Oxygen content detection system and method of controlling the same

Abstract

An oxygen content detection system comprises a zirconia analyzer, an air source, a mass flow valve and a first throttle valve. The zirconia analyzer comprises a signal processing device, a housing and a probe. The housing is connected to the signal processing device and has a detection port configured to enable gas from a furnace to enter a cavity of the housing via the detection port; the probe is disposed in the cavity of the housing, one end of the probe is connected to the signal processing device and is configured to detect an oxygen concentration in the gas entering the cavity of the housing, the signal processing device receives and processes a detection result of the probe to generate an oxygen concentration signal; the housing is further provided with a communication hole in fluid communication with the cavity of the housing, the air source is configured to be connected to the communication hole through a connection passage to input air to the cavity of the housing. The mass flow valve is disposed in the connection passage and is configured to adjust the amount of air according to the oxygen concentration signal. The first throttle valve is disposed in the connection passage to adjust the flow rate of the air in the connection passage.

Description

Technical Field

[0001] This application relates to reflow ovens, and more particularly to an oxygen content detection system and control method for reflow ovens. Background Technology

[0002] In the fabrication of printed circuit boards (PCBs), a process known as "reflow soldering" is commonly used to mount electronic components onto the PCB. In a typical reflow soldering process, solder paste (e.g., solder grease) is deposited onto selected areas of the PCB, and the leads of one or more electronic components are inserted into the deposited solder paste. The PCB then passes through a reflow oven, where the solder paste is reflowed in a heated zone (i.e., heated to melting or reflow temperature) and then cooled in a cooled zone to electrically and mechanically connect the leads of the electronic components to the PCB. The term "PCB" as used herein includes any type of substrate assembly of electronic components, such as wafer substrates. In a reflow oven, air or a substantially inert gas (e.g., nitrogen) is typically used as the working gas; different working gases are used for PCBs with different process requirements. The furnace chamber of the reflow oven is filled with the working gas, and the PCB undergoes soldering in the working gas as it is conveyed through the furnace by a transport device.

[0003] For reflow ovens that use a substantially inert gas (such as nitrogen) as the working gas, during operation, outside air inevitably enters the oven chamber along with the circuit boards, resulting in the presence of oxygen. If the oxygen concentration exceeds a certain level, it will adversely affect the soldering of electronic components within the reflow oven, such as causing oxidation. Therefore, reflow ovens are typically equipped with a zirconia analyzer to detect the oxygen content and replenish the working gas accordingly to maintain the oxygen concentration at a desired level. During operation, components / parts (such as circuit boards) in the reflow oven release substances at high temperatures. These substances adsorb onto the surface of the zirconia tubes in the zirconia analyzer, causing it to malfunction. In existing technology, operators typically open the oven chamber to allow air to enter and oxidize the substances adsorbed on the zirconia analyzer surface, thus restoring the analyzer to normal operation. This method requires the reflow oven to be stopped during implementation, and after the zirconia analyzer is restored to normal operation, working gas needs to be introduced into the furnace for a certain period of time to ensure that the working gas in the furnace meets the desired requirements, which makes it very cumbersome and uneconomical. Summary of the Invention

[0004] This application provides an oxygen content detection system for detecting the oxygen content in the furnace of a reflow oven, comprising: a zirconia analyzer, an air source, a mass flow valve, and a first throttle valve. The zirconia analyzer includes: a signal processing device, a housing, and a probe. The housing is connected to the signal processing device and has a detection port configured to allow the gas to be detected from the furnace to enter a cavity within the housing. The probe is disposed within the cavity of the housing, with one end connected to the signal processing device. The probe is configured to detect the oxygen concentration in the gas to be detected entering the cavity of the housing. The signal processing device receives and processes the probe's detection result to generate an oxygen concentration signal. The housing also has a connecting hole that is in fluid communication with the cavity of the housing. The air source is configured to be connected to the connecting hole via a connection passage to input air into the cavity of the housing. The mass flow valve is disposed in the connection passage and configured to adjust the amount of air supplied from the air source to the cavity of the housing according to the oxygen concentration signal. The first throttle valve is disposed in the connection passage to adjust the air flow rate in the connection passage.

[0005] According to the oxygen content detection system of this application, the zirconia analyzer is in working condition when the oxygen concentration signal indicates that the oxygen concentration in the gas to be detected from the furnace is within a preset range; and the zirconia analyzer is in a malfunctioning state when the oxygen concentration signal indicates that the oxygen concentration in the gas to be detected from the furnace drops sharply to near 0. When the zirconia analyzer is in a malfunctioning state, oxygen in the air supplied to the cavity of the housing through the air source can react with the substances adsorbed on the probe, thereby restoring the zirconia analyzer from the malfunctioning state to the working state.

[0006] The oxygen content detection system according to this application also includes a controller, which is configured to receive an oxygen concentration signal and is configured to: keep the mass flow valve closed when the oxygen concentration in the furnace indicated by the oxygen concentration signal is within a preset range; and open the mass flow valve to start inputting air from the air source into the cavity of the shell when the oxygen concentration in the furnace indicated by the oxygen concentration signal drops sharply to near 0.

[0007] According to the oxygen content detection system of this application, the controller is configured to retrieve and lock the oxygen concentration signal of the zirconia analyzer before its failure, and to compare the oxygen concentration signal received during the process of supplying air from the air source to the cavity of the housing with the oxygen concentration signal before the failure, and to control the opening of the mass flow valve according to the comparison result, thereby regulating the amount of air supplied from the air source to the cavity of the housing.

[0008] According to the oxygen content detection system of this application, the controller is configured to close the mass flow valve when the oxygen concentration signal received during the process of supplying air from the air source to the cavity of the housing reaches the oxygen concentration signal before the failure of the zirconia analyzer.

[0009] According to the oxygen content detection system of this application, the cavity of the housing of the zirconia analyzer is connected to the peak zone of the reflow oven via the detection port, so as to utilize the temperature of the peak zone to enable oxygen in the air from the air source to react with the substance adsorbed on the probe.

[0010] This application also provides a control method for an oxygen content detection system for a reflow oven. The oxygen content detection system includes a zirconia analyzer, which is capable of detecting the oxygen content of the gas in the reflow oven. The control method includes: when the reflow oven is operating, monitoring the oxygen concentration signal generated by the zirconia analyzer; when the oxygen concentration signal from the zirconia analyzer, indicating a sharp drop in the oxygen concentration in the gas to be detected from the reflow oven, drops to near zero, determining that the zirconia analyzer is in a malfunction state, and performing the following steps to restore the zirconia analyzer from the malfunction state to the operating state: inputting air into the cavity containing the probe of the zirconia analyzer; receiving the oxygen concentration signal generated by the zirconia analyzer during the air input process and comparing it with the oxygen concentration signal before the zirconia analyzer malfunction; when the oxygen concentration signal received during the air input process reaches the oxygen concentration signal before the zirconia analyzer malfunction, determining that the zirconia analyzer is in the operating state, and stopping the input of air into the cavity containing the probe of the zirconia analyzer.

[0011] According to the method of this application, inputting air into the cavity containing the probe of the zirconia analyzer includes inputting air from an air source into the cavity containing the probe of the zirconia analyzer; and the method further includes: providing a mass flow valve and a first throttle valve on the connection path between the air source and the zirconia analyzer to control the amount and speed of air.

[0012] According to the method of this application, the reflow oven remains operational when the step of restoring the zirconia analyzer from a failed state to a working state is performed.

[0013] According to the method of this application, a zirconia analyzer detects the gas from the peak zone of a reflow oven, so as to utilize the temperature of the peak zone to enable oxygen in the air from the air source to react with the substance adsorbed on the probe. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of an embodiment of the reflow oven 100 and its gas control system of this application;

[0015] Figure 2 yes Figure 1 A schematic diagram of the oxygen content detection system 120 of the gas control system shown;

[0016] Figure 3 Is adopted Figure 2A schematic diagram of some steps of the control method 300 for the oxygen content detection system 120 shown;

[0017] Figure 4 yes Figure 1 A schematic diagram of one embodiment of the controller 121. Detailed Implementation

[0018] Various specific embodiments of this application will now be described with reference to the accompanying drawings, which form part of this specification. It should be understood that although directional terms such as "front," "rear," "upper," "lower," "left," "right," "inner," "outer," "top," and "bottom" are used in this application to describe various exemplary structural parts and elements, their use is merely for illustrative purposes and is based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in this application can be arranged in different orientations, these directional terms are for illustrative purposes only and should not be considered as limiting.

[0019] Figure 1 This is a schematic diagram of one embodiment of the reflow oven 100 and its gas control system according to this application, illustrating the general components of the reflow oven 100 and its gas control system. Figure 1 As shown, the reflow oven 100 includes a furnace chamber 112, a preheating zone 101, a homogenizing zone 103, a peaking zone 105, and a cooling zone 107. A barrier exhaust zone 109 is also provided between the peaking zone 105 and the cooling zone 107. The furnace chamber 112 extends through the preheating zone 101, homogenizing zone 103, peaking zone 105, and cooling zone 107, and these zones are fluidly connected through the furnace chamber 112. The furnace chamber 112 includes an inlet 114 and an outlet 116. The reflow oven 100 also includes a conveying device 118, which extends through the furnace chamber 112 and is used to feed the circuit board to be processed into the furnace chamber 112 through the inlet 114, and to output the circuit board processed by the reflow oven 100 from the furnace chamber 112 through the outlet 116.

[0020] The preheating zone 101, the uniform temperature zone 103, and the peak temperature zone 105 together form the heating zone 106. Figure 1In the illustrated embodiment, the heating zone 106 includes three preheating zones 101, three homogenizing zones 103, and three peak zones 105. The preheating zones 101, homogenizing zones 103, and peak zones 105 are sequentially connected, and their temperatures gradually increase. In the preheating zones 101 and homogenizing zones 103, the circuit board is heated, and a portion of the flux in the solder paste dispensed on the circuit board vaporizes. The temperature in the peak zones 105 is higher than that in the preheating zones 101 and homogenizing zones 103, and the solder paste melts in the peak zones 105. The peak zones 105 are also higher-temperature areas where VOCs (such as rosin and resin) will vaporize. Figure 1 In the illustrated embodiment, the reflow oven 100 includes three cooling zones 107. After the circuit board is conveyed from the heating zone 106 into the cooling zone 107, the solder paste is cooled and solidified on the soldering areas of the circuit board, thereby connecting electronic components to the circuit board. It is worth noting that the number of the preheating zone 101, the homogenizing zone 103, the peaking zone 105, and the cooling zone 107 of the reflow oven can be varied, and is not limited to, depending on the product to be soldered and different soldering processes. Figure 1 The example shown.

[0021] A barrier exhaust zone 109 is provided in the connection area between the heating zone 106 and the cooling zone 107. The barrier exhaust zone 109 can extract or exhaust gas from the furnace 112, thereby preventing or reducing the entry of gas containing volatile pollutants from the heating zone 106 into the cooling zone 107. In addition, by extracting or exhausting gas from the furnace 112, the barrier exhaust zone 109 can also serve as a heat insulation zone, separating the high-temperature heating zone 106 from the low-temperature cooling zone 107.

[0022] The reflow oven 100 of this application uses nitrogen as its working gas. The reflow oven 100 is equipped with a working gas source 130 for supplying clean working gas to the furnace chamber 112. The reflow oven 100 also includes gas barrier zones 108 located at the inlet 114 and outlet 116 of the furnace chamber 112. The gas barrier zones 108 form a nitrogen curtain by supplying nitrogen towards the furnace chamber 112, which prevents air from the external environment from entering the furnace chamber 112. The reflow oven 100 is also equipped with an exhaust device (not shown) for discharging gases containing volatile contaminants from the furnace chamber 112. The exhaust device is typically connected to a high-temperature area of ​​the reflow oven 100, such as the homogenization zone 103, the peaking zone 105, or the barrier exhaust zone 109. The exhaust device remains operational while the reflow oven 100 is processing circuit boards to maintain the cleanliness of the gas in the furnace chamber 112. During this process, clean nitrogen gas needs to be continuously supplied from the working gas source 130 to maintain the working atmosphere and working pressure required by the furnace 112.

[0023] Although a gas barrier zone 108 is provided to form a nitrogen curtain, as the conveyor 118 transports the circuit boards into or out of the furnace 112, a relatively small amount of ambient air inevitably enters the furnace 112. Therefore, the working gas in the furnace 112 will always contain oxygen. Different welding processes have different requirements for the oxygen concentration level in the furnace 112, typically ranging from 500 to 5000 PPM (parts per million). It is desirable to maintain the oxygen concentration in the furnace 112 near the value required by the specific welding process. This satisfies the welding quality requirements while conserving nitrogen.

[0024] Therefore, the reflow oven 100 of this application is also equipped with a gas control system. See still... Figure 1 The gas control system includes an oxygen content detection system 120 and a nitrogen gas intake system 170. The oxygen content detection system 120 is used to detect the oxygen content in the furnace 112 of the reflow oven 100. The nitrogen gas intake system 170 determines whether to add nitrogen to the furnace 112 based on the detection result of the oxygen content detection system 120, thereby maintaining the oxygen concentration in the furnace 112 at the desired level.

[0025] The oxygen content detection system 120 includes a zirconia analyzer 140, an air source 135, a first air inlet valve device 137, and a controller 121. The zirconia analyzer 140 contacts the gas in the peak zone 105 of the reflow oven 100 to detect the oxygen concentration in the peak zone 105. In the reflow oven 100, the peak zone 105 has the highest temperature and is also the area that significantly affects the welding quality during the welding process. Therefore, detecting the oxygen concentration in the peak zone 105 and adjusting the nitrogen supply based on the detected oxygen concentration can maintain the oxygen concentration in the peak zone 105 at the target set value required by the welding process, thereby significantly improving the welding quality. Furthermore, as mentioned earlier, the peak zone 105 is a region with higher temperatures where VOCs (such as rosin and resin) will vaporize. Therefore, vaporized VOCs will adsorb onto the surface of the probe of the zirconia analyzer 140. When the amount of adsorbed substances on the probe surface increases to a certain level, the probe will lose its sensitivity to oxygen, thus causing the zirconia analyzer 140 to malfunction. Air source 135 is connected to zirconia analyzer 140 via first air intake valve device 137. Air source 135 is configured to restore zirconia analyzer 140 from a failed state to a working state by supplying air to zirconia analyzer 140. Figure 2 and Figure 3 A more detailed description will follow.

[0026] The nitrogen intake system 170 includes a working gas source (nitrogen source) 130, a second intake valve device 138, a third intake valve device 139, and a controller 121. Specifically, the oxygen content detection system 120 is communicatively connected to the nitrogen intake system 170 via the controller 121. The second intake valve device 138 and the third intake valve device 139 controllably connect the working gas source 130 to the furnace 112 to input nitrogen into the furnace 112. The controller 121 controls the opening degree of the second intake valve device 138 and the third intake valve device 139 based on the oxygen concentration signal measured by the oxygen content detection system 120, thereby adjusting the amount of nitrogen input into the furnace 112 and thus regulating the oxygen concentration in the furnace 112. The opening degree represents the extent to which the valves are open, ranging from 0% to 100%, where an opening degree of 0% indicates the valve is closed, and an opening degree of 100% indicates the valve is fully open.

[0027] exist Figure 1 In the illustrated embodiment, both the second intake valve device 138 and the third intake valve device 139 include a pressure proportional valve and a throttle valve. Specifically, the second intake valve device 138 includes a second pressure proportional valve 131 and a second throttle valve 133, and the third intake valve device 139 includes a third pressure proportional valve 132 and a third throttle valve 134. The second pressure proportional valve 131 and the third pressure proportional valve 132 are connected to the working gas source 130 and can controllably adjust the amount of nitrogen received from the working gas source 130. The second throttle valve 133 and the third throttle valve 134 are respectively connected to the second pressure proportional valve 131 and the third pressure proportional valve 132 and can adjust the gas flow rate according to the amount of gas adjusted by the second pressure proportional valve 131 and the third pressure proportional valve 132.

[0028] The second inlet valve device 138 connects the preheating zone 101 to the working gas source 130 in fluid communication, and the third inlet valve device 139 connects the cooling zone 107 to the working gas source 130 in fluid communication. In each zone of the heating zone 106, the gas temperature gradually increases from left to right, and different zones have different gas temperature requirements to meet different welding process requirements. Supplying nitrogen to the furnace 112 from the preheating zone 101 near the inlet 114 and the cooling zone 107 near the outlet 116 allows the ambient temperature nitrogen from the working gas source 130 to enter the lower temperature zones, thus avoiding a significant impact on the gas temperature in the higher temperature zones.

[0029] Figure 2 yes Figure 1 The schematic diagram of the oxygen content detection system 120 in the gas control system shown illustrates the specific components of the oxygen content detection system 120. (See diagram for details.) Figure 2As shown, air source 135 is connected to zirconia analyzer 140 via connection passage 246. A first intake valve device 137 is disposed in connection passage 246. The first intake valve device 137 includes a mass flow valve 244 and a first throttle valve 245. The mass flow valve 244 regulates the amount of air supplied from air source 135 to zirconia analyzer 140, and the first throttle valve 245 regulates the airflow rate in connection passage 246. Viewed from air source 135 to zirconia analyzer 140, the mass flow valve 244 and the first throttle valve 245 are sequentially disposed in connection passage 246. That is, during the flow of air from air source 135 to zirconia analyzer 140, the air first passes through mass flow valve 244 to regulate the total amount of air flowing to zirconia analyzer 140. It should be noted that compared to the second pressure proportional valve 131 and the third pressure proportional valve 132, mass flow valve 244 can achieve more precise control over the amount of air entering zirconia analyzer 140. A certain amount of air, after being regulated by mass flow valve 244, then passes through first throttle valve 245. First throttle valve 245 regulates the airflow rate, ensuring it is within an appropriate range to prevent excessive airflow into the zirconia analyzer 140, which could lower the temperature inside the analyzer. Ideally, the temperature inside the zirconia analyzer 140 should be maintained within a certain range. This is because the oxidation of substances adsorbed on the zirconia analyzer 140 requires specific temperature conditions. If the airflow rate is too high, the temperature inside the analyzer 140 will drop, affecting the effective utilization of the peak temperature zone 105 by the air entering the analyzer 140 to oxidize the adsorbed substances. Furthermore, the zirconia analyzer 140 requires high-temperature conditions (typically above 700°C) to operate normally. When the temperature inside the zirconia analyzer 140 does not reach the high-temperature condition (e.g., drops below 700°C), even if the air has actually oxidized the substances adsorbed on the zirconia analyzer 140, it is impossible to determine whether the adsorbed substances have been completely oxidized based on the oxygen concentration signal of the zirconia analyzer 140, and therefore it is impossible to determine whether the zirconia analyzer has returned to its working state. As a result, the air source 135 continuously supplies air into the zirconia analyzer 140. Of course, in other embodiments, a heater can be provided in the connection passage 246 so that the air reaches the desired temperature, for example, close to or greater than 700°C, before entering the zirconia analyzer 140.

[0030] The zirconia analyzer 140 includes a signal processing unit 249, a housing 251, and a probe 242. The housing 251 is connected to the signal processing unit 249. A large portion of the housing 251 is disposed within the gas collection chamber 243 of the peak zone 105 of the reflow oven 100, for contact with the working gas to be detected. The arrangement of the gas collection chamber 243 facilitates the installation and removal of the zirconia analyzer 140; for example, the gas collection chamber 243 can be located in a place easily accessible to the operator. The gas collection chamber 243 is in fluid communication with the peak zone 105 via connecting pipes 247 and 248, and the working gas flows into and / or out of the gas collection chamber 243 via a fan (not shown) disposed within the furnace 112. Alternatively, in other embodiments, the housing 251 of the zirconia analyzer 140 may be directly inserted into the peak zone 105.

[0031] The housing 251 has a cavity 252, and the probe 242 is disposed within the cavity 252 of the housing 251 and connected to the signal processing device 249. The end of the housing 251 opposite to the signal processing device 249 has a detection port 253, through which the working gas enters the cavity 252 of the zirconia analyzer 140 and contacts the probe 242 of the zirconia analyzer 140. The probe 242 is a zirconia tube, which is a good oxygen ion conductor at high temperatures (typically above 700°C). The zirconia tube is generally a closed-end cylindrical tube (not shown), with a first platinum electrode (not shown) on the outer side and a second platinum electrode (not shown) on the inner side. The first platinum electrode is in contact with the working gas, and the second platinum electrode is in contact with the reference air. At high temperatures, due to the difference in oxygen content between the working gas and the reference air, the oxygen concentration difference causes oxygen ions to migrate from the second platinum electrode to the first platinum electrode, and the resulting potential causes oxygen ions to migrate in the opposite direction from the first platinum electrode to the second platinum electrode. Once these two migrations reach equilibrium, a potential signal related to the oxygen concentration difference is generated between the first platinum electrode and the second platinum electrode. The signal processing device 249 generates an oxygen concentration signal in the working gas based on this potential signal.

[0032] The end of the housing 251 near the signal processing device 249 is also provided with a connecting hole 250. Air from the air source 135 enters the cavity 252 of the housing 251 through the connecting hole 250 to restore the zirconia analyzer 140 from a failed state to a working state. Specifically, at high temperatures, the air introduced into the zirconia analyzer 140 can oxidize substances such as VOCs adsorbed on the outside of the probe 242, thereby restoring the zirconia analyzer 140 from a failed state to a working state.

[0033] The controller 121 is communicatively connected to the signal processing device 249 and the mass flow valve 244 of the zirconia analyzer 140. It can control the opening of the mass flow valve 244 based on the oxygen concentration signal generated by the signal processing device 249, thereby regulating the amount of air entering the zirconia analyzer 140. The specific control process will be combined with... Figure 3 Describe it.

[0034] Figure 3 Is adopted Figure 2 The schematic diagram illustrates some steps of the control method 300 for the oxygen content detection system 120, used to show the method for determining whether the zirconia analyzer 140 has malfunctioned and restoring it from a malfunctioning state to a normal state. During normal operation of the reflow oven 100, the oxygen content detection system 120 monitors the oxygen content in the peak region 105 of the reflow oven 100 in real time. Specifically, as mentioned above, different welding processes have different requirements for the oxygen concentration level in the furnace 112, and a certain range of deviation in oxygen concentration is generally allowed. Assuming that the welding process requires an oxygen concentration of 500 PPM and the deviation is 20%, then an oxygen concentration of 600 PPM indicated by the oxygen concentration signal of the zirconia analyzer 140 can be considered as a normal operating condition. When the oxygen concentration exceeds 600 PPM, controller 121 opens the second inlet valve 138 and the third inlet valve 139, thereby introducing nitrogen gas from the working gas source 130 into the reflow oven 100. When the oxygen concentration signal indicated by the zirconia analyzer 140 reaches 500 PPM, controller 121 closes the second inlet valve 138 and the third inlet valve 139. However, when the zirconia analyzer 140 malfunctions—that is, when the amount of VOCs and other substances released from the product adsorbed on the surface of the probe 242 of the zirconia analyzer 140 reaches a certain level—the probe 242 of the zirconia analyzer 140 will not be able to make sufficient contact with the working gas, thus losing its sensitivity to oxygen.

[0035] exist Figure 3 In step 361, the oxygen concentration indicated by the oxygen concentration signal of the zirconia analyzer 140 is monitored to see if it drops sharply to near 0. If yes, the zirconia analyzer 140 is determined to be in a malfunctioning state, and the process proceeds to step 362; if no, the zirconia analyzer 140 is determined to be in normal working condition, and step 361 continues. It should be noted that "the oxygen concentration indicated by the oxygen concentration signal of the zirconia analyzer 140 drops sharply to near 0" means that the oxygen concentration indicated by the oxygen concentration signal drops from 600 PPM or less (e.g., 450 PPM) to near 0 (e.g., 20 PPM or lower) in one second or less.

[0036] The controller 121 stores the oxygen concentration signal of the zirconia analyzer 140 in real time throughout the process. When the zirconia analyzer 140 malfunctions, the controller 121 retrieves and locks the oxygen concentration signal of the zirconia analyzer 140 before the malfunction. For example, if the oxygen concentration signal of the zirconia analyzer 140 indicates that the oxygen concentration drops from 450 PPM to near 0 in one second or less, then the oxygen concentration signal before the malfunction is the oxygen concentration signal corresponding to the 450 PPM oxygen concentration.

[0037] In step 362, controller 121 opens mass flow valve 244 to allow air to flow from air source 135 to zirconia analyzer 140, and then proceeds to step 363. It should be noted that in this embodiment, controller 121 contains a nitrogen inlet control module and a zirconia recovery module. When zirconia analyzer 140 is working normally, controller 121 calls the nitrogen inlet control module; at this time, the zirconia recovery module is not called, meaning mass flow valve 244 is closed. When a zirconia analyzer 140 failure is detected, controller 121 switches to the zirconia recovery module; at this time, the nitrogen inlet control module is not called, and both the second inlet valve device 138 and the third inlet valve device 139 are closed. Of course, the controller 121 can also simultaneously call the nitrogen gas inlet control module and the zirconia recovery module. During the process of restoring the zirconia analyzer 140 from a failed state to a working state, nitrogen gas is introduced into the reflow oven 100 to prevent the oxygen content in the reflow oven 100 from exceeding the standard when the oxygen content in the reflow oven 100 cannot be detected, thus preventing adverse effects on the product.

[0038] In step 363, while controlling the mass valve 244 to input air into the zirconia analyzer 140, the controller 121 receives the oxygen concentration signal generated by the zirconia analyzer 140, compares the received oxygen concentration signal with the oxygen concentration signal before the zirconia analyzer 140 failed, and determines whether the oxygen concentration signal has recovered to the level before the zirconia analyzer failed. If yes, proceed to step 364; if no, proceed to step 362.

[0039] During the process of comparing the received oxygen concentration signal with the oxygen concentration signal before the zirconia analyzer 140 malfunctions, the controller 121 also controls the opening of the mass flow valve 244 based on the comparison result, thereby adjusting the amount of air entering the zirconia analyzer 140. For example, as the difference between the oxygen concentration signal received by the controller 121 and the oxygen concentration signal before the zirconia analyzer 140 malfunctions becomes smaller, the controller 121 controls the mass flow valve 244 to reduce its opening, thus reducing the amount of air entering the zirconia analyzer 140. This dynamic control, combined with the precise adjustment of the mass flow valve 244, ensures that after oxidizing the VOCs and other substances adsorbed on the zirconia analyzer 140, only a very small amount of air remains, and the remaining air will not affect the subsequent operation of the zirconia analyzer 140.

[0040] In step 364, controller 121 closes mass flow valve 244, stopping the supply of air to zirconia analyzer 140. When the oxygen concentration signal received by controller 121 from zirconia analyzer 140 returns to the level before zirconia analyzer 140 failed, that is, when the oxygen concentration signal received by controller 121 from zirconia analyzer 140 is the same (equal) to the oxygen concentration signal before zirconia analyzer 140 failed, controller 121 determines that zirconia analyzer 140 has recovered from the failed state to the working state. At this time, controller 121 closes mass flow valve 244, stops the supply of air to zirconia analyzer 140, and switches to nitrogen intake control module.

[0041] Figure 4 yes Figure 1 A schematic diagram of one embodiment of the controller 121 is shown. The controller 121 includes a bus 427, a processor 422, an input interface 423, an output interface 424, and a memory 425 having a control program 426. The processor 422, the input interface 423, the output interface 424, and the memory 425 are communicatively connected via the bus 427, enabling the processor 422 to control the operation of the input interface 423, the output interface 424, and the memory 425. The memory 425 is used to store programs, instructions, and data. The processor 422 reads programs, instructions, and data from the memory 425 and can write data to the memory 425.

[0042] Input interface 423 receives signals and data via connection 428, such as signals indicating the working status of reflow oven 100, oxygen concentration signals from zirconia analyzer 140, and various manually input parameters. Output interface 424 sends signals and data via connection 429, such as control signals to adjust the opening of mass flow valve 244, second pressure proportional valve 131, and third pressure proportional valve 132. Memory 425 stores control programs, preset target oxygen concentration values, oxygen concentration signals before zirconia analyzer 140 failure, nitrogen inlet control module data, and zirconia recovery module data. Various parameters can be preset during the manufacturing process or set manually or by importing data during use. Processor 422 obtains various signals, data, programs, and instructions from input interface 423 and memory 425, processes them accordingly, and outputs them through output interface 424.

[0043] The oxygen content detection system 120 of this application enables the zirconia analyzer 140 to return to normal operation after failure, and can achieve "online recovery," that is, to perform failure recovery of the zirconia analyzer 140 while the reflow oven 100 is still in normal operation, without having to stop the reflow oven 100. Therefore, the oxygen content detection system 120 of this application can achieve failure recovery of the zirconia analyzer 140 in a time-saving and cost-effective manner.

[0044] Although this application will be described with reference to the specific embodiments shown in the accompanying drawings, it should be understood that the oxygen content detection system of this application can have many variations without departing from the spirit, scope, and context of the teachings of this application. Those skilled in the art will also recognize that different ways of modifying the structural details of the embodiments disclosed in this application fall within the spirit and scope of this application and the claims.

Claims

1. An oxygen content detection system for detecting the oxygen content in the furnace of a reflow soldering furnace, characterized in that... The oxygen content detection system includes: Zirconia analyzer, the zirconia analyzer comprising: Signal processing device; A housing connected to the signal processing device, the housing having a detection port configured to allow a gas to be detected from the furnace to enter a cavity within the housing via the detection port; and A probe is disposed within the cavity of the housing, one end of the probe is connected to the signal processing device, and the probe is configured to detect the oxygen concentration in the gas to be detected entering the cavity of the housing. The signal processing device receives and processes the detection result of the probe to generate an oxygen concentration signal. The housing is also provided with a connecting hole, which is in fluid communication with the cavity of the housing; An air source configured to be connected to the communicating hole via a connection passage to supply air into the cavity of the housing; A mass flow valve, disposed in the connection passage and configured to adjust the amount of air supplied from the air source to the cavity of the housing according to the oxygen concentration signal; and A first throttle valve is disposed in the connection passage to regulate the airflow rate in the connection passage.

2. The oxygen content detection system according to claim 1, characterized in that: When the oxygen concentration signal indicates that the oxygen concentration in the gas to be detected from the furnace is within a preset range, the zirconia analyzer is in working condition; when the oxygen concentration signal indicates that the oxygen concentration in the gas to be detected from the furnace drops sharply to near 0, the zirconia analyzer is in a malfunctioning state. When the zirconia analyzer is in the failed state, oxygen in the air supplied to the cavity of the housing through the air source can react with the substance adsorbed on the probe, so that the zirconia analyzer can be restored from the failed state to the working state.

3. The oxygen content detection system according to claim 2, characterized in that: It also includes a controller configured to receive the oxygen concentration signal and configured to: keep the mass flow valve closed when the oxygen concentration in the furnace indicated by the oxygen concentration signal is within a preset range; and open the mass flow valve to start inputting air from the air source into the cavity of the housing when the oxygen concentration in the furnace indicated by the oxygen concentration signal drops sharply to near 0.

4. The oxygen content detection system according to claim 3, characterized in that: The controller is configured to retrieve and lock the oxygen concentration signal of the zirconia analyzer before its failure, and to compare the oxygen concentration signal received during the process of supplying air from the air source to the cavity of the housing with the oxygen concentration signal before the failure, and to control the opening of the mass flow valve according to the comparison result, thereby adjusting the amount of air supplied from the air source to the cavity of the housing.

5. The oxygen content detection system according to claim 4, characterized in that: The controller is configured to close the mass flow valve when the oxygen concentration signal received during the delivery of air from the air source to the cavity of the housing reaches the oxygen concentration signal prior to the failure of the zirconia analyzer.

6. The oxygen content detection system according to claim 1, characterized in that: The cavity of the housing of the zirconia analyzer is connected to the peak region of the reflow oven via the detection port, so that the temperature of the peak region allows oxygen in the air from the air source to react with the substance adsorbed on the probe.

7. A control method for the oxygen content detection system as described in claim 1, characterized in that... include: When the reflow oven is operating, the oxygen concentration signal generated by the zirconia analyzer is monitored. When the oxygen concentration signal from the zirconia analyzer, indicating a sharp drop in the oxygen concentration in the gas to be tested from the reflow oven, drops to near zero, the zirconia analyzer is determined to be in a malfunctioning state. The following steps are then performed to restore the zirconia analyzer from the malfunctioning state to the operating state: Air is introduced into the cavity of the zirconia analyzer; During the air input process, the oxygen concentration signal generated by the zirconia analyzer is received and compared with the oxygen concentration signal before the zirconia analyzer failed. When the oxygen concentration signal received during the air input process reaches the oxygen concentration signal before the zirconia analyzer malfunctions, it is determined that the zirconia analyzer is in the working state, and the input of air into the cavity of the zirconia analyzer is stopped.

8. The method according to claim 7, characterized in that: Introducing air into the cavity containing the probe of the zirconia analyzer includes introducing air into the cavity from an air source.

9. The method according to claim 7, characterized in that: The reflow oven remains operational while the step of restoring the zirconia analyzer from the failed state to the working state is performed.

10. The method according to claim 9, characterized in that... Also includes: The zirconia analyzer detects the gas from the peak region of the reflow oven, so that the temperature of the peak region allows oxygen in the air from the air source to react with the substances adsorbed on the probe.

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