JP4902486B2 - Reflow device - Google Patents

Description

  The present invention relates to a reflow apparatus.

  A solder composition is supplied in advance to an electronic component or printed wiring board, and the substrate is transferred to a reflow furnace by a transfer conveyor and soldered, or the electronic component is placed on the substrate by a thermosetting adhesive. A reflow device is used to secure the device.

  The reflow apparatus includes a transport conveyor for transporting a substrate and a reflow furnace main body to which the substrate 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, for example, an upper heating device and a lower heating device each including a blower. For example, hot air is blown from the upper heating device of the zone to the substrate to be conveyed, and hot air is blown to the substrate to be conveyed from the lower heating device, thereby melting the solder in the solder composition. It is made to adhere to the electrode of a board | substrate.

  The solder composition contains powder solder, a solvent, and a flux. Flux contains rosin as a component, removes the oxide film on the metal surface to be soldered, prevents reoxidation by heating during soldering, reduces the surface tension of the solder and wets it. It acts as a coating agent that improves

  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 is 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 recovering the flux component contained in the atmospheric gas in the reflow furnace have been proposed.

  For example, in the reflow apparatus proposed in Patent Document 1, the atmospheric gas taken out from the reflow furnace is taken out of the furnace, and the taken atmospheric gas is heated to a high temperature at which the catalyst acts, and then passes through the oxidation catalyst. Thus, there has been proposed a method in which the flux component contained in the atmospheric gas is oxidized and decomposed into water (steam) and carbon dioxide gas.

JP 2006-160591 A

  However, in Patent Document 1, if the low-temperature atmosphere gas at the beginning of the reflow furnace operation is heated to a high temperature at which the catalyst acts by the heating means for adjusting the catalyst temperature, a large burden is generated on the heating means for adjusting the catalyst temperature. There was a problem.

  Accordingly, an object of the present invention is to provide a reflow apparatus capable of efficiently raising the atmospheric gas taken out from the reflow furnace to a high temperature at which the catalyst acts.

In order to solve the above-mentioned problems,
This invention
In the reflow apparatus in which the atmospheric gas taken out from the inside of the reflow furnace in one or more zones passes through the flux recovery unit and is returned again into the reflow furnace.
The flux recovery unit includes a gas decomposition part having a catalyst tube for decomposing a flux component in the atmospheric gas, and a heating unit for heating the atmospheric gas before the atmospheric gas passes through the catalyst tube,
The reflow apparatus is characterized in that the heating means starts heating after a predetermined time has elapsed since the main switch of the reflow furnace was turned on.

  In the present invention, the heating of the heating means is started after a predetermined time has elapsed since the main switch of the reflow furnace is turned on, so that the atmospheric gas can be efficiently raised to a high temperature at which the catalyst acts.

  According to the present invention, the atmospheric gas taken out from the reflow furnace can be efficiently raised to a high temperature at which the catalyst acts.

  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, for convenience of explanation, illustration of the flux recovery unit disposed outside the reflow furnace is omitted.

  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 transfer conveyor and is carried into 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. Zone 8 and zone 9 are responsible for temperature control of cooling section R4.

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

An example of the heating device will be described with reference to FIG. For example, the configuration of the zone Z6 is shown in FIG. In the facing gap between the upper heating device 15 and the lower heating device 35, the article to be heated W on which the electronic components for surface mounting are mounted on both sides of the printed wiring board is placed on the conveyor 31 and conveyed. The upper heating device 15 and the lower heating device 35 are filled with, for example, nitrogen (N ₂ ) gas that is an atmospheric gas. The upper heating device 15 and the lower heating device 35 heat the article to be heated W by jetting hot air (heated atmospheric gas) to the article to be heated W. In addition, you may irradiate infrared rays with a hot air.

  The lower heating device 35 includes a main heating source 16, a sub-heating source 17, a blower such as an axial blower 18, a heat storage member 19, a hot air circulation duct 20, an opening 21, and the like. Note that the upper heating device 15 has, for example, substantially the same configuration as the lower heating device 35 described above, and a description of corresponding portions is omitted.

  Hot air is blown against the object to be heated W through the opening 21. The main heating source 16 and the sub heating source 17 are constituted by, for example, an electric heater. The heat storage member 19 is made of, for example, aluminum, and has a large number of holes. Hot air passes through the holes and is blown to the article to be heated W.

  Hot air is circulated by the axial blower 18. That is, via the path of (main heating source 16 → heat storage member 19 → opening 21 → object to be heated W → hot air circulation duct 20 → sub-heating source 17 → hot air circulation duct 20 → axial blower 18 → main heating source 16). Hot air circulates.

  In the vicinity of the axial flow blower 18, pipes 32a and 32b for guiding the atmospheric gas in the reflow furnace to the flux recovery unit are provided. The atmospheric gas is led out from these pipe ports, introduced into the flux recovery unit via the pipe 32a and the pipe 32b, passed through the flux recovery unit, and again introduced into the reflow furnace. In the flux recovery unit, the atmospheric gas is cooled and the flux component contained in the atmospheric gas is condensed and recovered.

  FIG. 4 is a bottom view of the reflow apparatus. As shown in FIG. 4, the flux recovery unit 41 is disposed on the side of the zone Z6 and the zone Z7, for example. The flux recovery unit has a gas decomposition part 38 and a radiator part 39, and the atmospheric gas derived from the reflow furnace is flux recovered via the pipes 32a to 32d and the pipe 40 communicating with the zones Z6 and Z7. Introduced into the unit 41.

  FIG. 5 is a front view of the flux collection unit 41. The flux recovery unit 41 includes a gas decomposition unit 38 and a radiator unit 39 isolated from the gas decomposition unit 38 via a heat insulating material 56. The atmospheric gas derived from the reflow furnace first passes through the gas decomposition section 38, then passes through the pipe 50 and the radiator section 39, and is again introduced into the reflow furnace through the pipe 61.

  The gas decomposition unit 38 includes a catalyst tube 42 and a heating unit 43 that heats the atmospheric gas that passes therethrough. The heating unit 43 is, for example, a heater or the like, and by turning on the heater, the atmosphere gas taken out from the reflow furnace is heated to a temperature at which the effect of the catalyst sufficiently acts, for example, a high temperature of about 300 ° C. to 400 ° C. .

  It is preferable to turn on the heating unit 43 with a predetermined time delay from the timing of turning on the main switch for controlling the reflow furnace. The main switch of the reflow furnace is turned on, and heating in the furnace is started. When a predetermined time elapses and the atmospheric gas is heated to a predetermined temperature (for example, about 200 ° C.), the heating unit 43 is turned on. This is because the burden of heating the atmosphere gas by the heating unit 43 can be reduced.

  Moreover, it is preferable to turn off the heating unit 43 with a predetermined time delay from the timing of turning off the main switch of the reflow furnace. The axial flow fan 18 in the reflow furnace is set to rotate for a predetermined time even when the main switch of the reflow furnace is turned off, and the atmospheric gas in the furnace flows and flows into the gas decomposition unit 38 during this time. To do. Therefore, even if the main switch of the reflow furnace is turned off, in order to decompose the flux component in the atmospheric gas flowing into the gas decomposition unit 38, it is necessary to heat the atmospheric gas to a high temperature at which the catalyst acts in the heating unit 43. Because there is.

The catalyst tube 42 is made of a catalyst such as platinum, lanthanum, palladium, or rhodium, and has a honeycomb structure. In the catalyst tube 42, oxygen is added when the atmospheric gas passes, and the organic component of the flux in the atmospheric gas is decomposed into carbon dioxide (CO ₂ ), water (H ₂ O), and the like by the catalyst.

  The radiator unit 39 includes a chamber 51, an internal chamber 52 provided in the chamber 51, a U-shaped pipe 53 that communicates the chambers, an axial fan 54, and a recovery box 55. The radiator 39 cools the atmospheric gas and condenses and recovers flux components and the like in the atmospheric gas after passing through the catalyst tube 42.

  The chamber 51 is a space into which the atmospheric gas that has passed through the catalyst tube 42 first flows. The internal chamber 52 is a space provided in the chamber 51 and formed by partitioning the space of the chamber 51. The U-shaped pipe 53 communicates between the chambers. The axial fan 54 is a cooling fan and cools the radiator unit 39. The collection box 55 is disposed below the U-shaped pipe 53 and collects a flux component condensed by cooling.

  FIG. 6 is a left side view of the flux recovery unit 41. As shown in FIG. 6, the U-shaped pipe 53a has two open ends, one open end is connected to the bottom surface of the chamber 51, and the other open end is connected to the bottom surface of the internal chamber 52a. And the internal chamber 52a communicate with each other via a U-shaped pipe 53a.

  Of the two open ends of the U-shaped pipe 53b, one open end is connected to the bottom surface of the internal chamber 52a, the other open end is connected to the bottom surface of the internal chamber 52b, and the internal chamber 52a and the internal chamber 52b are It communicates via U-shaped piping 53b. One open end of the pipe 61 communicating with the inside of the reflow furnace is connected to the bottom surface of the internal chamber 52b.

  The valve 57 controls the outflow of the atmospheric gas by opening and closing. The heater unit 62 has a temperature that does not affect the temperature environment in the reflow furnace before the atmospheric gas that has passed through the radiator 39 returns to the reflow furnace via the pipe 61, for example, the reflow furnace temperature. It is a heating means which heats to the same extent.

  FIG. 7 is a top view of the flux collection unit 41. As shown in FIG. 7, in the radiator section 39, the open ends of a plurality of U-shaped pipes 53 are respectively connected to the chamber 51, the internal chamber 52a, and the internal chamber 52a, the internal chamber 52b. 51, connected to the internal chambers 52a to 52b, and the chamber 51 and the internal chamber 52a, and the internal chamber 52a and the internal chamber 52b communicate with each other via a plurality of U-shaped pipes 53, respectively.

FIG. 8 is a perspective view of the radiator unit 39. In the radiator section 39, as shown in FIG. 8, the atmospheric gas flows along a route of pipe 50 → chamber 51 → pipe 53a → internal chamber 52a → pipe 53b → internal chamber 52b → pipe 61 → (into the reflow furnace). . In addition,
An arrow L in FIG. 8 indicates the flow of the atmospheric gas. For convenience of explanation, the illustration of the four U-shaped pipes 53 is omitted in FIG.

  In the circulation path of the atmospheric gas, a high-heat gas of about 400 ° C. heated by the gas decomposition unit 38 is circulated in the pipe 50. In the chamber 51, the atmospheric gas that has flowed in is gradually cooled and flows into the pipe 53a. In the pipe 53a, the atmospheric gas flowing from the chamber 51 is further cooled.

  In the internal chamber 52a, the gas flowing in from the pipe 53a is heated. Since the internal chamber 52 a is provided in the chamber 51, the temperature environment is higher than the temperature environment in the pipe 53 a due to the hot gas flowing into the chamber 51.

  In the pipe 53b, the gas flowing from the internal chamber 52a is cooled. In the internal chamber 52b, the gas flowing in from the pipe 53b is heated. Since the internal chamber 52 b is provided in the chamber 51, the temperature environment is higher than the temperature environment in the pipe 53 b due to the high-temperature gas flowing into the chamber 51.

  In the circulation path of the atmospheric gas, the gas temperature is changed from the pipe 50 to the chamber 51 (temperature drop) → the pipe 53a (temperature drop) → the internal chamber 52a (temperature rise) → the pipe 53b (temperature drop) by repeating the heating and cooling described above. ) → Internal chamber 52b (temperature rise) → pipe 61 → (into the reflow furnace)

  That is, in the atmosphere gas flow path, the atmosphere gas is cooled and condensed to collect the flack components and the like in the atmosphere gas while performing at least two cycles of raising and lowering the gas temperature. Thus, the flux component can be efficiently condensed and recovered by performing the cycle of raising and lowering the gas temperature a plurality of times.

  FIG. 9 is a graph showing the behavior of the gas temperature in the radiator unit 39. In addition, a measurement point is the position of T1-T7 shown in FIG. 5 and FIG. That is, T1 indicates the temperature of the pipe 50. T2 indicates the temperature at the position where the chamber 51 and one open end of the U-shaped pipe 53a are joined. T3 indicates the temperature at the position where the other open end of the U-shaped pipe 53a and the internal chamber 52a are joined. T4 indicates the temperature at the position where the internal chamber 52a and one open end of the U-shaped pipe 53b are joined. T5 indicates the temperature at the position where the other open end of the U-shaped pipe 53b and the internal chamber 52b are joined. T6 indicates the temperature at the position where the internal chamber 52b and one open end of the pipe 61 are joined. T7 indicates the temperature of the position of the pipe 61 before returning to the reflow furnace.

As shown in FIG. 9, the ambient gas temperature is lowered at T1 to T2 and T2 to T3. At T3 to T4, the ambient gas temperature is rising. In T4 to T5, the ambient gas temperature is decreasing. At T5 to T6, the ambient gas temperature is rising. In T6 to T7, the atmospheric gas temperature is decreasing. That is, it can be confirmed that the gas temperature changes in the gas flow path as follows.
Piping 50 to chamber 51 (T1 to T2) ... Temperature drop Piping 53a (T2 to T3) ... Temperature drop Internal chamber 52a (T3 to T4) ... Temperature rise Piping 53b (T4 to T5) ... Temperature drop Internal chamber 52b (T5 to T6) ... Temperature rise Pipe 61 (T6 to T7) ... Temperature drop

  The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, in the above-described embodiment, nitrogen gas is used as the atmospheric gas, but the present invention is not limited to this. For example, air may be used as the atmospheric gas. When air is used, the atmospheric gas may not be returned to the reflow furnace again after passing through the flux recovery unit. For example, three or more internal chambers may be provided in the chamber.

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. It is a bottom view of the reflow apparatus by one Embodiment of this invention. It is a front view of the flux collection | recovery unit by one Embodiment of this invention. It is a left view of the flux collection unit by one Embodiment of this invention. It is a top view of the flux collection | recovery unit by one Embodiment of this invention. It is a perspective view of the radiator part by one Embodiment of this invention. It is the graph which plotted the temperature of the atmospheric gas of a measurement point.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Carrying in port 12 ... Carrying out port 14 ... Forced cooling unit 15 ... Upper heating device 16 ... Main heating source 17 ... Sub heating source 18 ... Axial flow blower 19 ... -Heat storage member 20 ... Hot air circulation duct 21 ... Opening 31 ... Conveyor 32a-32d ... Piping 35 ... Lower heating device 38 ... Gas decomposition part 39 ... Radiator part 40 ... Piping 41 ... Flux recovery unit 42 ... Catalyst pipe 43 ... Heating unit 50 ... Piping 51 ... Chamber 52, 52a, 52b ... Internal chamber 53, 53a, 53b ...・ U-shaped piping 54 ... Axial fan 55 ... Recovery box 61 ... Piping 62 ... Heater

Claims (3)

In the reflow apparatus in which the atmospheric gas taken out from the inside of the reflow furnace in one or more zones passes through the flux recovery unit and is returned again into the reflow furnace.
The flux recovery unit includes a gas decomposition unit having a catalyst tube for decomposing a flux component in the atmosphere gas, and a heating unit for heating the atmosphere gas before the atmosphere gas passes through the catalyst tube. ,
A reflow apparatus characterized in that the heating means starts heating after a predetermined time has elapsed since the main switch of the reflow furnace was turned on. The reflow apparatus according to claim 1, wherein the heating of the heating means is finished after a predetermined time has elapsed since the main switch of the reflow furnace was turned off. The flux recovery unit is
The reflow apparatus according to claim 1, further comprising a radiator section that cools the atmospheric gas that has passed through the gas decomposition section and condenses and collects a flux component.

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