WO2008120526A1

WO2008120526A1 - Reflow device

Info

Publication number: WO2008120526A1
Application number: PCT/JP2008/053889
Authority: WO
Inventors: Masaki Iijima; Fumihiro Yamashita
Original assignee: Tamura Corporation; Tamura Fa System Corporation
Priority date: 2007-03-29
Filing date: 2008-02-27
Publication date: 2008-10-09
Also published as: JP2008246515A

Abstract

An inlet for N2 for cooling is provided below lower heating devices. N2 is supplied from below to the respective lower heating devices of zones (Z3-Z5) for performing preheating. N2 supplied from an N2 generation device (45) is divided by a branch section (46) into main supply and sub-supply for cooling. The sub-supply route is branched to three, and each of the branched routes has a valve (V3-V5) and a flow rate regulation volume (L3-L5). The conduction and interruption of the N2 for cooling relative to the zones (Z3-Z5) are controlled by switching the valves (V3-V5). In switching of lead-free solder to eutectic solder, N2 are introduced into the lower heating devices of the zones (Z3-Z5) to quickly lower the temperature of these zones.

Description

Specification

Technical field of reflow equipment

The present invention relates to a reflow apparatus applied to reflow or adhesive curing. Background art

Solder is supplied to the electronic component or printed wiring board in advance, and the substrate is transported to the reflow furnace by a conveyor, and soldered, or the electronic component is fixed on the substrate with a thermosetting adhesive. Reflow equipment is used for this purpose. In the reflow apparatus, desired soldering can be performed by controlling the surface temperature of an object to be heated, for example, a substrate, according to a desired temperature profile. When the production conditions are changed, for example, when changing to a different type of solder, it is required to improve the workability to cope with the changed solder within a short time.

Figure 6 shows an outline of the temperature profile. The horizontal axis is time, and the vertical axis is 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 heating section R 1 where the temperature rises due to heating, the next section is the preheating (preheating) section R 2 where the temperature is almost constant, and the next section is the main heating section R 3 The last section is the cooling section R4.

The temperature raising portion R 1 is a period in which the substrate is heated from room temperature to a preheating portion R 2 (for example, 1550 ° C. to 1700 ° C.). The preheating portion 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 the heating unevenness of the printed wiring board. This heating section R 3 (for example, 2 20 ° C to 2 40 ° C at peak temperature) However, it is a period of melting and joining. In this heating part R3, the temperature must be raised to a temperature exceeding the melting temperature of the solder. Even if the main heating part R 3 has passed the preheating part R 2, since there is uneven temperature rise, heating to a temperature exceeding the solder melting temperature is required. Last cooling part R

4 is a period in which the printed wiring board is rapidly cooled to form a solder composition.

In Fig. 6, curve 1 shows the temperature profile of lead-free solder. The temperature profile for 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 part R2 is considered to be higher than that of eutectic solder.

Furthermore, curve 3 in FIG. 6 shows a profile when a thermosetting adhesive for fixing an electronic component to a printed wiring board is cured. Compared to solder, the adhesive has a lower set temperature and does not require complicated temperature control. \ The temperature is controlled so that the profile is either curve 1 or curve 2 depending on the type of solder used (lead-free solder and eutectic solder) and the type of printed wiring board. If the reflow device is used for the adhesive curing process, the profile of curve 3 is used. In the case of a reflow device, increasing the set temperature can be done in a relatively short time, but since it has a heat insulating structure, it takes time to lower the temperature.

For example, in Japanese Patent Application Laid-Open No. 11-1 4 5 6 11, the temperature of a specific zone can be set in a short time by turning off the heating heater and sending outside air or inert gas to the specific zone. It is described that it is reduced. Japanese Patent Application Laid-Open No. 6-170 5 2 4 discloses that high warm air in a furnace is forcibly discharged and cold air is supplied into the furnace to forcibly cool it. Are listed.

As explained with reference to Fig. 6, in order to change the solder type from lead-free solder to eutectic solder, when the temperature of the reflow furnace is lowered, the preheating part R 2 in the temperature profile It is necessary to lower the temperature of the responsible zone, and it is important how the temperature of the zone can be lowered within a short time. However, those described in Japanese Patent Application Laid-Open Nos. 11-1 14 5 6 1 1 and 6 1 700 5 24 are different from the preheating unit R 2 in the main heating unit R 3. It does not reduce the temperature of the furnace in a specific zone, so the configuration is complicated, the time required to lower the temperature is long, and the amount of gas used for cooling is large. There was a problem such as.

Therefore, an object of the present invention is to rapidly reduce the temperature of the zone that handles the preheating portion among a plurality of zones arranged in-line, thereby reducing the type of solder without complicating the configuration. An object of the present invention is to provide a reflow apparatus capable of performing switching at high speed and efficiently. Disclosure of the invention

In order to solve the above-described problems, the present invention is configured such that the reflow furnace is sequentially divided into a plurality of zones along the conveyance path of the heated object to be conveyed, and is conveyed by controlling the temperature of the plurality of zones. In the reflow device that controls the temperature of the heated object with a desired profile,

When the set temperature in a zone is changed among multiple zones, the change in the set temperature is large. One or more zones introduces a gas that introduces a lower temperature gas than the gas in the zone. Set up a section,

This is a reflow apparatus in which a low temperature gas is introduced into the zone through a gas introduction unit to reduce the temperature of one or a plurality of zones in a short time. Specifically, the profile during reflow consists of a heating section, preheating section, main heating section, and cooling section, and is set in a zone that handles heating of the heating section, preheating section, and main heating section. One or more zones with large temperature changes are introduced with a lower temperature gas than the gas in the zone.

Furthermore, in order to enable cooling in a short time, the gas in one or a plurality of zones that are responsible for heating the preheating section is circulated in the cooling section provided outside the reflow furnace. Brief Description of Drawings

FIG. 1 is a schematic diagram showing an outline of a reflow apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an example of the configuration of one zone in one embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining a method of performing cooling by supplying N ₂ in one embodiment of the present invention.

FIG. 4A and FIG. 4B are schematic diagrams for explaining the arrangement of the inlets and holes provided in the embodiment of the present invention.

FIG. 5 is a schematic diagram showing an example of the set temperature of each zone.

FIG. 6 is a graph showing an example of a temperature profile during reflow. BEST MODE FOR CARRYING OUT THE INVENTION

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, on which electronic components for surface mounting are mounted on both sides of the printed wiring board, is placed on the conveyor and is carried into the reflow apparatus from the carry-in port 11. The transport conveyor moves at the specified speed in the direction of the arrow (see Fig. 1 The object to be heated is transported from the left to the right.

A reflow furnace, for example, is divided into 9 zones Z 1 to Z 9 along the transfer path from the carry-in entrance 1 1 to the carry-out exit 1 2, and these zones Z 1 to Z 9 are arranged in-line. ing. A flux recovery system 1 3 a is provided on the carry-in side, and flux collection systems 1 3 b and 1 3 c are provided on the carry-out side. 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. There is a forced cooling unit 14 associated with cooling zones Z8 and Z9. The number of zones is an example, and other numbers of zones may be provided.

The plurality of zones Z 1 to Z 9 described above controls the temperature of the object to be heated according to the temperature profile during reflow. The zones Z 1 and Z 2 are mainly responsible for the temperature control of the temperature riser R 1 in Fig. 6. The temperature control of the preheating section R 2 is mainly handled by the zones Z 3, Z 4 and Z 5. Zones Z 6 and Z 7 are responsible for temperature control of this heating section R 3. 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 and a lower heating device 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 Z 1, and hot air is blown to the object to be heated conveyed from the lower heating device 35.

In one embodiment of the present invention, when switching from lead-free solder to eutectic solder, heating is stopped and ambient temperature ambient gas (nitrogen: N ₂ ) is externally applied to the temperature of the pre-heated portion. The temperature in the furnaces of zones Z 3, Z 4 and Z 5 is lowered in a short time by supplying them into the lower heating devices of zones Z 3, Z 4 and Z 5 that are in charge of control. In this case, Z The amount of N ₂ introduced may be controlled so that more N ₂ is introduced in zones closer to 6. For example, the introduction amount (flow rate) of zones Z 3, Z 4, and Z 5 is controlled as (1: 2: 4). Further, N ₂ may be supplied only to the zone Z 6 that is adjacent to the zone Z 6 that is in charge of this heating section. This is because the temperature of the zone Z 5 is not easily lowered due to the influence of the zone Z 6 which is set to a high temperature. The operation of the blower does not stop even when switching. Further, not only the lower heating device 35 but also cooling N ₂ may be introduced from the upper heating device 15.

In one embodiment of the present invention, the atmosphere gas N ₂ is always circulated and cooled in connection with the upper heating devices of the zones Z 4 and Z 5, including during reflow and switching of the solder type. is doing. The constant circulation cooling is performed to simplify the configuration. If the heating is stopped when switching from lead-free solder to eutectic solder, the temperature of zones Z 4 and Z 5 can be lowered in a short time by the action of cooled N ₂ . Thus, in one embodiment, for heating zones Z 4 and Z 5, switching from lead-free solder to eutectic solder using _both the external supply of N _{2 and} the cooling action of N ₂ Sometimes the temperature can be lowered in a short time. Note that an inert gas other than N ₂ may be used as the atmospheric gas.

As described above, N ₂ for cooling is introduced from the lower heating device, but the upper and lower heating devices move back and forth with respect to the gas flow, so the cooling effect of introducing N ₂ for cooling is not Also spread to the upper heating device. Similarly, the cooling effect of the circulating cooling method in the upper heating device also affects the lower heating device.

An example of the heating apparatus will be described with reference to FIG. For example, the configuration of zone Z 5 is shown in FIG. Within the gap between the upper heating device 1 5 and the lower heating device 3 5, an object to be heated W with electronic components for surface mounting mounted on both sides of the printed wiring board is placed on the conveyor 4 1. Be transported. Up The partial heating device 15 and the lower heating device 35 heat the heated object W by jetting hot air to the heated object W. Infrared rays may be irradiated with hot air.

The upper heating device 15 includes a main heating source 16, a sub heating source 17, a blower, for example, an axial blower 18, a heat storage member 19, a hot air circulation duct 20, an opening 21, and the like. Hot air (heated atmospheric gas such as N ₂ ) is blown through the opening 21 to the article W to be heated. The main heating source 16 and the auxiliary heating source 17 are composed of, 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 object W to be heated.

Hot air is circulated by an axial blower 18. That is, (Main heating source 1 6 → Heat storage member 1 9 → Opening 2 1 → Substance to be heated W → Hot air circulation duct 2 0 → Sub heating source 1 7 → Hot air circulation duct 2 0 → Axial flow production 1 8 → Hot air circulates through the path of the main heating source 1 6).

In the hot air circulation path, for example, two holes 2 2 a as outlets and 2 2 b as inlets are provided in the upper two places, and Raje Turbotus 4 2 and hoses 4 3 a and 4 3 as external air-cooling devices are provided. Connect via b. The radiator box 42 has a structure in which a large number of fins are provided on the peripheral surface of a gas circulating pipe and a cooling fan is provided. For example, the hot air taken out from the hole 2 2 a is cooled by the radiator box 4 2 and taken into the upper heating device 15 in the zone Z 5 from the hole 2 2 b. An outlet (hole 2 2 a) force S is provided at a location where the pressure generated by the ventilation of the axial flow blower 1 8 is high, and an introduction port (hole 2 2 b) is provided at a location where the pressure is low. Gas circulates in the path including the lever box 42. At the bottom of the radiator box 4 2, a container 4 4 for collecting the flux is provided. The radiator box 4 2 cools the hot air even when the main heating source 16 and the auxiliary heating source 17 are operating. In this operating state, the main heating source 16 and the sub-heating source 17 are operated so that the temperature of the zone Z 5 becomes the set temperature. Therefore, when the solder is switched from lead-free solder to eutectic solder, if the main heating source 16 and sub-heating source 17 are de-energized, the temperature of the zone Z 5 can be quickly reduced by the cooling action of the radiator box 42. Can be lowered. Further, the radiator box 42 can also serve as a flux recovery device for the upper heating device 15. A method similar to the circulating cooling method in zone Z 5 is also applied to adjacent zone Z 4. The circulation cooling method may be applied to the lower heating device 35.

Further, an outside air introduction valve 23 is provided on the upper part of the upper heating device 15. An electric ball valve can be used as the outside air introduction valve 2 3. The outside air introduction valve 23 is turned on when switching from solder reflow to adhesive curing, and outside air is introduced. The temperature in the case of curing is lower than that of soldering and does not require N ₂ , so outside air is introduced when the power supply to the heating source is stopped and the supply of N ₂ is stopped.

In the case of zone Z 5, the outside air introduction valve is provided at one location of the upper heating device 15 and one location of the lower heating device 35. Similarly, each of the other zones Z 1 to Z 4 is provided with one outdoor air introduction valve in each of the upper and lower sides. In the case of zones Z 6 and Z 7, there are two outdoor air introduction valves at the top and bottom. A total of 18 outdoor air inlets are provided, and when the air is introduced, these outdoor air inlets are connected all at once.

The lower heating device 35 has the same configuration as the upper heating device 15 described above, and the description of the corresponding parts is omitted. The holes 3 6 a and 3 6 b provided in the lower part of the lower heating device 3 5 are holes for collecting the flux. However, the collection container is connected through a hose. Also, lower heating device

A cooling N ₂ inlet 3 7 is provided at the bottom of 3 5.

In addition, the atmosphere gas in the reflow furnace is led out from the lower heating device 35 to the flux recovery unit provided outside the reflow furnace, and the atmosphere gas is cooled by the flux recovery unit, and the flux contained in the atmosphere gas The components may be condensed and recovered and introduced again into the reflow furnace.

Although the flux recovery unit is not shown in the figure, for example, when atmospheric gas passes, oxygen is added and the organic component of the flux in the atmospheric gas is converted into carbon dioxide (C 0 ₂ ), water (H ₂ 0) by the catalyst. ), Etc., and a radiator section that cools the atmospheric gas and condenses and collects flux components in the atmospheric gas.

As shown in FIG. 3, N ₂ is supplied to the lower heating devices of the zones Z 3, Z 4, and Z 5 that are responsible for the preheating portion from below through the cooling N ₂ inlet. N ₂ from N ₂ generator 4 5 is separated into sub-supply for cooling the main supply by a branch unit 4 6. For example, N ₂ is generated by vaporizing ultra-low temperature liquefied nitrogen. Main supply and temperature control are performed even during transition.

The sub supply path is branched into three, and electronically controllable valves V 3, V 4 and V 5 and manual flow control volumes L 3, L 4 and L 5 are provided for each branch. By switching the valves V 3, V 4 and V 5, the conduction and shut-off of the cooling N _{2 to} the zones Z 3, Z 4 and Z 5 are controlled. In addition, the flow rate of N ₂ introduced can be adjusted by the flow rate adjusting volumes L 3, L 4 and L 5. For example, the flow rate of N ₂ is increased in the zone closer to zone Z 6 that is in charge of this heating unit. Although not shown, a regulator, a pressure sensor, etc. are arranged in the N ₂ supply path to each zone. Switching from lead-free solder to eutectic solder Sometimes, with respect to the lower heating device zone Z 3, Z 4 and Z 5, N ₂ is introduced, N ₂ for cooling from the lower enters the upper heating device 1 5, further comprising a Lage letterbox 4 2 Since it is cooled by the circulation path described above, the temperature of these zones can be lowered in a short time.

With reference to FIG. 4A and FIG. 4B, a hole for introducing gas or outside air to the outside provided in the reflow apparatus of one embodiment of the present invention will be schematically described. FIG. 4A shows the top surface of the reflow device, and FIG. 4B shows the bottom surface of the reflow device. Main N ₂ inlets a 1 to a 7 are formed on the upper surface of each zone, and main N ₂ inlets b 1 to b 7 are formed on the lower surface. The main N ₂ inlet is schematically represented by a white circle in Fig. 4A and Fig. 4B.

Holes c 41 and c 42 for connecting to the radiator box 4 2 are formed on the upper surface of the zone Z 4 and holes c 51 and c 52 for connecting to other radiator boxes are formed on the upper surface of the zone Z 5 Yes. The holes for connecting to the Raje Turbo are schematically represented by triangles in Fig. 4A and Fig. 4B.

Further, an inlet d 3 for cooling N ₂ is formed on the lower surface of the zone Z 3. Cooling N ₂ inlets d 4 and d 5 are formed on the lower surface of zone Z 4 and the lower surface of zone Z 5, respectively. The inlet for cooling N ₂ is schematically represented by a black circle in FIGS. 4A and 4B.

Further, outside air inlets e 1 to e 5 that are conducted when the temperature is lowered for curing are formed on the upper surfaces of the zones Z 1 to Z 5. Two outside air introduction ports e 61 and e 62 are formed on the upper surface of the zone Z 6, and two outside air introduction ports e 71 and e 72 are formed on the upper surface of the zone Z 7. Outside air inlets f 1 to f 72 are formed in the same manner on the lower surface, and a total of 18 outside air inlets are formed. The arrangement of the inlet and outlet shown in FIG. 4A and FIG. 4B is an example, and the installation location may be another location. However, the gas or air outlet is provided at a location where the pressure is increased by the operation of the blower, and the gas or air inlet is provided at a location where the pressure is reduced by the operation of the blower. In addition, an introduction port or a discharge port may be provided on the side surface of the heating device.

An example of the temperature setting for each zone in the embodiment of the present invention will be described with reference to FIG. In Fig. 5, the heater temperature (upper) represents the set temperature of the heater that constitutes the main heating source and sub-heating source of the upper heating device, and the heater temperature (lower) represents the main heating source of the lower heating device. And the set temperature of the heater that constitutes the auxiliary heating source. The set temperatures for lead-free solder, eutectic solder and curing are shown. In the case of lead-free solder, eutectic solder and hardening, the airflow of the axial blower of the upper heating device and the airflow of the axial flow blower of the upper heating device are set to medium (M id) in each zone. The transport speed is set to 0.9 (m / min). For example, in the case of lead-free solder, the heater temperature (upper) and heater temperature (lower) of zones Z3, Z4, and Z5, which handle the preheated part, are set to 190 ° C. In the case of eutectic solder, the heater temperature (top) and heater temperature (bottom) of zones Z 3, Z 4 and Z 5 are set to 160 ° C. Furthermore, in the case of curing, the heating zones Z 1 to Z 7 are set to 1550 ° C. The desired temperature (reflow) profile for lead-free solder can be obtained with the settings shown in Fig. 5, and the desired temperature (reflow) profile can be obtained for eutectic solder. The desired temperature profile for the case can be obtained.

For example, if the heater temperature is set to 150 ° C, the object to be heated (for example, If the heater temperature is set to 160 ° C, the temperature of the object to be heated will be approximately 140 ° C. When the heater temperature is set to 190 ° C, the temperature of the object to be heated is approximately 170 ° C to 180 ° C, and when the heater temperature is set to 245 ° C, When the temperature of the object is approximately 2 25 ° C and the heater temperature is set to 240 ° C, the temperature of the heated object is approximately 230 ° C.

Therefore, in the case of lead-free solder to eutectic solder, it is necessary to lower the temperatures of zones Z 3, Z 4 and Z 5 by 30 ° C. In the case of curing from lead-free solder, it is necessary to lower the temperatures of zones Z 3, Z 4 and Z 5 by 40 ° C. In one embodiment of the present invention, these temperature changes can be performed in a short time. For example, 30 minutes can be reduced to 15 to 20 minutes. According to the present invention described above, when it is necessary to change the set temperature of the reflow furnace, for example, when switching from lead-free solder to eutectic solder, the temperature of the zone having a large change in set temperature, for example, the temperature of the zone that handles the preheating portion. By rapidly reducing the value, the switching work can be performed in a short time and efficiently.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the cooling according to the present invention may be applied only to a zone serving as a terminal portion of the preheating portion adjacent to the main heating portion. The present invention can also be applied to temperature profile switching other than switching between lead-free solder and eutectic solder.

Claims

1. A reflow furnace is sequentially divided into a plurality of zones along the conveyance path of the heated object to be conveyed, and the temperature of the heated object to be conveyed is set to a desired profile by controlling the temperature of the plurality of zones. In reflow equipment controlled by

Among the plurality of zones, when changing the set temperature in the zone, the change in the set temperature is large. For one or more of the zones, the temperature is lower than the gas in the zone. A gas introduction part for introducing gas is provided,

The low temperature gas is introduced into the zone through the gas introduction part and fixed to 1

Or a reflow device that reduces the temperature of multiple zones in a short time.

2. The above-mentioned profile during reflow consists of the heating part, preheating part, main heating part and cooling part.

Among the zones that are responsible for heating the heating unit, the preheating unit, and the main heating unit, respectively, the gas in the zone is compared with one or more of the above zones having a large change in the set temperature. The reflow apparatus according to claim 1, further comprising a gas introduction unit that introduces a gas having a temperature lower than that of the first embodiment.

3. The reflow apparatus according to claim 1, wherein the low-temperature gas is introduced when the profile of the lead-free solder is switched to the profile of the eutectic solder.

4. The reflow device according to claim 3, wherein the introduction point of the low-temperature gas is provided at a location where the pressure generated by the blower is low.

5. Each heating device in the above zone is composed of an upper heating device and a lower heating device, and a counter gap between the upper heating device and the lower heating device is heated. It is configured to pass things,

2. The reflow device according to claim 1, wherein the gas introduction part is provided in one of the upper heating device and the lower heating device.

6. The reflow apparatus according to claim 1, wherein the gas in the one or more zones having a large change in the set temperature is circulated through a cooling unit provided outside the reflow furnace.

7. The reflow device according to claim 6, wherein the cooling section comprises a pipe through which the gas passes, a cooling fin provided on a peripheral surface of the pipe, and a collection section for collecting flux from the pipe.

8. The heating unit is a hot air jet type heating device having a heating source and a blower,

The gas is led out from a location where the pressure generated by the blower is high and supplied to the cooling unit, and the gas cooled by the cooling unit is introduced into the heating unit from a location where the pressure generated by the blower is low. A reflow device according to claim 6.

9. Each heating device in the zone is composed of an upper heating device and a lower heating device, and the heated object passes through a gap between the upper heating device and the lower heating device,

9. The reflow device according to claim 8, wherein the gas lead-out portion and the gas introduction portion are provided on one of the upper heating device and the lower heating device.