JP2001352162A - Soldering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow soldering device capable of preventing solder from being molten again by decreasing the temperature of the component loading face of a circuit board while the circuit board passes through a jet solder tank. SOLUTION: An inert gas spraying pipe 12 equipped with plural nozzle holes is arranged at the upper part of a flow soldering device, and inert gas for cooling a board jetted from the spraying pipe is sprayed to the upper face of the circuit board 1 passing through the solder tank so that an electronic component 11 which is already loaded on the upper face of the circuit board can be cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering apparatus, and more particularly to a flow soldering apparatus for performing soldering from the back surface of a circuit board in an inert gas atmosphere.

[0002]

2. Description of the Related Art In a flow soldering apparatus, for example, as shown in a side sectional view of FIG. And the circuit board 1
After the flux is applied to the soldering surface (back surface) of the above, it is guided to the tunnel-shaped chamber 3. The inside of the chamber 3 separated from the external space is filled with an inert gas such as N 2 gas blown out from a pipe 6.

[0003] Inside the chamber, a preheater 5 for preheating the circuit board 1 is provided along the conveyor 2,
A solder bath 7 for jetting molten solder is arranged on the back surface of the circuit board 1. Since the ambient temperature of the solder bath 7 becomes high due to the heat of the jetted solder, the high-temperature N 2 gas is led to the cooling device 10 by the suction pipe 8, and the cooled N 2 gas is returned to the solder bath 7 again by the pipe 9. Thereby, the atmosphere of the solder bath is reduced to a constant temperature.
However, the circulation of the N2 gas alone does not sufficiently cool the atmosphere of the solder bath, and the solder of the mounted components (surface mounted components) already bonded on the surface side of the circuit board may be re-melted. There is.

As a technique for preventing such re-melting of the mounted mounting component, for example, (1) a method of performing flow soldering with a heat-dissipating block placed on a lead of a surface mounting component, or 2) A method is known in which a heat-resistant tape is attached to the back surface of the circuit board facing the surface-mounted component, so that high-temperature jet solder does not directly touch the circuit board on the surface-mounted component mounting portion. Also, Japanese Patent Application Laid-Open
In Japanese Patent Application Laid-Open No. 1-186707, in a reflow soldering apparatus in which cream solder previously applied to a predetermined portion of a circuit board is melted by hot air, cooling air is poured into a component mounting surface in order to avoid a rise in temperature of non-heat-resistant electrical components. Cooling means has been proposed in which the amount of cooling air taken in from the outside is adjusted according to the area of the opening.

[0005]

However, in the conventional method proposed for preventing the solder from re-melting the mounted components, various types of heat-dissipating blocks can be prepared according to the shape and arrangement of the mounted components. There is a problem that the cost of assembling the substrate is increased because the heat-resistant tape needs to be attached. In addition, the component cooling by the opening area control proposed in the reflow soldering apparatus is in principle the same as the cooling by the N2 gas circulation described in FIG.
It is not sufficient to prevent the solder from re-melting the mounted components that occur during the passage of the hot jet solder bath in the flow soldering apparatus.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flow soldering apparatus capable of cooling a component mounting surface of a circuit board passing through a solder bath in which molten solder is jetted and preventing solder remelting of the mounted components. Other objects of the invention are, for example,
Provided is a flow soldering apparatus that can effectively prevent re-melting of an already mounted component even when a solder amount and a heat capacity of a bonding portion with a circuit board are small, such as a narrow pitch lead component such as a 0.5 mm pitch QFP. It is in.

[0007]

In order to solve the above-mentioned problems, a flow soldering apparatus according to the present invention comprises an inert gas spray pipe having a plurality of nozzle holes above a solder bath for jetting molten solder. By disposing the substrate cooling inert gas injected from the spray pipe onto the upper surface of the circuit board passing through the solder bath, the electronic components already mounted on the upper surface of the circuit board are cooled. In addition, remelting of a soldered portion is prevented.

In a preferred embodiment of the present invention, the spray pipe has a double structure consisting of a center pipe and an outer pipe, and supplies an inert gas for cooling a substrate to the center pipe and cools the outer pipe. By flowing the medium, the temperature rise of the substrate cooling inert gas itself in the spray pipe is suppressed. In another embodiment of the present invention, the spray pipe is arranged perpendicular to the circuit board transport direction, and the spray pipe is moved in the circuit board transport direction as the circuit board moves in the solder bath area. By doing so, a specific area on the circuit board is continuously cooled by the inert gas for cooling the board which is jetted from the spray pipe during the soldering process.

Further, the flow soldering apparatus according to the present invention discharges a high-temperature inert gas in the vicinity of the solder bath to the outside of the chamber and returns the inert gas cooled by the cooling device to the inside of the chamber. Means for cooling a circuit board by injecting an inert gas from a spray pipe having a plurality of nozzle holes disposed above the solder bath. According to the above configuration, in a state where the temperature rise of the inert gas atmosphere near the solder bath is suppressed, the substrate cooling inert gas is blown from the spray pipe to the upper surface of the circuit board passing through the solder bath, The cooling effect of the circuit board is enhanced, and the re-melting of the soldered portion in the already mounted electronic component can be reliably prevented.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of a flow soldering apparatus according to the present invention. Here, the solder bath 7
Is shown in a cross-sectional view as viewed from the traveling direction of the circuit board 1.
The circuit board 1 is carried into the solder bath 7 with both ends sandwiched by the conveyor 2, and after the lower surface of the circuit board is in contact with the jet solder, the circuit board 1 is gradually raised and separated from the solder bath. Pass the solder bath in orbit. In this embodiment,
Above the solder bath 7, a cooling inert gas blowing pipe 12 having a number of nozzle holes in the width direction of the circuit board is arranged. An inert gas for cooling, for example, a normal temperature or a cooled low-temperature N 2 gas, is supplied from the outside of the chamber 3 to the spray pipe 12 through a supply pipe 13.

In the present invention, since the inert gas for cooling is jetted vigorously onto the upper surface of the circuit board 1 from the nozzle holes provided in the spray pipe 12, the ambient temperature inside the chamber and the flow The upper surface of the circuit board 1 heated by the heat can be forcibly cooled. Therefore, even if the electronic component 11 mounted on the upper surface of the circuit board 1 is a component having a small amount of solder and a small heat capacity, such as a narrow-pitch lead component, for example, a temperature at which the bonded solder portion does not re-melt. It becomes possible to cool effectively.

When a plurality of the spray pipes 12 are arranged, for example, above a solder bath, the circuit board passing through the solder bath is cooled by an inert gas for cooling sprayed from nozzle holes arranged two-dimensionally. The entire surface can be cooled. Therefore, regardless of the arrangement position of the already mounted components on the circuit board, it is possible to perform the flow soldering while avoiding the remelting of the bonded solder. In this case, if the spray pipe to be operated is selected according to the moving position of the circuit board, and only the spray pipe at the position facing the circuit board is controlled so as to inject the cooling inert gas, the spray pipe is sprayed. Also, disturbance of the molten solder due to the inert gas can be prevented.

FIG. 2 shows an embodiment of a flow soldering apparatus according to the present invention having a movable blowing pipe 12 which performs a cooling operation following a circuit board. Here, the solder bath 7 is shown in a cross-sectional view along the transport direction of the circuit board. In the drawing, reference numeral 17 denotes a sensor for detecting a board arranged at the entrance of the solder bath 7, 18 denotes a ball screw for moving the spray pipe 12 in the direction of transporting the circuit board, 19
Is an electromagnetic valve for selectively supplying a cooling gas to the gas supply pipe 13, 20 is a pulse motor for driving the ball screw 18, 21 is a detection signal of the circuit board 1 by a board detection sensor 17. 5 shows a sequence controller that starts a control sequence for cooling a substrate in response to the sequence controller.

When the circuit board 1 conveyed by the conveyor 2 reaches the entrance of the solder bath 7, the detection sensor 17 outputs a board detection signal. Sequence controller 21
Opens the electromagnetic valve 19 in response to the substrate detection signal. Thereby, the N2 gas for cooling is supplied to the supply pipe 13.
To the spray pipe 12. After receiving the board detection signal, the sequence controller 21
At a predetermined timing, the drive motor 20 of the ball screw 18 is operated to start a control operation for moving the spray pipe 12 in the substrate advancing direction. As a result, the spray pipe 12 moves at the same speed as the conveyor 2, and keeps injecting the cooling gas to a predetermined position on the upper surface of the circuit board while the circuit board passes the solder.

As shown in the figure, when the number of the blowing pipe 12 is one, the ball screw 18 is driven at the timing when the component to be cooled on the circuit board reaches the position of the blowing pipe.
A plurality of components to be cooled are distributed on the circuit board,
If it is difficult to cool all parts with one blowing pipe 12, a plurality of blowing pipes may be attached to the ball screw 18 and moved in synchronization with the circuit board. With the above configuration, it is possible to cool the already mounted components on the circuit board with a small number of spray pipes during the soldering of the electronic components. The sequence controller 21 closes the electromagnetic valve 19 when the circuit board 1 is transported to a position where cooling is not necessary after passing through the solder bath,
And the spray pipe 12 is returned to the entrance point of the solder bath 7.

FIG. 3 shows still another embodiment of the soldering apparatus according to the present invention provided with a spray pipe 12. In this embodiment, the blowing pipe 12 has a double structure so that the cooling medium flows through the outer pipe so that the temperature of the cooling N2 gas supplied to the blowing pipe 12 does not rise due to the heat in the chamber 3. It is characterized by cooling the spray pipe itself. That is, as shown in FIG. 4, for example, the spray pipe 12 of the present embodiment is provided with a center pipe 22 to which a spray gas for cooling the substrate is supplied and a cooling medium for cooling the center pipe 22. And an outer pipe 23 to be formed. The central pipe 22 has a plurality of nozzle holes along the axial direction, similarly to the cooling pipe 12 shown in FIG. 1, and the cooling gas ejected from each nozzle hole is
It is sprayed toward the solder bath through a hole or groove 24 formed in the bottom surface of the outer pipe.

One end of the outer pipe 23 is connected to the cooling medium supply pipe 14 and the other end is connected to the cooling medium recovery pipe 15.
It is connected to the. A low-temperature cooling medium, for example, a low-temperature oxygen gas is supplied from the supply pipe 14, and the cooling medium heated at the ambient temperature in the chamber 3 is discharged to the outside by the recovery pipe 15 and recovered in a medium cooling device or a heat exchanger. . The outer pipe may be supplied with another cooling medium other than oxygen, such as liquid nitrogen, water, or air. According to this embodiment, a low-temperature inert gas is injected from the nozzle holes of the central pipe 22 by supplying the substrate cooling inert gas to the low-temperature central pipe 22 forcibly cooled by the cooling medium. With this configuration, it is possible to effectively cool the components mounted on the circuit board in a high-temperature atmosphere.

FIG. 5 shows the spray pipe 12 having the double structure.
1 shows an example of the overall structure of a soldering apparatus provided with the above. The basic configuration of the soldering apparatus is the same as that of the conventional apparatus described with reference to FIG. 7, and in the case of the present invention, a conventional inert gas for cooling the high-temperature atmosphere gas in the chamber is provided near the solder bath 7. In addition to the circulating cooling mechanisms (8, 9, 10), the spray pipe 12, a pipe 13 for supplying an inert gas for cooling the substrate to the spray pipe 12, and the spray pipe 12 are cooled. Medium supply pipe 14 and a cooling medium recovery pipe 15 for recirculating the cooling medium recovered by the cooling medium recovery pipe 14 outside the soldering device and sending the cooling medium to the cooling medium supply pipe 14 It has a configuration in which a type of medium cooling device 16 is provided.
When the spray pipe 12 having the double structure has a movable structure that follows the circuit board as shown in FIG. 2, the board detection sensor 17 is disposed at the entrance of the solder bath. in this case,
Part of the cooling medium supply / recovery pipes 14 and 15 may be made of a flexible material so as not to hinder the reciprocating movement of the spray pipe 12.

FIG. 6 shows an electronic component to be cooled (a narrow-pitch lead component) on a circuit board being conveyed in a soldering apparatus.
It is a figure showing the temperature change of the 11 soldering part. As can be seen from the figure, the temperature of the soldering part is the peak temperature t1 when the component is carried into the soldering process section.
Becomes The peak temperature t1 is equal to the solder melting temperature t2 (= 1
When the temperature exceeds (83 ° C.), the bonded solder portion is re-melted. In the soldering apparatus according to the present invention, the inert gas spray pipe 12 for cooling the substrate is disposed immediately above the solder bath 7.
By blowing the low-temperature cooling gas injected from the nozzle holes onto the upper surface of the substrate, it is possible to lower the peak temperature of the soldered portion to a temperature t1 'in the safe zone, which is much lower than the remelting temperature of the solder.

[0020]

As apparent from the above embodiments, the soldering apparatus according to the present invention is not only a gas circulation mechanism for cooling a high-temperature atmosphere gas in a chamber, but also an inert gas spray for substrate cooling. Equipped with a nozzle mechanism (blow-off pipe), and by vigorously blowing a cooling inert gas onto a circuit board being conveyed in a high-temperature atmosphere, the mounted component can be cooled to a temperature sufficiently lower than the solder remelting temperature. According to the present invention, it is not necessary to perform a special pretreatment for each circuit board in order to prevent a rise in temperature, and it is possible to efficiently solder electronic components to the circuit board.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of a flow soldering apparatus according to the present invention provided with a circuit board cooling gas spray pipe.

FIG. 2 is a sectional view of a main part showing another embodiment of the flow soldering apparatus according to the present invention having a movable circuit board cooling gas blowing pipe.

FIG. 3 is a sectional view of a main part showing still another embodiment of the flow soldering apparatus according to the present invention having a gas blowing pipe portion for cooling a circuit board having a double structure.

FIG. 4 is a cross-sectional view showing one example of a substrate cooling gas blowing pipe having a double structure.

FIG. 5 is a view showing the overall configuration of a flow soldering apparatus according to the present invention including a gas blowing pipe portion for cooling a circuit board having a double structure.

FIG. 6 is a diagram for explaining temperature transition of electronic components on a circuit board being conveyed in the flow soldering apparatus.

FIG. 7 is a diagram showing a configuration of a conventional flow soldering apparatus.

[Explanation of symbols]

1: circuit board, 2: conveyor, 3: chamber, 4:
Spray type flux coating device, 5: heater, 6: inert gas blowing pipe, 7: solder bath, 8: inert gas suction pipe, 9: inert gas delivery pipe, 10: atmosphere cooling device, 11: electronic component, 12: Substrate cooling gas blowing pipe, 13: Cooling gas supply pipe, 14: Blowing pipe cooling medium delivery pipe, 15: Blowing pipe cooling medium recovery pipe, 16: Cooling medium cooling device, 17: Substrate detection sensor , 18: ball screw, 19: solenoid valve, 20:
Motor, 21: sequence controller.

Continued on the front page (72) Inventor Tomoharu Horii 216 Totsukacho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Communications Division (72) Inventor Tomoyuki Omura 216 Totsukacho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Inside the Manufacturing Division (72) Inventor Hideki Ono 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi Division Communication Division (72) Yoshikazu Mutoh 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Corporation Hitachi Communications Division (72) Inventor Yuzo Kato 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi Communications Division Communications Division 4E080 AA01 AB03 AB06 CA20 5E319 AC01 CC24 CD35

Claims (4)

[Claims] 1. A circuit board is transported in an inert gas atmosphere.
In a flow soldering apparatus for soldering an electronic component by bringing molten solder jetted from a solder bath into contact with the back surface of the circuit board, an inert gas spray having a plurality of nozzle holes is provided above the solder bath. An electronic component already mounted on the circuit board is cooled by arranging a pipe and spraying an inert gas for cooling the board sprayed from the spray pipe on the upper surface of the circuit board passing through the solder bath. And a flow soldering device characterized by preventing re-melting of the already soldered portion. 2. The spraying pipe has a double structure consisting of a center pipe and an outer pipe, an inert gas for cooling a substrate is supplied to the center pipe, and a cooling medium flows through the outer pipe. 2. The flow soldering apparatus according to claim 1, wherein a temperature rise of the substrate cooling inert gas in the pipe is suppressed. 3. A circuit for moving the spraying pipe in a circuit board conveying direction along with the movement of the circuit board in the solder bath area, wherein the spraying pipe is perpendicular to the circuit board conveying direction. 2. The arrangement according to claim 1, wherein a specific area on the circuit board is continuously cooled by an inert gas for cooling the board from the spray pipe during the soldering process. Or the flow soldering apparatus according to claim 2. 4. A method for soldering an electronic component by transporting a circuit board in a chamber filled with an inert gas and bringing molten solder jetted from a solder bath provided in the chamber into contact with the back surface of the circuit board. An inert gas circulating cooling means for discharging a high-temperature inert gas in the vicinity of the solder bath to the outside of the chamber and returning the inert gas cooled by the cooling device to the inside of the chamber; Substrate cooling means for cooling the circuit board by injecting an inert gas from a spray pipe having a plurality of nozzle holes disposed above the bath, wherein the temperature of the inert gas atmosphere near the solder bath is controlled by the inert gas. While cooling by the active gas circulation cooling means, the substrate cooling inert gas injected from the spray pipe on the upper surface of the circuit board passing through the solder bath By attaching, flow soldering apparatus being characterized in that so as to prevent the re-melting of the soldering portion in already electronic components already mounted on the upper surface of the circuit board.