JP5395940B2 - Reflow device - Google Patents

Description

  The present invention relates to a reflow apparatus, and in particular, prevents flux from dripping on an object to be heated.

  A reflow apparatus is used in which a solder composition is supplied in advance to an electronic component or a printed wiring board, and the board is conveyed in a reflow furnace by a conveyor. The reflow apparatus includes a transport conveyor for transporting a substrate, and a reflow furnace main body to which a substrate as an object to be heated is supplied by the transport conveyor. For example, the reflow furnace is divided into a plurality of zones along a transfer path from a carry-in port to a carry-out port, and the plurality of zones are arranged in-line. The plurality of zones have roles such as a heating zone and a cooling zone depending on their functions.

  Each of the heating zones has an upper furnace body and a lower furnace body. For example, hot air is blown against the substrate from the upper furnace body of the zone, and hot air is blown against the substrate from the lower furnace body, thereby melting the solder in the solder composition and Is soldered.

  The solder composition includes powder solder, a solvent, and a flux. The flux contains rosin as a component, removes the oxide film on the surface of the metal to be soldered, prevents reoxidation by heating during soldering, reduces the surface tension of the solder and improves wetting It acts as a coating agent. This flux is vaporized by heating and fills the reflow furnace. The vaporized flux tends to adhere to a low temperature part, and when the vaporized flux adheres, it may drop from the adhering part and adhere to the upper surface of the substrate, impairing the performance of the substrate. In addition, there may be a case where the reflow process is greatly affected by depositing on a portion where the temperature decreases in the furnace. Therefore, several methods for removing or collecting the flux in the reflow furnace have been proposed.

  In recent reflow of lead-free solder, the wettability is generally inferior to that of Sn-Pb cream solder, so the reflow temperature also increases. Is made to suppress. That is, the rosin component contained in the solder paste is increased, and a component that is difficult to thermally decompose is used. This results in an increase in the vaporized flux component released into the furnace.

  For example, the following Patent Document 1 describes a reflow device that receives and removes flux liquefied at a plurality of locations with a receiving pan.

Japanese Patent Laid-Open No. 06-164128

  The reflow apparatus described in Patent Document 1 receives a flux adhered on a wall surface or the like by a receiving tray, and does not take into consideration the dripping of the flux adhered to the inner surface of the blower. The problem of flux sag will be described with reference to FIG.

  As shown by the arrow, the air generated by the fan 39 provided in the upper furnace body, for example, the fan 39 of the turbofan hits the inner surface of the case 40 of the blower and enters the upper furnace body through the hole 51 provided in the upper surface of the upper furnace body. It is sent. Further, the wind is dispersed by an air guide plate (also referred to as a current plate) 117, passes through the heater 18 and the panel 19, and is blown to the heated object W as hot air.

  When the atmospheric gas in the furnace body is blown on the inner surface of the case 40 as wind, the flux M11 adheres to the inner surface of the case because the case 40 is in contact with the outside air and has a relatively low temperature. Since the flux is liquid, it is dropped into the furnace body from the lower hole 51, flows on the plate surface of the air guide plate 117, and further drops downward. It drops on the upper surface of the panel 19 through the heater 18, and the flux on the panel 19 drops on the object to be heated (wiring board) W through the small hole. As a result, the article to be heated W is handled as a defective substrate.

  Accordingly, an object of the present invention is to provide a reflow apparatus capable of preventing a flux component in an atmospheric gas from adhering and drooping downward to generate a defective substrate.

In order to solve the above-described problem, the present invention includes a blower installed above the furnace body,
A wind guide plate that receives the wind blown downward from the blower and disperses the wind;
A heater disposed below the air guide plate;
A panel that is arranged below the heater and blows hot air against the object to be heated through a number of small holes;
This is a reflow device provided with a receiving portion for collecting flux dropped on the wind guide plate or flux adhered to the wind guide plate.

  According to the present invention, when the flux is dropped from the blower case onto the lower air guide plate, the flux is dripped onto the lower substrate by receiving the flux by the hook provided on the lower edge of the air guide plate, for example. Is prevented.

It is a basic diagram which shows the outline of the reflow apparatus by one embodiment of this invention. It is a graph which shows the example of the temperature profile at the time of reflow. It is sectional drawing which shows an example of a structure of one zone of the reflow apparatus by one Embodiment of this invention. 1 is a perspective view of an example of a wind guide plate according to an embodiment of the present invention and a schematic diagram schematically showing a gas flow in an upper furnace body. It is a basic diagram used for description of the structure of prevention of the dripping of the flux of the reflow apparatus by this invention. It is a one part perspective view of the panel in one embodiment of this invention. It is a basic diagram used for description of the problem of the conventional reflow apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration excluding an outer plate of a reflow apparatus according to an embodiment of the present invention. In FIG. 1, illustration of the flux collection | recovery apparatus arrange | positioned outside a reflow furnace for convenience of explanation is abbreviate | omitted. The embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

  An object to be heated, on which electronic components for surface mounting are mounted on both sides of the printed wiring board, is placed on a conveyor, and is carried into the furnace body of the reflow apparatus from the carry-in entrance 11. The conveyor conveys the object to be heated in the direction of the arrow (from left to right as viewed in FIG. 1) at a predetermined speed, and the object to be heated is taken out from the carry-out port 12.

  A reflow furnace is sequentially divided into, for example, nine zones Z1 to Z9 along the conveyance path from the carry-in port 11 to the carry-out port 12, and these zones Z1 to Z9 are arranged in-line. Seven zones Z1 to Z7 from the inlet side are heating zones, and two zones Z8 and Z9 on the outlet side are cooling zones. A forced cooling unit 14 is provided in relation to the cooling zones Z8 and Z9.

  The plurality of zones Z1 to Z9 described above controls the temperature of the object to be heated according to the temperature profile during reflow. FIG. 2 shows an outline of an example of a temperature profile. The horizontal axis represents time, and the vertical axis represents the surface temperature of a printed wiring board on which an object to be heated, such as an electronic component, is mounted. The first section is the temperature raising portion R1 where the temperature rises due to heating, the next section is the preheating (preheating) portion R2 where the temperature is substantially constant, the next section is the main heating portion R3, and the last section is This is the cooling unit R4.

  The temperature raising portion R1 is a period in which the substrate is heated from room temperature to a preheating portion R2 (for example, 150 ° C. to 170 ° C.). The preheating portion R2 is a period for performing isothermal heating, activating the flux, removing the oxide film on the surface of the electrodes and solder powder, and eliminating the heating unevenness of the printed wiring board. The main heating portion R3 (for example, 220 ° C. to 240 ° C. at the peak temperature) is a period in which the solder is melted and the joining is completed. In the main heating part R3, the temperature needs to be raised to a temperature exceeding the melting temperature of the solder. Even when the preheating portion R2 has passed, the main heating portion R3 needs to be heated to a temperature exceeding the melting temperature of the solder because there is uneven temperature rise. The last cooling part R4 is a period in which the printed wiring board is rapidly cooled to form a solder composition.

  In FIG. 2, curve 1 shows the temperature profile of lead-free solder. The temperature profile in the case of eutectic solder is shown by curve 2. Since the melting point of lead-free solder is higher than the melting point of eutectic solder, the set temperature in the preheating portion R2 is higher than that of eutectic solder.

  In the reflow apparatus, the zones Z1 and Z2 are mainly responsible for the temperature control of the temperature raising portion R1 in FIG. The zones Z3, Z4 and Z5 are mainly responsible for the temperature control of the preheating part R2. The zones Z6 and Z7 are responsible for temperature control of the main heating unit R3. The zone Z8 and the zone Z9 are responsible for temperature control of the cooling unit R4.

  Each of the heating zones Z1 to Z7 has an upper furnace body 15 and a lower furnace body 35 each including a blower. For example, hot air is blown against an object to be heated conveyed from the upper furnace body 15 and the lower furnace body 35 in the zone Z1.

An example of the heating device will be described with reference to FIG. For example, FIG. 3 shows a cross section when the zone Z6 is cut along a plane orthogonal to the transport direction. Within the facing gap between the upper furnace body 15 and the lower furnace body 35, the article to be heated W on which the surface mounting electronic components are mounted on both surfaces of the printed wiring board is placed on the conveyor 31 and conveyed. The upper furnace body 15 and the lower furnace body 35 are filled with, for example, nitrogen (N ₂ ) gas, which is an atmospheric gas. The upper furnace body 15 and the lower furnace body 35 heat the article to be heated W by blowing hot air (heated atmospheric gas) onto the article to be heated W. In addition, you may irradiate infrared rays with a hot air.

  The upper furnace body 15 includes, for example, a blower 16 configured as a turbofan, and air guide plates 17a and 17b arranged to face each other in order to disperse the air from the blower 16 and to make the temperature distribution in the furnace body uniform. The heater 18 is formed by folding a plurality of heater wires, and a panel (heat storage member) 19 having a large number of small holes through which hot air passes. On the other hand, it is sprayed from the upper side. The panel 19 is made of aluminum, for example.

  The lower furnace body 35 has the same configuration as the upper furnace body 15 described above. That is, for example, a blower 26 having a turbofan structure, air guide plates 27a and 27b arranged to face each other in order to disperse the air from the blower 26 and make the temperature distribution in the furnace uniform, and heater wires It has a heater 28 configured by bending a plurality of times, and a panel (heat storage member) 29 having a large number of small holes through which hot air passes. Hot air that has passed through the small holes in the panel 29 is blown against the article to be heated W from below.

  A flux recovery device 41 is provided for the upper furnace body 15. The flux recovery device 41 is installed on the back side of the upper furnace body 15 in a space surrounded by an outer plate, for example. A flux recovery device 61 is provided for the lower furnace body 35. The flux collection device 61 is installed on the back side of the lower furnace body 35 in a space surrounded by an outer plate, for example. The flux recovery device 41 includes a radiator section 42 that cools the atmospheric gas derived from the upper furnace body 15 and a recovery container 43 that recovers the flux liquefied by cooling. Similarly, the flux recovery device 61 includes a radiator unit 62 that cools the atmospheric gas derived from the lower furnace body 35 and a recovery container 63 that recovers the flux liquefied by cooling.

  As shown in FIG. 4A, the air guide plate, for example, the air guide plate 17b, includes an inclined plate 36a whose conveying direction is the longitudinal direction, a flange 36b provided along the lower edge of the inclined plate 36a, and an inclined plate 36a. And an attachment arm 37 for attaching to a duct or the like in the furnace body. Wind is dispersed by the inclined plate 36a. The air guide plate 17b may use a configuration divided along the transport direction. The flange 36b is preferably detachable from the inclined plate 36a. Although not shown, the other air guide plates 17a, 27a, and 27b have the same configuration.

  FIG. 4B schematically shows the flow of wind in the upper furnace body 15. The blower 16 has a motor 38 and a blade 39 rotated by the motor 38. In the case of a turbofan, when the blades 39 are rotated, air is blown from two places around the periphery, and this wind is sent into the upper furnace body 15 through holes 50 and 51 provided at two places in the upper part of the furnace body. Further, the wind is dispersed by the air guide plates 17 a and 17 b, passes through the heater 18 and the panel 19, and is blown to the heated object W. Further, the blower 16 introduces atmospheric gas in the furnace through a hole near the center.

  A hole 52 serving as an outlet for leading atmospheric gas to the flux recovery device 41 is provided in a path through which hot air circulates by the blower 16. The hole 52 is provided at a location where the pressure is high in the furnace. A hole 53 as an inlet for introducing the gas from the flux recovery device 41 into the upper furnace body 15 is provided at a location where the pressure is low. These holes 52 and 53 actually correspond to openings on one end sides of the connection pipes 54 and 55, respectively. Each of the connecting pipes 54 and 55 and the connecting pipe of the flux recovery apparatus 41 are connected by a hose not shown. Also in the lower furnace body 35, the atmospheric gas is led out to the flux recovery device 61 from a hole provided at a high pressure in the furnace, and the gas having a reduced flux component from the flux recovery device 61 has a low pressure in the furnace. It is introduced from the hole provided in the place.

  In addition, the flux collection | recovery apparatuses 41 and 61 are provided in the zone where dirt of atmospheric gas is large in each zone of a reflow apparatus. However, you may arrange | position the flux collection | recovery apparatuses 41 and 61 in all the zones of a reflow apparatus.

  Even when the flux recovery devices 41 and 61 are installed, the flux component cannot be completely removed, the flux adheres to the inner surface of the case in contact with the outside air of the blower 16, and the problem of dripping (dripping) on the lower substrate is eliminated. I can't. The present invention effectively prevents the flux from dripping on the substrate.

  As shown in FIG. 5A, the flux M1 adheres to the inner surface of the case 40 of the blower 16. The case 40 is in close contact with the upper surface of the upper furnace body, and wind is blown into the lower furnace body 15 through the holes 50 and 51. Since the flux M1 often adheres to the inner surface of the side wall where the wind blows inside the case 40 of the blower, a circular hole (or long hole) 65 for drain is formed on the upper surface of the upper furnace body 15 near the side wall. A formed pipe 66 is provided with a hole 65 and an open end. Although not shown in the drawing, the pipe 66 is extended to the outside of the upper furnace body 15 so that the flux that flows out through the pipe 66 outside is received by the recovery container. An opening / closing valve is provided at the other end of the piping 66 outside the furnace body, and the valve is opened only when the flux is recovered. The pipe 66 is made of a material having excellent heat resistance and corrosion resistance, such as stainless steel. Note that the flux may be collected inside the furnace body.

  The flux that hangs downward from the blower or the flux that adheres to the inclined plate 36a of the air guide plate 17b flows downward along the plate surface of the inclined plate 36a of the air guide plate 17b, flows into the kite 36b, and enters the kite 36b. Can be stored. The upper part of the outer plate (case) covering the upper half including the upper furnace body 15 of the reflow device is configured to be openable and closable around a side parallel to the transport direction for maintenance. The entire portion above the transport surface opens upward, and the entire upper portion is inclined. The flux M2 stored in the flange 36b flows into the recovery container when the upper part of the outer plate is opened and the upper part is inclined, and the flux is recovered. As an alternative configuration, a configuration in which the basket 36b is inclined in the longitudinal direction and a collection container is provided at the lower end of the basket 36b may be used.

  As shown in FIG. 5B, it is possible to provide a flange 36c separate from the wind guide plate, and the flange 36c can be detachably attached to the wind guide plate. For example, the structure which provides the engaging part which fits the spring-shaped locking piece and the hole in which a locking piece enters can be used in multiple places.

  When the air guide plate does not have the flange 36b (or flange 36c), or when the flux overflows from the flange, the flux passes through the heater 18 and drops onto the panel 19, and a small hole provided in the panel 19 The flux hangs on and adheres to the substrate W. In one embodiment of the present invention, as shown in FIGS. 5C and 6, a panel 191 having a recess 72 for collecting flux on a surface on which many small holes 71 are formed and a side wall 74 planted along the outer periphery. Is used. In order to prevent the flux from flowing out of the small hole 71, a boss 73 is provided around the small hole 71. For example, such a panel 191 can be manufactured by machining one metal plate.

  The panel 191 having such a configuration can store the flux M3 in the recess 72. Drain holes 75 a and 75 b are formed in a part of the panel 191. Although not shown, normally, the holes 75a and 75b are closed with stoppers. By opening the upper outer plate of the reflow device, the stopper is opened and the flux accumulated from the holes 75a and 75b is supplied to the recovery container 77 in a state where the entire upper part is inclined. Note that a pipe for guiding the flux accumulated in the recess 72 of the panel 191 to the collection container may be provided so that the flux is collected inside the furnace body without taking the panel 191 out of the furnace body.

  The configuration for accumulating the flux is not limited to that shown in FIGS. 5C and 6, and the configuration shown in FIG. 5D can be used. The panel 192 shown in FIG. 5D has an end surface of a boss 73 ′ provided around the small hole 71 as an inclined surface that descends toward the recess 76, and a shape from which flux from above easily enters the recess 76. In addition, a pin is planted and the inner surface of the recess 76 is formed on the small hole 71 side. Such a recess 76 can prevent the flux accumulated in the recess 76 from being scattered by the wind.

  As described above, in one embodiment of the present invention, three types of flux sag prevention mechanisms are included. That is, the first mechanism is a drain and a pipe for discharging the flux adhered to the inner surface of the blower. A 2nd mechanism provides the cage | basket for accumulating a flux in the baffle plate for disperse | distributing the wind which the air blower blew off. The third mechanism forms a concave portion for collecting flux on the panel, and collects the flux collected in the concave portion through the drain. By combining two or more of these three types of mechanisms, flux dripping can be effectively prevented.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications can be made without departing from the gist of the present invention. For example, an inclined groove for collecting the flux may be formed together with the recess in the panel, and the flux may be guided to the collection container or the pipe through the groove. Further, in the case of the lower furnace body, the flux may be collected by forming a drain in the vicinity of the upper surface of the case of the blower where the flux tends to accumulate.

DESCRIPTION OF SYMBOLS 11 ... Carrying in port 12 ... Carrying out port 14 ... Forced cooling unit 15 ... Upper furnace body 16, 26 ... Blower 17a, 17b, 27a, 27b ... Air guide plate 18, 28. ..Heater 19, 29... Panel 31... Conveyor 35 .. Lower furnace body 36 a .. Inclined plate 36 b, 36 c. Flux recovery device 66 ... Pipe for flux recovery 72 ... Panel recess 73 ... Boss 74 ... Side wall

Claims (7)

A blower installed above the furnace body;
A wind guide plate that receives wind blown downward from the blower and disperses the wind;
A heater disposed below the air guide plate;
A panel that is arranged below the heater and blows hot air against the object to be heated through a number of small holes;
The reflow apparatus provided with the receiving part which accumulates the flux dripped with respect to the said baffle plate, or the flux which adhered on the said baffle plate.   The reflow apparatus according to claim 1, wherein the receiving portion is a ridge extending along a lower edge of the inclined air guide plate.   The reflow apparatus according to any one of claims 1 and 2, wherein the receiving portion is detachable from the air guide plate.   The concave part which accumulates the flux dripped from the said baffle plate on the surface facing the said heater of the said panel, and the collection | recovery means which collect | recovers the flux collected in this recessed part were provided in any one of Claim 1, 2, and 3 Reflow equipment.   The reflow device according to claim 4, wherein a wall portion provided along the periphery of the panel and a boss provided around the small hole are formed in the recess. The blower is separated from the outside air by a case, and a blade is housed in the case.
The reflow apparatus according to any one of claims 1 to 5, wherein the flux adhered to the inner surface of the case side wall blown by the wind of the blower is collected.   The reflow device according to claim 6, wherein the flux adhered to the inner surface of the case of the blower is led out of the furnace body, and the flux is recovered outside the furnace body.

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