The big and medium manufacturers understand the harmful effects of HCFC and have taken precautions well in advance to meet the challenges of phasing it out. Small manufacturers, however, may face difficulties in changing over to new cleaning processes
By Richa Chakravarty
Monday, May 12, 2014: The US has made it mandatory that products imported or manufactured after January 1, 2015, which contain or have been manufactured by processes using hydrochlorofluorocarbon (HCFC), must bear a warning label in order to enter the US market. India has also started phasing out HCFC.
HCFC is a common precision solvent used for high-end cleaning. It is harmful to the environment as it depletes the ozone layer. While it is a huge cause for environmental concern, phasing it out will affect the cleaning process in electronics manufacturing. Electronics exports to the US will also get affected if the manufacturers do not abide by the country’s Clean Air Act.
Why electronic assemblies need to be cleaned
During the production of an electronic assembly, various flux formulations are used in different types of manufacturing equipment. After the soldering process (by vapour phase, wave, selective wave or manual soldering), the flux residues must be removed to ensure the long-term reliability of the electronic assembly.
In the consumer industry, the removal of these flux residues is not always required. However, for the manufacturing of class III assemblies, cleaning becomes a mandatory step to guarantee the highest reliability.
Over the years, there have been advancements in cleaning technologies like ultrasonic cleaning, high pressure cleaning, aqua storm, plasma and water-based surfactant technology.
With growing environmental concerns, many electronics manufacturers are moving away from traditional solvent cleaners that use ozone depleting chemicals or have a high VOC (volatile organic compound) content, and are replacing them with safer alternatives. Although many solvent cleaners enable a convenient single-stage process, water-based cleaners have several advantages including their non-flammable properties, low odour, little or no VOC content and very low toxicity. Whether it is ultrasonic, spray under immersion or dishwasher type application, it is important to identify the correct water-based cleaner for the specific job.
Water-based flux removers work by saponification, neutralising the flux acids. There is also a newer type of surfactant-free water-based cleaner. Based on glycols, these cleaners combine the advantages of water-based and solvent-based cleaners and need minimal rinsing.
The need to phase out the use of CFCs/HCFCs and advances in technology have resulted in different methods and solvents being used in the cleaning process during electronics manufacturing. PCBs are cleaned using ultrasonic cleaning methods. This is another type of cleaning that helps to remove residues in PCB assemblies. The normal cleaning agent used for this is isoproponal alcohol (IPA). Ultrasonic cleaning machines are available in different frequency ranges.
“Phasing out of HCFC started in India way back in 2009 and since then, manufacturers have been concentrating on cleaning methods that do not use HCFC. We have been using water-based surfactant technology for heavy contaminants, which can be removed by detergents and water. We use electronic grade IPA, which is an ultra high pure cleaning solvent with reduced contamination and defect densities,” shares Sanjiv Narayan, director, SGS Tekniks Manufacturing Pvt Ltd.
IPA is used extensively throughout the semiconductor industry for rinsing wafers, drying wafers and cleaning equipment. But impurities in IPA may be left on the wafer surface, risking degradation of device performance and process equipment, as well as yields.
With miniaturisation, the assembly processes have been modified due to the use of smaller components and more compact board assemblies. As a result, surface mount technology (SMT) is used, through which electronic components get soldered without leaving any trace of flux. In this case, there is no requirement for ultrasonic or any other cleaning after soldering.
Smile Electronics uses automatic SMT and PTH assembly lines, where dip cleaning and ultrasonic cleaning processes are used. “An ultrasonic cleaning machine at a fixed frequency of 34 kHz is used to clean PCBs in our unit. These cleaning processes use IPA, bio-act and Kaizen materials that do not have any HCFC content. The tank should be free of foreign object damage (FOD), ESD precautions should be taken and the correct chemicals should be used. Mechanical stress should be avoided on PCBAs during the cleaning process,” says Aashita Gupta, executive, business development and commercials, Smile Electronics Ltd.
New cleaning solvents
With the phasing out of CFCs and HCFCs, standard solder pastes and fluxes have evolved from rosin activated (RA) and mildly activated rosin (RMA) fluxes. “Today most flux formulations have changed and the earlier chemicals like CFCs, HCFCs, brominated solvents, detergents and glycols cannot do a good cleaning job any more. The new environment-friendly solvents do a better job,” informs Sanjiv Narayan.
Formulated hydrocarbons C have been developed mainly after the ban on CFCs and HCFCs, and when perfectly formulated, can easily outperform any other cleaner. They can remove flux residues, solid residues and salts under any type of component because of their very low surface tension. They are some of the most user- and environmental-friendly cleaners.
Lead-free trend impacts cleanliness
Partially removed or untouched residues can lead to component and product failures, resulting from electrochemical migration or current leakage. For mission critical electronics or Class III products, such as those used within the military and in the aerospace and medical industries, the highest electronic reliability is required. Hence, lead-free soldering machines are used where there is no cleaning process.
No effect on big manufacturers
Most of the manufacturers in India are aware of the hazards of CFC/HCFC and have stopped using this method of cleaning in their electronics manufacturing units. “The cleaning method is completely dependent on the criticality of application. Most of the machines available today require no cleaning at all, unless the client asks for cosmetic cleaning. In the organised sector, a no-clean process or water soluble flux is used. Almost every manufacturer in the organised sector adheres to the cleaning norms, as most of the businesses are dependent on exports,” informs Sanjiv Narayan.
It seems that while the big and medium manufacturers understand the harmful effects of HCFC and have taken precautions well in advance to meet the challenges of phasing out, small manufacturers may face difficulties in changing over to new cleaning processes. But keeping in mind the flourishing electronics grey market, buyers ought to be more cautious so as not to buy products with HCFC. Consumers should look for warning labels on the products.
|The cleaning process should meet the following criteria|
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