JPH05305430A - Heating furnace for soldering - Google Patents

Abstract

PURPOSE:To improve cooling efficiency and to prevent the occurrence of defects caused by a deficient cooling by specifying a material of peripheral wall and sealing plates in the outlet passage and coloring the surface of the sealing plate with black, thereby enhancing the thermal conductivity from the inner part to the outer part of an outlet passage. CONSTITUTION:In a heating surface provided with plural sealing plates 29, the peripheral wall 31 and the sealing plates 29 in the outlet passage 27 are made of aluminum and the surface of the sealing plates 29 are colored with the black. By this method, the thermal conductivity from the inner part to the outer part of the outlet passage 27 is enhanced, and the heat radiated from the circuit board 23 passed through the outlet passage is efficiently discharged to out of the outlet passage, and the circuit board 23 passed through the outlet passage can efficiently be cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace for soldering an electronic component to a circuit board.

[0002]

2. Description of the Related Art When an electronic component is mounted on a circuit board by soldering, the circuit board on which the electronic component is mounted at a predetermined position is passed through a heating furnace to melt the solder for soldering. In this case, the heating furnace is filled with an inert gas such as nitrogen gas to prevent oxidation of the circuit board and electronic components.

Conventionally, in order to fill the inside of the heating furnace with an inert gas, a method of shutting the inside and outside of the furnace with a shutter has been generally used. However, since this method has a poor workability, as shown in FIG. A non-contact seal type heating furnace has been proposed.
This heating furnace has a sheet heater 11 and a rod heater 13 inside.
And heating chamber 17 where fan 15 is installed, and entrance passage
19 and an outlet passage 21, in which a circuit board 23 on which electronic components are mounted is run with both side edges supported by a chain conveyor 25. A mesh conveyor may be used instead of the chain conveyor.

The heating chamber 17 is filled with an inert gas in order to prevent oxidation of the circuit board 23 on which electronic components are mounted. This inert gas is supplied from the inert gas supply pipe 27. The supply amount of the inert gas is adjusted so that the inert gas is constantly and gradually discharged from the inlet passage 19 and the outlet passage 21 to the outside of the furnace in order to prevent air from entering the furnace from the outside.

In order to minimize the amount of this inert gas flowing out to the outside, a large number of sealing plates 29 are installed in the inlet passage 19 and the outlet passage 21 at predetermined intervals in the traveling direction of the circuit board 23. Has been done. This provides resistance to the inert gas passing through the passage and limits the outflow of the inert gas. The material of the seal plate 29 is generally stainless steel.

Although the inert gas supply pipe 27 is installed in the outlet passage 21 in the example of FIG. 4, the inert gas supply pipe 27 may be installed in the heating chamber 17 in some cases.

[0007]

It is desirable that the component-mounted circuit board that has been soldered should be cooled to a temperature at which oxidation does not proceed when it goes out through the outlet passage. If a large number of sealing plates are installed in the passage, heat radiated from the circuit board is likely to be trapped in the outlet passage, and it is difficult to sufficiently cool the circuit board in the outlet passage.

Therefore, it has been considered to arrange a water cooling pipe on the outer periphery of the outlet passage to enhance the cooling effect in the outlet passage, but using cooling water may cause an accident such as water leakage, In addition, since operation and inspection are troublesome,
There are practical problems.

[0009]

The present invention provides a heating furnace for soldering which solves the above-mentioned problems, and has a structure for heating a circuit board on which an electronic component is mounted to a soldering temperature. A heating chamber, an inlet passage for introducing the circuit board into the heating chamber, and an outlet passage for leading the circuit board out of the heating chamber are provided, and the inside of the inlet passage and the outlet passage are arranged in a predetermined traveling direction of the circuit board. In a soldering heating furnace in which a large number of sealing plates that restrict the outflow of the inert gas in the heating chamber out of the furnace at intervals are installed, the surface of the sealing plate of the outlet passage is black. It is a feature.

[0010]

If the surface of the seal plate of the outlet passage is made black, the heat radiated from the circuit board passing through the outlet passage is efficiently absorbed by the seal plate and transmitted to the outside of the outlet passage through the peripheral wall of the seal plate and the outlet passage. Since it is released, the cooling efficiency of the circuit board passing through the outlet passage is improved.

In order to further enhance the cooling efficiency of the circuit board, the peripheral wall of the outlet passage and the sealing plate are made of copper or aluminum (including a copper alloy or an aluminum alloy) to enhance the thermal conductivity from the inside to the outside of the outlet passage. That is, it is effective to attach a radiation fin to the outer surface of the peripheral wall of the outlet passage to improve the heat radiation characteristics of the outlet passage.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 3 each show an embodiment of the present invention. In each figure, the same parts as those of the heating furnace of FIG. 4 described above are denoted by the same reference numerals, and only the characteristic points will be described here.

The characteristic of the heating furnace of FIG. 1 is that the seal plate 29 is subjected to a blackening treatment to make the surface black. In this way, the heat radiated from the component mounting circuit board 23 is efficiently absorbed by the seal plate 29, transmitted through the seal plate 29 and the peripheral wall 31, and radiated to the outside of the outlet passage 21. The cooling efficiency of the circuit board 23 that passes through is increased. In order to further increase the cooling efficiency of the circuit board, the peripheral wall 31 of the outlet passage 21 and the seal plate 29, which are conventionally made of stainless steel plate,
It is desirable that the is made of a copper plate (or an aluminum plate) with a black surface.

The heating furnace shown in FIG. 2 is characterized in that the outlet passage 21 has the same structure as that shown in FIG.
The radiation fin 33 is attached to the outer surface of the. In this way, the heat dissipation of the outlet passage 21 is further improved, and the cooling efficiency of the circuit board 23 is increased.

The heating furnace of FIG. 3 is characterized in that the outlet passage 21 has the same structure as that of FIG. 2, and a fan 35 for blowing air to the peripheral wall 31 and the radiation fins 33 is installed outside the outlet passage 21. That is. This way the exit passage
The heat dissipation of 21 is further improved, and the cooling efficiency of the circuit board 23 is increased.

[0016]

As described above, according to the present invention, the heat radiated from the circuit board passing through the outlet passage is efficiently absorbed by the seal plate, and is transmitted to the outside of the outlet passage through the seal plate and the peripheral wall of the outlet passage. Since it is discharged, the circuit board passing through the outlet passage can be efficiently cooled. Therefore, it is possible to eliminate a defect such as a component deviation caused by insufficient solidification of the solder due to insufficient cooling when leaving the heating furnace.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of a soldering heating furnace according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a soldering heating furnace according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of a soldering heating furnace according to still another embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional heating furnace for soldering.

[Explanation of symbols]

 11: Sheet heater 13: Rod heater 15: Fan 17: Heating chamber 19: Inlet passage 21: Outlet passage 23: Circuit board with electronic components 25: Chain conveyor 27: Inert gas supply pipe 29: Seal plate 31: Peripheral wall of outlet passage 21: Radiating fins 35: Fan

Claims (3)

[Claims] 1. A heating chamber for heating a circuit board on which electronic components are mounted to a soldering temperature, an inlet passage for introducing the circuit board into the heating chamber, and an outlet passage for leading the circuit board out of the heating chamber. In the inlet passage and the outlet passage, a large number of sealing plates are installed at predetermined intervals in the traveling direction of the circuit board to restrict the outflow of the inert gas in the heating chamber to the outside of the furnace. A heating furnace for soldering, wherein the surface of the seal plate of the outlet passage is black. 2. The heating furnace for soldering according to claim 1, wherein the peripheral wall of the outlet passage and the seal plate are made of copper or aluminum (including a copper alloy or an aluminum alloy). 3. The soldering heating furnace according to claim 1 or 2, wherein a radiation fin is attached to the outer surface of the peripheral wall of the outlet passage.