JPH0499086A - Reflowing device - Google Patents

Abstract

PURPOSE:To collectively perform reflow soldering by providing a heat source section which heats a substrate while it is in contact with the lower surface of the substrate, means which holds and places the substrate on the heat source section, and cooling means which cools a desired electronic parts on the substrate by bringing a cold substance into contact with the parts. CONSTITUTION:A substrate 10 is slightly pressed against a heat resisting film 23. Since melted solder 22 is pressurized, the film is somewhat swelled upward at its central part and the substrate 10 can be brought into close contact with the film 24 toward the peripheral part from the center. Therefore, no air is taken between the substrate 10 and film 24. Moreover, since the film 24 is flexible, no clearance is formed between the substrate 10 and film 24 even when the substrate 10 is somewhat bent and the entire surface of the substrate 10 is uniformly heated by means of the melted solder 22 heated to a prescribed temperature through the film 24. When reflowing is made in the first heat source section 1, in addition, damage of electronic parts 10 which is weaker in heat resisting property can be prevented surely, since the parts 10a are cooled by cooling air blown upon the parts 10a from a cooling nozzle 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a reflow apparatus that heats paste-like solder coated on a substrate.

(Prior Art) Conventionally, when performing reflow soldering, a board coated with paste solder is inserted into a reflow oven. Known reflow ovens include a convection method that heats by blowing hot air, a radiation method that irradiates with infrared rays, a heat transfer method that heats the substrate by placing it on a heat block, and a method that uses a combination of these methods.

For example, as shown in FIG. 6, the substrate 40 is placed in a reflow oven 4.
While the substrate 40 is being conveyed by the conveyor 42 disposed in the substrate 1, the ambient temperature around the substrate 40 is raised to 240° C. by blowing hot air from the heating unit 43 placed at the upper or lower part of the conveyor path or by irradiating infrared rays. There are known devices that are configured to maintain the temperature at a certain level for a predetermined period of time.

Furthermore, in Japanese Patent Application Laid-Open No. 54-80565, a plate with good thermal conductivity is floated on a heated liquid substance such as molten solder, a board is placed on top of this plate, and the plate is placed on top of the plate with good thermal conductivity. A method of reflowing paste-like solder on a board and soldering is disclosed.

(The problem that the invention is trying to solve is that the substrate 40 cannot be heated by the reflow oven 41.)
Not only is it difficult to uniformly heat the entire surface of the
When electronic components with low heat resistance such as hybrid IC components are mounted on the board 40, reflow soldering cannot be performed all at once because there is a risk that the electronic components may be damaged. After reflow soldering, the only option is to perform separate manual soldering or separate reflow soldering using a laser beam, etc., which complicates the circuit board manufacturing process and increases costs. Ta.

In addition, in the flow method disclosed in the above publication, heated molten solder is used as a heat source, so in principle the temperature distribution becomes uniform and it is possible to uniformly heat the entire surface of the board. In reality, it is unavoidable that the board will warp to some extent, so a gap may be formed between the board and the plate, which has good thermal conductivity.If a gap occurs, the thermal conductivity will decrease significantly, so it will eventually become uniform. There is a problem in that it is not possible to perform proper heating, and, similarly to the above, there is a problem in that it is not possible to reflow all at once when electronic components with low heat resistance are mounted.

In view of the above-mentioned conventional problems, the present invention has developed a reflow device that can perform reflow soldering all at once on boards on which electronic components with low heat resistance are mounted, and that can heat uniformly and perform high quality soldering. The purpose is to provide

(Means for Solving the Problems) In order to achieve the above object, the reflow apparatus of the present invention heats the substrate by heat conduction by bringing the bottom surface of a board on which paste-like solder is applied to the top surface and on which electronic components are mounted into contact with each other. It is characterized by comprising a heat source section, means for holding the board and installing it on the heat source section, and means for bringing a cold substance into contact with desired electronic components on the board to cool them.

Preferably, the heat source unit seals the top opening of a tank having an opening on the top surface with a flexible thin film, and fills the tank with a fluid having fluidity at least in a heated state. The configuration includes a heating means for heating the fluid to a predetermined temperature.

(Function) According to the above configuration of the present invention, the heat source unit heats the board efficiently and relatively uniformly by heat transfer from the bottom surface of the board to reflow the paste-like solder applied on the board. Moreover, damage to electronic components with low heat resistance can be reliably prevented by cooling them with a cooling means from above, so even if electronic components with low heat resistance are mounted, Reflow soldering can be performed all at once.

Further, as a heat source part, a flexible thin film body is arranged so as to be in contact with the upper surface of a fluid having a uniform temperature distribution heated to a predetermined temperature by a heating means, and the substrate is brought into contact with the thin film body. By using a thin film, even if the heat transfer surface in contact with the thin film of the substrate has some unevenness, there will be no gap between the thin film and the thin film, which is thin and has good thermal conductivity. The board can be heated efficiently and uniformly through the wafer, making it possible to perform high-quality reflow soldering.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5.

In FIG. 1, 1 is a first heat source section for reflow, 2 is a second heat source section for preheating, 3 is an incoming conveyor, and 4 is an outgoing conveyor. Reference numeral 5 denotes a conveyance device that sequentially conveys the substrate 10 carried in by the carry-in conveyor 3 to the second heat source section 2, the first heat source section 1, and the carry-out conveyor 4. Reference numeral 6 denotes cooling means for the substrate 10 disposed at the lower part of the carry-out conveyor 4.

The transport device 5 includes a guide rail 7 arranged along the transport direction of the substrate 10, a movable body 8 movable along the guide rail 7, and a lifting means 9 attached to the movable body 8. It is composed of a holding head 11 that is moved up and down and attracts and holds the substrate 10. On the substrate 10,
As shown in FIG. 2, a heat-resistant electronic component 10 is coated with paste-like solder to be reflowed.
In addition to the electronic component 10a having low heat resistance, the electronic component 10a is mounted.

As shown in FIG. 2, the holding head 11 is provided with a suction nozzle 12 so as to suction and hold a total of six places, two places each at both ends and an intermediate part of the substrate 10.
A cooling nozzle 13 is provided so as to face the upper part of the electronic component 10a having low heat resistance mounted on the substrate 10 that has been sucked by the suction nozzle 12. The suction nozzle 12 communicates with a suction port 14 connected to a suction source (not shown), and the cooling nozzle 13 communicates with a cooling air supply port 15 connected to a cooling air supply means (not shown).

The first heat source section 1 and the second heat source section 2 are configured as shown in FIG. 3. Note that the second heat source section 2 is connected to the substrate 10
Since the configuration is the same as that of the first heat source section 1 except that the temperature is controlled to a low temperature in order to preheat the heat source section 1, only the first heat source section 1 will be described below.

In FIG. 3, reference numeral 21 denotes a tank with an open top surface containing molten solder 22, and a first heating means 23 is disposed on the lower surface of the tank, and is configured to maintain molten solder 22 at a predetermined temperature. The open top surface of this tank 21 is hermetically covered with a heat-resistant film 24 such as a 50 μm thick polyimide film, which is placed in contact with the top surface of the molten solder 22 . Reference numeral 25 denotes a fixing frame that fixes the periphery of the heat-resistant film 4 to the inner periphery of the upper end of the tank 21 in a sealed state.

An example of this tank 21 is that this tank 21 is
A preliminary tank 26 is disposed in communication with the tank, and a second heating means 28 is disposed on the lower surface thereof, and a second heating means 28 is connected to the first and second heating means 2.
A heat insulating material 29 is interposed between 3.28 and is configured to be able to be heated separately. A dipping body 31 that can be raised and lowered between a lowered position where it is immersed in the molten solder 22 and a raised position where it is retracted upward is provided at the upper part of the preliminary tank 26. When it is lowered at 32 and immersed in the molten solder 22, the upper surface of the molten solder 22 in the preliminary tank 26 rises as shown by the imaginary line, and the head pressure H acts on the molten solder 22 in the tank 21. It is configured to apply pressure. In this way, the head pressure H is used to
By pressurizing the molten solder 22 in 1, a stable pressurized state can be obtained.

Further, as a damage detection means 33 for the heat-resistant film 24, a pair of electrodes 34a and 34b are connected to each other by the molten solder 22 when the immersion body 31 is immersed and the upper surface of the molten solder 22 in the preliminary tank 26 is raised. It is connected to a power source 35 and an alarm 36, and is configured to issue an alarm when the top surface of the molten solder 22 descends and the picture electrodes 34a and 34b are insulated while the immersion body 31 is immersed. ing.

In the above configuration, in order to reflow and solder the paste-like solder on the base l1jlO, the board 10 is carried in by the carry-in conveyor 3, and the board 1o is sucked and held by the holding joint 1 of the transport device 5. The holding head 11 sequentially supplies the substrate 1o onto the first and second heat source sections 1.2. In these heat source parts 1.2, the substrate 10 held by the holding head 11 is brought into contact with the heat-resistant film 24 on the upper surface of the tank 21 as shown in FIG. 4, and further, as shown in FIG. The substrate 1o is slightly pressed against the heat-resistant film 24. At this time, since the molten solder 22 is pressurized, the center of the heat-resistant film 24 bulges slightly upward as shown in FIG. Since the heat-resistant film 24 can be brought into close contact with the substrate 1o and the heat-resistant film 24 in order, air will not be trapped between the substrate 1o and the heat-resistant film 24.

Furthermore, since the heat-resistant film 24 is flexible, the substrate 10
Even if there is some warpage, there is no need to live in the room,
The heat-resistant film 24 is strongly adhered along the lower surface of the substrate 1o, and the entire surface of the substrate 10 is uniformly heated by the molten solder 22 heated to a predetermined temperature via the heat-resistant film 24.

That is, since the molten solder 22 is in a liquid state, its temperature distribution can be easily made uniform, and by pressing the lower surface of the substrate 1o in close contact with the thin heat-resistant film 24 that is in contact with the upper surface of the molten solder 22, the temperature distribution can be uniformly applied to the substrate 1o. Heat is transferred to and heated efficiently and uniformly. Furthermore, since the molten solder 22 is covered with the heat-resistant film 24 in contact with its upper surface, its oxidation is prevented, and a decrease in thermal conductivity and overall non-uniformity due to the formation of oxides can be prevented. In this way, the paste-like solder on the substrate 10 reflows uniformly, resulting in high-quality soldering.

Furthermore, when reflowing in the first heat source section 1, the electronic component 10a with low heat resistance is cooled by blowing cooling air from above with the cooling nozzle 13, so that damage to the electronic component 10a can be reliably prevented. I can do it. Of course, this electronic component 1
The lead 0a is also reliably reflow soldered by the heat supplied from the bottom surface of the board 10. In this way, the substrate 1
Even if electronic component 10a with low heat resistance is mounted on o,
It is possible to perform reflow soldering all at once without fear of damaging the film. If the heat-resistant film 24 is damaged, the molten solder 22 will leak out and the top surface of the molten solder 22 in the preliminary tank 26 will be Since the electrodes 34a and 34b are insulated, the alarm 36 can be activated and the alarm can be detected immediately, allowing appropriate treatment to be taken promptly.

Furthermore, when the work is finished, first the operation of the first heating means 23 is stopped, the molten solder 22 in the tank 21 is cooled and solidified, and the heat-resistant film 24 is protected by supplying the shrinkage at that time from the preliminary tank 26. After the molten solder 22 in the tank 21 is cooled and solidified, the operation of the second heating means 28 is stopped and the molten solder 22 in the preliminary tank 26 is cooled and solidified. Furthermore, at the start of work, for the same reason, the second heating means 28 is activated to melt the solder in the preliminary tank 26, and then the first heating means 23 is activated to melt the solder in the tank 21. .

In the above embodiment, molten solder 2 was used as the heating fluid, but silicone oil or the like may also be used. In addition, an example is shown in which a heat-resistant film 24 such as a polyimide film is used as the thin film, but it also has the necessary strength and heat resistance against the heated fluid, and also has the ability to prevent the heated fluid from passing through and flowing upward. It is possible to use a thin film-like body made of any material.

Further, although an example has been shown in which cooling air is blown out from the cooling nozzle 13 as a means for cooling the electronic component 10a with low heat resistance, it may be cooled by bringing a cooling block into contact with the electronic component 10a.

(Effects of the Invention) According to the present invention, it is possible to reflow the paste-like solder applied on the substrate by efficiently and relatively uniformly heating the substrate using a heat transfer method from the bottom surface of the substrate in the heat source section. Moreover, damage to electronic components with low heat resistance can be reliably prevented by cooling them with a cooling means from above, so even if electronic components with low heat resistance are installed, they can be cooled all at once. This has the effect of allowing reflow soldering to be performed.

Further, as a heat source part, a flexible thin film body is arranged so as to be in contact with the upper surface of a fluid having a uniform temperature distribution heated to a predetermined temperature by a heating means, and the substrate is brought into contact with the thin film body. By using a thin film, even if the heat transfer surface in contact with the thin film of the substrate has some unevenness, there will be no gap between the thin film and the thin film, which is thin and has good thermal conductivity. The board can be heated efficiently and uniformly through the wafer, making it possible to perform high-quality reflow soldering.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view of one embodiment of the present invention, Fig. 2 is an enlarged view of the holding head section which is the main part, Fig. 3 is a longitudinal sectional side view showing the configuration of the heat source section, Fig. 4, FIG. 5 is a sectional view showing the state of contact with the thin film body immediately before heating the substrate and in the heated state, and FIG. 6 is a configuration diagram of a conventional example. 1--------・・--・-1-----～--・・--First heat source part 0--・--・・-------1-----
−・Substrate 1 ・−・−・−−−−−−Holding head 3
・・−・−−−−−−−・−−−−−−−−−−−・−
Cooling nozzle 1−・−・・−・−・−・−Tank 2・−・−−−−1・−・−・・−−1−−−−−
Molten solder 3 -----First heating means 4--
−−−・−−−−−−−・・・−・−−1−−−−−−
Heat resistant film.

Claims (2)

[Claims] (1) a heat source unit that conductively heats the bottom surface of a board on which paste solder is applied and electronic components are mounted by contacting it, and a means for holding the board and installing it on the heat source unit;
1. A reflow apparatus comprising: means for bringing a cold substance into contact with desired electronic components on a substrate to cool them. (2) The heat source unit seals the top opening of a tank having an opening on the top surface with a flexible thin film, and fills the tank with a fluid that has fluidity at least in a heated state, and fills the tank with a fluid that is fluid at least in a heated state. 2. The reflow apparatus according to claim 1, further comprising heating means for heating the reflow to a predetermined temperature.