JPS60124464A - Inert atmosphere device for melting low-melting metal - Google Patents

Abstract

PURPOSE:To obtain easily an inert atmosphere for melting an oxidative low- melting metal by providing a discharge port in the lower part of a vessel provided with a feed hole for an inert gas in the upper part so that the discharge of the gas and putting-in and-out of an object are made possible. CONSTITUTION:A stainless steel plate 14 on which a low-melting metal S is placed is inserted through a discharge port 5 into a vessel 1. An inert gas heated by a gas heater 3 is fed through the feed hole 2 in the upper part of the vessel 1 and the cold air is discharged through the port 5. The vessel 1 into which the device for heating and melting said metal S can be housed is thus filled with the inert gas. Electricity is then conducted to a heater 12 and the metal S is melted.

Description

[Detailed description of the invention] (a) Technology to which the invention pertains The present invention is directed to a method for obtaining an inert atmosphere to prevent oxidation when melting low melting point metals such as Sn, Pb, Bi, and alloys thereof. (b) Description of the prior art When metal is melted in the air, the molten metal combines with oxygen in the air to form a metal oxide, which causes various problems. In particular, when oxides are generated in solders mainly composed of Pb and Sn, the oxides adhere to the soldered parts and not only deteriorate the appearance but also cause soldering defects.

As a method of heating and melting solder for soldering, there is a method in which molten solder is jetted with a pump and the printed circuit board is brought into contact with the jetted portion.
This soldering method involves stirring the molten solder with a pump and then jetting it into the air, which results in particularly severe oxidation. Traditionally, in order to reduce oxidation in jet solder baths, so-called cover wax, such as oil or resin, was floated on top of molten solder, but cover wax gives off a bad odor when heated, and It was difficult to treat.

Furthermore, since the cover wax cannot cover the molten solder that is flowing, it has no effect on preventing oxidation in this area.

It is known that metals will not oxidize if they are dissolved in an inert gas atmosphere such as nitrogen, argon, or carbon dioxide, but obtaining such an atmosphere requires a great deal of effort and large-scale equipment. It is. In other words, to create an inert atmosphere, a completely airtight container is used, the inside of the container is evacuated using a vacuum device, and then an inert gas is injected into the container. In order to increase the temperature, it is necessary to repeat this operation several times, which results in an increase in the amount of inert gas used.

Even when melting solder, if the above-mentioned device is used, good soldering can be performed in a solder bath without oxidation, but it is not easy to use considering the equipment and the amount of inert gas used. Moreover, since the container must be opened when the soldering object is put in or taken out, vacuum and inert gas injection must be performed each time, which poses problems in terms of productivity and economy.

(c) Purpose of the Invention The present invention does not require a completely airtight container, nor does it require a vacuum device, and can create an inert atmosphere in the container to the extent that the metal does not oxidize. It is an object of the present invention to provide a low melting point metal processing apparatus in which materials can be taken in and taken out without disturbing an inert atmosphere.

B) Structure of the Invention The present inventor completed the present invention by paying attention to the fact that when a room is heated with a stove in winter, cigarette smoke wafts horizontally between the ceiling and the floor. This phenomenon occurs when the air that has been warmed by the stove and becomes lighter fills upwards, causing the cigarette smoke to be caught between the warm upper air and the cooler lower air and sway due to lateral force. The higher the temperature, the more warm air from the ceiling will occupy the area, and the smoke will trail downwards. In other words, the present invention fills the container with inert gas from above by gently injecting warmed inert gas from the two parts of the container that have an outlet at the bottom, and cold air flows from the bottom. It is designed to be discharged from an outlet.

In the apparatus of the present invention, a gas outlet is provided at the bottom of the container that can sufficiently cover the portion of the low melting point metal that is heated and melted, and an inert gas inlet is installed at the top of the container. The inlet is connected to an inert gas supply source via a gas heating device.

The reason why the present invention is used for melting low melting point metals is that when high melting point metals such as Fe and N1 have a melting point of 100°C or higher, the surrounding temperature becomes high when melting, and strong convection occurs inside the container. This is because the inert atmosphere inside the container is greatly disturbed, causing air to flow in from the outlet. Usable metals include A1 and low-temperature silver solder, with a melting temperature of 600 to 7.
The dimensions are around 00 degrees Celsius.

(E) Description of the Embodiment FIG. 1 shows an embodiment of the present invention, in which a printed circuit board is soldered with jet solder.

The device of the present invention has an inert gas injection hole (2) in the upper part of the container (1).
), the injection hole is connected to an inert gas supply source (4) via a gas heating device (3), and the injection hole is connected to an inert gas supply source (4) via a gas heating device (3)
) has a discharge port (5) at the bottom, but in order to solder the printed circuit board,
Additionally, fluxer (6), preheater (7), jet soldering bath (8), cooling fan (9), and conveyor device (]0)
etc. are added.

The preheater 7 (7) and the jet solder bath (8) are arranged on a trapezoidal platform (
11) installed on top of the fluxer (6) and cooling fan (
It is located one step higher than 9). The container (1) is installed in such a way as to cover the preheater (7), the jet solder bath (8), and the stand (11). ) is the outlet t5),
(It is 51.

In the above embodiment, first, before energizing the jet solder bath 18) and the preheater (7), an inert gas is heated by the gas heating device (3) through the injection hole (2) drilled in the upper part of the container (1). Inject the gas gently. Then, the warmed inert gas is filled from above the container (1), and the cold air is discharged from the outlet (51, (5). At this time, the filling status of the inert gas is known (( Place a lit incense stick in the container and judge by the position where the smoke from the incense stick is waving like the cigarette smoke mentioned above.Then, the smoke from the incense stick is at the outlet (5).

If the solder starts to come out from (5), it means that the inside of the container has been filled with inert gas, so the jet solder bath and preheater are energized to prepare for soldering.

Convection occurs inside the container due to the melting heat of the jet soldering bath and the heat of the preheater, but the temperature at which the solder is melted (300°C)
However, since heated inert gas is continuously injected little by little from the injection hole, the outflow of inert gas from the outlet is stronger than the inflow of air due to convection. , air never flows into the container.

Once the jet has melted the solder in the solder tank, the transfer device 00
), first apply flux to the printed circuit board using a fluxer (6), then transport it from one discharge port (5) to the preheater 7) installed above, where it is heated. After preheating with the preheater (7),
Soldering is performed in a jet soldering bath (8). Thereafter, the printed circuit board (p) is lowered by a transport device (tto), carried out from the other outlet (5) to the outside of the container, and cooled by a cooling fan (9).

In the above embodiment, the jet solder bath is placed in an inert gas atmosphere inside the container, so no matter how much the molten solder is stirred and jetted, it will not oxidize, and the soldering of printed circuit boards can be done using conventional inert gas atmosphere. Continuous soldering is possible because it can be performed without opening and closing the container unlike in an atmosphere device.

FIG. 2 shows the use of the present invention in a solder ball manufacturing method (Patent No. 981220), which has already been established as a patent by the applicant of the present invention. The method for manufacturing the solder balls is to cut the franked solder wire into chips, place them on a stainless steel plate, and heat and melt them to make them into spherical shapes.If the device of the present invention is used for this purpose, it is possible to use the franked solder wire. This produces very clean solder balls.

The container (1) used to produce spherical solder from chip solder is rectangular and has an outlet (5) at the bottom, an inert gas injection hole (2), and a gas heating device ( 3) The inert gas supply source (4) is the same as shown in FIG. A downward heating heater (1 spring) is installed above the container.

In order to turn chip solder into spherical solder using the above device, a stainless steel plate (14) is placed on the rod (13) that moves up and down, and a large number of chip solders (S) that do not contain flux are placed on the stainless steel plate. Insert the container into the container through the discharge port (5) and place it near the heater (121).In this state, as explained in Fig. 1, heated inert gas is introduced from the injection hole (2) at the top of the container. Fill the container with inert gas by gently injecting it.The inert gas filling status can be easily determined from the smoke of the incense stick.In this way, the container is filled with inert gas. The heater (12) is energized to melt the chip solder on the stainless steel plate fM). At this time, the melted chip solder is surrounded by an inert atmosphere, so it does not oxidize and becomes spherical due to its own surface tension.

After the chip solder becomes spherical, stop heating the heater (1) and allow it to cool in the container. After the solder solidifies, gently lower the rod (13) and exit the container from the outlet (5). The next operation is to place the chip solder on a stainless steel plate, then place it on the rod, gently insert the solder into the container through the outlet, and heat it with a heater to melt it.

When spherical solder is produced using the apparatus of the present invention, not only can continuous work be performed in an inert atmosphere, but also clean solder balls can be obtained without using flux, making it a rational process that does not require flux cleaning afterwards. can be done.

(F) Effects of the Invention In the present invention, since the outlet is installed at the bottom of the container, the outlet can be used to take out and put things in, and continuous heat treatment can be performed. Furthermore, since there is no need to evacuate the inside of the container, there is no need to use an expensive airtight container, and there is also an economical advantage in that a large amount of inert gas is not used as in the conventional vacuum replacement method.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating soldering of printed circuit boards using the apparatus of the present invention, and FIG. 2 is a diagram illustrating the manufacture of solder balls using the apparatus of the present invention.

Claims (1)

[Claims] In equipment that processes low melting point metals in an inert atmosphere,
The container is large enough to cover the heating melting and processing equipment for low melting point metals, and there is an outlet at the bottom of the container that allows gas to be discharged.
An inert atmosphere for melting low melting point metals, further comprising an inert gas injection hole formed in the upper part of the container, and the injection hole is connected to an inert gas supply source via a gas heating device. Device.