JPH0320303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a vapor phase soldering device having a feature of a liquid circulation system.

(Prior Art) A conventional vapor phase soldering apparatus uses a heater 14 to pump a liquid 13 contained in a liquid tank 12 provided integrally at the bottom of a steam tank 11, as shown in FIG. A vapor phase 15 is formed in the steam tank 11 by evaporation.
Printed wiring board 1 as an object to be soldered
7 is carried in, reflow soldering of the board-mounted components is carried out using the latent heat of vaporization of the vapor phase 15, and the board 17 is carried out to the outside through the carrying-out port section 18 provided on the other side of the steam tank 11. In this case, a cooling coil 19 is provided inside the carrying-in port 16 and the carrying-out port 18, and the cooling coil 1
Although the vapor phase 15 is prevented from leaking to the outside by the condensing action of the cooling coil 19, the leakage of the vapor cannot be completely prevented by the cooling coil 19 alone.

Therefore, conventionally, steam is sucked into the condensation tank 23 from near the openings of the carry-in port 16 and the carry-out port 18 through the suction pipe 22 of the liquid recovery unit 21, and the air is passed through the condenser 24 of the refrigeration cycle and the exhaust pipe. 25 and then forcedly exhausted to the outside by a fan.
The liquid 13a condensed in the condenser 24 and accumulated in the tank 23 is pumped to the liquid return pipe 2 by the pump 27.
8 and then circulated to the liquid tank 12.

(Problems to be Solved by the Invention) However, since the liquid 13a condensed in the condensation tank 23 is at a low temperature (30°C), this liquid 13a
If the liquid is directly returned to the liquid tank 12, the temperature of the liquid in the liquid tank 12 decreases, which affects the level of the vapor phase 15, causing a problem of lowering the level of the vapor phase.

An object of the present invention is to provide a liquid circulation system that does not affect the vapor phase level in a vapor phase soldering device.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a liquid tank 32 with a built-in heater 34 in the lower part of a steam tank 31, and evaporates the liquid 33 in this liquid tank 32 so that the liquid 33 inside the steam tank 31 is heated. A duct-shaped inlet 36 is provided on one side of the steam tank 31 along a conveyor 37a that forms a vapor phase 35 and conveys the soldering object 37 through this vapor phase 35. In the vapor phase soldering apparatus, a duct-shaped outlet section 38 is provided on the other side of the tank 31, and the bottom surfaces of the outlet section 36 and the outlet section 38 are formed in a downwardly sloping shape toward the liquid tank 32. As part of a liquid circulation system that circulates the liquid to the liquid tank 32, a liquid supply pipe 48 is connected to the bottom surface of at least one of the carry-in port 36 and the carry-out port 38 at a position remote from the liquid tank 32. , this liquid supply pipe 4
This is a vapor phase soldering device in which a preheating section 51 is provided between the connecting portion of No. 8 and the liquid tank 32 to heat the returning liquid by the bottom surface, which is heated to a high temperature due to heat conduction from the liquid tank 32.

(Function) In the present invention, by returning the liquid to the bottom surface of at least one of the carry-in port 36 and the carry-out port 38 which are in a high temperature state, this liquid is transferred to the preheating section 51 of the bottom surface.
While flowing down, the temperature rises to an extent that does not affect the high temperature liquid 33 in the liquid tank 32, and the liquid circulates to the liquid tank 32.

(Example) Hereinafter, the present invention will be explained in detail with reference to an example shown in FIG. .

As shown in FIG. 1, a liquid tank 32 is integrally provided at the bottom of the steam tank 31, and this liquid tank 32 contains a special liquid (fluorinated inert solvent, etc.) with a boiling point of 215°C.
Product name: Florinat) 33 is stored.
The liquid 33 is evaporated by a heater 34 inserted into the liquid, and a vapor phase 35 is formed inside the steam tank 31.

A loading port 36 is provided on one side of the steam tank 31 with respect to the steam phase 35 formed in the steam tank 31.
Printed wiring board 3 as an object to be soldered
7 is carried in, reflow soldering is performed by the latent heat of vaporization possessed by the vapor phase 35, and the board 37 is carried out to the outside through an outlet 38 provided on the other side of the steam tank 31. Cooling coils 3 for condensing the vapor phase 35 at the loading port 36, the loading port 38, and the upper part of the steam tank 31
9 is provided. This cooling coil 39 is a coiled (helical) cooling water pipe. 37a is a conveyor for conveying the printed wiring board 37.

The carry-in port 36 and the carry-out port 38 are formed in the shape of a duct, and the bottom surface thereof is formed in a downwardly inclined shape toward the liquid tank 32.

At the inlet port 36 and the outlet port 38, the vapor phase 35 is prevented from leaking to the outside by the condensing action of the cooling coil 39 therein. Since leakage prevention is not perfect, a liquid circulation system is provided that forcibly recovers steam from the vicinity of the openings of the carry-in port 36 and the carry-out port 38, condenses it, and returns the liquid to the liquid tank 32.

This liquid circulation system connects the suction pipe 42 of the liquid recovery unit 41 to the condensation tank 43 from near the openings of the carry-in port 36 and the carry-out port 38,
A condensing coil (evaporator of the refrigeration cycle) 44 is provided inside the condensing tank 43, an exhaust pipe 45 is drawn out from the upper part of the condensing coil 44, an exhaust fan is provided in the exhaust pipe 45, and a lower part of the tank 43 is provided with an exhaust pipe 45. The suction port of a circulation pump 47 is connected to the extraction pipe, and the liquid supply pipe 48 drawn out from the discharge port of the pump 47 is connected to the vicinity of the openings at the bottoms of the carrying-in port 36 and the carrying-out port 38.

By separating the connection part of the liquid supply pipe 48 and the liquid tank 32 in this way, a preheating section is provided at the bottom of the carry-in port 36 and the carry-out port 38 as part of the liquid circulation system. A section 51 is provided.

Then, the loading port 36 and the loading port 3
Steam is sucked into the condensing tank 43 from near the opening of 8 through the suction pipe 42, and the air is forcibly exhausted to the outside by a fan through the condensing coil 44 and the exhaust pipe 45, and is condensed in the condensing coil 44. The liquid 33a accumulated in the tank 43 is passed through the liquid return pipe 48 by a pump 47 to the inlet port 3.
6 and the bottom surface near the opening of the outlet section 38.

At the stage where this liquid flows down on the inclined bottom surfaces of the carry-in port 36 and the carry-out port 38, the liquid flows into the heater 34.
Preheating section 51 heated by conductive heat from
The liquid is heated to a high temperature and circulated to the liquid tank 32.

In this way, the bottom surfaces of the carry-in port 36 and the carry-out port 38 apply heat to the low-temperature liquid supplied from the liquid supply pipe 48 to raise its temperature, but on the other hand, heat is taken away by the returned liquid and the liquid evaporates. The temperature does not rise to the extent that it does.

In such a vapor phase soldering apparatus, when the printed wiring board 37 is carried into the steam tank 31 through the carry-in port 36, the vapor phase 35 produced by evaporation from the liquid 33 by the heater 34 is heated. The latent heat of vaporization (215° C.) melts the cream solder between the board 37 and the parts mounted on the board, and the parts mounted on the board are soldered to the board surface. This board 3
The molten solder is solidified at the stage where solder 7 is continuously carried out to the outside through the outlet 38.

In this embodiment, a liquid recovery unit is exemplified as the liquid circulation system, but the present invention is not limited to this liquid recovery unit. A filtering unit may also be used.

〔Effect of the invention〕

According to the present invention, since the preheating section is provided as a part of the liquid circulation system on the bottom surface of at least one of the carry-in port and the discharge port, the heat possessed by the bottom surface of the carry-in port and the discharge port which are in a high temperature state is absorbed. By using this method, the temperature of the liquid increases in the preheating section immediately before returning to the liquid tank, and the temperature of the liquid in the liquid tank can be lowered, without the need to provide a special heating means separate from the heater in the liquid tank. There is no. Therefore, the level of the vapor phase formed in the steam tank is not affected, and a stable vapor phase level can always be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the vapor phase soldering apparatus of the present invention, and FIG. 2 is a sectional view of a conventional vapor phase soldering apparatus. 31... Steam tank, 32... Liquid tank, 33... Liquid,
34... Heater, 35... Steam phase, 36... Carrying in port, 37... Soldering object, 37a... Conveyor, 38... Carrying out port, 48... Liquid supply pipe, 5
1...Preheating section.

Claims (1)

[Claims] 1. A liquid tank with a built-in heater is integrally provided at the bottom of the steam tank, and the liquid in this liquid tank is evaporated to form a vapor phase in the vapor tank. Along the conveyor that conveys the objects to be soldered, a duct-shaped inlet is provided on one side of the steam tank, and a duct-shaped outlet is provided on the other side of the steam tank, and the inlet and In a vapor phase soldering device in which the bottom surface of the carry-out port is sloped downward toward the liquid tank, the bottom surface of the carry-in port and the carry-out port are used as part of a liquid circulation system that circulates the liquid to the liquid tank. A liquid supply pipe is connected to at least one bottom surface at a position remote from the liquid tank, and the liquid supply pipe is connected to the liquid tank at a high temperature due to heat conduction from the liquid tank. A vapor phase soldering device characterized by being provided with a preheating section for heating a return liquid through a bottom surface.