JP2009004436A - Reflow apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To assure a temperature difference between the surface temperature of the soldering surface of a substrate and the surface temperature of the non-soldering surface of the substrate when reflow soldering is performed on one side of the surface. <P>SOLUTION: A heating section 15 and a housing section 35 are provided through a conveyance way 41. The heating section 15 heats the reflow surface W1 of an article W to be heated. The housing section 35 has an open surface 36 in close proximity to the conveyance way 41, and a closed surface 37 facing the open surface 36. Since a distance from the conveyance way 41 to the closed surface 37 of the housing section 35 is longer than that from the conveyance way 41 to a radiation panel 19, the temperature of the housing section 35 can be made lower than that of the heating section 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflow apparatus, and more particularly, to a reflow apparatus that performs reflow soldering on one side of a printed wiring board.

  A reflow apparatus is used for supplying solder to an electronic component or a printed circuit board in advance, transporting the printed circuit board into a reflow furnace by a transport conveyor, and performing soldering.

  The reflow apparatus includes a transport conveyor for transporting an object to be heated, such as a printed wiring board, and a reflow furnace main body into which the substrate is transported 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, and desired soldering can be performed by controlling the surface temperature of the substrate according to a desired temperature profile.

  Each of the heating zones is provided with a heating unit including, for example, a blower or a radiation panel. For example, as schematically shown in FIG. 8, when reflow soldering is performed on one surface of a heated body W such as a printed wiring board on which the electronic component 101 is mounted (hereinafter, the surface on which the reflow soldering is performed on the heated body W). The heating unit 102 heats the heated object W by blowing hot air or irradiating infrared rays on the reflow surface W1 and melts the solder on the reflow surface W1. Adhere to the electrode. Since the electronic component 101 mounted on the reflow surface W1 is exposed to a high temperature equal to or higher than the melting temperature of the solder, one having high heat resistance is used.

  By the way, a capacitor, IC (Integrated) having a low heat-resistant temperature is provided on a surface to which the object to be heated W is not soldered (hereinafter, a surface to which the object W is not reflowed is referred to as a non-reflow surface W2). When a reflow soldering is performed on the reflow surface W1 when a weak heat resistant component such as a circuit) is mounted, the surface temperature of the non-reflow surface W2 rises due to the influence of the reflow heating. Heat resistance may be impaired.

  Therefore, for example, in Patent Document 1 below, the lower surface of the substrate is heated entirely in a reflow furnace to perform reflow soldering on the lower surface of the substrate, and the cooling air is supplied to the upper surface of the substrate to cool the upper surface of the substrate. In Japanese Patent Application Laid-Open No. H10-260260 describes that the temperature rise of components mounted on the board is suppressed.

JP 2000-59020 A

  However, in the above-described Patent Document 1, it is necessary to appropriately install a plurality of deflecting plates so that the cooling air sent from the air supply fan can be uniformly supplied to the substrate. There was a problem that the configuration was complicated.

  In addition, by cooling the non-reflow surface of the substrate, there is a problem that the surface temperature of the reflow surface is likely to be lowered, and poor solder connection is likely to occur. In order to suppress a temperature rise on the non-reflow surface while maintaining a high temperature on the reflow surface, it is necessary to ensure a difference between the surface temperature of the reflow surface and the surface temperature of the non-reflow surface. However, it is difficult to secure the temperature difference by controlling the surface temperatures of the reflow surface and the non-reflow surface.

  Accordingly, an object of the present invention is to secure a temperature difference between a reflow surface and a non-reflow surface of a heated object such as a substrate with a simple configuration, and to thermally protect a weak heat-resistant component mounted on the non-reflow surface. It is in providing the reflow apparatus which can do.

In order to solve the above-described problem, the present invention is such that a reflow furnace is sequentially divided into a plurality of zones along a conveyance path of a heated object to be conveyed, and the heated object is heated or cooled in the plurality of zones. In the reflow apparatus for performing soldering on one side of the heated object,
The zone for heating the object to be heated is
A heating unit having a radiation panel;
A housing portion having an opening surface close to the conveyance path and a closing surface facing the opening surface;
The heating unit and the case unit are provided to face each other via a conveyance path, and a conveyance path is provided between the heating unit and the case unit,
The reflow apparatus is characterized in that the distance from the conveyance path to the closed surface of the casing is longer than the distance from the conveyance path to the radiation panel.

  In this invention, since the distance from the conveyance path to the closed surface of the casing is longer than the distance from the conveyance path to the radiation panel, the temperature in the casing in the zone is made lower than the temperature in the heating section. be able to.

  In this invention, it is preferable that a housing | casing part has a gas introduction part which introduces the gas for reducing the temperature in a housing | casing part. This is because the temperature inside the casing of the zone can be further reduced.

  Furthermore, in this invention, it is preferable that a shielding plate for shielding hot air from the heating unit is provided between the heating unit and the housing unit. This is because by suppressing the mutual movement of the atmosphere of the heating unit and the casing, the difference between the temperature in the casing of the zone and the temperature in the heating unit can be further increased.

  According to this invention, since the temperature in the casing portion of the zone and the temperature in the heating portion can be differentiated with a simple configuration, the surface temperature of the reflow surface and the surface temperature of the non-reflow surface of the heated object The difference can be ensured between. Therefore, it is possible to suppress the temperature rise of the non-reflow surface while heating the reflow surface of the heated object such as the substrate to a high temperature, so that the heat resistance limit of the weak heat-resistant component mounted on the non-reflow surface is exceeded. It can prevent and heat-protect weak heat-resistant parts.

  Hereinafter, embodiments of the present invention will be described 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. An object to be heated, in which solder and electronic components for surface mounting are mounted on one side of the printed wiring board and weak heat-resistant components are mounted on the other side, is placed on the conveyor and is carried into the reflow apparatus from the carry-in entrance 11. The The conveyor conveys the object to be heated in the arrow direction (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, six zones Z1 to Z6 along a conveyance path from the carry-in entrance 11 to the carry-out port 12, and these zones Z1 to Z6 are arranged in-line. A flux collection system 13a is provided on the carry-in side, and flux collection systems 13b and 13c are provided on the carry-out side. Five zones Z1 to Z5 from the entrance side are heating zones, and the zone Z6 on the exit side is a cooling zone. A forced cooling unit 14 is provided in relation to the cooling zone Z6. The number of zones is an example, and other numbers of zones may be provided.

  The plurality of zones Z1 to Z6 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 is time, and the vertical axis is the surface temperature of the object to be heated. 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 heated object is heated from room temperature to a preheating portion R2 (for example, 150 ° C. to 170 ° C.). The preheating part R2 is a period for performing isothermal heating, activating the flux, removing the oxide film on the surface of the electrode and solder powder, and eliminating heating unevenness of the heated object. 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 this reflow apparatus, the zone Z1 mainly takes charge of the temperature control of the temperature raising portion R1 in FIG. The temperature control of the preheating portion R2 is mainly handled by the zones Z2 and Z3. The zones Z4 and Z5 are responsible for temperature control of the main heating unit R3. The zone Z6 is responsible for temperature control of the cooling unit R4.

  Each of the heating zones Z <b> 1 to Z <b> 5 includes a heating unit 15 and a housing unit 35. The heating unit 15 and the housing unit 35 are provided to face each other via the conveyance path, and the heated object passes along the conveyance path 41 provided between the heating unit 15 and the housing unit 35. Each heating section 15 of the heating zones Z1 to Z5 is provided on one side of the conveyor, for example, on the lower side of the conveyor, and each housing section 35 of the heating zones Z1 to Z5 is on the other side of the conveyor. For example, it is provided in the upper side of a conveyance conveyor. The reflow surface to be heated and reflowed is conveyed so as to face the heating unit 15, and hot air is blown from the heating unit 15 to the reflow surface of the heated object.

An example of the configuration of the heating zones Z1 to Z5 will be described with reference to FIGS. For example, the configuration of the zone Z5 is shown in FIGS. 3 and 4, and FIG. 4 is a cross-sectional view taken along the broken line II ′ of FIG. Within a facing gap between the heating unit 15 and the housing unit 35, a heated object W in which solder and a surface mounting electronic component are mounted on the reflow surface W1 and a weak heat-resistant electronic component is mounted on the non-reflow surface W2, It is placed on the conveyor 41 and conveyed. The conveyor 41 is composed of a pair of chain conveyors, for example, and the heated object W is placed on the conveyor pins protruding from the chain conveyor. An atmosphere gas such as nitrogen (N ₂ ) is filled in the heating unit 15 and the housing unit 35.

  The heating unit 15 includes a main heating source 16, a sub heating source 17, a blower 18, a radiation panel 19, a hot air circulation duct 20, an opening 21, and the like. The main heating source 16 and the sub heating source 17 are composed of, for example, an electric heater, and heat the atmospheric gas in the heating unit 15. The main heating source 16 also heats the radiation panel 19.

  The blower 18 includes a fan and a motor that rotationally drives the fan. As the fan, for example, a turbo fan or a sirocco fan can be used.

  The radiant panel 19 is made of, for example, aluminum, and has a large number of ventilation holes through which air from the blower 18 passes. Hot air (heated atmospheric gas) through the ventilation holes passes through the opening 21 and is uniformly blown to the reflow surface W1 of the heated object W. Thereby, the reflow surface W1 of the to-be-heated body W is heated uniformly, without temperature irregularity. In addition, you may irradiate infrared rays.

  Hot air is circulated by the blower 18. That is, hot air is passed through the path of (main heating source 16 → radiation panel 19 → opening 21 → heated body W → hot air circulation duct 20 → sub-heating source 17 → hot air circulation duct 20 → blower 18 → main heating source 16). Circulates.

  The holes 22a and 22b provided in the lower part of the heating unit 15 are holes for flux collection, and although not shown, a collection container is connected through a hose.

  A housing part 35 is provided on the opposite side of the heating part 15 via the transport conveyor 41. The housing part 35 is closed from the opening surface 36 close to the transport conveyor toward the closing surface 37 facing the opening surface 36 to form a space inside the housing part 35. For example, a gas introduction part 38 and a temperature sensor 39 are provided on the closing surface 37 of the housing part 35.

  The distance from the transport conveyor 41 to the closing surface 37 of the housing unit 35 is configured to be longer than the distance from the transport conveyor 41 to the radiation panel 19. Thereby, since the space volume in the housing part 35 can be made larger than the space volume in the heating part 14, the heat spread from the heating part 15 into the housing part 35 is diffused, and the inside of the housing part 35 is diffused. Can be made lower than the temperature in the heating section 15, and a temperature difference can be made. Unlike the configuration of the present invention, when the distance to the closing surface 37 of the housing portion 35 is shorter or the same as the distance from the transport conveyor 41 to the radiation panel 19, the space in the housing portion 35 is narrow. Heat from the heating unit 15 tends to be trapped.

The gas introduction part 38 is a hole through which an atmospheric gas for lowering the temperature in the housing part 35 is introduced from the outside. This atmospheric gas is an atmospheric gas in a room temperature range lower than the temperature in the housing part 35, and, for example, nitrogen (N ₂ ) is used in accordance with the atmospheric gas filled in the housing part 35. Although the temperature in the casing 35 becomes high due to the influence of hot air from the heating section 15, the temperature rise in the casing 35 is suppressed by introducing nitrogen (N ₂ ) at normal temperature from the gas introduction section 38. can do. Therefore, the difference between the temperature in the housing part 35 and the temperature in the heating part 15 can be further increased.

Nitrogen (N ₂ ) gas from the gas introduction part 38 and hot air from the heating part 15 are agitated in the casing part 35, and the temperature in the casing part 35 becomes substantially uniform. The temperature in the housing part 35 is detected by a temperature sensor 39 that performs temperature detection. Although details will be described later, the flow rate of nitrogen (N ₂ ) introduced from the gas introduction unit 38 may be adjusted based on the temperature detected by the temperature sensor 39.

  In addition, arrangement | positioning of the gas introduction part 38 and the temperature sensor 39 which are shown in FIG. 3 is an example, Comprising: The installation location may be another location. A plurality of gas introduction portions 38 and temperature sensors 39 may be provided.

As shown in FIG. 4, shielding plates 40 a and 40 b for shielding hot air from the heating unit 15 are provided between the heating unit 15 and the housing unit 35. The shielding plates 40 a and 40 b are provided so as not to overlap with the transport conveyor 41, and are provided, for example, in parallel with the opening surface 36 of the housing unit 35. Since the shielding plate 40a and the shielding plate 40b block the portions other than the transport conveyor 41 and the heated object W between the heating unit 15 and the housing unit 35, the inside of the heating unit 15 and the housing unit 35 of this part are closed. The movement of nitrogen (N ₂ ) inside is suppressed. Therefore, the mutual influence of the temperature in the heating part 15 and the temperature in the housing | casing part 35 becomes small, and these temperature differences can be enlarged more.

  Although not shown, the shielding plates 40a and 40b are provided so as to shield the facing gap between the heating unit 15 and the housing unit 35 from the inner wall of the outer case of the reflow device toward the transport conveyor 41, for example. Also good.

  As described above, according to the embodiment of the present invention, since the temperature in the heating unit 15 and the temperature in the housing unit 35 can be made different with a simple configuration, the reflow surface W1 of the object to be heated W1. And a non-reflow surface W2 can ensure a temperature difference. Therefore, the reflow soldering can be performed on the reflow surface W1 without damaging the weak heat-resistant component mounted on the non-reflow surface W2.

Next, an example of adjusting the flow rate of nitrogen (N ₂ ) introduced from the gas introduction unit 38 will be described with reference to FIG. As shown in FIG. 5, nitrogen (N ₂ ) is supplied through a gas introduction part 38 to the respective housing parts 35 of the zones Z1, Z2, Z3, Z4, and Z5 that are responsible for heating. Nitrogen (N ₂₎ nitrogen from generator 45 (N ₂₎ is separated into the main supply and the sub-supply by a branch unit 46. For example, nitrogen (N ₂ ) is generated by vaporizing ultra-low temperature liquefied nitrogen.

For example, the sub supply path is branched into five, and a valve V1, a valve V2, a valve V3, V4, and V5 that are electronically controllable are provided for each branch, and are connected to the gas introduction unit 38 of each zone. By switching the valves V1, V2, V3, V4 and V5, the conduction and shut-off of nitrogen (N ₂ ) to each zone are controlled. Although not shown, a regulator, a pressure sensor, and the like are disposed in the nitrogen (N ₂ ) supply path to each zone.

The flow rate of nitrogen (N ₂ ) introduced from the gas introduction unit 38 can be adjusted by the control unit. The control unit compares the temperature detection result in the casing 35 supplied from the temperature sensor 39 with the target temperature (set temperature) in the casing 35, and the introduced nitrogen (N ₂ ). Adjust the flow rate. For example, when the detected temperature is higher than the set temperature, control is performed to increase the flow rate of introduced nitrogen (N ₂ ), and when the difference between the detected temperature and the set temperature becomes small, the flow rate is introduced. The nitrogen (N ₂ ) flow rate is controlled to decrease. It should be noted that even if the flow rate of introduced nitrogen (N ₂ ) is increased, the flow rate is set so as not to be actively blown to the heated object W. Such control is performed by, for example, PID control, and the temperature in the housing portion 35 can be kept substantially at the set temperature. Although FIG. 4 shows an example in which the valve V5 is controlled by the controller for simplicity, it goes without saying that each of the valves V1, V2, V3, and V4 can be controlled.

Although not shown, a manual flow rate adjustment volume can be provided to adjust the flow rate of introduced nitrogen (N ₂ ). By adjusting the flow rate of nitrogen as described above (N _2), for example, the flow rate of the temperature is high zone in the housing portion 35, i.e. nitrogen as zone closer to the zone Z4 and the zone 5 responsible for the heating unit (N ₂₎ number Is done. In this way, nitrogen (N ₂ ) is introduced from the outside into the housing part 35 and the flow rate is adjusted to suppress a temperature rise in the housing part 35 and to keep the temperature inside the housing part 35 to some extent. Can be kept constant.

  FIG. 6 shows an example of an outline of surface temperature changes of the reflow surface W1 and the non-reflow surface W2 when the reflow soldering is performed on the heated object W using the reflow apparatus according to the embodiment of the present invention. The horizontal axis is time, the vertical axis is temperature, curves 3 and 4 show changes in surface temperature at different positions in the surface of the reflow surface W1, respectively, and curves 5 and 6 show the non-reflow surface W2. The changes in the surface temperature at different positions in the plane are respectively shown.

  As shown in FIG. 6, a temperature difference can be secured between the curves 3 and 4 and the curves 5 and 6. In particular, a sufficient temperature difference can be ensured between the reflow surface W1 and the non-reflow surface W2 even during the main heating part R3 in which the surface temperature of the heated object W is highest, so that the surface is mounted on the non-reflow surface W2. Reflow soldering can be performed on the reflow surface without damaging the weak heat resistant parts.

  Moreover, since the reflow surface W1 is heated uniformly, there is almost no temperature difference between the curve 3 and the curve 4, and the temperature nonuniformity of the reflow surface W1 is small. Similarly, since the non-reflow surface W2 is uniformly cooled, there is almost no temperature difference between the curve 5 and the curve 6, and the temperature unevenness in the surface of the non-reflow surface W2 is small. As described above, in the reflow device according to the embodiment, the surface temperature difference between the reflow surface W1 and the non-reflow surface W2 is ensured while the surface temperatures in the reflow surface W1 and the non-reflow surface W2 are kept substantially uniform. In addition, the weak heat resistant component can be thermally protected.

FIG. 7 shows an example of the surface temperature difference of the heated object W in the reflow device according to the embodiment of the present invention and the reflow device according to the comparative example in which a panel is provided in the housing portion 35. In addition, the reflow apparatus of the comparative form is provided with a panel in the housing part 35 so as to be substantially parallel to the closing surface 37, so that the distance from the transport conveyor 41 to the panel in the housing part 35, and the transport conveyor The distance from 41 to the radiation panel 19 in the heating unit 15 is substantially equal. 7 indicates the surface temperature difference (° C.) between the reflow surface W1 and the non-reflow surface W2 of the heated object W in the zone Z5, and when nitrogen (N ₂ ) is supplied into the casing portion 35. These are the measured values when not. Note that the supply amount of nitrogen (N ₂ ) is 100 nl / min.

  As shown in FIG. 7, the reflow device according to the embodiment has no panel in the housing portion 35, and a space is formed between the transport conveyor 41 and the closing surface 37 of the housing portion 35. The temperature difference can be made larger than that of the reflow apparatus of the form.

Further, by supplying nitrogen (N ₂ ), it is possible to prevent a temperature rise in the casing 35 and to increase the difference in surface temperature between the reflow surface W1 and the non-reflow surface W2.

In the zone Z5 that is responsible for the main heating unit, for example, the surface temperature of the reflow surface W1 is heated to 220 ° C. to 240 ° C. at the peak temperature, but in one embodiment in which nitrogen (N ₂ ) is supplied into the housing unit 35. The peak temperature of the non-reflow surface W2 of the heated object W can be suppressed to about 190 to 210 ° C., for example. If the heat resistant temperature of a weak heat resistant component such as an IC mounted on the non-reflow surface W2 is about 230 ° C. or less, for example, the difference between the surface temperature of the non-reflow surface W1 and the heat resistant temperature of the weak heat resistant component may be secured. Therefore, the weak heat resistant component can be thermally protected.

  Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, an inert gas other than nitrogen gas or air may be used as the atmospheric gas instead of nitrogen gas. In addition, the gas introduction part 38 provided in the housing part 35 is provided at least in a zone that is responsible for heating of the object to be heated, but it is not necessary to provide the gas introduction part 38 in all zones that are responsible for heating. You may provide the gas introduction part 38 only in the zone which it takes charge of. In addition, the heating unit 15 may be provided on the upper side of the conveyance path 41 and the housing unit 35 may be provided on the lower side.

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 in one embodiment of this invention. It is a schematic diagram for explaining the flow rate adjustment of the N ₂ introduced in the embodiment of the present invention. FIG. 5 is a cross-sectional view taken along line I-I ′ of FIG. 4. It is a graph which shows the example of the surface temperature change of the reflow surface of the to-be-heated body at the time of reflow in one embodiment of this invention, and a non-reflow surface. It is a figure which shows the difference of the surface temperature of the reflow surface of a to-be-heated body, and the non-reflow surface in one zone of one Embodiment of this invention, and a comparative form. It is a basic diagram for demonstrating the reflow heating in the heating zone of a reflow furnace.

Explanation of symbols

Z1 to Z9 Zone W Object to be heated W1 Reflow surface W2 Non-reflow surface 11 Carrying in port of heated object 12 Carrying out port of heated object 15 Heating unit 16 Main heating source 17 Sub heating source 18 Blower 19 Radiation panel 20 Hot air circulation duct 21 Opening portion 35 Housing portion 36 Opening surface 37 Closure surface 38 Gas introduction portion 39 Temperature sensor 40a, 40b Shield plate 41 Conveyor

Claims (5)

A reflow furnace is sequentially divided into a plurality of zones along the conveyance path of the heated object to be conveyed, and soldering is performed on one surface of the heated object by heating or cooling the heated object in the plurality of zones. In the reflow device that performs
The zone for heating the object to be heated is
A heating unit having a radiation panel;
A housing portion having an opening surface close to the conveyance path and a closing surface facing the opening surface;
The heating part and the housing part are provided to face each other via the transport path, and the transport path is provided between the heating part and the housing part,
The reflow apparatus characterized in that a distance from the conveyance path to the closed surface of the casing is longer than a distance from the conveyance path to the radiation panel.   The reflow apparatus according to claim 1, wherein the housing part includes a gas introduction part that introduces a gas for lowering the temperature in the housing part.   The reflow apparatus according to claim 2, wherein the flow rate of the gas introduced from the gas introduction unit is adjustable for each of the plurality of zones. A temperature measuring unit for measuring the temperature in the casing, and
A control unit for adjusting the flow rate of the gas introduced from the gas introduction unit,
The reflow apparatus according to claim 2, wherein the control unit adjusts the flow rate of the gas based on a comparison between a measured temperature measured by the temperature measuring unit and a desired set temperature.   The reflow apparatus according to claim 1, wherein a shielding plate for shielding hot air from the heating unit is provided between the heating unit and the housing unit.

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