trying to put 20 pounds of “stuff” into a 10-pound bag. And that was in the good old days. Designers squash more and more components into smaller and smaller spaces (5). Why? Because the world demands it! For example, in the 1950s automotive electronics consisted of the horn, lights, radio and windshield wipers. Now, electronics is virtually everywhere in the vehicle. The proportion of the cost of electronics to the cost of the total vehicle has grown from about 1% to over 35% (6). As we’ve been teaching over the past, uhm, three decades, less space between the components means that effective cleaning requires more attention to TACT (Temperature, Action, Chemistry, and Time). Over the years we’ve also made valiant attempts to convince designers to consider cleanability as a factor in design. We’ve written papers, done presentations, and attempted to communicate face to face with designers. Efforts have at best met with critical success. 

Today, most electronics assemblers consist of attempts to meet customer requirements by ever-increasing efforts to clean in large, plastic, in-line cleaning machines. This involves in-air spray washing with an aqueous cleaning agent, rinsing with copious amounts of water, and drying. Line-of-sight cleaning of complex assemblies has inherent limitations. The concept of immersion cleaning with ultrasonics seems groundbreaking; it may be essential to achieve adequate soil removal. While alternative promises show the promise of more effective cleaning of complex product, the tendency is to stick with the tried and true – in this case, enormous machines spraying more and more cleaning agent on the parts. 

Change is inevitable, whether the requirements for change are impelled by governmental regulation or by increasingly exacting product requirements. Whatever the motivation, think of changing of the cleaning process to be an investment, not an expense. It is crucial to anticipate and embrace change, not to fear it. Nostalgia and tradition are important. Maybe, at least for some manufacturers, traditional methods must be abandoned. In electronics assembly and in other areas, progress means understanding the possibilities, testing, and actually adopting alternative cleaning methods. In the coming months, we will expand on newer cleaning possibilities.

References 

1. 1. B. Kanegsberg and E. Kanegsberg, Clean Source Newsletter, September 2023; https://bfksolutions.com/real-costs-of-changing-the-cleaning-process/ 
   2. B. Kanegsberg and E. Kanegsberg, Clean Source Newsletter, October 2023; https://bfksolutions.com/real-costs-of-changing-the-cleaning-process-2/ 
   3. B. Kanegsberg and E. Kanegsberg, Clean Source Newsletter, July 2022; https://bfksolutions.com/degreasing-and-fireworks/ 
   4. B. Kanegsberg and E. Kanegsberg, Clean Source Newsletter, January 2023; https://bfksolutions.com/interesting-times-for-manufacturers/
   5. B. Kanegsberg, “Meshing Design with Assembly,” Altium Design Blog, May 2019 https://resources.altium.com/pcb-design-blog/meshing-design-with-assembly-flux-cleaning
   6. M. Valenti, “Cleaning Sensitive Electronics for Remanufacturing”, Presentation for MERA, The Association for Sustainable Manufacturing, 2019; https://www.youtube.com/watch?app=desktop&v=6TFxNHfVaSg 

Other Resources
“The evolution of mobile phones: 1973 – 2019”
https://flauntdigital.com/blog/evolution-mobile-phones/

“The Evolution of Cell Phone Design Between 1983 – 2009),” WDD Staff, Web Design Depot
https://www.webdesignerdepot.com/2009/05/the-evolution-of-cell-phone-design-between-1983-2009/

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