MXPA98002839A - Method of welding by reflux and equipment of welding by reflux to weld through a method of welding by refl - Google Patents

Abstract

The outside air is supplied by a ventilation member within a heat exchange member in which heat exchange is carried out between the outside air and the interior air of different temperatures to reduce a difference in temperatures; The heat exchange that will be supplied with the outside air is heated by the hot air discharged from the heating member, thus heating the outside air being supplied to the heat exchange member, then the outside air heated in this way is heated further by the heating member to reach a high temperature

Description

METHOD OF WELDING BY REFLUX AND EQUIPMENT OF WELDING BY REFLUX TO WELD THROUGH A METHOD OF WELDING BY REFLUX BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to a reflow soldering method and to a reflow soldering equipment using the reflow soldering method for conveying, to a heating member, a printed board assembled with a circuit component and coated with solder in the form of cream on a transport member such as a belt conveyor. In the heating member the printed board is heated to melt the solder in the form of cream and in this way carry out the welding. 2. Description of the Related Art A conventional reflow welding equipment that has been proposed in Japanese Patent Application No. Hei 6-175657 by the applicant of the present invention will be explained. The reflow welding equipment, as shown in Figure 7, is equipped with a transporting member 1 carrying a printed board not illustrated, mounted with a circuit component also not illustrated and coated with cream-shaped solder, inwards from the side A of augmentation and then to side B of discharge.

The transporting member 1 comprises an endless chain conveyor, a drive motor Ib for driving the chain conveyor, and a conveyor rail for guiding the chain conveyor so that the chain conveyor does not yield downward with the chain conveyor. printed board weight and others. With the rotation of the drive motor lb, the printed board moves in the direction of arrow C, that is, from the upstream side to the downstream side. On the upstream side of the interior of the conventional reflow welding equipment in which the chain conveyor passes it, a first preheating furnace 2 and a second preheating furnace 3 are arranged as preheating members. In a case 2a of the first preheating furnace 2, a pair of fans 2b are mounted. On the pair of fans 2b there are arranged six infrared heaters 2d. In the first preheating furnace 2 air is fed up into the case 2a by the fan 2b into the infrared heater 2d, in which the air is heated. The hot air hits the upper inner surface of the case 2a and is reflected downward, circulating inside the case 2a to preheat a printed non-illustrated board that has been assembled with a circuit component and coated with cream solder.

The second preheating furnace 3 located on the downstream side of the first preheating furnace 2 has the same constitution as the first preheating furnace 2 and will therefore not be described. On the downstream side of the second preheating furnace 3 a reflow oven 14 is arranged. The reflow oven 14 has a heater box 14a located immediately below the chain conveyor la. In the upper part of this heater box 14a, a plurality of heating nozzles 14b are arranged along the travel direction of the chain conveyor la. A plurality of heaters not shown are placed inside the heater box 14a, with which the air fed therein will be heated to a high temperature. In the upper part of the reflow furnace 14 is arranged a relief cover 15 to which a relief pipe 6 and a circulation pipe 16 are connected. From the relief pipe 6 a part of the hot air at high temperature after the venting fusion of the coated cream-shaped solder on the printed board, is carried in the direction of arrow D and is discharged out of the reflow-welding equipment. The residual hot air not removed by the vent pipe 6 is brought in by a fan 17 from the circulation duct 16 in the direction of the arrow E, being fed back into the heater box 14a of the reflow oven 14 from the inlet port 17a, through a relief port 17b. Then, the fan 17 is disposed below the reflow oven 14 and the circulation duct 16 is extended and connected to the relief cover 15. On the chain conveyor is the cooling fan 9 having a plurality of cooling plates. 9a flow straightening to cool the printed printed board. In a conventional reflow welding equipment, a falling object receiving network 10 is disposed below the first and second preheating furnaces 2 and 3 to receive unnecessary materials such as weld spatter that fall into the first and second preheating furnaces 2. and 3. However, in the reflow welding equipment described above, because a flow is mixed in the weld in the form of coated cream on the printed board for the purpose of improving the effectiveness of the weld, the flow is partially evaporated in a hot gas when the cream-shaped solder is melted with the hot air at high temperature discharged from the heating nozzle 14b. The hot air inclusive of the flow that has been converted to a gas when it is inserted by the fan 17 decreases in temperature during travel from the circulation duct 16 to the fan 17, causing the gaseous flow to become a highly viscous liquid or a solid and being fixed to the interior of the circulation duct 16, to the fan 17 or to the reflow oven 14. Therefore, the assimilation efficiency and the fan relief performance of the fan 17 are degraded, by which time it is not possible to send the desired quantity of hot air inside the reflow oven 14. Therefore, it will take a long time to heat the inside temperature of the reflow oven 14 to a desired high temperature, resulting in increased energy consumption. Likewise, the temperature of the high temperature hot air discharged from the reflow oven 14 varies with the result that the cream-shaped solder coated on the printed board will be non-uniformly melted and the welding performance will be degraded. Moreover, the circulation duct 16 and the fan 17 require maintenance that includes disassembly and cleaning in a short period of time to remove the flow that remains on the inside of the circulation duct 16 and the fan 17; therefore the speed of operation of the reflow welding equipment will decrease to degrade the productivity of the equipment. Since the vent cover 15 and the fan 17 are connected through the extended circulation duct 16, the high temperature hot air entering from the relief cover 15 decreases as it passes through the circulation duct to be recharged at the reflow oven 14 through fan 17.

BRIEF DESCRIPTION OF THE INVENTION As a first means to solve the above-described problem, a reflow soldering method of the present invention comprises the steps of supplying the outside air by means of the vent member within the heat exchange member in which the exchange of heat takes place. heat between outside air and indoor air of different temperatures to decrease the temperature difference; heating the heat exchange member supplied with the outside air by using the hot air discharged from the heating member to raise the temperature of the supplied outside air within the heat exchange member; supplying the outside air in this heated manner to the heating member; further heating the outside air to a high temperature by the heating member; and discharging the high temperature hot air out of the heating member, thereby welding a circuit component to the printed board by using the high temperature heated air discharged in this manner.

As a secondary means for solving the problems described above, the reflow soldering method of the present invention also includes absorbing the heat of the hot air discharged from the heating member by the outside air in the heat exchange member, to decrease thus the temperature of the hot air present in the vicinity of the heat exchange member outside the heat exchange member. Moreover, as a third means to solve the problems described above, the reflow welding equipment of the present invention comprises a conveyor member for carrying a printed board assembled with a circuit component and coated with solder in the form of a cream, a member of ventilation for supplying the outside air to the interior, a heat exchange member for introducing the outside air from the vent member to the interior, and a heating member for heating the outside air being supplied from the vent member through of the heat exchange member. The heat exchange member is disposed in a position in which hot air heated in the heating member is discharged. Moreover, as a fourth means to solve the problem described above, the reflow welding equipment of the present invention is constituted in such a way that the heat of the high temperature hot air discharged from the heating member is brought out and cooled by the outside air fed into the heat exchange member. To collect and discharge the air in this cooled form, the relief member is provided. The heat exchange member is arranged in the relief member. Moreover, as a fifth means of the present invention to solve the problem described above, the heat exchange member is disposed on the opposite side of the heating member below the transporting member. Further, as a sixth means of the present invention to solve the problem described above, the heat exchange member is comprised of an air reservoir that is collectively formed of a plurality of tubes on both inlet and outlet sides; the outside air is fed from the vent member, through the air reservoir, then being fed to the heating member. Moreover, as a seventh means of the present invention to solve the problem described above, an air reservoir of the heat exchange member is comprised of a plurality of channels forming a corrugated surface.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a general block diagram of one embodiment of a reflow welding equipment according to the present invention; Figure 2 is a sectional view of a main portion of a first preheating furnace of the reflow welding equipment of Figure 1; Figure 3 is a sectional view of a main portion of a heating member of the reflow welding equipment of Figure 1; Figure 4 is a schematic perspective view of a heat exchange member of the reflow welding equipment of Figure 1; Figure 5 is a schematic perspective view of another embodiment of the heat exchange member of Figure 4; Figure 6 is a perspective view explaining the hot state of a printed board heated by the heating member of Figure 3; and Figure 7 is a general block diagram of conventional reflow welding equipment.

DESCRIPTION OF THE PREFERRED MODALITIES The reflow soldering equipment of the present invention will be explained with reference to Fig. 1 to Fig. 6. The same members as those used in the reflow soldering equipment of the related art described above will be designated by them. reference numbers and explained. Figure 1 is a general block diagram of a reflow welding equipment embodiment according to the present invention, in which a conveyor member 1 is arranged to carry a printed board P from the feed side A to the side B of download. The conveyor member 1 is for example comprised of the endless chain conveyor, the drive motor lb for driving the chain conveyor and a conveyor rail for guiding the chain conveyor from below so that the chain conveyor does not it is sent downwards with the weight of a part that is being carried, and is designed to travel, with the rotation of the drive motor lb, in the direction of arrow C, that is, from the side A of power on the side upstream to discharge side B on the downstream side. The chain conveyor is directed once out of the reflow welding equipment on the supply side A and on the discharge side B, and is then directed back to the reflow welding equipment after being guided by a plurality of guide rollers le. The chain conveyor is further routed in the lower part of the interior of the reflow welding equipment, and then wound on the drive motor pulley Ib to repeat the stroke with the rotation of the drive motor Ib. In the reflow soldering equipment in which the chain conveyor 1 runs, the first preheating furnace 2 and the second preheating furnace 3 are arranged on the upstream side to preheat the printed board P. The first preheating furnace 2 it is housed in case 2a, whose interior is divided into two chambers. In both chambers are mounted a pair of fans 2b, each having a rotary arrow 2c projecting downwards. Six infrared heaters 2d are arranged on top of any of the pair of fans 2b. In the first preheating oven 2, as shown in figure 2, the air in the case 2a is fed upwards with the rotation of the fan 2b. The heated air in the infrared heater 2d has a temperature of about 150 ° C. After preheating of the printed board P mounted with a circuit component Pl and coated with cream-shaped solder, the preheated air with a temperature of approximately 150 ° C strikes the surface of the upper wall of the case 2a, being reflected to circulate at a uniform temperature of about 150 ° C inside the case 2a.

Therefore, the air inside the case 2a is maintained at a uniform temperature; that is, there is no temperature difference between the upper part and the lower part, so the printed board P can be heated to a uniform temperature. The second preheating furnace 3 located on the downstream side of the first preheating furnace 2 has the same constitution as the first preheating furnace 2 and will therefore not be described. Under the conveyor member 1 on the downstream side of the second preheating furnace 3 the heating member 4 is disposed. The heating member 4 has a heater box 4a disposed immediately below the chain conveyor la. In the upper part of the heater box 4a, a plurality of heating nozzles 4b are arranged at a predetermined spacing, for example with a pitch of approximately 20 mm, along the direction of travel, in the direction of the arrow C of the chain conveyor la. The heating nozzle 4b having an opening of approximately 50 mm × 5 mm is arranged longitudinally at right angles to the travel direction of the chain conveyor la. In the heater box 4a, as shown in Figure 3, a plurality of heaters 4c and a plurality of sprinkler nozzles 4d with a number of small diameter holes not illustrated formed face-down on the top of the heaters 4c, are embedded in order from below on a side wall of the heater box 4a. Similarly, a thermocouple 4e for measuring the temperature in the heater box 4a is embedded in the other side wall opposite the first side wall in which the heater 4c and the spray nozzle 4d are embedded. A 4g air filter is mounted between the thermocouple 4e and an upper cover 4f to cover the upper part of the heater box 4a, in which a multitude of heating nozzles 4b are formed, to thereby reduce the turbulence of the air flow when the air blown out of the spray nozzle 4d and heated to a high temperature in the heater 4c flows into the heating nozzle 4b. Directly above the heating nozzle 4b of the heating member 4 is the chain conveyor la. Also on top of the chain conveyor is disposed at a predetermined distance a box-shaped relief member 5 which is open at the bottom. The relief member 5 is connected to the relief duct 6 through which the high temperature heated air coming from the heating nozzle 4b is collected and discharged. The heat exchange member 7 is mounted within the relief member 5, on the carrier member 1 and opposite the heating member 4 below the member of the conveyor member 1. The heat exchange member 7 is designed in such a manner that the exchange of heat is made between the outside air and the interior air that are at different temperatures, thus reducing the temperature difference between the outside air and the interior air. The heat exchange member 7 has a constitution such that, as shown in Figure 4, a plurality of round tubes 7a are assembled with a predetermined space provided therebetween to form the air reservoir 7b; and the round tubes 7a are assembled on any of the input 7c and output 7d sides. The input side 7c is connected to the air supply duct 8a, while the output side 7d is connected to the supply duct 7e. The supply duct 7e, as shown in Figure 1, is connected to the heating member 4 from the heat exchange member 7. The air supply duct 8a connected to the inlet side 7c of the heat exchange member 7 it is extended from the ventilation member 8 comprising the fan and others arranged below the heating member 4 and connected. In the vent member 8, the air inlet port 8b is equipped with the filter 8c to receive clean outside air with removed soils, and then send the outside air from the discharge port 8d * to the heating member 7 through of the air supply duct 8a. Moreover, on the downstream side of the reflow oven 4, the cooling fan 9 having a plurality of flow straightening plates 9a is disposed on the chain conveyor 1. Similarly, the receiving mesh of falling object 10 is disposed in the first and second heating furnaces 2 and 3 for receiving unnecessary objects such as weld spatter falling from the chain conveyor 1. That is, the backflow welding equipment of the present invention comprises a conveyor member 1 for carrying a printed P board assembled with a circuit component and coated with solder in the form of a cream, a vent member for supplying the outside air in the interior, a heat exchange member for introducing the outside air coming from the member of ventilation 8 towards the inside and a heating member 4 for heating the outside air that is supplied from the member of 0 ve ntilation 8 through the heat exchange member 7. The heat exchange member 7 is disposed in a position in which the hot air 11 heated in the heating member 4 is discharged. In the reflow welding equipment of the present invention of the constitution described above, the printed board P mounted with a circuit component Pl and coated with solder in the form of cream is carried by the conveyor member from the feed side A; when the printed board P is preheated in the first and second preheating furnaces 2 and 3, the printed board temperature increases to approximately 120-150 ° C. The preheated printed board P is carried over the multitude of heating nozzles 4b of the heating member 4, the heated air 11 heated to a temperature as high as about 300 ° C in the center, is applied from the heating nozzles 4b to the side of the bottom surface of the printed board P as shown in figure 6, thus raising the temperature of the printed board P to approximately 200-250 ° C on the side of the lower surface. Then, the cream-shaped solder coated on the lower surface of the printed board P is melted to produce an electrically conductive condition between the circuit component Pl and a circuit pattern not illustrated on the printed board P. The printed board P with the solder in the form of melted cream, when carried by the carrier member 1 to the downstream side, is sent from the heating member 4 to the cooling fan 9, where the printed board P is cooled with the air coming from the flow straightening plates 9a. In this way, the solder in the form of a cream is set to connect the circuit component Pl to the circuit pattern not illustrated. The hot air 11 that has been discharged upwards from the heating nozzles 4b and that has melted the solder in cream form, it is cooled by absorption of heat by the outside air being fed into the heat exchange member 7. The air thus cooled is collected and discharged by the relief member 5 out of the reflow welding equipment. The heat exchange member 7 is disposed in the relief member 5. In the heat exchange member 7, the air reservoir 7b having a plurality of tubes 7a is formed. The heat of the hot air 11 which is discharged upwards from the heating nozzle 4b of the heating member 4 is absorbed by the outside air supplied from the ventilation member 8 in the air reservoir 7b of the heat exchange member 7, decreasing the temperature of the hot air 11 outside the heat exchange member 7. The outside air supplied from the vent member 8 in the heat exchange member 7 takes the heat coming from the hot air 11, thus raising its temperature from 100 to 150 ° C in the air tank 7b. The outside air in the air reservoir 7b which has risen from 100 to 150 ° C is forced, by the fresh outside air coming in from the vent member 8 through the air duct 8a, from the supply duct 7e to the heater box 4a of the heating member 4. The outside air in this heated manner that has been sent to the heater box 4a is blown outwards towards the heater 4c from a plurality of not illustrated holes in the sprinkler nozzle 4d. Then, the outdoor air further raises its temperature to about 300 ° C, becoming hot air at a high temperature 11 as shown in figure 6. The hot air 11 is discharged upwards from the heating nozzle 4b. Subsequently, the printed board P which has been carried on the conveyor member 1 is heated by the hot air at high temperature 11 to approximately 200 to 250 ° C on the lower surface of the printed board P, in order to melt the weld in the form of cream coated on the undersurface of the printed board P "Moreover, since the heat exchange member 7 is disposed on the opposite side of the heating member 4 which is below the transport member 1 in the relief member 5, the heat of the hot air 11 which has been discharged out of the heating member 4 and which has melted the solder in the form of cream is efficiently absorbed, thus decreasing the temperature of the hot air 11 present outside of, and in the vicinity of, the limb heat exchange 7. The circuit component Pl on the printed board P, therefore, can be protected from heating and damage. In the embodiment of the present invention, the air reservoir 7b of the heat exchange member 7 comprising an assembly of a plurality of round tubes 7a has been explained so far.; however, the tubes 7a are not limited to the round shape but may have other shapes, for example an oval shape. Moreover, it should be noted that the air reservoir 7b of the heat exchange member 7 is not limited to the plurality of tubes 7a, but that the air reservoir 7b as shown in Figure 5 may be comprised of a plurality of portions. channel channel undulating and be hollow in the interior. According to the present invention described so far, a reflow soldering method comprises supplying the outside air by means of the vent member inside the heat exchange member, where heat exchange takes place between the outside air and the indoor air of different temperatures to decrease the temperature difference; heating the heat exchange member supplied with the outside air by using the hot air discharged from the heating member; supplying the outside air in this heated manner to the heating member; further heating the outside air to a high temperature by means of the heating member; and discharging the high temperature hot air out of the heating member, by soldering a circuit component to the board printed with the hot air at high temperature in this discharged manner. Therefore, the heat of the high temperature hot air discharged from the heating member is efficiently absorbed in the heat exchange member, thus raising the temperature of the external air supplied in the heat exchange member in a short period of time. In this way, it becomes possible to supply the hot outdoor air to the heating member. The outside air that will be supplied to the heating member, which is hot, can be easily heated to a high temperature by the heating member in a short time, thus uniformly melting the coated cream-shaped solder on the printed board and consequently ensuring a high reliability welding result. Moreover, the heat of the hot air discharged from the heating member is absorbed by the outside air in the heat exchange member, to thereby lower the temperature of the hot air outside the heat exchange member. Therefore, it is possible to prevent the circuit component loaded on the printed board from becoming hot and thermally damaged. In addition, the reflow welding equipment comprises a conveyor member for carrying a printed board assembled with a circuit component and coated with solder in the form of a cream, a vent member for supplying the outside air inwardly, an exchange member for heat for introducing the outside air coming from the vent member inwards, and a heating member for heating the outside air being supplied from the vent member through the heat exchange member. The heat exchange member is disposed in a position in which hot air heated in the heating member is discharged. Therefore, the heat of the high temperature hot air being discharged from the heating member is absorbed, to thereby efficiently heat the outside air being fed into the heat exchange member and feed the outside air in this heated manner to the heating member. Therefore, it is possible to provide a low energy consumption reflow soldering equipment which can decrease the electric capacity of the heater to heat the heating member. Moreover, it is possible to provide a reflow welding equipment having improved time efficiency and high productivity, in which the outside air that will be supplied from the ventilation member is clean air and therefore does not settle neither flow nor dust inside the ventilation member and the heating member. Thus, it is possible to prolong the maintenance time of the equipment. The high temperature hot air discharged from the heating member is cooled by heat absorption by the outside air fed into the heat exchange member. To gather and discard the chilled air outward, the relief member is provided. The heat exchange member is arranged in the relief member. Therefore, it is possible to efficiently absorb the heat coming from the hot air at high temperature and to heat the outside air fed in the heat exchange member to a high temperature in a short period of time. In addition, the heat exchange member that is disposed on the opposite side of the heating member below the conveyor member, can efficiently absorb the heat that comes from the hot air at high temperature after melting the coated cream-shaped solder on the board printed, to thus cool the hot air at high temperature, thus preventing the circuit component loaded on the printed board from heating up and being thermally damaged. Likewise, the heat exchange member is comprised of an air reservoir comprising an assembly of a plurality of tubes that are assembled at the inlet and outlet sides to cause the outside air being supplied from the reservoir member. ventilation, pass the heating member through the air tank. Therefore, it is possible to efficiently absorb the heat that comes from the hot air at high temperature in order to heat up to a high temperature the outside air fed into the air tank in a short time. The air reservoir of the heat exchange member is comprised of a plurality of channel portions having a corrugated surface; therefore, the air reservoir can be increased in a surface area to efficiently absorb the heat of the hot air at high temperature, thus heating, in a short period of time, up to a high temperature the fresh air supplied in the reservoir of air.

Claims (14)

NOVELTY OF THE INVENTION CLAIMS

1. - A method of reflow welding comprising the steps of: supplying the outside air by means of a ventilation member in a heat exchange member in which the exchange of heat between the outside air and the indoor air of different heat takes place temperatures to decrease a difference in temperatures; heating said heat exchange member supplied with the outside air by using the hot air discharged from a heating member to raise the temperature of the outside air supplied within said heat exchange member; supplying the outside air in this heated manner to said heating member; further heating the outside air to a high temperature by means of said heating member; and discharging the high temperature hot air out of said heating member, thereby welding a circuit component to a printed board by using the high temperature hot air discharged in this manner.

2. A method of reflow welding according to claim 1, further characterized in that the heat of the hot air discharged from said heating member is absorbed by the outside air in said heat exchange member, to thereby lower the temperature of the hot air present in the vicinity of said heat exchange member outside said heat exchange member.

3. A reflow welding equipment comprising: a conveyor member for carrying a printed board assembled with a circuit component and coated with solder in the form of a cream; a ventilation member to supply the outside air inwards; a heat exchange member for introducing the outside air coming from a ventilation member in the interior; and a heating member for heating the outdoor air that is being supplied from said vent member through said heat exchange member, said heat exchange member being disposed in a position in which the air heated by said heat Heating is discharged.

4. A reflow welding equipment according to claim 3, further characterized in that the high temperature hot air discharged from said heating member is cooled by absorption of heat by the external air fed into said heat exchange member; a venting member is also provided to collect and discharge the cooled air in this manner; and said heat exchange member is disposed in said relief member.

5. A reflow welding equipment according to claim 4, further characterized in that said heat exchange member is disposed on the opposite side of said heating member below said conveyor member.

6. A reflow welding equipment according to claim 5, further characterized in that said heat exchange member comprises an air reservoir, which is collectively formed of a plurality of tubes on both outlet and inlet sides; and the outside air is fed from said vent member, through said air reservoir, then being fed to said heating member.

7. A reflow welding equipment according to claim 6, further characterized in that said air reservoir of said heat exchange member comprises a plurality of channel portions having a corrugated surface.

8. A reflow welding equipment according to claim 4, further characterized in that said heat exchange member comprises an air reservoir, which is collectively formed of a plurality of tubes on both inlet and outlet sides; and the outside air is fed from said ventilation member, through said air reservoir, then being fed to said heating member.

9. A reflow welding equipment according to claim 8, further characterized in that said air reservoir of said heat exchange member comprises a plurality of channel portions having a corrugated surface.

10. A reflow welding equipment according to claim 3, further characterized in that said heat exchange member is disposed on the opposite side of said heating member, below said conveyor member.

11. A reflow welding equipment according to claim 10, further characterized in that said heat exchange member comprises an air reservoir, which is collectively formed of a plurality of tubes on both inlet and outlet sides; and outside air is fed from said vent member, through said air reservoir, then being fed to said heating member.

12. A reflow welding equipment according to claim 11, further characterized in that said air reservoir of said heat exchange member comprises a plurality of channel portions having a corrugated surface.

13. A reflow welding equipment according to claim 3, further characterized in that said heat exchange member comprises an air reservoir, which is collectively formed of a plurality of tubes on both inlet and outlet sides; and outside air is fed from said vent member, through said air reservoir, then being fed to said heating member.

14. A reflow welding equipment according to claim 13, further characterized in that said air reservoir of said heat exchange member comprises a plurality of channel portions having a corrugated surface.