Oxygen sensor with micro oxygen ion current for detecting trace oxygen of N2 in high-temperature welding equipment

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Reflow soldering technology is well-known in the field of electronics manufacturing. The components on various circuit boards used in computers are soldered to the circuit boards using this process. The device contains a heating circuit that heats air or nitrogen to a high enough temperature, which is then blown over the circuit board where the components are to be attached, causing the solder on both sides of the components to melt and bond them to the main board. The advantage of this process is that the temperature is easy to control, oxidation can be avoided during welding, and the manufacturing cost is easier to manage. As many electronic products evolve toward being smaller, lighter, and more highly compact, especially with the widespread use of handheld devices, existing component material technologies face severe challenges, which in turn creates opportunities for rapid development. As a shielding gas, nitrogen’s main role in welding is to remove oxygen during the welding process, improve weldability, and prevent re-oxidation. This method has been in use for a long time and is widely applied. Due to cost considerations, nitrogen protection is generally chosen. To ensure the welding quality of electronic products under high-temperature conditions, it is necessary to strictly control the oxygen content in reflow soldering and peak welding equipment. This requires the use of oxygen sensors to monitor the oxygen level inside the furnace, ranging from normal air levels (20.95%) to low-oxygen environments (around 5 ppm), in order to improve the manufacturing process and enhance product quality. In the SMT industry, to ensure the welding quality of electronic products under high-temperature conditions, lead-free processes are employed in current wave soldering and reflow soldering techniques, which requires raising the welding temperature (sometimes as high as 260°C). Raising the welding temperature accelerates the oxidation of the welding surface, thereby affecting the welding quality. To this end, it is necessary to protect the welded area from an oxygen-rich environment. Strict control of the oxygen content in reflow soldering and wave soldering equipment requires testing ranges that extend from normal air conditions (20.95%) to environments with low oxygen concentrations (around 5 ppm). Currently, the shielding gas used in lead-free soldering processes is pure nitrogen, with its concentration generally ranging from 99.9% to 99.999%. At this point, an oxygen analyzer is needed to measure the trace amount of oxygen inside, and a feedback loop is used to control the oxygen concentration, thereby regulating the welding process. One of the oxygen sensors offered by Gongcai.com, the Austrian SENSORE micro-oxygen ion current oxygen sensor – SO-B0-001 – uses oxygen ions as the charge carriers in the zirconia electrolyte; therefore, when a voltage is applied to the zirconia cell, oxygen ions are drawn toward the anode through the zirconia disc. If a perforated cover is placed over the cathode of the electrolyzer, the rate at which oxygen flows toward the cathode will be restricted. Limited by this rate, as the applied voltage increases gradually, the current in the electrolyzer reaches saturation. This saturation current is known as the limit current, and it is proportional to the oxygen concentration in the surrounding environment.