JPH0739031B2 - Heat treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment apparatus, and more particularly to a heat treatment apparatus for subjecting an object to be continuously moved in a heat treatment apparatus body to heat treatment.

[0002]

2. Description of the Related Art A conventional example of a heat treatment apparatus (for example, solder reflow) is shown in FIGS.

FIG. 3A is a schematic side view of the heat treatment apparatus. FIG. 3B shows FIG. 3A and FIG. 3C described later.
3 is a graph schematically showing the temperature distribution inside the heat treatment apparatus shown in FIG. FIG. 3C is a schematic plan view of the heat treatment apparatus.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIGS. 5 (a) to 5 (c) are conceptual views showing only a guide penetrating the inside of the main body of the heat treatment apparatus and showing the curved state thereof.

Further, FIG. 6 is a partial plan view showing an example of a printed circuit board, and FIG. 7 shows an example in which the printed circuit board is placed on an object support means such as a roller chain.

In a heat treatment apparatus such as solder reflow for soldering the electronic component 18 to the printed board 17 shown in FIGS. 6 and 7, the electronic component 18 is placed on the printed board 17 and paste-like solder (diameter 15 An object to be continuously conveyed in the heat treatment apparatus main body 3 shown in FIGS. 3 and 4, the object 2 to which the solder particles having a particle size of 50 μmφ are dispersed 1/2 in the flux paste. A transport chain 7 as a support means and a guide 4 for supporting this are provided. The transport chain 7 is operated by a transport pulley 8 and a drive pulley 9 placed on a heat treatment apparatus mount 10. The transport chain 7 may be another trackless mechanism component. 6 and 7, 19 is a printed wiring, 20 is a solder (paste solder or cream solder), and 21 is a hole penetrating the printed circuit board.

The object 2 shown in FIGS. 3 and 4 is supported at both ends by pins 5 of a conveying chain having a length within a few millimeters (in this example, within 3 mm) and moves inside the heat treatment apparatus main body 3. . Two conveying chains 7 and guides 4 for supporting the conveying chains 7 shown in FIG. 4 are arranged facing each other so as to support both side edges of the object to be processed 2 by a pin 5, and one or both of them are It is movable so that it can be supported even when the size of the processed material 2 is different. (That is, it can be moved like a virtual line in FIG. 4 by using a handle or the like not shown.)

As shown in FIG. 3, the guide 4 is arranged so as to penetrate the heat treatment apparatus main body 3 having a plurality of heaters 6 for heating the inside of the furnace, and the carrier chain 7 supported by the guide 4 is
The object 2 to be processed is placed and moved inside the heat treatment apparatus main body 3. As the heater 6 for heating the inside of the furnace, a hot air heater (using air or nitrogen gas) and a far infrared heater are used together.

FIG. 3B shows an example of the temperature distribution of the object to be processed 2 as it moves inside the heat treatment apparatus body 3. In this graph, the object to be treated 2 is heated immediately upon entering the furnace, moves a fixed distance while being maintained at a constant temperature (for example, 150 to 170 ° C.), and is further heated to the maximum temperature ( Tmax) is reached. Tmax is controlled to a temperature equal to or lower than the heat resistant temperature of the electronic component 18 mounted on the printed board 17, and at a solderable temperature (for example, 215 to 220 ° C.). After reaching Tmax, the temperature of the object to be processed 2 decreases. The passage time of the object 2 to be processed in the furnace is, for example, 3 to 4 minutes. A ₁ , A ₂ , B ₁ and B ₂ shown in FIG.
The inner side surface (A ₁ , A ₂ ) and the outer side surface (B ₁ , B ₂ ) of the guide 4 in the max portion are shown.

However, the above heat treatment apparatus has the following problems. a) When one or both of the guides 4 are moved and adjusted to match the width of the object to be processed 2. Specifically, in FIG. 4, when the guide 4 is moved to, for example, the position of the virtual line or moved from the position of the virtual line to the position of the solid line, the distance D between the two guides changes. b) When the heat capacities of the objects to be processed 2 (printed circuit board 17 etc.) vary widely and are not constant.

In the above case, the thermal conditions inside the heat treatment apparatus main body 3 change with time, and the temperature inside the furnace becomes non-uniform in the IV-IV line direction. As a result, the guide 4 made of metal such as stainless steel undergoes thermal expansion deformation as shown in FIG. 5B or 5C, and the pin 5 for supporting the object to be processed is several mm or less. Due to the short length, the workpiece 2 may fall from the transport chain 7 or may be compressed and deformed.

In FIG. 5, TA ₁ , TA ₂ , TB ₁ and TB ₂ are A ₁ , A ₂ and A ₂ of the guide 4 shown in FIG. 4, respectively.
The temperatures of B ₁ and B ₂ are shown. When there is no temperature difference between the inner surface and the outer surface of the guide 4, that is, TA ₁ = TB ₁ , TA ₂ =
At TB ₂ , the guide 4 does not bend as shown in FIG.

However, for the above reason, when the temperature condition changes when the guide is moved and the side temperature of the guide becomes non-uniform, the inside temperature of the guide is higher than the outside temperature as shown in FIG. 5B. Also becomes higher (ie TA ₁ > TB ₁ ,
TA _2> TB ₂ and turned in) or caught the interval curvature occurs guide 4, or the guide outer surface temperature as shown in FIG. 5 (c) is higher than the inner surface temperature (i.e. TA ₁ <T
There was a problem that the distance between the guides 4 was increased (B ₁ , TA ₂ <TB ₂ ).

In order to solve the above-mentioned problem, conventionally, a strong member is used for the guide 4, or the heater 6 for heating the furnace is changed in arrangement, or a fan is provided so that the inside of the furnace is leveled. I was trying to prevent heat from bending the guide 4 with heat. However, since it is difficult to determine the optimum conditions one by one when the positional relationship of each of the various processed objects 2 changes,
After all, it was the current situation that the car was driven insufficiently.

[0016]

SUMMARY OF THE INVENTION The object of the present invention is caused by the bending and bending of the guide caused by the non-uniform temperature when the position condition of the guide changes even if the temperature inside the heat treatment apparatus main body is uniform. It is an object of the present invention to provide a heat treatment apparatus having means for preventing the object to be processed from falling and deforming.

[0017]

That is, the present invention is a heat treatment having a heat treatment apparatus main body; a guide penetrating the heat treatment apparatus main body; and an object support means which is guided by the guide and moves in the heat treatment apparatus main body. In the device, a heating means for heating a predetermined portion of the guide, and a length of the guide.
Multiple to detect the temperature of both sides in the cross section perpendicular to the direction
A temperature detecting means, this by actuating the heating means based on a temperature detection result of these temperature detection means, the temperature control for temperature control so as to reduce the temperature difference between both sides in the cross section of the guide The present invention provides a heat treatment apparatus characterized by having means.

[0018]

EXAMPLES Examples of the present invention will be described below.

1 and 2 are schematic diagrams showing the present invention.

FIG. 1 is a diagram schematically showing a part of the cross section at the position of line IV-IV in FIG. 3, that is, at the position where the temperature is Tmax (for example, 230 ° C.). Although the heat treatment apparatus main body 3 is not shown in the figure and only one object support means is shown, the other side is also the same. Where Tma
A control heater 11 capable of withstanding x is attached to a point B ₁ on the outer side surface of the guide 4.

The connection method of the control heater 11 will be described. The positions indicated by A ₁ and B ₁ on both sides of the guide 4 are described.
Attached respectively temperature detecting element 12 and 13 to location, wiring so that the output from both is canceled each other.

When, for example, thermocouples are used as the temperature detecting elements 12 and 13, they are connected in series as +-and-+ as shown in FIG. Also, a resistance element such as a thermistor
Even when 32 and 33 are adopted, bridge connection is performed as shown in FIG.

To adjust the zero point at room temperature, for example, when a thermocouple is used, the voltage deviation setter 14 shown in FIG. 1 is connected and the output at room temperature is set to zero. When a resistance element is used, the output at room temperature can be set to 0 by adjusting the variable resistance VR shown in FIG. 2A (however, R ₁ =
R ₂ ), and also a voltage deviation setter may be used together. Note that FIG. 2B is a circuit diagram of a resistance bridge when a resistance element is used. Even when a thermometer of a method other than the above is adopted, the method of detecting the temperature difference is similarly performed.

By the temperature detection method described above, the temperature difference between the inner surface and the outer surface of the guide 4 at Tmax is detected, and the deviation signal due to this temperature difference is used as the voltage deviation setter 14 of 0 ± ΔV.
Via PID (Proportional, Integral, Derivative operation) controller 15 installed separately from the furnace temperature control. The output of the PID controller is used as the input of the power adjustment circuit 16 of the control heater 11 to form an automatic temperature control circuit.

In the above example, points A ₁ and B _{1 and} points A ₂ and B ₂ (not shown) are shown (FIG. 3 (c), FIG. 4).
(See FIG. 5) and operate the control heater 11 so as to eliminate or reduce the difference between the temperature TA ₁ and the temperature TB ₁ and the difference between the temperature TA ₂ and the TB ₂ (see FIG. 5). There is. Accordingly, and FIG. 5 (b) or guide curved due to the difference in thermal expansion due to the temperature difference between FIG. (C) to indicate such guide both side surfaces is prevented, always a straight line shape as in FIG (a) Can be maintained. As a result, the printed circuit board is prevented from falling off the roller chain and being deformed by being pushed by the roller chain. Further, since the operation of the control heater 11 is based on the PID control, the temperature control described above is performed with high accuracy and is highly reliable.

The present invention can be variously modified other than the above.

Generally, the internal temperature of the heat treatment apparatus body 3 is
The center is the highest, and the lower the distance from the center, the lower the height. For this reason, as shown in the above embodiment, the control heater 11 is often attached to the outer side surface of the guide 4, but conversely, it can be attached to the inner side surface of the guide 4.

Further, the control heater 11 is guided to the guide 4
It is also possible to attach them to both the inner side surface and the outer side surface, but in this case, not only the temperature difference control but also the control so that the temperature of the guide 4 does not exceed Tmax is required.

Furthermore, the present invention can be applied not only to continuous processing but also to a batch type heat treatment apparatus, and it goes without saying that the object to be processed may be other than a printed circuit board.

[0030]

According to the present invention, the breaking of the guide is perpendicular to the longitudinal direction.
Since the temperatures of both sides of the surface are detected and the temperature differences are controlled so as to be small, the deformation of the guide due to the difference in thermal expansion due to the temperature difference between the both sides is prevented. As a result, the object to be treated is dislodged from the object to be treated support means guided in the guide, or not deformed or pinched to the object to be processed support means, a heat treatment and moved safely subjected It

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a highest temperature part in a heat treatment apparatus according to an embodiment of the present invention and a circuit diagram when a thermocouple is used.

FIG. 2 is a part of a circuit diagram when a temperature / resistance change element according to an exemplary embodiment of the present invention is used.

FIG. 3 is a schematic view and a temperature distribution diagram of a side surface and a plane surface of a heat treatment apparatus of a conventional example.

FIG. 4 is a schematic cross-sectional view of the highest temperature part of a conventional heat treatment apparatus body.

FIG. 5 is a conceptual diagram of a guide curve of a conventional example.

FIG. 6 is a partial cross-sectional view showing an example of a printed circuit board.

FIG. 7 is a schematic view of a printed circuit board loaded on the end of the transport chain.

[Explanation of symbols]

 1 Heat Treatment Equipment 2 Heat Treatment Equipment 3 Heat Treatment Equipment Body 4 Support Guide 5 (Conveyor Chain) Pin 6 Furnace Heating Heater 7 Conveyor Chain 8 Conveyor Pulley 9 Drive Pulley 10 Heat Treater Stand 11 Control Heater 12, 13, 32, 33 Temperature detection element 14 Voltage deviation setter 15 PID controller 16 Power adjustment circuit 17 Printed circuit board 18 Electronic parts 19 Printed wiring 20 Solder 21 Printed board through hole

Claims (1)

[Claims] 1. A heat treatment apparatus comprising: a heat treatment apparatus main body; a guide that penetrates through the heat treatment apparatus main body; and a workpiece support means that is guided by the guide and moves within the heat treatment apparatus main body. A heating means for heating a predetermined portion, and a cross section perpendicular to the longitudinal direction of the guide.
By operating a plurality of temperature detection means for detecting the temperature of both sides, said heating means based on a temperature detection result of these temperature detection means in the guide of the
And a temperature control means for controlling the temperature so as to reduce the temperature difference between both side surfaces in the cross section .