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ELECTRONIC COMPONENT COOLING ALTERNATIVES: COMPRESSED AIR AND LIQUID NITROGEN
Schmitt, S. C. AND R. F. Olfenbuttel. ELECTRONIC COMPONENT COOLING ALTERNATIVES: COMPRESSED AIR AND LIQUID NITROGEN. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-94/170 (NTIS 95-100087), 1994.
The goal of this study was to evaluate topics used to troubleshoot circuit boards with known or suspected thermally intermittent components. Failure modes for thermally intermittent components are typically mechanical defects, such as cracks in solder paths or joints, or broken bonds, such as interconnections inside integrated circuit packages or capacitors. Spray cans of refrigerants (R-12 [CFC-12] and R-22 [HCFC-22]}, which are commonly used in electronics manufacturing and repair businesses for this purpose, served as the benchmark for the evaluation. A promising alternative technology that was evaluated in this study is a compressed-air tool that provides a continuous stream of cold air that can be directed toward specific components. Another alternative technology that was considered is a Dewar flask that dispenses cold nitrogen gas as the cooling agent. Critical parameters were measured for each cooling method to provide a basis for comparison of compressed air and liquid nitrogen with spray cans of refrigerant. These parameters are accuracy, electrostatic discharge risk, cooling capability, technician safety, pollution prevention potential, and economic viability. This study was performed in accordance with the Quality Assurance Project Plan for Cold Compressed Air for Electronic Component Cooling Study, dated August 1991. Although the plan was written specifically for the evaluation of compressed air, the test plan was written to include an evaluation of liquid nitrogen because test site staff were interested in evaluating this technology. The liquid nitrogen evaluation showed that it could be a viable alternative. Therefore, with the concurrence of the Project Officer, this final report includes the results of both compressed air and liquid nitrogen. Newark Air Force Base, in Ohio, was the site for evaluating compressed-air technology. Electronic circuit boards from a variety of Air Force Systems are tested and repaired on a daily basis. A percentage of these circuit boards demonstrate thermally intermittent failure modes and were used for comparison testing. This report was submitted in partial fulfillment of Contract Number 68-CO-0003, Work Assignment 2-36, under the sponsorship of the U.S. Environmental Protection Agency. This report covers the period from June 1991 to February 1993 and work was completed as of September 1993.