JP2008172154A - Reflow furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To blow atmosphere within a carrier section at a reflow furnace onto a substrate in a turbulent flow state to improve the heat exchange efficiency to the substrate, while controlling the atmosphere temperature within the carrier section under a predetermined temperature condition. <P>SOLUTION: In a reflow furnace 10, a hot air generator section 60, where a heater 62 and a fan 64 are arranged, and a carrier section 30 for carriage of a substrate 22 are segmented by a hood 40 and a partition plate 50. Heated atmosphere is fed into the carrier section 30 from many hot air blowout sections attached to the partition plate 50, and atmosphere within the carrier section 30 is sucked from many suction sections 56 attached to the partition plate 50 into the hot air generator section 60 for atmosphere circulation. The hot air blowout sections and the suction sections 56 are provided in pairs, and the hot air blowout section is arranged adjacent to the outside of the suction section 56 in each pair of the hot air blowout section and the suction section 56. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflow furnace, and more particularly to a reflow furnace that can efficiently heat a substrate and can make the atmosphere in a transfer part of the reflow furnace uniform.

  A reflow furnace has been widely used as an apparatus for soldering an electronic component to a substrate by blowing hot air onto the substrate to reflow the solder. As such a reflow furnace, there exists a thing of patent document 1, for example. The reflow furnace described in Patent Document 1 is provided with a heater toward the substrate, and obtains heat to be reflowed by the radiant heat of the heater.

JP-A-1-305554

  In the invention described in Patent Document 1, radiant heat is used as a heating heat source for the substrate and a heating heat source for the atmosphere in the transport unit. When radiant heat is used as a heat source for heating the substrate, there is a problem that reflow processing takes time. Moreover, when the atmosphere in a reflow furnace is heated by radiant heat, there exists a subject that maintenance of temperature is difficult. When the reflow process is performed in such a reflow furnace, there is a problem that a product that does not satisfy the expected quality may be manufactured.

  In recent years, lead-free solder has been used in place of conventional solder. The reflow temperature of lead-free solder is higher than that of conventional solder, and the temperature difference from the heat resistance temperature of electronic components mounted on the board is small. As described above, when an electronic component is attached to a substrate using lead-free solder, there is a problem that the temperature control of the atmosphere in the transport unit must be strictly performed more than ever.

  The present invention provides a reflow furnace capable of improving the heating efficiency of the substrate, making the temperature of the atmosphere in the transfer part of the reflow furnace always uniform, and reliably controlling the atmosphere in the transfer part of the reflow furnace to a predetermined temperature condition. The purpose is to provide.

  In the present invention, a hood and a partition plate divide a hot air generation unit in which a heater and a fan are arranged and a transport unit that transports a substrate, and an atmosphere heated from a large number of hot air ejection units provided in the partition plate is provided. A reflow furnace that feeds into the transport unit and sucks and circulates the atmosphere in the transport unit into the hot air generating unit from a plurality of suction units provided on the partition plate, and the hot air jet unit and the suction unit are paired. A reflow furnace characterized in that, in each pair of the hot air ejection part and the suction part, the hot air ejection part is disposed adjacent to the outside of the suction part.

  Moreover, it is preferable that the said hot-air ejection part is arrange | positioned in multiple places so that the circumference | surroundings of the said suction part may be enclosed. Here, a plurality of hot air ejection portions surrounding the suction portion may be connected to form a hot air ejection portion in a ring shape concentric with the suction portion. As a result, the heat exchange to the substrate becomes efficient and the temperature of the atmosphere in the transport unit is suitably uniform due to the relationship between the hot air jetted from the hot air jet unit and the flow of the atmosphere of the transport unit sucked from the suction unit. It becomes.

  Further, the suction part is formed by a tube, and the hot air jet part is formed in a through hole that penetrates in the plate thickness direction of the partition plate, and the through hole is in contact with a part of the outer peripheral surface of the tube. It is preferable that they are arranged in the above state. On the other hand, the hot air ejection part is formed of a tube, and the suction part is formed in a through hole penetrating in the plate thickness direction of the partition plate, and the tube is in contact with a part of the outer peripheral surface of the through hole. It may be arranged in the state. By adopting these configurations, the substrate can be more suitably heated, and the atmospheric temperature in the transport unit can be made uniform.

  Moreover, it is preferable that ratio of the flow-path cross-sectional area of the said suction part and the flow-path cross-sectional area of the said hot-air ejection part is the range of 2: 1-4: 1. Furthermore, it is more preferable that the ratio of the channel cross-sectional area of the suction part to the channel cross-sectional area of the hot air ejection part is 3: 1. Thereby, the balance between inflow and outflow of the heated atmosphere ejected from the hot air ejection section and the atmosphere sucked from the transport section via the suction section can be improved, and heat can be applied to the substrate more suitably. The atmospheric temperature in the transport unit can be maintained uniformly.

  In addition, a part of the heated atmosphere ejected from the hot air ejection section is sucked into the suction section, thereby forming a turbulent flow in the transport section, thereby improving the heating efficiency of the substrate. The atmospheric temperature in the transfer unit is made as uniform as possible. Thereby, the atmosphere sprayed in the conveyance part spreads in the conveyance part, the heating performance to a board | substrate improves, and the atmospheric temperature in a conveyance part can be made uniform.

According to the reflow furnace of the present invention, the atmosphere to be wiped on the substrate can be in a turbulent state, so that the substrate can be efficiently heated and the reflow process can be performed in a short time. According to such a reflow furnace, even when lead-free solder is used, the thermal load on the electronic component mounted on the board can be minimized.
In addition, since the ambient temperature in the transport unit can be made as uniform as possible, it is possible to eliminate unevenness in solder reflow of a substrate on which electronic components are mounted using solder. That is, a substrate on which electronic components are mounted with uniform quality can be provided, and the yield of electronic component mounted products can be improved.

(First embodiment)
Hereinafter, the reflow furnace in this embodiment is demonstrated in detail based on drawing.
FIG. 1 is an explanatory view of the schematic configuration of the reflow furnace in the present embodiment as viewed from the substrate transport direction. FIG. 2 is an explanatory view of the direction of the partition plate from the transport unit side. FIG. 3 is an enlarged view of a portion Z in FIG. FIG. 4 is an explanatory diagram showing the flow of the atmosphere in the transport section, hot air ejection section, and suction section.

  In the reflow furnace 10 according to the present embodiment, the substrate 22 on which the electronic component 20 is placed is partitioned by a hood 40 made of a heat insulating material formed in a U shape whose cross-sectional shape opens downward. It is divided into a conveyance unit 30 that conveys in the horizontal direction, and a hot air generation unit 60 in which a heater 62 and a fan (blower fan) 64 are arranged. Reference numeral 12 denotes a pedestal. The internal space of the pedestal 12 can be used as a storage for nitrogen gas required when the reflow furnace 10 is used as a nitrogen furnace.

  An endless circulation type substrate transport device 31 such as a mesh conveyor formed of a heat resistant member is disposed in the transport unit 30. The substrate transport device 31 transports the substrate 22 from the inlet side to the outlet side of the reflow furnace 10 (in a direction perpendicular to the paper surface in FIG. 1). In FIG. 1, a substrate transfer portion of the substrate transfer device 31 is illustrated, and the substrate transfer device 31 circulates in a direction orthogonal to the paper surface.

  The space above the partition plate 50 is formed in a hot air generating unit 60 in which a heater 62 and a blower fan 64 are disposed. The heater 62 and the catalyst body 66 are built in a heater box 68 formed in a rectangular parallelepiped. The heater box 68 is attached to the partition plate 50 by an attachment plate 69. A tunnel portion extending in a direction orthogonal to the transport direction is formed above the transport portion 30 by the bottom surface of the heater box 68, the mounting plate 69, and the partition plate 50.

  An opening 68A is formed on the upper surface of the heater box 68, and a blower fan 64 is disposed opposite to the opening 68A. A plurality of circular through holes 68 </ b> B are formed in the bottom plate of the heater box 68 and communicated with the transport unit 30 via a suction unit (suction tube) 56. The through holes 68B are formed in a staggered arrangement on the bottom plate of the heater box 68.

  A hot air circulation path 80 is formed in the hot air generator 60 by the heater box 68, the hood 40, and the partition plate 50. The hot air circulation path 80 distributes the hot air sent by the blower fan 64 toward both sides (in the direction of arrow A in FIG. 1) in the direction orthogonal to the substrate carrying direction, and from both sides to the carrying unit 30. Are directed downward (in the direction of arrow B in FIG. 1), and in parallel to the transport unit 30, opposite to each other from both sides of the reflow furnace 10 toward the central portion of the reflow furnace 10 by the tunnel part. After guiding in the direction (the direction of arrow C in FIG. 1), it is formed so that it can be ejected from the hot air ejection part 54 toward the substrate 22 conveyed onto the conveyance part 30.

  The conveyance unit 30 and the hot air circulation path 80 are communicated with each other by a hot air jet unit 54 formed in the partition plate 50. Further, both ends of the conveying unit 30 and the hot air generating unit 60 (heater 62) are fitted in both holes so as to pass the through hole 52 of the partition plate 50 and the through hole 68B formed in the bottom plate of the heater box 68. The suction section (suction tube) 56 communicates with each other. Therefore, the suction pipe 56 extends in a state of passing through the tunnel portion in the vertical direction, and communicates the transport unit 30 and the heater box 68.

  The through holes 52 formed in the partition plate 50 are formed by pressing or the like so as to form a staggered arrangement having the same arrangement as the through holes 68B formed in the heater box 68. As shown in FIGS. 2 and 3, the shape of the through hole 52 includes an inner hole 53 into which one end of a suction pipe 56 made of a tube used as the suction portion 56 is press-fitted, and a semicircle on the periphery of the inner hole 53. It is formed in a shape having an outer hole (hot air ejection portion) 54 that forms a shape. The inner diameter of the inner hole 53 is equal to the outer diameter of the suction pipe 56.

  The outer hole 54 of the through hole 52 formed in the partition plate 50 maintains the state of penetrating the partition plate 50 in the plate thickness direction even after the suction pipe 56 is attached to the partition plate 50. In the present embodiment, the outer hole 54 serves as a hot air ejection portion 54. That is, each hot-air ejection part 54 is provided in pairs with each suction pipe 56, and is arranged at a plurality of locations in such a manner that it surrounds the suction part of the suction pipe 56 from the outside and is in contact with a part of the outer peripheral surface of the suction pipe 56. It will be in the installed state.

  Further, the ratio of the flow path area of the suction pipe 56 and the flow path area of the hot-air ejection part 54 is preferably in the range of 4: 1 to 2: 1. This is a case where the flow area of the hot-air ejection portion 54 is a ratio of 3: 1. As described above, the flow area of the hot air ejection part 54 is set to be in a range of ¼ to 1/2 with respect to the flow area of the suction pipe 56. The flow rate of the atmosphere ejected into the air is 2 to 4 times the flow rate of the atmosphere sucked into the suction pipe 56.

In the reflow furnace 10, solder may be reflowed while nitrogen gas is introduced from a supply port (not shown) and air is purged as much as possible.
The atmosphere heated from the hot-air ejection unit 54 is ejected into the transport unit 30, and the atmosphere in the transport unit 30 is sucked by the suction pipe 56 and introduced into the heater box 68. In this way, the atmosphere circulates in the reflow furnace 10. Of course, part of the atmosphere introduced into the reflow furnace 10 flows out from the inlet side and the outlet side of the reflow furnace 10.

  Since the hot air jetting part 54 is arranged in a state adjacent to the outside of the suction pipe (suction part) 56, a part of the atmosphere jetted from the hot air jetting part 54 into the transport unit 30 is illustrated by the suction pipe 56. As shown in FIG. 4, turbulent flow is generated in the atmosphere ejected from the hot air ejection section 54 into the transport section 30, and the substrate 22 is uniformly wiped. Further, since the atmosphere is in a turbulent state, the substrate 22 is efficiently heated, so that the reflow process can be performed in a short time. Furthermore, the temperature of the atmosphere in the transport unit 30 is made uniform, and good reflow is performed.

  Further, as described above, since the through holes 52 of the partition plate 50 are arranged in a staggered arrangement in a plan view, the hot air ejection part 54 and the suction pipe in the direction orthogonal to the transport direction of the substrate 22 in the transport part 30 are used. The arrangement density of 56 can be increased. Increasing the arrangement density of the hot-air jets 54 and the suction pipes 56 is advantageous because the atmosphere in the transport unit 30 is stirred more highly, and the ambient temperature in the transport unit 30 can be made more uniform. .

FIG. 5 shows the flow velocity distribution of the atmosphere in the reflow furnace 10. An anemometer was attached to the substrate 22, and the wind velocity of the atmosphere wiped against the substrate 22 was measured by carrying the inside of the reflow furnace 10. The section A in FIG. 5 shows the wind speed in the reflow furnace 10 in the present embodiment, and the section B shows an intermediate position between the suction pipes 56 at positions away from the suction pipes 56 as shown in the lower part of the figure. A comparative example in the case where the hot-air ejection part 54 is arranged (prior art) is shown.
In section A in FIG. 5, the difference between the maximum value Amax and the minimum value Amin of the wind speed is small, whereas in section B, the difference (the difference between the maximum value Bmax and the minimum value Bmin of the wind speed) is extremely large. It has become. In the case of the present embodiment, as described above, a part of the atmosphere ejected from the hot air ejection part 54 is sucked so as to wrap around the atmosphere sucked from the suction pipe 56, and the turbulent flow state is obtained. In contrast, in the case of the comparative example, it is considered that the atmosphere is ejected straight from the hot air ejection portion 54 and the atmosphere is less agitated.

From this experimental result, according to the reflow furnace 10 according to the present embodiment, there is little variation in the flow velocity of the atmosphere that is wiped to the substrate 22 in the transport unit 30, and the substrate 22 is wiped in a uniform atmosphere. I understand. Thus, even when a uniform atmosphere flows in the transport unit 30, the substrate 22 can be efficiently heated, and the occurrence of temperature unevenness in the transport unit 30 can be suitably prevented.
Moreover, it becomes possible to perform the solder reflow process under uniform conditions, and the yield of products after the reflow process can be improved.

Next, the flow of the atmosphere in the reflow furnace 10 will be described.
The atmosphere in the conveyance unit 30 sucked into the heater box 68 by the blower fan 64 is heated by the heater 62, passes through the opening 68 </ b> A of the heater box 68, and is sent out again to the hot air circulation path 80 by the blower fan 64. . The heated atmosphere sent out by the blower fan 64 is guided so as to be separated in the hot air circulation path 80 toward both sides in the direction orthogonal to the extending direction of the transport unit 30 (in the direction of arrow A in FIG. 1). Downward from the both sides toward the transport unit 30 (in the direction of arrow B in FIG. 1), and further in the reverse direction so that the tunnel part between the transport unit 30 and the heater box 68 approaches each other from the side. 1 (in the direction of arrow C in FIG. 1), and then ejected from the hot air ejection section 54 provided on the partition plate 50 toward the substrate 22 transported into the transport section 30 (in the direction of arrow D in FIG. 1). . The atmosphere ejected to the transport unit 30 reflows the solder mounted on the substrate 22. The atmosphere in the transport unit 30 is sucked into the heater box 68 (on the hot air generating unit 60 side) by the blower fan 62 via the suction pipe 56 attached to the through hole 52 of the partition plate 50 (in FIG. 1). Arrow E direction).
The atmosphere sucked into the heater box 68 (the internal space of the hot air generator 60) is heated again by the heater 62, and then passes through the opening 68A on the upper surface of the heater box 68 and sucked into the blower fan 62 (see FIG. F direction in 1). In this way, the atmosphere of the transport unit 30 circulates inside the reflow furnace 10.

(Second Embodiment)
Next, another embodiment will be described. In the first embodiment, the single reflow furnace 10 has been described. In this embodiment, as shown in FIG. 5, hot air generators 60 and 60 are disposed above and below the transport unit 30, and the heater 60 and The reflow furnace 10 provided with the blower fans 62 will be described.

The configuration of the substrate transfer device 31 in this embodiment is not particularly limited, but two endless chains 31A that rotate in a direction perpendicular to the paper surface of FIG. 6 are provided in parallel, and each chain piece is inwardly provided. The thing of the form which provided the support pin P which protrudes toward is employ | adopted. The substrate 22 conveyed by the substrate conveying device 31 can be placed between the support pins P in a bridging manner and conveyed.
In the present embodiment, since the heater 62 and the blower fan 64 are respectively provided above and below the transport unit 30, the atmosphere in the transport unit 30 can be set to a more uniform temperature condition.

  In the embodiment described above, a configuration in which one reflow furnace 10 is disposed in the transport direction of the substrate 22 is shown, but actually, a plurality of reflow furnaces are disposed in the transport direction of the substrate 22. 10 is connected to a continuous reflow furnace. In this case, the hood 40 may be divided into a plurality of pieces in the longitudinal direction and used as a partition plate for each reflow furnace 10. Further, a catalyst body (not shown) for removing the flux contained in the atmosphere can be disposed in the reflow furnace 10 in a necessary section.

  By adopting the continuous reflow furnace, the electronic components 20 are continuously soldered to the substrate 22 by sequentially arranging the substrates 22 on the transport unit 30 and sequentially carrying them into the continuous reflow furnace. Can do. A plurality of reflow furnaces 10, 10, 10,... That have changed the temperature setting of the transport unit 30 are connected in the substrate transport direction so that a temperature gradient is appropriately provided in the transport direction (preheating unit, heating unit, main heating unit). , And a configuration such as a cooling unit). Thereby, fine reflow conditions (reflow temperature and time) can be set.

  In both a single reflow furnace and a continuous reflow furnace, if a labyrinth or an air curtain device is provided at the entrance / exit part of the transfer unit 30 which is a boundary between the reflow furnace 10 and the outside, the temperature of the atmosphere of the transfer unit 30 This is preferable because it can be easily managed.

  The reflow furnace 10 in the embodiment described above circulates the atmosphere in the reflow furnace 10 once in a horizontal direction perpendicular to the extending direction of the transport unit 30, and then merges the divided atmosphere again. Although a so-called nitrogen furnace in which nitrogen is introduced into the reflow furnace 10 is described, the circulation mode of the atmosphere is not particularly limited, and any atmospheric circulation form and so-called atmospheric furnace in which nitrogen is not introduced may be used. Of course, the present invention can be applied.

Further, the hot air ejection part 54 does not necessarily have to be formed at a plurality of locations on the outer peripheral edge of the suction part (suction pipe) 56. Of course, as another form of the hot air ejection portion 54, for example, it may be formed in a ring shape concentric with the suction portion 56. When the hot-air ejection part 54 is formed in a ring shape concentric with the suction part 56, a double-structured tube 58 as shown in FIG. 7 is provided in a through-hole provided in the through-hole 52 of the partition plate 50 and the bottom of the heater box 68. 68B, the space between the outer tube 58A and the inner tube 58B may be used as the hot air blowing portion 54, and the inner space of the inner tube 58B may be used as the suction portion 56.
In this case as well, the ratio of the channel area of the suction portion 56 and the channel area of the hot air ejection portion 54 is preferably the ratio described above.

  In the present embodiment, the hot air ejection part 54 is configured by the outer hole 54 of the through hole 52 formed in the partition plate 50 and the suction part is configured by the suction pipe 56, but the outer periphery of the suction part 56 is surrounded. Thus, even if the configuration in which the hot air ejection portion 54 is arranged as described above, the configuration in which the hot air ejection portion 54 is formed by a tubular body and the suction portion 56 is configured by a through hole formed in the partition plate is adopted. Similar effects can be obtained.

It is explanatory drawing which faced from the board | substrate conveyance direction which shows schematic structure of the reflow furnace in 1st Embodiment. It is explanatory drawing which faced the direction of the partition plate from the conveyance part side. FIG. 3 is an enlarged view of a Z portion in FIG. 2. It is explanatory drawing which shows the flow of the atmosphere in a conveyance part, a hot-air ejection part, and a suction part. It is a graph which shows the result of the experiment which measured the wind speed of the atmosphere wiped off to a board | substrate in a conveyance part by the reflow furnace using the partition plate concerning 1st Embodiment, and the reflow furnace using the partition plate concerning a prior art. . It is explanatory drawing which shows schematic structure of the reflow furnace of 2nd Embodiment. It is explanatory drawing which shows an example of other embodiment of a hot-air ejection part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reflow furnace 12 Base 20 Electronic component 22 Board | substrate 30 Conveyance part 31 Substrate conveyance apparatus 40 Hood 50 Partition plate 52 Through-hole 54 Hot-air ejection part (outer hole)
56 Suction unit (suction tube)
58 Double structure pipe 58A Outer pipe 58B Inner pipe 60 Hot air generating part 62 Heater 64 Blower fan 68 Heater box 69 Mounting plate 80 Hot air circulation path

Claims (8)

The hood and the partition plate divide the hot air generating unit in which the heater and the fan are disposed and the transport unit for transporting the substrate, and the atmosphere heated from the hot air jetting portions provided on the partition plate is contained in the transport unit. A reflow furnace that draws in and circulates the atmosphere in the transport unit into the hot air generation unit from a plurality of suction units provided in the partition plate;
The hot air ejection part and the suction part are provided in pairs, and in each pair of the hot air ejection part and the suction part, the hot air ejection part is disposed adjacent to the outside of the suction part. A reflow furnace characterized by having   The reflow furnace according to claim 1, wherein the hot air ejection part is arranged at a plurality of locations so as to surround the suction part.   The reflow furnace according to claim 1, wherein the hot air ejection part is formed in a ring shape concentric with the suction part. The suction part is formed by a tube, and the hot air ejection part is formed in a through-hole penetrating in the plate thickness direction of the partition plate,
The reflow furnace according to any one of claims 1 to 3, wherein the through-hole is disposed in contact with a part of the outer peripheral surface of the tubular body. The hot air ejection part is formed by a tube, and the suction part is formed in a through-hole penetrating in the plate thickness direction of the partition plate,
The reflow furnace according to any one of claims 1 to 3, wherein the tubular body is disposed in contact with a part of an outer peripheral surface of the through hole.   The ratio of the channel cross-sectional area of the suction part and the channel cross-sectional area of the hot air ejection part is in a range of 2: 1 to 4: 1. The reflow furnace described in 1.   The reflow furnace according to any one of claims 1 to 6, wherein a ratio of a flow passage cross-sectional area of the suction portion and a flow passage cross-sectional area of the hot air ejection portion is 3: 1.   While a part of the heated atmosphere ejected from the hot air ejection part is sucked into the suction part, a turbulent flow is formed in the transport part, thereby improving the heating efficiency to the substrate, and The reflow furnace according to any one of claims 1 to 7, wherein the atmospheric temperature in the transport unit is made as uniform as possible.

Images