JPH04344869A - Heat treatment device - Google Patents

Abstract

PURPOSE:To prevent the object to be treated from falling and being deformed by detecting a temperature of plural parts of a carrying chain supporting guide which passes through the inside of a heat treatment device main body. CONSTITUTION:In a heat treatment device for placing a side edge part of an object 2 to be treated on an end part of a carrying chain 7 and moving it in a heat treatment device maim body, temperature difference measuring sensors 12, 13 are provided in plural parts in the width direction of a supporting guide, a heater 11 for raising a temperature of a low temperature part and reducing a temperature difference is provided additionally, and also, a controller 15 for reducing a temperature difference is provided. In such a way, a curvature of the guide generated due to an ununiform temperature caused by a fluctuation of a position condition of the guide, and a fall and a deformation of the object to be treated, based thereon can be prevented.

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 applying heat treatment to a workpiece that is continuously moved within the main body of the heat treatment apparatus.

0002

2. Description of the Related Art Conventional examples of heat treatment equipment (for example, solder reflow) are shown in FIGS. 3 to 7.

FIG. 3(a) is a schematic side view of a heat treatment apparatus. Figure 3(b) is similar to Figure 3(a) and Figure 3(c) described below.
2 is a graph schematically representing the temperature distribution inside the heat treatment apparatus shown in FIG. FIG. 3(c) is a schematic plan view of the heat treatment apparatus.

FIG. 4 is a sectional view taken along the line IV--IV in FIG. 3.

[0005] FIGS. 5A to 5C are conceptual diagrams showing only the guide passing through the main body of the heat treatment apparatus and illustrating how the guide is curved.

Furthermore, 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 mounted on a processing object support means such as a roller chain.

In a heat treatment apparatus such as solder reflow for soldering an electronic component 18 to a printed circuit board 17 shown in FIGS. 6 and 7, the electronic component 18 is placed on the printed circuit board 17, and a paste solder (diameter A workpiece for continuously transporting a workpiece 2 to which solder particles of ~50 μmφ are dispersed in flux paste (1/2 of solder particles having a diameter of ~50 μm in flux paste) is conveyed in a heat treatment apparatus main body 3 shown in FIGS. 3 and 4. A conveyor chain 7 serving as a support means and a guide 4 for supporting the conveyor chain 7 are provided. The conveyance chain 7 is operated by a conveyance pulley 8 and a driving pulley 9 placed on the heat treatment apparatus pedestal 10 . Note that the conveyance chain 7 may be another trackless mechanical component. 6 and 7, 19 represents printed wiring, 20 represents solder (paste solder or cream solder), and 21 represents a hole penetrating the printed circuit board.

The workpiece 2 shown in FIGS. 3 and 4 is supported at both ends by pins 5 of a conveyor chain with a length of within several millimeters (in this example, within 3 mm), and is moved inside the heat treatment apparatus main body 3. . Two conveyor chains 7 and guides 4 for supporting the conveyor chains 7 shown in FIG. It is movable so that it can be supported even when the size of the workpiece 2 is different. (In other words, it can be moved as shown by the imaginary line in FIG. 4 using a handle, etc. not shown.)

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

FIG. 3(b) shows an example of the temperature distribution of the object 2 as it moves inside the heat treatment apparatus main body 3. In this graph, the temperature of the workpiece 2 is immediately raised when it enters the furnace, it moves a certain distance while being kept at a constant temperature (for example, 150 to 170 °C), and then it is further heated to reach the maximum temperature ( Tmax) is reached. Tmax is a temperature below the heat-resistant temperature of the electronic component 18 mounted on the printed circuit board 17 and at which soldering is possible (for example, 215 to 220
℃). After reaching Tmax, the workpiece 2
temperature decreases. The time required for the object 2 to pass through the furnace is, for example, 3 to 4 minutes. A1, A2, shown in FIG. 3(c),
B1 and B2 are the inner surface (A1, A2) and outer surface (B1, B2) of the guide 4 at the Tmax portion.
represents.

By the way, the above heat treatment apparatus has the following problems. a) A case where one or both of the guides 4 is adjusted to match the width of the object 2 to be processed. Specifically, in FIG. 4, the distance D between both guides changes because the guide 4 is moved, for example, to the position of the imaginary line, or from the position of the imaginary line to the position of the solid line. b) When there are many types of objects 2 to be processed (printed circuit boards 17, etc.), and their heat capacities are not constant.

In the above case, the thermal conditions inside the heat treatment apparatus main body 3 change over 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. Due to its short length,
The workpiece 2 may fall off the conveyor chain 7 or be compressed and deformed.

In FIG. 5, TA1, TA2, TB
1 and TB2 are A1 of the guide 4 shown in FIG. 4, respectively.
, A2 , B1 and B2 . When there is no temperature difference between the inner and outer surfaces of the guide 4, that is, TA1 =
When TB1, TA2 = TB2, Fig. 5(a)
The guide 4 does not curve as shown in FIG.

However, for the reason mentioned above, when the temperature condition changes when the guide is moved and the temperature on the guide side surface becomes uneven, the temperature on the inner side surface of the guide becomes lower than the temperature on the outer surface as shown in FIG. 5(b). (i.e. TA1 > TB1
, TA2 > TB2) A curvature occurs and guide 4
or the temperature of the outer surface of the guide becomes higher than the temperature of the inner surface (i.e. TA1
<TB1, TA2 <TB2) Guide 4
There was a problem that the interval between

In order to solve the above-mentioned problem, the conventional methods have been to use a sturdy member for the guide 4, change the arrangement of the heater 6 for heating the furnace, or install a fan to improve the uniformity in the furnace. They were trying to prevent the guide 4 from curving by increasing the heat. However, when the positional relationship of each type of workpiece 2 changes, it is difficult to determine the optimal conditions one by one.
In the end, the current situation is that the system has been operated in an insufficient manner.

[0016]

[Object of the Invention] The object of the present invention is to solve the problem of curvature of the guide, which occurs due to uneven temperature when the positional conditions of the guide change, even if the temperature inside the heat treatment apparatus body is uniform, and the curvature caused by the curvature. An object of the present invention is to provide a heat treatment apparatus equipped with a means for preventing objects to be treated from falling and being deformed.

[0017]

[Structure of the Invention] That is, the present invention provides a heat treatment method having a heat treatment apparatus main body; a guide passing through the heat treatment apparatus main body; and a workpiece supporting means guided by the guide and moved within the heat treatment apparatus main body. In the apparatus, a heating means for heating a predetermined portion of the guide, a temperature detection means for detecting temperatures at a plurality of locations on the guide, and operating the heating means based on a temperature detection result by the temperature detection means. Accordingly, there is provided a heat treatment apparatus characterized by having a temperature control means for controlling the temperature so as to reduce the temperature difference between a plurality of locations on the guide.

[0018]

[Examples] Examples of the present invention will be described below.

FIGS. 1 and 2 are schematic diagrams representing the present invention.

FIG. 1 is a diagram schematically showing a part of a cross section taken along the line IV--IV in FIG. 3, that is, the position where the temperature is Tmax (for example, 230° C.). Although the heat treatment apparatus body 3 is not shown and only one side of the support means for the object to be treated is shown, the same applies to the other side. put it here,
A control heater 11 that can withstand Tmax is attached to the outer surface B1 on the outside of the guide 4.

Regarding the method of wiring the control heater 11, temperature detecting elements 12 and 13 are attached to both sides of A1 and B1, and the wiring is done so that the outputs from both cancel each other out.

When thermocouples are used as the temperature detection elements 12 and 13, for example, they are connected in series as +- and -+ as shown in FIG. Furthermore, when employing resistance elements 32 and 33 such as thermistors, bridge connection is performed as shown in FIG.

For zero point adjustment at room temperature, for example, when using a thermocouple, connect the voltage deviation setter 14 shown in FIG. 1 and set the output at room temperature to 0. In addition, when using a resistance element, the output at room temperature can be set to 0 by adjusting the variable resistor VR shown in Fig. 2(a) (however, R1 =
R2), and a voltage deviation setting device may also be used. In addition,
FIG. 2(b) is a circuit diagram of a resistance bridge when using a resistance element. Even when a thermometer of a type other than the above is used, the temperature difference is detected in the same manner.

By the temperature detection method described above, the temperature difference between the inner and outer surfaces of the guide 4 at Tmax is detected, and a deviation signal due to this temperature difference is applied to the voltage deviation setting device 1 of 0±ΔV.
PID (proportional, integral,
Differential operation) is input to the controller 15. The output of the PID controller is input to the power adjustment circuit 16 of the control heater 11, forming an automatic temperature control circuit.

In the above example, point A1 and point B1
point, and points A2 and B2 (not shown in Figure 3(c)
), see Figure 4) is detected, and temperature TA1 and temperature T are detected.
The control heater 11 is operated so as to eliminate or minimize the difference between the temperatures TA2 and TB2 and the difference between the temperatures TA2 and TB2 (see FIG. 5). Therefore, the guide curvature caused by the difference in thermal expansion caused by the temperature difference on both sides of the guide as shown in FIG. 5(b) or FIG. 5(c) is prevented, and
) can maintain a straight line. the result,
The printed circuit board will not fall off the roller chain, nor will it be deformed by being pushed by the roller chain. Further, since the control heater 11 is operated by PID control, the temperature control described above is performed with high precision and is highly reliable.

The present invention can be modified in various ways other than those described above.

Generally, the internal temperature of the heat treatment apparatus main body 3 is as follows:
It is highest in the center and gets lower as you move away from the center. For this reason, although the control heater 11 is often attached to the outer surface of the guide 4 as shown in the above embodiment, it is also possible to attach it to the inner surface of the guide 4.

It is also possible to attach the control heater 11 to both the inner and outer surfaces of the guide 4, but in this case, not only the temperature difference control but also the
It is necessary to control the temperature so that it does not exceed Tmax.

Furthermore, the present invention is applicable not only to continuous processing but also to batch type heat treatment equipment, and it goes without saying that the object to be processed may be other than printed circuit boards.

[0030]

Effects of the Invention: The present invention detects the temperature at multiple locations on the guide and controls to reduce the difference between the detected temperatures. Deformation of the guide is prevented. As a result, the heat-treated object does not come off from the object-to-be-processed support means guided by the guide, or is deformed by being caught between the object-to-be-processed support means, and is safely moved and subjected to heat treatment. .

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the 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 variable element according to an embodiment of the present invention is used.

FIG. 3 is a schematic side view and plan view of a conventional heat treatment apparatus, and a temperature distribution diagram.

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

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

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

FIG. 7 is a schematic diagram of a printed circuit board loaded on the end of a conveying chain.

[Explanation of symbols]

1 Heat treatment device 2 Workpiece 3 Heat treatment device main body 4 Support guide 5 (conveyance chain) pin 6 Furnace heating heater 7 Conveyance chain 8 Conveyance pulley 9 Drive pulley 10 Heat treatment device stand 11 Control heaters 12, 13, 32, 33 Temperature detection element 14
Voltage deviation setting device 15 PID controller 16 Power adjustment circuit 17 Printed circuit board 18 Electronic components 19 Printed wiring 20 Solder 21 Printed circuit board through hole

Claims (1)

[Claims] 1. A heat treatment apparatus comprising: a heat treatment apparatus main body; a guide passing through the heat treatment apparatus main body; and a workpiece support means guided by the guide and moved within the heat treatment apparatus main body, wherein the guide A heating means for heating a predetermined portion, a temperature detection means for detecting temperatures at a plurality of locations on the guide, and operating the heating means based on the temperature detection result by the temperature detection means,
A heat treatment apparatus comprising: temperature control means for controlling temperature so as to reduce temperature differences between a plurality of locations on the guide.