JP3934281B2 - Conveyor furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conveyor furnace which is used in a soldering process of an electric circuit board and a screen printing electrode forming process of a solar battery or a liquid crystal panel paste, and dries or fires wet solder or paste on the board.
[0002]
[Prior art]
A conventional conveyor furnace 100 will be described with reference to FIG. In the figure, 101 is a chamber, 102 is a heat insulating material provided on the outer surface of the chamber 101, 103 is a cabinet that houses the chamber 101, 104 is a lamp heater installed in the chamber 101, 105 is a heat exhaust port in the cabinet, 106 Is a thermocouple, 107 is a temperature control unit, 108 is a substrate to which a paste is attached, and 109 and 110 are substrate entrances. Reference numeral 111 denotes an outside air intake port to the cabinet 105, 112 denotes a belt for transporting the substrate, 113 and 114 denote belt driving rollers, 115 denotes a belt tension roller, 116 denotes an air supply unit, 117 and 118 denote air curtains, and 119 and 120 Is an exhaust duct, 121 is an exhaust gas in the cabinet, and 122 is an exhaust gas in the chamber.
[0003]
The belt 112 that conveys the substrate 108 is driven by belt driving rollers 113 and 114 disposed on both sides of the cabinet 103. Further, since the belt driving roller 114 alone rotates idly, the driving force of the belt driving roller 114 is reliably transmitted to the belt 112 by the tension of the belt tension roller 115. The belt 112 has a loop shape, and is introduced into the chamber 101 again through the outside of the cabinet 103.
[0004]
Next, the operation will be described. The substrate 108 fixed on the belt 112 is successively put into the chamber 101 and heated and dried by the lamp heater 104. The temperature in the chamber 101 that has risen due to the lighting of the lamp heater 104 is measured by the thermocouple 106, and the measurement data is given to the temperature control unit 107. Based on the measurement data, the temperature control unit 107 controls the output of the lamp heater 104 so that the temperature in the chamber 101 becomes constant.
[0005]
In order to exhaust the organic solvent gas generated from the paste adhered to the substrate 108, fresh air is continuously supplied from the air supply unit 116, and the in-chamber exhaust gas 122 is exhausted from the exhaust ducts 119 and 120. In order to keep the airflow and temperature in the chamber 101 constant, air curtains 117 and 118 are provided in the vicinity of the substrate entrances 109 and 110. Moreover, in order to prevent the temperature rise of the conveyor furnace 100 and to operate safely, a cabinet 103 is provided so as to surround the chamber 101 and its heat insulating material 102, and outside air is taken in from the outside air intake port 111, and warm outside air is It is discharged from the cabinet exhaust port 105.
[Problems to be solved by the invention]
[0006]
The lamp heater 104 quickly warms the air in the substrate 108, the belt 112, and the air supply unit 116 in the chamber 101 to the temperature in the chamber. However, the heat of the lamp heater 104 is difficult to be transmitted near the substrate entrances 109 and 110, and the substrate entrance 109 , 110 is considerably lower than the temperature inside the chamber 104. As a result, as shown in FIG. 6, condensation A of the organic solvent gas is generated near the substrate inlet / outlet 110, and this condensation A may drop on the substrate 108 to cause a pattern defect (in the vicinity of the substrate inlet / outlet 110). The same applies to.
[0007]
An example of this situation is discussed below. Assuming that the adhered paste on the substrate 108 contains 20% of texanol having a boiling point of 230 ° C., the chamber 101 is maintained at 160 ° C., and the substrate 108 with 10 g of the paste is continuously fed every 5 seconds. In the chamber 101, it is calculated that steam at 160 ° C. containing 0.4 g of texanol per second is generated. Here, when 150 liters of air is supplied from the air supply unit 116 per minute, the dew point temperature of texanol is estimated to be 110 ° C. In contrast, the air curtains 117 and 118 supplied at 20 liters per minute at room temperature and the temperatures of the substrate entrances 109 and 110 are only about 50 ° C. to 120 ° C. As a result, the temperature in the vicinity of the substrate entrances 109 and 110 becomes equal to or lower than the dew point temperature of texanol, and condensation A of the organic solvent gas is generated.
[0008]
On the other hand, if there are gaps between the chamber 101 and the heat insulating material 102 and the cabinet 103 at the substrate entrances 109 and 110, the exhaust gas 121 in the cabinet becomes an exhaust gas mixed with organic exhaust. Further, if the exhaust gas 122 in the chamber is exhausted as it is, the environment is contaminated, which is a problem.
Here, the printing paste-containing organic solvent has been described, but in the case of the soldering process, the exhaust gas may contain an acidic inorganic substance, which is a problem in terms of safety and health.
[0009]
As described above, in the conventional conveyor furnace 100, there is a problem that the solvent gas generated at the substrate entrances 109 and 110 is dripped onto the substrate 108 and the apparatus due to condensation A, and environmental pollution due to the solvent gas is a problem.
An object of the present invention is to provide a conveyor furnace which solves such problems and hardly causes condensation of solvent gas. It is another object of the present invention to provide a conveyor furnace that hardly causes environmental pollution due to solvent gas.
[0010]
[Means for Solving the Problems]
The conveyor furnace according to claim 1 is provided at a substrate entrance / exit of the chamber in a conveyor furnace that allows a substrate to pass through a chamber provided with heating / drying means to dry or bake deposits adhered on the substrate. The air curtain includes an air curtain, an air heating unit that heats air of the air curtain, and an air duct outside the air curtain that is provided outside the air curtain and exhausts gas leaked from the air curtain. The air is heated so that the temperature of the air is higher than the dew point of the solvent gas generated from the deposit, and the exhaust gas in the chamber exhausts the solvent gas generated from the deposit, and the solvent gas discharged from the exhaust duct in the chamber A liquid reservoir that liquefies and collects, a solvent recovery portion that recovers the liquid solvent collected in the liquid reservoir, and a chamber substrate A substrate inlet / outlet heating unit that is provided at the inlet and heats the substrate inlet / outlet of the chamber, and the substrate inlet / outlet heating unit heats the substrate inlet / outlet of the chamber to a temperature higher than a dew point of the solvent gas generated from the deposit, It is further provided with the solvent absorption part provided near board | substrate entrance / exit of this, and absorbing the solvent gas generated from the said deposit | attachment .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a conveyor furnace according to the invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a conveyor furnace 1 according to the present embodiment. In the figure, 2 is a chamber provided with substrate entrances 3 and 4 on both sides, 5 is a heat insulating material provided on the outer surface of the chamber 2, 6 is a cabinet that accommodates the chamber 2, and 7 and 8 are sides of the cabinet 6. A belt driving roller 9 is a loop belt which is supported at both ends by belt driving rollers 7 and 8 and is introduced into the chamber 2 through the substrate entrances 3 and 4.
[0020]
Further, 10 is a substrate placed on the belt at a predetermined interval, and a paste as an example of a deposit is adhered thereto, 11 is a lamp heater (heating / drying means) disposed above the belt 10 in the chamber 2, Reference numeral 12 denotes an air supply unit installed below the belt 10 in the chamber 2, 13 denotes a cabinet internal heat exhaust port formed in the upper part of the cabinet 6, and 14 denotes an outside air intake port formed in the lower part of the cabinet 6. The deposit is not limited to a paste, and may be a metal such as solder.
[0021]
Further, 15 is a thermocouple for measuring the temperature in the chamber 2, and 16 is a temperature control unit for controlling the temperature in the chamber 2 based on the temperature data measured by the thermocouple 15. Here, the temperature control unit 16 is connected to the lamp heater 11 via a cable (the cable is not shown), and the output of the lamp heater 11 is adjusted by the control of the temperature control unit 16.
[0022]
Reference numeral 17 denotes a belt tension roller for applying tension to the belt 9, 18 and 19 an air curtain provided at the substrate entrance, 20 an air heating unit for heating the air of the air curtain 19, and 21 a substrate entrance 3 of the chamber 2. 4 is a heat insulating material (sealing portion) provided between the chamber 2 and the cabinet 6 in the vicinity of 4 and filling the gap between the chamber 2 and the cabinet 6.
[0023]
Furthermore, 22 is provided in the substrate inlet / outlet 4, and a rubber heater (substrate inlet / outlet heating unit) for heating the solvent gas leaking from the substrate inlet / outlet 4, and 23 is provided on the outer surface of the rubber heater 22 to absorb the solvent gas generated from the paste. Solvent absorption heat insulating material (solvent absorption part), 24 is exhaust gas in the cabinet, 25 is exhaust gas in the chamber, 30 is provided on both sides of the cabinet 6, and exhausts the solvent gas generated from the paste adhered to the substrate 10 Exhaust unit.
[0024]
As shown in FIG. 2, the exhaust unit 30 is provided outside the air curtain 19, extends between the chamber 2 and the cabinet 6, and extends outside the cabinet 6. An in-chamber exhaust duct 32 for exhausting the solvent gas in the chamber 2 and a box-shaped organic solvent trap (liquid reservoir) connected to the exhaust ducts 31 and 32 for liquefying and collecting the solvent gas. 33).
[0025]
The exhaust unit 30 is formed on the upper surface of the organic solvent trap 33, and discharges heat from the organic solvent trap 33 and a drain valve (solvent for recovering the liquid organic solvent accumulated in the organic solvent trap 33. A recovery part) 35 and an exhaust duct 36 extending upward from the upper surface of the organic solvent trap 33 and exhausting the exhaust gas in the organic solvent trap 33.
[0026]
As shown in FIG. 3, the air curtain 18 and the air heating unit 20 are integrally formed, and a fan 18b is provided below the air outlet 18a. The air heating unit 20 is provided with a coil heater 20a and a thermocouple 20b, and the coil heater 20a is feedback-controlled based on temperature data measured by the thermocouple 20b.
[0027]
Furthermore, as shown in FIG. 4, the rubber heater 22 includes a rectangular Si rubber sheet 22a and a heater wire incorporated in the Si rubber sheet 22a. Then, by supplying electricity to the heater wire to heat the heater wire, the Si rubber sheet 22a is warmed, and the occurrence of condensation near the substrate entrance / exit 4 is prevented.
[0028]
Next, the operation will be described. The substrates 10 fixed on the belt 9 are successively put into the chamber 2 and heated and dried by the lamp heater 11. The belt 9 is driven by belt drive rollers 7 and 8 disposed on both sides of the cabinet 6. Further, since only the belt driving roller 8 rotates idly, the driving force of the belt driving roller 8 is reliably transmitted to the belt 9 by the tension of the belt tension roller 17. The belt 9 has a loop shape and passes through the outside of the cabinet 6 to be introduced into the chamber 2 again.
[0029]
The temperature in the chamber 2 that has risen due to the lighting of the lamp heater 11 is measured by the thermocouple 15, and the measurement data is given to the temperature control unit 16. Based on this measurement data, the temperature control unit 16 controls the output of the lamp heater 11 so that the temperature in the chamber 2 becomes constant.
[0030]
In order to exhaust the organic solvent gas generated from the paste adhered to the substrate 10, fresh air is continuously supplied from the air supply units 18 and 19, and the in-chamber exhaust gas 25 is exhausted from the exhaust unit 30 to the outside. Air curtains 18 and 19 are provided in the vicinity of the substrate entrances 3 and 4 in order to keep the airflow and temperature in the chamber 2 constant. Moreover, in order to prevent the temperature rise of the conveyor furnace 1 and to operate safely, a cabinet 6 is provided so as to surround the chamber 2 and the heat insulating material 3, and outside air is taken in from the outside air intake port 14, and warm outside air is The air is exhausted from the cabinet exhaust port 24.
[0031]
The present embodiment has the following features. First, as a first point, an air heating unit 20 is provided on the side of the air curtains 18 and 19 to warm the air in the air curtains 18 and 19. Specifically, air at room temperature is set to a predetermined flow rate with a flow meter, and then preheated using a coil heater 20a whose temperature can be controlled by a thermocouple 20b, and then air heated from the air curtains 18 and 19 is heated. Is blowing out. As a result, the occurrence of condensation near the substrate entrances 3 and 4 is prevented.
[0032]
In addition, if the heating temperature of the air by the air heating unit 20 is set higher than the dew point of the organic solvent gas generated from the paste, it is possible to more effectively prevent the occurrence of condensation near the substrate entrances 3 and 4. For example, when the organic solvent gas is texanol, condensation is hardly generated in the air curtains 18 and 19 if the coil heater 20a is controlled to 140 ° C. to 300 ° C., which is equal to or higher than the dew point temperature.
[0033]
As a second point, the exhaust duct 31 shown in FIG. 2 is provided outside the air curtains 18 and 19 to suck the solvent gas leaked from the air curtains 18 and 19. As a result, the content of the solvent gas near the substrate entrances 3 and 4 is reduced, and the condensation of the solvent gas near the substrate entrances 3 and 4 is prevented. Further, since the solvent gas leaked from the air curtains 18 and 19 is not discharged to the outside through the substrate entrances 3 and 4, contamination of the atmosphere by the solvent gas can be effectively prevented.
[0034]
Instead of the air used in the air curtains 18 and 19, oxygen gas, nitrogen gas, argon gas, or a mixed gas thereof may be used. Here, since the air curtains 18 and 19 are generally the same as the gas flowing into the furnace, for example, in the case of a printing paste, oxygen is used for the purpose of burning a resin which is an organic component. Further, when sintering a metal such as solder, an inert gas such as nitrogen or argon is used for the purpose of preventing oxidation.
[0035]
As a third point, the gap between the cabinet 6 and the chamber 2 at the substrate entrances 3 and 4 is sealed with a heat insulating material 21. As a result, the paste vapor is not mixed into the exhaust gas 24 in the cabinet, so that condensation near the substrate entrances 3 and 4 is prevented and air pollution is also prevented. Here, the gap between the cabinet 6 and the chamber 2 is sealed with the heat insulating material 21, but it is not necessary to be a heat insulating material, and an aluminum foil tape or the like may be used.
[0036]
As a fourth point, a rubber heater 22 on the sheet is provided at the substrate entrance 4 to heat the solvent gas leaking from the air curtain 19. As a result, the occurrence of condensation at the substrate entrance 4 is prevented. Further, if the temperature of the solvent gas is set higher than the dew point temperature of the solvent gas, it is possible to more effectively prevent the occurrence of condensation near the substrate entrances 3 and 4. For example, when the solvent gas is texanol as described above, if texanol is heated to 140 ° C. or higher, almost no solvent condensation occurs. In FIG. 1, the rubber heater 22 is provided at the substrate entrance / exit 4 on the substrate 10 lead-out side, but the rubber heater 22 may be provided at the substrate entrance / exit 3 on the substrate 10 introduction side.
[0037]
As a fifth point, a solvent absorbing heat insulating material 23 is fixed on the rubber heater 22. As a result, even when the easy condensation of the solvent gas is generated, since the solvent-absorbing insulation material 23 absorbs the solvent gas can reliably prevent condensation of the solvent gas. As such a solvent-absorbing heat insulating material 23, for example, porous polyvinyl formal is suitable. Since polyvinyl formal can absorb the solvent up to about 10 times its own weight, maintenance is not required even if it is organic or inorganic saturated steam, or the conveyor furnace 1 is operated for a long time. In FIG. 1, the solvent absorption heat insulating material 23 is provided at the substrate entrance / exit 4 on the substrate 10 lead-out side, but the solvent absorption heat insulating material 23 may be provided at the substrate entrance / exit 3 on the substrate 10 introduction side.
[0038]
As a sixth point, the solvent gas generated from the paste is collected in the organic solvent trap 33 through the exhaust duct 32 in the chamber and the exhaust duct 31 outside the air curtain shown in FIG. The solvent gas collected in the organic solvent trap 33 is cooled by the fins 34, and the liquefied organic solution is accumulated in the organic solvent trap 33. Then, when a predetermined amount of the organic solution has accumulated in the organic solvent trap 33, the drain valve 35 can be operated to recover the organic solution. As a result, harmless exhaust gas from which the organic solvent component has been removed is released from the exhaust duct 25, and environmental pollution can be effectively prevented.
[0039]
【The invention's effect】
Since the conveyor furnace according to the present invention is configured as described above, the following effects can be obtained.
That is, the condensation of the solvent gas generated from the deposits can be prevented by heating the air curtain air in the air heating unit. As a result, pattern defects do not occur on the substrate, and the manufacturing cost can be reduced.
[0040]
In addition, condensation of the solvent gas at the substrate entrance and exit can be prevented by absorption of the solvent gas by the air duct outside the air curtain. As a result, pattern defects do not occur on the substrate, and the manufacturing cost can be reduced. Further, since the solvent gas does not leak to the outside air, air pollution can be effectively prevented.
[0041]
Further, the sealing portion provided between the chamber and the cabinet can prevent condensation of the solvent gas at the substrate entrance / exit. As a result, pattern defects do not occur on the substrate, and the manufacturing cost can be reduced. Further, since the solvent gas does not leak to the outside air, air pollution can be effectively prevented.
[0042]
Further, by providing the solvent gas heating unit in the vicinity of the substrate inlet / outlet, condensation of the solvent gas at the substrate inlet / outlet can be prevented. As a result, pattern defects do not occur on the substrate, and the manufacturing cost can be reduced.
[0043]
Furthermore, by providing a solvent absorbing portion in the vicinity of the substrate inlet / outlet, condensation of the solvent gas at the substrate inlet / outlet can be prevented. As a result, pattern defects do not occur on the substrate, and the manufacturing cost can be reduced.
[0044]
In addition, by providing a liquid reservoir that liquefies and collects the solvent gas exhausted from the exhaust duct in the chamber, the organic solution is reliably recovered, and harmless exhaust gas from which organic solvent components have been removed is released to the outside. The As a result, since the solvent gas does not leak into the outside air, air pollution can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a conveyor furnace according to the present embodiment.
FIG. 2 is a cross-sectional view showing an exhaust unit.
FIG. 3 is a cross-sectional view showing an air curtain and an air heating unit.
FIG. 4 is a view showing a rubber heater.
FIG. 5 is a sectional view showing a conveyor furnace according to the prior art.
FIG. 6 is an enlarged sectional view showing a part of a conveyor furnace according to the prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Conveyor furnace, 2 ... Chamber, 3, 4 ... Substrate entrance / exit, 6 ... Cabinet, 10 ... Substrate, 18, 19 ... Air curtain, 20 ... Air heating part, 21 ... Thermal insulation (sealing part), 22 ... Rubber Heater (substrate inlet / outlet heating section), 23 ... Solvent absorption heat insulating material (solvent absorption section), 31 ... Exhaust duct outside air curtain, 32 ... Exhaust duct in chamber, 33 ... Organic solvent trap (liquid reservoir), 35 ... Drain valve (Solvent recovery unit).

Claims (1)

In a conveyor furnace that passes a substrate through a chamber provided with heating / drying means and dries or fires the deposits deposited on the substrate,
An air curtain provided at the substrate entrance of the chamber;
An air heating section for heating the air curtain air;
An outside air curtain exhaust duct for exhausting gas leaked from the air curtain, provided on the outside of the air curtain ;
The air heating unit heats the air so that the temperature of the air curtain air is higher than the dew point of the solvent gas generated from the deposit,
An exhaust duct in the chamber for exhausting the solvent gas generated from the deposit;
A liquid reservoir for liquefying and collecting the solvent gas discharged from the chamber exhaust duct;
A solvent recovery unit for recovering the liquid solvent collected in the liquid reservoir;
A substrate entrance / exit heating section that is provided at the substrate entrance / exit of the chamber and heats the substrate entrance / exit of the chamber;
The substrate entrance / exit heating section heats the substrate entrance / exit of the chamber to a temperature higher than the dew point of the solvent gas generated from the deposit,
A conveyor furnace , further comprising a solvent absorbing portion that is provided in the vicinity of a substrate inlet / outlet of the chamber and absorbs a solvent gas generated from the deposit.

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