JP4766554B2 - Heating furnace control method and control apparatus - Google Patents

Description

  The present invention relates to a heating furnace control method and control apparatus, and more particularly to a heating furnace control method and control apparatus suitable for heating an object to be heated while maintaining a predetermined temperature.

  Conventionally, a heating furnace for heating an object to be heated by a heated gas is used. As this heating furnace, for example, there is a reflow furnace for soldering surface-mounted components mounted on an electronic substrate. As shown in FIG. 8, the reflow furnace is mounted with a solder paste 4 applied to a plurality of lands (not shown) formed in advance on the wiring board 3 while electrodes are positioned on the lands by a mounter (not shown). This is an apparatus for heating and soldering the placed electronic component 2 in an atmosphere of a predetermined temperature in the reflow furnace 1 for a predetermined time.

  In this reflow furnace 1, a predetermined gas 7 (for example, air, nitrogen gas, etc.) stored in a cylinder 6 through a regulator (pressure regulator) 8 that adjusts the gas flowing in the pipe 9 to a constant pressure is supplied to the reflow furnace 1. It is supposed to be sent. A temperature control unit 10 that heats the gas sent to the reflow furnace 1 is provided at the subsequent stage of the regulator 8. The temperature adjusting unit 10 receives the temperature setting command from the temperature setting unit 11, compares the temperature setting command with temperature information detected by the temperature sensor 12 that detects the temperature in the reflow furnace 1, and the heater 13 The gas heating part 14 which adjusts the temperature of the gas sent into the reflow furnace 1 and adjusts the inside of the reflow furnace 1 to the set temperature is configured.

In addition, there is a reflow furnace configured to send air, nitrogen gas, or the like into the reflow furnace 1 by an air supply device such as a fan (not shown) or a pressurizing device instead of the cylinder 6, but description thereof is omitted.
In such a reflow furnace 1, temperature management in the furnace is important in order to ensure that the electronic component 2 (surface-mounted component) is attached to the wiring board 3 by the melted solder paste 4. Particularly recently, lead-free solder containing no lead has been used from the viewpoint of global environmental protection. This lead-free solder has stricter temperature conditions when soldering the electronic component 2 to the wiring board 3 than the conventional solder of lead and tin alloy. For this reason, the temperature control in the reflow furnace 1 is an extremely important point in improving the manufacturing quality.

  By the way, the wiring board 3 is heated while moving in the reflow furnace 1 by a conveyor (not shown), and the electronic component 2 is soldered. The setting of the moving speed of the conveyor, the temperature in the reflow furnace 1, the area and material of the wiring board 3, the number and type of the electronic parts 2 to be mounted, whether the electronic parts 2 are mounted on one side of the wiring board 3, Alternatively, the temperature in the reflow furnace 1 and the conveyor speed (temperature profile) are set according to the soldering conditions such as the mounting method for mounting on both sides.

Generally, this temperature profile differs depending on the soldering conditions described above. And when the wiring board 3 from which the soldering conditions differ is soldered in the reflow furnace 1, it is necessary to set a temperature profile each time.
Incidentally, the reflow furnace 1 has a large heat capacity in order to maintain the temperature in the furnace, and the temperature adjustment in the furnace for reflowing different wiring boards 3 requires about 10 to 30 minutes. Further, in the conventional reflow furnace 1, when the temperature profile is set and adjusted, the wiring board 3 cannot be put in the furnace. There is a problem that the atmosphere adjustment is necessary every time the type of the wiring board 3 to be soldered is different, and the production efficiency is remarkably lowered.

Therefore, a reflow apparatus and a control method thereof have been proposed to solve this type of problem (see, for example, Patent Document 1).
Incidentally, the temperature profile of the reflow furnace 1 has a preheating process (preheating) prior to soldering as shown in FIG. 9, for example. It is configured as.
JP 2001-160675 A

  However, in the above-described reflow apparatus, in addition to environmental conditions such as atmospheric pressure and temperature in the vicinity of the reflow furnace, when the pressure of the gas sent into the reflow furnace changes, the flow rate of hot air given into the furnace changes. There is a problem of end. In order to solve this kind of problem, it is considered that the pressure of the gas fed into the furnace should be kept constant. However, although this method can keep the volume flow of hot air sent into the furnace constant, the thermal energy applied to the furnace changes due to disturbances such as changes in pressure and temperature near the reflow furnace. There is a concern of deviating from the optimal soldering conditions. For this reason, the conventional reflow furnace has a problem that it is difficult to stably maintain high quality soldering.

Moreover, since the reflow furnace is provided with the preheating process, it cannot be denied that the furnace length becomes long and the installation area of the reflow furnace becomes wide.
The present invention has been made to solve such a problem, and the object of the present invention is to change environmental conditions such as atmospheric pressure and temperature in the vicinity of the heating furnace, the pressure of the gas sent into the furnace, or An object of the present invention is to provide a control method and a control device for a heating furnace with a small installation area, while adjusting the gas sent into the furnace to an optimum temperature and flow rate for processing the object to be heated even if the state of the wiring board changes. .

  For example, a reflow furnace as a heating furnace has heat energy when molecules of gas (for example, air, nitrogen gas, etc.) sent into the furnace are heated by a heater, and this heat energy is transmitted to the solder paste. As a result, the solder paste is melted and the electronic components mounted on the wiring board are soldered. In other words, the main purpose of the reflow furnace is to transfer heat to the object to be heated (solder paste), and to keep the temperature constant, the energy of the gas sent into the furnace is controlled to constant, that is, it is sent into the furnace. It is desirable to control the molecular weight of the gas to be constant.

The control method of the heating furnace of the present invention is made to achieve the above-described object based on such knowledge, and is a control method of a heating furnace that heats an object to be heated by a gas sent into the furnace. And
A flow rate adjusting step for adjusting the flow rate of the gas to a preset mass flow rate, a gas heating step for heating the gas adjusted in the flow rate adjusting step to a preset temperature, the flow rate adjusting step, and the gas And a heating energy adjusting step of adjusting the thermal energy of the gas fed into the furnace to a predetermined value in cooperation with the heating step.

  Preferably, in the energy adjustment step, when the inflow amount of the gas flowing into the heating furnace increases, the gas heating step gives a command to lower the temperature of the gas while the gas flowing into the heating furnace When the inflow amount of the gas decreases, it is desirable to give a command to raise the temperature of the gas to the gas heating step and adjust the thermal energy of the gas sent into the furnace to a predetermined value.

More preferably, when the temperature of the heating furnace rises, the energy adjustment step gives a command to the flow rate adjustment step to reduce the flow rate of the gas, while when the temperature of the heating furnace falls, the flow rate adjustment It is desirable to adjust the thermal energy of the gas sent into the furnace to a predetermined value by giving a command to increase the flow rate of the gas in the process.
The heating furnace control apparatus to which the above-described heating furnace control method is applied is a heating furnace control apparatus that heats an object to be heated by gas fed into the furnace,
A flow rate adjusting unit that is inserted into a pipe into which the gas is fed into the heating furnace and adjusts the flow rate of the gas flowing through the pipe to a preset mass flow rate, and a pipe subsequent to the flow rate adjusting unit. The gas fed into the furnace by cooperating a gas heating unit that heats the gas adjusted by the flow rate adjusting unit to a preset temperature, the flow rate adjusting unit, and the gas heating unit And a thermal energy adjusting unit that adjusts the thermal energy of the battery to a predetermined value.

  The control device for the heating furnace described above adjusts the mass flow rate of the gas (for example, air, nitrogen gas, etc.) sent to the heating furnace to a predetermined value by the flow rate adjustment unit, and the gas heating unit includes, for example, a heater The gas is heated to a preset temperature by, for example. Therefore, the above-described reflow furnace control apparatus heats a gas having a predetermined mass flow rate Q, that is, a predetermined molecular weight, to a preset temperature ΔT (heating temperature−ambient temperature) by a heater. [Q × ΔT] can be kept constant, and an optimum amount of heat is provided for heat-processing the object to be heated.

  Preferably, the thermal energy adjusting unit gives an instruction to lower the temperature of the gas heated by the gas heating unit when the amount of the gas flowing into the heating furnace increases, and flows into the heating furnace. When the inflow amount of the gas decreases, it is desirable to adjust the thermal energy of the gas sent into the furnace to a predetermined value by giving a command to increase the temperature of the gas heated by the gas heating unit. .

  When the flow rate of the gas flowing into the heating furnace changes due to a change in the ambient temperature of the heating furnace or a change in the thermal load of the object to be processed in the furnace, The gas heating unit is commanded to adjust the temperature corresponding to the amount of change, and the thermal energy of the gas is kept constant. Therefore, the above-described heating furnace control device gives thermal energy optimal for heat treatment to the object to be heated in the furnace.

More preferably, when the temperature of the heating furnace rises, the thermal energy adjustment unit gives an instruction to reduce the flow rate of the gas to the flow rate adjustment unit, while when the temperature of the heating furnace falls, the flow rate It is desirable to give a command to increase the gas flow rate to the adjustment unit to adjust the thermal energy of the gas sent into the furnace to a predetermined value.
Even if the temperature of the heating furnace changes due to a change in the ambient temperature of the heating furnace or a change in the thermal load of an object to be processed in the heating furnace, the above-mentioned control device for the heating furnace does not change this temperature. A command is given to the flow controller for the molecular weight of the gas corresponding to the minute, and the thermal energy of the gas is kept constant. Therefore, the above-described heating furnace control device gives thermal energy optimal for heat treatment to an object to be heated to be processed in the furnace.

The heating furnace is configured as a reflow furnace in which a solder paste applied to a previously formed land of a wiring board on which an electronic component is mounted is melted and the electronic component is attached.
The above-mentioned reflow furnace control device is capable of adjusting the temperature change even when the temperature of the reflow furnace changes due to a change in the ambient temperature of the reflow furnace or a change in the thermal load of the wiring board to be soldered in the reflow furnace. In addition to giving a command to the flow controller for the molecular weight of the gas corresponding to the above, the heating amount of the gas heated by the gas heating unit is adjusted to maintain the thermal energy of the gas constant. Therefore, the control device for the reflow furnace described above gives thermal energy optimum for soldering to the solder paste applied on the wiring board in the reflow furnace.

  According to the control method and control device for a heating furnace of the present invention, the flow rate of a gas (for example, air or nitrogen gas) sent into the heating furnace by the flow rate adjusting unit is adjusted to a preset mass flow rate, and this The thermal energy adjustment unit that cooperates with a gas heating unit (for example, a heater) inserted between the flow rate adjustment unit and the heating furnace adjusts the thermal energy of the gas sent into the furnace to a predetermined value. Therefore, the thermal energy of the gas can be kept constant, and the optimum thermal energy can be given to the object to be heated in the heating furnace. Therefore, if the heating furnace control method and control device of the present invention are applied to, for example, a reflow furnace for soldering electronic components mounted on a wiring board, thermal energy suitable for soldering can be applied to the solder paste. High quality soldering can be done.

  The thermal energy adjustment unit gives a command to lower the temperature of the gas adjusted by the gas heating unit when the inflow amount of the gas flowing into the furnace increases, while the inflow amount of the gas flowing into the furnace decreases. Since it is configured to give a command to raise the temperature of the gas, the furnace temperature is changed in the furnace due to a change in the ambient temperature of the heating furnace, a change in the heat load of the object to be heated in the furnace, etc. Even if the flow rate of the flowing gas changes, it is possible to give a command to the gas heating unit so that the temperature corresponds to the flow rate change, and the heat energy of the gas can be kept constant. For this reason, the control method and control apparatus of the heating furnace of the present invention can give optimum heat energy to the object to be heated in the furnace.

  Alternatively, the thermal energy adjustment unit gives a command to decrease the flow rate of the gas adjusted by the flow rate adjustment unit when the temperature in the furnace rises, and gives a command to increase the flow rate when the temperature in the furnace decreases. Even if the temperature in the furnace changes due to a change in the ambient temperature of the heating furnace, a change in the thermal load of the object to be heated in the furnace, etc. Since the gas adjusted to the molecular weight corresponding to the temperature change is fed into the furnace, the thermal energy of the gas can be kept constant. Therefore, the control method and control device for a heating furnace according to the present invention can give optimum thermal energy for soldering to an object to be heated in the furnace, for example, a solder paste applied on a wiring board, and high quality. An excellent effect that soldering is possible can be achieved.

  Hereinafter, as an embodiment of a heating furnace control apparatus to which the heating furnace control method of the present invention is applied, the above-mentioned electronic component is obtained by melting a solder paste applied to a pre-formed land of a wiring board on which the electronic component is mounted. A control apparatus for a reflow furnace to which is attached will be described with reference to the drawings. Also, parts having the same functions as those of the conventional reflow furnace control device shown in FIG. Moreover, FIGS. 1-7 is drawing explaining the control apparatus of the reflow furnace which concerns on 1st embodiment of this invention and its modification, Comprising: These inventions are not limited by these drawings.

  Although the details will be described later, the reflow furnace control device shown in FIG. 1 is different from the conventional reflow furnace control device in that the gas flowing between the regulator 8 and the heater 13 is set via the pipe 9. A fluid flow control device (mass flow controller) 20 which is a flow rate adjusting unit for adjusting the mass flow rate, a flow rate setting unit 21 for giving a command of a mass flow rate of the gas flowing through the mass flow controller 20, and the input in the reflow furnace 1 Set value of the mass flow rate of the gas fed to the furnace and the temperature in the furnace, and the state of the wiring board 3 (the number and type of electronic components 2 mounted on the wiring board 3, the size and material of the wiring board 3, the type of solder paste 4) Etc.) and a control unit (thermal energy adjusting unit) 22 for controlling the temperature in the furnace by causing the mass flow controller 20 and the heater 13 to cooperate with each other. There is a point.

  The mass flow controller 20 includes a mass flow sensor that measures the mass flow rate. For example, as shown in FIG. 10, this mass flow sensor has a pair of temperatures made of a resistance temperature detector in the fluid flow direction F with a heater element Rh made of a heating resistor provided on the silicon base B interposed therebetween. It has an element structure provided with sensors Ru and Rd. The thermal flow meter utilizes the fact that the degree of diffusion (temperature distribution) of the heat generated from the heater element Rh changes due to the flow of the fluid, and the resistance value changes due to the heat of the temperature sensors Ru and Rd. It is configured to detect the flow rate Q of the fluid.

  Specifically, the heat generated from the heater element Rh is applied to the downstream temperature sensor Rd according to the flow rate Q of the fluid, so that the change in the resistance value due to the heat of the temperature sensor Rd is greater than that of the upstream temperature sensor Ru. The flow rate Q is measured by utilizing the fact that it is large. In the figure, Rr is a temperature sensor made of a resistance temperature detector provided at a position away from the heater element Rh, and is used for measuring the ambient temperature.

  FIG. 11 shows a schematic configuration of a thermal flow meter using the above-described mass flow sensor. That is, the drive circuit of the heater element Rh forms a bridge circuit B1 using the heater element Rh, a temperature sensor Rr for measuring ambient temperature, and a pair of fixed resistors R1 and R2, and a voltage supplied from a predetermined power source Vcc is applied to the bridge circuit B1 via the transistor Q, the bridge output voltage of the bridge circuit B1 is obtained by the differential amplifier A1, and the transistor Q is adjusted so that the bridge output voltage becomes zero (0). The heater driving voltage applied to the bridge circuit B1 by feedback control is adjusted. The heater driving circuit configured as described above controls the heat generation temperature of the heater element Rh so as to be always higher than the ambient temperature by a constant temperature difference ΔT.

  On the other hand, the flow rate detection circuit for detecting the flow rate Q of the fluid flowing along the mass flow rate sensor from the change in resistance value due to the heat of the pair of temperature sensors Ru and Rd includes the pair of temperature sensors Ru and Rd and the pair of temperature sensors Ru and Rd. A bridge circuit B2 for measuring a flow rate is formed using the fixed resistors Rx and Ry, and a bridge output voltage (sensor output corresponding to a temperature difference) corresponding to a change in the resistance value of the temperature sensors Ru and Rd is supplied to the differential amplifier A2. Configured to detect via. Then, the flow rate Q of the fluid flowing along the mass flow sensor is obtained from the bridge output voltage detected through the differential amplifier A2 under the condition that the heat generation amount of the heater element Rh is made constant by the heater driving circuit. It has become a thing.

The flow rate Q is calculated, for example, by taking the bridge output voltage (sensor output) into an arithmetic processing unit (CPU) not shown.
In the reflow furnace 1 configured as described above, the wiring placed so that the electrode of the electronic component 2 is positioned by the mounter (not shown) at the position of the solder paste 4 applied to the previously formed land of the wiring board 3. The substrate 3 is fed by a conveyor 15 operating at a predetermined moving speed v [m / s] shown in FIG.

The operation of the control apparatus for the reflow furnace according to the embodiment of the present invention configured as described above will be theoretically described. Here, for the sake of easy understanding, the gas 7 is assumed to be nitrogen gas for convenience.
First, the mass flow controller 20 receives the flow rate command issued from the flow rate setting unit 21 and determines the mass flow rate of the nitrogen gas 7 fed into the reflow furnace 1 (hereinafter sometimes referred to as “furnace”) via the pipe 9. Control to be constant. The mass flow rate of the nitrogen gas fed into the furnace via the mass flow controller 20 is constant, and therefore the molecular weight per unit time of the nitrogen gas 7 flowing through the pipe 9 is constant. That is, the molecular weight per unit time of the nitrogen gas 7 fed into the reflow furnace 1 is constant.

Meanwhile kinetic energy K _E where one molecule at an absolute temperature T [K] has, if the gas constant and R [J / mol · K] ,
K _E = (3/2) R · T [J]
As shown. Thus, the kinetic energy _{K n} having the nitrogen gas n [mol] of the absolute temperature T [K], if the Avogadro's number and _{N A} [mol ^-1],
K _n = (3/2) n · NA _A · R · T [J]
It is obtained. Now, assuming that the volume of the nitrogen gas 7 fed from the mass flow controller 20 into the furnace is V [m ³ ], the number of moles N of the nitrogen gas 7 is
N = V / (22.4 × 10 ⁻³ ) [mol]
It is. Therefore, if the flow rate per unit time is q [m ³ / s], the number of moles n of nitrogen gas 7 fed into the furnace per second by this gas is:
n = q / (22.4 × 10 ⁻³ ) [mol / s]
It becomes. Therefore, when the nitrogen gas 7 is T [K], the heat flow I flowing into the reflow furnace 1 is
I = (3/2) · q / (22.4 × 10 ⁻³ ) NA _A · R · T [J / s]
= (3/2) · q / (22.4 × 10 ⁻³ ) NA _A · R · T [W]
= K ・ q ・ T [W]
It is obtained. However, K = 3N _A · R / (2 × 22.4 × 10 ⁻³ ).

As this equation shows, it can be derived that the heat flow I given to the reflow furnace 1 is proportional to the product of the gas flow rate and the absolute temperature of the gas.
In order to simplify the analysis here, the heat transfer coefficient α [W / (m ² · K)] of the board including all objects including the electronic component 2 and the solder paste 4 mounted on the wiring board 3 is assumed. If the surface area of contact of the substrate surface with the nitrogen gas 7 is S [m ² ], the surface thermal resistance R _S of the substrate is
R _S = 1 / αS [K / W]
It is. On the other hand, the heat capacity of the reflow furnace 1 is C [J / K], the heat capacity of the substrate is extremely small compared to the heat capacity of the reflow furnace 1, and this is ignored and the heat flow dissipated from the reflow furnace 1 to the outside is ignored. if simplification, and the heat capacity C and the surface thermal resistance R _s as shown in FIG. 3 are connected in parallel, the equivalent circuit is obtained for supplying the heat flow I in the parallel circuit.

As described above, the heat flow I is hot air obtained by heating the nitrogen gas 7 having a constant mass flow rate, that is, a constant molecular weight per unit time, by the heater 13 with the mass flow controller 20. This heat flow I is divided into the heat capacity C and the surface heat resistance R _s as a heat flow I _C and a heat flow I _R , respectively. Incidentally, in general, the reflow furnace 1 is designed to have a large heat capacity C in order to suppress temperature fluctuation in the furnace. Therefore, heat flow I _C, when the furnace has reached a certain temperature may be considered to hardly flows. Of course, the heat flow that leaks from the heat capacity C, that heat dissipated out of the furnace is considered as being slightly, this case can be considered as a constant heat flow I _C flows.

On the other hand, the surface thermal resistance _RS is the heat transfer coefficient α [W / (m ² · K) of the board including all the objects including the electronic component 2 and the solder paste 4 mounted on the wiring board 3 as described above. ] And the contact surface area S [m ² ] in contact with the surface area of the substrate (nitrogen gas 7) changes as a matter of course. Therefore, if the flow rate and temperature of the nitrogen gas 7 fed into the furnace are adjusted so as to obtain an optimum heat flow I according to the surface thermal resistance R _S for each different board, the solder paste applied to the land of the wiring board 3 is melted. Thus, the electronic component 2 can be soldered with high quality.

  Specifically, evaluation is performed by performing soldering in advance in the reflow furnace 1 so that optimum soldering conditions can be maintained for each of the plurality of types of substrates to be soldered, and the flow rate conditions set in the flow rate setting unit 21 and The temperature conditions set in the temperature setting unit 11 are recorded, and the optimum conditions corresponding to the state of the wiring board are set in the control unit 22. By doing so, even if a plurality of types of substrates are sent to the reflow furnace 1 by the conveyor 15, the flow rate and temperature of the gas are adjusted by the control unit 22 so that the heat flow is optimal for the substrates flowing in the reflow furnace 1. As a result, high quality soldering is possible.

More specifically, with respect to the reflow furnace control device according to the embodiment of the present invention, the wiring board 3 (all objects including the electronic component 2 and the solder paste 4 mounted on the wiring board 3) with respect to the moving speed v of the conveyor 15 including) will be described by using the necessary quantity of heat Q to request a reflow furnace 1, the graph of FIG. 4 showing a relationship between a supply heat quantity Q _W capable reflow furnace 1 has on the wiring board 3.

  The wiring board 3 has a shorter time in the reflow furnace 1 as the moving speed of the conveyor 15 increases. For this reason, the amount of heat required for the movement speed is increased. On the other hand, the amount of heat supplied to the wiring board 3 decreases in inverse proportion to the moving speed v of the conveyor 15 if the heat flow I supplied into the reflow furnace 1 is constant. From this, the graph shown in FIG. 4 is obtained.

An amount of heat Q _A required by the wiring board 3 from the figure, if the moving speed of the conveyor 15 is v, supplied heat quantity Q _W1 supplies the reflow furnace 1 to the wiring board 3 shows this Q _A It can be derived that it may be set so as to pass through the intersection S between the straight line and the moving speed v. That is, this intersection point S is a point where the amount of heat required for the wiring board 3 to perform soldering and the amount of heat supplied to the reflow furnace 1 are equally balanced, and optimal soldering can be performed.

If you introduce another wiring board 3 while a constant movement speed v of the conveyor 15 to the reflow furnace 1, if the amount of heat that the wiring board 3 requires increases to Q _B, shows the Q _B line and may be adjusted to supply heat to be supplied to the reflow furnace 1 is wiring board 3 increases the amount of heat supplied so as to pass through the intersection point T between the moving velocity v in the Q _W2.
In addition, although control of the reflow furnace 1 mentioned above illustrated the case where the moving speed v of the conveyor 15 was made constant, for example, the same wiring board 3 (the electronic component 2 mounted on the wiring board 3 and the solder paste 4 are included. The present invention can also be applied to a case where the moving speed v of the conveyor 15 is increased in order to increase the number of manufactured sheets (including all objects). For example, the amount of heat the wiring board 3 requests as shown in FIG. 5 indicated by Q, the movement speed of the conveyor 15 as v ₁ when operating the reflow furnace 1, the moving speed v ₁ of the straight line Q and the conveyor 15 The amount of heat (heat flow) supplied to the reflow furnace 1 so as to pass through the intersection S is adjusted to _QW1 . When the speed of the conveyor 15 is increased to the moving speed v ₂ , the amount of heat Q required by the wiring board 3 increases, so that the reflow is performed so as to pass through the intersection T between the straight line Q and the moving speed v ₂ of the conveyor 15. the amount of heat (heat flow) is supplied to the furnace 1 may be adjusted to Q _W2. Of course, when the number of manufactured sheets per unit time is reduced, the amount of heat (heat flow) supplied to the reflow furnace 1 may be reduced by applying a concept opposite to that described above.

Alternatively, the amount of heat (heat flow) supplied to the reflow furnace 1 is constant, and different wiring boards 3 (including all objects including the electronic component 2 and the solder paste 4 mounted on the wiring board 3) are used in the reflow furnace 1. What is necessary is just to adjust the moving speed v of the conveyor 15, when soldering. Specifically, as shown in the graph of FIG. 6, when the amount of heat Q supplied to the reflow furnace 1 is constant and the amount of heat required by the wiring board 3 is Q _A , the amount of heat supplied Q _W supplied to the reflow furnace 1 an intersection U of the required heat quantity Q _a of the wiring board 3 and find, may be set as the moving speed v ₁ of the conveyor 15. Then, if different heat wiring board 3 requires is Q _B, find the intersection V of the heat supplied Q _W supplied to the reflow furnace 1 requires heat Q _B of the wiring board 3, the movement of the conveyor 15 The speed v ₃ may be used.

As described above, the heating furnace control method and control apparatus according to the present invention use the parameters of the thermal energy K _E required for heat-treating the article 1 to be heated, the flow rate Q of the gas 7 and the heating temperature ΔT (treatment temperature-ambient temperature) as parameters. Is controlled by the control unit 22 (thermal energy adjustment unit) so as to satisfy [K _E = Q × ΔT]. That is, if any two of these three parameters are determined, the remaining parameters are uniquely determined. Therefore, the control part 22 can supply the optimal amount of heat to heat the object to be heated 1 by performing this calculation.

  Thus, in the heating furnace control apparatus to which the heating furnace control method of the present invention is applied, the flow rate of the gas (for example, air or nitrogen gas) 9 sent to the reflow furnace 1 by the mass flow controller 20 (flow rate adjusting unit) is preset. In addition to adjusting the mass flow rate, the heater 13 (gas heating unit) inserted between the mass flow controller 20 and the reflow furnace 1 cooperates to heat and control the gas to a preset temperature. Since the control unit 22 (thermal energy adjusting unit) is provided, the thermal energy of the gas can be kept constant, and the heat most suitable for soldering the solder paste applied on the wiring board in the reflow furnace 1 Can give energy. Therefore, the heating furnace control apparatus to which the heating furnace control method of the present invention is applied can perform high-quality soldering.

  Next, a modification of the control device for the reflow furnace according to the embodiment of the present invention will be described with reference to the drawing shown in FIG. In this modified example, the flow rate follow-up control for controlling the heating temperature of the heater 13 according to the variation in the constant mass flow control controlled by the mass flow controller 20 and the mass flow controller according to the variation in the constant temperature control controlled by the temperature adjustment unit 10. A reflow furnace control apparatus having a temperature follow-up control that adjusts a flow rate control amount of 20 is provided with the same reference numerals for parts having the same functions as those of the above-described embodiment, and the description thereof is omitted.

  The mass flow controller 20 includes a movable valve 20a that adjusts the flow rate of the gas 7 that flows through the pipe 9, a mass flow rate detection unit 20b that detects the mass flow rate of the gas 7 that flows through the movable valve 20a, and outputs mass flow information. The comparison unit 20c that compares the flow rate command issued from the setting unit 21 with the mass flow rate information detected by the mass flow rate detection unit 20b and outputs the deviation information, and receives the deviation information obtained by the comparison unit 20c and receives the deviation information. The valve opening 20 is adjusted, and the valve 7 is configured to adjust the mass flow rate of the gas 7 to the flow rate given from the flow rate setting unit 21.

  On the other hand, the temperature controller 30 heats the gas 7 flowing through the pipe 9 to keep the temperature in the reflow furnace 1 constant, and the temperature of the hot air heated by the heater 13 and sent into the reflow furnace 1. The temperature detection unit (temperature sensor) 12 to be detected, the temperature designation output from the temperature setting unit 11 and the temperature of the hot air detected by the temperature detection unit 12 are compared, and the comparison unit 31 that outputs the deviation information and this comparison The heater adjustment unit (temperature adjustment unit) 10 is provided that receives the deviation information obtained by the unit 31 and adjusts the value of the current supplied to the heater 13 to adjust the temperature of the gas 7 to the temperature given from the temperature setting unit 11. Configured.

  The mass flow rate information detected by the mass flow rate detection unit 20 b of the mass flow controller 20 is given to the flow rate tracking control unit 40. The flow rate tracking control unit 40 includes a comparison unit 41 that compares the flow rate setting value that the control unit 22 gives to the flow rate setting unit 21. The comparison unit 41 obtains and outputs a value (flow rate difference value) obtained by subtracting the mass flow rate information detected by the mass flow rate detection unit 20b from the flow rate setting value given to the flow rate setting unit 21 by the control unit 22. The flow rate difference value output from the comparison unit 41 obtains a temperature change in the vicinity of the set temperature with respect to the amplified flow rate difference value (flow rate change amount) via a gain adjustment unit 42 that amplifies the output to a predetermined gain and outputs the gain. It is given to the differentiation circuit (dT / dQ) 43. The output of the differentiating circuit 43 is added to the temperature command value given to the temperature setting unit 11 by the control unit 22 and the addition unit 44 and is given to the temperature setting unit 11.

  With this configuration, even if the mass flow rate of the gas 7 varies due to some factor, the flow rate tracking control unit 40 adjusts the temperature of the heater 13 so as to suppress the variation. Specifically, when the inflow amount of the gas 7 flowing into the reflow furnace 1 increases, the flow rate tracking control unit 40 outputs a command to lower the temperature of the gas 7 adjusted by the heater 13 while the reflow furnace 1 When the inflow amount of the inflowing gas 7 decreases, a command to increase the temperature of the gas 7 adjusted by the heater 13 is output. Therefore, even if the flow rate of the gas 7 flowing into the reflow furnace 1 changes due to a change in the ambient temperature of the reflow furnace 1 or a change in the thermal load of the wiring board 3 to be soldered in the reflow furnace 1, the flow following control is performed. Since the unit 40 corrects the temperature corresponding to the change in the flow rate and gives it to the temperature setting unit 11, the thermal energy of the gas 7 can be kept constant. For this reason, the heating furnace control method and control apparatus according to the present invention can give thermal energy optimum for soldering to the solder paste applied on the wiring board 3 in the reflow furnace 1.

  On the other hand, the temperature information in the furnace detected by the temperature detection unit 12 of the temperature controller 30 is given to the temperature tracking control unit 50. The temperature tracking control unit 50 includes a comparison unit 51 that compares the temperature setting value that the control unit 22 gives to the temperature setting unit 11. The comparison unit 51 obtains and outputs a value (temperature difference value) obtained by subtracting the temperature information detected by the temperature detection unit 12 from the temperature setting value given to the temperature setting unit 11 by the control unit 22. The temperature difference value output from the comparison unit 51 obtains a flow rate change in the vicinity of the set flow rate with respect to the amplified temperature difference value (temperature change amount) via a gain adjustment unit 52 that amplifies the output to a predetermined gain and outputs it. It is given to the differentiation circuit (dQ / dT) 53. The output of the differentiation circuit 53 is added to a flow rate command value given to the flow rate setting unit 21 by the control unit 22 and added to the addition unit 54 to be output to the flow rate setting unit 21.

  By configuring in this way, even if the temperature of the gas 7 controlled and output by the temperature controller 30 fluctuates due to some factor, the temperature follow-up control unit 50 suppresses the fluctuation and the mass flow rate of the gas 7 Adjust. Specifically, the control method and control device for a heating furnace according to the present invention provides a command to reduce the flow rate of the gas 7 adjusted by the mass flow controller (flow rate controller) 20 when the temperature of the reflow furnace 1 rises, When the temperature of the furnace 1 decreases, a command to increase the flow rate of the gas 7 is given. For this reason, even if the temperature of the reflow furnace 1 changes due to a change in the ambient temperature of the reflow furnace 1 or a change in the thermal load of the wiring board 3 to be soldered in the reflow furnace 1, the thermal energy of the gas is constant. Can be maintained.

Therefore, the control method and control device for the heating furnace of the present invention can give the thermal energy optimum for soldering to the solder paste 4 applied on the wiring board 3 in the reflow furnace 1, and high quality soldering can be achieved. It becomes possible.
Next, a second embodiment of the heating furnace control apparatus to which the heating furnace control method of the present invention is applied will be described. The second embodiment is different from the above-described embodiment in that the wiring board 3 placed so that the electrode of the electronic component 2 is located by the mounter is placed in the reflow furnace 1 without using a conveyor. This is a soldering process, and it is a control device for a heating furnace suitable for the production of a small variety of products.

  As described above, in order to solder the electronic component 2 placed on the wiring board 3, a preheating step (preheating) as shown in FIG. 9 is necessary. Accordingly, in the heating furnace to which the heating furnace control device of the present invention is applied, the flow rate and temperature of the gas fed into the reflow furnace 1 are controlled by the control unit 22 so as to match the temperature profile, so that the temperature suitable for soldering. You can run a profile. Therefore, the heating furnace to which the control device for the heating furnace of the present invention is applied eliminates the time required for resetting the temperature profile when soldering a small number of various types of wiring boards 3, and also a heating furnace for preheating. Is unnecessary, and there is a great effect that the installation area can be reduced.

  In addition, the control method and control apparatus of the heating furnace of the present invention are not limited to the above-described embodiment, and can be applied to a heating furnace that heats an object to be heated by gas fed into the furnace, Of course, various modifications can be made without departing from the scope of the present invention.

The schematic block diagram which shows the whole structure of the control apparatus of the reflow furnace which concerns on one Embodiment of this invention. The figure which represented typically the wiring board conveyed with the conveyor to the reflow furnace shown in FIG. The equivalent circuit which shows the thermal circuit of the reflow furnace shown in FIG. The graph which shows the relationship between the required heat amount which a wiring board requires with respect to the conveyance speed of a conveyor, and the supply heat amount which a reflow furnace can supply to a wiring board as an example. The graph which shows the relationship of the heat supply amount which a reflow furnace should supply to a wiring board as an example, when the conveyance speed of a conveyor is changed. The graph which shows the relationship of the moving speed of the conveyor which should be set as an example, when the state (surface thermal resistance) of a wiring board is changed. The schematic block diagram which shows the whole structure of the control apparatus of the reflow furnace which concerns on embodiment which deform | transformed the reflow furnace shown in FIG. The schematic block diagram which shows the whole structure of the control apparatus of the conventional reflow furnace. The figure which shows an example of the temperature profile in a reflow furnace. The schematic block diagram of a mass flow sensor. The figure which shows the structural example of the heater drive circuit and flow detection circuit which are applied to the mass flow sensor of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflow furnace 2 Electronic component 3 Wiring board 4 Paste 6 Cylinder 7 Gas 8 Regulator 9 Piping 10 Temperature control part 11 Temperature setting part 12 Temperature detection part 13 Heater 20 Mass flow controller 21 Flow rate setting part 22 Control part 30 Temperature controller

Claims (7)

A method for controlling a heating furnace that heats an object to be heated by gas fed into the furnace,
A flow rate adjusting step for adjusting the flow rate of the gas to a preset mass flow rate;
A gas heating step of heating the gas adjusted in the flow rate adjustment step to a preset temperature;
A heating energy adjusting step of adjusting the thermal energy of the gas fed into the furnace to a predetermined value by cooperating the flow rate adjusting step and the gas heating step. Control method.   In the energy adjustment step, when the inflow amount of the gas flowing into the heating furnace increases, the gas heating step gives a command to lower the temperature of the gas, while the inflow amount of the gas flowing into the heating furnace. 2. The heating according to claim 1, wherein when the gas is reduced, the gas heating step is given a command to increase the temperature of the gas to adjust the thermal energy of the gas fed into the furnace to a predetermined value. How to control the furnace.   When the temperature of the heating furnace rises, the energy adjustment process gives an instruction to reduce the flow rate of the gas to the flow rate adjustment process, while when the temperature of the heating furnace falls, the gas is supplied to the flow rate adjustment process. The heating furnace control method according to claim 1, wherein a heat energy of the gas fed into the furnace is adjusted to a predetermined value by giving a command to increase the flow rate of the furnace. A control device for a heating furnace that heats an object to be heated by gas sent into the furnace,
A flow rate adjusting unit that is inserted into a pipe through which the gas is fed into the heating furnace and adjusts the flow rate of the gas flowing through the pipe to a preset mass flow rate;
A gas heating unit that is provided in a downstream pipe of the flow rate adjustment unit and heats the gas adjusted by the flow rate adjustment unit to a preset temperature;
A heating furnace comprising: a heat energy adjusting unit that adjusts the thermal energy of the gas fed into the furnace to a predetermined value by cooperating the flow rate adjusting unit and the gas heating unit. Control device.   The thermal energy adjusting unit gives a command to lower the temperature of the gas heated by the gas heating unit when the amount of the gas flowing into the heating furnace increases, while the gas flowing into the heating furnace The gas energy supplied to the furnace is adjusted to a predetermined value by giving a command to raise the temperature of the gas heated by the gas heating unit when the inflow amount of the gas decreases. 4. A control apparatus for a heating furnace according to 4.   When the temperature of the heating furnace rises, the thermal energy adjustment unit gives an instruction to reduce the flow rate of the gas to the flow rate adjustment unit, while when the temperature of the heating furnace decreases, the flow rate adjustment unit The control apparatus of the heating furnace of Claim 4 which gives the instruction | command which increases the flow volume of gas, and adjusts the thermal energy which the said gas sent into the said furnace has to a predetermined value.   The heating furnace according to any one of claims 4 to 6, wherein the heating furnace is a reflow furnace in which a solder paste applied to a pre-formed land of a wiring board on which an electronic component is mounted is melted and the electronic component is attached. Control device.

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