JP2005246476A - Method for management of in-furnace atmosphere of reflow soldering equipment and reflow soldering equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for management of an in-furnace atmosphere by which the oxygen atmosphere in gaseous nitrogen in a furnace of reflow soldering equipment is kept at a desired value and reflow soldering equipment which realizes the method. <P>SOLUTION: The reflow soldering equipment which performs reflow soldering within the furnace 1 supplied with the gaseous nitrogen is equipped with: gaseous nitrogen supplying means 8 to 23 capable of supplying the gaseous nitrogen into the furnace 1; a means 24 for detecting the oxygen concentration in the furnace 1; and control means 25 and 26 for controlling the oxygen concentration of the gaseous nitrogen supplied from the gaseous nitrogen supplying means 8 to 23 according to the oxygen concentration in the furnace 1 detected by the detecting means 24. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for maintaining the oxygen concentration in a furnace atmosphere constant in a reflow soldering apparatus that performs reflow soldering in a furnace supplied with nitrogen gas.

  The reflow soldering apparatus performs reflow soldering by heating and melting cream solder on a substrate in a high temperature atmosphere in a furnace while conveying a printed circuit board on which electronic components are mounted by a conveyor. At this time, if the inside of the furnace is filled with air, the cream solder is oxidized by oxygen and the quality of the soldering part is deteriorated. Therefore, reflow soldering is currently performed by supplying nitrogen gas into the furnace. A soldering apparatus is generally used.

On the other hand, if the oxygen concentration in the nitrogen gas in the furnace fluctuates, the quality of the soldering part will not be maintained, so the furnace atmosphere is managed so that the oxygen concentration in the furnace is maintained at the desired low oxygen concentration. (For example, refer to Patent Document 1).
JP-A-3-101296

  However, in the above technique, when nitrogen gas having a low oxygen concentration (for example, 50 to 30 ppm) is continuously supplied into the furnace and the oxygen concentration in the furnace becomes an unnecessary low oxygen concentration, air (oxygen) It is not an efficient control method.

  The problem to be solved by the present invention is to eliminate the above-mentioned waste, and to maintain the oxygen concentration in the nitrogen gas in the furnace at a desired value in the reflow soldering apparatus, and the reflow realizing the same It is to provide a soldering apparatus.

In order to solve the above problems, the present invention employs the following means. That is,
The reflow soldering apparatus according to the present invention is a reflow soldering apparatus that performs reflow soldering in a furnace to which nitrogen gas is supplied, and is supplied to the furnace in accordance with the oxygen concentration in the furnace. The oxygen concentration of the nitrogen gas is automatically adjusted.

  The reflow soldering apparatus of the present invention is a reflow soldering apparatus that performs reflow soldering in a furnace to which nitrogen gas is supplied, a nitrogen gas supply means capable of supplying nitrogen gas into the furnace, Means for detecting the oxygen concentration, and control means for controlling the oxygen concentration of the nitrogen gas supplied from the nitrogen gas supply means in accordance with the oxygen concentration in the furnace detected by the detection means. Features.

  In addition, in the above, when the nitrogen gas supplied into the furnace is generated separately from the air, it is substantially the same even if the nitrogen concentration of the nitrogen gas is controlled instead of controlling the oxygen concentration of the nitrogen gas. It is.

  Since the present invention has the above-described configuration, the oxygen concentration of the nitrogen gas supplied to the furnace is decreased / increased in accordance with the increase / decrease of the oxygen concentration in the furnace atmosphere, and the furnace atmosphere is always maintained. It is controlled to a predetermined oxygen concentration.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the reflow soldering apparatus includes three preheating chambers 2, one reflow chamber 3, and one cooling chamber 4 in the furnace 1 in the conveying direction of the conveyor 5. It has in order along. 6 is a blower, 7 is a heater. The supply port of the nitrogen gas supply pipe 8 passes through the wall of the furnace 1 and faces the furnace 1, and a certain amount of nitrogen gas is continuously supplied into the furnace 1 from the nitrogen gas supply system 9 through the nitrogen gas supply pipe 8. To be supplied.

  The nitrogen gas supply system 9 for carrying out the method of the present invention employs a PSA (Pressure Swing Adsorption) type nitrogen gas generation method in which nitrogen gas is separated from a raw material gas to generate nitrogen gas, and an adsorbent As a molecular sieve charcoal (Molecular Seizing Carbon) is used. Molecular sieve charcoal has different adsorption rates between nitrogen and oxygen, and can preferentially adsorb oxygen under pressure and separate nitrogen from air. The adsorbed oxygen can be desorbed under reduced pressure, and molecular sieve charcoal can be regenerated.

  As shown in FIG. 2, the nitrogen gas supply system 9 includes two adsorption tanks 10 and 11 filled with molecular sieve charcoal, and these two adsorption tanks 10 and 11 respectively have a high pressure adsorption process and a low pressure. By repeating the desorption (regeneration) step alternately, nitrogen is continuously separated from the air and nitrogen gas is supplied. Hereinafter, it demonstrates in detail based on FIGS.

  In FIG. 2, 12 is an inverter type compressor for supplying compressed air, 13 is an inverter, 14 and 15 are air supply valves, 16 and 17 are exhaust valves, 18 and 19 are product supply valves, and 20 and 21 are pressure equalization valves. , 22 are product discharge valves, and any of the valves 14 to 22 is composed of a solenoid valve. 23 is a product nitrogen gas storage tank for storing nitrogen gas. Reference numeral 24 denotes an oxygen concentration meter for detecting the oxygen concentration in the atmosphere in the furnace 1, and a detection end 24 a of the oxygen concentration meter 24 is inserted into the furnace 1. The output terminal of the oxygen concentration meter 24 is connected to the PID controller 25, and the value of the oxygen concentration detected by the oxygen concentration meter 24 is input to the controller 25. The controller 25 controls the rotation speed of the compressor 12 by controlling the frequency of the inverter 13 based on the deviation between the detected value of the oxygen concentration meter 24 and the set oxygen concentration value of the atmosphere in the furnace 1. Further, the detected value of the oximeter 24 and the set oxygen concentration value are input to the sequencer (PLC) 26 through the controller 25. The sequencer 26 controls the opening and closing of the valves 14 to 22, for example, based on the deviation between the detected value of the oxygen concentration meter 24 and the set oxygen concentration value of the atmosphere in the furnace 1. Automatically adjusts the desorption switching cycle.

  Hereinafter, the operation of the nitrogen gas supply system 9 will be described.

  In the PSA system 9, the air pressurized by the compressor 12 is selectively sent alternately to the two adsorption tanks 10 and 11, and the oxygen is adsorbed and removed in the adsorption tank into which the pressurized air is sent. Nitrogen gas is sent to the product storage tank 23. That is, when one adsorption tank 10 is in the adsorption process and the other adsorption tank 11 is in the desorption process, the valves 14 to 22 are in the following state. The air supply valve 14, the exhaust valve 17, and the product supply valve 18 are open, and the air supply valve 15, the exhaust valve 16, the product supply valve 19, and the pressure equalizing valves 20, 21 are closed. In this state, the air pressurized by the compressor 12 is sent into one adsorption tank 10, and the pressurized air adsorbs and removes oxygen in the one adsorption tank 10, and nitrogen gas is sent to the product storage tank 23. . On the other hand, in the other adsorption tank 11, the oxygen adsorbed in the previous adsorption process is desorbed and exhausted.

  When the above adsorption process and desorption process are performed for a predetermined time, next, one adsorption tank 10 is switched to the desorption process, and the other adsorption tank 11 is switched to the adsorption process. That is, the air supply valve 15, the exhaust valve 16, and the product supply valve 19 are opened, and the air supply valve 14, the exhaust valve 17, the product supply valve 18, and the pressure equalizing valves 20, 21 are closed. The air pressurized by the compressor 12 is sent to the other adsorption tank 11, the oxygen is adsorbed and removed from the pressurized air in the other adsorption tank 11, and nitrogen gas is sent to the product storage tank 23. In one adsorption tank 10, the oxygen adsorbed in the previous adsorption process is desorbed and exhausted.

  The pressure equalizing valves 20 and 21 are opened in the middle of switching from the adsorption process to the desorption process to equalize the pressure in the two adsorption tanks 10 and 11. That is, at the end of the adsorption process, all the valves 14 to 19 are once closed, and the pressure equalizing valves 20 and 21 are opened. After completion of the pressure equalization process, the process proceeds to the desorption process.

  Thus, by opening and closing the valves 14 to 19, when one of the adsorption tanks 10 is adsorbed, the other adsorption tank 11 is desorbed, and in the next cycle, one of the adsorption tanks 10 is desorbed and the other is adsorbed. The tank 11 is configured to perform adsorption. These are repeated at a predetermined switching cycle to continuously generate nitrogen gas. The sequencer 26 performs opening / closing control of the valves 14 to 19 and the pressure equalizing valves 20 and 21 for switching the adsorption / desorption process. The product discharge valve 22 is opened by a sequencer 26 after a predetermined time has elapsed after the operation of the apparatus.

  In the PSA-type nitrogen gas supply system 9, the molecular sieve charcoal changes the adsorption rate difference between nitrogen and oxygen depending on the adsorption time. Therefore, if the adsorption / desorption switching cycle of the adsorption tanks 10 and 11 is changed, the generated nitrogen The oxygen concentration of the gas changes (see FIG. 4).

  In the PSA-type nitrogen gas supply system 9, the oxygen concentration of the generated nitrogen gas also changes when the pressure of the pressurized air, that is, the supply amount of the pressurized air, for example, the rotational speed of the compressor 12 changes ( (See FIG. 6).

  The nitrogen gas supply system 9 of the present embodiment is configured to switch the adsorption / desorption cycle of the adsorption tanks 10 and 11, that is, the sequencer 26 for opening and closing the air supply valves 14 and 15, the exhaust valves 16 and 17, and the product supply valves 18 and 19. Further, the controller 25 controls the rotational speed of the compressor 12, that is, the frequency of the inverter 13, so that nitrogen gases having different oxygen concentrations are generated.

  Hereinafter, the case where the set oxygen concentration in the atmosphere in the furnace 1 is 500 ppm will be described as an example.

  The automatic adjustment of the adsorption / desorption switching cycle in the adsorption tanks 10 and 11 by the sequencer 26 will be described based on the flowchart shown in FIG. As shown in FIG. 3, initially, the adsorption / desorption switching period of the adsorption tanks 10 and 11 is set to the time inputted as an initial value to the sequencer 26. The initial value of the switching cycle may be any switching cycle that can generate nitrogen gas having an oxygen concentration lower than the set oxygen concentration of the atmosphere in the furnace 1, but is set so that nitrogen gas having a low oxygen concentration is generated as much as possible. It is preferable to do this. Therefore, it is preferable to set the switching cycle to the shortest time when the oxygen concentration is 0 ppm or close thereto. In this embodiment, 35 seconds (the frequency is 50 Hz and the oxygen concentration is 0 ppm) is set from the test data indicating the relationship between the frequency and switching period and the oxygen concentration shown in FIG.

  Pressurized air that is selectively sent alternately from the compressor 12 to the two adsorption tanks 10 and 11 is repeatedly adsorbed and desorbed at a switching period of 35 seconds, and is produced by adsorption and removal of oxygen. The gas is sent to the product storage tank 23.

  The oxygen concentration in the atmosphere in the furnace 1 is detected by the oxygen concentration meter 24, and the detected value and the set oxygen concentration value (500 ppm) input to the controller 25 are input to the sequencer 26 by serial communication. The sequencer 26 determines that the detected value <(set value + constant value), and if not satisfied, the operation is continued with the switching period of 35 seconds. The constant value may be an arbitrary value, and is set to 300 ppm in the present embodiment.

  By the operation in the switching cycle, the oxygen concentration in the atmosphere inside the furnace 1 is lowered. When the sequencer 26 determines that the detected value <(set value + constant value) is satisfied, the sequencer 26 sets the adsorption / desorption switching cycle of the adsorption tanks 10 and 11 to a switching cycle according to the set oxygen concentration. change. This switching cycle is determined as follows. That is, as shown in FIG. 4, if the inverter frequency (that is, the rotation speed of the compressor 12) is different, the minimum oxygen concentration value of the generated nitrogen gas is different. The frequency decreases as the value of the minimum oxygen concentration increases. Therefore, according to the frequency at which the minimum oxygen concentration of the generated nitrogen gas becomes the set oxygen concentration, the nitrogen gas having the set oxygen concentration can be obtained with the minimum power consumption. Therefore, a switching cycle is selected that can generate nitrogen gas with a set oxygen concentration when the compressor 12 is operated at this frequency. That is, a switching cycle is selected that can generate nitrogen gas having a set oxygen concentration at a frequency at which the minimum oxygen concentration of the generated nitrogen gas becomes the set oxygen concentration. Thereby, the power consumption of the compressor 12 can be minimized.

  Referring to FIGS. 4 and 5, the set oxygen concentration of 500 ppm in the generated nitrogen gas becomes the minimum value of the oxygen concentration when the frequency is 32 Hz. If the compressor 12 is operated at this frequency, nitrogen gas having a set oxygen concentration (500 ppm) can be generated with low power consumption. Therefore, a switching cycle in which the oxygen concentration becomes the set oxygen concentration (500 ppm) under this frequency, that is, 60 seconds is selected. Therefore, when the detected value <(set value + constant value) is satisfied, the adsorption / desorption switching period of the adsorption tanks 10 and 11 is changed to 60 seconds by the sequencer 26, and thereafter the operation is continued at this switching period. Is done.

  As described above, the adsorption / desorption switching period of the adsorption tanks 10 and 11 is initially set to an initial value by the sequencer 26. When the oxygen concentration in the furnace 1 atmosphere approaches the set oxygen concentration, the change is made according to the set oxygen concentration. After that, the operation is changed to this switching cycle.

  On the other hand, the value detected by the oxygen concentration meter 24 and the value of the set oxygen concentration so that the oxygen concentration in the furnace 1 becomes the set oxygen concentration (500 ppm) under the adsorption / desorption switching cycle of the adsorption tanks 10 and 11. The frequency of the inverter 13 is automatically adjusted by the controller 25 in accordance with the deviation from the above, the number of revolutions of the compressor 12 is controlled, the amount of pressurized air fed into the adsorption tanks 10 and 11 is adjusted, and the furnace 1 The oxygen concentration of the nitrogen gas supplied into the inside is automatically adjusted.

  As described above, the adsorption / desorption switching cycle of the adsorption tanks 10 and 11 is appropriately automatically adjusted by the sequencer 26 in accordance with the detected value of the oxygen concentration, and the rotation speed of the compressor 12 is detected for the oxygen concentration. It is controlled by the controller 25 according to the value, and the oxygen concentration of the nitrogen gas supplied into the furnace 1 is automatically adjusted so that the oxygen concentration in the furnace 1 becomes the set oxygen concentration.

  Hereinafter, the operation of the present invention will be described.

  The nitrogen gas atmosphere in the furnace 1 is set to a set oxygen concentration, for example, 500 ppm by the nitrogen gas supply system 9 as described above. The printed circuit board 27 on which the electronic components are mounted is conveyed in the furnace 1 by the conveyor 5 from the substrate carry-in port 1a to the substrate carry-out port 1b, and the cream solder on the printed circuit board 27 is preheated in a heated nitrogen gas atmosphere. 2 is preheated, heated and melted in the reflow chamber 3, the molten solder is cooled and solidified in the cooling chamber 4, and the electronic component is soldered onto the substrate.

  When an oxygen concentration higher than the set oxygen concentration (500 ppm) is detected by the oxygen concentration meter 24, nitrogen gas having a lower oxygen concentration in accordance with the detected value of the oxygen concentration is introduced into the furnace 1 by the nitrogen gas supply system 9. The oxygen concentration in the furnace 1 is always 500 ppm. When an oxygen concentration lower than the set oxygen concentration (500 ppm) is detected by the oxygen concentration meter 24, nitrogen gas whose oxygen concentration is increased according to the detected value of the oxygen concentration is introduced into the furnace 1 by the nitrogen gas supply system 9. The oxygen concentration in the furnace 1 is always 500 ppm. Thus, when the oxygen concentration in the furnace 1 increases / decreases relative to the set oxygen concentration, the oxygen concentration of the nitrogen gas supplied from the nitrogen gas supply system 9 is decreased / increased, and the set oxygen is always set in the furnace 1. It is managed so as to be a concentration.

  The PSA-type nitrogen gas supply system used in the present invention is based on the deviation between the value detected by the oxygen concentration meter and the set oxygen concentration in the furnace, and the adsorption / desorption of the adsorption tank is performed. The oxygen concentration of the nitrogen gas supplied into the furnace is automatically adjusted so that the oxygen concentration in the furnace becomes the set oxygen concentration by adjusting the switching cycle and the supply amount of the source gas. It is also possible to adjust the density as follows. In other words, the oxygen concentration in the furnace is set by adjusting the adsorption / desorption switching cycle of the adsorption tank based on the deviation between the value detected by the oxygen concentration meter and the value of the set oxygen concentration. It can also be configured such that the oxygen concentration of the nitrogen gas supplied into the furnace is automatically adjusted so as to obtain an oxygen concentration. Alternatively, the supply amount of the raw material gas is adjusted based on the deviation between the value of the oxygen concentration detected in the furnace with the oximeter and the value of the set oxygen concentration, so that the oxygen concentration in the furnace becomes the set oxygen concentration. The oxygen concentration of the nitrogen gas supplied into the furnace can be automatically adjusted.

  In the above embodiment, the controller 25 uses a PID control controller, but it may of course be a controller of another control method. Moreover, although the rotation speed of the compressor was controlled, another system may be used as long as the supply amount of the source gas can be controlled. Further, the present invention manages the oxygen concentration in the furnace by the closed loop control as described above, but the oxygen concentration in the furnace is not limited to the closed loop control as in the present invention, but the compressor is operated in accordance with a predetermined procedure. It is also possible to manage by adopting open loop control by sequence control that changes the rotation speed of the suction tank and the adsorption / desorption switching cycle of the adsorption tank.

It is sectional drawing which shows the reflow soldering apparatus of this invention. It is a figure which shows the structural example of the nitrogen gas supply system of a PSA system. It is a flowchart which shows the automatic adjustment of the switching cycle of adsorption | suction / desorption by a sequencer. It is a graph which shows the relationship between a frequency and a switching period, and oxygen concentration. FIG. 5 is an enlarged view of a part of FIG. 4. It is a graph which shows the relationship between the inverter frequency and oxygen concentration under a switching period of 30 seconds.

Explanation of symbols

  1 .. Furnace, 1a ... Substrate carry-in port, 1b ... Substrate carry-out port, 2 .... Preheating chamber, 3 .... Reflow chamber, 4 .... Cooling chamber, 5 .... Conveyor, 6 .... Blower, 7 .... Heater, 8 ·· Nitrogen gas supply pipe, 9 ·· Nitrogen gas supply system, 10, 11 ·· Adsorption tank, 12 ·· Compressor, 13 ·· Inverter, 14,15 ·· Air supply valve, 16, 17 · · Exhaust valve, 18, 19 ·· Product supply valve, 20, 21 · · Pressure equalizing valve, 22 · · Product discharge valve, 23 · · Product storage tank, 24 · · Oxygen meter, 24a · · Detection end, 25 · · Controller, 26 ... Sequencer, 27 ... Printed circuit board with electronic components.

Claims (4)

  In a reflow soldering apparatus that performs reflow soldering in a furnace supplied with nitrogen gas, the oxygen concentration of the nitrogen gas supplied into the furnace is automatically adjusted according to the oxygen concentration in the furnace. A method for managing the atmosphere in the furnace of the reflow soldering apparatus.   In a reflow soldering apparatus that performs reflow soldering in a furnace supplied with nitrogen gas, the nitrogen concentration of the nitrogen gas supplied into the furnace is automatically adjusted according to the oxygen concentration in the furnace. A method for managing the atmosphere in the furnace of the reflow soldering apparatus.   In a reflow soldering apparatus for performing reflow soldering in a furnace supplied with nitrogen gas, nitrogen gas supply means capable of supplying nitrogen gas into the furnace, means for detecting the oxygen concentration in the furnace, and this detection means And a control means for controlling the oxygen concentration of the nitrogen gas supplied from the nitrogen gas supply means in accordance with the oxygen concentration in the furnace detected by the above.   In a reflow soldering apparatus for performing reflow soldering in a furnace supplied with nitrogen gas, nitrogen gas supply means capable of supplying nitrogen gas into the furnace, means for detecting the oxygen concentration in the furnace, and this detection means And a control means for controlling the nitrogen concentration of the nitrogen gas supplied from the nitrogen gas supply means in accordance with the oxygen concentration in the furnace detected by the step.

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