JP2011082282A - Reflow apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pollution-free reflow apparatus that is reduced in running cost and facilitates recovery of wastes having solder by using superheated steam as a heating medium. <P>SOLUTION: The reflow apparatus preheats a workpiece by using air as a heating medium, performs reflow soldering using the superheated steam as the medium, and cools the workpiece through supplied-air cooling. The high-temperature superheated steam generated from water by a high-frequency electromagnetic induction heater is introduced in a reflow chamber to fill the reflow chamber with the high-temperature superheated steam by using properties of room-temperature expansion of the superheated steam and to hold the reflow chamber in an oxygen-free state, the high-temperature superheated steam is jetted toward the workpiece to fuse solder, and the superheated steam having been used has its heat exchanged with supply water and is subjected to distillation processing, thereby collecting components scattered during the solder fusing, in distilled water. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflow apparatus.

  In the reflow method in which lead-free cream solder is printed on a printed circuit board and the components are mounted on the printed circuit board for soldering, an inert gas, especially nitrogen gas, is generally used as a heating medium to prevent solder oxidation. ing. In this case, since the heated nitrogen gas is repeatedly used, the concentration of flux components and fume components scattered when the solder is melted in the atmosphere increases not only to hinder soldering itself. There were problems such as adhering to the workpiece and condensing and accumulating in the low temperature part of the furnace. This situation arises from the need to reuse the used nitrogen gas without discarding it.

Many techniques have been proposed to remove this soldering waste and to reuse nitrogen gas (for example, Patent Documents 1, 2, 3, 4, and 5).
These technologies had the following commonality.
(1) In order to remove a flux component from a high-temperature medium after use at about 230 ° C. to 240 ° C. containing nitrogen gas, the medium must be cooled. For this purpose, each of these techniques includes a technique for inducing and cooling the medium outside the furnace or the heating chamber, and a complicated mechanism technique for collecting the substance condensed by cooling. In these techniques, when the reproduction medium is returned into the furnace or chamber, the medium having a low temperature must be heated again in order not to lower the internal atmosphere temperature, and an extra heating cost is required.
(2) Organic solvents that cannot be collected by the above cooling method are further decomposed and removed using a catalyst heated to about 400 ° C. In this case, the temperature of the medium is lowered and then returned to the chamber ( As a representative example, Patent Documents 4 and 5).

These are all open technologies designed for costly nitrogen gas recycling. Inert gases other than nitrogen gas are more expensive and cannot be used.
As other media, a technique using water vapor (Patent Document 6) and a technique using superheated steam (Patent Document 7) are disclosed. Since air molecules are excluded from an atmosphere filled with water vapor or superheated water vapor, the workpiece can be soldered in an oxygen-free state. Since these methods use water as the consumable, there is an advantage that the running cost is reduced as compared with the case of using nitrogen gas.
Of these techniques, the technique disclosed in Patent Document 6 is not yet widely used because the reflow furnace structure is complicated in order to prevent condensation that occurs easily.

  On the other hand, the technique disclosed in Patent Document 7 is a technique in which steam is introduced into a plurality of chambers and heated to generate superheated steam, and reflow soldering is performed while circulating the atmosphere with a fan.

However, this technique has the following problems in using superheated steam as a heating medium.
(1) There is no technology corresponding to the phase conversion of superheated steam Superheated steam is produced by using water as steam and further heating the steam. That is, 1 mol (18 grams) of water becomes 22.4 liters of water vapor at normal temperature and normal pressure, and the volume further increases in proportion to the temperature at normal pressure. That is, when superheated steam is used as a medium for reflow heating, a large amount of medium can be obtained using a small amount of water as a raw material, and the reflow chamber can be filled with high-temperature and high-pressure superheated steam. Superheated steam has a strong far-infrared heating effect, thereby realizing oxygen-free reflow. On the other hand, because of this property, high-temperature superheated steam filled in the heating chamber has a strong tendency to always leak out of the room, so it is necessary to take technical measures to capture and recover the amount of superheated steam that leaks after use. .
Conversely, when superheated steam is cooled, it condenses into water and the volume is extremely reduced. This means that if the superheated steam after being used for reflow heating is cooled, it can be recovered as a very small amount of water.
When superheated steam is used as a medium, the characteristic of phase conversion must be considered technically. This characteristic is very different from air and nitrogen gas, which are gases at normal temperatures and at temperatures as high as several hundred degrees. However, Patent Document 7 does not provide any technology that takes into account the characteristics of superheated steam.

(2) Increase in melting and scattering components in the atmosphere in the chamber As described above, this problem is also a common problem in a reflow furnace using nitrogen gas as a heating medium. Solder melting and scattering components are contained in the exhaust and discharged outside the furnace, and some of them are condensed and accumulated when they come into contact with the low temperature part in the furnace. In this respect, since the technique described in Patent Document 7 does not provide any means for suppressing or collecting the increase of the solder scattering component in the circulating medium, at the same time the concentration of waste products in the circulating atmosphere increases without limit. There is a pollution problem that wastes leak out of the furnace without limit.

(3) Problems when heating a room-temperature workpiece with superheated steam In addition to this, Patent Document 7 lacks technical measures to prevent side effects based on the characteristics of superheated steam.
In the description of Patent Document 7, if superheated steam of 150 ° C or higher is sprayed onto the workpiece at a speed of 1 meter or more per second, no dew condensation occurs on the workpiece, but when the room temperature workpiece enters the heating chamber, the temperature is sufficient. It takes time according to the heat capacity of the parts to rise. Naturally, a part having a large heat capacity requires a long heating time. During this time, superheated steam is condensed on the surface of the work and adheres as water droplets. These water droplets evaporate as the part temperature rises. As the number of reflow substrates increases, the concentration of solder melting and scattering components in the medium in the chamber increases, so that the concentration at which these components dissolve during condensation also increases. The dissolved component is chemically active as described in Patent Document 7, and it not only adheres to the substrate and parts and exerts harmful effects, but also remains on the work as a residue after water droplets re-evaporate. The residue will absorb and dissolve moisture in the air at a later date and corrode the metal part of the workpiece. This problem is a problem peculiar to superheated steam that does not occur in a reflow furnace using nitrogen gas as a heating medium.

(4) Problem at the time of workpiece | work cooling The technique of patent document 7 is not equipped with the countermeasure technique at all about the problem of the cooling of the workpiece | work after reflow. The technology of the reflow device disclosed in this document has no explanation about the mutual interference between the atmospheres of the reflow zone and the cooling zone, and since there is a common conveyor mechanism for moving the workpiece, there is a gap between both zones. The gas can be circulated through. Therefore, a part of the superheated steam in the reflow zone leaks to the cooling zone based on the property of normal temperature expansion. The leaked high-temperature superheated steam is atomized into water droplets, and can adhere to the workpiece and cause harmful effects on the substrate and components as in the preheating step. This problem is also a problem peculiar to superheated steam that was not present when nitrogen gas was used.

  The present invention has been made in order to solve the above-mentioned problems. Reflow soldering is performed with high-temperature and high-pressure heated steam, and superheated steam is collected after use to remove scattered components during melting of the solder by a simple technique. An object of the present invention is to provide a reflow apparatus using superheated steam which is low in running cost and free of pollution.

JP 7-77346 A JP 2007-160322 A JP 2008-279502 A JP 2009-99761 A JP 2009-99762 A Japanese Patent Laid-Open No. 2002-263832 JP 2008-270499 A JP 2001-235228 A

Nakao Gosuke, Hiraizumi Satoshi, and Iwasaki Atsuko "Reflow Equipment for Lead-Free", Furukawa Electric Times, No. 106, pages 25-30, July 2000

The first problem to be solved is that in a reflow apparatus using superheated steam as a medium, high-temperature and high-pressure superheated steam has a strong tendency to leak out of the heating chamber.
Further, the second problem to be solved is that in the reflow apparatus using superheated steam as a medium, the concentration of the component of molten solder scattered in the reflow apparatus rises indefinitely while the superheated steam is reused in the heating chamber. Is a point.
The third problem to be solved is that when heating a normal temperature workpiece with superheated steam, the superheated steam containing solder melting and scattering components is condensed and adhered to the workpiece surface until the workpiece is sufficiently heated. In the process where the work is contaminated and in the process of cooling the work after reflow, the superheated steam containing the solder melting and splashing component leaked from the reflow chamber becomes mist-like water droplets and adheres to the work, and the work is contaminated. Is a point.

If the reflow device does not correspond to the characteristics of the heating medium to be used, it cannot be established as a reflow device and cannot be put into practical use. There is a great difference in the characteristics of nitrogen gas and superheated steam as heating media. Nitrogen gas is chemically inert and is in the gas phase at both ambient and reflow temperatures. On the other hand, superheated steam is instantly transformed into a liquid phase (water) due to a temperature drop and exhibits water properties.
Therefore, in order to use superheated steam as a heating medium, it is necessary to cope with the phase conversion of superheated steam.
In order to use superheated steam as a reflow superheated medium, the present invention utilizes the phase change of superheated steam from the gas phase to the liquid phase to liquefy the used superheated steam, and the solder melting and scattering material contained therein It is the most important feature that it is provided with a means for removing the residue of scattered components generated by melting of the solder by collecting the water in the water droplets and preventing the dew condensation of the used superheated steam on the workpiece.

  A reflow apparatus according to the present invention is a reflow apparatus that performs reflow soldering while a workpiece, which is a board on which a component is printed by printing solder, passes through a plurality of chambers, and is heated by an electromagnetic induction heater and / or an electric heater. A reflow chamber in which a superheated steam generating means for generating steam, a water supply passage for supplying water to the superheated steam generating means, a reflow soldering means for soldering a workpiece with superheated steam, an electric heater and a fan are provided. And a lead-out path for deriving the superheated steam after use, a soldering residue that collects molten solder scattering components in the generated distilled water by bringing the water supply path and the lead-out path into close contact to perform heat exchange and distillation of the superheated steam It is characterized by comprising a recovery means, a preheating chamber in which an electric heater and a fan are disposed, and a cooling chamber for taking in outside air and cooling the work.

  The reflow method of the present invention is a reflow method for performing reflow soldering while a work, which is a board on which a component is printed by printing solder, passes through a plurality of chambers, and includes a superheated steam generation step and the superheated steam. A water supply path for supplying water to the generating means, a reflow soldering step for soldering the workpiece with superheated steam, a lead-out path for deriving superheated steam after use, and the water supply path and the lead-out path are in close contact with each other It comprises a soldering residue recovery step of exchanging and distilling superheated steam and collecting molten solder scattering components in the generated distilled water.

  The reflow apparatus using the superheated steam of the present invention as a heating medium uses a phase change of superheated steam from a gas phase to a liquid phase to remove scattered components generated by melting of the solder, and to provide a means for preventing superheated steam condensation. Since it is provided, there is an advantage that a reflow device that is pollution-free and low in running cost can be realized.

FIG. 1 is an explanatory diagram showing the overall configuration of the reflow apparatus. Example 1 FIG. 2 is a flowchart for explaining the operation steps of the reflow apparatus. Example 1 FIG. 3 is a reference diagram showing a configuration of an example of a high frequency dielectric heater. Example 1

  The purpose of non-polluting and low-running reflow soldering has been realized by collecting molten solder scattered components in the water that has phase-converted superheated steam and preventing condensation of the superheated steam.

FIG. 1 is a diagram showing the overall configuration of one embodiment of the reflow apparatus of the present invention.
After the cream solder is printed and the workpiece 6 which is a board on which the components are mounted is carried into the reflow apparatus 1 from the board carry-in entrance 23, the work 6 is transported through the reflow apparatus and reflow soldered. Unload from exit 24. In this figure, the configuration of the lower half of the apparatus is rotationally symmetric about the upper part of the transport mechanism 25 and the transport line, and therefore the detailed configuration is not shown.

  The reflow device 1 includes a first preheating zone 2, a second preheating zone 3, a reflow zone 4, and a cooling zone 5.

  In FIG. 1, the first preheating zone 2 is illustrated so as to correspond to one first preheating chamber, but more specifically, the number of chambers may be plural if necessary. In the other zones described below, the number of corresponding rooms is shown as one, but a plurality of rooms can be similarly provided according to specific use needs.

  The first preheating chamber circulates the indoor air heated by the heater 7 by the fan 8 and heats the work 6 carried in to about 100 ° C. which is the boiling point of water. The applied heater 7 may be an electric heater or another type of heater. In this preheating step, the work is preheated and heated to about the boiling point of water, so that even if the work comes into contact with superheated steam that may leak from the reflow zone 4, it does not cause condensation on the surface. ing.

  The second preheating chamber is a heating chamber corresponding to the second preheating zone 3 and circulates indoor air heated by a heater (not shown) by a fan (not shown), and is used by the user. According to the set reflow soldering temperature profile, the workpiece 6 heated in the first preheating chamber is further heated to about 150 ° C. to 170 ° C. The second preheating chamber includes a lead-out path for discharging superheated steam that may leak from the reflow chamber, details of which will be described later.

  The reflow chamber is a heating chamber corresponding to the reflow zone 4 and circulates indoor air heated by a heater (not shown) from the start of operation of the reflow device 1 by a fan (not shown), Preheat indoor atmosphere and components to a temperature required for reflow (about 230 ° to 240 °). When the room temperature rises, superheated steam is introduced to expel all the air inside, and then reflow soldering is performed.

  Superheated steam applied to reflow soldering is generated by the high frequency electromagnetic induction heater 11. First, water is taken into the high frequency electromagnetic induction heater 11 from the water supply channel inlet 9 through the water supply channel 10, and superheated steam having a reflow temperature of about 240 ° C. or more is generated by high frequency electromagnetic induction. The generated superheated steam is jetted from the superheated steam jet 13 into the reflow chamber via the superheated steam duct 12. When it is detected by an oxygen electrode (not shown) that the reflow chamber is filled with superheated steam, the workpiece 6 described above is carried in from the board carry-in port 23, and the soldering process in this reflow apparatus is started. The operation of the reflow apparatus and the work soldering step will be described in detail later. The temperature in the reflow chamber is detected by a temperature sensor (not shown) and used as a control signal for the soldering process.

  The superheated steam generated by the high-frequency electromagnetic induction heater 11 has a high temperature and a high pressure, rapidly fills the reflow room space, circulates in the room by a fan (not shown), and the injection port 14 set at the lower part of the reflow room. To the workpiece 6. The injection port 14 has a large number of small holes in a flat plate and is provided with a tubular guide to form a nozzle shape. The high-temperature superheated steam circulating in the room is injected by a fan toward the work and has a large heat capacity. The soldering of components (particularly, components (BGA) having solder joints only on the lower surface) is performed smoothly (see Non-Patent Document 1 as a reference).

In the conventional reflow apparatus using nitrogen gas, nitrogen gas is supplied to both the preheating zone and the reflow zone in order to maintain the medium at a low oxygen concentration level necessary for oxygen-free soldering, so that the nitrogen gas consumption space is large. Moreover, constant replenishment of leaking nitrogen gas was necessary. For this reason, the demand amount of nitrogen gas was large, and there existed a problem in terms of running cost.
The present invention, on the other hand, only needs to supply superheated steam only to the reflow zone, so that water consumption is small and the heating cost is lower.
The supply of the heating medium only in the reflow zone is due to the characteristics of superheated steam. The high-temperature superheated steam of 240 ° or more just generated by the high-frequency electromagnetic induction heater 11 has a volume of 22.4 liters corresponding to 1 mol (18 grams) of water, and becomes about 260 liters in terms of atmospheric pressure according to the gas equation. This means that when the high-temperature and high-pressure superheated steam is brought into contact with the normal pressure environment, the volume is constantly expanded until the temperature drops to room temperature.
That is, the superheated steam in the reflow chamber is ejected from the lower flat jet port 14 toward the transport mechanism unit 25 having a lower atmospheric pressure, and bathed as a jet stream toward the work 6. Further, because of this property, as long as the superheated steam is continuously supplied to the reflow chamber, air is expelled from the room and the room is maintained in an oxygen-free state, so that oxygen-free soldering is established.

Here, the high frequency electromagnetic induction heater 11 used in this embodiment will be described.
In general, various types of high-frequency electromagnetic induction heater technologies are implemented, but in this embodiment, one of them is used. The configuration is shown in FIG. 3 as a reference diagram. FIG. 3 is cited from Patent Document 8.
In FIG. 3, when a fluid is passed through the heat generating bent tube 10 made of a conductive material and a high-frequency current is passed through the coil 14, a magnetic field is generated inside the coil by the magnetic flux, and an eddy current is generated in the heat generating bent tube 10, which is unique. Joule heat is generated due to the resistance, and heat is transferred to the fluid flowing in the pipe to heat the fluid.

  Although the high-frequency electromagnetic induction heater 11 of this embodiment in FIG. 1 is illustrated to generate superheated steam from water in one unit, the unit that generates water vapor by heating water and the water vapor are heated. You may connect the unit which produces | generates superheated steam. Alternatively, it is also possible to use an electric heater in the step of generating water vapor from water and use another electric heater or a high-frequency electromagnetic induction heater in the step of using the generated water vapor as superheated water vapor. It goes without saying that the advantage of the reflow device utilizing superheated steam characteristics in the present invention can be obtained by using any production method.

  The used superheated steam sprayed on the workpiece 6 is sucked by the fan 15 from the used superheated steam suction port 16 and introduced into the soldered residue collecting device 18 through the used superheated steam lead-out path 17. In this way, the reflow chamber is always filled with fresh superheated steam, and the used gas is immediately discharged. Further, the superheated steam leaked from the reflow zone 4 into the reflow device is also introduced into the soldering residue collecting device 18 through the post-use superheated steam outlet passage 17.

The soldering residue collecting device 18 is a heat exchange type distillation device, and cools and distills the superheated steam after use with normal temperature water supplied from the water supply channel inlet 9. After use, the superheated steam is cooled to at least 70 ° C. or less and phase-converted to become water. This water adsorbs or dissolves flux components, fume components and fine solder particles scattered by melting the solder, and collects the molten solder residue. Since the volume of water produced is much smaller than gaseous superheated steam, it is also very convenient for disposal or regeneration. The waste water is discharged from the drain port 10.
On the other hand, the heat energy of the heated steam is transferred to water by this heat exchange, and the water supplied to the high-frequency electromagnetic induction heater 11 is heated, which contributes to the saving of the heating power cost of the high-frequency electromagnetic induction heater 11.

  An inverted T-shaped partition 20 is provided at the lower end of the reflow chamber and the second preheating chamber. A partition 20 is also provided at the lower end of the cooling chamber near the reflow chamber. These are partitions for minimizing leakage of superheated steam, and a small amount of leaked superheated steam is still collected in the superheated steam outlet 17 after use.

  The reflowed work 6 is air-cooled in the cooling chamber of the cooling zone 5 and then carried out from the substrate carry-out port 24. Outside air is introduced into the cooling chamber from the outside air inlet 21, the work 6 is cooled while being circulated by a fan (not shown), and is exhausted out of the apparatus through the exhaust port 22. This air cooling has an effect of preventing the entry of superheated steam that may leak out of the reflow zone into the cooling chamber.

Next, operation steps of this embodiment will be described with reference to FIG.
First, the power source of the reflow device is turned on (ST1), and the heaters and fans in the first preheating chamber, the second preheating chamber, and the reflow chamber are started (ST2). The room temperature of the first preheating chamber is about 100 ° C, the room temperature of the second preheating chamber is a user set temperature of about 150 ° to 170 °, and the room temperature of the reflow chamber is about 230 ° C to 240 ° C. When the user set temperature is reached (ST3), water supply to the electromagnetic induction heater is started (ST4), and the generated superheated steam is supplied to the reflow chamber (ST5).

  The superheated steam is filled in the reflow chamber by the signal of the oxygen electrode installed in the reflow chamber (ST6), and when the set reflow temperature is reached, the work is carried into the reflow apparatus (ST7). After the workpiece is heated to about 100 ° C. in the first preheating chamber (ST8), it is heated to the preheating temperature set in the second preheating chamber (ST9). Thereafter, the work is advanced to the reflow chamber, and reflow solder melting is performed by injection of superheated steam (ST10). The workpiece is heated according to a temperature profile set by the user. Finally, the work is air-air cooled in the cooling chamber (S12) and carried out of the reflow device (ST13).

  The post-use superheated steam sprayed toward the workpiece in the reflow chamber is introduced into the solder residue collecting device, and scattered components are collected and removed by heat exchange with the supply water (S11).

  By performing reflow soldering with only the reflow chamber at the reflow temperature, the volume of the heating medium to be used can be minimized and the cost can be reduced, and pollution measures to collect solder melting and scattering components by using the heating medium as the liquid phase by heat exchange It can also be applied to applications.

DESCRIPTION OF SYMBOLS 1 Reflow apparatus 2 1st preheating zone 3 2nd preheating zone 4 Reflow zone 11 High frequency electromagnetic induction heater 18 Soldering residue collection apparatus

Claims (2)

A reflow apparatus that performs reflow soldering while a workpiece, which is a substrate on which a component is printed by printing solder, passes through a plurality of chambers,
Superheated steam generating means for generating superheated steam by an electromagnetic induction heater and / or an electric heater;
A water supply channel for supplying water to the superheated steam generating means;
Reflow soldering means for soldering the workpiece with superheated steam;
A reflow chamber in which an electric heater and a fan are disposed;
A lead-out path for deriving superheated steam after use;
Soldering residue collection means for collecting the molten solder scattering component in the produced distilled water by performing heat exchange and distillation of superheated steam by bringing the water supply channel and the outlet channel into close contact with each other,
A preheating chamber in which an electric heater and a fan are disposed;
A reflow apparatus comprising a cooling chamber that takes in outside air and air-cools a workpiece. A reflow method for performing reflow soldering while a workpiece, which is a substrate on which a component is printed by printing solder, passes through a plurality of chambers,
A superheated steam generation step;
A water supply channel for supplying water to the superheated steam generating means;
A reflow soldering step for soldering the workpiece with superheated steam;
A lead-out path for deriving superheated steam after use;
A reflow method comprising: a soldering residue recovery step of bringing the molten water splash component into the produced distilled water by closely exchanging heat supply steam and superheated steam by bringing the water supply channel and the outlet channel into close contact with each other.

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