JP2000000657A - Non-contact type soldering method, and its soldering iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the soldering in a non-contact manner in a short time by blowing a preheated gas flow against a part to be soldered of a work, preheating the part, blowing a hot main heating gas flow from a tip of a soldering iron, and performing the soldering in the atmosphere surrounded by the preheated gas flow prevent the electrostatic discharge failure of electronic parts. SOLUTION: A soldered part after soldering by a main heating gas flow is gradually cooled by a preheating gas flow, and preferably rapidly cooled below the room temperature. It is preferable to eject the main heating gas flow at 250-600 deg.C and the preheating gas flow at 100-200 deg.C at the flow rate of 0.5-2 liter/min. and under the pressure of 0.1-2 kgf/cm2.G. A nitrogen gas fed to a gas feed passage 21 is lead to a main heating gas generating chamber 17, and heated by a heater 14 to generate the main heating gas flow, and ejected from a first nozzle 19. A part of the gas is led to a preheating gas flow generating chamber 18 and heated, and ejected from a second nozzle 20. The main heating gas flow is not scattered therearound, and the solder is immediately melted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering method and a soldering iron, for example, in which electronic components can be soldered in a non-contact manner.

[0002]

2. Description of the Related Art For example, when assembling electronic equipment, various electronic components and wiring are often soldered to an electronic substrate using a soldering iron.

[0003] In this type of soldering iron, a method in which a tip chip heated by a heater or the like is brought into contact with a land or a work of an electronic substrate to melt the solder and separate the tip chip to solidify the solder is widely adopted.

On the other hand, as shown in FIG. 3, an air passage is formed in a soldering iron 50, a heater 51 is built in, a stainless steel or brass nozzle 52 is attached to the tip, and high-temperature air is blown. Non-contact soldering irons that are soldered have also been proposed.

[0005]

However, in the conventional contact-type soldering method, since the tip is brought into contact with the soldering portion, the life of the tip is short, and it is necessary to ensure the accuracy of soldering. It was necessary to replace it about 40,000 to 50,000 times. In addition, since the advanced chip comes into direct contact with the electronic substrate or electronic component, there is a concern that leakage current, noise, harmonics, static electricity, etc. are transmitted from the advanced chip to the electronic substrate or electronic component, thereby deteriorating the electrical characteristics of the product. Was.

In the conventional non-contact soldering iron, high-temperature air impinges on the work and then scatters around the work, so that heat cannot be concentrated in a spot on a required portion. It takes 4 to 5 seconds to be practical, and is used for removing (reworking) soldered electronic components.

[0007] It is an object of the present invention to provide a soldering method in which soldering of electronic components and the like can be performed in a non-contact manner in such a situation.

[0008]

Accordingly, a non-contact soldering method according to the present invention uses a soldering iron to blow a high-temperature gas flow to a soldering portion of the work to solder the work. A high-temperature main heating gas flow is ejected from all the tips, and a preheating gas flow surrounding the main heating gas flow and having a lower temperature than the main heating gas flow is ejected, and the preheating gas flow is applied to a soldering portion of the work. After spraying and preheating, the main heating gas flow is sprayed onto a soldering portion of the preheated work, and soldering is performed in an atmosphere surrounded by the preheating gas flow.

The main heating gas flow and the preheating gas flow may be air, but nitrogen gas is preferable in consideration of the influence of O _{2 in} the air.

One of the features of the present invention is to form a high temperature inner / outer double gas flow, preheat with an outer gas flow, and perform soldering with an inner gas flow in an atmosphere surrounded by an outer gas flow. It is in the point which was made. Accordingly, the heat of the gas flow inside does not scatter to the surroundings, the soldering can be performed in a short time in a non-contact manner, and the effects of leakage current, noise, and harmonics on the product can be eliminated. However, regarding the static electricity, the gas flow is charged due to the friction of the gas flow, particularly the friction when the gas flow is ejected at a high speed, and there is still a concern about the electric influence on the product.

[0011] Therefore, the ejection pressure of the main heating gas flow and the preheating gas flow is set to a range in which the charging of the gas flow is such that the electric influence is not concerned, specifically 0.1 to 2 kgf / cm.
The pressure is preferably ² · G.

[0012] In order to form a dense and well-soldered solder, the attached molten solder is soldered in an atmosphere that can be slowly cooled with a gentle temperature profile, and immediately cooled immediately before the start of solidification in an atmosphere at room temperature or lower. It is important to do so. In the present invention, the gas flow is made into an inner / outer double, preheated by the outer preheating gas flow, soldered by the inner main heating gas flow, then slowly cooled by the outer preheating gas flow to just before the start of solidification, and then cooled to room temperature. Exposure to the following atmosphere allows rapid cooling. When the present invention is applied to soldering of electronic components, the temperature of the main heating gas flow is set to 250 to 600 ° C., the temperature of the preheating gas flow is set to 100 to 200 ° C., and the gas is ejected at a flow rate of 0.5 to 2 liter / min. Is good.

The rapid cooling immediately before the start of solidification of the molten solder may be performed by exposing it to the atmosphere. However, the molten solder releases latent heat upon solidification and simultaneously dissolves O ₂ , H ₂ , CO, etc. in the atmosphere. In addition, since oxidation of the solder and porosity may be caused, and oxidation of the solder immediately before solidification is the largest cause of the generation of bridges, horns, and glares, a low-temperature nitrogen gas atmosphere at room temperature or lower may be used. The temperature of the low-temperature nitrogen gas atmosphere is room temperature, specifically, 25 ° C. or lower, but may be lower than the freezing point, for example, −20 ° C. to −30 ° C. in order to secure the quenching effect. When the work surface is exposed to a low-temperature nitrogen gas atmosphere, the molten solder is rapidly cooled from the front side. However, when the low-temperature nitrogen gas is sprayed on the work back side to rapidly cool from the work back side, the rapid cooling effect is promoted. This is preferable because a finer rapidly solidified structure can be obtained.

Further, according to the present invention, it is possible to provide a soldering iron used in the above-mentioned non-contact soldering method.

That is, in the non-contact soldering iron according to the present invention, in the non-contact type soldering iron for performing soldering by blowing a high-temperature gas flow to a soldering portion of a work, A central first nozzle and a second nozzle that opens to cover the outside of the first nozzle are attached, while a heater is built in the iron body, and a periphery of the heater is A main heating gas flow generation chamber is formed in communication with the first nozzle; a preheating gas flow generation chamber is formed around the main heating gas flow generation chamber in communication with the second nozzle; The trowel body is provided with a gas supply passage for supplying gas to the main heating gas flow generation chamber and the preheating gas flow generation chamber. Ejected from Le, characterized in that none from the second nozzle is generated a low-temperature preheating gas flow to be ejected surrounds the main heating gas flow than the main heating gas by convection radiation heating.

By the way, even if the ejection pressures of the main heating gas fluid and the preheating gas fluid are appropriately set as described above, the charging of the gas flow still remains. Therefore, the main body of the iron is grounded, and a negative charge is electrostatically induced inside the main heating gas flow generation chamber and the preheating gas flow generation chamber so that the positive charge of the main heating gas flow and the preheating gas flow can be removed. Is good.

[0017]

According to the present invention, of the inner and outer double gas flows ejected from the tip, after being preheated by the outer preheating gas flow, the preheating is performed in an atmosphere surrounded by the outer preheating gas flow. Since the soldering is performed with the inner main heating gas flow, the heat of the main heating gas flow blown to the work soldering part does not scatter around, and is efficiently transmitted to the work soldering part, Non-contact soldering can be performed within a short time.

As a result, it is possible to prevent the electrical characteristics of the product from deteriorating due to the contact of the tip, and to properly set the ejection pressures of the main heating gas flow and the preheating gas flow and to ground the trowel main body, thereby reducing the gas. The charging of the current can be reliably prevented, thereby preventing the electronic components from being electrostatically damaged and ensuring the electrical characteristics of the product.

Further, since the soldering can be performed in an atmosphere in which the molten solder is slowly cooled, the molten solder has a substantially hemispherical shape which is a preferable bulging state due to its surface tension. Also, immediately before the start of solidification of the molten solder, it is rapidly cooled in an atmosphere at room temperature or lower, and it is possible to give the molten solder directional solidification in which the distance between its liquidus and solidus is substantially reduced. This allows the solder to have a finely solidified structure.

As a result, there is no scatter of solder balls, bridges or solder, and it is dense, has very few segregation of Pb and Sn and has very few pores, has excellent heat shock resistance, and has high quality non-oxidizing and non-cleaning with good build. Can be soldered.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to specific examples shown in the drawings. 1 and 2 show a preferred embodiment of a non-contact soldering iron according to the present invention. The rear end of the iron main body 11 is attached to the tip of the iron base 10 by screwing or the like. The iron main body 11 is made up of an inner and outer double stainless steel cylinders 12 and 13 and a central rod-shaped alumina ceramic heater 14. And

The heater 14 has a metal cover 15.
The inner surface of the inner stainless steel cylinder 13 is supported by the inner surface of the inner stainless steel cylinder 13, and a plate-shaped spacer portion 16 is formed at the rear end of the cover 15. Heating gas flow generation chamber 17 for generating air, stainless steel cylinder 1 inside and outside
Between 2 and 13, there is a preheating gas flow generation chamber 18 that generates a preheating gas flow lower than the main heating gas flow by convective radiation heating.

Further, a first nozzle 19 made of molybdenum is fitted to the tip of the inner stainless steel cylinder 13, and the first nozzle 19 protrudes from the tip of the outer stainless steel cylinder 12. At the end of the first nozzle 19
A second nozzle 20 that covers the entire outer periphery of the nozzle is externally fitted.

A gas supply passage 21 is formed in the trowel base 10 in a hollow shape, and a first gas flow port 22 is provided at a rear end of the trowel main body 11.
6, a second gas flow port 23 is formed at the tip of the cover 15, and a third gas flow port 24 is formed at the distal end of the cover 15. The main heat gas flow generated in the main heat gas flow generation chamber 17 is supplied to the first gas flow port.
Of the nozzle 19.

Further, a fourth gas flow port 25 is formed in the inner stainless steel cylinder 13 behind the cover 15, and a fifth gas flow port 26 is formed at the tip of the outer stainless steel cylinder 12.
The preheating gas flow generated in the preheating gas flow generation chamber 18 is guided toward the second nozzle 20.

Further, a sensor 27 for detecting and controlling the temperature of the main heating gas flow 30 is attached to the tip of the heater 14, and the stainless steel cylinders 12 and 13 are grounded though not shown. It is connected.

Next, a soldering method will be described. When soldering is performed in a non-contact manner using the soldering iron of this example, first, the heater 14 is energized, and a nitrogen gas (or air) is supplied to the gas supply passage 21 in the iron base 10. The nitrogen gas (or air) may be preheated to a predetermined temperature, for example, 40 to 50 ° C. Then, the nitrogen gas is guided to the main heating gas flow generation chamber 17 through the gas circulation ports 22 and 23, and is heated to 250 to 600 ° C. by the heater 14 to generate the main heating gas flow 30. 30 is ejected from the first nozzle 19 through the gas flow port 24. The jet amount of the main heating gas stream 30 is 0.5 to 2.0 liter / min, and the jet pressure is 0.1 to 2.0 liter / min.
It is set to 1 to 2.0 kgf / cm ² · G.

At the same time, part of the nitrogen gas is
Through the preheating gas flow generation chamber 18, and convection of the high-temperature nitrogen gas in the main heating gas flow generation chamber 17 and radiant heat from the heater 14.
The preheated gas flow 31 is generated by being heated to 00 to 200 ° C., and is ejected from the second nozzle 20 through the gas flow port 26 so as to cover the periphery of the main heated gas flow 30. The ejection amount of the preheating gas stream 31 is set at 0.5 to 2.0 liter / minute, and the ejection pressure is set at 0.1 to 2.0 kgf / cm ² · G.

When the preparation is completed, a preheating gas flow 31 is first blown onto the soldering portion W of the substrate to
After preheating, the main heating gas stream 30 is blown, and the high-temperature main heating gas stream 30 is preheated as shown in FIG.
Is sprayed onto the soldering portion W in a state where the solder is covered, and the solder is not immediately scattered to the surroundings as in the related art, so that the solder is immediately melted. Thereafter, the molten solder is gradually cooled by the preheating gas flow 31 until just before the start of solidification, and is rapidly cooled by being exposed to the atmosphere.

According to the experiments conducted by the present inventors, it took four to five seconds for the conventional non-contact soldering iron to complete the soldering, but the non-contact soldering iron of the present example was used. It was confirmed that soldering could be completed in about one second. Therefore, it was confirmed that the non-contact type soldering iron of the present example can be practically used instead of the contact type soldering iron in the conventional welding robot or automatic welding machine.

When the heat of the molten solder is rapidly absorbed into the surroundings, the molten solder is rapidly cooled as a whole to form fine quenched crystals, fine columnar crystals, and fine free crystals. In the crystal, a grain boundary containing impurities and gas is easily generated in parallel with the crystal column, and the free crystal tends to contain flux gas and impurity gas. On the other hand, since the main heating gas flow 30 and the preheating gas flow 31 having appropriate pressures are blown to the molten solder, the molten solder is pressurized without the solder or flux flowing out of the soldering portion W. The gas can be released, eliminating bubbles and gas holes. In addition, the dendrite can be filled with the molten solder by the pressurization due to the pressurization, thereby preventing microporosity and macroporosity (porosity), and forming a dense crystal structure.

Accordingly, the entire molten solder is quenched to substantially reduce the distance between the liquidus and solidus of the molten solder, exert a pressurizing effect, and produce macroscopic segregation (Pb, Sn).
And the like, and dendrites, layered structure, nucleated structure, etc. of micro segregation are reduced to obtain a solidified solder having a fine crystal structure with few impurities and gas.

The main heating gas flow 30 and the preheating gas flow 3
1 is set appropriately, so that charging due to gas friction is unlikely to occur, and since the iron body 11 is grounded, even if the gas flows 30, 31 are positively charged, the main heating gas flow A negative charge can be electrostatically induced inside the generation chamber 17 and the preheating gas flow generation chamber 18 to remove the positive charge of the main heating gas flow 30 and the preheating gas flow 31, resulting in electrostatic breakdown at the soldering site W. Can be reliably eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a preferred embodiment of a non-contact soldering iron according to the present invention and a cross section taken along line II of the preferred embodiment.

FIG. 2 is a diagram for explaining a soldering method according to the embodiment.

FIG. 3 is a schematic configuration diagram showing a conventional non-contact soldering iron.

[Explanation of symbols]

 Reference Signs List 11 Iron body 17 Main heating gas flow generation chamber 18 Preheating gas flow generation chamber 19 First nozzle 20 Second nozzle 21 Gas supply passage 30 Main heating gas flow 31 Preheating gas flow W Soldering site

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E319 AA01 AC01 CC49 CC54 CC58 CD31 GG03 GG11 GG15

Claims (6)

[Claims] When a high-temperature gas flow is blown onto a soldering portion of a work using a soldering iron to solder the work, a high-temperature main heating gas flow is ejected from the tip of the soldering iron and the main heating is performed. A preheating gas flow surrounding the gas flow and having a lower temperature than the main heating gas flow is jetted out, and the preheating gas flow is blown to a soldering portion of the work to preheat the work, and then the soldering of the work in which the main heating gas flow is preheated is performed. A non-contact soldering method, wherein the soldering is performed in an atmosphere surrounded by the preheating gas flow. 2. The non-contact soldering according to claim 1, wherein the soldering portion after the soldering by the main heating gas flow is gradually cooled by the preheating gas flow and then rapidly cooled to room temperature or lower. Method. 3. The method according to claim 1, wherein the main heating gas stream at a temperature of 250 to 600 ° C. is supplied at a flow rate of 0.5 to 2 liters / minute and a temperature of 100 to 2
The non-contact soldering according to claim 1 or 2, wherein the preheated gas stream of 00 ° C is jetted at a flow rate of 0.5 to 2 liters / minute at a pressure of 0.1 to ² kgf / cm ² · G. Method. 4. The non-contact soldering method according to claim 1, wherein nitrogen gas or air is used for said main heating gas flow and said preheating gas flow. 5. A non-contact type soldering iron for performing soldering by spraying a high-temperature gas flow onto a soldering portion of a work, wherein a tip of a central first nozzle is provided at a tip of a main body of the iron; A second nozzle that opens and covers the outside of the nozzle is attached, while a heater is built in the iron body,
A main heating gas flow generation chamber is formed around the heater in communication with the first nozzle, and a preheating gas flow generation chamber communicates with the second nozzle around the main heating gas flow generation chamber. The main body of the iron is provided with a gas supply passage for supplying gas to the main heating gas flow generation chamber and the preheating gas flow generation chamber, and a high temperature main heating gas flow is generated by heating the heater. The method is characterized in that a preheating gas flow which is ejected from the first nozzle and which is lower in temperature than the main heating gas flow by convective radiation heating is generated and is ejected from the second nozzle surrounding the main heating gas flow. And a non-contact soldering iron. 6. The main body of the trowel is grounded, and a negative charge is electrostatically induced inside the main heating gas flow generation chamber and the preheating gas flow generation chamber to generate a positive charge of the main heating gas flow and the preheating gas flow. 6. The non-contact soldering iron according to claim 5, which is removable.