Home Products & Industries Surface Treatment Case Studies Replacing IPA with AXAREL™ 2200

Replacing IPA with AXAREL™ 2200

Isopropyl Alcohol Alternative for Electronics Cleaning

Isopropyl alcohol (IPA) continues to be a popular cleaner for the removal of solder paste from stencils and misprinted circuit boards because of its compatibility with assembly materials, reasonable performance and low cost.  Its familiar odor and fast evapor­ation make it agreeable to operators. However, as paste technology has advanced and environmental regulations tightened, the demand for cleaning agents with better solvency and less environmental impact has continued to increase.  AXAREL™  2200 Cleaner was developed to meet this demand.
AXAREL 2200 was formulated by carefully selecting solvents that would allow it to quickly dissolve a wide variety of no-clean, water-soluble and rosin paste residues, as well as un­cured surface mount adhesives from sten­­cils, mis­printed circuit boards and circuit assemblies. It has also been shown to effectively remove many flux residues after reflow. The unique combination of solvents in AXAREL 2200 make it a more powerful and a more ver­satile cleaner than IPA.
Non-volatile residue (NVR), i.e. residue which remains after the solvent has completely evaporated, is a concern associated with any solvent cleaner because these residues can potentially cause performance issues. Since Vantage has strict quality standards, AXAREL 2200 will be con­sistent in purity and composition on a lot to lot basis. IPA, being a com­modity chem­ical, has a tendency to vary significantly in composition which in turn adds significant variability to the type and amount of residues that remain after cleaning.
Emissions of volatile organic compounds (VOC) are now being regulated in most parts of the world. Fast evaporating solvents, such as IPA, are among the major sources of VOC emissions. Many electronics manufacturers are now investigating alternative cleaning methods to lower or eliminate IPA emissions from their operations. IPA has been found to evaporate approximately 7.3 times faster than AXAREL 2200 under simulated stencil cleaning conditions (see the data in the Economics section).  In addition, IPA has a vapor pressure that is 12.6 times that of AXAREL 2200. Table 1 shows the relative rates of VOC emissions by IPA and AXAREL 2200 based on vapor pressure comparisons and the relative evaporations rate. As can be seen, simply converting from IPA to AXAREL 2200 will reduce the rate of VOC emissions by 86-92%.

Table 1:  Relative Rate of VOC Emissions

Even though IPA has been used in electronics production for decades, manufacturers are becoming more concerned about the flammability of IPA cleaning pro­cesses.  These cleaning processes typically operate at room temperature (approxi­mately 77 °F / 25 °C), which is well above the flash point of IPA (53 °F /12 °C). This means that the vapors from this process can be ignited if both an ignition source (such as a soldering iron) and oxygen (which is always present in the form of air) are present.
The flash point of AXAREL 2200 exceeds room temperature (111 °F / 44 °C), so the risks associated with its use at room temperature are considerably lower than those of IPA. In fact, AXAREL 2200 can be used safely in the proximity of ignition sources, so long as AXAREL 2200 is kept at room temperature (below its flash point). Furthermore, test results have demonstrated that AXAREL 2200 provides better cleaning than IPA at ambient temperatures.
Using the lower explosive limit (LEL) values for the various components of AXAREL 2200, all of which are similar, the LEL of AXAREL 2200 at room temperature and atmospheric pressure is approximately 13,000 parts per million (1.3%).  The vapor pressure of AXAREL 2200 is approximately 3.5 torr (3.5 mm Hg) at room temperature which corresponds to approximately 4,600 ppm.  Thus, under normal operating conditions, there is approximately three times less AXAREL 2200 vapor present in the air than is required for ignition. As a result, AXAREL 2200 vapors cannot be ignited when the liquid is at room temperature.
The ingredients in AXAREL 2200 were carefully selected to offer low toxicity without sacrificing performance, convenience or affordability. Under normal conditions, the vapors from AXAREL 2200 are not irritating to the eyes, skin or respiratory tract.  In studies with rats, inhalation of saturated vapors (2500 ppm) of the non-linear alcohol in AXAREL 2200 produced no adverse effects.  Likewise, there have been no reports of adverse inhalation effects in humans.  Similar results are expected for the other ingredients present in AXAREL 2200.
The inhalation hazards associated with the use of solvent cleaners have become increasingly important to the prospective users.  The American Conference of Governmental Industrial Hygienists (ACGIH) provides recommendations on exposure limits for a number of chemicals and solvents. Common recommendations include Short-term Exposure Limits (STEL), Threshold Limit Values (TLV) and Permissible Exposure Limits (PEL). In general the higher the TLV and/or PEL the better; however, neither the TLV nor the PEL values provide enough information to accurately judge the differences in the potential inhalation exposure hazards when comparing two solvents because they do not consider how likely each solvent will be volatilized.
Kob & Altnau1 proposed the use of the Vapor Hazard Ratio (VHR) as a more realistic way to compare the relative inhalation hazards of various solvents used for cold cleaning.  The VHR takes into consideration both the exposure limits and the vapor pressure of each solvent since the later will determine the likelihood of exposure to the solvent. The VHR for IPA and AXAREL 2200 are 289 and 18, respectively (see Table 2). This implies IPA is a substantially greater inhalation hazard than AXAREL 2200.
1 N. Kob and G. Altnau, “Vapor Hazard Ratio—Assessment for Solvent Risk Comparisons”, CleanTech Magazine, May 2001, pp 30-37.
                                                            Vapor Pressure (mm Hg) x 106
Vapor Hazard Ratio (VHR)  =        --------------------------------------------------------
                                                            Exposure Limit (ppm) x 760 mm Hg
Note:  Vapor pressure is normalized to atmospheric pressure (760 mm Hg), and the factor 106 is used to bring the VHR into whole numbers. Higher numbers indicate higher risk.
Table 2:  Relative Inhalation Risks

AXAREL 2200 has a mild petroleum-like odor and it has not been a serious concern to cur­rent customers. 
To determine the economic impact of using AXAREL 2200 instead of IPA, a "use-cost analysis" can be performed. Relative use-cost information can be determined by evaluating the differences in evaporation rates, maximum solder paste loading, drag-out, process cycle time and the purchase price of the solvent. The data shown in the Table 3 below are from laboratory studies simulating open-tank, stencil cleaning processes.  These data show that an IPA bath evaporates approximately 7.3 times faster than an AXAREL 2200 bath under the same conditions.
Table 3:  Evaporation Rates

Drag-out can also be a significant source of solvent loss.  In some high volume applications, drag-out accounts for as much as 50% of the total IPA loss.  Experi­ence has shown that drag-out per substrate is typically less for AXAREL 2200 than IPA.  Combined with the lower AXAREL 2200 evaporation rate, the consumption of IPA is typically between 5 and 8 times higher than AXAREL 2200.  So, despite its higher per-gallon price, AXAREL 2200 use-cost is competitive with IPA when one multiplies the price per gallon of IPA by a factor of 5 to 8, which accounts for the much higher consumption of IPA versus AXAREL 2200.

Total cycle time is approximately the same for AXAREL 2200 and IPA.  Since AXAREL 2200 has higher solvency than IPA, the wash time is reduced. This com­pen­sates for the slightly longer drying time of AXAREL 2200. Simple air movement around the substrates accelerates the drying time, making the drying time for AXAREL 2200 faster than expected based on the evaporation rate data.
AXAREL 2200 is compatible with all metals as well as most epoxies, flex laminates and other crosslinked polymers. The product is compatible with screen emulsions, stencils, ceramics and epoxy substrates as well as most electronic components. Emulsions used to bind stencils to frames may be attacked after prolonged exposure to the solvent or temperatures above 120 ˚F (49 ˚C). Table 4 summarizes the results of compatibility testing on common plastics and elastomers. The user is recommended to carry out compatibility testing to confirm suitability for use.
Table 4:  Plastic/Elastomer Compatibility of AXAREL 2200

In summary, compared to IPA, AXAREL 2200 is a more powerful cleaner, offers more process flexibility, substantially reduces the rate of VOC generated, is safer for employees, and costs less to use.
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