JP4722735B2 - Impurity removing method and apparatus, soldering apparatus - Google Patents

Description

  The present invention relates to an impurity removal method and apparatus for removing impurities from molten solder, and a soldering apparatus.

Static and wave (jet) type flow soldering apparatuses can perform soldering efficiently and are widely used as methods suitable for industrial production.
In static and wave type flow soldering equipment, solder material is heated and melted in a solder bath, and this flowing solder material (hereinafter referred to as molten solder) is sprayed onto the surface of a substrate to which electronic components are to be soldered. Then, the substrate is brought into contact with the liquid surface of the molten solder, and the molten solder is supplied to the soldering portion between the electronic component and the substrate to perform soldering.

When the static type and wave type flow soldering apparatuses are operated for a long time, there is a problem that impurities contained in the molten solder in the solder bath increase and adversely affect the soldering quality performance.
For example, when heated molten solder comes into contact with an electronic component or a substrate, low melting point components such as Pb (lead) and Bi (bismuth) may be eluted as impurities from the lead plating portion of the electronic component. Further, Cu (copper) may be eluted from the copper foil of the substrate. In addition, the low melting point component contained in the material constituting the electronic component or the substrate is eluted, and impurities contained in the molten solder increase.

In order to solve the above problems, a solder plating method and a solder plating apparatus are provided (for example, see Patent Document 1). In this apparatus (method), the solder bath is rotated, and an intermetallic compound having a large specific gravity is moved and precipitated on the outer peripheral side of the solder bath by centrifugal force, thereby increasing the purity of the molten solder in the center of the solder bath. Then, soldering is performed at the center of the solder tank, that is, at a portion where there is a large amount of high-purity molten solder.
Also, molten solder containing a large amount of intermetallic compounds is discharged from an openable / closable discharge port provided in the lower part of the solder tank.

JP 2004-292866 A

Since the conventional soldering equipment is configured as described above, as soldering continues, impurities contained in the molten solder gradually increase and the uniformity of the solder is lost. There was a problem that the performance deteriorated.
For example, it causes a phenomenon called lift-off in which the interface between the solder and the substrate copper foil peels off at the soldering location.
Further, when the Cu concentration in the molten solder is increased, the melting point of the solder is increased, the viscosity is increased, bridging defects (solder short circuit) and red eye defects (copper foil exposure) are increased, and work quality is deteriorated. .
Pb is also a typical Sn (tin) -Pb solder composition that has been used in the past. However, when Pb is mixed as an impurity in a lead-free solder material, the original purpose (lead-free) is hindered. It will also be.

Also, in the solder plating method and the solder plating apparatus described in Patent Document 1, the intermetallic compound is moved to the inner peripheral side of the solder bath by centrifugal force. The compound disperses and precipitates. Therefore, when the intermetallic compound dispersed and precipitated is to be discharged from the discharge port provided at only one place in the lower part of the solder tank, a large amount of molten solder is also discharged together with the intermetallic compound, which is not always efficient. There was a problem that it could not be removed.
Moreover, since the whole solder tank is rotated, electric power sufficient to obtain a large rotating motor (driving device) and a sufficient rotating speed (centrifugal force) is required.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain an impurity removal method and apparatus and a soldering apparatus that can efficiently remove impurities in a bath.

In the impurity removal method according to the present invention, in a rotating means that is inserted into a bathtub in which a molten substance is accommodated and performs a circular motion with the central portion of the bathtub as a rotation center, a circumferential flow rate is given to the molten substance, Separating impurities having a specific gravity greater than that of the molten material and aggregating them in the center of the bottom surface of the bath; cooling and solidifying the molten material from which impurities have been separated; and aggregating impurities are provided on the bottom surface of the bath And a step of re-dissolving the portion where the impurities are condensed by the heating means and increasing the concentration of the impurities, and a step of discharging the impurities by the discharging means.

According to the present invention, in the rotating means that is inserted into the bathtub in which the molten substance is accommodated and performs a circular motion with the central portion of the bathtub as the center of rotation, a circumferential flow velocity is given to the molten substance, Separating the impurities having a large specific gravity and aggregating them in the center of the bottom of the bath; and cooling means to solidify the molten material from which the impurities have been separated, and heating means provided with the aggregated impurities on the bottom of the bath The step of re-dissolving the portion where the impurities are fused and agglomerated impurities to increase the concentration of the impurities and the step of discharging the impurities by the discharging means can be efficiently removed.
Further, since the removed impurities are concentrated, recycling as a specific substance is possible.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below. 1 is a cross-sectional view showing a schematic configuration of a soldering apparatus including an impurity removal apparatus according to Embodiment 1 of the present invention. In the configuration of FIG. 1, the impurity removing device and the soldering device are integrated (the solder bath is shared).

In FIG. 1, the present soldering apparatus includes a solder bath 2, a rotating rod 5 that rotates in molten solder filled (accommodated) in the solder bath 2, a rotating motor 4 that drives the rotating rod 5, and a solder bath. 2 A side heater 3 a disposed on the outer peripheral side surface, a bottom heater 3 b provided on the bottom surface of the solder bath 2, and an extraction nozzle 6 for sucking impurities from the solder bath 2 are provided.
The rotary rod 5 has an arm portion 5b extending in the radial direction of the solder bath 2 from a rotating shaft 5a coinciding with the center of the solder bath 2, and an insertion portion 5c extending from the end of the arm portion 5b in the solder bath 2 direction. It has. The rotary shaft 5 a is connected to the rotary shaft of the rotary motor 4.

Next, the operation will be described. FIGS. 2-1 to 2-4 are cross-sectional views showing a procedure for refining molten solder by removing impurities in the impurity removing apparatus of FIG. 1, and show successive steps. For simplification, the side heater 3a, the rotary rod 5, the rotary motor 4, and the extraction nozzle 6 are shown only when they are used.
First, as shown in FIG. 2A, in the case where the side surface heater 3a and the bottom surface heater 3b are “ON” and the solder filled in the solder bath 2 is melted (molten solder 1), impurities 7 diffuses in the molten solder 1. This state is the initial state.

Next, as shown in FIG. 2-2, the rotating rod 5 provided with the rotating motor 4 is immersed in the molten solder 1 in the solder bath 2. When the rotary motor 4 is driven, the insertion portion 5c of the rotary rod 5 inserted into the solder bath 2 performs a circular motion around the rotary shaft 5a.
Since the rotating shaft 5a of the rotating rod 5 and the center of the solder tank 2 coincide with each other, as the insertion portion 5c of the rotating rod 5 moves in the circumferential direction (arrow direction in FIG. 2-2), A flow velocity in the same direction is generated in the molten solder 1.
When the flow rate of the molten solder 1 exceeds a certain level, a vortex is generated in the molten solder 1 and the liquid level near the center thereof drops. Along with this, the impurities 7 start to aggregate toward the center of the vortex.

  The impurity 7 is a substance having a specific gravity greater than Sn, such as Pb, Bi, or Cu, or an intermetallic compound composed of these substances. The specific gravity of Sn with respect to the specific gravity of 7.27 is 11.34 for Pb, 9.75 for Bi, and 8.96 for Cu. The specific gravity of Sn-3Ag-0.5Cu solder used as lead-free solder is 7.4.

Hereinafter, a phenomenon in which impurities having a specific gravity greater than that of the solder material aggregate will be described. By rotating the molten solder 1 at a constant speed, a certain pressure is applied to the molten solder 1 and the impurities 7 only in a unique direction. Aggregation pressure due to the above pressure acts between the particles composed of the above substances or intermetallic compounds to cause entanglement between the particles, and the particles gather and aggregate.
If the molten solder 1 is rotated at a non-uniform speed, the pressure is dispersed, and the agglomeration pressure does not act on each particle, so the impurities 7 do not agglomerate.

  The number of rotations of the rotating rod 5 varies depending on the size of the solder tank 2 and the filling amount of the molten solder 1, but is set to about 10 to 150 rpm. With this setting, the molten solder 1 is given a constant speed rotation that causes a vortex to occur at the center of the solder bath 2. In the vicinity of the bottom surface of the solder bath 2, the viscosity of the molten solder 1 increases due to the frictional force, and the centrifugal force does not sufficiently act. At the center and outside of the vortex, the pressure is lower at the center where the liquid level falls. Therefore, the agglomerated impurities 7 are caused to flow toward the center of the vortex due to the pressure difference and precipitate.

  Next, as shown in FIG. 2-3, the rotating rod 5 provided with the rotary motor 4 is removed from the molten solder 1, the extraction nozzle 6 is inserted into the center of the vortex of the molten solder 1, and left until the flow stops. To do. The agglomerated impurities 7 are deposited near the center of the bottom surface of the solder bath 2. The extraction nozzle 6 is inserted from the upper surface opening of the solder bath 2 toward the center of the bottom surface, and the tip opening reaches the vicinity of the center of the bottom surface of the solder bath 2.

Next, as shown in FIG. 2-4, the side heater 3a is set to “OFF” and the bottom heater 3b is set to “ON”.
The molten solder 1 starts to solidify from the upper surface opening portion and the side surface periphery of the solder tank 2 where heat is easily released, and gradually becomes solid solder 1b. Since the solidification temperature (melting point) of the molten solder 1 from which the impurities 7 have been separated is higher than the solidification temperature of the impurities 7, the molten solder 1 is cooled from a portion away from the bottom heater 3b and becomes solid solder 1b. In addition, although the solid solder 1b is described as "solid", it changes from a melt to a solid-liquid mixed state and solid as the cooling progresses.

On the other hand, the agglomerated impurities 7 are melted (remelted) by the bottom heater 3 b and concentrated near the bottom center of the solder bath 2.
The molten solder 1 in the vicinity of the bottom surface is separated from the impurities 7 as the concentration of the impurities 7 progresses, and gradually begins to precipitate as the high-purity solder 1a. At this point, most of the substance that remains in the molten state becomes concentrated impurities 7.
Finally, the concentrated impurities 7 in the molten state are sucked by the extraction nozzle 6 and discharged from the solder bath 2.

As described above, according to the first embodiment, the molten solder 1 in the solder bath 2 is rotated at a constant speed, and the impurities 7 having a specific gravity larger than that of the solder material are aggregated near the bottom center of the solder bath 2. Since the bottom heater 3b is melted and concentrated, the impurities 7 can be separated from the molten solder 1 and the high-purity solder 1a can be refined. Further, since the concentrated impurities 7 are concentrated near the center of the bottom surface of the solder bath 2, they can be easily discharged from the extraction nozzle 6.
Moreover, since the removed impurity 7 is concentrated, it can be recycled as a specific substance.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below. In the first embodiment, the extraction nozzle 6 performs suction from above to remove the concentrated impurities 7. On the other hand, in the second embodiment, instead of the extraction nozzle 6, a drain cock (discharge pipe with a valve) for discharging is provided at the center of the bottom surface of the solder tank 2.

FIG. 3 is a cross-sectional view showing a schematic configuration of a soldering apparatus provided with an impurity removing apparatus according to Embodiment 2 of the present invention. FIG. 3 corresponds to the state of FIG.
In FIG. 3, the present soldering apparatus is provided with a drain cock 8 that is openable and closable at the center of the bottom surface of the solder bath 2 and communicated with the inside and outside of the solder bath 2. When the drain cock 8 is opened, the concentrated impurity 7 is discharged. Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

  As described above, according to the second embodiment, the concentrated impurity 7 that is fluid in a molten state and has a large specific gravity is easily discharged from the drain cock 8, so that the purity can be increased more efficiently. The solder 1a can be refined.

Embodiment 3 FIG.
The third embodiment of the present invention will be described below. In the first and second embodiments, in the impurity removing device, the solder tank 2 is shared by the impurity removing device and the soldering device. That is, the impurity removal device constitutes a part (inside) of the soldering device.
In contrast, in the third embodiment, the impurity removing device is separated from the soldering device, and the soldering device and the impurity removing device are connected by an inflow path (pipe with a valve).

FIG. 4 is a cross-sectional view showing a schematic configuration of an impurity removal apparatus according to Embodiment 3 of the present invention.
In FIG. 4, the impurity removal apparatus 10 has a configuration in which only the soldering processing function is omitted from the soldering apparatus of FIG. 1 or FIG. Does not occur.
The soldering apparatus 20 is an existing static type and wave type flow soldering apparatus, and a printed circuit board 12 serving as a work is immersed in the molten solder 13 filled in the solder bath 11 to perform a soldering process.
The impurity removing device 10 and the soldering device 20 are connected by an inflow path 9 including a valve 9a.

As described above, according to the third embodiment, since the impurity removing device 10 and the soldering device 20 are separated and connected to each other through the inflow path 9, the impurity removing device 10 removes the impurities 7. Can only do. Therefore, higher purity molten solder can be efficiently supplied from the impurity removing device 10 to the soldering device 20.
Further, by making the inflow path 9 a circulation system, impurities eluted in the solder bath 11 of the soldering apparatus 20 can be continuously removed.

Embodiment 4 FIG.
The fourth embodiment of the present invention will be described below. As shown in FIG. 4, in the third embodiment, the impurity removing device and the soldering device are connected by the inflow path 9.
On the other hand, in the fourth embodiment, for example, the high-purity molten solder refined by the impurity removing device 10 without connecting the impurity removing device 10 and the soldering device 20 is used as the solder bath 11 of the soldering device 20. It will be transferred to.
Alternatively, the solder tank 2 itself is made detachable, and the impurity removing device 10 is replaced with the soldering device 20.

  As described above, according to the fourth embodiment, the impurity content in the single solder can be managed by refining the single solder before being used for the soldering process in the impurity removing apparatus 10. it can. Then, molten solder having a higher purity than that of the third embodiment can be supplied to the soldering apparatus.

In the first to fourth embodiments, the impurity removal target is a molten solder, but the present invention is not limited to this. If the specific gravity of the impurities is larger than the specific gravity of the object to be refined (molten material), the present invention can similarly separate the impurities and obtain an object with higher purity.
For example, the present invention can be easily applied to hot dip plating or the like, and if applied to hot dip galvanization or hot dip tin plating, the specific gravity of impurities to be removed should be larger than zinc or tin. .

It is sectional drawing which shows schematic structure of the soldering apparatus provided with the impurity removal apparatus which concerns on Embodiment 1 of this invention. FIG. 2 is a cross-sectional view showing a procedure for refining molten solder by removing impurities in the impurity removal apparatus of FIG. 1. It is sectional drawing which showed the next stage of FIGS. It is sectional drawing which showed the next stage of FIG. It is sectional drawing which showed the next stage of FIGS. 2-3. It is sectional drawing which shows schematic structure of the soldering apparatus provided with the impurity removal apparatus which concerns on Embodiment 2 of this invention. It is sectional drawing which shows schematic structure of the impurity removal apparatus which concerns on Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Molten solder, 1a High purity solder, 1b Solid solder, 2 Solder tank, 3a Side heater, 3b Bottom heater, 4 Rotating motor, 5 Rotating rod, 5a Rotating shaft, 5b Arm part, 5c Insertion part, 6 Extraction nozzle, 7 Impurity, 8 drain cock, 9 inflow path, 9a valve, 10 impurity removal device, 11 solder bath, 12 printed circuit board, 13 molten solder, 20 soldering device.

Claims (6)

In a rotating means that is inserted into a bathtub in which the molten material is contained and performs a circular motion around the center of the bathtub, a flow rate in the circumferential direction is given to the molten material, and impurities having a specific gravity greater than that of the molten material Separating and aggregating in the center of the bottom of the bathtub;
A step of cooling and solidifying the molten material from which impurities have been separated, and melting the aggregated impurities with a heating means provided on the bottom surface of the bath, and re-dissolving the portion where the impurities are aggregated to increase the concentration of the impurities When,
And a step of discharging impurities by a discharging means. A bathtub containing molten material;
A rotating means that is inserted into the bathtub and performs a circular motion around the center of the bathtub as a rotation center, and gives a circumferential flow velocity to the molten material;
Heating means provided on the bottom surface of the bathtub;
A discharge means provided at the bottom center of the bathtub;
The rotating means includes a rotating shaft that coincides with a central portion of the bathtub, an arm portion that extends from the rotating shaft in the radial direction of the bathtub, and an insertion portion that extends from the arm portion in the bathtub direction. An impurity removal apparatus comprising:   The impurity removing apparatus according to claim 2, wherein the discharging means is an extraction nozzle that is inserted from the upper surface opening of the bathtub toward the center of the bottom surface.   The impurity removing apparatus according to claim 2, wherein the discharging means is a drain cock that is inserted into a central portion of the bottom surface of the bathtub and communicates the inside and the outside of the bathtub. The apparatus for removing impurities according to claim 2,
A soldering apparatus, wherein molten solder is accommodated in the bath and soldering is performed. The apparatus for removing impurities according to claim 2,
While containing molten solder in the bathtub,
The soldering apparatus characterized by connecting the solder tank which performs a soldering process, and the said bathtub with piping with a valve | bulb.

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