JPWO2007023604A1 - Reflow furnace - Google Patents

Abstract

[PROBLEMS] A conventional reflow furnace in which a large number of blowout ports and suction ports are formed in the vicinity of the blowout ports has a problem that a high-height component is thermally damaged or a printed circuit board is heated unevenly. It was. In the reflow furnace according to the present invention, a zigzag plate-like nozzle having a large number of ejection holes formed in the upper portion protrudes from the heater surface, and a plurality of blocks forming the plate-like nozzle can be moved up and down. It has become. [Selection] Figure 4

Description

  The present invention relates to a reflow furnace that performs soldering by melting a solder paste applied to a printed circuit board.

  When soldering a printed circuit board and an electronic component using solder paste, it is generally performed in a reflow furnace. A reflow furnace has a preheating zone, a main heating zone, and a cooling zone inside the tunnel-shaped muffle. A heater is installed in the preheating zone and the main heating zone, and a cooler is installed in the cooling zone. Yes.

  As a heater used for the reflow furnace, there are an infrared heater and a hot air blowing heater. Infrared heaters penetrate infrared rays into the printed circuit board and electronic equipment and melt the solder paste applied to the soldering part, but since the infrared rays go straight, the soldering part is a shadow of electronic parts. There was a problem that the soldering part which becomes a gap and could not be heated sufficiently.

  On the other hand, since the hot air convects in the muffle, the hot air blowing heater penetrates into the shadows of electronic components and narrow gaps, so the entire printed circuit board can be heated uniformly compared to the infrared heater. It has the feature that it can be used, and it is often used in reflow furnaces today.

  A hot air blowing heater installed in a conventional reflow furnace has a large area hot air blowing port and a small area hot air suction port formed adjacent to the hot air blowing port. Was blown in large quantities and applied to the printed circuit board to heat a large area of the printed circuit board at one time. It was thought that blowing hot air from this large area outlet could uniformly heat the printed circuit board, but recent experimental results revealed that even if hot air was blown from a large area, it could not be heated uniformly. did. In other words, after heating the printed circuit board by blowing hot air from a large area hot air outlet, the heated printed circuit board advances and arrives at the intake port. The printed circuit board will be cooled. Therefore, when a temperature profile is drawn in a reflow furnace in which a hot air outlet with a large area and a hot air inlet with a small area are installed adjacent to each other, the temperature at the hot air outlet is increased. Then, the temperature might drop. In this way, if there is a temperature fluctuation in the preheating zone or the main heating zone, the printed circuit board will not be heated uniformly, resulting in partial overheating or underheating, resulting in thermal damage to electronic components or unmelted solder paste. It may become.

In view of the problem of the reflow furnace that blows out hot air from these large area outlets, a large number of small area hot air outlets and continuous hot air outlets are provided. A reflow furnace provided with a continuous hot air inlet is proposed (Patent Documents 1 to 7).
Japanese Patent Laid-Open No. 2-330374 JP 2001-144426 A JP 2001-144427 A JP 2001-326455 A JP 2002-198642 A JP 2002-331357 A JP 2003-332725 A

  By the way, a high electronic component (hereinafter referred to as a vertical component) may be mounted on the printed circuit board. When soldering a printed circuit board mounted with vertical components like this in a conventional reflow oven with a suction port near the hot air outlet, the vertical component near the hot air outlet heats up faster, The temperature rise of other electronic components away from the hot air outlet is delayed. As a result, there is a problem that the entire printed circuit board is not uniformly heated. In addition, if you try to raise the temperature of the part where the temperature rises slowly to the predetermined soldering temperature, the temperature of the part where the temperature rises fast like the vertical component will rise too much, causing the electronic parts to be thermally damaged. Become. Further, in the conventional reflow furnace provided with a suction port in the vicinity of the hot air blowing port, there is a problem that the outside air enters and raises the oxygen concentration when an inert gas is used due to turbulent flow in the muffle. An object of the present invention is to provide a reflow furnace that not only can uniformly heat a printed circuit board on which vertical components are mounted, but also stabilizes the oxygen concentration even in an inert atmosphere.

  In the reflow furnace in which the hot air blowing heater is installed, the present inventor heats the entire printed circuit board evenly by installing a large number of plate nozzles for blowing hot air and hot air suction ports in a zigzag manner. The present invention has been completed by finding that non-uniform heating does not occur when the hot air blowing port is set at a distance corresponding to the vertical height parts.

  The present invention provides a reflow furnace comprising a preheating zone, a main heating zone, and a cooling zone, and zigzag plate-like nozzles protruding from the heater surface are formed on the upper or upper portions of the preheating zone and the main heating zone. A plurality of strips are arranged in a direction transverse to the traveling direction, and each plate-like nozzle is composed of a plurality of blocks, and each block is movable in the vertical direction. The reflow furnace is characterized in that a suction port is formed in the vicinity.

  In the present invention, the plate-like nozzles are arranged at the upper part or the upper and lower parts of the preheating zone and the main heating zone, but the arrangement may be only at the upper part. That is, in general, a printed circuit board is often coated with a solder paste on the top and electronic components are mounted on the application part. Therefore, if only the top of the printed circuit board is heated with hot air, the solder paste can be melted. However, in order to uniformly heat the entire printed circuit board, it is necessary to heat the lower part of the printed circuit board. In this case, not the hot air blown out from the zigzag plate-like nozzle used in the present invention, but the conventional one. The hot air blown out from the nozzle used in the reflow furnace may be used, or far infrared rays may be used. The hot air blowing heater used in the present invention is basically installed at the upper part of the reflow furnace in order to move the block forming the plate-like nozzle up and down according to the height of the electronic component or the like.

  The nozzle plate of the hot air blowing heater used in the present invention has a zigzag shape. This zigzag nozzle plate has the effect of uniformly heating the printed circuit board. In other words, in a reflow furnace in which a plurality of nozzle plates are arranged, if the nozzle plates are arranged in a straight line and in parallel, a dead zone in which hot air does not blow is formed between the nozzle plate and the nozzle plate adjacent to the nozzle plate. When the substrate passes through this dead zone, the printed circuit board has a portion that is not heated linearly. Therefore, in the reflow furnace in which the linear nozzle plate is arranged, the printed circuit board is heated and unheated in a striped pattern laterally in the traveling direction, and the entire printed circuit board is hardly heated uniformly. However, when the plurality of nozzle plates are zigzag-shaped, even if a dead zone is formed between the nozzle plate and the nozzle plate disposed adjacent to the nozzle plate, there is always a heated portion in the lateral direction. Therefore, in this reflow furnace, even if there are a heating part and a non-heating part on the side, both sides of the non-heating part are heating parts, so the heat of the heating part heats the non-heating part and prints. The entire substrate is heated uniformly.

  Further, in the present invention, since the plate-like nozzle of the hot air blowing heater protrudes from the heater surface, a heating region in which a portion surrounded by a pair of adjacent plate-like nozzles and between the heater surface and the printed board becomes a constant temperature. It becomes. In other words, in the heating area, when hot air blown from the ejected hole of the protruding plate nozzle hits the printed circuit board and returns to the suction port formed on the heater surface, the heat is accumulated in the heating area and becomes a constant temperature. . The heating area is formed long in the lateral direction of the printed circuit board, and the heating area sequentially exists with the progress of the printed circuit board. Accordingly, the printed circuit board conveyed by the conveying device is further heated evenly together with the zigzag nozzle plate.

  In the reflow furnace of the present invention, a zigzag plate-like nozzle is formed by combining a plurality of blocks, and each block can move up and down. That is, by moving the block up and down, the distance from the ejection hole of the block to the vertically high part of the printed circuit board can be adjusted. Therefore, by pushing the block of the part through which the vertical height part passes into the back and separating the vertical height part from the ejection hole of the block, the vertical height part will not be overheated and the heating state of the vertical height part and other parts will be It becomes uniform.

  In the reflow furnace of the present invention, the blocks moved up and down must be stopped at appropriate places, so that a locking plate is erected between the blocks. And a locking device is installed in a block or a locking plate. The locking device may be of any structure as long as the block can be securely stopped at a predetermined position, but a spring-biased ball or cone that is simple in structure and can be reliably locked is suitable. Yes. When a spring-biased ball or cone locking device is installed on the block, a plurality of recesses into which the ball or cone can be easily fitted are formed on the locking plate. In this way, the spring-biased ball or cone locking device ensures that the block stays in place only by moving the block in the vertical direction and locking the ball or cone in a suitable recess.

  In the hot air blowing heater used in the reflow furnace of the present invention, the suction port is formed on the heater surface between the plate nozzles, the suction port is formed in a zigzag shape along the plate nozzle, or the adjacent plate shape It may be formed in a zigzag shape at substantially the center between the nozzles. The suction port formed on the heater surface is preferably zigzag with the same pitch as the plate nozzle, but other shapes such as a punching plate in which a large number of holes are formed on the heater surface and a slat in which a large number of slits are formed may be used. . Since a commercially available punching plate and slatter can be used, it is possible to save the trouble of forming a suction port when manufacturing a hot air blowing heater.

  The plate-like nozzle of the hot air blowing heater used in the reflow furnace of the present invention has a blowing port, and the printed board is heated by blowing hot air from the blowing port and hitting the printed board. . The outlet is a hole, a slit, or the like, but a hole is preferable to a slit. This is because the hole can make the hot air faster than the slit, so that rapid heating is possible and productivity can be increased.

  Since the opening area of the hole as the blowout opening is small, the blowout speed of the hot air is much faster than that of the slit, and rapid heating can be performed as much, and the productivity is excellent. However, the hole can be heated sufficiently just below the hole, but when the hole is removed from just below the hole, the temperature becomes lower than that below the hole, resulting in nonuniform heating. Therefore, it has been considered difficult to uniformly heat a hot air blowing heater using holes. Therefore, a large number of ejection holes are formed in the plate-like nozzle, and the ejection holes are not at the same position with respect to the traveling direction of the printed circuit board as the ejection holes of the adjacent plate-like nozzles. It is drilled at the same position as the ejection holes of the plate-like nozzles separated by at least one sheet. In this way, if the ejection hole is formed so as to be shifted from the adjacent plate nozzle, even if the first plate nozzle has a low temperature portion shifted from just below the ejection hole, the next plate nozzle The jet holes are heated by applying hot air to the low temperature portion.

  According to the present invention, a plurality of zigzag plate-like nozzles are formed in a direction transverse to the traveling direction of the printed circuit board, so that hot air is always applied to any part of the printed circuit board running in the reflow furnace. The printed circuit board is uniformly heated. In the reflow furnace according to the present invention, the zigzag plate-like nozzle is formed of a plurality of blocks, and the blocks can be moved up and down, so that the position of the block where the vertically high parts pass is adjusted. By doing this, the distance from the jet outlet to the vertical height component can be adjusted, and the vertical height component is not overheated. Furthermore, in the reflow furnace of the present invention, since the plate-like nozzle protrudes from the heater surface, a horizontally long heating region in which the temperature is constant between adjacent plate-like nozzles is formed, and the printed circuit board progresses. On the other hand, the heating region performs uniform heating. And in the reflow furnace of this invention, since a heating area | region performs self-convection, external air does not penetrate | invade and it can maintain a low oxygen concentration in the stable state.

  Hereinafter, the reflow furnace of the present invention will be described with reference to the drawings. 1 is a front cross-sectional view of the reflow furnace of the present invention, FIG. 2 is a front cross-sectional view of a hot air blowing heater installed in the reflow furnace of the present invention (however, only the nozzle plate is a cross section along the center of the zigzag), and FIG. FIG. 4 is a partial perspective view of the hot air blowing heater installed in the reflow furnace of the present invention (however, it faces upward for easy understanding), FIG. 5 is a plan view of FIG. 4, and FIG. 6 is a portion of FIG. It is an enlarged view.

  As shown in FIG. 1, in the reflow furnace 1 of the present invention, a tunnel-like muffle 2 is formed in the longitudinal direction, and the muffle is a preheating zone 3, a main heating zone 4, and a cooling zone 5. A plurality (three pairs) of hot air blowing heaters 6... Are installed above and below the preheating zone 3, and a plurality (two pairs) of hot air blowing heaters 7 are arranged above and below the main heating zone 4. Is installed. The hot air blowing heater 6 installed in the preheating zone 3 and the hot air blowing heater 7 installed in the main heating zone 4 have almost the same structure, but the hot air blowing heater 7 installed in the main heating zone is hot air installed in the preheating zone. The width in the conveying direction is shorter than that of the blowing heater 6. The cooling zone 5 is provided with a pair of coolers 8 and 8 that do not clearly indicate a structure for cooling the printed circuit board after soldering. In the muffle 2, a conveyor 9 that transports the printed circuit board P runs from the preheating zone 3 to the cooling zone 5 (arrow X).

  Here, the hot air blowing heater installed in the reflow furnace of the present invention will be described. Since the hot air blowing heater installed in the preheating zone and the hot air blowing heater installed in the main heating zone have the same structure, the hot air blowing heater installed in the preheating zone will be described here.

  The hot air blowing heater 6 has a box shape and is divided into four chambers in the vertical direction. As shown in FIGS. 2 and 3, the four chambers are a blower chamber 10, a heating chamber 11, a hot air chamber 12, and a suction chamber 13 from the top.

  A blower 14 is placed in the center of the blow chamber 10. This blower is a sirocco fan and works in conjunction with a motor 15 placed outside. There are partition walls 16 (one not shown) on both sides of the air blowing chamber 10, and one end of the partition wall is an opening 17. The opening of each partition wall is not an opposite position but a separated end.

  In the heating chamber 11, flow paths 18 and 18 are formed on both sides, and a plurality of electric heaters 19 are arranged inside the heating chamber. A suction hole 21 is formed in the partition plate 20 that separates the heating chamber 11 and the blower chamber 10. The suction hole is located directly above the blower 14, and its diameter is slightly smaller than the diameter of the sirocco fan that is the blower.

  The hot air chamber 12 communicates with the opening 17 of the air blowing chamber 10, and hot air is sent from the air blowing chamber 10. A partition plate 22 is stretched between the hot air chamber 12 and the suction chamber 13, and the suction chamber 13 communicates with the heating chamber 11 through a flow path 18. A heater surface 23 is provided above the suction chamber 13. .

  A plurality of zigzag plate-like nozzles 24... Protrude from the heater surface 23 on the partition plate 22. In this standing state, a block forming a plate-like nozzle, which will be described later, is fitted so as to be movable up and down, and the block and the partition plate are sealed. The plurality of zigzag plate-like nozzles 24 are arranged in a direction crossing the traveling direction (arrow X) of the printed circuit board as shown in FIGS. The plate-like nozzle 24 has a large number of ejection holes 25 penetrating therethrough. Further, suction ports 26 are formed on both sides of the plate nozzle 24 along the plate nozzle.

  The zigzag plate-like nozzle 24 is composed of a plurality of blocks 27. The block may be any part of the side that forms the zigzag shape. As the block shape, for example, a V-shaped portion, a W-shaped portion, or a combination of a plurality of V-shaped portions in a zigzag shape may be used to increase the block length. In the embodiment of the present invention, the block is a V-shaped portion. The block 27 is fitted to the partition plate 22 so as to be movable up and down.

  Locking plates 28 are erected on both sides of the block 27, and the locking plates are fixed to the partition plate 22. Therefore, the block 27 can be moved in the vertical direction as indicated by the arrow Y in FIG. Further, locking devices 29 are embedded on both sides of the block 27 as shown in FIG. In the locking device 29, the ball 30 is pressed outward by the compression spring 31, and a part of the ball 30 protrudes from the locking device 29. A plurality of depressions 32 having substantially the same shape as a part of the ball 30 of the locking device 29 are vertically formed on both sides of the locking plate 28.

  Next, the soldering of the printed circuit board in the reflow furnace having the above structure will be described. First, before soldering the printed circuit board on which the vertical component H is mounted, the preheating hot air blowing heater 6 and the main heating hot air blowing heater 7 installed on the upper part of the muffle 2 of the reflow furnace 1 are adjusted. I do. In this adjustment, the block 27 of the plate-like nozzle 24 on the upper side through which the vertical height component H of the printed circuit board P passes is moved upward as shown in FIGS. This movement is to move the block 27 so that the distance between the upper part of the vertical component H and the ejection hole 25 of the block 27 is substantially the same as the distance between the other electronic components D of the printed circuit board P.

  Thereafter, the electric heater 19 disposed in the heating chamber 11 is energized and the motor 15 is driven to rotate the sirocco fan as the blower 14. Then, the gas in the heating chamber 11 is heated by the electric heater 19 and becomes hot hot air, and is drawn into the blower chamber 10 from the suction side of the blower by the blower 14. The hot air drawn into the blower chamber 10 is sent by the blower 14 from the blowout side of the blower to the hot air chamber 12 through the opening 17 and further blown out from the ejection holes 25 of the plurality of plate-like nozzles 24. . In the muffle 2, the printed circuit board P is run by the conveyor 9, and hot air blown from the ejection holes 25 ... of the plate-like nozzle 24 hits the running printed board P to heat the printed board here. To do. In the printed circuit board heated by hot air, the solder paste applied to the soldering portion is melted, and the printed circuit board and the electronic component are soldered. At this time, since the zigzag plate-like nozzles 24... Protrude from the heater surface 23, there is no portion where hot air does not hit the printed circuit board, and all portions are uniformly heated with hot air. Accordingly, there is no partial overheating or unmelting of the solder paste.

  The hot air blown out from the plate-like nozzles takes heat away from the printed circuit board, so the temperature drops. The hot air whose temperature has thus decreased is sucked into the suction port 26 in the vicinity where the plate-like nozzle 24 is erected as shown in FIG. 3 and enters the heating chamber 11 through the flow path 18. The hot air that has entered the heating chamber 11 is heated to a predetermined temperature by the electric heater 19, and is sucked into the blower chamber 10 by the blower 14. And hot air is sent to the hot air chamber 12 from the opening 17, and is blown out again from the ejection hole 25 ... of the plate-like nozzle 24, and heats a printed circuit board. That is, the reflow furnace of the present invention does not interfere with the hot air blown out from other plate-like nozzles because the hot air blown out from the plate-like nozzles is sucked from the suction port immediately after heating the printed circuit board. Therefore, in the reflow furnace of the present invention, there is no turbulent flow in the muffle, and the oxygen concentration is stabilized.

Front sectional view of the reflow furnace of the present invention Front sectional view of hot air blowing heater installed in the reflow furnace of the present invention Side sectional view of hot air blowing heater installed in the reflow furnace of the present invention Partial perspective view of hot air blowing heater installed in the reflow furnace of the present invention Plan view of FIG. Partial enlarged view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflow furnace 3 Preheating zone 4 Main heating zone 5 Cooling zone 6 Hot air blowing heater 23 Heater surface 24 Plate nozzle 25 Ejection hole 26 Suction port 27 Block 29 Locking device 30 Ball 31 Compression spring 32 Dimple

The reflow furnace of the present invention has an excellent effect in an inert atmosphere reflow furnace in which the inside of the muffle is filled with an inert gas because there is no turbulent flow of hot air, but the entire printed circuit board can be heated uniformly. Needless to say, it can also be used in an atmospheric reflow furnace.

Claims (3)

  In a reflow furnace consisting of a preheating zone, a main heating zone, and a cooling zone, zigzag plate-like nozzles protruding from the heater surface are located above or below the preheating zone and the main heating zone in the direction of travel of the printed circuit board. A plurality of strips are arranged in the direction crossing each other, and each plate-like nozzle is composed of a plurality of blocks, and each block is movable in the vertical direction, and suction is performed in the vicinity of the plate-like nozzle. A reflow furnace characterized in that a mouth is formed. The reflow furnace according to claim 1, wherein the block includes a plurality of sides forming a zigzag shape. 2. The reflow furnace according to claim 1, wherein a locking plate for stopping the block at an appropriate position is provided between the blocks.

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