JP2502827B2 - Reflow soldering equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component such as a chip component or a flat package having a high heat resistance temperature (hereinafter referred to as a mounting component) and an electronic component having a lead wire having a low heat resistance temperature. The present invention relates to a reflow soldering device capable of soldering a board in a hot atmosphere.

[0002]

2. Description of the Related Art Conventionally, a printed circuit board on which mounting components having a relatively high heat resistance is mounted is soldered by a reflow soldering apparatus in a high temperature atmosphere uniformly maintained at a temperature of about 210 to 250 ° C. Was being done.

Further, in the case of a mixed mounting board of a mounting component having a high heat resistance temperature and an electronic component with a lead wire having a low heat resistance temperature,
After mounting the mounted components on the printed circuit board coated with solder paste, soldering is performed with a reflow soldering device, then the electronic components with lead wires are mounted on the printed circuit board, and then flux coating, After preheating, soldering was performed in a solder bath, and further cleaning was performed with a Freon (trade name of DuPont) solution or the like.

[0004]

By the way, with the diversification of surface mounting technology and cost reduction of printed circuit boards,
Among the electronic components with lead wires that have been used in the solder bath up to now, electronic components with a low heat resistance of about 120 ° C. have not been soldered by the reflow soldering device.

For this reason, in the reflow soldering apparatus currently used, the heating chamber is made uniform at a temperature of 210 to 250 ° C., so that it has a lead wire having a low heat resistance of about 120 ° C. There is a problem that it is not suitable for soldering electronic components.

Further, in order to solder an electronic component with a lead wire in a solder bath, a flux coating device, a preheating device and a cleaning device are required. Particularly, the cleaning device is Freon (trade name of DuPont). ) Since a liquid is used, if part of the vapor is discharged to the outside, the cleaning liquid is wasted, which not only increases the cost of the product but also deteriorates the working environment and causes pollution. There was a problem.

Therefore, the present inventor has proposed a reflow soldering method for a printed circuit board and an apparatus therefor (see Japanese Patent Application No. 2-194722) in order to solve the above conventional problems. That is, as a method for reflow soldering a printed circuit board, the printed circuit board is continuously transferred to a transfer conveyor of a reflow soldering device in which a preheating chamber and a reflow chamber are sequentially provided so as to be in close contact with each other, and preheating is performed. The upper part of the chamber and the upper part of the reflow chamber are heated to a low temperature, and the lower part of the preheating chamber and the lower part of the reflow chamber are heated to a high temperature to melt the solder paste on the back surface of the printed circuit board. After that, it is solidified and the electronic component is soldered to the printed circuit board.

As a reflow soldering device,
Keep the upper side of the preheating chamber and the upper side of the reflow chamber at a low temperature, and keep the lower side of the preheating chamber and the lower side of the reflow chamber at a high temperature to create a temperature difference and solder the back side of the printed circuit board. In order to carry out, the hot atmosphere heated at the lower side of the reflow chamber flows upward between the side walls of the preheating chamber and the reflow chamber and the chain guide having the guide rails of the respective transport chains. A shield plate is provided to prevent this.

As described above, after the solder paste is applied to the through hole portion on the back surface of the printed circuit board, it is inverted to mount the mounted component and to lead the lead wire of the electronic component with the lead wire through the hole. Then, reflow soldering is performed on the back surface of the printed circuit board.

Further, a shielding plate is provided between the side wall of the preheating chamber, the side wall of the reflow chamber and the chain guide having the guide rail of the transfer chain, whereby the lower side of the preheating chamber and the lower side of the reflow chamber. The side heat atmosphere is prevented from entering the upper side of the preheating chamber and the upper side of the reflow chamber.

By the way, also in the above-mentioned conventional method and apparatus for soldering a printed circuit board, the printed circuit board at the front stage and the printed circuit board at the rear stage in the traveling direction of the printed circuit board must be sequentially brought into close contact with each other on the transport conveyor to be transported. Therefore, if it takes time to apply the solder paste to the printed circuit board or temporarily attach the mounted components and electronic components to the printed circuit board, the placement of the printed circuit board on the transfer conveyor is interrupted, and Since there is a gap between the printed circuit board in the latter stage and the low-temperature thermal atmosphere on the upper side of each of the preheating chamber and the reflow chamber and the high-temperature thermal atmosphere on the lower side of the preheating chamber and the lower side of the preheating chamber and the lower temperature side, the original temperature difference is restored. There is a problem that it is difficult to recover to a hot atmosphere having Therefore , a heat shield is provided between the printed circuit boards .
It is necessary to place a dummy board between the printed boards.
There is a problem that it is difficult to carry out the missing conveyance . "

The present invention has been made in order to solve the above-mentioned problems, and even in intermittent transfer in which the printed circuit boards are transferred with a space between them, the upper portions of the preheating chamber and the reflow chamber can be moved to the upper side. An object of the present invention is to obtain a reflow soldering device for a printed circuit board, which can hold a lower side in a high temperature hot atmosphere in a low temperature hot atmosphere.

[0013]

A reflow soldering apparatus according to the present invention has a preheating chamber and an upper side of the reflow chamber.
A preheating chamber is provided along with each external air introduction fan.
And the side wall of the reflow chamber and the chain guide of the transfer chain
A shielding plate is provided between them.

[0014]

In the present invention, the lower side of the preheating chamber and the lower side of the reflow chamber are heated to a higher temperature atmosphere than the upper side of the preheating chamber and the upper side of the reflow chamber, and the upper side of the preheating chamber. And blowing the outside air downward from the outside air introducing fan provided on the upper side of the reflow chamber and on the upper side of the reflow chamber, the thermal atmosphere of the lower side of the preheating chamber and the lower side of the reflow chamber is prevented from flowing to the upper side.

[0015]

1 and 2 show an embodiment of the present invention. FIG. 1 is a side sectional view, FIG. 2 is an enlarged side sectional view showing an essential portion of FIG. 1, and FIG. FIG. 4 is an enlarged side sectional view showing the shape of the printed circuit board in FIG. 1, and FIG. 4 is an enlarged front sectional view showing the transport conveyor in FIG.

In these figures, 1 is a printed circuit board, 1a is a main surface, and 1b is a back surface. Reference numeral 2 is a chip component having a high heat resistant temperature as a mounting component, 3 is an electronic component having a low heat resistant temperature, 4 is a lead wire of the electronic component 3, 5 is a printed circuit, and 6 is a lead wire 4 inserted therein. And 7 is a solder paste. Further, in FIG. 4, reference numeral 11 denotes a transport chain as an example of a transport conveyor that transports the printed circuit board 1. Reference numeral 12 is a mounting roller on which the printed circuit board 1 is mounted, and 13 is a chain guide. Also,
1 and 2, reference numeral 21 denotes the entire reflow soldering apparatus, and reference numerals 22 and 23 denote primary spares for heating the printed circuit board 1 with air heated to a temperature lower than the melting point of the solder paste 7. The heating chamber and the secondary preheating chamber are provided at the rear and the front in the traveling direction of the printed circuit board 1 (direction of arrow A), and 22A and 23A denote the preheating chambers 22 and 22, respectively.
The upper side of 23, 22B and 23B are the preheating chambers 2
2, 23 is a lower side, 24 is a reflow chamber for soldering the printed circuit board 1, and 24A is the reflow chamber 24.
24B is the lower side of the reflow chamber 24,
Are formed on the side walls of the preheating chambers 22 and 23 and the reflow chamber 24 in parallel with the traveling direction of the printed circuit board 1 (direction of arrow A). 26 is a heater for heating air,
Seed heaters or far infrared heaters are used. Radiation heat 27 including far infrared rays generated from the heater 26 is used in each of the preheating chambers 22 and 23 and the reflow chamber 2.
A shield plate that shields the radiation inside 4 to prevent the traveling printed circuit board 1, chip component 2, and electronic component 3 from being heated by radiant heat. 28 is the chain
A shield plate that closes between the guide 13 and each side wall 25,
The hot air heated by the heaters 26 on the lower sides 22B, 23B, 24B of the preheating chambers 22, 23 and the reflow chamber 24 is prevented from flowing upward. 29 is a heating chamber formed by the shielding plate 27, and 30 is a blower fan for circulating the air heated in each heating chamber 29, and a multi-blade blower or the like is used. Although not shown, an air flow passage is formed from the heating chamber 29 to the inside of the blower fan 30. 31 is the blower fan 3
0 motors, 32 are upper sides 22A, 23A, 24A of the preheating chambers 22, 23 and the reflow chamber 24, respectively.
In order to keep the inside of the electronic component 3 at a temperature not higher than the heat resistant temperature, an outside air introduction port for introducing outside air at room temperature, 33 is the outside air introduction port 32
External air introduction fan, 34 is the preheating chambers 22, 23
And a blower port for blowing the air in the reflow chamber 24 toward the printed circuit board 1, 35 is an inlet port for circulating the air discharged from the blower port 34 to the heating chamber 29, and 36 is formed in each of the blower ports 34. The rectifying plate rectifies the turbulent air flow of the blower fan 30. Reference numeral 37 denotes the preheating chambers 22 and 23, and the upper portions 22A and 23 of the reflow chamber 24.
A punched steel plate provided below each straightening plate 36 of A and 24A, which is shown by broken lines in FIGS. 1 and 2, and has a large number of through holes (not shown) formed therein. 38 is the printed circuit board 1
Each preheating chamber 2 with a radiant heater that heats the back surface 1b of the
2, 23, lower side 22B, 23B, 2 of the reflow chamber 24
It is provided above each straightening plate 36 of 4B. 39 is an exhaust port, 40 is an exhaust fan, and 41 is a cooling fan that cools the heated printed circuit board 1.

In FIG. 1, each preheating chamber 22,
Upper side 22A of the 23, 23A and the lower side 22B, 23B and reflow - the upper side 24A of the chamber 24 and the lower side 24B transport chain - is disposed to face up and down around the emissions 11.

Next, the operation will be described. FIG. 5 (a)
(D) is a process drawing of soldering of the printed circuit board 1. First, in FIG. 5A, the printed circuit board 1 is turned upside down so that the main surface 1a is on the lower side and the back surface 1b is on the upper side. Then, a solder paste 7 is applied to a portion of the printed circuit 5 on which the chip component 2 is mounted and a portion of the through hole 6 into which the lead wire 4 of the electronic component 3 is inserted on the back surface 1b which is the upper side. . The solder paste 7 is applied by an injector (not shown) or by covering with a plate-shaped screen (not shown) having the same through holes as the printed circuit board 1.

Next, as shown in FIG. 5 (b), after mounting the chip component 2 on the solder paste 7, as shown in FIG. 5 (c), the printed circuit board 1 is inverted to expose the main surface 1a. After the upper side, the lead wire 4 of the electronic component 3 is inserted into the through hole 6, and the solder paste 7 is melted by the reflow soldering device 21 shown in FIG. ) Soldered as shown.

FIG. 6 is a characteristic diagram showing the relationship between the time t for transporting the printed circuit board 1 and the temperature T ° C. The broken lines indicate the upper side 22A, 23A of the preheating chambers 22 and 23 and the reflow chamber 24, respectively.
24A temperature characteristics, preheating chambers 22 and 23 and reflow
The solid line of the chamber 24 shows the temperature characteristics of the lower sides 22B, 23B, 24B. The time t1 to t2 indicates the time during which the printed circuit board 1 passes through the primary preheating chamber 22, the time t2 to t3, the secondary preheating chamber 23, and the time t3 to t4, the reflow chamber 24. .

In FIG. 6, time t1 is the time when heating is started, and indicates room temperature T1 = 20 ° C. Next, the heating is performed at times t1 to t2, and at times t2 to t3, the upper sides 22A and 23A of the preheating chambers 22 and 23 are driven by the outside air introduction fan 33 to send outside air from the outside air introduction port 32, respectively. Lower sides 22B and 23B of the preheating chambers 22 and 23
Electronic component 3 to suppress the rise of the heat atmosphere from
The temperature is maintained at a temperature of about T2 = 90 ° C., which is lower than or equal to the heat resistant temperature of
Also, the lower side 22B, 23B of each preheating chamber 22, 23
Is for preheating the printed circuit board 1 T4 = 150 ° C
Is heated to the next level. At time t3 t4, reflow - upper side 24A of the chamber 24, when feeding the outside air by driving the outside air introduction fan 33 from the outside air introduction port 32, pre
Introduction of outside air into the equipment heating chambers 22 and 23 and the reflow chamber 24
The amount of outside air blown by the fan 33 can be changed appropriately.
And, for example, the reflow chamber is more than the preheating chambers 22 and 23.
When the temperature of the lower side of the chamber 24 becomes higher, the reflow chamber
Since the temperature on the upper side of 24 also becomes correspondingly high,
The blowing amount of the outside air introduction fan 33 is set to the preheating chambers 22, 2
3 more than above, and above by the shielding plate 28
Together with the effect of preventing the hot air from flowing, the rising of the hot atmosphere from the lower side 24B of the reflow chamber 24 is suppressed and the maximum temperature is maintained at about T3 = 115 ° C. The lower side 24B of the reflow chamber 24 is heated to about T5 = 215 ° C, which is higher than the melting temperature (180 ° C) of the solder paste 7, so that the lead wire 4 of the chip component 2 and the electronic component 3 is soldered. Done. In addition, each preheating chamber 22, 23 and
When introducing outside air into the flow chamber 24, for example, in winter
When the outside air temperature is low, introduce an outside air temperature that is too low.
Then the temperature may become too low.
In this case, each preheating chamber 22, 23 and reflow chamber 24
By adjusting the amount of outside air blown onto each,
Since the temperature can be controlled, the amount of spray that matches the outside air temperature
Adjust to. Next, the printed circuit board 1 is taken out of the reflow soldering device 21 and cooled by the cooling fan 41 to complete soldering. It should be noted that the punched steel plate 37 is used for the upper side 2 of each of the preheating chambers 22 and 23 and the reflow chamber 24.
The near-infrared rays in 2A, 23A, 24A are prevented from being absorbed by the main surface 1a of the printed circuit board 1, and air is blown by each cold air fan 33 to the lower side of each of the preheating chambers 22, 23 and the reflow chamber 24. The hot air of 22B, 23B, and 24B is applied to the preheating chambers 22 and 23 and the upper side 22 of the reflow chamber 24.
It is prevented from flowing into the A, 23A, and 24A. Further, the inside of the lower side 24B of the reflow chamber 24 is heated by the hot air and the heater 3
It is heated by the near-infrared rays generated from No. 8.

[0022]

As described above, according to the present invention, outside air is blown downward to the upper side of the preheating chamber and the upper side of the reflow chamber so that the lower side of the preheating chamber and the lower side of the reflow chamber are blown. Each of the preheating chambers and reflow chambers is equipped with an outside air introduction fan that prevents the heated hot atmosphere from flowing upward.
Since the thermal atmosphere in the lower part of the chamber does not flow to the upper part, it is not necessary to closely convey the front and rear stages of the printed circuit board when transporting the printed circuit board, and therefore, the printed circuit board and the printed circuit board can be transferred between them. It becomes possible to open and place it on the transfer conveyor, preheating and each side of the reflow chamber
Guide rails for each transport chain on the wall and transport conveyor
If a shield plate is installed between the
Between the printed circuit boards during transport
In addition, there is no need to mount a dummy board for heat shielding.
This has the advantage that the number of steps for transferring the printed circuit board can be saved.
It Also, change the blowing amount of the outside air introduction fan.
Therefore, even if the outside air temperature changes, each
It is possible to control the atmosphere in the heating and reflow chambers.
It becomes Noh.

Further, even if a mixed board of a mounted component having a high heat resistance temperature and an electronic component with a lead wire having a low heat resistance temperature is soldered by a reflow soldering device, the electronic component having a low heat resistance temperature is not damaged by heat. Since it does not exist, there is an advantage that the soldering process can be simplified.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a side sectional view showing an enlarged main part of FIG.

FIG. 3 is an enlarged side sectional view showing the shape of the printed circuit board shown in FIG.

FIG. 4 is an enlarged side sectional view showing the shape of the transport chain of FIG.

FIG. 5 is a diagram showing a process of soldering a printed circuit board.

FIG. 6 is a characteristic diagram showing the relationship between the transport time of the printed circuit board and the temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 1a Main surface 1b Back surface 2 Chip component 3 Electronic component 4 Lead wire 5 Printed circuit 6 Through hole 7 Solder paste 11 Transport chain 21 Reflow soldering device 22 Primary preheating chamber 22A Upper side 22B Lower side 23 Secondary preheating chamber 23A Upper side 23B Lower side 24 Reflow chamber 24A Upper side 24B Lower side 30 Blower fan 32 Outside air inlet 33 Outside air inlet fan

Claims (1)

(57) [Claims] 1. A solder paste applied on a printed circuit board.
Conveying means for temporarily mounting mounted components on a strike, inserting lead wires of electronic components from the main surface of the printed circuit board into through holes formed in the printed circuit board, and conveying the temporarily adhered printed circuit board by a conveyor. And a reflow soldering device in which a preheating chamber for heating the printed circuit board and a reflow chamber for melting and soldering the solder paste are vertically opposed to each other around the transport conveyor. In the upper side of the preheating chamber and the upper side of the reflow chamber, the thermal atmosphere heated in the lower side of the preheating chamber and the lower side of the reflow chamber is blown upward by blowing outside air downward. Each has an outside air introduction fan to prevent the flow , and
Each side wall of the preheating chamber and the reflow chamber and the transfer conveyor
Chain guide with guide rails for each transport chain
And the hot atmosphere heated at the bottom of the reflow chamber
A reflow soldering device characterized in that a shielding plate is provided to prevent the flow toward one side .