JP3404768B2 - Reflow equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow apparatus and a reflow method for soldering and mounting electronic components on a printed circuit board.

[0002]

2. Description of the Related Art In recent years, a technique for mounting electronic components on a printed circuit board has required increasingly more soldering and joining of electrodes of finer electronic components and circuits formed on the printed circuit board. Further, in recent years, with the abolition of CFC cleaning, soldering without cleaning is required.

In the conventional reflow apparatus, the printed circuit board is heated by using air heated to a predetermined temperature as a heat medium to melt the solder and solder the electronic parts.

FIG. 10 shows a conventional device known from Japanese Patent Laid-Open No. 63-278668. As you can see in the figure,
An air circulation path c traversed by a conveyor b that conveys the printed circuit board a is arranged in the longitudinal direction of the conveyor b without a gap, and internal air is circulated by two sirocco fans d in each air circulation path c. The circulating air is heated by the two heaters e, and the heated air is supplied to the air circulation path c.
Soldering is performed by spraying onto the printed circuit board a on the conveyor b that traverses the board.

[0005]

However, in the above-mentioned conventional device, the electrodes of the fine electronic parts, the circuit formed on the printed circuit board a, and the cream solder used for joining are oxidized during the heating, and the solder paste is excellent. There is a problem that can not be soldered. Therefore, the yield is poor and the cost of the product is high.

The present invention solves the above-mentioned conventional problems, and remelts the cream solder while preventing the oxidation of the cream solder used for bonding electrodes and circuits of fine electronic components and printed circuit boards. It is an object of the present invention to provide a reflow apparatus and a reflow method aiming at the above.

[0007]

In order to achieve the above object, a reflow apparatus of the present invention is a heating apparatus for heating a furnace body portion and a printed circuit board on which an electronic component is mounted in the furnace body portion. parts and a transport section for transporting the printed circuit board, and a fan for circulating a heat air, provided with a suction port of the fan on the lower side of the transport unit, the suction port and transportable of the fan
It is provided with a plate between the feeding section .

The plate has a structure in which the end portion is bent so as to surround the conveying portion.

[0009] As a further plate is obtained by a U-shaped section formed by bending the end portion other than the peripheral port and blowing outlet of the hot air toward the print circuit board conveying surface.

[0010]

With the above structure, the printed circuit board on which the electronic parts are mounted is transported by the transport unit and passes through the inside of the reflow furnace body. During this passage, the printed circuit board is heated through the atmosphere by the heating means provided in the reflow furnace body, At this time, the solder is re-melted to be soldered, but the atmosphere in the reflow furnace is maintained at a predetermined inert gas concentration by the supply of the inert gas from the inert gas supply section. It is possible to prevent the electrodes of the fine electronic components, the circuits formed on the printed circuit board, and the cream solder used for joining from being oxidized, and the soldering can be performed well.

If a suction port of a fan that circulates hot air used as one of heating means for heating the printed circuit board is set below the carrying portion of the printed circuit board, it is caused by carrying the printed circuit board. It is possible to reduce the turbulence of the air flow in the furnace body and maintain the atmosphere in the reflow furnace body at a predetermined inert gas concentration by supplying the inert gas from the inert gas supply unit.

As a method of setting the suction port of the fan on the lower side of the transport section, a method having a plate between the suction port of the fan and the transport section, or a plate whose end portion is bent so as to surround the transport section is further provided. The turbulence of the air flow in the furnace body caused by carrying the printed circuit board can be reduced, and the atmosphere in the reflow furnace body can be maintained at a predetermined inert gas concentration by supplying the inert gas from the inert gas supply unit.

Further, by providing a hot air blowout port from the plate surface toward the conveyance surface of the printed circuit board and a plate having a U-shaped cross section in which an end portion other than the periphery of the blowout port is bent, The turbulence of the air flow in the furnace body portion due to the blowing of hot air can be reduced, and the atmosphere in the reflow furnace can be maintained at a predetermined inert gas concentration by supplying the inert gas from the inert gas supply portion.

[0014]

(Embodiment 1) Hereinafter, a reflow apparatus according to a first embodiment of the present invention will be described with reference to the drawings.

As shown in FIGS. 1 and 2, when the conveyor 2 runs vertically through the reflow furnace body 1a of the furnace body portion 1, and the printed circuit board 3 on which the electronic components 6 are mounted is supplied from the previous process. , The conveyor 2 conveys this and reflow furnace body 1
Pass a from the entrance tunnel 4 to the exit tunnel 5 at a predetermined speed.

The reflow furnace body 1a has a preheating chamber 11 for preheating a plurality of printed circuit boards 3 from an inlet tunnel 4, a plurality of reflow heating chambers 12 for heating the preheated printed circuit boards 3, and a printed circuit board after reflow. It is divided into one cooling chamber 13 for cooling 3.

A preheating heater 15 is provided at the back side of the conveyor 2 in the preheating chamber 11, and a conveyor 2 in the reflow heating chamber 12 is provided.
A reflow heater 16 is provided at the back side of the cooling chamber 13
The heat exchangers 17 for cooling are provided at the back side of the conveyor 2.

Further, each preheating chamber 11 and reflow heating chamber 12
And the lower part of the conveyor 2 in the cooling chamber 13 through the fan suction port 18a.
Is provided.

Further, each preheating chamber 11 and reflow heating chamber 12
An inert gas supply pipe 24 is connected to each bottom of the cooling chamber 13 via a flow meter 22, and N2 gas, which is an inert gas, is passed through a valve 26 at a predetermined flow rate to each preheating chamber 11 and reflow heating chamber 12. And, it is sent into the cooling chamber 13 so that the atmosphere of the reflow furnace body 1a is maintained at a predetermined inert gas concentration.

A plate 21 is provided on the lower surface of the conveyor 2 in the reflow furnace body 1a. Due to this plate 21, the air flow in the reflow furnace body 1 follows the arrow 19 shown in FIG.

Next, the operation will be described. Each preheating room 1
1, the atmosphere of the reflow heating chamber 12 and the cooling chamber 13,
A predetermined inert gas concentration is set by the gas supply from the inert gas supply pipe 24, and the preheating heater 1
5, the reflow heating heater 16 and the heat exchange 17 set a predetermined temperature, and the sirocco fan 18 acts to circulate the atmosphere throughout the room, so that each preheating chamber 11, reflow heating chamber 12, and cooling chamber The entire area within 13 is controlled to have a uniform inert gas concentration and temperature.

Further, even if the printed circuit board 3 is carried into each chamber due to the presence of the plate 21, the flow of the circulating flow in each chamber does not largely change, so that each preheating chamber 11,
The entire area of the reflow heating chamber 12 and the cooling chamber 13 is controlled to a stable and uniform inert gas concentration.

As a result, the printed circuit board 3 passing through the reflow furnace body 1a is preheated as shown in FIG.
After being heated to about 150 ° C, the reflow heating chamber 12
Then, it is heated to 220 ° C. and soldered by remelting the solder. Then, it is cooled in the cooling chamber 13.

Since the above steps are performed under a predetermined inert gas concentration of inert gas, electrodes of the fine electronic component 6, circuits formed on the printed circuit board 3, cream solder used for bonding, etc. Oxidation due to heating can be prevented all the time, and the soldering can be performed well.

In this embodiment, both ends of the plate 21 are bent, but this bending may be partially deleted to stabilize the flow of the circulating flow in each chamber of the reflow furnace body 1a.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention, in which forced exhaust having an exhaust duct 27, an exhaust amount adjusting valve 27, an exhaust blower 29 and an inert gas curtain portion 30 at the inlet of the inlet tunnel 4. By including the portion, the atmospheric air is prevented from being entrained in the furnace body portion 1 and the atmosphere of the reflow furnace body 1a is maintained at a predetermined inert gas concentration, and the inert gas leaking from the furnace body portion 1 is removed from the outside of the apparatus. Without discharging it indoors, it is sent together to the factory exhaust by the exhaust blower 29. Further, by adjusting the exhaust amount with the adjusting valve 28, the atmosphere in the reflow furnace can be maintained at a predetermined inert gas concentration in a more stable state.

(Embodiment 3) FIG. 5 shows Embodiment 3, in which the atmosphere gas blown by the sirocco fan 18 in the cooling chamber 13 takes away the heat of the heated printed circuit board 3 and then the heat exchanger 17. Then, the sirocco fan 18 repeats blowing air to create a circulating flow. Since the heat exchanger 17 is on the back surface, the flux floating in the atmospheric gas in the circulation flow path can be recovered by the heat exchanger 17 having the cooling fins. The heat exchanger 17 has a structure that can be taken out on the back side, so that the cleaning work can be simplified.

(Embodiment 4) FIG. 5 shows Embodiment 4, in which the atmosphere is re-established by the heater 31 provided in the circulation flow path of the atmosphere gas circulated by the sirocco fan 18 before the reflow device is stopped in the cooling chamber 13. The gas is heated to vaporize the solidified flux, and the catalyst 32
It is possible to purify and remove the flux by causing a combustion reaction with.

Further, in order to remove the flux, a filter 33 may be provided below the conveyor 2 which conveys the printed circuit board 3 in the circulation flow path.

(Embodiment 5) FIG. 6 shows Embodiment 5 in which, in the entrance tunnel 4, in the direction of the entrance and exit of the furnace 2 in the furnace body 1 or the conveyor 2 for carrying the printed circuit board 3 in a direction substantially perpendicular to the board carrying surface. When the vertical plate 34 is provided in a curved shape, the direction of the air flow is bent along the vertical plate 34, so that the outflow of the inert gas from the inside of the furnace body and the entrainment of air into the furnace body 1 are suppressed. The atmosphere of 1a can be maintained at a predetermined inert gas concentration.

(Sixth Embodiment) FIG. 7 shows a sixth embodiment, in which a conveyor 2 for carrying a printed circuit board 3 is longitudinally connected by connecting a substantially closed conveyor 36 having a connection structure in close contact with the entrance and exit of a reflow device. The inclusion of air in the reflow furnace body 1a is suppressed.
Further, by providing the closed conveyor 36 with the inert gas supply unit 35, it is possible to further prevent the air from being trapped in the reflow furnace body 1a, and to maintain the atmosphere of the reflow furnace body 1a at a predetermined inert gas concentration.

(Embodiment 7) FIG. 8 shows a reflow method of Embodiment 7 of the present invention, in which a reflow apparatus equipped with an inspection machine for recognizing a state after reflow soldering is used, and an inspection result of this inspection machine is obtained. By analyzing the mounting status by combining the printing status inspection results collected up to now and the electronic component mounting status inspection results, and setting the analysis results as optimum printing conditions, optimum mounting conditions, and optimum reflow conditions. The soldering quality can be improved.

(Embodiment 8) FIG. 9 shows an embodiment 8, in which a vertical plate 37 is provided below the carrying surface of the printed circuit board of the carrying unit and is substantially perpendicular to the carrying direction.
By providing a structure in which a plurality of vertical plates 37 are connected to each other in the transport direction, the flow of the air flow in the transport direction in the furnace body 1 is suppressed, and the air is prevented from being entrained in the furnace body 1. The atmosphere of the reflow furnace body 1a can be maintained at a predetermined inert gas concentration. The continuous body 38 of the vertical plate 37 can also be used as a conveyor 40 that receives the printed circuit board 3 dropped from the conveyor 2 and carries it out from the reflow furnace body 1a.

[0034]

As is apparent from the above description of the embodiments, according to the reflow apparatus and the reflow method of the present invention, the printed circuit board is carried by the carrying section and passes through the reflow furnace, and during the passage. It is heated through the atmosphere by the heating means provided in the reflow furnace, and at this time the solder is remelted and soldered, but the atmosphere in the reflow furnace is controlled by the supply of the inert gas from the inert gas supply unit. Since the predetermined inert gas concentration is maintained, the electrodes of the fine electronic components in the printed circuit board, circuits formed on the printed circuit board, or cream solder used for bonding is prevented from being oxidized, and the solder is used. Since the attachment can be performed favorably, the yield can be improved and the cost can be reduced.

If the suction port of the fan that circulates the hot air used as one of the heating means for heating the printed circuit board is set below the carrying section of the printed circuit board, it will be generated by carrying the printed circuit board. The turbulence of the air flow in the furnace body can be reduced, and the atmosphere in the reflow furnace can be maintained at a predetermined inert gas concentration by supplying the inert gas from the inert gas supply section, which guarantees oxidation prevention even during continuous production. Cheap.

As a method of setting the suction port of the fan on the lower side of the conveying unit, a method of further providing a plate having a plate between the suction port of the fan and the conveying unit, or a plate whose end portion is bent so as to surround the conveying unit is further provided. , It is easy to maintain the predetermined inert gas concentration by supplying the inert gas from the inert gas supply unit to the atmosphere in the reflow furnace by reducing the turbulence of the air flow in the furnace body caused by carrying the printed circuit board. Antioxidation can be reliably achieved.

Further, by providing a hot air blowout port from the plate surface toward the conveyance surface of the printed circuit board and a plate having a U-shaped cross section in which an end portion other than the vicinity of the blowout port is bent, The turbulence of the air flow in the furnace body due to the blowing of hot air is reduced, and the atmosphere in the reflow furnace can be easily maintained at the specified inert gas concentration by supplying the inert gas from the inert gas supply unit, and the oxidation prevention can be reliably achieved. be able to.

[Brief description of drawings]

FIG. 1 is a schematic front sectional view showing a configuration of a reflow apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic side sectional view showing the structure of the reflow heating chamber.

FIG. 3 is a characteristic diagram showing a temperature change during a processing step of the same printed circuit board.

FIG. 4 is a schematic front cross-sectional view showing the configuration of a forced exhaust unit of the reflow device according to the second embodiment.

FIG. 5 is a schematic side cross-sectional view showing the configuration of cooling chambers according to the third and fourth embodiments.

FIG. 6 (a) is a schematic plan sectional view showing the structure of an entrance / exit tunnel of the fifth embodiment. FIG. 6 (b) is a schematic front sectional view of the same.

FIG. 7 is a schematic front sectional view showing a configuration of a printed circuit board carrying conveyor showing the sixth embodiment.

FIG. 8 is a block diagram showing steps of the reflow method of the seventh embodiment.

FIG. 9 is a schematic front cross-sectional view showing the configuration of the reflow device of Example 8.

FIG. 10 is a schematic front sectional view showing the structure of a conventional reflow apparatus.

[Explanation of symbols]

1 furnace body 1a Reflow furnace 2 conveyors 3 printed circuit board 4 entrance tunnel 5 exit tunnel 6 electronic components 11 Preheating room 12 Reflow heating chamber 13 Cooling chamber 15 Preheater 16 Reflow heater 17 heat exchanger 18 Sirocco fan 18a Fan suction port 21 plates 22 Flow meter 24 Inert gas supply pipe 26 valves

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Manabu Ando 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-8564 (JP, A) JP-A-4-46 182063 (JP, A) Actual Kaihei 4-75665 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/34 B23K 1/008

Claims (3)

(57) [Claims] And 1. A furnace body section, this furnace body portion, a heating portion for heating the printed circuit board mounted with electronic components, and a conveying unit configured to convey the printed circuit board, and a fan for circulating a heat wind comprising a provided with a suction port of the fan on the lower side of the transport unit, the transport and the suction port of the fan
Reflow device with a plate between the parts . 2. A plate is bent at its end so as to surround the conveying section.
The reflow apparatus according to claim 1, wherein the reflow apparatus has a structure. 3. Hot air directed to the transfer surface of the printed circuit board.
The end of the plate other than the
The bending according to claim 1 or 2 to make a U-shaped cross section.
Reflow equipment.