Patent Description:
Currently, as a technique for mounting various electronic products (e.g., IC chips) on a circuit board, a soldering process is widely known. With a typical soldering process, first, solder paste is printed in place on a circuit board. Next, electronic products are mounted on the circuit board. Then, the circuit board is heated and cooled in this order in a soldering apparatus called a reflow furnace.

Conventional techniques for cooling the circuit board include a cooling apparatus disclosed in PTL <NUM>. The conventional cooling apparatus adopts a scheme for supplying cooling gas from above and below. The conventional cooling apparatus includes left and right rails for transporting circuit boards, and left and right inlet channels combined with the left and right rails. The inlet channels extend in an up-and-down direction of the cooling apparatus on lateral sides of the left and right rails.

The left and right inlet channels are linked to upper and lower recovery channels. The upper recovery channel recovers cooling gas above the left rail after the cooling gas is blown from above a circuit board and then moved to the left of the circuit board. The lower recovery channel recovers cooling gas below the left rail after the cooling gas is blown from below the circuit board and then moved to the left of the circuit board. The upper recovery channel and the lower recovery channel merge into a single channel downstream of the recovery channels. The right inlet channel is similar in configuration to the left inlet channel.

PTL <NUM> discloses a cooling apparatus that adopts the same gas supply scheme as PTL <NUM>. PTL <NUM> discloses a cooling apparatus that uses a scheme of supplying gas from above (down blow scheme). The cooling apparatus of PTL <NUM> includes cooling fins provided between a stirring fan and rails and configured to cool the gas supplied from above to be blown onto a circuit board. PTL <NUM> discloses an apparatus by which gas supplied from above is heated using a heater and blown onto a circuit board.

A case will now be considered in which two or more circuit boards are cooled by being transported successively on the cooling apparatus of PTL <NUM>. In this case, part of the cooling gas supplied from above the cooling apparatus is expected to move to below the cooling apparatus through a gap between two adjacent circuit boards. Conversely, part of the cooling gas supplied from below the cooling apparatus is expected to move to above the cooling apparatus.

Then, a flow of the cooling gas is disturbed in places where different flows of gas collide with each other, and consequently oxygen gas may flow in from outside the reflow furnace. This problem can also occur with the cooling apparatus of PTL <NUM>. With the cooling apparatus of PTL <NUM>, the cooling gas moves to above a cooling zone in places where a circuit board is present, but otherwise moves to below the cooling zone. Therefore, a state of circulation of the cooling gas in the cooling zone varies greatly depending on the presence or absence of a circuit board, and the above-mentioned inflow of oxygen gas from outside the furnace may occur. The oxygen gas from outside the furnace might cause oxidation of a soldering area. Thus, there is demand for improvements intended to cool the soldering area while curbing disturbances in the flow of cooling gas in the cooling apparatus.

With the cooling apparatus of PTL <NUM>, the channel resulting from the merging of the upper and lower recovery channels is formed outside the cooling zone. Consequently, the cooling gas flowing through the resulting channel may be cooled by an inner wall surface of the resulting channel. When the cooling gas is cooled by the inner wall surface, there may arise a trouble in which flux contained in the cooling gas will condense and attach to the inner wall surface. Thus, there is demand for improvements also from the viewpoint of curbing liquefaction of flux in the cooling zone and thereby improving flux recovery efficiency outside the cooling zone.

Prior art document <CIT> discloses a refluxing soft soldering apparatus that is configured to blow hot air from upper side and lower side of a circuit board in a heated air circulation apparatus, wherein electronic components are soldered on the circuit board in soft soldering mode, the heated air circulation apparatus has an upside circulating system and a lower side circulating system, the upside circulating system has a blast blower, a hot air blow-out device, a suction pipe and a discharging pipe; the lower side circulating system includes a blast blower, a hot air blow-out device and a discharging pipe; the blast blower of the upside circulating system and the blast blower of the lower side circulating system are driven by a common motor, and are configured in a furnace at the lower side of the conveyor. They can also be configured in the following mode, namely, the blast blower of the upside circulating system and the blast blower of the lower side circulating system are configured in a furnace at the upside of the conveyor, and the motor is configured at the upside of the furnace.

Prior art document <CIT>- <CIT> shows an apparatus and method in which power consumption is reduced and in which a circuit board can be heated stably to a prescribed temperature. This heating apparatus is provided with a conveyance part which conveys a circuit board on which an electronic component is mounted. In addition, it is provided with preheating chambers and heating chambers adjacent to one another in which the conveyance part is contained, in which solder for reflow is heated on the circuit board and melted or in which an adhesive for electronic-component fixation is hardened. In addition, it is provided with a cooling chamber which is adjacent to the rear part in the conveyance direction of the heating chamber, and in which the molten solder for reflow is cooled and solidified. In addition, it is provided with at least one, out of shielding plates, which is situated just above rail parts in the conveyance part and which is situated in the boundary between the respective chambers.

Prior art document <CIT> describes a reflow soldering device that is configured to prevent contamination of the soldering device and to facilitate washing of a substrate by cooling, liquefying and separating flux gas contained in gas by a high pressure part, of inert gas god out of a blower. A substrate is carried to a reflow soldering chamber RF from a preheating chamber, comes into contact with heated nitrogen gas and cream solder is melted, and electronic parts are soldered to the substrate. When the substrate is heated, flux evaporates from the cream solder, and is mixed with nitrogen gas. This nitrogen gas is fed by pressure to a flux collecting device by e blower, comes into contact with a cooling pipe and is cooled. The flux contained in the gas is liquefied and separated from the gas, stored in a bottom part of the flux collecting device, and collected through a flux collecting pipe. The nitrogen gas from which the flux is separated is returned to the upper part of a heating device.

Prior art document <CIT> discloses a cooler for a soldered board, that is configured to easily regulate the temperature falling speed of a board in a cooler for a soldered high-temperature board. A cooling chamber body of a cooler is disposed at the board delivering side of a reflowing unit R. A high-temperature board is cooled with cold winds generated by a fan in the body and a cooling fin cooler. A plurality of cooling fluid blowing nozzle tube is laterally provided at the upstream side of a board conveyer, and a cooling fluid outlet is provided at the board opposite side. The tube is rotatably mounted by a swivel joint. A flow regulating valve for variably regulating the flow rate of the cooling fluid (nitrogen gas) to be supplied to the tube is provided at an external cooling fluid supply tube. The tube is rotated by the joint to regulate the cooling fluid flowing angle, and the cooling fluid flowing rate is regulated by the valve, thereby regulating the temperature falling speed of the board.

An object of the present invention is to provide a soldering apparatus capable of curbing disturbances in flow of cooling gas in a cooling apparatus when two or more circuit boards are cooled by being transported successively. Another object of the present invention is to provide a soldering apparatus capable of improving recovery efficiency for flux contained in cooling gas outside a cooling zone.

The object underlying the present invention is achieved by a soldering apparatus according to independent claim <NUM>. Preferred embodiments are defined in the respective dependent claims.

According to the present invention the proposed soldering apparatus realizes the following features.

The soldering apparatus comprises a cooling zone, an upper vent hole, a lower vent hole, an external channel, a blower unit, a heat exchanger, a pair of bypass channels, and a ventilation plate.

The cooling zone cools a board subjected to a soldering process.

The upper vent hole is provided above a pair of rails configured to transport the board in the cooling zone.

The lower vent hole is provided below the pair of rails in the cooling zone.

The external channel connects the upper and lower vent holes with each other outside the cooling zone.

The blower unit is communicated with the upper vent hole. The blower unit causes gas in the external channel to flow through the upper vent hole, the cooling zone, and the lower vent hole in order and return to the external channel.

The heat exchanger is provided in a lower opening linked to the lower vent hole below the pair of rails. The heat exchanger cools gas passing through the lower opening.

The pair of bypass channels are provided in parallel to the pair of rails on lateral sides of the pair of rails. The bypass channels deliver gas above the pair of rails to the lower opening while bypassing locations of the pair of rails.

The ventilation plate is provided in a space formed between the pair of bypass channels below the pair of rails. The ventilation plate has a slit used to send gas below the pair of rails to the lower opening.

According to a second embodiment, the soldering apparatus further has the following features.

The pair of bypass channels each include an inlet port, a discharge port, and a bend, the inlet ports being located above the pair of rails, the discharge ports being located below the ventilation plate, the bends bending outward from inside the pair of rails in the locations of the pair of rails.

The discharge ports are located below the ventilation plate and above the lower opening.

According to a third embodiment, the soldering apparatus further has the following features.

One of the inlet ports faces another of the inlet ports.

One of the discharge ports faces another of the discharge ports.

According to a fourth embodiment, the soldering apparatus further has the following features.

A width of the pair of bypass channels in a transport direction of the board is approximately equal to a width of the ventilation plate in the transport direction.

The slit is formed in a direction orthogonal to the transport direction of the board.

According to a fifth embodiment, the soldering apparatus further has the following features.

The upper vent hole is provided in a furnace side wall surface serving as a side wall surface of the cooling zone.

The blower unit includes a blower fan, a fan inlet zone, and a fan outlet zone. The blower fan is provided on a furnace ceiling wall surface serving as a ceiling wall surface of the cooling zone. The fan inlet zone extends from the upper vent hole to a wall surface facing the furnace side wall surface, and causes gas to flow toward the blower fan from the upper vent hole. The fan outlet zone is provided surrounding the fan inlet zone and causes gas to flow toward the cooling zone from the blower fan.

According to a sixth embodiment, the soldering apparatus further has the following features.

An outlet zone bottom wall surface serving as a bottom wall surface of the fan outlet zone faces a board transport surface formed between the pair of rails. A large number of vent holes are formed at equal intervals in the outlet zone bottom wall surface.

According to a seventh embodiment, the soldering apparatus further has the following features.

The soldering apparatus further comprises a branch channel and a recovery unit.

The branch channel branches off from the external channel at a midpoint of the external channel.

The recovery unit is connected to the branch channel. The recovery unit recovers flux in a liquid state.

According to an eighth embodiment, the soldering apparatus further has the following features.

The recovery unit includes a storage and a connector connecting the storage to the branch channel.

A branch point of the branch channel in the external channel is located directly below the lower vent hole.

The storage is provided below the branch point.

A channel connecting the branch point and the storage with each other is inclined downward from the branch point to the storage.

According to the invention, when a board is present above the heat exchanger, much of the gas above the pair of rails can be delivered to the heat exchanger through the pair of bypass channels. On the other hand, when no board is present above the heat exchanger, much of the gas above the pair of rails can be sent to the heat exchanger through the slit. Thus, when two or more boards are transported successively, it is possible to cool the boards while curbing disturbances in the flow of gas existing between the pair of rails.

According to the second embodiment, since the discharge ports are located below the ventilation plate and above the lower opening, length of the bypass channels can be shortened. By shortening the length of the bypass channels, it is possible to supply gas to the heat exchanger while keeping the gas flowing through the bypass channels from being cooled by inner wall surfaces of the bypass channels. This makes it possible to cool the gas passing through the bypass channels reliably in the heat exchanger and thereby efficiently recover the flux contained in the gas downstream of the heat exchanger.

According to a third embodiment, when a board is present above the heat exchanger, much of gas flowing to lateral sides of the board can be drawn in through the inlet ports and discharged to below the ventilation plate through the bends and the discharge ports. The gas discharged to below the ventilation plate merges with gas passing through the slit. This can cause disturbances of gas below the ventilation plate. However, because the disturbances are blocked by the ventilation plate, the flow of the gas existing between the pair of rails is rarely disturbed. Thus, it is possible to cool the boards while curbing disturbances in the flow of gas existing between the pair of rails.

Spacing between the pair of rails is adjusted according to size of the boards. That is, the spacing is increased when boards having a large width in the direction orthogonal to the transport direction are cooled, and the spacing is reduced when boards having a small width are cooled. Consequently, if the slit is formed in parallel to the transport direction, disturbances in the flow of gas may increase around the slit depending on the spacing between the pair of rails. In this respect, according to the fourth embodiment, since the slit is formed in the direction orthogonal to the transport direction, occurrence of troubles with adjustment of the spacing between the pair of rails can be reduced compared to when the slit is formed in parallel to the transport direction.

According to the fifth embodiment, the gas flowing into the blower unit from the external channel through the upper vent hole can be sent out to the cooling zone by flowing through the fan inlet zone, the blower fan, and the fan outlet zone in this order. Here, the upper vent hole is provided in the furnace side wall surface. The blower fan is provided in the furnace ceiling wall surface. The fan outlet zone is provided surrounding the fan inlet zone. Therefore, such a relative arrangement allows an orientation of the gas flowing into the blower unit through the furnace side wall surface to be changed in the blower unit and thereby allows the gas sent out from the blower unit to be orientated in a single direction moving from above to below the cooling zone. This makes it possible to stabilize the flow of gas existing between the pair of rails.

According to the sixth embodiment, a large number of vent holes are formed at equal intervals in the outlet zone bottom wall surface facing the board transport surface. Consequently, the gas flowing into the blower unit during operation of the blower unit can be moved toward the board transport surface by blowing out uniformly through the vent holes. This makes it possible to further stabilize the flow of gas existing between the pair of rails.

According the seventh embodiment, the flux in a liquid state produced by being condensed in the heat exchanger can be recovered by the recovery unit outside the cooling zone through the external channel and the branch channel.

According to the eighth embodiment, the channel connecting the branch point and the storage with each other is inclined downward from the branch point to the storage. This makes it possible to improve the efficiency with which the flux in a liquid state is recovered outside the cooling zone by the recovery unit.

A soldering apparatus (hereinafter also referred to as a "reflow furnace") according to an embodiment of the present invention will be described below with reference to the drawings. Note that components common among different drawings will be denoted by the same reference sings, and redundant description thereof will be omitted. Also, the present invention is not limited by the embodiment described below.

<FIG> is a diagram showing an overall configuration example of a reflow furnace according to an embodiment of the present invention. The reflow furnace <NUM> shown in <FIG> includes a conveyor <NUM>. The conveyor <NUM> includes a pair of rails <NUM> and 11R placed along a longitudinal direction of the reflow furnace <NUM>, and transports circuit boards CB (see <FIG>) mounted between the rails <NUM> and 11R in a transport direction BDD. Spacing between the rails <NUM> and 11R is adjusted according to size of the circuit boards CB. Solder paste is printed in place on the circuit board CB. Also, electronic products are mounted on the circuit board CB. A solder paste printing process and an electronic product mounting process are performed before a soldering process performed in the reflow furnace <NUM>.

The reflow furnace <NUM> also includes labyrinths <NUM> and <NUM>. The labyrinth <NUM> is provided at an inlet of the reflow furnace <NUM>. The labyrinth <NUM> has an internal structure that is made up of plural fin-like metal plates and the like. The internal structure prevents infiltration of outside air through the inlet of the reflow furnace <NUM>. The labyrinth <NUM> is provided at the inlet of the reflow furnace <NUM>. The labyrinth <NUM> is provided for the purpose of preventing infiltration of outside air through the outlet of the reflow furnace <NUM>.

The reflow furnace <NUM> further includes a heating zone <NUM>. The heating zone <NUM> includes, for example, preheating zones and peak heating zones. In the example shown in <FIG>, five zones on the inlet side (i.e., on the side of the labyrinth <NUM>) correspond to the former and the remaining three zones on the outlet side (i.e., on the side of the labyrinth <NUM>) correspond to the latter. However, the numbers of preheating zones and peak heating zones vary with the type of reflow furnace <NUM>.

In the preheating zone, circuit boards CB are heated in a relatively low temperature range. As a result of the heating in the preheating zone, the flux contained in the solder paste starts to evaporate. In the peak heating zone, the circuit boards CB are heated in a temperature range in which a solder component contained in the solder paste melts. The range of the preheating temperature and the range of the peak heating temperature are set appropriately according to solder component composition. Evaporation of the flux occurs not only in the preheating zone, but also in the peak heating zone. As the circuit boards CB are heated in the peak heating zone, the volatile components in the flux evaporate.

The reflow furnace <NUM> further includes a cooling zone <NUM>. In the example shown in <FIG>, the cooling zone <NUM> is divided into first and second zones. However, the total number of cooling zones <NUM> varies with the type of reflow furnace <NUM>. Therefore, the total number of cooling zones <NUM> may be <NUM>. In the cooling zone <NUM>, circuit boards CB are cooled. As the circuit boards CB are cooled in the cooling zone <NUM>, the solder component solidifies.

The cooling zone <NUM> is linked to the heating zone <NUM>. Consequently, part of the volatile components of the flux evaporating in the heating zone <NUM> flows into the cooling zone <NUM>. A configuration example of the cooling zone <NUM> and cooling operation for circuit boards CB in the cooling zone <NUM> will be described below.

<FIG> is a diagram showing an example of major components of the cooling zone <NUM> shown in <FIG>. As shown in <FIG>, the cooling zone <NUM> includes a cooling zone 40A and a cooling zone 40B. The cooling zone 40A and the cooling zone 40B are basically equal in configuration. Therefore, the cooling zone 40A will be described below representatively, and description of the cooling zone 40B will be omitted.

In the following description, <FIG> are referred to in order to supplement the description of <FIG>. <FIG> corresponds to a diagram of an upper part of the cooling zone <NUM> as viewed from the side of a conveyor <NUM> when the cooling zone <NUM> is cut along line <NUM>-<NUM> shown in <FIG>. <FIG> corresponds to a diagram obtained when the cooling zone 40A is cut along line <NUM>-<NUM> in <FIG> and viewed from the side of the cooling zone 40B (heating zone <NUM>). <FIG> corresponds to a diagram of the upper part of the cooling zone <NUM> as viewed from the side of the conveyor <NUM> when the cooling zone <NUM> is cut along line <NUM>-<NUM> shown in <FIG>. <FIG> corresponds to a diagram of a lower part of the cooling zone <NUM> as viewed from the side of the conveyor <NUM> when the cooling zone <NUM> is cut along line <NUM>-<NUM>. Note that "the upper part of the cooling zone <NUM>" and "the lower part of the cooling zone <NUM>" are shown relative to the position of the conveyor <NUM>.

In the example shown in <FIG>, blower units <NUM> are provided in an upper part of the cooling zone 40A. The blower units <NUM> are attached to a ceiling wall surface (hereinafter referred to as a "furnace ceiling wall surface) <NUM> of the cooling zone 40A. The blower units <NUM> draw in gas for cooling (e.g., nitrogen gas) from lateral sides. The blower units <NUM> send out the drawn gas downward. Each of the blower units <NUM> includes a blower fan <NUM>, a fan inlet zone <NUM>, and a fan outlet zone <NUM>.

The blower fan <NUM> is located below the furnace ceiling wall surface <NUM>. The blower fan <NUM> draws gas out of the fan inlet zone <NUM> and sends out the gas to the fan outlet zone <NUM>. In the example shown in <FIG>, the blower fan <NUM> includes baffles 91a and 91b. The baffles are provided to horizontally whirl the gas sent out from the blower fan <NUM> in the fan outlet zone <NUM>. The baffles 91a and 91b are arc-shaped in cross section and approximately equal in size. The baffle 91a extends toward a left-side wall surface (hereinafter referred to as a "furnace left-side wall surface") <NUM> of the cooling zone 40A from an outer edge of the blower fan <NUM> indicated by broken lines. On the other hand, the baffle 91b extends toward a right-side wall surface (hereinafter referred to as a "furnace right-side wall surface") 42R of the cooling zone 40A from the outer edge. Note that the "right side" and the "left side" are indicated with respect to the transport direction BDD.

Now, another configuration example of the blower fan will be described with reference to <FIG>. In this example, small baffles are added to the blower fan <NUM>. As shown in <FIG>, the blower fan <NUM> includes small baffles 91c and 91d. Purposes of installation of the small baffles are similar to those of the baffle 91a or 91b. The small baffles 91c and 91d are approximately equal in size. However, the small baffles 91a and 91b are smaller in cross section R and vertical size than the baffles 91a and 91b. Therefore, in the example shown in <FIG>, the gas sent out from the blower fan <NUM> flows along a surface of the baffle 91a (or baffle 91b) or flows along a surface of the small baffle 91c or (small baffle 91d). The latter flow produces a gas flow whirling in central part of the fan outlet zone <NUM>. The former flow produces a gas flow whirling outside the central part.

Returning to <FIG>, the description of the cooling zone <NUM> will be continued. The fan inlet zone <NUM> is marked off by side wall surfaces (hereinafter referred to as "inlet zone side wall surfaces") 92a and 92b, a bottom wall surface (hereinafter referred to as an "inlet zone bottom wall surface") 92d, and a ceiling wall surface (hereinafter referred to as an "inlet zone ceiling wall surface") 92e (see, in particular, <FIG> and <FIG>). In the example shown in <FIG>, a partition plate 92c is provided in the fan inlet zone <NUM>. The partition plate 92c faces the furnace right-side wall surface 42R. An installation position of the partition plate 92c is located close to that side face of the blower fan <NUM> which is farthest from the furnace right-side wall surface 42R. By installing the partition plate 92c in such a position, the gas flowing into the fan inlet zone <NUM> through an upper vent hole <NUM> is supplied evenly to a bottom of the blower fan <NUM>. The inlet zone bottom wall surface 92d is inclined downward from the partition plate 92c to the furnace right-side wall surface 42R. Note that the inlet zone bottom wall surface 92d does not necessarily have to be inclined in this way, and an entire area of the inlet zone bottom wall surface 92d may extend in a horizontal direction.

A reason for installing the partition plate 92c is to reduce the area of a wall surface placed in contact, in the fan inlet zone <NUM>, with the gas flowing in through the upper vent hole <NUM>, and thereby reduce the time required for maintenance including cleaning of the wall surface. Therefore, from a viewpoint other than maintenance efficiency, the partition plate 92c does not need to be provided. In that case, the inlet zone bottom wall surface 92d is connected to the furnace left-side wall surface <NUM> and is inclined downward therefrom to the furnace right-side wall surface 42R. The inlet zone bottom wall surface 92d becomes level in a location close to the furnace right-side wall surface 42R and is connected to the furnace right-side wall surface 42R.

The fan outlet zone <NUM> is provided surrounding the fan inlet zone <NUM>. As shown in <FIG> and <FIG>, the fan outlet zone <NUM> is marked off by side wall surfaces (hereinafter referred to as "outlet zone side wall surfaces") 93a and 93b, a bottom wall surface (hereinafter referred to as an "outlet zone bottom wall surface) 93c, the furnace ceiling wall surface <NUM>, and the furnace right-side wall surface 42R. The board passage zone 40a described above is a space formed below the outlet zone bottom wall surface 93c.

A gas outlet <NUM> shown in <FIG> corresponds to the fan outlet zone <NUM> in the cross section. The gas outlet <NUM> is configured to cause the gas whirling in the horizontal direction along a surface of the baffle 91a or 91b by being sent out from the blower fan <NUM> to move downward. The outlet zone bottom wall surface 93c is located below the gas outlet <NUM>. As shown in <FIG>, a large number of vent holes <NUM> are formed at equal intervals in the outlet zone bottom wall surface 93c. The gas in the fan outlet zone <NUM> is blown out through each of the vent holes <NUM>.

As shown in <FIG>, the outlet zone bottom wall surface 93c has a pent-roof shape that inclines gently downward from central part to the furnace right-side wall surface 42R and the furnace left-side wall surface <NUM>. A reason for this is that even if flux in a liquid state is produced in the outlet zone bottom wall surface 93c, the flux is expected to move to a position close to the furnace right-side wall surface 42R or the furnace left-side wall surface <NUM>. When the flux moves in this way, the flux is kept from dripping off the central part located right above the circuit board CB. Note that the shape of the outlet zone bottom wall surface 93c is not limited to this, and another shape may be used.

As shown in <FIG> and <FIG>, the upper vent hole <NUM> is provided in the furnace right-side wall surface 42R. A lower vent hole <NUM> is provided in a bottom wall surface (hereinafter referred to as a "furnace bottom wall surface") <NUM> of the cooling zone 40A. The lower vent hole <NUM> is connected with one end of an external channel <NUM>. The other end of the external channel <NUM> is connected with the upper vent hole <NUM>. That is, the upper vent hole <NUM> and the lower vent hole <NUM> are interconnected via the external channel <NUM>.

In the board passage zone 40a, a lower opening <NUM> is provided between the conveyor <NUM> and the lower vent hole <NUM>. The lower opening <NUM> is a space connecting the board passage zone 40a and the lower vent hole <NUM> with each other. A heat exchanger <NUM> is provided in the lower opening <NUM>. The heat exchanger <NUM> exchanges heat with gas passing therethrough and thereby cools the gas. Details of a configuration example centered around the heat exchanger <NUM> will be described in Item <NUM>-<NUM>.

As shown in <FIG>, a ventilation plate <NUM> is provided below the conveyor <NUM> and above the heat exchanger <NUM>. The ventilation plate <NUM> is made up of a flat metal plate. As shown in <FIG>, three slits <NUM> are formed at equal intervals in the ventilation plate <NUM>. A longitudinal direction of the slits <NUM> is orthogonal to the transport direction BDD. That is, the slits <NUM> are formed in a direction (hereinafter also referred to as a "transverse direction TRD") orthogonal to the transport direction BDD. Note that the total number of slits <NUM> is not limited to the example of <FIG>. That is, the total number of slits <NUM> may be less than or more than three. Also, a formation direction of the slits <NUM> may be a direction parallel to the transport direction BDD.

As shown in <FIG>, a bypass channel <NUM> that bypasses the location of the rail <NUM> is provided on a lateral side of the rail <NUM>. The bypass channel <NUM> inclines an inlet port 72a located above the rail <NUM>, a discharge port 72b located below the ventilation plate <NUM>, and a bend 72c. Gas above the rail <NUM> flows into the inlet port 72a and is discharged from the discharge port 72b. The bend 72c bends from inside to outside the rail <NUM> (to the side of the furnace left-side wall surface <NUM>) at the position of the rail <NUM>.

A bypass channel <NUM> having the same configuration as the bypass channel <NUM> is provided on a lateral side of the rail 11R. An inlet port 73a of the bypass channel <NUM> faces the inlet port 72a. A discharge port 73b of the bypass channel <NUM> faces the discharge port 72b. A bend 73c of the bypass channel <NUM> bends to outside the rail 11R (to the side of the furnace right-side wall surface 42R) at the position of the rail 11R.

The bypass channels <NUM> and <NUM> have a certain width in the transport direction BDD. As shown in <FIG>, the width of the bypass channels in the transport direction BDD is generally equal to the width of the ventilation plate <NUM> in the transport direction BDD. Also, as can be seen from <FIG>, the width of the ventilation plate <NUM> in the transverse direction TRD is generally equal to the distance between the bypass channels <NUM> and <NUM>. Actually, there is a gap between the bypass channel <NUM> or <NUM> and the ventilation plate <NUM>, and the gap is closed by a support plate provided below the ventilation plate <NUM>. In this arrangement, the ventilation plate <NUM> is provided in a space formed between the bypass channels <NUM> and <NUM>. As the ventilation plate <NUM> is provided at this position, the movement of gas in an up-and-down direction of the ventilation plate <NUM> is restricted by movement through the slits <NUM>.

As shown in <FIG>, the external channel <NUM> bifurcates at a halfway point. Specifically, the external channel <NUM> bifurcates directly below the lower vent hole <NUM>. A branch channel <NUM> extends from a branch point <NUM>. A terminal end of the branch channel <NUM> is connected to a connector <NUM> of a recovery unit <NUM>. Flux FX in a liquid state is stored in a storage <NUM> of the recovery unit <NUM>. The entire storage <NUM> is located below the branch point <NUM>. A channel connecting the branch point <NUM> and the storage <NUM> with each other (i.e., the branch channel <NUM> and the connector <NUM>) inclines downward from the branch point <NUM> to the storage <NUM>.

<FIG> is a diagram showing a configuration example centered around the heat exchanger <NUM> shown in <FIG>. In the example shown in <FIG>, the heat exchanger <NUM> includes a main body <NUM> and a refrigerant channel <NUM>. The main body <NUM> has an internal space, in which the refrigerant channel <NUM> is placed. The refrigerant channel <NUM> is provided being folded up by turning between opposite side faces of the main body <NUM>. The total number of refrigerant channels <NUM> may be either one or more than one.

Refrigerant (e.g., cooling water) supplied from outside the heat exchanger <NUM> circulates through the refrigerant channel <NUM>. A supply port 62a of the refrigerant channel <NUM> is provided in lower part of the heat exchanger <NUM> and a discharge port 62b of the refrigerant channel <NUM> is provided in upper part of the heat exchanger <NUM>. This results in formation of a refrigerant flow moving from below and above in the main body <NUM> by turning between opposite side faces of the main body <NUM>.

In the example shown in <FIG>, the lower opening <NUM> is made up of a small opening 47a that houses the main body <NUM> and a large opening 47b that has a larger diameter than the small opening 47a. The width of the large opening 47b is generally equal to the distance between the bends 72c and 73c. When gas in the bend 72c or 73c is discharged through the discharge port 72b or 73b, the discharged gas flows in the transverse direction TRD at the position of the large opening 47b.

The heat exchanger <NUM> is detachably mounted in the lower opening <NUM>. The heat exchanger <NUM> is connected to the furnace right-side wall surface 42R via a connection unit (not shown). Consequently, when the heat exchanger <NUM> is removed together with the connection unit, the heat exchanger <NUM> is separated from the cooling zone <NUM>.

<FIG> and <FIG> are diagrams explaining flows of gas in the cooling zone <NUM>. Note that <FIG> and <FIG> correspond to diagrams obtained when the cooling zone 40A is cut at the same position as in <FIG> and viewed from the side of the cooling zone 40B. A difference between <FIG> and <FIG> lies in the presence or absence of a circuit board CB. That is, a circuit board CB is illustrated in <FIG> and no circuit board CB is illustrated in <FIG>. The situation shown in <FIG> is typically observed when two or more circuit boards are cooled while being transported successively.

Arrows "GFD" in <FIG> and <FIG> indicate directions of gas flows produced in the cooling zone <NUM> when the blower unit <NUM> operates. The flows are described concretely as follows. That is, when the blower unit <NUM> is operated, the gas in the external channel <NUM> flows into the fan inlet zone <NUM> through the upper vent hole <NUM>. The gas flowing into the fan inlet zone <NUM> is sucked up by the blower fan <NUM> and sent out to the fan outlet zone <NUM>. The gas sent out to the fan outlet zone <NUM> flows through the fan outlet zone <NUM> by flowing outside the fan inlet zone <NUM> and moves to the outlet zone bottom wall surface 93c. The series of blowing operations of the blower unit <NUM> causes an orientation of the gas flowing into the blower unit <NUM> through the furnace right-side wall surface 42R to be changed in the blower unit <NUM> and causes the gas to be sent out from the blower unit <NUM> by being orientated in a direction moving from above to below the cooling zone 40A.

The gas reaching the outlet zone bottom wall surface 93c flows into the board passage zone 40a through the vent holes <NUM> (see <FIG>). As already described, the vent holes <NUM> are formed at equal intervals in the outlet zone bottom wall surface 93c. Consequently, the flow rate of the gas flowing into the board passage zone 40a through the vent holes <NUM> is generally uniform in a plane direction of the outlet zone bottom wall surface 93c.

In the example shown in <FIG>, the gas flowing into the board passage zone 40a through the vent holes <NUM> is blown onto the circuit board CB, thereby cooling the circuit board CB. The gas blown onto the circuit board CB changes orientation on the circuit board CB and flows around the circuit board CB. The gas flowing around the circuit board CB is broadly divided into gas flowing in the transport direction BDD and gas flowing in the transverse direction TRD.

The gas flowing in the transport direction BDD moves to the ventilation plate <NUM> by slipping through the sides of the circuit board CB. The gas reaching the ventilation plate <NUM> moves to the lower opening <NUM> through the slits <NUM>. The flow of gas before passing through the slits <NUM> is adjusted while passing through the slits <NUM>. Consequently, below the slits <NUM>, the direction (i.e., the direction from top to bottom) of the gas flow becomes constant. After passing through the slits <NUM>, the gas reaches the large opening 47b.

The gas flowing in the transverse direction TRD flows into the bend 72c (or the bend 73c) through the inlet port 72a (or the inlet port 73a) and is discharged through the discharge port 72b (or the discharge port 73b). In the bend 72c (or the bend 73c), the flow of gas is adjusted. Consequently, the gas discharged through the discharge port 72b (or the discharge port 73b) reaches the large opening 47b by spreading in the transverse direction TRD.

The gas reaching the large opening 47b is cooled by coming into contact with a surface of the refrigerant channel <NUM> when passing through the heat exchanger <NUM> (the internal space of the main body <NUM>). The cooled gas flows through the external channel <NUM> as a result of draw-in operation of the blower unit <NUM> and flows into the blower unit <NUM> (fan inlet zone <NUM>) through the upper vent hole <NUM>. Thus, the gas blown out from the outlet zone bottom wall surface 93c (vent holes <NUM>) by delivery operation of the blower unit <NUM> is low in temperature, and consequently the circuit board CB is cooled.

In the example shown in <FIG>, most of the gas flowing into the board passage zone 40a through the vent holes <NUM> moves as it is to the ventilation plate <NUM>. The flow of gas reaching the ventilation plate <NUM> is as described in <FIG>. Part of the gas flowing into the board passage zone 40a through the vent holes <NUM> reaches the large opening 47b through the bypass channel <NUM> or <NUM>. As can be seen when <FIG> and <FIG> are compared, the direction of the gas flow flowing into the board passage zone 40a through the vent holes <NUM> is constant regardless of the presence or absence of a circuit board CB above the heat exchanger <NUM>.

Oxygen gas may flow into the board passage zone 40a from outside the cooling zone <NUM>. The oxygen gas might cause oxidation of the soldering area on the circuit board CB. Also, if the flow of gas existing between the rails <NUM> and 11R is disturbed, during cooling of the circuit board CB, the soldering area and the like will be easily oxidized by oxygen mixed into the flow of gas.

In this respect, with the configuration of the reflow furnace according to the embodiment, when a circuit board CB is present above the heat exchanger <NUM>, much of the gas above the conveyor <NUM> can be sent to the large opening 47b through the bypass channels <NUM> and <NUM>. On the other hand, when no circuit board CB is present above the heat exchanger <NUM>, much of the gas above the conveyor <NUM> can be sent to the large opening 47b through the slits <NUM>. This makes it possible to always prevent the flow of gas existing between the rails <NUM> and 11R from being disturbed.

In particular, with the configuration of the reflow furnace according to the embodiment, since the discharge ports 72b and 73b are located below the ventilation plate <NUM> and above the lower opening <NUM>, length of the bypass channels <NUM> and <NUM> can be shortened. By shortening the length of the bypass channels <NUM> and <NUM>, it is possible to supply gas to the heat exchanger <NUM> while keeping the gas flowing through the bypass channels <NUM> and <NUM> from being cooled by the inner wall surfaces. This makes it possible to cool the gas passing through the bypass channels <NUM> and <NUM> reliably in the heat exchanger <NUM> and thereby efficiently recover the flux contained in the gas downstream of the heat exchanger <NUM>.

The gas discharged to below the ventilation plate <NUM> merges with the gas passing through the slits <NUM>. This can cause disturbances of gas below the ventilation plate <NUM>. However, because the disturbances are blocked by the ventilation plate <NUM>, the gas existing between the rails <NUM> and 11R is rarely disturbed. Thus, with the configuration of the reflow furnace according to the embodiment, it is possible to cool the circuit boards CB while curbing disturbances in the flow of gas existing between the rails <NUM> and 11R.

As already described, the spacing between the rails <NUM> and 11R is adjusted according to the size of the circuit boards CB. That is, when circuit boards CB having a large width in the transverse direction TRD are cooled, the spacing between the rails <NUM> and 11R is increased; and when circuit boards CB having a small width are cooled, the spacing is reduced. Consequently, if the slits <NUM> are formed in parallel to the transport direction BDD, disturbances in the flow of gas may increase around the slits <NUM> depending on the spacing between the rails <NUM> and 11R. In this respect, with the configuration of the reflow furnace according to the embodiment, since the slits <NUM> are formed in the transverse direction TRD, occurrence of troubles with adjustment of the spacing between the rails <NUM> and 11R can be reduced compared to when the slits <NUM> are formed in parallel to the transport direction BDD.

Also, the reflow furnace according to the embodiment allows the orientation of the gas flowing into the blower unit <NUM> through the furnace right-side wall surface 42R to be changed in the blower unit <NUM> and thereby allows the gas sent out from the blower unit <NUM> to be orientated in the direction moving from above to below the cooling zone <NUM>. This makes it possible to stabilize the flow of gas existing between the rails <NUM> and 11R.

Also, with the reflow furnace according to the embodiment, since the vent holes <NUM> are formed at equal intervals in the outlet zone bottom wall surface 93c, the gas flowing into the blower unit <NUM> can be sent out to the cooling zone <NUM> by blowing out uniformly through the vent holes <NUM>. This makes it possible to further stabilize the flow of gas existing between the pair of rails <NUM> and 11R.

Also, with the reflow furnace according to the embodiment, below the lower vent hole <NUM>, flux in a liquid state can be caused to flow through the branch point <NUM>, the branch channel <NUM>, and the connector <NUM> in this order. Thus, outside the cooling zone <NUM> (i.e., in the recovery unit <NUM>), the flux can be recovered efficiently.

Also, with the reflow furnace according to the embodiment, since the channel connecting the branch point <NUM> and the storage <NUM> with each other inclines downward from the branch point <NUM> to the storage <NUM>, the flux recovery efficiency of the recovery unit <NUM> can be improved.

Another example devised by the present inventors in the process of conducting studies for the present invention will be disclosed below as a reference example. Note that the same components as those of the above embodiment are denoted by the same reference signs as the corresponding components of the above embodiment, and description thereof will be omitted.

<FIG> is a diagram showing an example of major components of a cooling zone in a soldering apparatus according to a reference example. As shown in <FIG>, the cooling zone <NUM> includes a cooling zone 40C and a cooling zone 40D. The cooling zone 40C and the cooling zone 40D are basically equal in configuration. Therefore, the cooling zone 40C will be described below representatively, and description of the cooling zone 40D will be omitted.

In the following description, <FIG> are referred to in order to supplement the description of <FIG>. <FIG> corresponds to a diagram obtained when the cooling zone 40C is cut along line <NUM>-<NUM> in <FIG> and viewed from the side of the cooling zone 40D (heating zone <NUM>). <FIG> corresponds to a diagram obtained when the cooling zone <NUM> is cut along line <NUM>-<NUM> shown in <FIG> and the upper part of the cooling zone <NUM> is viewed from the side of the conveyor <NUM>. <FIG> corresponds to a diagram obtained when the cooling zone <NUM> is cut along line <NUM>-<NUM> shown in <FIG> and the lower part of the cooling zone <NUM> is viewed from the side of the conveyor <NUM>.

In the reference example, the blower units <NUM> are provided in the upper part of the cooling zone <NUM>. The configuration of the blower unit <NUM> and its surroundings is the same as that of the embodiment.

As shown in <FIG>, according to the reference example, the inlet zone bottom wall surface 92d becomes level in a location close to the furnace right-side wall surface 42R and is connected to the furnace right-side wall surface 42R. So far, the configuration is the same as that of the embodiment. According to the reference example, one end of a drain pipe <NUM> is connected to the level area. The drain pipe <NUM> discharges liquid-state flux produced in the fan inlet zone <NUM>, from the fan inlet zone <NUM>. A central axis of the drain pipe <NUM> extends in a vertical direction. The other end of the drain pipe <NUM> reaches the board passage zone 40a.

Below the drain pipe <NUM> in the board passage zone 40a, a drain slider <NUM> is detachably attached to a wall surface that makes up the board passage zone 40a. The drain slider <NUM> has a function to guide flux dripping off the drain pipe <NUM>, to the lower opening <NUM>.

As shown in <FIG>, the heat exchanger <NUM> is provided in the lower opening <NUM>. So far, the configuration is the same as that of the embodiment. According to the reference example, a filter <NUM> is provided on the heat exchanger <NUM>. The filter <NUM> is made up of a porous metal body having a three-dimensional network structure. The filter <NUM> has such a sectional shape (quadrangular in the example shown in <FIG>) that can be fitted in the lower opening <NUM>. Details of a configuration example centered around the heat exchanger <NUM> will be described in Item <NUM>-<NUM>.

<FIG> is a diagram showing a configuration example centered around the heat exchanger <NUM> shown in <FIG>. In the example shown in <FIG>, the heat exchanger <NUM> includes a main body <NUM> and a refrigerant channel <NUM>. Also, in the example shown in <FIG>, the lower opening <NUM> includes a small opening 47a and a large opening 47b. So far, the configuration is the same as that of the embodiment. According to the reference example, the filter <NUM> is provided in the large opening 47b. When the filter <NUM> is provided in the large opening 47b, an upper surface of the main body <NUM> is covered with the filter <NUM>. As the upper surface of the main body <NUM> is covered with the filter <NUM>, the gas in the cooling zone 40A flows into the internal space of the main body <NUM> always through the filter <NUM>. The filter <NUM> is detachably mounted in the lower opening <NUM>.

<FIG> is a diagram explaining flows of gas in the cooling zone <NUM> shown in <FIG>. Note that <FIG> corresponds to a diagram obtained when the cooling zone 40C is cut at the same position as in <FIG> and viewed from the side of the cooling zone 40D.

When the blower unit <NUM> is operated, the gas in the external channel <NUM> flows into the board passage zone 40a through the vent holes <NUM> (see <FIG>). The gas flowing into the board passage zone 40a through the vent holes <NUM> reaches an upper surface of the filter <NUM> by flowing from above to below the conveyor <NUM> while cooling the circuit boards CB.

The gas reaching the upper surface of the filter <NUM> flows into the filter <NUM>. Disturbances of gas before flowing into the filter <NUM> are smoothed out (rectification action of the filter <NUM>) while the gas is flowing through the filter <NUM>. Consequently, below a lower surface of the filter <NUM>, the direction (i.e., the direction from top to bottom) of the gas flow becomes constant. Also, the rectification action leads to a uniform flow rate of the gas below the lower surface of the filter <NUM> in the horizontal direction.

Claim 1:
A soldering apparatus (<NUM>),
comprising:
- a cooling zone (<NUM>, 40A, 40B) configured to cool a board (CB) subjected to a soldering process;
- an upper vent hole (<NUM>) provided above a pair of rails (<NUM>, 11R) configured to transport the board (CB) in the cooling zone (<NUM>, 40A, 40B);
- a lower vent hole (<NUM>) provided below the pair of rails (<NUM>, 11R) in the cooling zone (<NUM>, 40A, 40B);
- an external channel (<NUM>) that connects the upper and lower vent holes (<NUM>, <NUM>) with each other outside the cooling zone (<NUM>, 40A, 40B);
- a blower unit (<NUM>) that is communicated with the upper vent hole (<NUM>), and configured to cause gas in the external channel (<NUM>) to flow through the upper vent hole (<NUM>) hole, the cooling zone (<NUM>, 40A, 40B), and the lower vent hole (<NUM>) in order and return to the external channel (<NUM>); and
- a heat exchanger (<NUM>) provided in a lower opening (<NUM>) linked to the lower vent hole (<NUM>) below the pair of rails (<NUM>, 11R), and configured to cool gas passing through the lower opening (<NUM>);
characterized by:
- a pair of bypass channels (<NUM>, <NUM>) provided in parallel to the pair of rails (<NUM>, 11R) on lateral sides of the pair of rails (<NUM>, 11R), and configured:
- to draw in gas above the pair of rails (<NUM>, 11R) through inlet ports (72a, 73a),
- to let the gas flow through the bypass channels (<NUM>, <NUM>),
- to discharge the gas through discharge ports (72b, 73b) while bypassing locations of the pair of rails (<NUM>, 11R), and
- to thereby deliver the gas to the lower opening (<NUM>); and
- a ventilation plate (<NUM>) provided in a space formed between the pair of bypass channels (<NUM>, <NUM>) below the pair of rails (<NUM>, 11R), and provided with a slit (<NUM>) used to send gas below the pair of rails (<NUM>, 11R) to the lower opening (<NUM>).