JPH0846346A - Soldering device - Google Patents

Abstract

PURPOSE:To make uniform an oxygen concentration in atmospheric gas by a method wherein nitrogen gas containing a trace of oxygen is introduced in a preheating area, nitrogen gas is introduced in a soldering area and nitrogen gas curtains are respectively formed on both sides of the soldering area. CONSTITUTION:A nitrogen gas curtain jet duct 15 is arranged between hoods 7 and 8 and a nitrogen gas curtain jet duct 17 is similarly arranged between the part of an exit 10 for printed boards in the hood 8 and the part 16 of the upper side of a rear structural member of a soldering device. Moreover, nitrogen gas only is discharged downward via the duct 15 to make a gas curtain form and at the same time, nitrogen gas is similarly discharged toward the exit 10 in the hood 8 via the duct 17 at an angle slanted at about 15 to 90 deg. from the horizontal plane downward to make a gas curtain form. Thereby, the inflow of the outside air is stopped and an oxygen concentration in atmospheric gas within a furnace can be kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering apparatus, and more particularly to a soldering apparatus for arranging electronic parts on a printed circuit board, applying flux and then performing a soldering process.

[0002]

2. Description of the Related Art In the electronics industry, printed wiring boards (hereinafter referred to as "substrates") used in electronic equipment after soldering are cleaned to remove flux residue. Most of the cleaning liquid used for this cleaning is Is C
FC (Freon 113) and methyl chloroform, both of which are harmful.

Substrate cleaning used in electronic devices is forced to choose between alternative cleaning solutions and processes and non-cleaning post-flux and process development.

As a method of completely eliminating specific CFCs in the printed board cleaning step, there are a method of changing the cleaning method and a method of realizing no cleaning. The method of changing the cleaning method is as follows. .

When soldering, a water-soluble flux is used to wash with water.

At the time of cleaning using a conventional flux, water mixed with a saponifying agent or other organic solvent such as alcohol is used.

An alternative CFC that does not destroy the ozone layer is adopted.

However, from the viewpoint of sewage treatment problems and safety, many companies in Japan need to improve the flux,
We are working to improve the soldering equipment to eliminate cleaning.

Under such circumstances, the most promising method is soldering in a nitrogen gas atmosphere, and an apparatus and a device for realizing high quality soldering even with a flux having low activity. Development of flux. At the same time that some of the products have already been put to practical use, devices, fluxes, etc., have been released from various companies.

By the way, the automatic soldering method for a printed circuit board is roughly classified into a flow method and a reflow method. In either method, the inside of the soldering apparatus is inactivated by nitrogen gas to suppress oxygen content. As a result, reoxidation inside the device is prevented, and good soldering can be realized even with flux having weak soldering characteristics.

Further, the type of flux used for soldering is conventionally determined according to the degree of oxidation of the printed circuit board to be soldered, and each of these fluxes has its own oxygen demand.

In such soldering, it is important to improve the wettability of the solder, and conventionally, this is controlled by changing the amount of solder and the amount of activator contained in the flux. .

Here, the "wettability" of the solder means that when the flux activation temperature and the solder melting temperature are balanced.
Refers to the fact that the solder becomes compatible with the soldering surface of the component.

[0014]

However, it is extremely difficult to improve the wettability of the solder, and
There is a drawback in that the flux used for soldering must be changed to be adaptable to this depending on the condition of the printed circuit board.

Further, it is desired that the oxygen concentration in the atmosphere gas in the furnace including the preheating area and the soldering area in the soldering apparatus is made uniform, but in the conventional soldering apparatus, the preheater or the solder bath is used. Due to the heat of molten solder in the furnace, the temperature inside the furnace becomes high, while outside air enters through the inlet opening for loading the printed circuit board and the outlet opening for carrying out the printed circuit board. The phenomenon occurs.

Therefore, the oxygen distribution density in the atmosphere gas in the furnace becomes uneven, and it becomes difficult to maintain a uniform oxygen distribution in the furnace, and flux residue is left on the product printed circuit board, which adversely affects the soldering accuracy. Bring As a technique for solving such a problem, there is Japanese Patent Laid-Open No. 6-296.
As shown in Japanese Patent Publication No. 55-55, the inert gas supply nozzles are sequentially arranged in the chamber, and the amount of the inert gas supply to each of the inert gas supply nozzles is increased or decreased according to the temperature of the atmosphere in the chamber. Soldering equipment and actual Kaihei 5-28
As disclosed in Japanese Patent No. 558, a shutter mechanism and a curtain mechanism (a goodwill structure such as a film plate material or a gas curtain by an inert gas such as nitrogen) are attached to a substrate loading and unloading port to form partition walls. The device is known.

However, with any of the above-mentioned soldering devices, it was difficult to keep the oxygen concentration in the atmosphere gas in the furnace uniform at all times to eliminate the flux residue on the printed circuit board and to eliminate the cleaning of the printed circuit board. .

As a result of various experiments and researches, the present inventor has found that oxygen can be added to a nitrogen atmosphere according to the activity of the flux and the concentration of oxygen can be changed to cope with the state of the printed circuit board. .

Further, the inventor of the present invention can prevent the inflow of outside air by blowing nitrogen gas from the outlet side for carrying out the printed circuit board toward the inlet side, and can make the oxygen concentration in the atmosphere gas in the furnace more constant. Found.

The present invention has been made based on these findings.

[0021]

SUMMARY OF THE INVENTION A soldering apparatus according to the present invention comprises a preheating area and a soldering area which are adjacent to each other, a means for conveying parts to be soldered through these two areas, and a small amount of oxygen in the preheating area. That is, a means for introducing a nitrogen gas containing oxygen in the range of 0.005% to 5% as an atmosphere gas, a means for introducing a nitrogen gas as an atmosphere gas into the soldering area, and between the both areas and the soldering area. At the exit side of the first and second respectively
And a means for forming a nitrogen gas curtain.

The first and second nitrogen gas curtain forming means are composed of double pipes of an outer pipe and an inner pipe each having an axially extending slit, and the slits are located on opposite sides.

The slit of the second nitrogen gas curtain forming means forms a nitrogen gas curtain which is inclined downward from the horizontal plane by 15 ° to 90 ° toward the direction of the preheating section.

The means for introducing nitrogen gas containing oxygen includes means for measuring the amount of oxygen in the preheating zone and adjusting this value according to the type of flux used for soldering.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, 1 is an automatic soldering mechanism for applying solder to a soldering surface of a printed circuit assembly and then performing soldering, and 2 is a printed circuit board of a product to be soldered, for example, flux is applied. Conveyor belt, 3 housing, 4 preheater,
5 is a jet type solder bath, 6 is a bath of molten solder, 7 is an upper portion (hood) of the front structural member disposed directly above the preheating section having the preheater 4, and 8 is soldering facing the solder bath 5. An upper part (hood) of the central structural member arranged right above the area, 9 is an inlet for carrying a printed circuit board formed upstream of the preheating area, and 10 is a board for carrying a printed circuit board formed downstream of the soldering area. An outlet is shown, and in the present invention, a suitable amount of oxygen gas, for example, 30 N liter / h, that is, 0.3 Nm ³ / h, is supplied to the discharge pipe 11 arranged in the hood 7 through the opening 11 ′ according to the kind of flux. Flow rate of trace oxygen gas 12N
A constant flow rate of nitrogen gas mixed with m ³ / h of nitrogen gas was introduced, and an opening 12 was formed in a discharge pipe 12 arranged in the hood 8.
Nitrogen gas is introduced through ???, and these gases are uniformly blown downward through the net-like diffusion structure portions 13 and 14 that jut out just above the printed board transport passage.

Further, a nitrogen gas curtain ejection duct 15 is arranged between the hoods 7 and 8, and the nitrogen gas curtain ejection duct is similarly ejected between the outlet 10 portion of the printed circuit board and the upper portion (hood) 16 of the rear structural member in the hood 8. The duct 17 is arranged.

Further, only nitrogen gas of, for example, 12.5 Nm ³ / h is discharged vertically downward at a pressure of, for example, 3.5 kg / cm ² through the gas curtain jet duct 15 to form a gas curtain, and Similar to the above, nitrogen gas is discharged through the gas curtain jet duct 17 toward the outlet 10 of the hood 8 at an angle inclined downward from the horizontal plane by about 15 ° to 90 ° to form a gas curtain.

The gas curtain ejection ducts 15 and 17 in the present invention are respectively composed of an outer pipe 19 having a slit opening 18 in the axial direction and an inner pipe 21 similarly having a slit opening 20 in the axial direction as shown in FIG. The outer and inner pipes 19 and 21 are arranged so that the slit openings 18 and 20 are at 180 ° different positions.

Further, the slits 18 of the outer pipes 19 of the ducts 15 and 17 are arranged so that the directions of the slit openings 18 are at right angles to the conveying direction of the printed circuit board in a horizontal plane.

In the present invention, the nitrogen atmosphere gas containing oxygen released from the release pipe 11 into the duct 7 is produced, for example, as follows.

FIG. 4 shows an atmosphere gas supply device used in the soldering apparatus of the present invention, and the mixing ratio of the nitrogen atmosphere gas containing the trace amount of oxygen gas supplied to the discharge pipe 11 is an oxygen gas source (not shown). _No. ), and the pipelines E ₁ , E ₂ , E ₃ passing through a plurality of flow meters G ₁ -G ₃ having different flow rates and having stop valves D ₁ , D ₂ , D ₃ interposed therebetween, and a nitrogen gas source (Fig. It is determined by the combination with the conduit C connected to (not shown), and is introduced through the flow meter G ₄ and the conduit H. On the other hand, nitrogen gas is introduced into the discharge pipe 12 from the conduit F through the flow meter G ₅ and the conduit J.

In the nitrogen gas curtain jet duct 15, the flow rate is adjusted by a flow meter G ₆ , for example, a flow rate of 1
A nitrogen atmosphere gas containing a trace amount of oxygen to form a gas curtain by sending ^2.5 Nm ³ / h of nitrogen gas at a pressure of 3.5 kg / cm ² and blowing to the preheating area and nitrogen to be applied to the soldering area. Shut off atmospheric gas. Further, in the nitrogen gas curtain jet duct 17,
Nitrogen gas whose flow rate is adjusted by the flow meter G ₇ is delivered.

K is a mixer, L is an oxygen analyzer, and M is a recorder.

[0035]

Since the soldering apparatus of the present invention is constructed as described above, the optimum amount of nitrogen gas containing oxygen according to the type of flux is used in the hood 7 for forming the preheating area of the printed circuit board. , And several kinds of flux can be used in one step of soldering. In addition, there is a great advantage that it can contribute to the improvement of the atmosphere related to the wettability of the solder.

Further, in the soldering apparatus of the present invention,
The gas curtain formed by the gas curtain ejection duct 15 prevents the gas from entering the upper area of the solder bath 5 from the preheating area, and further obliquely from the transfer outlet 10 of the printed board toward the upper area of the solder bath 5. Since the gas curtain is formed through the gas curtain jet duct 17, the upper area is filled with nitrogen gas, which has a great advantage that disturbance due to inflow of air from the outside can be completely prevented.

Further, the duct in the soldering apparatus of the present invention is constituted by a double pipe consisting of an outer pipe and an inner pipe each having a slit, and the slits are arranged so as to be oriented 180 ° different from each other. If gas is introduced into the pipe and this gas is discharged from the slit of the outer pipe through the slit of the inner pipe,
Even if gas is supplied into the inner pipe from one end thereof, there is an advantage that the amount of gas released from the slit of the outer pipe becomes uniform along the slit.

[Brief description of drawings]

FIG. 1 is a vertical sectional view for explaining a soldering device of the present invention.

FIG. 2 is a plan view for explaining the soldering device of the present invention.

FIG. 3 is a perspective view of a duct in the soldering device of the present invention.

FIG. 4 is an explanatory diagram of an atmospheric gas supply device used in the soldering device of the present invention.

[Explanation of symbols]

 1 Automatic Soldering Mechanism 2 Conveyor Belt 3 Housing 4 Preheater 5 Jet-type Solder Tank 6 Bath of Molten Solder 7 Hood 8 Hood 9 Conveying Inlet 10 Outlet 11 Ejection Pipe 11 'Opening 12 Emission Pipe 12' Opening 13 Diffusion Structure 14 Diffusion Structure 15 Gas curtain ejection duct 16 Hood 17 Gas curtain ejection duct 18 Slit opening 19 Outer pipe 20 Slit opening 21 Inner pipe

Claims (4)

[Claims] 1. A preheating area and a soldering area which are adjacent to each other, a means for carrying parts to be soldered through these two areas, a means for introducing nitrogen gas containing oxygen as an atmospheric gas into the preheating area, It is characterized by comprising means for introducing nitrogen gas into the soldering area as an atmospheric gas, and means for forming first and second nitrogen gas curtains between the both areas and on the outlet side of the soldering area, respectively. Soldering equipment. 2. The first and second nitrogen gas curtain forming means comprises a double pipe of an outer pipe and an inner pipe each having a slit extending in the axial direction, and the slits are located on opposite sides of each other. The soldering apparatus according to claim 1, wherein 3. The soldering according to claim 2, wherein the slit of the second nitrogen gas curtain forming means forms a nitrogen gas curtain which is inclined downwardly from a horizontal plane in the direction of the preheating region by 15 ° to 90 °. apparatus. 4. The oxygen-containing nitrogen gas introducing means includes means for measuring the amount of oxygen in the preheating zone and adjusting this value according to the type of flux used for soldering. Soldering equipment.