JPH0442055Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Field of industrial application) The present invention is a vapor phase soldering device that performs reflow soldering using the latent heat of vaporization of the saturated vapor phase (hereinafter simply referred to as vapor). It is related to.

(Prior Art) As shown in Japanese Unexamined Patent Publication No. 62-130770, a liquid tank is provided at the bottom of a steam tank, and a workpiece loading port and a workpiece loading port are provided across the liquid tank. , a gas phase in which the inert liquid contained in the liquid tank is heated by a heater to form vapor inside the vapor tank, and the workpieces conveyed in this vapor are reflow soldered by the latent heat of vaporization of the vapor. Type soldering devices are known.

In such vapor phase soldering, the displacement of the inert liquid contained in the liquid tank is monitored by utilizing the fact that the light transmittance changes depending on the presence or absence of the inert liquid. It is conceivable to detect the fluctuation in position using a multi-stage photo sensor.

(Problem to be solved by the invention) However, such a photo sensor has a limited heat resistance temperature and cannot be used near an inert liquid heated to a high temperature of 200°C or higher. However, due to the performance of the photo sensor, it is not possible to use it at a sufficient distance from the inert liquid.

An object of the present invention is to enable a photo sensor, which is excellent as a means for detecting fluctuations in liquid level, to be used for detecting the liquid level of a high-temperature inert liquid.

[Structure of the idea]

(Means for Solving the Problems) In the present invention, a liquid tank section 12 is provided at the lower part of a steam tank 11, and an inert liquid 1 is stored in the liquid tank section 12.
3 is heated by the heater 22 to form a saturated vapor phase 142 inside the steam tank 11, and the workpiece W conveyed in this saturated vapor phase 142 is flow soldered by the latent heat of vaporization of the saturated vapor phase. In the type soldering apparatus, a large-diameter heat dissipating cylinder 63 is communicated with the bottom of the liquid tank 12 via a pipe 62, and a heat-resistant transparent pipe 64 is vertically installed through the heat dissipating cylinder 63. This is a vapor phase soldering device in which photo sensors 65, 66, 67, and 68 for detecting the liquid level in the liquid tank section 12 are provided in multiple stages with the transparent pipe 64 in between.

(Function) In the present invention, since the liquid level in the liquid tank section 12 appears as it is inside the transparent pipe 64 via the tube 62 and the heat dissipation cylinder 63, the liquid level fluctuation in the transparent pipe 64 is detected by a multi-stage photo sensor 65. ,66,67,
By detecting by 68, the liquid tank section 12
Monitor the liquid level inside. At this time, the inert liquid 13 in the liquid tank 12 is in a high temperature state where it boils due to the heating of the heater 22 to be used for reflow soldering, but the heat contained in the inert liquid is dissipated through a large diameter heat dissipation device. Heat is radiated by the cylinder 63, and the temperature of the inert liquid inside the transparent pipe has dropped to a level that does not interfere with the normal operation of the photo sensor.

(Examples) Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

As shown in FIG. 1, an inner tank 12 as a liquid tank is formed at the bottom of the steam tank 11.
An inert liquid 13 is contained inside the container 2 . This inert liquid 13 is a fluorinated inert solvent (trade name: Fluorinert) with a boiling point of 215°C. Further, the steam tank 11 is provided with a workpiece inlet 14 and a workpiece outlet 15 with the inner tank 12 in between. An inert liquid 1 is contained inside the workpiece loading port 14.
Cooling coils 16 are disposed above and below the work conveyor 17 to condense the saturated vapor phase (hereinafter simply referred to as vapor) evaporated from the workpiece 3 and the mist floating around it and prevent it from leaking from the workpiece loading port. Cooling coils 18 are also provided inside the workpiece transfer port 15 above and below the workpiece conveyor 17 to condense vapor and mist and prevent them from leaking from the workpiece transfer port.

An outer tank 21 is arranged outside the inner tank 12,
A heater 22 is provided inside the outer tank 21, and at least a heat transfer medium 23 that becomes molten when heated by the heater 22 is filled. This heat transfer medium 23 is for uniformly heating the inert liquid 13, and suitable materials include glycerin and solder.

Furthermore, a vertical partition plate 31 is provided inside the inner tank 12 and is movable along a left-right movement guide means (not shown). It is divided into a section 32 and a secondary tank section 33 on the workpiece delivery side, and a liquid passage gap 34 is provided between the primary tank section 32 and the secondary tank section 33. Vertical partition plate 31
A female threaded member 35 is integrally attached to the holder, and this female threaded member 35 is screwed onto a threaded rod 36, and this threaded rod 36 is rotated by a motor 39 via a bevel gear 37 and a rotating shaft 38. Therefore, when the threaded rod 36 is rotated by this motor 39,
The vertical partition plate 31 is moved to the workpiece loading side or the workpiece loading side, and the primary tank section 32 and the secondary tank section 33
The area ratio between the two is variably adjusted.

In addition, a steam rising plate 4 is provided at the upper part of the work loading side and the upper part of the workpiece unloading side of the inner tank 12, respectively.
1 and 42 are provided movably along a vertical movement guide means (not shown), and these steam rising plates 41,
42 is vertically adjusted by feed screws or cams rotated by motors 43 and 44 (FIG. 2), respectively. Then, the steam rising plate 41 on the workpiece loading side is adjusted to a relatively low level,
Further, the steam rising plate 42 on the workpiece unloading side is adjusted to a relatively high level.

Pockets 51 and 52 are provided on the workpiece loading side and the workpiece unloading side of the inner tank 12. A cooling coil 53 is provided inside the pocket 51 on the workpiece loading side, and a perforated plate 54 is provided in the upper opening. A perforated plate 55 is provided at the top opening of the pocket 52 on the workpiece delivery side.

The perforated plates 54 and 55 have a large number of small holes 56, and the speed at which the vapor formed in the steam tank 11 flows down into the pockets 51 and 52 and is liquefied can be controlled by the small holes 56 of the perforated plates 54 and 55. The fluid resistance of the hole 56 suppresses and slows down the flow. This prevents the saturated vapor phase level from falling. At the same time, the pockets 51,
To prevent vapor and mist that have fallen into the air from rising again. In particular, the relatively low-temperature inert liquid condensed at the workpiece loading port 14 and the loading port 15 falls into the pockets 51, 52 through the small holes 56 of the perforated plates 54, 55.
The small hole 56 is cooled, and vapor and mist from rising again from the small hole 56 is effectively suppressed.

A liquid level detection device 61 is connected to the inner tank 12 . In this liquid level detection device 61, a heat radiation header 63 as a heat radiation cylinder made of a large diameter metal cylinder is connected and communicated with a pipe 62 pulled out from the bottom of the inner tank 12. Two transparent pipes 64 made of heat-resistant glass are erected and communicated with each other. This liquid level detection device 61 functions as a communicating pipe with the inner tank 12, and the liquid level in the inner tank 12 appears as it is on the transparent pipe 64. A photo sensor 65 for detecting the upper limit of the liquid level, a photo sensor 66 for detecting the medium level of the liquid level, a photo sensor 67 for detecting the lower limit of the liquid level, a photo sensor 67 for detecting the lower limit of the liquid level, and a photo sensor 67 for detecting the lower limit of the liquid level. Photo sensors 68 for detecting are provided in multiple stages. These photo sensors 65, 66, 67, and 68 each consist of a light emitter and a light receiver that face each other through a transparent pipe 64. This allows the presence or absence of inert liquid at each level to be detected since the emitted light may or may not be sensed by the light receiver.

Then, the inner tank 1 is
The high temperature inert liquid in 2 is radiated, and the transparent pipe 6
The temperature of the inert liquid inside the transparent pipe 64 is kept low to protect the photo sensor provided on the side surface of the transparent pipe 64, and to prevent changes in light transmittance when the inert liquid is in a high temperature state. When the upper limit sensor 65 detects the presence of liquid, the pump (described later) for returning the inert liquid to the primary tank section 32 is stopped, and when the lower limit sensor 67 detects the absence of liquid, the pump for returning the inert liquid to the primary tank section 32 is stopped.
Start the pump to return the inert liquid to.
When the lowest limit sensor 68 detects the absence of liquid, the operation of this vapor phase soldering apparatus (work conveyor, heater, etc.) is stopped.

Next, the piping system diagram shown in FIG. 2 will be explained. The dotted line is a piping system related to mist collection, and the two lines are a piping system related to inert liquid circulation, and all inert liquid circulation piping systems for the primary tank section 32 (this will be explained later) Final return line 7
1, 72, 73, and 74 are connected. Although the final return pipes 71, 72, 73, and 74 are shown as being inserted from the upper part of the steam tank 11 in FIG. 2, they are actually inserted into the primary tank section 32 as shown in FIG. connected to the side of the

The piping system related to mist recovery indicated by the dotted line is provided with suction ports 81 at the upper and lower portions of the workpiece loading port 14 and the workpiece loading port 15, respectively, for sucking the mist to the outside.
A pipe line 82 is drawn out from 1, and the pipe line 82 on the workpiece carry-in side is connected to the upper part of the tank 84 of the liquid recovery unit via a condensation tank 83, and the pipe line 82 on the workpiece carry-out side is directly connected to the It is connected to the upper part of the tank 84. Inside the tank 84 of the recovery unit, there is an air-cooled cooler 86 inside the mist collision plate 85.
is provided, and the suction side of a blower 89 is connected to an air suction port 87 provided above between the mist collision plates 85 via a conduit 88.

The suction force of the blower 89 sucks the mist into the tank 84 from the suction port 81 of the steam tank 11, and the mist is liquefied by the cooling action of the mist collision plate 85 and the cooler 86, and only air is liquefied. The air is exhausted by the blower 89.

Cooling coils 16, 18, 5 in the steam tank 11
3 and the cooling coil 93 in the condensing tank 83 are supplied with cooling water.

The inert liquid circulation piping system represented by two lines includes pipes 101 and 1 drawn out from pockets 51 and 52.
The suction side of a circulation pump 104 is connected through a pipe 103 that communicates with both of the pumps 10 and 02.
The discharge side of No. 4 is connected to the final return conduit 71. Similarly, a conduit 10 communicating with both conduits 101 and 102 drawn out from pockets 51 and 52
5, the suction side of a circulation pump 106 is connected, and the discharge side of this pump 106 is connected to the final return line 72.

In addition, the pipe line 11 drawn out from the bottom of the inner tank 12
1 is connected to a surge tank 114 via an electric valve 113 in a conduit 112. The surge tank 114 also includes the pipes 101 and 102 drawn out from the pockets 51 and 52 as well as the electric valve 1 in the pipe 115.
It is connected via 16. This surge tank 1
14 is an electric valve 11 when filtering the inert liquid in the inner tank immediately after the device operation is stopped.
3, 116 is opened to cool the high temperature inert liquid taken out from the inner tank 12, etc., to relieve its thermal shock. The bottom of this surge tank 114 is communicated with a filtering tank 119 via a conduit 118 in which an electric valve 117 is provided. A filter is provided inside this tank 119 to remove flux etc. from the inert liquid, and a liquid supply pump 122 is connected to a pipe line 121 drawn out from the bottom of the filtering tank 119.
The suction side of the pump 122 is connected, and the discharge side of the pump 122 is connected to the final return line 73 via a line 123, and is also connected to the pocket 52 via a line 124. Similarly, the suction side of a liquid recovery pump 125 is connected to the lower part of the tank 84 of the recovery unit, and the discharge side thereof is connected to the final return line 73 via a line 126, and to the pocket 52 via a line 127. has been done.

A pipe line 132 for filtering during operation is connected to a pipe line 111 drawn out from the bottom of the inner tank 12 via an electric valve 131, and a pump 133 is installed in this pipe line 132, which is used for removing flux, etc. A front stage filter 134 and a rear stage filter 135 are provided, and this pipe line 132 connects to the final return pipe line 74.
It is connected to the.

An upper preheater 138 and a lower preheater 139 are provided at the workpiece inlet of the steam tank 11 with the workpiece conveyance path in between.
8,139, the workpiece is preheated.

Next, the movement of vapor and mist will be explained based on FIG. The inert liquid 13 is heated by the heater 22 via the heat transfer medium 23, and the steam rising plate 41
A saturated vapor phase (hereinafter simply referred to as vapor) 141 is formed on the primary tank section 32 between the vertical partition plate 31 and the workpiece conveyance level, and a saturated vapor phase (hereinafter simply referred to as vapor) 141 is formed on the primary tank section 32 between the vertical partition plate 31 and the vapor rising plate 42. Vapor 142 is formed on the secondary tank section 33 between the plate 31 and the workpiece conveyance level.

The reason why the vapor 141 on the primary tank section 32 does not rise sufficiently is that the pipes 71 and 7
This is because the inert liquid at a lower temperature than 2, 73, and 74 is returned. Since the inert liquid preheated in the primary tank part 32 is gradually supplied to the secondary tank part 33 through the liquid passage gap 34, the vapor 14 on this secondary tank part 33
2 rises to a sufficiently high level. This vapor 1
41 and 142 are saturated vapor phases forming a constant high temperature region (215°C), but in the upper temperature drop region 143 (near 200°C) there is a mist with larger particle size than the vapor. There is.

Therefore, the workpiece W is transported above the primary tank section 32 through a temperature decreasing region 143, and is preheated in this relatively low temperature (200° C.) region 143, and then transferred onto the secondary tank section 33. Then, the solder paste is transported through a vapor 142, and the latent heat of vaporization of the high temperature (215°C) vapor 142 melts the cream solder applied between the printed wiring board as a workpiece and the parts mounted on the board, and reflow soldering is performed. Ru.

Furthermore, the vapor and mist 144 that overflowed the steam rising plates 41 and 42 fall onto the perforated plates 54 and 55 due to their own weight, enter the inside of the pockets 51 and 52 through the small holes 56, and
cooling coil 53 or conduit 12 in the pocket.
It is liquefied by contacting the low-temperature inert liquid supplied from No. 4,127. The vapor and mist that has fallen into the pockets 51 and 52 are removed by the perforated plates 54 and 55.
cannot be re-ascended due to Further, vapor and mist that are about to leak outside through the workpiece loading port 14 or the workpiece loading port 15 are condensed by the cooling coils 16 and 18, and the inert liquid liquefied in this way is transported into the workpiece. Exit parts 14, 15
It flows down the slope of the pocket and into the pockets 51 and 52. At that time, the cooled inert liquid passes through the small holes 56 of the perforated plates 54 and 55, so the small holes 56
The rise of vapor and mist from 6 is effectively prevented. Also, because there is a pocket 52,
There is no possibility that the low temperature inert liquid will directly flow into the secondary tank section 33.

[Effect of idea]

According to the present invention, via the pipe at the bottom of the liquid tank,
A large-diameter heat dissipation cylinder is connected, and a vertically erected heat-resistant transparent pipe is communicated through the heat dissipation cylinder. Since a photo sensor is installed, this photo sensor can be used to detect the liquid level of the high-temperature inert liquid, which is heated to the boiling point for reflow soldering in the liquid tank, while it is outside at a low temperature. Changes in light transmittance caused by the inert liquid and functional deterioration of the photo sensor itself can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the vapor phase soldering apparatus of the present invention, and FIG. 2 is a piping system diagram thereof. W...work, 11...steam tank, 12...inner tank as a liquid tank section, 13...inert liquid, 22...heater, 62...pipe, 63...heat radiation header as a heat radiation cylinder, 64...transparent pipe, 65, 66, 6
7, 68...Photo sensor, 142...Saturated vapor phase.

Claims (1)

[Scope of utility model registration request] A liquid tank section is provided at the bottom of the steam tank, and the inert liquid contained in this liquid tank section is heated by a heater to form a saturated vapor phase inside the steam tank, and the inert liquid is transported in this saturated vapor phase. In a vapor phase soldering device in which workpieces are reflow soldered using latent heat of vaporization in a saturated vapor phase, a large-diameter heat dissipating cylinder is connected to the bottom of the liquid tank via a pipe. A vapor phase soldering method characterized by a heat-resistant transparent pipe vertically installed through the pipe, and a multi-stage photo sensor for detecting the liquid level in the liquid tank section sandwiching the transparent pipe. Device.