JP2002026508A - Reflow furnace and heating method using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflow furnace which is reduced in cost by simplifying its structure and can more uniformly heat an object to be heated in the heating-up section of the object and can keep the temperature of the object constant in the temperature-keeping section of the object. SOLUTION: This reflow furnace is provided with a first heat insulating structure section 12 which thermally insulates an object preheating zone PH in which the object 8 to be heated is preheated from the outside, a first air heating heater 50 which heats the object 8 in the section 12 with hot air, and first infrared heaters 60A and 60B which heat the object 8 in the section 12. The furnace is also provided with a first air circulating section 40 which circulates the air in the section 12, a second heat insulating structure section 14 which thermally insulates a properly object heating zone RF in which the preheated object 8 is properly heated and is integrated with the first heat insulating structure section 12, and a second air heating heater 150 which heats the object 8 in the section 14 with hot air. In addition, the furnace is also provided with second infrared heaters 160A and 160B which heat the object 8 in the section 14 and a second air circulating section 140 which circulates the air in the section 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow furnace for heating an object to be heated such as a printed circuit board when the object is conveyed, and a heating method using the reflow furnace.

[0002]

2. Description of the Related Art For example, surface mount devices (Surf)
2. Description of the Related Art Reflow soldering is known as a mounting technique for mechanically fixing an electronic component such as an mounted device) by conductively connecting it to a printed circuit board. In reflow soldering technology, device leads are aligned and mounted on a printed board on which solder paste has been printed in advance, and the board is heated by passing it through a reflow oven, thereby melting the solder and allowing the device to be printed on the printed board. Solder the leads. A reflow furnace for performing this reflow soldering method has a preheating section (preliminary heating section) and a reflow section (main heating section) as shown in FIGS. As the printed circuit board 1020 is transported along the preheating section 1000 and the reflow section 1010, the printed circuit board 1020 is fully heated after being preheated.

FIG. 9 shows a temperature profile required for a conventional reflow furnace, and FIG. 10 shows a structure of a conventional reflow furnace for realizing this temperature profile. The structure of the reflow furnace shown in FIG. 10 has a total of three boxes. The preheating unit 1000 includes two boxes 1030 and 1040, and the reflow unit 1010 includes one box 1050. Each box 103
Reference numerals 0, 1040, and 1050 heat the printed circuit board 1020 using both infrared rays and hot air. Boxes 1030 and 1040 have fan 103 respectively.
1, infrared heater 1032, infrared heater 1033
have. Box 1050 contains fan 1051,
An infrared heater 1052 and an infrared heater 1053 are provided. The fans 1031 and 1051 are rotated by motors 1034 and 1054, respectively.

[0004]

The reflow furnace of this type has a structure in which, when the fan 1031 or the fan 1051 rotates, the air is heated when passing through the holes of the infrared heaters 1032 and 1052 to generate hot air. For this reason, it is difficult to independently control the temperature of the hot air and the heating temperature of the infrared heater by infrared rays because the temperature of the hot air depends on the infrared heaters 1032 and 1052. When the temperature of hot air and the heating temperature by infrared rays are controlled independently, each box 1030, 1040, 105
With respect to 0, an infrared heater and a heater for hot air must be provided, respectively, and the structure becomes complicated, resulting in an expensive device. Furthermore, if an infrared heater is used in a section where it is desired to maintain a constant temperature, a difference in infrared absorptance of electronic components on the printed circuit board causes a temperature difference in the printed circuit board, resulting in a non-uniform temperature of the printed circuit board. There are points.

FIGS. 11 and 12 show another conventional reflow furnace. In the reflow furnace of FIG. 10, three zones are formed by a total of three boxes. In the reflow furnace of FIG. 12, a total of four boxes 1130, 1140, 1
150 and 1160 form four zones.
The preheating unit 1200 has two boxes 1130 and 11
40, and the reflow unit 1210 includes two boxes 1
150 and 1160. The box 1130 and the box 1140 have a fan 1131 and infrared heaters 1132 and 1133, respectively. Two boxes 1
Each of 150 and 1160 has a fan 1151, an infrared heater 1152, and an infrared heater 1153. The reflow furnace having such a structure is provided with a printed circuit board 10.
This is a case where the solder used in No. 20 is a lead-free solder. In this case, in the reflow unit 1210,
Since the reflow temperature must be maintained for a certain period of time, a box 1160 for maintaining the temperature constant is required in addition to the box 1150 for heating. The structure of this reflow furnace has a problem that the number of boxes increases and each box requires a fan and an infrared heater, which makes it difficult to reduce the cost. Therefore, the present invention solves the above-mentioned problems, and has a simple structure and can reduce the cost. The object to be heated can be more uniformly heated in a temperature rising section of the object to be heated. It is an object of the present invention to provide a reflow oven capable of keeping the temperature of the reflow oven constant and a heating method using the reflow oven.

[0006]

According to a first aspect of the present invention, there is provided a reflow furnace for heating an object to be heated when the object to be heated is conveyed, wherein a preheating zone for preheating the object to be heated is provided. A first heat insulating structure formed by heat insulation from the outside, a first air heater arranged in the first heat insulating structure and heating the object to be heated with hot air, and a first air heater arranged in the first heat insulating structure. And heating the object to be heated with infrared rays.
An infrared heater, a first air circulating unit disposed in the first heat insulating structure, and circulating air in the first heat insulating structure, and a main heating zone for main heating the preheated object to be heated. A second heat-insulating structure formed insulated from the second heat-insulating structure, wherein the second heat-insulating structure is formed as an integral structure with the first heat-insulating structure; And heating the object to be heated with hot air.
An air heating heater, a second infrared heater arranged in the second heat insulating structure for heating the object to be heated with infrared light, and an air heater disposed in the second heat insulating structure and air in the second heat insulating structure. And a second air circulating unit that circulates water.

According to the first aspect, the first heat insulating structure is formed by insulating a preheating zone for preheating the object to be heated from the outside. The first air heating heater, the first infrared heater, and the first air circulation unit are disposed in the first heat insulating structure. The object to be heated is heated by hot air by the first air heater. The first infrared heater heats the object to be heated with infrared light. The first air circulation unit circulates the air in the first heat insulating structure. The second heat insulating structure is formed by thermally insulating a main heating zone for main heating the preheated object to be heated, and the second heat insulating structure is formed as an integral structure with the first heat insulating structure. ing. In the second heat insulating structure,
An air heater, a second infrared heater, and a second air circulation unit are arranged. The second air heater heats the object to be heated with hot air. The second infrared heater heats the object to be heated with infrared light. The second air circulation unit circulates the air in the second heat insulating structure. Thereby, since the first heat insulating structure and the second heat insulating structure are formed as an integrated structure, the structure of the reflow furnace can be simplified and the cost can be reduced. Since the air circulation in the first heat insulation structure is performed by the first air circulation unit and the air circulation in the second heat insulation structure is performed by the second air circulation unit, the air in the first heat insulation structure and the second heat insulation structure is air-cooled. The circulation structure can be simplified, and the structure can be simplified and the cost can be reduced.

According to a second aspect of the present invention, in the reflow furnace according to the first aspect, the hot air at a target temperature by the first air heater and the infrared light by the first infrared heater are provided in the first heat insulating structure. And a temperature maintaining section for heating the object to be heated by the first air heater with the hot air having a target temperature. In the second aspect, in the temperature rising section in the first heat insulating structure, the temperature of the object to be heated is increased by the hot air of the target temperature by the first air heater and the heating by the infrared rays by the first infrared heater. On the other hand, in the temperature holding section in the first heat insulating structure,
Heating is performed by hot air at a target temperature by an air heater. Accordingly, in the heating section, the object to be heated, such as a component or a printed circuit board, can be heated more uniformly because of the combined use of the infrared rays and the hot air having the target temperature. In the temperature holding section, the temperature is held by the convection of hot air at the target temperature,
The temperature of the object to be heated can be kept constant.

According to a third aspect of the present invention, in the reflow furnace according to the second aspect, the hot air at a target temperature by the second air heater and the infrared light by the second infrared heater are provided in the second heat insulating structure. And a temperature holding section for heating the object to be heated by the hot air at a target temperature by the second air heater. In the third aspect, in the temperature rising section in the second heat insulating structure, heating is performed by hot air of the target temperature by the second air heater and infrared light by the second infrared heater. On the other hand, in the temperature holding section in the second heat insulating structure, heating is performed by hot air of the target temperature by the second air heater. Accordingly, in the heating section, the main heating of the object to be heated can be performed uniformly because of the combined heating of the infrared rays and the hot air at the target temperature. In the temperature holding section, since the heating is performed by the convection of the hot air at the target temperature, the temperature of the main heated object can be kept constant.

According to a fourth aspect of the present invention, in the reflow furnace according to the first aspect, the first infrared heater and the second infrared heater are provided with a temperature sensor on one surface side for generating infrared light. A heat insulating material is disposed on the other surface side for preventing occurrence. According to the fourth aspect, a heat insulating material is disposed on the other surface of the first infrared heater and the second infrared heater for preventing generation of infrared rays. Accordingly, the heat insulating material can prevent infrared rays from being generated from the other surface of the first infrared heater or the second infrared heater, and can prevent hot air from receiving excessive heat from the surface of the infrared heater.

According to a fifth aspect of the present invention, in the reflow furnace according to the first aspect, the first infrared heater and the second infrared heater are divided into a plurality in the direction in which the object to be heated is conveyed. Thereby, it has a hot air passage for blowing hot air to the object to be heated. According to the fifth aspect, the hot air can be directly blown from the hot air passage of the first infrared heater or the second infrared heater to the object to be heated.

The invention according to claim 6 is a heating method using a reflow furnace for heating the object to be heated when the object to be heated is conveyed, wherein a preheating zone for preheating the object to be heated is thermally insulated from outside. In the first heat-insulating structure section formed as described above, the first air circulation section circulates the air in the first heat-insulating structure section, heats the object to be heated with hot air by the first air heater, The object to be heated is heated with infrared rays by an infrared heater, and a main heating zone for main heating the preheated object to be heated is formed by being insulated from the outside, and is integrally formed with the first heat insulating structure. In the second heat insulating structure formed as a body, a second air circulating unit circulates air in the second heat insulating structure, and heats the object to be heated with hot air using a second air heater. 2 Add the above by infrared heater A heating method by a reflow furnace, which comprises heating an object by infrared radiation.

According to a sixth aspect of the present invention, the first heat-insulating structure is formed such that a preheating zone for preheating the object to be heated is thermally insulated from the outside. In the first heat insulating structure, the object to be heated is heated by the first air heater with hot air. The first infrared heater heats the object to be heated with infrared light. The first air circulation unit circulates the air in the first heat insulating structure. The second heat insulating structure is formed by thermally insulating a main heating zone for main heating the preheated object to be heated, and the second heat insulating structure is formed as an integral structure with the first heat insulating structure. ing. In the second heat insulating structure, a second air heater, a second infrared heater, and a second air circulation unit are arranged. The second air heater heats the object to be heated with hot air. The second infrared heater heats the object to be heated with infrared light. The second air circulation unit circulates the air in the second heat insulating structure. Thus, since the first heat insulating structure and the second heat insulating structure are formed as an integral structure, the structure of the reflow furnace can be simplified and the cost can be reduced. Since the air circulation in the first heat insulation structure is performed by the first air circulation unit and the air circulation in the second heat insulation structure is performed by the second air circulation unit, the air in the first heat insulation structure and the second heat insulation structure is air-cooled. The circulation structure can be simplified, and the structure can be simplified and the cost can be reduced.

According to a seventh aspect of the present invention, in the heating method using the reflow furnace according to the sixth aspect, the target temperature of the first air heater is set within the first heat insulation structure during a temperature rising section of the object to be heated. The heating is performed by the hot air and the infrared rays by the first infrared heater, and in the temperature holding section of the object to be heated, the heating is performed by the hot air at the target temperature by the first air heater.
According to the seventh aspect, in the temperature rising section in the first heat insulation structure,
The temperature of the object to be heated is increased by heating with hot air at a target temperature by the air heater and infrared light by the first infrared heater. On the other hand, in the temperature holding section in the first heat insulating structure, heating is performed by hot air of the target temperature by the first air heater. Therefore, in the heating section, the object to be heated, such as a component or a printed circuit board, can be heated more uniformly because of the combined use of infrared rays and hot air at the target temperature. In the temperature holding section, the temperature is held by the convection of the hot air at the target temperature, so that the temperature of the object to be heated can be kept constant.

According to an eighth aspect of the present invention, in the heating method using the reflow furnace according to the seventh aspect, in the second heat insulating structure, the target temperature of the second air heater is set in a temperature rising section of the object to be heated. The heating is performed by the hot air and the infrared rays by the second infrared heater, and in the temperature holding section of the object to be heated, the heating is performed by the hot air at the target temperature by the second air heater.
According to the eighth aspect, in the temperature rising section in the second heat-insulating structure, the second
Heating is performed by hot air at a target temperature by an air heater and infrared light by a second infrared heater. On the other hand, in the temperature holding section in the second heat insulating structure, heating is performed by hot air of the target temperature by the second air heater. Accordingly, in the heating section, the main heating of the object to be heated can be performed uniformly because of the combined heating of the infrared rays and the hot air at the target temperature. In the temperature holding section, since the heating is performed by the convection of the hot air at the target temperature, the temperature of the main heated object can be kept constant.

[0016]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 is a sectional view showing a preferred embodiment of the reflow furnace of the present invention, and FIG. 2 is a sectional view taken along line E-E of the reflow furnace of FIG. FIG. 3 shows an example of a temperature profile, and FIGS. 1 and 2 are configured to obtain this temperature profile. The temperature profile is measured for reflow furnace conditions and temperature control in mass production.A temperature sensor such as a thermocouple is attached to the same board as the printed circuit board to be produced.
The substrate is placed on a conveyor of a reflow furnace and measured when passing through the reflow furnace, and indicates a temperature that changes with time. The temperature profile in FIG. 3 is required when, for example, a lead-free solder is used as the solder to be used. Needless to say, the required temperature profile differs depending on the type of lead-free solder, but here, for simplification of description, the description will be made based on one general example.

First, an example of the temperature profile shown in FIG. 3 will be described. In the temperature profile of FIG. 3, the vertical axis represents temperature, and the horizontal axis represents time. The vertical axis shows the preheating temperature (preheating temperature) T1 and the reflow temperature (main heating temperature) T2. On the time axis, a preheating section (preheating section) PH and a reflow section RF are shown. The preheating section PH has a heating section A and a temperature holding section B. Similarly, the reflow section RF has a temperature rising section C and a temperature holding section D. The preheat temperature T1 is, for example, about 170 ° C.
And the time of the temperature holding section B is about 90 seconds. The reflow temperature T2 is, for example, about 240 ° C., and the time of the temperature holding section D is about 20 seconds. The time of the heating section A is about 50 seconds, and the time of the heating section C is about 30 seconds.

Temperature holding section B in preheat section PH
Therefore, it is important that the temperature of the entire printed circuit board, which is the object to be heated, is as uniform as possible at the preheating temperature T1 at the time of moving to the heating section C of the reflow section RF. FIG. 4 and FIG.
1 shows an example of a temperature rise for a component P2 that is difficult to warm up. 4 and FIG. 5, the more uniform the temperature of the printed circuit board in the temperature holding section B in FIG. 3 is, the smaller the variation in the soldering temperature is, as in FIG. 5 than in FIG. As a result, the soldering quality of the printed circuit board becomes stable. In order to realize this, the preheating temperature T in the temperature holding section B of the preheating section PH is required.
It is most effective to blow hot air at a temperature of 1 onto the printed circuit board. If an infrared heater is used in the temperature holding section B, a temperature difference occurs in the printed circuit board due to a difference in infrared absorptivity of each component on the printed circuit board, and the printed circuit board and components cannot be brought to a uniform temperature.

On the other hand, in the heating section A of the preheating section PH shown in FIG. 3, the printed board at room temperature, which has been introduced from the outside, must be efficiently heated to the preheating temperature T1. It is effective to use an infrared heater which can be used. However, if the temperature of the printed circuit board is raised by using only the infrared heater, the parts P1 and the parts P2 that are easily warmed up and the parts P2 that are hard to warmed up as shown in FIG. In this case, a large temperature difference occurs. At this time, when hot air of the preheat temperature T1 is blown onto the printed circuit board, the component P2 having a lower temperature than the preheat temperature T1 is selectively heated as shown in FIG. To prevent heat from being overheated by cooling. Thus, as shown in FIG. 7, it is possible to minimize the variation in temperature between the component P1 that easily warms up and the component P2 that hardly warms up.

FIG. 1 is a sectional view showing a preferred embodiment of the reflow furnace according to the present invention as described above. The reflow furnace 10 includes a heat insulating structure 11 and a conveyor 10.
Two. The heat insulating structure 11 integrally forms a preheating portion (also referred to as a preheating portion or a preheating zone) PH and a reflow portion (also referred to as a main heating portion, a soldering portion, or a main heating zone) RF. ing.
The first heat insulating structure 12 and the second heat insulating structure 14 are integrated to form the heat insulating structure 11. The first heat insulating structure 12 and the second heat insulating structure 14 have an upper heat insulating part 20 and a lower heat insulating part 21. The first heat insulating structure 12 is formed in a state where the preheat portion PH is insulated from the outside. The preheat portion PH is formed by being thermally insulated from the outside in order to preheat the printed circuit board 8 so as not to give a thermal shock to the object to be heated, for example, the printed circuit board 8.

The second heat-insulating structure 14 forms a main heating zone in which the printed circuit board 8 is fully heated while being insulated from the outside. A substrate inlet 31 is formed in front of the first heat insulating structure 12, and a substrate outlet 3 is formed in the rear of the second heat insulating structure 14.
2 are formed. An opening 18 is formed in the partition 16 of the first heat insulating structure 12 and the second heat insulating structure 14. The conveyor 102 is a printed circuit board 8 which is an object to be heated.
Is conveyed in the F direction, and the conveyor 102 receives the F through the board inlet 31, the opening 18 and the board outlet 32.
Direction. The first heat insulating structure 12 and the second heat insulating structure 14 of the heat insulating structure 11 are made of, for example, calcium silicate, ceramic fiber (alumina or the like), glass fiber, or the like.

Next, the elements of the first heat insulating structure 12 and the elements of the second heat insulating structure 14 will be sequentially described. In the first heat insulating structure 12, a first air circulation unit 40, a first air heater 50, first infrared heaters 60A and 60B and the like are accommodated. The first air circulation unit 40 includes a fan 4 for hot air circulation (also referred to as hot air circulation).
3, a motor 44, a rectifying plate 45, a nozzle plate 46, a temperature sensor 47, and the like. The motor 44 is provided on the upper heat insulating unit 20, and when the fan 43 is rotated by the operation of the motor 44, the hot air (also referred to as hot air) W generates the first heat insulating structure 12 as indicated by a broken line arrow. Circulate in

The rectifying plate 45 of FIG. 1 is formed over the entire length of the temperature raising section A and the temperature holding section B, and the rectifying plate 45 includes a first air heater 50 and a first infrared heater 60A.
It is located between. The current plate 45 has a mesh shape or a plate shape having a large number of holes.
By passing through 5, the nonuniform hot air W disturbed by the fan 43 is converted into a stable and uniform flow. The nozzle plate 46 is located in the temperature holding section B, and is disposed below the current plate 45. Nozzle plate 46
Has a plurality of nozzles 46 </ b> A and plays a role of directly blowing the hot air W <b> 1 that has passed through the rectifying plate 45 onto the printed circuit board 8 on the conveyor 102. The hot air W generated by the rotation of the fan 43 passes between the straightening plate 45, the nozzle plate 46, and the side wall 20A of the upper heat insulating portion 20 shown in FIG. 2, and circulates as hot air W1 to the fan 43 side. I have. The temperature sensor 47 measures the temperature of the hot air passing through the rectifying plate 45 and supplies a temperature signal of the hot air W to the control unit 100.

The first air heater 50 includes a fan 43
And the rectifying plate 45 so that they can be commonly used across the temperature raising section A and the temperature holding section B.
It is arranged in the direction. The first air heater 50 is
This is a heater having fins 50 </ b> A, and is arranged so that the airflow of the hot air W generated by the hot air circulation fan 43 is applied. The operation of the first air heater 50 is controlled by a command from the control unit 100, and the operation of the motor 44 is also controlled by a command from the control unit 100.

The first infrared heaters 60A and 60B of FIG.
Are disposed in the first heat insulating structure 12, for example. The three first infrared heaters 60 </ b> A are located above the conveyor 102 and at the same height as the nozzle plate 46. The three first infrared heaters 60B are located on the lower side corresponding to the first infrared heater 60A, and are located on the lower side of the conveyor 102.
The first infrared heaters 60A and 60B generate infrared rays and heat the printed circuit board 8 when energized by a command from the control unit 100. The first infrared heater 60A,
60B is located only in the heating section A.

A hot air passage 61 is provided between the upper first infrared heater 60A and the wall 12C of the first heat insulating structure 12.
Are formed. The hot air heated by the first air heater 50 passes through the hot air passage 61 and is blown onto the printed circuit board 8 on the conveyor 102. The hot air is denoted by W1, and the hot air W1 is supplied to the conveyor 1 in the same manner as the hot air W1 that has passed through the nozzle 46A of the nozzle plate 46.
02 is directly sprayed on the printed circuit board 8. When the temperature sensor 47 detects the temperature of the hot air, the controller 100 controls the amount of heat generated by the first air heater 50 to control the temperature of the hot air W. In addition,
The six first infrared heaters 60A and 60B arranged in the temperature rising section A of the first heat insulating structure 12 use the same type of infrared heater in the illustrated embodiment in order to obtain a cost advantage by mass production effect. are doing.

Next, the components in the second heat insulating structure 14 of FIG. 1 will be described. In the second heat insulating structure 14, the second
The air circulation unit 140, the second air heater 150, the second
Infrared heaters 160A, 160B and the like are accommodated. The second air circulation unit 140 is provided with a fan 14 for hot air circulation.
3, motor 144, current plate 145, nozzle plate 14
6, a temperature sensor 147 and the like. Motor 144
Are provided on the upper heat insulating portion 20, and when the fan 143 is rotated by the operation of the motor 144, the hot air (also referred to as hot air) W is generated in the second heat insulating structure portion 14 as indicated by a broken line arrow. Circulate.

The rectifying plate 145 of FIG. 1 is formed over the entire length of the temperature raising section C and the temperature holding section D.
5 is located between the second air heater 150 and the second infrared heater 160A. The current plate 145 has a mesh shape or a plate shape having a large number of holes.
Of the hot air W having a non-uniform flow disturbed by the fan 43 is converted into a stable and uniform flow. The nozzle plate 146 is located in the temperature holding section D, and is disposed below the current plate 145. The nozzle plate 146 has a plurality of nozzles 146 </ b> A, and plays a role of directly blowing hot air that has passed through the current plate 145 onto the printed circuit board 8 on the conveyor 102. Fan 43
The hot air W generated by the rotation of the gas passes between the current plate 145, the nozzle plate 146, and the side wall of the upper heat insulating portion 20, and
The hot air W1 is circulated to the fan 143 side. The temperature sensor 147 measures the temperature of the hot air that has passed through the current plate 145, and sends the hot air W
Supply a temperature signal.

The second air heater 150 is connected to the fan 1
43 and the current plate 145. The second air heater 150 is a heater having fins 150A, and the hot air W generated by the fan 143 for circulating hot air.
It is arranged so that the air current may hit. The operation of the first air heater 50 is controlled by a command from the control unit 100, and the operation of the motor 44 is also controlled by a command from the control unit 100.

The second infrared heaters 160A and 160A of FIG.
For example, a total of four OBs are arranged in the second heat insulating structure 14. The two second infrared heaters 160A are:
It is located above the conveyor 102 and at the same height as the nozzle plate 146. The two second infrared heaters 160B are located on the lower side corresponding to the first infrared heater 160A, and are located on the lower side of the conveyor 102. Second infrared heaters 160A and 160B
Generates infrared rays and heats the printed circuit board 8 when energized by a command from the control unit 100. The first infrared heaters 60A and 60B are located only in the temperature rising section C.

A hot air passage is formed between the upper second infrared heater 160A and the wall of the second heat insulating structure 14. The hot air heated by the second air heater 150 passes through a hot air passage and is blown onto the printed circuit board 8 on the conveyor 102. The hot air is indicated by W1, and the hot air W1 is the nozzle 1 of the nozzle plate 146.
Conveyor 102 in the same manner as hot air W1 passing through 46A
Is directly sprayed on the printed circuit board 8 above. When the temperature sensor 147 detects the temperature of the hot air, the control unit 100 controls the amount of heat generated by the second air heater 150 to control the temperature of the hot air W.

Incidentally, the four first infrared heaters 160A, 160A, 1A arranged in the temperature rising section C of the second heat insulating structure portion 14.
60B is the same type in the illustrated embodiment, and 60A, 60A
OB uses the same type of infrared heater. In addition, the conveyor 102 in FIG. 1 conveys the printed board 8 to be heated from the board inlet 31 to the board outlet 32 through the opening 18 at a constant speed. As described above, the elements of the preheat portion PH and the reflow portion RF in FIG. 1 are basically the same, the first heat insulating structure portion 12 forms one box, and the second heat insulating structure portion 14 forms another box. Make up the box. The heating section A and the temperature holding section B of the preheating section PH are constituted by one first heat insulating structure section 12, and the heating section C and the temperature holding section D of the reflow section RF are constituted by the second heat insulating structure section 14. are doing.

In the temperature rising section A and the temperature holding section B in the first heat insulating structure section 12, a single first air circulation section 40 is used in common. Similarly, the temperature rising section C and the temperature holding section D in the second heat insulating structure section 14 are shared by one second air circulation section 140. That is, in the temperature rising section A and the temperature holding section B, the hot air of the preheat temperature T1 is collectively controlled and shared. Similarly, in the temperature rising section C and the temperature holding section D, the hot air at the reflow temperature T2 is collectively controlled by the second air circulation unit 140 and shared. Thus, the structure is simple and the cost can be reduced.

By the way, in the heating section A shown in FIG.
The surface temperature of the infrared heater 60A is controlled to a temperature higher than a predetermined preheat temperature T1 in order to generate a required amount of infrared light. Here, if the hot air W receives excessive heat from the surface of the first infrared heater 60A, the hot air W remains at a temperature higher than the preheat temperature T1, which is a problem. As a method for avoiding such a problem, the first infrared heater 60A generates infrared rays with respect to the printed circuit board 8 by using an infrared heater 60A.
Covering all or part of the part except for the surface with a heat insulating material. By covering a part or the entirety of the first infrared heater 60A with the heat insulating material in this manner, the amount of heat transferred from the infrared heater 60A to the hot air W1 is appropriately suppressed,
The temperature of the hot air W1 passing through the hot air passage 61 is the preheat temperature T
A temperature higher than 1 can be prevented.

FIG. 8 shows a configuration example of the first infrared heater 60A having such a function. The first infrared heater 60A has a structure in which an aluminum plate 70, a high-infrared radiation treated surface portion 71, a heater portion 72, and a heat insulating material 73 are laminated. A temperature sensor 74 is attached to the high-infrared radiation processing surface 71. The temperature sensor 74 is a sensor for controlling the temperature of the first infrared heater 60A, and the temperature detected by the temperature sensor 74 is sent to the control unit 100 of FIG. 1 as temperature information. The control unit 100 controls the amount of power to the first infrared heater 60A based on the temperature information from the temperature sensor 74. As the structure of the first infrared heater 60A, the same structure can be adopted for the second infrared heater 160A provided in the temperature rising section C of the reflow section RF in FIG. The temperature sensor 74 shown in FIG.
The temperature sensors 47 and 147 in FIG. 1 can use, for example, thermocouples.

Next, a heating method for heating the printed circuit board 8 by the reflow furnace 10 shown in FIG. 1 will be described. The printed circuit board 8 is placed on the conveyor 102 and the conveyor 10
By the operation of 2, the printed circuit board 8 is introduced from the board entrance 31 into the preheating section PH. In the heating section A, hot air (also referred to as hot air) W1 is directly blown onto the printed circuit board 8. That is, the fan 4 of the first air circulation unit 40
3 rotates, the air is heated by the first air heater 50 to become hot air W, passes through the rectifying plate 45, and is rectified, and then the hot air passage 61 of the first infrared heater 60A.
The hot air W1 is blown directly onto the printed circuit board 8 by passing through. Simultaneously with the blowing of the hot air, the first infrared heaters 60A and 60B heat the printed circuit board 8 by infrared rays.

By doing so, the printed circuit board 8 at room temperature can be efficiently heated by the first infrared heaters 60A and 60B. However, with the first infrared heater alone, a temperature difference may occur in the printed circuit board 8 because the infrared ray absorption rate and the heat capacity differ depending on the type of components mounted on the printed circuit board 8. In order to prevent the occurrence of this temperature difference, hot air W1 having a preheat temperature T1 is blown onto the substrate to selectively heat components having a temperature lower than the preheat temperature T1 and components having a temperature exceeding the preheat temperature T1. In order to prevent overheating, it cools and removes heat. In this way, it is possible to minimize the variation in the temperature of the printed circuit board 8 and efficiently heat the printed circuit board.

Next, when the conveyor 102 transports the printed circuit board 8 to the temperature holding section B, only the hot air W1 is blown to the printed circuit board 8 through the nozzle plate 46. In the temperature holding section B, it is important to make the entire temperature of the printed circuit board 8 as uniform as possible and to maintain the preheat temperature T1. The more uniform the temperature in the printed circuit board 8, the more the variation in the soldering temperature is reduced and the more stable the soldering quality. In order to make the temperature of the entire printed circuit board uniform, it is most effective to blow only the hot air W1 at the preheat temperature T1 onto the printed circuit board 8. If an infrared heater is used in the temperature holding section B, a difference in the infrared absorptivity of components causes a temperature difference on the printed circuit board, which is not preferable.

As described above, after the printed circuit board 8 has passed the temperature rising section A and the temperature holding section B of the preheating section PH, it enters the temperature rising section C of the reflow section RF. Since the printed circuit board 8 has to be heated from the preheat temperature T1 to the reflow temperature T2 in the temperature rising section C, the second infrared heater 160 that can be efficiently heated is used.
A and 160B are effective. However, with the second infrared heaters 160A and 160B alone, a temperature difference occurs in the printed circuit board 8 due to a difference in infrared absorptance and heat capacity depending on the type of components of the printed circuit board 8. When the hot air of the reflow temperature T2 is blown to the printed circuit board 8 when heating with the second infrared heater, components having a lower temperature than the reflow temperature T2 are selectively heated, and the temperature of the component exceeding the reflow temperature T2 is increased. The parts are cooled and deprived of heat to prevent overheating. In this way, it is possible to minimize variations in the temperature of the printed circuit board 8 in the temperature rising section C.

When the printed circuit board 8 further proceeds to the temperature holding section D, the printed circuit board 8 is blown with only the hot air W1. In the temperature holding section D, it is important to make the temperature of the printed circuit board 8 uniform to the reflow temperature T2, and the more uniform the temperature of the printed circuit board is, the smaller the variation of the soldering temperature is and the more stable the soldering quality is. I do. As a method for making the temperature of the printed circuit board uniform, it is most effective to blow the hot air W1 at the reflow temperature T2 directly onto the printed circuit board 8 in the temperature holding section D.
If an infrared heater is used in the temperature holding section D, a temperature difference may occur due to a difference in infrared absorptivity depending on the type of components of the printed circuit board 8, which is not preferable.

In the embodiment of the present invention, the preheating section
Each of the reflow sections is a single heat-insulating box, and a total of two connected heat-insulating boxes. Heating of the preheating section and the reflow section in the temperature rising section is performed by hot air (warm air) of the infrared ray and the target temperature, respectively, and heat retention in the temperature holding section is performed by hot air, so that high performance and low price can be realized. .

In the heating section, the components and the printed circuit board can be more uniformly heated because of the combined use of the infrared rays and the hot air having the target temperature. In the temperature holding section, since the hot air having the target temperature is convected, the temperature of the printed circuit board and components can be kept constant. The entire structure of the reflow furnace 10 includes two parts, a preheat part PH and a reflow part RF.
Only one air circulating unit and only two air circulating units, enabling significant cost reduction.

Incidentally, the present invention is not limited to the above-described embodiment, and various modifications are possible. The number of the first infrared heaters in the heating section in FIG. 1 is not limited to six, but may be four or eight or more. The second infrared heater 160A in the heating section C in FIG.
The number of 160B is not limited to four, but may be six or more. If the first infrared heater and the second infrared heater are configured such that the hot air passage 61 or 161 can be secured and the hot air can pass through, the first infrared heater and the second infrared heater are each one. No problem.

In the embodiment shown in FIG. 1, the hot air is applied to the printed circuit board 8 from the top downward, but it is also possible to simultaneously apply the hot air not only from the top downward but also from the bottom upward. When the lead-containing solder is used for the printed circuit board 8 instead of the lead-free solder, the reflow portion RF shown in FIG.
Can be dealt with by eliminating the structural portion of the temperature holding section D. The object to be heated is not limited to the printed circuit board 8 but may be of another type, for example, annealing of various components or materials (stabilizing the internal structure by heat treatment), painting or drying of a solvent. .

[0046]

As described above, according to the present invention,
The structure is simple and the cost can be reduced. The object to be heated can be more uniformly heated in the temperature rising section of the object to be heated, and the temperature of the object to be heated can be kept constant in the temperature holding section.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a preferred embodiment of a reflow furnace of the present invention.

FIG. 2 is a cross-sectional view of the reflow furnace of FIG. 1 taken along line EE.

FIG. 3 is a view showing an example of a temperature profile of the reflow furnace of FIG. 1;

FIG. 4 is a diagram illustrating an example of a temperature difference between a warm-up component P1 and a hard-warming component P2 when shifting from a temperature holding section B to a heating section C shown as a conventional comparative example.

FIG. 5 is a diagram showing a temperature holding section B to a heating section C in FIG. 3 of the present invention.
FIG. 9 is a diagram showing an example in which the temperature difference between a component P1 that is easy to warm up and a component P2 that is difficult to warm up when the process proceeds to FIG.

FIG. 6 shows a part P1 that easily warms up and a part P that hardly warms up in a heating section A in a conventional preheating unit.
The figure which shows the temperature difference between two.

FIG. 7 is a diagram showing a state in which a temperature difference between a component P1 that easily warms up and a component P2 that hardly warms up in a temperature rising section A of FIG. 3 of the present invention is small.

FIG. 8 is a diagram showing a structural example of a first infrared heater and the like.

FIG. 9 is a diagram showing an example of a conventional temperature profile.

FIG. 10 is a diagram showing a conventional reflow furnace for realizing the temperature profile of FIG. 9;

FIG. 11 is a diagram showing another conventional temperature profile.

FIG. 12 is a diagram showing a conventional reflow furnace for realizing the conventional temperature profile of FIG. 11;

[Explanation of symbols]

Reference numeral 8: printed circuit board (object to be heated), 10: reflow furnace, 11: heat insulating structure, 12: first heat insulating structure, 14: second heat insulating structure, 40 ... -1st air circulation part, 50 ... 1st air heater, 60A, 60
B: first infrared heater, 61: hot air passage, 1
02: conveyor, 140: second air circulation unit, 1
50: second air heater, 160A, 160B
············································································
-Temperature rise section of reflow section, D: temperature holding section of reflow section, PH: preheat section (preheating section, preheating zone), RF: reflow section (soldering section, main heating zone)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 101: 42 B23K 101: 42

Claims (8)

[Claims] 1. A first heat insulating structure, comprising: a reflow furnace for heating an object to be heated when the object to be heated is conveyed; A first air heating heater arranged in the first heat insulating structure to heat the object to be heated with hot air; and a first air heater arranged in the first heat insulating structure to heat the object to be heated by infrared rays A first infrared heater, a first air circulating unit disposed in the first heat insulating structure and circulating air in the first heat insulating structure, and a main heating zone for main heating the preheated object to be heated Is a second heat insulating structure formed by insulating from outside,
A second heat insulating structure formed integrally with the first heat insulating structure; and a second air heater disposed in the second heat insulating structure and heating the object to be heated with hot air. A second infrared heater arranged in the second heat insulating structure to heat the object to be heated with infrared light; and a second infrared heater arranged in the second heat insulating structure to circulate the air in the second heat insulating structure. And a second air circulation unit. 2. In the first heat-insulating structure, the hot air at a target temperature by the first air heater and a heating section of the object to be heated by the first infrared heater with the infrared rays; 2. The reflow furnace according to claim 1, further comprising a temperature holding section for heating the object to be heated, the section being heated by the hot air at a target temperature by the first air heater. 3. 3. In the second heat insulating structure, the hot air having a target temperature of the second air heater and a heating section of the object to be heated in which the infrared light is heated by the second infrared heater; 3. The reflow furnace according to claim 2, further comprising: a temperature holding section for heating the object to be heated, the section being heated by the hot air at a target temperature by the second air heater. 4. 4. The first infrared heater and the second infrared heater have a temperature sensor disposed on one surface side for generating infrared rays and a heat insulating material disposed on the other surface side for preventing generation of infrared rays. The reflow furnace according to claim 1. 5. A hot-air passage for blowing hot air onto the object to be heated by dividing the first infrared heater and the second infrared heater into a plurality in the direction in which the object to be heated is conveyed. The reflow furnace according to claim 1, comprising: 6. A heating method using a reflow furnace for heating the object to be heated when the object to be heated is conveyed, wherein a preheating zone for preheating the object to be heated is formed by being insulated from the outside. In the first heat insulating structure, the first air circulating unit circulates the air in the first heat insulating structure, and
Heating the object to be heated with hot air by an air heater,
A first infrared heater heats the object to be heated by infrared rays, and a main heating zone for main heating of the preheated object to be heated is insulated from the outside, and is integrally formed with the first heat insulating structure. In the second heat insulating structure formed as a structure, a second air circulation unit circulates the air in the second heat insulating structure, and heats the object to be heated with hot air by a second air heater. And heating the object to be heated with infrared rays by a second infrared heater. 7. In the first heat-insulating structure, heating is performed by the hot air at a target temperature by the first air heater and the infrared light by the first infrared heater in a heating section of the object to be heated. The heating method according to claim 6, wherein in the temperature holding section of the object to be heated, heating is performed by the hot air having a target temperature by the first air heater. 8. In the second heat-insulating structure, in a heating section of the object to be heated, heating is performed by the hot air having a target temperature by the second air heater and the infrared light by the second infrared heater. The heating method using a reflow furnace according to claim 7, wherein in the temperature holding section of the object to be heated, heating is performed by the hot air having a target temperature by the second air heater.