JP2902298B2 - Vapor reflow soldering apparatus and control method therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor reflow soldering apparatus and a control method therefor, and more particularly, to imposition of a so-called flat pack IC, a resistor, a capacitor, etc., in which electrode terminals are taken out in a plane in four directions. Chip parts are printed circuit boards and other wiring boards (hereinafter collectively referred to as circuit boards)
The present invention relates to a vapor reflow soldering apparatus suitable for high-density mounting to be soldered thereon and a control method thereof.

[0002]

2. Description of the Related Art In recent years, high-density mounting of electronic components on a circuit board has been increasingly advanced. However, soldering work for bonding electronic components such as ICs and chip components to a circuit board is a final step of a line. In addition, its soldering technology is regarded as the most important technology in the line. Recently, it is necessary to improve the uniformity of the temperature distribution in the furnace where soldering is performed and to avoid harmful heating of electronic components.
A vapor that uses a vapor with a large specific gravity to air as a heat medium, prints solder on the board, and heats an object to be processed such as a circuit board on which electronic components are mounted by utilizing the latent heat of condensation of the heat medium.
Over reflow soldering apparatus is known.

[0003] This apparatus is disclosed, for example, in JP-A-63-903.
As described in Japanese Patent Publication No. 61, a steam generating tank for soldering a circuit board by passing it through saturated steam of a heat medium having a large specific gravity with respect to air as described above is provided. A conventional typical vapor reflow soldering apparatus using a conveyor will be described with reference to FIGS. FIG. 5 is a longitudinal sectional view showing a configuration of a conventional vapor reflow soldering apparatus, and FIG. 6 is a sectional view of the apparatus shown in FIG.

[0005] The apparatus shown in FIGS.
A reflow section 1 including a carry-in side transport path 5, a carry-out side transport path 6, a heater 7, a carry-in side cooler 8, a carry-out side cooler 9, a carry-in side exhaust port 10, and a carry-out side exhaust port 11;
And a cooling unit 3 having a cooling fan 18.
And a drive system including a conveyor 15, a drive sprocket 19, a drive motor 20, an idler 21, and the like for transporting the workpiece 16 from left to right as viewed in FIG.
A heating medium recovery system including a recovery device 23 provided with the above, a hydroxyl remover 25, a circulation pump 26, and the like; It comprises a temperature control system such as a temperature sensor 31, a temperature controller 32, a power controller 33 and the like.

[0005] The steam generating tank 4 and the chamber having the carry-in side cooler 8 and the carry-out side cooler 9 are separated by an open partition 34 at the lower part, and connected via a return passage 17 formed by a bottom 35 and the partition 34. Have been.

The operation of the conventional vapor reflow soldering apparatus configured as described above will be described. When the apparatus is started, power is supplied to the preheater 14 and the heater 7. The heat medium liquid 12 stored in the lower part of the steam generation tank 4 is
Since the latent heat of evaporation is about 1/25 of water, it is heated by the heater 7 and immediately boiled to generate saturated steam 13. The saturated steam 13 rises in the steam generating tank 4, and a part of the steam 13 flows out of the lower steam outlet 36, and the rest flows out of the upper steam outlet 37 through the side wall passage 38 to remove the solder on the workpiece 16. Ensure the vapor level required for reflow.

[0007] The saturated steam 13 that has heated the object 16 is
It is condensed and liquefied, falls to the lower part of the steam generation tank 4, and accumulates at the bottom of the steam generation tank 4. The remaining saturated steam 13 is cooled and liquefied by the carry-in side cooler 8 and the carry-out side cooler 9, and returns to the bottom of the steam generating tank 4 through the return passage 17. Slightly remaining steam is supplied to the inlet exhaust port 10 and the outlet exhaust port 1.
1 and the vapor that has adhered to the processing object 16 and then evaporates and separates, flows into the recovery device 23 from the discharge-side exhaust port 11 through the pipe 22. Collection device 23
It is recovered by the demister 24 and liquefied cooling steam. The recovered heat medium liquid 12 is subjected to removal of hydroxyl by a hydroxyl remover 25 and returned to the steam generation tank 4 through a return passage 17 by a circulation pump 26.

The workpiece 16 is preheated by a preheater 1 in a preheater 2.
Heated by the radiant heat from the conveyor 4 and carried into the reflow unit 1 by the conveyor 15. Workpiece 1 carried into reflow unit 1
In 6, the solder is heated and melted by the latent heat of condensation of the saturated steam 13. The object 16 is gradually cooled into the unloading-side transport path 6, solidifies the solder, enters the cooling unit 3, is further cooled by the cooling fan 18, and is unloaded from the apparatus. The height of the saturated steam 13 in the steam generation tank 4 is determined by the temperature sensor 31 and the temperature controller 3 movably provided in the steam generation tank 4.
By controlling the power to the heater 7 via the power controller 33 so that the temperature becomes a predetermined temperature according to the above, the predetermined value is maintained.

When the predetermined operation is completed, the heat medium liquid 12 stored in the lower part of the steam generation tank 4 is recovered to the cooling tank 27 by opening the valve 30. Heat medium liquid 12 is used for cooling tank 2
When cooled at 7, the flux that has melted is deposited. Therefore, the heat medium liquid 12 is filtered by the pump 28 into the filter 2.
9 to separate the deposited flux. The heat medium liquid 12 from which the flux has been removed is returned to the return passage 17 on the carry-in side.
And returns to the bottom 35 of the steam generation tank 4.

[0010]

The following problems arise in the vapor reflow soldering apparatus as described above. In the reflow chamber, when power is supplied to the heater 7 by activating the apparatus, the heat medium liquid heated by the heater 7 rises due to the density difference and collects at the upper part of the liquid level. Since the thermal conductivity of the heat medium liquid is as small as about 1/10 of water, heat is not easily transmitted from the heated high-temperature heat medium liquid to the lower-temperature heat medium liquid below.

A stainless steel plate is used as the material in the steam generating tank in consideration of corrosion resistance. The stainless steel sheet has a thermal conductivity as low as half that of the carbon steel sheet, and heat is hardly transmitted to the wall of the steam generation tank. As a result, by the time the heating medium liquid boils (generally 15 to 30 minutes), the temperature difference between the upper wall surface and the lower wall surface of the steam generation tank becomes 100 ° C. or more, and distortion due to thermal stress is generated. Cracks may be generated in the generating tank, and the reliability of the apparatus is reduced, such as leakage of the heat medium liquid.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to reduce a temperature difference between the upper and lower portions of a heat medium liquid stored in a lower portion of a steam generating tank in a reflow section. Another object of the present invention is to provide a highly reliable vapor reflow soldering apparatus and a control method thereof, which reduce a thermal stress caused by a temperature difference between the wall surfaces of a steam generation tank when the apparatus is started.

[0013]

In order to achieve the above-mentioned object, a vapor reflow soldering apparatus according to the present invention comprises a preheating part for mounting an object to be processed by mounting an electronic component on a circuit board coated with solder. And conveyed so as to pass through the reflow section, preheat the object to be processed to a desired temperature by the preheating means in the preheating section, perform the main heating with the saturated vapor of the heat medium liquid in the reflow section to melt the solder, In a vapor reflow soldering apparatus that blows cool air in a cooling unit subsequent to solidify the solder and solder the electronic components onto a circuit board, a heating means for heating a heat medium liquid provided in a steam generation tank of the reflow unit, Heat medium liquid temperature in the steam generation tank and
A temperature sensor for detecting any one of the heat medium vapor temperatures, a heat medium liquid supply means for supplying a heat medium liquid into the steam generation tank, and a heat medium liquid level in the steam generation tank Heat medium liquid amount detection means, heat medium liquid temperature and heat medium vapor
A signal from the temperature sensor when any one of the temperatures reaches the set value and a signal from the heat medium liquid amount detection means control an additional supply amount of the heat medium liquid from the heat medium liquid supply means, and Control means for controlling the supply of the heat source of the heating means.

According to another aspect of the present invention, there is provided a method for controlling a vapor reflow soldering apparatus, comprising the steps of: It is transported so as to pass through the reflow section, and the preheating section preheats the workpiece to a desired temperature,
Vapor reflow soldering in which the main heating is performed with the saturated vapor of the heat medium liquid in the reflow section to melt the solder, and the cooling section following the reflow section blows cool air to solidify the solder and solder the electronic components onto the circuit board. In the control method of the apparatus, at least one heater is provided in the steam generation tank of the reflow section, and the amount of the heat medium to be filled before the apparatus is started is set to an amount in which the heater closest to the bottom is immersed. Energize the submerged heater, heat medium liquid temperature near the bottom of the steam generation tank, surface liquid temperature of the heater,
When one of the heat medium vapor temperatures reaches a set value, a new heat medium liquid is additionally supplied, and the additional supply amount is limited to an amount at which the heat medium liquid temperature does not drop by a certain amount or more. The apparatus is started by repeating the supply of the heat medium liquid each time the set temperature is reached until the heat medium liquid is supplied.

[0015]

The function of the above technical means is as follows. Since the heat conductivity of the heat medium liquid is as small as about 1/10 of water and the heat conductivity of stainless steel is as small as about 1/2 of carbon steel, the present invention minimizes the amount of heat medium liquid when the apparatus is started. The heat transfer between the upper and lower portions of the heat medium liquid is promoted to reduce the temperature difference. Heating is performed by supplying a minimum amount of the heat medium liquid to be charged into the steam generation tank at the time of starting the apparatus so that the upper surface of the heater is immersed in the liquid so as to prevent overheating of the heater (heating means). Shall be. Since the amount of the heating medium liquid is small, the liquid level becomes low, heat transfer between the upper part and the lower part of the liquid is promoted, the temperature difference becomes small, and the temperature becomes uniform.

Further, since the amount of the heat medium liquid is small, it boils in a short time to generate saturated steam. The inside of the steam generation tank is heated by the saturated steam, and the wall surface temperature of the steam generation tank becomes uniform.
When the heating medium liquid boils, the heating medium liquid supply means is driven to supply the remaining liquid in a plurality of times. Supplying the liquid and raising the liquid level are repeated. As described above, the heating is performed by the heater in the limited heat medium liquid. That is, the apparatus is started by supplying a predetermined amount of the heat medium liquid, and the temperature difference on the wall surface of the steam generating tank at the time of starting is reduced to suppress the generation of thermal stress. When the temperature difference on the wall surface of the steam generation tank is reduced, the generation of thermal stress is suppressed, and the secular change such as crack generation hardly occurs, and a highly reliable reflow soldering apparatus can be obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. 1 to 4, the same reference numerals as those shown in FIGS. 5 and 6 denote the same parts, and a general description thereof will be omitted. Embodiment 1 FIG. 1 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to one embodiment of the present invention.

In FIG. 1, reference numeral 31 denotes a steam temperature sensor for detecting the temperature of the saturated steam 13; 39, a temperature sensor for detecting the temperature of the heating medium liquid 12 in the steam generation tank 4;
Is a temperature controller connected to the temperature sensor 39, and 32b is
A temperature controller connected to a steam temperature sensor (temperature sensor) 31; 40, a switch between the temperature controller 32a and the power controller 33; 41, a liquid level gauge provided at a lower portion of the steam generation tank 4; The liquid level gauge 41 functions as a heat medium liquid amount detection unit that detects the liquid level of the heat medium liquid 12 in the steam generation tank 4.

The difference between the embodiment shown in FIG. 1 and the prior art shown in FIGS. 5 and 6 is as follows. That is, the power supply to the heaters 7a and 7b provided in the upper and lower two stages in the steam generating tank 4 is divided into an upper stage and a lower stage, and the heating medium liquid amount detecting means for detecting the liquid level in the steam generating tank is provided. A level gauge 41 is provided. The power supply of the upper heater 7b is controlled by the liquid level meter 41 so that the heater 7b
The power supply is connected to a power supply via a switch 40 that closes a contact when it is detected that the heater is below the surface, and the power supply of the lower heater 7a is always connected to the power supply during operation of the present apparatus. Further, a temperature sensor 39 is provided in the heat medium liquid 12 of the steam generating tank 4, and a temperature control is performed as control means for controlling the operation of the filtering pump 28 based on an electric signal from the temperature sensor 39 and a detection value of the liquid level gauge 41. It has the structure provided with the container 32a.

The operation of the thus configured vapor reflow soldering apparatus of the present embodiment will be described. Prior to the start-up of the device, the heating medium 12 cooled in the cooling tank 27 is used.
Is supplied under pressure to a filter 29 by a filtering pump 28 to remove the flux and supply the same to the steam generation tank 4.
At this time, the supply amount of the heat medium liquid 12 is controlled by controlling the operation of the filtering pump 28 based on the output signal of the liquid level gauge 41, so that the upper surface of the lower heater 7a closest to the bottom of the steam generation tank 4 is almost immersed. Filled to height.

Next, when the apparatus is started, the preheater 14
Then, electric power is supplied to the lower heater 7a. The amount of the heat medium liquid 12 supplied to the bottom 35 of the steam generation tank 4 is
Since the lower heater 7a is slightly small enough to be immersed, it is heated by the heater 7a, heat transfer between the upper and lower portions of the heat medium liquid 12 is promoted, and the temperature difference is reduced. Of saturated steam 13 is generated. The portion below the heat medium liquid level in the steam generation tank 4 is heated to the boiling temperature by the heat medium liquid 12 due to the boiling of the heat medium liquid 12, and the portion in contact with the saturated vapor 13 is heated by the latent heat of condensation of the saturated vapor. The inside of the steam generation tank 4 gradually approaches a uniform temperature (boiling point temperature).

The saturated steam 13 of the heat medium that has heated the inside of the steam generating tank 4 is condensed and liquefied and falls to the bottom 35 of the steam generating tank 4.
Is liquefied by the carry-in side cooler 8, the carry-out side cooler 9, the recovery device 23 and the like, and returns to the bottom 35 of the steam generating tank 4 through the return passage 17. When the saturated steam 13 is generated and the temperature sensor 39 in the heat medium liquid 12 detects that the temperature has become equal to the set temperature (for example, the boiling point temperature), it sends a signal to the temperature controller 32a. Upon receiving a signal from the temperature sensor 39, the temperature controller 32a sends a signal to the filtering pump 28 to operate the filtering pump 28 and cause the heating medium 12
Supply.

At this time, the level of the heat medium liquid is detected by the liquid level meter 41, and when a certain amount of the heat medium liquid is supplied, the temperature controller 3
By sending a signal to 2a and controlling to stop the operation of the filtering pump 28, the remaining heat medium liquid 12 is supplied in a plurality of times. The supply amount of the heat medium liquid 12 by the operation of the filtering pump 28 is:
As described above, the supply is divided into a plurality of times, so that the amount of the heat medium liquid 12 already in the steam generation tank 4 is slightly suppressed at one time, and the amount of the heat medium liquid is suddenly increased by the additional supply of the heat medium liquid. Prevents temperature drop.

Further, the supply of the heat medium liquid 12 to the steam generation tank 4 is performed through the return passage 17, so that the heat medium liquid 12 is mixed with the heat medium liquid 12 recovered while passing through the return passage 17,
The liquid temperature becomes uniform, thereby preventing a local temperature drop and suppressing the occurrence of thermal stress. If it is detected again by the temperature sensor 39 after the supply of the heat medium, the heat medium liquid 12 is repeatedly supplied as described above. When the liquid level meter 41 detects that a predetermined amount of the heat medium liquid 12 immersed in the heat medium liquid 12 has been supplied to the upper heater 7b, the temperature controller 32
a, a switch 40 closes its contact upon receiving a signal from the temperature controller 32a, and switches the upper and lower heaters 7a, 7a.
Heating is performed by b. After this, the heat medium liquid 12 is detected to have exceeded the set temperature by the temperature sensor 3 9,
The supply of the heat medium liquid 12 is repeated, and a predetermined amount of the heat medium liquid 12 required for a normal operation state is supplied, and the apparatus enters a normal start-up state.

In a normal operation state, the lower heater 7a
Always heats, and the upper heater 7b controls the amount of heat generated by the power controller 33 by the steam temperature sensor 31 and the temperature controller 32b to control the height of the saturated steam 13. The subsequent operation of the device is the same as that of the conventional device, and therefore the description is omitted here. By the above-mentioned operation at the time of starting, the steam generation tank 4
Since the temperature difference between the upper and lower portions of the heat medium liquid in the inside can be reduced, the temperature difference on the wall surface of the steam generation tank can be reduced, and the occurrence of thermal stress can be prevented, thereby improving the reliability of the apparatus.

In the above embodiment, the number of temperature measurement points in the heating medium liquid 12 is one, but the number of temperature measurement points may be two or more. For example, if the heat medium liquid 12 is attached at a predetermined interval in the liquid, the temperature difference of the heat medium liquid 12 can be directly confirmed, and the temperature can be controlled more accurately.

Embodiment 2 FIG. 2 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to another embodiment of the present invention. Embodiment shown in FIG. 2, which differ in the embodiment shown in Figure 1, obtained by changing the temperature sensor 3 9 bottom 35 heated from near the heater 7a of the steam generating tank 4, on the surface of 7b, filtering The supply of the heat medium liquid from the pump 28 is performed by the heaters 7a,
The detection is performed by detecting the surface liquid temperature of 7b.

The operation of the apparatus shown in FIG. 2 is the same as the operation of the apparatus of the embodiment shown in FIG. 1, and the description is omitted here. According to this embodiment, the same effects as those of the previous embodiment can be obtained. In particular, since the surface liquid temperature of the heater is directly measured,
This has the effect of preventing overheating of the heaters 7a, 7b.

[Embodiment 3] FIG. 3 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to still another embodiment of the present invention. The embodiment shown in FIG. 3 is different from the embodiment shown in FIG. 1 in that the heating medium liquid is supplied from the filtering pump 28 by the signal of the steam temperature sensor 31 instead of the temperature sensor 39. is there. Further, the filtering pump 28 is provided with an operation time integrating function.

If the relationship between the operating time of the filtering pump 28 and the liquid level is known in advance, the liquid level can be set based on the integrated value of the operating time of the filtering pump 28. For example, the configuration is such that the filtering pump 28 is operated only when the temperature of the steam temperature sensor 31 becomes equal to or higher than a set temperature (boiling point temperature of the heat medium liquid), and is stopped immediately when the temperature becomes equal to or lower than the set temperature. When a predetermined amount of the heating medium liquid 12 supplied in the apparatus during normal operation is supplied based on the integrated value of the operation time of the filtering pump 28, a signal is sent to the temperature controller 32 to immediately stop the filtering pump 28. In this way, the contact of the switch 40 may be closed by the signal to perform a normal operation.

Other general operations of the apparatus shown in FIG. 3 are the same as those of the apparatus of the embodiment shown in FIG. 1, and the description thereof is omitted here. According to this embodiment, the same effects as in the previous embodiment can be obtained, and in particular, the structure is simplified and the reliability is improved.

[Embodiment 4] FIG. 4 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to still another embodiment of the present invention. The embodiment shown in FIG. 4 is different from the embodiment shown in FIG. 1 in that a preheating tank 50 having a built-in preheating heater 51 for preheating the heat medium liquid is provided between the filter 29 and the steam generation tank 4. It is in. The heat medium liquid that has passed through the filter 29 enters the preheating tank 50 and is preheated, and flows into the steam generation tank 4 through the return passage 17.

The embodiment shown in FIG. 4 is different from the embodiment shown in FIGS. 1 to 3 in that the temperature of the heat medium liquid flowing into the steam generation tank approaches the temperature of the heat medium in the steam generation tank. Since the temperature drop due to the liquid supply can be reduced and the temperature difference between the wall surfaces of the steam generation tank can be reduced, there is an effect that generation of thermal stress can be further suppressed. Further, since the heat medium liquid is preheated, the liquid temperature does not decrease even if the supply amount per time is increased, so that there is an effect that the start-up time required until the device enters a normal operation state can be shortened. . Other general operations of the apparatus shown in FIG. 4 are the same as those of the apparatus of the embodiment shown in FIG. 1, and the description is omitted here.

In the above embodiment, when the minimum amount of heat medium boils at the time of starting the apparatus, the apparatus is started up while repeating the operation of additionally supplying a predetermined amount of heat medium and boiling. The additional supply of liquid may be performed continuously. In other words, the supply amount of the heat medium liquid and the calorific value of the heater are balanced within a range where the change amount of the liquid temperature is suppressed to a certain amount or less, and by continuously supplying, the temperature change due to the supply of the heat medium liquid is further reduced. Can be smaller.
In the above-described embodiment, the case where the heaters are provided in two upper and lower stages has been described. However, the number of heaters is a design problem and is not particularly relevant to the essence of the present invention.

[0035]

As described above in detail, according to the present invention, by reducing the temperature difference between the upper and lower portions of the heat transfer fluid stored in the lower portion of the steam generation tank in the reflow section, the steam generation at the time of starting the apparatus is achieved. It is possible to provide a highly reliable vapor reflow soldering apparatus and a control method thereof by reducing thermal stress caused by a temperature difference between the wall surfaces of the bath.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to another embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to still another embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing a configuration of a vapor reflow soldering apparatus according to still another embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing a configuration of a conventional vapor reflow soldering apparatus.

FIG. 6 is a cross-sectional view of the device of FIG.

[Description of Signs] 1 ... reflow section, 2 ... preheating section, 3 ... cooling section, 4 ... steam generating tank, 5 ... incoming side transport path, 6 ... outgoing side transport path, 7a, 7
b: heater, 8: carry-in side cooler, 9: carry-out side cooler, 10: carry-in side exhaust port, 11 ... carry-out side exhaust port, 12 ...
Heat medium liquid, 13: saturated steam, 14: preheater, 15 ...
Conveyor, 16: Workpiece, 17: Return passage, 27: Cooling tank, 28: Filtering pump, 29: Filter, 31: Steam temperature sensor, 32, 32a, 32b: Temperature controller, 33: Power controller, 34 ... partition wall, 35 ... bottom part, 39 ... temperature sensor, 41 ... liquid level gauge, 50 ... preheating tank,
51: Preheating heater.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 3/34 507 B23K 1/015

Claims (3)

(57) [Claims] An object to be processed having electronic components mounted on a circuit board coated with solder is conveyed through a preheating unit and a reflow unit, and the object is heated to a desired temperature by a preheating unit in the preheating unit. Vapor that preheats, performs main heating with the saturated vapor of the heat medium liquid in the reflow section to melt the solder, and blows cool air in the cooling section following the reflow section to solidify the solder and solder the electronic components onto the circuit board in the reflow soldering apparatus, a temperature sensor for detecting the heating means of the heat medium liquid provided to the vapor generation tank reflow section, one of the temperature of the heat medium liquid temperature and the heat medium steam temperature of the steam generating vessel Heating medium liquid supply means for supplying a heat medium liquid into the steam generation tank; heat medium liquid amount detection means for detecting a heat medium liquid level in the steam generation tank; and the heat medium liquid temperature and heat. Medium vapor temperature A heating medium liquid supply amount is controlled from the heating medium liquid supply means by a signal from the temperature sensor and a signal from the heating medium liquid amount detecting means when the temperature of the shift reaches a set value. And a control means for controlling the supply of the heat source. 2. An object to be processed having electronic components mounted on a circuit board coated with solder is conveyed so as to pass through a preheating section and a reflow section. In the preheating section, the object to be processed is heated to a desired temperature by preheating means. Vapor that preheats, performs main heating with the saturated vapor of the heat medium liquid in the reflow section to melt the solder, and blows cool air in the cooling section following the reflow section to solidify the solder and solder the electronic components onto the circuit board In the reflow soldering apparatus, a heating unit for heating a heat medium liquid provided in a steam generation tank of a reflow section, a temperature sensor for detecting any one of a heat medium liquid temperature and a heat medium vapor temperature in the steam generation tank A heat medium liquid supply unit for supplying a heat medium liquid into the steam generation tank, and a signal from a temperature sensor when any one of the heat medium liquid temperature and the heat medium vapor temperature reaches a set value; heat A vapor reflow soldering apparatus, comprising: a control unit that controls a supply amount of a heating medium from the medium liquid supply unit and further controls a supply of a heat source of a heating unit. 3. An object to be processed having electronic components mounted on a circuit board coated with solder is conveyed so as to pass through a preheating section and a reflow section. The preheating section preheats the object to a desired temperature, Vapor reflow soldering in which the main heating is performed with the saturated vapor of the heat medium liquid in the reflow section to melt the solder, and the cooling section following the reflow section blows cool air to solidify the solder and solder the electronic components onto the circuit board. In the control method of the apparatus, at least one heater is provided in the steam generation tank of the reflow unit, and the amount of the heating medium filled before the apparatus is started is set to an amount that the heater closest to the bottom is immersed. Electricity is supplied to the submerged heater, and when one of the heat medium liquid temperature near the bottom of the steam generation tank, the surface liquid temperature of the heater, and the heat medium vapor temperature reaches a set value, a new heat is generated. Medium The liquid is additionally supplied, and the amount of the additional supply is limited to an amount at which the temperature of the heat medium liquid does not drop by a predetermined amount or more, and the supply of the heat medium liquid is performed every time the temperature reaches the set temperature until a predetermined amount of the heat medium liquid is supplied. A method for controlling a vapor reflow soldering apparatus, wherein the apparatus is started by repeating the above steps.