WO2005068123A1

WO2005068123A1 - Reflow furnace

Info

Publication number: WO2005068123A1
Application number: PCT/JP2005/000004
Authority: WO
Inventors: Issaku Sato
Original assignee: Senju Metal Industry Co., Ltd.
Priority date: 2004-01-16
Filing date: 2005-01-05
Publication date: 2005-07-28
Also published as: JPWO2005068123A1; TW200526100A; JP4665763B2

Abstract

[PROBLEMS] In a conventional reflow furnace in which flux fume produced in the furnace is led to the outside for purification, the flux fume is not sufficiently removed, and the flux fume remains in an inert gas circulated in the furnace. As a consequence, in such a conventional reflow furnace, flux fume tends to adhere to a furnace wall, and the adhered flux fume sometimes drops to soil a printed circuit board. [MEANS FOR SOLVING PROBLEMS] In a reflow furnace of the invention, flux fume produced in the furnace is led to the outside, and almost the entire flux fume is removed at a filter section as a removing device. In the filter section is installed a paper block-like filter having a large number of long holes, and the long holes are oriented in the direction of flow of the flux fume.

Description

Reflow furnace

Technical field

The present invention relates to a reflow furnace for soldering a printed board and a surface mount component with a solder paste.

Background art

[0002] Solder paste used for soldering in a reflow furnace is a viscous soldering material composed of powder solder and paste-like flux. When soldering a printed circuit board and a surface mounted device (SMD) using this solder paste, a metal mask with holes drilled in the same place as the soldered part of the printed circuit board is used. After placing the solder paste on the printed circuit board so that the soldered parts match, place the solder paste on the metal mask, apply the solder paste with a squeegee, and fill the holes in the metal mask with the solder paste. I do. Then, when the metal mask is moved upward on the printed circuit board, the solder paste is printed on the soldered portion of the printed circuit board. After that, a predetermined SMD is mounted on the application part of the printed circuit board, and the printed circuit board is transferred into the reflow furnace by a transfer device of the reflow furnace, and soldering is performed.

[0003] A reflow furnace for soldering a printed circuit board includes a preheating zone, a main heating zone, and a cooling zone in order from the entrance to the exit, and the conveying device travels along these zones. ing. The printed circuit board passes through the preheating zone, the main heating zone, and the cooling zone while being transported by the transport device, and is subjected to soldering.

[0004] In the preheating zone of the reflow oven, the solvent contained in the solder paste is evaporated by heating the printed circuit board to 100 to 150 ° C, and the solvent is heated by the high-temperature heating in the main heating zone in the next process. To prevent bumping! In addition, the printed board or SMD can be alleviated against heat shock caused by high-temperature heating, and the activation of the flux can be activated. Remove things and dirt to clean

[0005] In this heating zone, the temperature is equal to or higher than the melting temperature of the powder solder in the solder paste. Then, the solder paste powder solder applied to the printed circuit board is melted, and the solder spreads between the soldered part of the printed board and the SMD electrode.

[0006] The cooling zone blows cold air to the printed circuit board heated to a high temperature in the main heating zone to solidify the molten solder so that the soldered portion does not collapse due to vibration or impact. Cools quickly to eliminate thermal effects

[0007] By the way, an activator is an essential component in the solder paste flux. The activator has a function of reducing and removing the oxide to clean even if the soldered portion of the printed circuit board or the SMD electrode is heated at a high temperature and oxidized during soldering. The higher the caloric content, the better the solderability and the less defects. However, when soldering with solder paste containing a large amount of activator, after soldering, the flux residue adhering to the soldered part absorbs moisture and becomes an electrolyte, corroding the soldered part and lowering the insulation resistance. . For this reason, printed circuit boards used for communication equipment and computers that require reliability have been washed and removed of flux residues after soldering using solder paste. Cleaning fluids such as trichlene, alcohol, etc. were used to clean this flux residue. These cleaning fluids may cause damage to the ozone layer surrounding the earth and cause global warming. Therefore, use is regulated. Therefore, a solder paste which does not need to be cleaned after soldering, that is, a non-cleaned solder paste has been used at present. This non-cleaning solder paste does not cause problems such as corrosion and a decrease in insulation resistance without cleaning because the amount of the active agent added is small and the flux residue after soldering is very small.

[0008] Since the non-cleaning solder paste has a small amount of added activator, when soldering is performed in an atmospheric reflow oven where oxygen is present, oxides of the soldered portion that have been oxidized during heating are completely returned. Cannot be removed. Therefore, the non-cleaning solder paste cannot sufficiently reduce the oxidized powder solder that can be removed by force if soldering failure occurs, and generates fine solder balls. If soldering is performed in a reflow furnace in an inert atmosphere without oxygen even in a non-cleaning solder paste while applying force, the soldered portion will not be oxidized during heating, resulting in poor soldering and small solder balls. Soldering without generation is possible. Follow Recently, the inert atmosphere reflow furnace has been widely used in the electronic equipment industry.

[0009] In an inert atmosphere reflow furnace, it is effective to reduce the oxygen concentration in the furnace as much as possible to prevent defective soldering. Therefore, in an inert atmosphere reflow furnace, a device such as a labyrinth is devised at the entrance and exit to prevent air from entering from outside, and the disturbance of hot air inside the furnace is suppressed to prevent air from entering from outside. RU

[0010] Generally, in an inert atmosphere reflow furnace, an inert gas flows into a furnace from a gas cylinder or an inert gas generator installed outside, but a new inert gas always flows in the furnace. In this case, the running cost increases due to the large consumption of the inert gas. Therefore, the inert gas in the furnace is purified and reused. Purification of the inert gas is to remove solvent vapor and flux fume generated from the solder paste during soldering.

[0011] That is, when the solder paste is heated in the reflow furnace, the solvent in the solder paste evaporates in the preheating zone, and the flux is heated to a high temperature in the main heating zone, so that the flux is decomposed into flux fume. When the evaporated solvent or flux fume (hereinafter referred to as flux fume) adheres to the components in the reflow furnace, it condenses there and further solidifies. When flux 'fume which solidifies for a long time accumulates, it falls onto the printed circuit board during soldering,

Dirty SMD or hinders smooth running of transport equipment. Therefore, a number of reflow furnaces equipped with a flux and fume removing device have been proposed. (Reference: Patent Documents 1-8)

Patent Document 1: JP-A 1-305594

Patent Document 2: JP-A No. 4-13474

Patent Document 3: JP-A-4-46667

Patent Document 4: JP-A-4-251661

Patent Document 5: JP-A-5-50218

Patent Document 6: JP-A-9-307224

Patent Document 7: JP-A-10-335807 Patent Document 8: Japanese Utility Model Publication No. 5-93079

Disclosure of the invention

Problems to be solved by the invention

[0012] However, in a conventional reflow furnace equipped with a flux / fume removing device, it is difficult to completely remove the flux / fume, and the gas that has passed through the flux / fume removing device is recirculated to the pipe through which the gas flows to the reflow furnace. The flux or fume concentration in the gas recirculated to the reflow furnace may adhere to the furnace wall or cooling zone of the reflow furnace. An object of the present invention is to provide a reflow furnace capable of efficiently removing flux 'fumes from the gas force inside the furnace led out of the furnace.

Means for solving the problem

[0013] The present inventors have found that flux 'fume is liquid at the time of dew condensation, paper absorbs and cleans liquid, and flux' fume adheres to the wall surface of the slot when passing through the slot. The present invention has been completed by focusing on the easiness of the method.

[0014] The present invention relates to a flux and a fume removal apparatus for extracting a flux 'fume generated in a reflow furnace together with an inert gas to a pipe outside the reflow furnace and installing the flux' fume removal apparatus outside the reflow furnace. In a reflow furnace for returning inert gas to the reflow furnace again, a block filter made of paper having a large number of long holes is formed in a part of the filter of the removing device. A reflow furnace characterized by being installed so as to face the flow direction.

The invention's effect

[0015] In the reflow furnace of the present invention, since the gas in the furnace passes through many long holes, the flux fume is cooled while the gas passes through the long holes, and the flux fume is condensed and adheres to the long holes. Flatus fumes are liquid when condensed, but the filter is made of V or paper, which easily penetrates the liquid, so the liquid flux fume instantly soaks into the paper filter. Therefore, most of the flux-fume-containing gas that has passed through the removal device is removed by the filter. As for the paper filter, the liquid flux Fume fumes continuously permeate, so that the permeation effect lasts for a long time. However However, even a paper filter has a limit on the amount of suction, and the state of permeation deteriorates. At that time, it is very easy to change the filter just by replacing it with a new filter. Paper filters can be incinerated, and the substances that have permeated the replaced used filters are pine resin, thixotropic agents, solvents, etc. in the flux, so there is no pollution problem when incinerated. . Therefore, the post-processing of the used paper filter becomes very easy.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] In the filter used in the present invention, the elongated hole is directed in the gas flow direction.

A slot is oriented in the direction of gas flow when the slot is inclined or bent so that it can easily flow from the inlet to the outlet. It is parallel or zigzag. When the long hole is formed in a zigzag shape, the length of the long hole becomes longer, so that the flux fume is more easily attached.

[0017] The block-shaped filter may be divided into a plurality of pieces in the long hole direction and stacked. When filters are stacked, the position of the long hole shifts in the stacking part, so that the gas flow velocity changes abruptly at that part, and the flux and fume tend to adhere to the part where the gas flow velocity changes suddenly, and the flux · The fume removal rate is improved.

Example

Hereinafter, the present invention will be described with reference to the drawings. 1 is a front cross-sectional view of the reflow furnace of the present invention, FIG. 2 is a plan view illustrating a suction portion of the flux fume in the reflow furnace, FIG. 3 is a cross-sectional view taken along line A--A of FIG. 2, and FIG. FIG. 5 is a front sectional view of the filter, FIG. 6 is a plan view of a filter used in the present invention, FIG. 7 is a plan view of another filter used in the present invention, FIG. 8 is a front sectional view of a filter used in the present invention, and FIG. 9 is a front sectional view of another filter used in the present invention.

[0019] In the reflow furnace 1, a tunnel 2 is formed in the longitudinal direction. In the tunnel, a preheating zone 5, a main heating zone 6, and a cooling zone 7 are sequentially formed with the inlet 3 side force and the outlet 4 side force. I'm in love. Hot air blowout type heaters 8 are installed in the upper and lower portions of the preheating zone 5 and the main heating zone 6, and coolers 9 and 9 are installed in the upper and lower portions of the cooling zone 7.

[0020] In the tunnel 2, a pair of conveyors 10, 10 travels from the entrance 3 to the exit 4. ing. The conveyor 10 runs on rails 11. A large number of pins 12 project from the pair of transport conveyors 10 in opposite directions, and a printed circuit board P is placed on the pins and transported in the tunnel 2.

An inert gas supply port 13... Is provided in the hot air blowout type heater 8 and an appropriate portion of the cooler 9, and the inert gas supply port is connected to an inert gas supply source (not shown) outside the reflow furnace. For example, it is connected to a nitrogen gas cylinder or a nitrogen gas tank.

[0022] A square suction pipe 14 is attached along the rail 11 of the conveyor! / The suction pipe has a plurality of suction ports 15 formed on the inside, that is, on the side of the printed circuit board to be conveyed. Outlet pipes 16 and 16 are connected to both ends of the suction pipe 14, and the outlet pipes are connected to a removing device 17 that removes the flux fume.

The flux / fume removing device 17 is composed of a filter part 18 and an aggregating part 19, and the filter part 18 and the aggregating part 19 are connected by a removing nove 20. The filter part 18 has a filter placed inside, and absorbs and removes most of the flux 'fume sucked from the suction pipe 14 by the filter. The aggregating section 19 is provided with a blower (not shown) and water-cooled fins inside. The blower sucks the gas through the suction pipe 14, the outlet pipe 16, the filter part 18, and the removal pipe 20, and contacts the flux fume that cannot be adsorbed and removed by the filter part 18 to the water-cooled fins. Here, they are collected by aggregation and adhesion.

[0024] The filter part 18 has a box shape, and a door 21 that can be opened and closed is installed on the front surface thereof. The above-mentioned lead pipe 16 is connected to the upper part of the filter part 18, and the removal pipe 20 is connected to the lower part of the lateral surface. Inside the filter part 18, a cradle 22 having a shelf on the lower side is erected, and three paper block filters 23 are stacked and mounted on the cradle. !

As shown in FIGS. 6-9, a number of long holes 24 through which gas can pass are penetrated inside the block-shaped filter 23. The long hole 24 is open in the direction of gas flow, that is, in the direction of the removal pipe 20 from the outlet nove 16 through which gas flows when stored in the filter part 18. The shape of the long hole is not limited, but is, for example, a corrugated shape, a cylinder, a honeycomb, or the like. Figure 6 shows corrugated paper 25 sandwiched between many papers. The formed elongated hole 24 is inserted from the upper part to the lower part. Fig. 7 shows the paper formed continuously with a cylindrical paper cylinder 26, and the slot 24 is also inserted from the upper part to the lower part.

The long holes 24 of the block-shaped filter 23 are parallel to the gas flow direction as shown in FIG. 8, or zigzag in the gas flow direction as shown in FIG. And so on.

[0027] Outflow pipes 27, 27 are connected to the outlet of the aggregating section 19, and the outflow pipes are connected to blowout nozzles 28, which are installed at the upper and lower portions of the inlet 3 and the outlet 4 of the tunnel 2. Been!

Here, an operation state of the reflow furnace having the above structure will be described. The printed circuit board P is placed on the conveyor 10 from the entrance 3 and is carried into the tunnel 2. The printed circuit board P is heated by the hot air blowout type heater 8 in the pre-heating zone 5, where the solvent in the solder paste is evaporated, and pre-heating is performed to protect the printed circuit board and electronic components from heat shock. . The solvent evaporated here is sucked into the suction port 15 opened near the conveyor 10 as shown by arrows in FIGS.

[0029] The printed circuit board P preheated in the preheating zone 5 is then conveyed to the main heating zone 6, where it is heated to a high temperature to melt the powder solder in the solder paste and wet the soldered portion. spread. At this time, rosin, activator, thixotropic agent and the like in the solder paste become flux 'fumes, and the flux' fumes are also sucked into the suction port 15 opened near the conveyor 10.

The vaporized solvent or flux fume sucked into the suction port 15 also enters the filter part 18 of the removing device through the outlet pipe 16 and the suction pipe 14. Since the block-shaped filter 23 accommodated in the filter part 18 has a large number of long holes 24, the flux 'fume passes through these many long holes. In the process of passing through the elongated hole, the flux fume is cooled on the wall surface of the elongated hole 24 and forms dew condensation, and adheres to the wall surface. At this time, since the block filter is made of paper, dew condensation on the wall surface of the long hole instantly permeates the wall surface of the long hole. In this way, the flux fume that passes through the long hole of the block filter is condensed one after another and is removed by seeping into the block filter. It is. Filters with a large amount of flux fumes are removed from a part of the filter and discarded or incinerated.

[0031] The flux / fume that could not be completely removed by a part of the filter is transferred to the aggregation section 19 by the removal pipe 20, where it contacts the water-cooled fins, aggregates, and is completely removed. In the agglomeration section, the flux 'fume adhering to the water-cooled fins is collected in the lower container and disposed as waste. The inert gas from which the flux / fume has been almost removed by the removal device is returned to the reflow furnace 1 from the outflow pipe 27.

Brief Description of Drawings

FIG. 1 is a front sectional view of the reflow furnace of the present invention.

[Figure 2] Plan view for explaining the suction part of the flux 'fume in the reflow furnace

[Figure 3] A-A sectional view of Figure 2

[Figure 4] Partial cross-sectional view of a part of the filter in the flux and fume removing device

[Figure 5] Front sectional view of a part of the filter in the flux and fume removing device

FIG. 6 is a plan view of a filter used in the present invention.

FIG. 7 is a plan view of another filter used in the present invention.

FIG. 8 is a front sectional view of a filter used in the present invention.

FIG. 9 is a front sectional view of another filter used in the present invention.

Explanation of symbols

[0033] 1 reflow furnace

16 Derivation pipe

17 Removal device

18 Fino letter section

19 Agglomeration part

23 Huino Letter

24 Slot

Industrial applicability

[0034] The reflow furnace of the present invention can be applied to any heater such as a far-infrared irradiation type and a laser-irradiation type in addition to a hot air blowing type heater.

Claims

The scope of the claims

[1] Flux generated in the reflow furnace is discharged to the outside of the reflow furnace together with inert gas by a nove, and flux and fume removal equipment installed outside the reflow furnace removes flux and fumes. In the reflow furnace for returning the inert gas to the inside of the reflow furnace again, a paper block filter having a large number of long holes is formed in a part of the filter of the removing device in the flow direction of the flux fume through the long holes. A reflow furnace characterized by being installed as described above.

2. The reflow furnace according to claim 1, wherein the filter has an elongated hole parallel to a flowing direction of gas.

3. The reflow furnace according to claim 1, wherein the filter has an elongated hole formed in a zigzag shape in a gas flow direction.

[4] The reflow furnace according to claim 1, wherein the filter is divided into a plurality of pieces in a long hole direction.

1/6

Replacement forms (Rule 26)

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9 / ε

[S side

1-00000 / S00Zdf / 13d ε 890 / S00Z OAV

9 / 5/6

WO 2005/068123 PCT / JP2005 / 000004