JPH03221783A - Method and apparatus for preventing entrance of air into environment at rotational axis insertion part - Google Patents

Abstract

PURPOSE:To prevent air from being entered into the environment by forming a hole in a partition wall for blocking the atmosphere and the environment and constructing the surroundings of a hole on the atmosphere side to be the same as that of the environment, and further inserting a rotational shaft from the hole into the environment for rotation. CONSTITUTION:A gas supply pipe 7, 7 is disposed in a heating region 4 and a cooling region 5 of a N2 reflow furnace 1 through a furnace wall 6, and a fan 8 is disposed in the heating region 4 and the cooling region 5, and further a gas inflow inlet 16 is formed in the side surface of a cavity 13. N2 is fed from a gas bomb to the gas supply pipe 7 to force N2 into the furnace as well as force N2 into the cavity 13. Further, a rotational shaft 10 is rotated by a motor 11, the gas flows into the furnace from the hole 9 in the furnace wall 6 following the rotation, but since the cavity in the hole is filled with N2, N2 freed from a hole plate 15 flows from the hole in the furnace wall into the furnace. Thus, air is prevented from entering the furnace.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device in which a rotating shaft is inserted through a partition wall that separates the atmosphere from the atmosphere, for example, reflow soldering is performed while stirring an inert gas inside the furnace from outside the furnace. The present invention relates to a method and apparatus for preventing air from entering the atmosphere from the rotary shaft insertion portion in a rotary shaft insertion portion.

[Prior art] Reflow soldering is a method in which cream solder is applied to a printed circuit board and soldered by heating and melting it in a tunnel-type glue flow furnace. Much has been done to maintain the atmosphere. To create an N2 atmosphere inside the reflow oven, supply N2 directly into the reflow oven and rI! This allows N2 to flow out from the inlet and outlet of the furnace. Even if the entrance and exit of the furnace is open, if N2 is supplied into the furnace, air is difficult to enter the furnace through the entrance and exit, and the N2 atmosphere inside the furnace can be maintained.

Even if this NZ is used or a flow furnace (hereinafter referred to as +N2 reflow furnace) uses a weakly active flux.

Because soldering can be done cleanly, one of today's countermeasures against CFCs is that soldering can be done without cleaning the flux residue after soldering, and sometimes soldering can be done without cleaning the flux residue after soldering because the carbonization of the flux is small. It has the advantage of being easy to clean even when cleaning.

N1) In a flow furnace, it is possible to make the temperature distribution inside the furnace more uniform by flowing N2 inside the furnace rather than simply keeping the inside of the furnace in an N2 atmosphere, so the printed circuit board is heated evenly, Accidents such as soldering defects due to insufficient heating and heat damage to electronic components due to local heating are eliminated. Therefore, in an N2 reflow furnace, a fan for flowing N2 is installed inside the furnace, and the fan is rotated by a motor outside the furnace. A hole is made in the furnace wall for the fan inside the furnace and the motor outside the furnace.

They are interlocked by a rotating shaft inserted through the hole.

[L that the invention tries to solve! a] However, in conventional N2 reflow ovens, no matter how much N2 is supplied, oxygen gets mixed into the furnace and the oxygen concentration increases, making it impossible to take full advantage of the features of the N2 reflow oven.

[Means for Solving the Problems] The present inventors investigated the cause of filtration element contamination in N2 reflow ovens, and found that in order to flow N2 in the furnace with a fan, the furnace was A hole 9 in the furnace wall 6 into which the rotating shaft IO connected to the motor 11 installed outside is inserted.
It was found that air gets caught up in the rotation of the rotating shaft and enters the furnace. In other words, the hole in the rotating shaft insertion part is larger than the shaft diameter so that the shaft can be easily inserted.
If the motor is simply placed over a hole, air will enter through the hole.

Therefore, the inventors of the present invention focused on the fact that if the material that is drawn into the hole into which the rotary shaft is inserted as the shaft rotates is not air but the same gas as inside the furnace, the oxygen 1J11 degree inside the furnace will not be lowered. The present invention was completed.

In the present invention, the atmosphere is separated from the atmosphere by a partition wall, a hole is bored in the partition wall, and the surroundings of the hole on the atmosphere side of the FM wall are kept in the same atmosphere as the above-mentioned atmosphere.

The rotary shaft is inserted into the atmosphere through the hole and rotated. A hollow body serving as an ax hole is installed in the rotary shaft insertion part into the atmosphere, and the rotary shaft is inserted through the hole of the hollow body and the hole F[. This is an air intrusion prevention device in a rotating shaft insertion portion into the atmosphere, characterized in that the rotating shaft is inserted into the atmosphere, and a gas inlet is formed in the hollow body.

[Example] The present invention will be explained below based on the drawings.

Figure 1 is a central cross-sectional view of an N2 reflow oven employing the present invention,'! Figure s2 is an enlarged sectional view of the main part.

The N2 reflow furnace 1 is of a tunnel type, and a conveyor 2 (not shown) for transporting a printed circuit board runs inside the tunnel. There are multiple heaters 3 at the top and bottom of the conveyor.
... is installed, but the part where the heater is installed in the tunnel is the heating area 4 that heats the printed circuit board,
The part where the heater is not installed serves as a cooling area 6 for cooling the printed circuit board after soldering. Gas supply pipes 7, 7 are installed in the heating zone 4 and the cooling zone 5 through the furnace u6, from which N2 is supplied into the furnace. In addition, a fan 8 is installed in the heating area 4 to stir the N2 in the heating area to make it a uniform temperature, and in the cooling area 5, a fan 8 is installed to cool the printed circuit board after soldering. is installed. The fan is rotated by a motor 11 outside the furnace by means of a rotary shaft 10 inserted from outside the furnace through a hole 9 drilled in the furnace u, 6.

The door 1 is connected to the motor through the air intrusion prevention device 12. It is attached to 16. The air infiltration prevention device has two bodies: a hollow body 13;
Flanges 14 for attaching the air intrusion prevention device to the motor 1 and the oven wall 6 of the reflow oven are formed on the upper and lower outer sides of the hollow body. Furthermore, large plates 15, 15 having holes of approximately the same diameter as the rotating shaft are installed inside the upper and lower parts of the hollow body 13. A flat bearing is suitable for the large plate 15, which protects the rotating shaft to a certain extent and allows the rotating shaft to rotate smoothly without wobbling. A gas inlet 16 is formed on the side surface of the hollow body 13, and the inlet is connected to the gas supply pipe 7 described above. A gasket 17 is installed between the hollow body 13 and the furnace u6, and the attachment makes the part and the outside airtight.Next, the operating state of the N2 reflow furnace employing the present invention will be described.

First, N2 is sent from two gas cylinders (not shown) to the zero body supply pipe 7 to flow into the furnace and also into the hollow body 13. Then, the motor 11 rotates the rotating shaft 1.
0 is rotated, the gas is caught in the rotation of the rotating shaft and flows into the furnace through the hole 9 in the furnace wall 6, but since the hollow body above the hole is filled with N2, the large plate The N2 extracted from No. 15 flows into the furnace through the hole in the furnace wall. Therefore, no air enters the furnace.

Conventional N2 in which the inventors installed the motor directly on the furnace wall
When we measured the oxygen concentration in a reflow oven and an N2 reflow oven that adopted the present invention, we found that in the conventional type, the oxygen concentration in the oven was 11,000PP, but in the N2 reflow oven that adopted the present invention, it was less than 1.00PPM. This was an extraordinary number.

[Effects of the Invention] According to the present invention, when a rotary shaft is inserted into the atmosphere from the outside, air is not mixed into the atmosphere from the two-rotation shaft insertion portion, so that the purity of the atmosphere can be improved. Therefore, in a +N2 reflow oven, a less active flux can be used, making it possible to do without cleaning, and soldering is difficult to carbonize after soldering, so even if the flux residue needs to be cleaned, it is easy to do. It is possible to achieve excellent effects that have not been seen before.

[Brief explanation of drawings]

FIG. 1 is a central cross-sectional view of an N2 reflow oven employing the present invention, FIG. 2 is an enlarged cross-sectional view of a main part, and FIG. 3 is an enlarged cross-sectional view of a conventional rotating shaft mounting section. 6... Furnace wall 9... Hole lO... Rotating shaft 11.
...Motor 12...Aerial trespass prevention device 13...
Hollow body 5...Large plate 6...Gas inlet

Claims (3)

[Claims] (1) Separate the atmosphere from the atmosphere with a partition wall, drill a hole in the partition wall, create the same atmosphere around the hole on the atmospheric side of the partition wall, and insert the rotating shaft into the atmosphere through the hole. A method for preventing air intrusion at a rotating shaft insertion part into an atmosphere, characterized by inserting the rotating shaft into the atmosphere and rotating the shaft. (2) Install a hollow body with holes at both ends that are approximately the same diameter as the shaft in the partition wall on the atmospheric side that has a hole for inserting the rotating shaft, and insert the rotating shaft into the atmosphere through the hole in the hollow body and the hole in the partition wall. An air intrusion prevention device in a rotary shaft insertion portion into an atmosphere, characterized in that the hollow body is inserted into the atmosphere and a gas inflow port is formed in the hollow body. (3) An air intrusion prevention device in a rotating shaft insertion portion into an atmosphere as set forth in claim (2), wherein the hole in the hollow body is a flat bearing.