JP3088837B2 - Heating furnace for soldering - Google Patents

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, and the solder is melted and soldered. In this case, the heating furnace is filled with an inert gas such as nitrogen gas to prevent oxidation of the circuit board and the electronic components.

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

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

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

In the example shown in FIG. 4, the inert gas supply pipe 27 is installed in the outlet passage 21, but the inert gas supply pipe 27 may be installed in the heating chamber 17.

[0007]

It is desirable that the component-mounted circuit board, which has been soldered, be cooled to a temperature at which oxidation does not proceed when exiting through the outlet passage. If a large number of seal plates are provided 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.

Accordingly, 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. However, the use of cooling water may cause an accident such as water leakage. In addition, operation and inspection are troublesome,
There is a practical problem.

[0009]

SUMMARY OF THE INVENTION The present invention provides a soldering heating furnace which solves the above-mentioned problems, and has a structure for heating a circuit board on which electronic components are 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; inside the inlet passage and the outlet passage, a predetermined direction is set in the traveling direction of the circuit board. In a heating furnace for soldering, in which a number of seal plates are provided to restrict the flow of the inert gas in the heating chamber out of the furnace at intervals, the surface of the seal plate in the outlet passage is blackened. It is a feature.

[0010]

When 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 seal plate and the peripheral wall of the outlet passage. Since the discharge is performed, the cooling efficiency of the circuit board passing through the outlet passage is improved.

In order to further improve 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 increase the heat conductivity from the inside to the outside of the outlet passage. It is effective to attach heat radiation fins to the outer surface of the peripheral wall of the exit passage to improve the heat radiation characteristics of the exit passage.

[0012]

Embodiments of the present invention will be described below 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 therefore, only the feature points will be described here.

A feature of the heating furnace shown in FIG. 1 is that the sealing 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 passing 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
Is desirably made of a copper plate (or aluminum plate) having a black surface.

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

The heating furnace shown in 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 provided outside the outlet passage 21. That is. This way the exit passage
The heat radiation of 21 is further improved, and the cooling efficiency of 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 transmitted to the outside of the outlet passage through the seal plate and the peripheral wall of the outlet passage. Since the circuit board is discharged, the circuit board passing through the outlet passage can be efficiently cooled. Therefore, it is possible to eliminate defects such as misalignment of components caused by insufficient solidification of the solder due to insufficient cooling when leaving the heating furnace.

[Brief description of the drawings]

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

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

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

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

[Explanation of symbols]

 11: Planar heater 13: Bar 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 33: Radiation fin 35: Fan

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-157462 (JP, A) JP-A-5-161963 (JP, A) JP-A-59-125266 (JP, A) JP-A-4- 253566 (JP, A) JP-A 5-263 (JP, U) JP-A 4-98364 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 1/00-1 / 20 B23K 31/02 310 H05K 3/34 507

Claims (3)

(57) [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 number of seal plates are provided at predetermined intervals in the traveling direction of the circuit board to restrict the flow of the inert gas in the heating chamber out of the furnace. A heating furnace for soldering, wherein a surface of a seal plate of the outlet passage is made 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 device according to claim 1 , wherein a radiation fin is attached to an outer surface of a peripheral wall of the outlet passage .
Heating furnace .