Nitrogen retrofit system saves test time

The Electronics Packaging and Assembly division of AirLiquide provides industrial gases for inerting wave and reflow soldering atmospheres, pertinent equipment, applications and services for the board assembly and packaging industries. Now, it has developed a nitrogen retrofit system.

NitroCool is a turnkey retrofit solution, converting mechanically refrigerated test chambers to liquid nitrogen. The major advantage is to allow extremely fast temperature cooldown rates (in excess of 70K/minute). This retrofit meets the growing use of accelerated stress testing (AST-HALT and HAAS) and environmental stress testing (ESS) in electronics manufacturing, to better detect latent defects or design flaws. AST requires rapid temperature ramp rates of 45K and higher for proper testing. By converting from freon-based mechanical to liquid nitrogen cooling, these ramp rates are easily achieved inside a retrofitted chamber.

An upgrade typically involves the addition of a liquid nitrogen injection system, a PC based control system and a ceramic heater (to prevent premature failure due to overheating caused by air circulation problems). Additional functions are: individually adjustable air flow with dual exhausts, data logging and a vibration capability. Another option is a patented N2 recycling scheme, which reduces operational cost by allowing reuse of nitrogen in other plant applications.

NitroCool is offered as a turnkey package for completely or partially improving the efficiency of existing nitrogen sys-tems. Even minor modifications of nitrogen chambers with NitroCool, says marketing manager Martin Theriault, can improve and optimize processes and help save liquid nitrogen. The test chamber is user-friendly and fail-safe. The operator simply inputs the required ramp rate, temperature set-points and the min. and max. input air temperatures. The sys-tem self-tunes to compensate for cycle changes in the same test charge, automatically altering the parameters to meet process-specific requirements.

In a converted test chamber, after the NitroCool retrofit, a 16-kW transmitter for cellular phones can now be cooled down to –40°C within 30s. This vastly improves the previous setup, which had taken up to three days. The retrofit has extended the life cycle of the test chamber and, at the same time, is freeing up plant space previously needed for the chiller. It also eliminated noise and heat generation along with the necessary compressor and its maintenance. Air Liquide also offers related plant solutions such as vacuum-insulated nit-rogen piping, the supply of N2, the installation of cryogenic tanks, safety and O2 monitoring, as well as the removalof existing compressors and CFC/HFC systems, including customer support and training. Werner Schulz

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