JPH05169249A - Nitrogen seal jetting type soldering device - Google Patents

Abstract

PURPOSE:To provide a nitrogen seal jetting type soldering device, in which the nitrogen atmosphere necessary for executing the soldering process can surely and easily be obtd. in the upper part of the soldering vessel with a small quantity of the nitrogen gas. CONSTITUTION:Above the upper surface of a soldering vessel 8' and below a conveying line L for conveying materials to be soldered, nitrogen gas supplying pipes 14 for supplying the nitrogen gas are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen-enclosed jet type soldering apparatus in which at least a soldering step is performed in a nitrogen atmosphere.

[0002]

2. Description of the Related Art Conventionally, a printed circuit board is generally soldered by a jet type (automatic) soldering device. FIG. 8 shows an example of a jet type soldering device.
In this soldering apparatus 1, reference numeral 2 is a conveyer conveyor for conveying an article to be soldered (for example, a printed circuit board) to be soldered. The transfer conveyor 2 is composed of two tracks 2a and 2b provided in parallel and facing each other. Soldered products are those tracks 2
It is conveyed in a state of being installed between a and 2b. Below the transfer conveyor 2, along the extending direction of the transfer conveyor 2 from the inlet side (front side in the drawing) toward the outlet side, the fluxer 5, the warm air heater 6, the preheater 7, the solder bath 8, The cooling fan 9 and the like are sequentially arranged.

With this configuration, the printed circuit board carried into the soldering device 1 from the entrance side of the conveyor 2 is first coated with flux by the fluxer 5 and then applied to the warm air heater 6. The flux is dried, preheated by the preheater 7, soldered in the solder bath 8, cooled by the cooling fan 9 and then carried out and moved to the next step. Will be things.

By the way, in the soldering apparatus (process) as described above, conventionally, a flux containing pine resin (rosin) or a halide is used as the flux adhered by the fluxer 5. If this flux remains on the printed circuit board, it may cause corrosion or decrease in insulation resistance. Therefore, cleaning with chlorofluorocarbon or trichloroethane was performed after the soldering process. However, in recent years, it has been determined that these fluorocarbons and trichloroethane are internationally regulated as ozone-depleting substances.

Under these circumstances, recently, a soldering apparatus which does not require cleaning of flux in the soldering process of a printed circuit board has begun to be provided. It was developed from the following viewpoints. In other words, the flux is a so-called reducing agent (antioxidant), and the stronger the action, the better the original function of the flux is. However, such flux has a large amount of residue, which requires cleaning after soldering. .. In other words, the soldering apparatus described above uses a flux having a small reducing action to volatilize the flux in the soldering process, thus eliminating the need for cleaning the flux. When such a flux is used, it is feared that the terminals and copper foil will be oxidized before reaching the soldering part, so soldering should be performed in an inert gas (nitrogen gas) atmosphere. There is.

For example, ELECTRONIC PACKING & PRODUCTIO
In N magazine, April 1990 issue, P64-P66, in the jet type soldering device, the entire transport system from the fluxer to the cooling device is covered with a cover in a tunnel shape, and nitrogen gas is supplied to almost the entire area inside the cover. A nitrogen-enclosed jet-type soldering device in which a mouth is arranged and the entire inside of the cover is made into a nitrogen atmosphere is disclosed. In this case, the oxygen concentration inside the cover that covers the entire transport system is about 50 ppm or less. According to the nitrogen-filled type soldering apparatus as described above, good soldering can be performed even if a flux having a small reducing action is used.

[0007]

However, as a result of earnest research, the inventors of the present invention have found that, in the nitrogen-enclosed jet type soldering apparatus as described above, the entire conveying system corresponding to each process is not made to be a nitrogen atmosphere. In addition, it was found that the soldering can be performed satisfactorily if only the part corresponding to the soldering tank to be soldered has a nitrogen atmosphere, and in that case, if the surroundings of the soldering tank have a nitrogen atmosphere with an oxygen concentration of less than 5%. Got

The present invention has been made in view of the above circumstances, and in particular, in a nitrogen-enclosed jet type soldering apparatus in which at least the peripheral portion of the solder tank is soldered in a required nitrogen atmosphere, at the time of soldering. It is another object of the present invention to provide a nitrogen-filled jet-type soldering device that can create more advantageous conditions.

[0009]

The invention according to claim 1 is
A transport conveyor for transporting the article to be soldered, and a solder tank provided below the transport conveyor,
A nitrogen-encapsulated jet-type soldering device configured to perform at least soldering of the article to be soldered in the solder bath in a nitrogen atmosphere, wherein nitrogen for supplying nitrogen gas to the vicinity of the solder bath. The supply unit is provided at least above the solder bath and below the transfer line of the soldering object to be transferred by the transfer conveyor.

According to a second aspect of the present invention, in the nitrogen-enclosed jet type soldering apparatus according to the first aspect, the solder bath has a nozzle for injecting molten solder upward, and the nitrogen supply section is It is characterized in that it is provided at least on the front side in the transport direction of the transport conveyor with respect to the nozzle.

According to a third aspect of the present invention, in the nitrogen-filled jet-type soldering device according to the first or second aspect, the nitrogen supply section extends in a width direction orthogonal to the transfer direction of the transfer conveyor. It is characterized by doing.

[0012]

In the nitrogen-filled jet type soldering device according to the first aspect, the space formed between the lower surface of the soldered article and the molten solder surface when the article to be soldered reaches the upper portion of the solder bath. Is filled with the nitrogen gas supplied from the nitrogen gas supply port. Since the space formed between the lower surface of the article to be soldered and the molten solder surface is extremely small, it is possible to easily create a nitrogen atmosphere having an extremely high nitrogen gas concentration on the lower surface of the article to be soldered.

In the nitrogen-filled jet type soldering device according to the second aspect, the nitrogen atmosphere can be reliably formed in the portion to be soldered on the lower surface of the article to be soldered.

In the nitrogen-filled jet type soldering device according to the third aspect, the nitrogen atmosphere can be reliably formed over the entire width of the article to be soldered even when the width of the conveyor is changed.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment describes an example in which the present invention is applied to an apparatus for soldering a mounted printed circuit board. 1 and 2 show the vicinity of a solder bath of a nitrogen-filled jet-type soldering device 15 according to the present invention. In these figures, reference numeral 2 (FIG. 2) is a conveyer conveyor, and 8'is a solder tank provided below the conveyer conveyor 2.

The transfer conveyor 2 has two tracks 2a and 2b arranged in parallel. Each orbit 2
a and 2b have a large number of transfer claws 3, 3, ... Which move endlessly, and the printed circuit board (soldered product) P is directly gripped between the transfer claws 3 as shown in FIG. To be done. As shown in FIG. 2, on both outer sides of the tracks 2a and 2b, frames 10 and 10 extend at substantially the same height as the tracks 2a and 2b in parallel with the tracks 2a and 2b.
The tracks 2a and 2b are supported by the frames 10 and 10, and the transfer angle of the transfer conveyor 2 is changed by changing the angles of the frames 10 and 10.

Below the transfer conveyor 2, in addition to the solder bath 8 ', a fluxer, preheater, etc. (not shown) similar to the soldering device 1 shown in FIG. 8 are provided on the front side of the solder bath 8'. A cooling fan is arranged on the rear side of the solder bath 8 '. Devices other than the solder bath 8 ', such as fluxers and preheaters, are the same as the frame 1
It is supported by 0 and 10.

However, the flux used in the nitrogen-filled jet-type soldering device 15 according to the present invention is a special flux having a small reducing action and does not require cleaning after soldering. Further, the fluxer for applying the flux to the soldering surface of the printed circuit board is of a type in which the flux is sprayed and sprayed.

The distance between the two tracks 2a and 2b, that is, the conveyance width, can be changed and adjusted by a track width adjusting mechanism (not shown).

In the present embodiment, as shown in FIG. 1, the solder baths 8'are formed into two baths by the partition plate 13 in the extending direction of the conveyor 2, and the first nozzle is provided for each bath. 11, and a second nozzle 12 is provided.

Nitrogen supply pipes (nitrogen supply parts) 14, 14 for ejecting nitrogen gas are provided at a position below the carrier line L of the printed circuit board near the upper end of the solder bath 8 '.
Is provided. The nitrogen supply pipe 14 is a through hole (not shown) for ejecting nitrogen gas to the wall of the metal pipe.
Is formed. These nitrogen supply pipes 14 are shown in FIG.
As shown in FIG. 5, the through hole is provided so as to extend in the width direction of the solder bath 8 ′, that is, in the direction orthogonal to the transport direction of the transport conveyor 2, and the through hole is provided above the through hole in the longitudinal direction of the nitrogen supply pipe. Many are formed along it. Further, as shown in FIG. 1, the plurality of nitrogen supply pipes 14 are arranged so as to extend almost entirely from one end to the other end of the printed circuit board moving direction in the upper part of the solder bath 8 '(left-right direction on the paper surface in FIG. 1). Are arranged, in particular with respect to the two nozzles 11, 12, at least those nozzles 11, 12,
12 front side (front side with respect to printed circuit board conveyance direction)
These nitrogen supply pipes 14 are located in the.

A nitrogen gas generated by a nitrogen generator (not shown) is introduced to the nitrogen supply pipes 14, 14, .... In this embodiment, the nitrogen generator used in this apparatus is a nitrogen generator utilizing membrane separation.

A shielded space for enclosing the nitrogen gas supplied by the nitrogen supply pipes 14, 14, ... Is formed in an upper space substantially corresponding to the solder bath 8'in the upper portion of the solder bath 8 '. A shield 19 is provided for this purpose.
As shown in FIG. 1, the shield 19 includes frames 10, 1
With respect to the extending direction of 0, it is formed to be sufficiently longer in the front-rear direction than the length of the solder bath 8 ', and has a width between both frames 10, 10 as shown in FIG. Has been done.

As shown in FIGS. 1 and 2, the shield 19 has an upper cover 16A provided above the conveyor 2 and a lower cover 16B provided below the conveyor 2. The upper cover 16A and the lower cover 16B are provided with a shutter 30 that closes the front and rear openings of the space surrounded by the cover.

In this embodiment, both the upper cover 16A and the lower cover 16B are made by bending a stainless plate. As shown in FIGS. 1 and 2, the upper cover 16A has a rectangular top plate 17 and four side plates 18a, 18b, 1 bent vertically downward from the four sides of the top plate 17.
8c and 18d. These side plates 18a
The two side plates 18a, 18c that face each other are arranged in a direction orthogonal to the extending direction of the conveyor 2 (frame 10), and the other two side plates 18b, 18 that face each other.
d is oriented in the direction along the frames 10 and 10, respectively. The upper cover 16A has the side plates 18b, 18
D is attached to the outer surface 10a of the frame 10 by, for example, fixing it with a screw. Most of the top plate 17 of the upper cover 16A is composed of a transparent glass plate 22 fitted in the locking groove 21, so that the solder bath 8'can be seen even from above the upper cover 16A. Is becoming

The lower cover 16B corresponds to the solder bath 8 '.
Corresponding to the above, there is a bottom plate 23 of a size that covers at least the entire upper opening of the solder bath 8 '. Both ends of the bottom plate 23 (ends in the left-right direction on the paper surface in FIG. 1) rise upward, and the rising ends are bent horizontally outward to form a mounting portion 24. This mounting portion 24 is the frame 1
It corresponds to 0 and 10 and is attached to the lower surfaces 10b and 10b by screws, for example.

The portion of the bottom plate 23 corresponding to the solder bath 8'has a rectangular opening 25 as shown in FIG.
The upper surface of the solder bath 8'can be seen from the opening 25. As shown in FIG. 1, the bottom plate 23 has the nozzles 1
1 and 12 are located below the spouting ports 11a and 12a, and therefore these spouting ports 11a and 12a
Is at a position slightly above the opening 25. However, the bottom plate 23 is located above the upper end of the outer wall of the solder bath 8 '.

As shown in FIGS. 1 and 2, shield plates 26a, 26b, 26c and 26d project downward from the four sides which are the peripheral portions of the opening 25, respectively, and the lower portions of the shield plates 26a, 26b, 26c and 26d project downward. It is inserted inside the solder bath 8 ', that is, in the molten solder. And this
The gap between the lower cover 16B and the solder bath 8'is shielded. These shield plates 26a to 26d are provided in a position close to the inner wall surface side plate of the solder bath 8'in a non-contact state with the inner wall surface.
It is located well outside 12 The shield plate 2
Of the 6a to 26d, the pair of shield plates 26b and 26d provided in the extending direction of the transport conveyor 2 includes the solder bath 8 '.
Since it crosses the partition plate 13, the portion corresponding to the partition plate 13 has a form in which the partition plate 13 is escaped by the groove 27 as shown in FIG. 1 or 4. Further, in FIG. 4, a hole indicated by reference numeral 28 is a hole formed in the shield plate 26c for passing each of the nitrogen supply pipes 14.

In this case, the shutters 30 are provided at two positions between the tracks 2a and 2b and between the track 2b and the frame 10 as shown in FIG. The shutter 30 (30A, 30B) has a plurality of screens 31,3.
1, ... Are arranged in the width direction. These screens 31 are made of a flexible film body. As shown in FIG. 6, the screens 31 have upper ends near the inner upper ends of the side plates 18a and 18c.
Guide rails 32, 32 provided in parallel with a, 18c
It is adapted to be engaged with a groove 33 formed between and to be slidable along the guide rail 32. , Each screen 31 is, in this case, as shown in FIG.
The upper surface of one end 34a of the upper bent portion 34 hooked on the guide rail 32 in the width direction is hooked to the lower surface of the other end 34b of the screen 31 adjacent to the screen 31, and the adjacent screens are adjacent to each other. 31 prevents the gaps from being generated between the two.

By the shutters 30 (30A, 30B), the openings of the upper cover 16A and the lower cover 16B are always closed regardless of the movement of the track 2b. Further, the transport path of the printed circuit board P is also blocked by the shutter 30 (30A),
Since the screen 31 constituting the shutter 30 is made of the flexible film body as described above, the printed circuit board P can easily push the screen 31 away and pass through the shutter 30.

Next, the operation of the nitrogen-filled jet-type soldering device (hereinafter abbreviated as "soldering device") 15 having the above-mentioned structure will be described.

In the operating state of the soldering device 15, the nitrogen supply device (not shown) is operated and nitrogen gas is ejected from the nitrogen supply pipes 14, 14, .... Other operations are the same as those of the conventional jet-type automatic soldering device. The printed circuit boards P to be soldered are sequentially transported by the transport conveyor 2, and first, a flux having a low reducing action is applied to the soldering surface (rear surface) by a spray type fluxer (not shown), and then passes over the preheater. It approaches the solder bath 8 '. The printed circuit board P near the solder bath 8'is the shutter 30A.
Through the inside of the shield 19 in a nitrogen atmosphere and soldered in the solder bath 8 '. At this time, as shown in FIG. 7, when the printed circuit board P to be soldered reaches the upper portion of the solder bath 8 ′, it is sandwiched between the printed circuit board P and the molten solder M on the lower surface side of the printed circuit board P. An extremely narrow space C is formed. By the way, nitrogen supply pipes 14, 14, ... Are provided below the transfer line L of the printed circuit board P on the upper surface of the solder bath 8 '.
Therefore, the space C becomes a nitrogen atmosphere in which the oxygen concentration is close to 0 (zero) and the nitrogen gas concentration is extremely high even with a small amount of nitrogen gas. As a result, it is possible to effectively prevent oxidation of terminals, copper foil, and the like on the printed circuit board P, enable the use of a flux having a low reducing action, and eliminate the flux cleaning step.

In addition, since the nitrogen supply pipe 14 is provided at least on the front side of each of the nozzles 11 and 12 as described above, the space C portion having the high nitrogen concentration as described above is surely provided on the front side of the nozzles 11 and 12. As a result, the soldering is performed in a nitrogen atmosphere having an extremely high concentration.

Further, in this embodiment, a shield space is formed by the shield 19 above the solder bath 8 ', and the inside of this shield space is also filled with the nitrogen gas from the nitrogen supply pipe 14. As a result, a nitrogen atmosphere having an oxygen concentration of 5% or less is created inside the shield 19 even when a nitrogen generator utilizing membrane separation (for example, not a nitrogen cylinder) is used as the nitrogen generating means as in this embodiment. Therefore, it is possible to form a nitrogen atmosphere in the entire periphery of the printed board P, and it is possible to further stabilize the nitrogen atmosphere in the space C.

In the present specification, the "nitrogen atmosphere" does not mean a nitrogen gas concentration of 100%, but means a state in which the proportion of nitrogen is higher and the proportion of oxygen is lower than in the normal atmosphere.

The nitrogen supply pipe 14 is a solder bath 8 '.
Since it extends in the width direction, it is possible to create a high-concentration nitrogen atmosphere with respect to the entire width of the printed circuit board P, and even if the width of the conveyor 2 (tracks 2a, 2b) is changed, The action is not lost.

The printed circuit board P soldered by passing over the solder bath 8'passes through the shutter 30A on the exit side in the same manner as in the case of the shutter 30A on the entrance side and goes out of the front shield 16 to the next step. Is processed.

As described above, the present invention is intended to form a particularly high-concentration nitrogen atmosphere on the upper surface of the solder bath where soldering is actually performed. The formation of a high-concentration nitrogen atmosphere in other portions is not limited. Therefore, the shielding space as described above may be formed so as to make the wide space above the solder bath 8 ′ a nitrogen atmosphere, and in order to increase the nitrogen concentration of the shielding space in the shielding space, A nitrogen supply port different from the nitrogen supply pipe 14 may be provided.

[0039]

As described above, according to the nitrogen-filled jet-type soldering apparatus according to the first aspect of the present invention, the lower surface side of the article to be soldered is provided between the article to be soldered and the molten solder surface in the solder bath. An extremely narrow space is formed and the space is filled with nitrogen gas, so this space can be used as a nitrogen atmosphere with a very high nitrogen gas concentration, which allows terminals and copper foil to be soldered. It is possible to prevent the oxidization of the above and to use a flux having a low reducing action, and to eliminate the flux cleaning step. Further, since the space formed on the lower surface of the article to be soldered is extremely small, the required nitrogen atmosphere can be formed with a small amount of nitrogen gas, and the consumption of nitrogen gas is also small.
Such an excellent effect.

According to the nitrogen-enclosed jet type soldering device of the second aspect, a space having a high nitrogen concentration can be always formed on the front side of the nozzle, and the soldering is surely performed in a high-concentration nitrogen atmosphere. It can be carried out.

According to the nitrogen-encapsulated jet soldering apparatus of the third aspect, a high-concentration nitrogen atmosphere can be created with respect to the entire width of the product to be soldered, and the width of the conveyor is changed. Even in that case, the action can be maintained.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a solder tank portion of a nitrogen-filled jet-type soldering device according to an embodiment of the present invention.

FIG. 2 is a front side view of FIG.

FIG. 3 is a plan view showing a lower cover of the shield according to the present embodiment.

FIG. 4 is a side view of the lower cover shown in FIG.

FIG. 5 is a front view showing an embodiment of a shutter that constitutes the shield according to the present embodiment together with a conveyor and the like.

FIG. 6 is a perspective view showing the shutter shown in FIG.

FIG. 7 is a partial side sectional view for explaining the operation of the present invention, showing the upper part of the solder bath together with the product to be soldered.

FIG. 8 is a perspective view showing an example of a jet type soldering device.

[Explanation of symbols]

 2 Transport Conveyor 8'Solder Tank 11 First Nozzle 12 Second Nozzle 14 Nitrogen Supply Pipe (Nitrogen Supply Section) 15 Nitrogen Filled Jet-type Soldering Device P Printed Circuit Board (Product Soldered) L Transfer Line

Claims (3)

[Claims] 1. A transport conveyor for transporting an article to be soldered, and a solder bath provided below the transport conveyor, wherein at least soldering to the article to be soldered in the solder bath is nitrogen. A nitrogen-encapsulated jet-type soldering device configured to be performed in an atmosphere, wherein a nitrogen supply unit for supplying nitrogen gas in the vicinity of the solder tank is at least above the solder tank and the transfer. A nitrogen-filled jet-type soldering device, characterized in that it is provided below a transfer line for the products to be soldered that are conveyed by a conveyor. 2. The solder bath has a nozzle for spraying molten solder upward, and the nitrogen supply unit is provided at least on the front side of the nozzle in the transport direction of the transport conveyor. The nitrogen-enclosed jet-type soldering device according to claim 1. 3. The nitrogen-enclosed jet-type soldering device according to claim 1, wherein the nitrogen supply unit extends in a width direction orthogonal to a transfer direction of the transfer conveyor.