KR20210100729A - Ultrasonic Soldering Device and Ultrasonic Soldering Method - Google Patents

Abstract

(Objective) The present invention relates to an ultrasonic soldering apparatus and an ultrasonic soldering method, and an object of the present invention is to form a uniform, thin and strong solder layer without thermal damage or ultrasonic damage to the film of a substrate.
(Configuration) An iron tip heating device, an ultrasonic oscillation device, a solder preheating device, a solder slide device, and an iron tip moving device are provided. It is an ultrasonic soldering device characterized by removing the adhering substances on the adjacent substrate and attaching molten solder to the substrate for soldering.

Description

Ultrasonic Soldering Device and Ultrasonic Soldering Method

The present invention relates to an ultrasonic soldering apparatus and ultrasonic soldering method for soldering to a substrate or a portion of a film formed on the substrate.

Conventionally, a solar cell includes an N-type/P-type silicon substrate that converts solar energy into electrical energy, a silicon nitride film that is an insulator thin film on the surface of the silicon substrate, and a method for extracting electrons generated in the silicon substrate. Consists of a finger electrode, a bus bar electrode that collects electrons drawn from the finger electrode, and a lead electrode that draws out the electrons collected in the bus bar electrode to the outside. has been

Further, on the back surface of the solar cell, a lead wire is soldered to an aluminum electrode formed by applying an aluminum paste.

At this time, on the back surface of the solar cell, a lead wire is soldered to the aluminum electrode. However, the strength is weak, a hole is drilled in an aluminum electrode, silver paste is applied and sintered, and a lead wire is soldered to the silver paste portion to ensure strength.

For example, when soldering a lead wire to an aluminum electrode formed on the back surface of a solar cell, making a hole in the aluminum electrode, applying and sintering silver paste thereto, and soldering a lead wire to a part of this silver paste, , there is a problem in that the tensile strength of the lead wire is not sufficiently obtained, or an extra step of applying and sintering the silver paste is required, and thus the cost is increased.

For this reason, it is desired to solder a lead wire to the board|substrate (silicon board|substrate) which comprises a solar cell, or the aluminum electrode formed on the board|substrate firmly and at low cost.

The present inventors increase the cross-sectional area and heat capacity of the iron tip in solder to reduce the heating temperature of the iron tip to reduce thermal damage to the substrate, and also improve the ultrasonic conduction to reduce the ultrasonic output, thereby removing the deposits on the substrate and making it thinner. A uniform solder layer was formed, and the formation of a uniform and thin solder layer was realized without damage to the film of the substrate.

Therefore, the present invention provides an ultrasonic soldering apparatus for soldering a portion of a substrate or a film formed on the substrate, comprising: a substrate preheating apparatus for preheating a substrate to be soldered or a substrate on which a film is formed to a predetermined temperature lower than the melting temperature of the solder; , an iron tip heating device that adjusts the soldering iron tip portion close to the portion of the substrate at a predetermined temperature preheated by the substrate preheating device to a predetermined temperature at which the solder supplied in the state of applying ultrasonic waves is melted; An ultrasonic oscillation device for supplying ultrasonic waves to the heated iron tip portion, a solder preheating device for preheating the thread-shaped solder supplied to the iron tip portion to a temperature lower than the temperature at which the thread-shaped solder is dissolved; A solder slide device for adjusting the speed at which the preheated thread-like solder is supplied to the heated iron tip portion, and the pre-heated thread-like solder by the solder slide device is applied to the heated iron tip close to the substrate at a predetermined speed. An iron tip moving device for moving the iron tip in the soldering direction at a predetermined speed while supplying is provided, the preheated thread-like solder is dissolved by the iron tip portion, and ultrasonic waves are applied to remove the adhering to the adjacent substrate portion, and the substrate portion It is configured to be soldered by attaching the molten solder to it.

At this time, in the shape of the iron tip portion, by making the length in the moving direction of the iron tip longer than the width in the moving direction of the iron tip, thereby increasing the cross-sectional area and heat capacity, heat conduction to the substrate is improved to lower the temperature of the iron tip, thereby reducing the temperature of the film or substrate on the substrate. In order to reduce the thermal damage to the film|membrane in it.

In addition, in the shape of the iron tip portion, the length in the moving direction of the iron tip is longer than the width in the moving direction of the iron tip, thereby increasing the cross-sectional area to improve the heat conduction of ultrasonic waves to the substrate and to improve the removal of attachments to reduce the ultrasonic oscillation output Thus, the ultrasonic damage to the film on the substrate or the film in the substrate is reduced.

In addition, the ultrasonic oscillation output is 2W to 6W, preferably 2W.

In addition, in the shape of the iron tip portion, the length in the moving direction of the iron tip is 3 to 6 times the width in the moving direction of the iron tip, and a solder layer of uniform thickness is formed in accordance with the cycle of the bending length in the moving direction of the iron tip on the board. to form.

In addition, the cross-sectional area of the preheated thread-like solder is made large or small so that the thickness of the solder to the substrate can be adjusted as thin as possible.

In addition, the supply speed of preheated thread-like solder and the moving speed of the iron tip are made to be the same.

In addition, in the supply speed of preheated thread-like solder and the moving speed of the iron tip, the former is made faster than the latter to increase the amount of molten solder to increase the thickness of the solder to the substrate, or the former is made slower than the latter to increase the amount of molten solder The thickness of the solder to the substrate is reduced by reducing

In addition, the moving speed of the iron tip portion is set to 150 mm/s to 200 mm/s to form a uniform and thin solder layer.

In addition, the material of the iron tip or the material for coating the iron tip is made of a material with high hardness and abrasion resistance.

In addition, the material of the iron tip is to be any one of titanium, titanium alloy, silicon or silicon alloy.

In addition, the coating thickness of the iron tip is 5 to 15 μm.

As described above, the present invention increases the cross-sectional area and heat capacity of the iron tip in solder to reduce the heating temperature of the iron tip to reduce thermal damage to the substrate, and also improves ultrasonic conduction to reduce the ultrasonic output on the substrate. It became possible to form a thin and uniform solder layer by removing the deposit, and to form a uniform and thin solder layer without damage to the film of the substrate. These have the following characteristics.

(1) By increasing the cross-sectional area of the iron tip (about 4 times in the experiment), the heating temperature of the iron tip can be lowered by about 90°C (experiment). In this case, it was possible to reduce the thermal damage to the substrate.

(2) Also, in the case of (1), the temperature of the substrate preheating apparatus for preheating the substrate can be lowered by about 30° C., which can also contribute to reducing thermal damage to the substrate.

(3) In the case of (1), by increasing the cross-sectional area of the iron tip (about 4 times in the experiment), the conduction of the ultrasonic waves from the ultrasonic oscillator becomes good, and even if the output is reduced to 2W, the substrate adheres , a thin and uniform solder layer could be formed.

(4) The thickness of the solder layer on the substrate can be realized about 50 µm to 100 µm, which is about half or one-third of the conventional one, and the amount of solder material used is reduced by half or one-third, and the cost can be reduced.

(5) By manufacturing or coating the iron tip of the soldering iron with a high-hardness and wear-resistant metal (titanium, titanium alloy, silicon, silicon alloy, etc.), it has become possible to significantly extend the life of the iron tip.

1 is a block diagram of one embodiment of the present invention.
[Fig. 2] Flowchart 1 for explaining the operation of the present invention.
[Fig. 3] Flowchart 2 for explaining the operation of the present invention.
[Figure 4] It is a flowchart of temperature setting of the present invention.
Fig. 5 is an example of a substrate to be soldered according to the present invention.
[Fig. 6] A structural example of the soldering apparatus of the present invention.
[Figure 7] An improved example of the iron tip of the present invention.
[Figure 8] It is an example of the tip speed (S1) of the present invention.
[Fig. 9] An example of the solder supply rate S2 of the present invention.
[Fig. 10] A temperature setting example of the present invention.
[Fig. 11] An example of setting ultrasonic power according to the present invention.
[Fig. 12] A setting example of the present invention and the prior art.
[Fig. 13] An example of a soldering photo of the present invention.
[Fig. 14] An example of the shape of the iron tip of the present invention.
[Figure 15] It is an explanatory diagram of the treatment of the ABS coating of the present invention.
[Figure 16] It is an explanatory diagram (hardness) of the ABS coating of the present invention.
[Fig. 17] It is an application example for the soldering iron of the ABS coating of the present invention.
[Fig. 18] A surface microscope image example 1 (molybdenum) of the ABS coating of the present invention.
[Figure 19] Example 2 of a surface microscope image of the ABS coating of the present invention.
[Fig. 20] It is a flowchart for explaining the operation of the present invention (without pre-soldering).
[Fig. 21] A ribbon connection example of the present invention.
[Fig. 22] A wire connection example of the present invention.
[Fig. 23] An example of soldering conditions according to the present invention.
[Fig. 24] The soldering conditions and soldering success example of the wire of the present invention.
[Fig. 25] It is explanatory drawing of the presence or absence of pre-soldering, the presence or absence of solder supply, etc. in the ultrasonic soldering of this invention.

(Example 1)

1 shows a block diagram of one embodiment of the present invention. Fig. 1 is an example of ultrasonic soldering on the back surface of a substrate (silicon substrate) of a solar cell, and is applicable to the surface of a substrate of a solar cell.

In Fig. 1, a substrate (solar cell substrate, silicon substrate) 1 is a silicon substrate constituting a solar cell (refer to Fig. 5).

A substrate mounting table (substrate preheating table) 2 is for mounting and preheating the substrate 1 , and is heated to a predetermined temperature below the temperature at which the solder is melted and above room temperature.

The iron tip 3 is an iron tip constituting the soldering device, disposed close to the substrate 1 to be soldered (usually about 30 μm), and heated to a predetermined temperature by the iron tip heating device 4, and It is moved in the soldering direction by the iron tip moving device (S1) (32) in a state in which the ultrasonic wave is applied from the ultrasonic oscillator (5).

The iron tip temperature (T3) (31) is the temperature (T3) of the iron tip.

The iron tip moving device (S1) (32) is a device for moving the iron tip (3) in the soldering direction.

The iron tip heating device 4 heats the iron tip 3 to a predetermined temperature, and is a heating element such as a ceramic heater.

The ultrasonic oscillator 5 oscillates ultrasonic waves and supplies them to the iron tip 3, which generates an ultrasonic output of 2W to 6W.

The solder 6 is a thread-shaped solder supplied to the iron tip 3, and is a solder containing Sn, Zn, etc., but not containing Pb or the like.

The solder preheating device (T2) 7 preheats the thread-like solder 6, and preheats the solder 6 to a temperature below which the solder 6 melts.

As shown in the figure, the solder slide device 8 automatically supplies preheated thread-like solder 6 to the tip portion of the iron tip 3 at a predetermined speed.

Next, the operation of the configuration of Fig. 1 will be described in detail with reference to Figs.

2 and 3 show a flow chart for explaining the operation of the present invention.

In S1 in Fig. 2, a solar cell substrate (an aluminum pattern is formed on the back surface) is prepared. That is, the solar cell substrate (silicon substrate) shown in FIG. 5 mentioned later is prepared. The silicon substrate 1 of FIG. 5 is an aluminum film 11 formed by screen-printing and sintering an aluminum paste on the back surface as shown in FIG. The original silicon substrate 1 without the aluminum film 11 is exposed on a portion of (not shown, on the back surface corresponding to a bus bar electrode formed on the surface).

In S2, the board|substrate mounting table is heated to predetermined temperature T1. That is, the substrate mounting table 2 of Fig. 1 is heated to a predetermined temperature T1 (a temperature slightly lower than the temperature at which the solder 6 is melted).

In S3, the board|substrate is put on the board|substrate mounting stand. Accordingly, the substrates are sequentially placed on the substrate mounting table 2 heated to a predetermined temperature (T1) and sequentially heated to a predetermined temperature (T1).

In S4, the solder preheater and the iron tip are heated to predetermined temperatures (T2 and T3), respectively. That is, the solder preheater 7 of FIG. 1 is heated to a predetermined temperature T2 (a temperature slightly lower than the temperature at which the solder 6 is melted), and the iron tip 3 of FIG. It is heated to a temperature at which the solder 6 is melted).

In S5, the ultrasonic output is set to a predetermined power (W). That is, the ultrasonic output of the ultrasonic oscillator 5 of Fig. 1 is set to a predetermined power W (in the experiment, it is, for example, in the range of 2W to 6W, preferably 2W).

In S6 in Fig. 3, the molten solder is adhered to the silicon substrate (or aluminum surface) by bringing the iron tip close to the substrate surface (about 30 mu m on the substrate). That is, the iron tip 3 of FIG. 1 is brought close to about 30 μm on the back side of the substrate 1 (refer to FIG. 5 (b)), and the aluminum side of the substrate 1 or the exposed surface of the substrate 1 The molten solder in which the thread-like solder 6 supplied to the silicon substrate (silicon surface) is preheated and melted is adhered to the silicon substrate (silicon surface) by removing the deposits on the surface by the supplied ultrasonic waves.

In S7, the iron tip is moved at a predetermined speed S1 from the starting point to the end point of the soldering object.

In S8, the iron tip is lifted at the end point. According to these S6 to S8, the molten solder automatically supplied to the part of the iron tip is adhered from the starting point toward the end point to the part where the adhesion of the aluminum or silicon surface of Fig. 5 (b) is removed on the adjacent substrate. it becomes possible

In S9, it is determined whether it is the end. In case of YES, it is terminated. If NO, move to the next soldering start location in S10, and repeat after S6. For example, in the case of a solar cell substrate (silicon substrate) having a horizontal and vertical length of 150 mm, the experiment was repeated 5 times.

As described above, the iron tip 3 is placed close to the aluminum surface or the silicon surface of the solar cell substrate, and preheated thread-like solder 6 is automatically supplied to the tip of the iron tip 3 to the iron tip. In addition to forming the molten solder in (3), ultrasonic waves are supplied from the iron tip 3 to the aluminum or silicon surface of the adjacent solar cell substrate to remove the deposit, and then the molten solder is adhered while moving from the starting point to the final point. It has become possible to adhere thinly, firmly and cleanly with molten solder without damaging the aluminum or silicon surface of the battery substrate. Thereby, the ribbon (lead wire) is firmly fixed directly to the aluminum or silicon surface of the solar cell substrate (in this case, instead of the thread-like solder 6 of FIG. 1, a pre-soldered ribbon is used), or After pre-soldering with the thread-like solder 6, it became possible to solder the ribbon (even without ultrasonic waves).

Hereinafter, it will be described in detail sequentially.

Fig. 4 shows a temperature setting flowchart of the present invention. That is, the setting of the temperatures T1, T2, and T3 described in FIGS. 1, 2 and 3 will be described in detail.

·Temperature (T1): the temperature of the substrate mounting table of FIG.

·Temperature (T2): the temperature of the solder preheating device of FIG. 1

·Temperature (T3): the temperature of the iron tip (3) in FIG.

In S11 in Fig. 4, the optimum temperature ranges of T1, T2, and T3 are set. That is, the optimum temperature range obtained in advance by experiment is set respectively.

In S12, it is determined whether T1 is a predetermined temperature range. That is, it is determined whether the current temperature T1 is within the optimum temperature range of T1 set in S11. If YES, the process proceeds to S13. If NO, it returns to S11 and repeats.

In S13, it is determined whether T2 is a predetermined temperature range. That is, it is determined whether the current temperature T2 is within the optimum temperature range of T2 set in S11. If YES, the process proceeds to S14. If NO, it returns to S11 and repeats.

In S14, it is determined whether T3 is a predetermined temperature range. That is, it is determined whether the current temperature T3 is within the optimum temperature range of T3 set in S11. If YES, soldering starts at S15. If NO, it returns to S11 and repeats.

As described above, the temperature T1 of the substrate mounting table 2 of FIG. 1, the temperature T2 of the solder preheater 7, and the temperature T3 of the iron tip 3 are the optimum temperatures obtained in advance by experiment. When it is determined that each has been adjusted within the range (to be described later), soldering is started (by performing S5 and later in FIG. 2 as already described), and while removing the adhesions on the aluminum or silicon surface of the solar cell substrate with ultrasonic waves, preliminary It becomes possible to solder by adhering the heated and molten molten solder to the aluminum surface or the silicon surface adjacent from the iron tip.

Fig. 5 shows an example of a substrate to be soldered according to the present invention.

Fig. 5(a) is a cross-sectional view of the back surface of the solar cell substrate (silicon substrate), and Fig. 5(b) is a plan view of the back surface of the solar cell substrate.

5 (a) and (b), on the back surface of the solar cell substrate (silicon substrate) 1, an aluminum film 11 is formed by applying and sintering an aluminum paste as shown by the diagonal line, The portion corresponding to the band-shaped bus bar electrode on the surface, not shown, is formed in a structure in which the silicon surface is exposed without an aluminum film.

According to the present invention, molten solder is adhered to the aluminum film 11 portion of the back surface of the solar cell or the portion where the silicon surface is exposed, followed by soldering.

Fig. 6 shows a configuration example of the soldering apparatus of the present invention. This soldering apparatus consists of an ultrasonic oscillation device (5), a propagation path (51), and an iron tip (3).

6, the ultrasonic oscillator 5 corresponds to the ultrasonic oscillator 5 of FIG.

The propagation path 51 propagates the ultrasonic output generated by the ultrasonic oscillator 5 to the iron tip 3 with good efficiency.

The iron tip 3 is the iron tip 3 of FIG. 1, which is heated to a predetermined temperature T3 and melts the preheated solder to generate molten solder, and transmits the ultrasonic wave generated by the ultrasonic oscillator 5 as a propagation path. After receiving through (51) and propagating to the aluminum or silicon surface of the solar cell substrate disposed adjacently to remove the deposits on the aluminum or silicon surface, the molten solder is adhered and soldered. As shown, the iron tip 3 has a long length (horizontal direction and the direction in which the iron tip 3 moves and solders) with respect to the width (vertical direction) as shown (usually about 2 to 6 times, Figs. 7 and 14). will be described later using ).

As described above, by connecting the ultrasonic oscillation device 5 to the iron tip 3 through the propagation path 51, the ultrasonic wave is supplied to the aluminum or silicon surface of the solar cell substrate disposed close to the iron tip 3 to form the surface of the surface. After the attachment is removed, the molten solder of the iron tip 3 is adhered to the aluminum surface or the silicon surface to enable solid soldering.

7 shows an improved example of the iron tip of the present invention.

Figure 7 (a) shows an example of the shape of a conventional iron tip. The conventional iron tip was soldered using a soldering part 33 having a square or circular shape of 1 mm x 1 mm as shown. In this conventional soldering part 33, there is no directionality, so it is convenient to solder in an arbitrary direction.

However, the contact area of the soldering portion 33 is small, as also in the example of (a), 7 and the 1mm × 1mm rectangle contact area of 1mm ^2, large and the heat resistance of the aluminum surface being in contact with or silicon surface also ultrasonic resistance also big

For this reason, in the experimental example of FIG. 7(b) of the present invention, the width is made the same as 1 mm, the length is quadrupled to 4 mm, and the contact area is quadrupled, and heat to the aluminum or silicon surface to be contacted By reducing the resistance to about 1/4 and also reducing the ultrasonic resistance to about 1/4, as a result, the heating temperature of the iron tip 3 corresponding to this state could be lowered and the ultrasonic output could also be lowered. As a result, by reducing thermal damage and ultrasonic damage to the aluminum surface or the silicon surface, respectively, and forming a thin solder layer (half or 1/3 the thickness of conventional ones), strong and clean soldering is possible.

Figure 7 (b) shows an example of the shape of the iron tip of the present invention. The iron tip of the present invention was soldered using a rectangular soldering part 34 having a width of 1mm and a length of 4mm as shown. Since the soldering part 34 of the present invention has four times the contact area with respect to the aluminum or silicon surface compared to the soldering part 33 of FIG. In addition to being able to reduce it to 4, it was possible to increase the heat capacity (about 4 times) by quadrupling the cross-sectional area of the iron tip 3 .

Figure 7 (c) shows an example of the shape of another iron tip of the present invention. Another iron tip of the present invention has a rectangular soldering part 35 having a width of 1 mm or less and a length of about 4 mm as shown. In this other example of the shape of the iron tip, it is a structure in which a small shape with a width of 1 mm or less and a length of 4 mm or less is added to the tip of the iron tip 3 in FIG. It is a convenient structure if you want. That is, it has a feature that only the width can be arbitrarily reduced to 1 mm or less in a state that is approximately the same as or slightly larger than the shape of the iron tip of FIG.

As described above, by increasing the length of the iron tip in the longitudinal direction (4 times in the experiment), the thermal resistance between the aluminum surface or the silicon surface of the solar cell substrate is reduced (about 1 in the experiment) in a state where soldering of the same width is possible. /4) and increase the heat capacity (about 4 times), as a result, the temperature of the iron tip is reduced and the ultrasonic output is reduced, thereby reducing thermal damage and ultrasonic damage to the aluminum or silicon surface of the solar cell substrate By doing so, it was possible to realize soldering of a thin solder layer while also realizing strong and clean soldering.

8 shows an example of the tip speed S1 of the present invention. That is, the information shown below corresponds to the speed S1 of the iron tip 3 of FIG. 1 .

Here, the speed is the speed S1 of moving the iron tip 3 of FIG. 1 with respect to the aluminum surface or the silicon surface of the solar cell substrate 1 to be soldered. The speed example (mm/s) is a speed example of the upper limit, the optimal range, and the lower limit in the case of the shape of the iron tip of FIG. 7 (b) used in this experiment. The remarks are observations of the solder state at each speed (upper limit, optimal range, lower limit). It will be described below.

(1) If the speed of the iron tip 3 in FIG. 1 is set to 200 mm/s or more, the upper limit, the supply of molten solder from the iron tip 3 to the aluminum or silicon surface of the solar cell substrate 1 is delayed. , since the supply of solder to the surface is cut off halfway as a result, the upper limit of the speed is set to 200 mm/s.

(2) When the optimum range of the speed was 150 to 200 mm/s, the solder could be uniformly and thinly applied to the aluminum surface or the silicon surface of the solar cell substrate 1 .

(3) At 150 mm/s or less, which is the lower limit of the speed, the supply of solder becomes excessive, and places where the solder accumulates on the aluminum surface or the silicon surface occur.

From the above experimental results, the optimum range of the speed of the iron tip 3 in FIG. 1 is 150 to 200 mm/s, and accordingly, even if it is too late or too fast, the solder could not be uniformly and thinly applied to the aluminum or silicon surface. In addition, although the shape of the iron tip 3 of Fig. 7(b) was used in the experiment, other shapes (width, etc.) may be used. Also, if the desired solder thickness, etc. is different, it is necessary to obtain the optimum speed by experiment. do.

Fig. 9 shows an example of the solder supply rate S2 of the present invention. That is, the following information shown in FIG. 1 corresponds to the speed S2 of supplying the solder 6 to the iron tip 3 .

Here, the speed is the speed S2 at which the solder 6 preheated by the solder preheating device 7 of FIG. 1 is supplied to the iron tip 3 by the solder slide device 8 . The remarks are observations of the soldering state in speed (fast (faster than the iron tip speed), optimal range, and slow (slower than the iron tip speed)). It will be described below.

(1) If the speed of the solder 6 supplied by the solder slide device 8 of Fig. 1 is increased (faster than the speed of the iron tip), the solder 6 is moved at a speed faster than the speed of the iron tip 3 ), that is to say, oversupply of solder, so that the molten solder is thickly applied to the aluminum or silicon surface of the solar cell substrate 1, and if it is too fast, solder pooling occurs.

(2) When the speed of the solder 6 is within the optimum range (when the speed of the solder 6 and the speed of the iron tip are the same), the solder is evenly and thinly applied to the aluminum or silicon surface of the solar cell substrate 1 . could be spread

(3) If the speed of the solder 6 is slowed (slower than the speed of the iron tip), the solder 6 is supplied to the iron tip 3 at a speed slower than the speed of the iron tip 3, that is to say, an undersupply of solder, If the molten solder was applied thinly to the aluminum or silicon surface of the solar cell substrate 1, and it was made more slowly, the solder broke in the middle.

From the above experimental results, the optimum range of the supply speed of the solder 6 by the solder slide device 8 in Fig. 1 is the same as that of the iron tip, so that the solder can be applied evenly and thinly. However, it has been found that if the speed is too fast, the solder will collect, and if it is slightly slowed, the solder can be thinned, but if it is too slow, the solder will break in the middle. In addition, it is also possible to adjust (increase or decrease) the thickness of the solder by using the one in which the cross-sectional area of the supplied thread-like solder 6 is changed (increased or decreased).

Fig. 10 shows an example of setting the temperature of the present invention. That is, it corresponds to the substrate mounting table 2, the solder pre-heating device 7, and the iron tip heating device 4 in FIG. 1 to correspond to the following information.

Here, the devices are the substrate mounting table 2, the solder preheating device 7, and the iron tip heating device 4 shown in FIG. The set temperature represents an example of a set temperature set by an experiment for each device, and the set temperature range is an appropriate set temperature range used in the experiment for each device. It will be described below.

(1) The substrate mounting table (T1) (2) of FIG. 1 is a temperature slightly lower than the temperature at which the solder 6 melts and becomes molten solder by the iron tip 3 when ultrasonic waves are applied. In the experiment, 170° C. and the appropriate set temperature range was in the range of 140°C to 200°C.

(2) The solder preheating device (T2) (7) of FIG. 1 preheats the solder (6) to a temperature slightly lower than the temperature at which the soldering iron tip (3) turns into molten solder. In the experiment, it is set to 160°C. and the appropriate set temperature range was in the range of 150°C to 200°C.

(3) The iron tip heating device (T3) (4) of FIG. 1 is the temperature at which the solder 6 is melted and becomes molten solder by the iron tip 3 when ultrasonic waves are applied. In the experiment, it is set to 360°C, A suitable set temperature range was 340°C to 450°C.

In addition, the set temperature and the set temperature range depend on the material of the solder 6 used, and Sn-Zn solder was used in the above experimental example. Since different solder materials have different melting temperatures, it is necessary to obtain and set the set temperature and set temperature range by experiment.

Fig. 11 shows an example of setting the ultrasonic power of the present invention. That is, the following information is made to correspond to the oscillation output power of the ultrasonic oscillator 5 of FIG. 1 .

Here, the power is the ultrasonic oscillation output (power) supplied to the iron tip 3 by the ultrasonic oscillation device 5 of FIG. 1 . W is the power (W) set in the experiment. The remarks indicate information that observed the situation in the case of each power. It will be described below.

(1) When the ultrasonic oscillation power of the ultrasonic oscillation device 5 of Fig. 1 is increased (6W or more in the experiment),

It is possible to lower the iron tip temperature

・Damage or breakage of the substrate or crystal

・The solder bonding surface is not smooth.

phenomenon could be observed. Here, “it is possible to lower the iron tip temperature” means that when the ultrasonic output (power) is increased (for example, 6 W or more), the heating temperature when the iron tip 3 becomes molten solder decreases by increasing the ultrasonic output. This means that the tip temperature (T3) can be lowered as a result. In addition, "substrate or crystal damage or breakage" means that the ultrasonic output is increased. As a result, the large ultrasonic output causes ultrasonic damage to the aluminum surface and silicon surface of the solar cell substrate, thereby damaging the substrate or crystal and film breakage. This means that the likelihood of this happening is high. Also, "the solder bonding surface does not become smooth" means that the solder to the aluminum surface and the silicon surface does not become smooth because of the large ultrasonic output, and thus becomes uneven.

(2) When the ultrasonic power is in the optimum range (for example, within the range of 2W to 6W, preferably 2W), the solder can be uniformly and thinly applied to the aluminum surface and the silicon surface of the solar cell substrate 1 . could

(3) When the ultrasonic power is small (eg 2W or less),

It is necessary to raise the iron tip temperature.

Inability to sufficiently remove oxides, etc.

phenomenon could be observed. Here, “need to raise the iron tip temperature” means that when the ultrasonic output (power) is reduced (for example, 2 W or less), the heating temperature of the iron tip 3 when it becomes a molten solder rises by reducing the ultrasonic output. , means that there is a need to raise the iron tip temperature (T3) as a result. In addition, "the oxide and the like cannot be sufficiently removed" means that, as a result, deposits, oxides, etc. on the aluminum surface and silicon surface of the solar cell substrate cannot be sufficiently removed because the ultrasonic output is made small.

12 shows an example of the present invention and a conventional setting.

Fig. 12 compares the prior art and the present invention for each item, and describes the difference in detail as follows. Here, the item is "Iron tip temperature (T3)" and the like as a comparison item. Conventionally, the conventional specific example of an item is shown, and this invention shows the specific example of this invention of an item. A note is a detailed description of an item.

Here, the iron tip temperature T3 was 450° C. in the prior art, but in the present invention, when the width of the tip shape of the iron tip 3 is made the same, the length is approximately quadrupled and the cross-sectional area is quadrupled (Fig. 7). (b)), the temperature of the iron tip (heating temperature of the iron tip) became 360°C, and it was confirmed by experiment that the temperature was decreased by about 90°C. Accordingly, the temperature when the molten solder of the iron tip 3 is adhered close to the aluminum surface and the silicon surface of the solar cell substrate 1 is lowered, thereby reducing thermal damage.

The substrate preheating temperature (T1) made it possible to lower the iron tip temperature and at the same time, even if the substrate preheating temperature was also lowered by about 30°C from 200°C to 170°C, the iron tip 3 of the present invention (compared to the conventional one). Soldering became possible using an iron tip having a length of about 4 times (refer to FIG. 7(b)).

The speed of the iron tip (S1) could be improved by 28 mm/S to 178 mm/S by using the iron tip of the present invention from the conventional 150 mm/S.

Solder supply was 200 pulses in the present invention.

The iron tip height was conventionally 20 to 30 μm, but in the present invention, it was controlled to 30 μm.

The solder preheating temperature (T2) was not previously available, but in the present invention, it was preheated to 160°C.

The ultrasonic oscillation output was 6W in the prior art, but in the present invention, using the iron tip of the present invention (refer to FIG. By sufficiently removing the deposits on the substrate 1 and adhering the molten solder, it was possible to solder uniformly and thinly (half of the conventional thickness).

The solder weight is 0.02 to 0.03 g per pass conventionally, and 0.1 to 0.15 g of the solder was used in 5 pieces (5 passes) per wafer. In the present invention, since the amount of solder is 0.01 g per pass and 0.05 g of solder is used in 5 pieces (5 passes) in one wafer, the amount of solder used can be reduced by reducing from half to one third compared to the prior art. there was. In addition, in the reduction in the amount of solder used according to the present invention, the thickness of the solder on the aluminum surface and the silicon surface of the solar cell substrate 1 can be reduced from half to one third as compared with the conventional one.

Fig. 13 shows an example of a soldering photo of the present invention. The horizontal direction in Fig. 13 (a) shows an example of a soldering photograph in the case of an appropriate condition (in the case of the present invention in Fig. 12), and it can be observed that the solder is neatly thin and uniformly soldered.

On the other hand, (b) in Fig. 13, the vertical direction shows a photographic example of poor soldering in the case of unsuitable conditions. Unsold solder defects can be observed.

14 shows an example of the shape of the iron tip of the present invention.

Fig. 14 (a) shows an example of the width of the iron tip. That is, the soldering state is described for a case in which the width of the iron tip 3 to be soldered is equal to, greater than, or smaller than the width of the pattern to be soldered (here, a bus bar pattern as an example), and the width of the iron tip (larger, the same) , smaller) and the soldering state is described as follows.

(In the above, meandering is a snake-like shape.)

As described above, the best result is obtained when the width of the iron tip (width in the direction perpendicular to the soldering direction) is the same as the width of the pattern to be soldered, and it is found that good results cannot be obtained if it is too wide or too narrow than that. became

Fig. 14(b) shows an experimental example. That is, the conditions and results of the experiment are as follows.

· The width of the iron tip was matched to the width of the busbar pattern on the surface. That is, for example, as shown in the example of the shape of the iron tip of the present invention shown in FIG. 7B , the width of the iron tip of the present invention is matched to the width of 1 mm of the bus bar pattern to be soldered.

· The length of the iron tip depends on the unevenness (bending) of the processing shape of the wafer surface. That is, since the length of the iron tip is a relation in which the molten solder at the tip of the iron tip is adhered to the part to be soldered (pattern on the wafer, for example, bus bar pattern, etc.) It is necessary to match the period (for example, one period) of the unevenness), which means that it depends on the bending (irregularity) of the wafer.

- In this experimental example, since the unevenness|corrugation (curvature) of the processed shape of the wafer in a present state falls within 4 mm, it was set as 4 mm. That is, since one cycle of unevenness (bending) of the processing shape of the wafer used in the experiment fell within 4 mm, the length of the iron tip shape example of the present invention shown in FIG.

As described above, the width and length of the iron tip are determined (adjusted) in accordance with the width (width of the pattern) of the part to be soldered and the unevenness (bentness) of the processing shape of the wafer surface to be soldered, as well as thermal resistance and ultrasonic resistance. The shape of the iron tip was determined (adjusted) so that it was small and the heat capacity was large. As a result, as described above, in the present invention, a solder layer having a thickness of half or a third of that of the prior art and a uniform solder layer is strongly soldered to the aluminum surface and silicon surface of the solar cell substrate, and the heating temperature of the iron tip is lowered. It was possible to reduce the thermal damage and ultrasonic damage of the soldering surface of the solar cell substrate by reducing the ultrasonic output.

Fig. 15 shows a process explanatory diagram of the ABS coating of the present invention.

Fig. 15 (a) schematically shows the state of the titanium (TA) treatment.

In Fig. 15(a), a substrate 11 is a substrate (material) of an iron tip of an ultrasonic soldering iron, and is, for example, titanium metal (titanium alloy). The base material 11 is not limited to titanium metal, and may be any metal as long as it has good thermal conductivity, is hard, and has abrasion resistance (to be described later in FIG. 17 and the like). In addition, from the viewpoint of forming a high-hardness, abrasion-resistant film on the substrate 11 by ion sputtering, it is necessary to have high adhesion or alloying properties.

The TA mixed layer 12 is a mixed layer formed from the surface of the base 11 to the inside by colliding titanium ions here by ion sputtering from the base 11 , as shown. As shown in the figure, the thickness of the TA mixed layer 12 is usually about 5 to 10 μm.

The TA film 13 is a titanium film (TA film) formed on the base material 11 as shown when titanium ions are collided here by ion sputtering from the base material 11 . As shown in the figure, the thickness of the TA film 13 is usually about 5 to 10 µm. If necessary, it becomes thin by grinding a little from above, but may be flattened to improve planarity. Therefore, in the experiment, ion sputtering (ABS coating) was performed with a pulse of 50 Hz, a maximum voltage of 220 V, and a current of 42 A (normal mode), whereby an unevenness of 10 µm or more was obtained. A 10×10 mm ² area was treated for 13 minutes.

The original substrate surface 14 is the surface of the substrate 11 before ion sputtering.

When ion sputtering of titanium (or titanium alloy) is performed on the substrate 11 as described above, the TA mixed layer 12 is formed from the surface of the substrate 11 to the inside and is firmly fixed, and TA on the substrate 11 The coating film 13 is formed, so that it is possible to manufacture a high hardness and wear resistance iron tip provided by the TA coating film 13 . The TA film 13 can also improve sliding by slightly grinding the surface as needed to make it flat.

Fig. 15(b) schematically shows the state of the silicon (SA) treatment.

In Fig. 15(b), a substrate 21 is a substrate (material) of an iron tip of an ultrasonic soldering iron, and is, for example, silicon metal (silicon alloy). The base material 21 is not limited to silicon metal, and may be any metal as long as it has good thermal conductivity, is hard and has abrasion resistance (described later in Fig. 17 and the like). In addition, from the viewpoint of forming a film of high hardness and wear resistance on the substrate 21 by ion sputtering, it is necessary to have high adhesion or alloying properties.

The SA mixed layer 22 is a mixed layer formed inside from the surface of the substrate 21 by ion sputtering from on the substrate 21 by making silicon ions collide here, as illustrated. As shown in the figure, the thickness of the SA mixed layer 22 is usually about 5 to 10 μm.

The SA film 23 is a silicon film (SA film) formed on the substrate 21 when silicon ions are collided here by ion sputtering from the substrate 21 , as illustrated. As shown in the figure, the thickness of the SA film 23 is usually about 5 to 10 µm. If necessary, it becomes thin by grinding a little from above, but may be flattened to improve planarity.

The original substrate surface 24 is the surface of the substrate 21 before ion sputtering.

When ion sputtering of silicon (or silicon alloy) is performed on the substrate 21 as described above, the SA mixed layer 22 is formed from the surface of the substrate 21 to the inside and is firmly fixed and on the substrate 21 . The SA coating 23 is formed, so that it is possible to manufacture a high-hardness and wear-resistant iron tip provided with the SA coating 23 . It is also possible to improve the slippage of the SA film 23 by slightly polishing the surface as necessary to make it flat.

Fig. 16 shows an explanatory diagram (hardness) of the ABS coating of the present invention. Fig. 16 shows an example of the film hardness (HV: Vickers hardness) of the TA treatment of Fig. 15 (a), which has already been described.

In Fig. 16, the column on the left shows the case of three states: the TA treatment of Fig. 15 (a), the grinding processing up to the original substrate surface 14, and the 5 μm grinding processing from the original substrate surface, which have already been described. The column of is an example of film hardness (HV), and here, the example in which the base material 11 is an Fe-based base material is shown, and it is equipped with the following hardness.

Here, the film hardness of 2500 HV on the TA surface is about 2500 HV as it is after the TA treatment in Fig. means to be That is, the hardness of the stainless steel (SUS304) of the iron tip of the conventional ultrasonic soldering iron is 150HV (refer to FIG. 17 to be described later), which means that the hardness is 16 times harder (abrasion resistance is approximately the same).

Similarly, 2000 HV of grinding to the original substrate surface means that the film hardness when grinding to the original substrate surface 14 in the state after the TA treatment in Fig. 15(a) is about 2000 HV. That is, it means that the hardness of the stainless steel (SUS304) of the iron tip in the conventional ultrasonic soldering iron is 150 HV (refer to FIG. 17 to be described later), which is about 13 times harder (the abrasion resistance is approximately the same).

Similarly, 1000 HV of 5 μm grinding on the original substrate surface means that the film hardness when 5 μm grinding on the original substrate surface is about 1000 HV in the state after the TA treatment in Fig. 15(a). That is, it means that the hardness of the stainless steel (SUS304) of the iron tip in the conventional ultrasonic soldering iron is 150HV (refer to FIG. 17 to be described later), which is about 6 times harder (the abrasion resistance is approximately the same).

17 shows an application example of the ABS coating of the present invention to a soldering iron. Fig. 17 shows the relationship between hardness (HV), specific heat (J/KgK), and thermal conductivity (W/mK) of the TA film of Fig. 15 (a) and the SA film of Fig. 15 (b), which have already been described. will be.

In Fig. 17, the column on the left shows the TA film of Fig. 15 (a), the SA film of Fig. 15 (b), and other materials, which have already been described, and the column on the right shows the hardness, specific heat, and thermal conductivity values. Examples of , each having the following hardness, specific heat, and thermal conductivity.

Here, molybdenum, chromium-molybdenum steel, SUS304, etc. were conventionally used for the film/material of the iron tip in the left column, and the hardness was within the range of 147 to 415 HV (several hundreds of HV) (“( 1) See “Original Hardness (Hundreds of HV)”).

When the TA film of Fig. 15 (a) of the present invention is formed on the surface of such a conventional iron tip (molybdenum, chromium molybdenum steel, SUS304), the hardness of the TA film is increased by about 6 times to 2500 HV (“ (2) Hardness after treatment (2500 HV)") was found, and it was found that the abrasion resistance was also substantially similarly increased.

Similarly, as shown on the right side of Fig. 17,

It was found that it increased from "(3) original thermal conductivity (16.3 of SUS304)" to "(4) thermal conductivity after change (147 of molybdenum)".

That is, by changing the base material of the iron tip from the conventional "SUS304" to the "molybdenum" of the present invention, the thermal conductivity was increased by about 9 times, and the surface hardness was increased by about 6 times by forming a TA film on the surface.

Here, by changing the base material of the iron tip from SUS304 to molybdenum, thermal properties, particularly thermal conductivity, to the silicon substrate were significantly improved, and the frequency of replacement of the iron tip could be increased by about 6 months. However, since the hardness is small, the frequency of replacement of the iron tip is about 6 months. In addition, by increasing the hardness by performing TA treatment (TA coating) on molybdenum, the base material of the iron tip (refer to FIG.

18 shows an example of a surface micrograph (molybdenum) of the ABS coating of the present invention. In the experiment, the ABS coating shown in Fig. 18 was performed with a pulse of 50 Hz, a maximum voltage of 220 V, and a current of 14 A (mild mode), whereby the unevenness of about 5 μm was obtained. A 10×10 mm ² area was treated for 40 minutes.

Fig. 18(a) shows a photomicrograph of the molybdenum surface (substrate), and Fig. 18(b) shows a photomicrograph of the TA surface (titanium coating). Both images are images whose magnification increases in the order of 5, 10, 20, and 50 times from the top.

In the molybdenum surface (substrate) of Fig. 18(a), as shown in the figure, it is possible to observe after machining in the transverse direction.

In the TA surface (titanium coating) of FIG. 18(b), it is revealed that titanium is formed in an island shape by titanium ion sputtering on the surface of molybdenum, which is the iron tip base material. This TA surface has island-like irregularities on the surface as schematically shown in FIG. It is possible to flatten the surface by performing 5 μm grinding on the surface of the substrate. In addition, as the hardness decreases from 2500 to 1000 HV as shown in Fig. 16, as the polishing increases, it is necessary to perform polishing to obtain optimum flatness according to use.

In the SA surface (silicon coating) in Fig. 18C, it is found that silicon is formed in an island shape by silicon ion sputtering on the surface of molybdenum, which is the iron tip base material. This SA surface has island-like irregularities on the surface as schematically shown in FIG. It is possible to flatten the surface by performing 5 μm grinding on the surface of the substrate. In addition, since the hardness decreases as the polishing increases, as in the case of the TA film, it is necessary to perform polishing to obtain optimum flatness according to use.

Figure 19 shows the surface micrograph Example 2 of the ABS coating of the present invention. That is, a stereoscopic microscope at 4 times in each of Mo (molybdenum) in Fig. 18 (a), TA (titanium coating) in Fig. 18 (b), and SA (silicon coating) in Fig. 18 (c), which have already been described. is a picture example of

Next, the procedure for directly ultrasonically soldering a ribbon or a wire (wire), which is a lead wire to which solder is attached, to a substrate or a film formed on the substrate will be described in detail with reference to Figs.

Fig. 20 shows a flowchart (without pre-soldering) for explaining the operation of the present invention.

In Fig. 20, in S101, the temperature of the soldering iron, the wafer mounting table, and the like, the ultrasonic oscillation frequency, and the like are set. That is, before ultrasonic soldering, the following are performed as preparatory steps.

· Soldering iron: Heat to a predetermined temperature (heat to a temperature at which the solder attached to the ribbon or wire is melted).

· Wafer mounting table: Preheat the mounting table of the wafer, which is the substrate, to a predetermined temperature (a temperature slightly lower than the temperature at which the solder attached to the ribbon or wire is melted, for example, 180°C (to be described later)).

· Ultrasonic oscillation frequency, etc.: Adjust so that ultrasonic waves of a predetermined frequency and a predetermined output are supplied from the soldering iron tip to the wafer, which is the substrate.

In S102, the wafer is set at a predetermined position. That is, a wafer of, for example, a solar cell to be ultrasonically soldered to a ribbon or wire is transferred and fixed by an automatic machine (not shown) to a predetermined position on a wafer mounting table heated to a predetermined temperature in S101. When fixed, it is preheated to a predetermined temperature (eg 180° C.) in a very short time.

In S103, the solder-attached wire or ribbon is sent out. That is, in S102, a wire (wire rod) or ribbon previously soldered to a predetermined position (a substrate to be ultrasonically soldered or a film on a substrate to be ultrasonically soldered) of the preheated wafer fixed at a predetermined position on the wafer mounting table is placed in an automatic machine (not shown). not) sent by The wire (wire rod) or ribbon is sent out from a reel or is sent out from a mounting box in which a plurality of wires or ribbons cut to a predetermined length are accommodated. In addition, in particular, since the wire sometimes breaks due to torsion while it is being sent from the reel, it is preferable to send the wire (wire rod) cut to a predetermined length from the loading box by an automatic machine. In the case of the ribbon, that's not the case.

In S104, ultrasonic soldering is performed. That is, in the state in which the wafer is fixed to the wafer mounting table in S102 and preheated to a predetermined temperature (for example, 180° C.), and the wire (wire rod) or ribbon to which the solder is attached in S103 is formed on the wafer or on the wafer. In the state of being supplied (or placed) on a film (aluminum film, nitride film, glass film, etc.), the wire (wire rod) or ribbon The solder adhering thereto is melted, and the wire or ribbon and the wafer (substrate) or the film formed on the wafer (film on the substrate) are ultrasonically soldered.

In S105, it is determined whether there is a processing wafer. In the case of YES, since there is still a processing wafer, the following wafer processing (processes S102 to S104) is repeated in S106. In the case of NO, the processing of all wafers has been completed, and thus the process is completed.

As a result, it is possible to melt the solder previously attached to the wire (wire) or ribbon, and then directly ultrasonically solder to the preheated wafer (substrate) or the film (film on the substrate) formed on the wafer. Accordingly, there are the following advantages over the case of ultrasonically soldering the previously described wire or ribbon to which no solder is attached to a substrate or a film on the substrate.

1. In this example, since solder is attached to the wire or ribbon, an automatic solder feeding device, preheating device, etc. are unnecessary.

2. Compared with the case where solder is pre-soldered to a substrate or a film on the substrate and then a wire or ribbon is soldered, the pre-soldering step is unnecessary.

Fig. 21 shows a ribbon connection example of the present invention. That is, an example in which a ribbon to which solder is attached is directly ultrasonically soldered to a wafer (for example, a solar cell substrate) or a film on the wafer according to the flowchart of FIG. .

Fig. 21 (a) shows an example of connection to the finger surface, Fig. 21 (b) shows an example of connection to the silicon surface, and Fig. 21 (c) shows an example of connection to the rear aluminum surface.

Fig. 21 (a) shows an example of connection to the finger surface. Fig. 21 (a-1) shows an example in which a ribbon is ultrasonically soldered to a finger surface, and Fig. 21 (a-2) shows a view when viewed from the horizontal direction.

The ribbon (ribbon to which solder is attached) shown in Fig. 21(a) is ultrasonically soldered directly to the finger surface formed on the silicon substrate according to the flowchart of Fig. 20, and the ribbon is electrically connected to the finger surface (finger electrode). An example in which the ribbon is mechanically and securely connected (fixed) to a film (a nitride film or a glass film formed on the nitride film) is shown.

Fig. 21B shows an example of connection to the silicon surface (substrate). Fig. 21 (b-1) shows an example in which a ribbon is ultrasonically soldered to a silicon surface, and Fig. 21 (b-2) shows a view when viewed from the horizontal direction.

The ribbon (ribbon to which solder is attached) shown in Fig. 21(b) is directly ultrasonically soldered onto a silicon substrate according to the flowchart of Fig. 20, the ribbon is electrically connected to the silicon surface (substrate), and the An example in which the ribbon is mechanically and firmly connected (fixed) to the silicon surface (substrate) is shown.

Fig. 21(c) shows an example of connection to the rear aluminum surface. Fig. 21 (c-1) shows an example in which the ribbon is ultrasonically soldered to the aluminum surface of the back surface, and Fig. 21 (c-2) shows a view when viewed from the horizontal direction.

The ribbon (ribbon to which solder is attached) shown in Fig. 21(c) is ultrasonically soldered directly to the aluminum surface of the back surface of the silicon substrate according to the flowchart in Fig. 20, and the ribbon is electrically connected to the aluminum surface on the back surface. Moreover, the example in which the said ribbon was connected (fixed) mechanically and firmly to the back aluminum surface is shown.

Fig. 22 shows a wire connection example of the present invention. That is, in accordance with the flow chart of Fig. 20 described above, a wire (wire) to which solder is attached is directly ultrasonically soldered to a wafer (eg, a solar cell substrate) or a film on the wafer, and the wire is electrically and mechanically firmly connected. shows an example.

Fig. 22(a) shows an example of connection to the finger surface, Fig. 22(b) shows an example of connection to the silicon surface, and Fig. 22(c) shows an example of connection to the rear aluminum surface.

Fig. 22(a) shows an example of connection to the finger surface. Fig. 22 (a-1) shows an example in which a wire is ultrasonically soldered to a finger surface, and Fig. 22 (a-2) shows a view when viewed from the horizontal direction.

The wire (wire attached with solder) shown in Fig. 22(a) is ultrasonically soldered directly to the finger surface formed on the silicon substrate according to the flowchart in Fig. 20, and the wire is electrically connected to the finger surface (finger electrode). An example in which the wire is mechanically and securely connected (fixed) to a film (a nitride film or a glass film formed on the nitride film) is shown.

22B shows an example of connection to a silicon surface (substrate). Fig. 22 (b-1) shows an example in which a wire is ultrasonically soldered to a silicon surface, and Fig. 22 (b-2) shows a view when viewed from the horizontal direction.

The wire (wire to which solder is attached) shown in Fig. 22(b) is directly ultrasonically soldered on the silicon substrate according to the flowchart of Fig. 20, and the wire is electrically connected to the silicon surface (substrate), and the An example in which a wire is mechanically and firmly connected (fixed) to a silicon surface (substrate) is shown.

Fig. 22(c) shows an example of connection to the rear aluminum surface. Fig. 22 (c-1) shows an example in which a wire is ultrasonically soldered to the aluminum surface of the back surface, and Fig. 22 (c-2) shows a view when viewed from the horizontal direction.

The wire shown in Fig. 22(c) (the wire to which the solder is attached) is directly ultrasonically soldered to the aluminum surface of the back surface of the silicon substrate according to the flowchart in Fig. 20, and the wire is electrically connected to the aluminum surface of the back surface. Moreover, the example in which the said wire was mechanically and firmly connected (fixed) to the back aluminum surface is shown.

23 shows an example of soldering conditions of the present invention. That is, an example of the soldering conditions used in ultrasonic soldering in FIG. 20, FIG. 21, and FIG. 22 already described is shown. As shown in the figure, the sample, ultrasonic output, ultrasonic frequency, iron temperature, and stage temperature (wafer loading table temperature) were as follows.

Fig. 24 shows the soldering conditions and soldering success examples of the wire of the present invention.

24(a) shows an example of the number of successes/total number. Here, as the cross-sectional shape of the wire, examples of the number of successes when tested for 0.5 mm phi, 0.4 mm phi, 0.3 mm phi, and 0.2 mm phi are shown as shown, and the following results shown in the drawings were obtained.

Here, (a-1) "solder coating with a thickness of about 10 μm" refers to a wire (copper wire) with solder having a thickness of about 10 μm attached (attached by solder coating). (a-2) The "distorted shape of the wire" is a slightly crushed o-shaped wire of a "solder coating with a thickness of about 10 μm" as described in FIG. 24 (b) to be described later. (a-3) "Pre-soldering, copper wire ○ shape" is pre-soldered on a substrate, and a copper wire ○ shaped wire is ultrasonically brazed thereto.

As described above, the results of ultrasonic soldering to a substrate (wafer) were tested according to the flow chart of FIG. lost.

(1) Ultrasonic soldering was difficult for the wire in the (circle) shape of (a-1), but ultrasonic soldering was possible in all other cases (electrical and mechanical connection became good).

(2) 0.5mmφ wire (a wire with solder attached to the surface of a 0.5mmφ copper wire) is too hard, and when ultrasonic soldering is performed on the wafer, the wafer may crack or peel off, making handling difficult . In order to use the wire, it is necessary to soften it by annealing or the like.

(3) As shown in (a-3), it was found that ultrasonic soldering to the substrate was possible even with a copper wire ○-shaped wire by pre-soldering (ultrasonic pre-soldering) to the substrate in advance.

Fig. 24(b) shows an explanatory view of the crushed wire. That is, an explanatory view of "(a-2) distorted shape of the wire" in Fig. 24(a) described above is shown.

Fig. 24 (b-1) shows an example of a copper wire ?-shaped wire, and Fig. 24 (b-2) shows an example of a distorted shape.

In Fig. 24 (b-2), the copper wire (circle)-shaped wire of Fig. 24 (b-1) is slightly crushed up and down in the radial direction as shown in the figure here, so that the portion in contact with the substrate below is If it is about 100 to 200 µm or more, it has been found through experiments that stable soldering is possible (ultrasonic soldering according to the flowchart of FIG. 20 is possible).

Fig. 25 shows an explanatory diagram (with or without presoldering, with or without solder supply, etc.) of ultrasonic soldering according to the present invention. Here, the vertical axis represents the distinction between the presence or absence of pre-soldering. That is, there is a distinction between a wire or a ribbon being pre-soldered to a portion of a substrate to be ultrasonically soldered (eg, a wafer or a film formed on a surface of the wafer) in advance, and in a case in which it is not pre-soldered.

In addition, the horizontal axis represents the distinction between the presence or absence of solder adhesion to the wire or ribbon. That is, if the surface of the wire or ribbon is soldered (or coated with solder) in advance, it is present, if it is not soldered, it is not.

In Fig. 25, the following experimental results shown in the drawings were obtained when ultrasonic soldering was performed according to the flow chart of Fig. 20 already described for the combination of the presence or absence of pre-soldering and the presence or absence of solder adhesion of wires or ribbons.

In detail here, the following results were obtained for the four combinations (1), (2), (3), and (4).

(1) In the case of “pre-solder oil” or “solder attachment oil for wire or ribbon”,

1. Stable work

2. Soldering is possible even with a ○-shaped wire

result was obtained. That is, it is an experimental result in the case of ultrasonically soldering a wire or ribbon to which a solder is attached to a portion pre-soldered by ultrasonic soldering on a substrate (wafer) or a film formed on the substrate to be ultrasonically soldered with a wire or ribbon. A stable operation was possible, and even with a ○-shaped wire, soldering was possible (electrically connected and mechanically firmly connected).

(2) In the case of “No pre-soldering” or “With solder attached to wires or ribbons”,

1. ○ Wires or ribbons with distorted shapes are closely adhered

2. The adhesion of the ○shaped wire is unstable.

3. There is a problem with the adhesion of the place where the attached solder has peeled off.

was obtained. That is, it is an experimental result in the case of ultrasonically soldering a wire or ribbon to which a solder is attached to a portion of a substrate (wafer) or a film formed on the substrate to which the wire or ribbon is to be ultrasonically soldered to a portion where there is no preliminary soldering by ultrasonic soldering. The result was obtained that the wire or ribbon with the shape of ○ had good adhesion, the adhesion of the wire with the shape of ○ was unstable, and that there was a problem in adhesion at the place where the attached solder was peeled off.

(3) In the case of “Pre-soldering oil” or “No soldering of wires or ribbons”,

1. A result was obtained that the solder material may not adhere uniformly depending on the method of heat transfer. That is, it is an experimental result in the case of ultrasonically soldering a wire or ribbon without solder adhesion to a portion pre-soldered by ultrasonic soldering to a substrate (wafer) or a film formed on the substrate to be ultrasonically soldered with a wire or ribbon. A result was obtained that the solder material did not adhere uniformly depending on the method of heat transfer. In other words, since solder is not attached to the wire or ribbon, the part of the board to be soldered is pre-soldered, and ultrasonic soldering is performed while lightly pressing with the soldering iron tip from the top of the wire or ribbon, the soldering iron tip, wire or ribbon, reserve on the board In the path of heat transfer to the soldering part, there was a case where consistent and clean soldering could not be achieved depending on the method of heat transfer. That is, it can be solved by soldering it to a wire or ribbon.

(4) In the case of “No pre-soldering” or “No soldering of wires or ribbons”,

1. Requires solder supply

2. In addition to the supply of wire or ribbon, the supply of solder is unstable.

3. It is difficult to supply a uniform solder material

was obtained. That is, since there is no preliminary soldering for the wire or ribbon and the portion of the board to be soldered, it is necessary to simultaneously supply the wire or ribbon and solder. Therefore, it is necessary to supply solder, and the result is that the supply operation of both the supply of the wire or ribbon and the supply of the solder is unstable, and it is difficult to supply the solder material uniformly.

1: Substrate (solar cell substrate, silicon substrate)
2: Substrate loading stand (substrate pre-heating stand)
3: Iron tip
31: iron tip temperature (T3)
32: iron tip moving device (S1)
4: Iron tip heating device
5: Ultrasonic oscillator
6: Solder
7: Solder preheating device (T2)
8: Solder slide device (S2)
11, 21: description
12: TA mixed layer
13: TA film
14: original substrate surface
22: SA mixed layer
23: SA film
24: original substrate surface

Claims (16)

In an ultrasonic soldering apparatus for soldering to a substrate or a portion of a film formed on the substrate,
A substrate preheating device for preheating a substrate to be soldered or a substrate on which a film is formed to a predetermined temperature lower than a melting temperature of solder;
An iron tip heating device that adjusts a soldering iron tip portion close to a portion of the substrate having a predetermined temperature preheated by the substrate preheating device to a predetermined temperature at which the solder supplied with ultrasonic waves is melted. )Wow,
an ultrasonic oscillator for supplying the ultrasonic wave to the iron tip portion heated by the iron tip heating device;
a solder preheating device for preheating the thread-shaped solder supplied to the iron tip to a temperature lower than a temperature at which the thread-shaped solder is dissolved;
a solder slide device for adjusting the speed at which the thread-shaped solder preheated by the solder preheating device is supplied to the heated iron tip portion;
An iron tip moving device that moves the iron tip in the soldering direction at a predetermined speed while supplying the pre-heated thread-like solder by the solder slide device to the heated iron tip close to the substrate at a predetermined speed cast
provided,
An ultrasonic soldering apparatus, characterized in that preheated thread-like solder is dissolved by an iron tip portion, and ultrasonic waves are applied to remove adhesions on adjacent substrate portions, and the molten solder is attached to the substrate portion for soldering.
According to claim 1,
In the shape of the iron tip portion, the length in the moving direction of the iron tip is longer than the width in the moving direction of the iron tip, thereby increasing the cross-sectional area and heat capacity, thereby improving heat conduction to the substrate and lowering the temperature of the iron tip, An ultrasonic soldering apparatus for reducing thermal damage to a film on a substrate or to a film in the substrate.
3. The method of claim 1 or 2,
In the shape of the iron tip portion, the length in the moving direction of the iron tip is longer than the width in the moving direction of the iron tip, thereby increasing the cross-sectional area to improve heat conduction of the ultrasonic waves to the substrate and to improve the removal of attachments. An ultrasonic soldering apparatus characterized by reducing an oscillation output to reduce ultrasonic damage to a film on a substrate or a film in the substrate.
4. The method of claim 3,
An ultrasonic soldering apparatus characterized in that the ultrasonic oscillation output is 2W to 6W, preferably 2W.
5. The method according to any one of claims 1 to 4,
In the shape of the iron tip portion, the length in the moving direction of the iron tip is 3 to 6 times the width in the moving direction of the iron tip, and the solder having a uniform thickness according to the cycle of the bending length in the moving direction of the iron tip on the board Ultrasonic soldering apparatus, characterized in that to form a layer.
6. The method according to any one of claims 1 to 5,
The ultrasonic soldering apparatus according to claim 1, wherein the thickness of the solder to the substrate can be adjusted as thin as possible by increasing or decreasing the cross-sectional area of the preheated thread-like solder.
7. The method according to any one of claims 1 to 6,
Ultrasonic soldering apparatus, characterized in that the supply speed of the preheated thread-like solder and the moving speed of the iron tip are the same.
8. The method according to any one of claims 1 to 7,
In the supply speed of the preheated thread-like solder and the moving speed of the iron tip, the former is made faster than the latter to increase the amount of molten solder to increase the thickness of the solder to the substrate, or An ultrasonic soldering apparatus characterized in that it is made slower than the latter to reduce the amount of molten solder, thereby reducing the thickness of the solder to the substrate, so that the thickness of the solder can be adjusted as thin as possible.
9. The method according to any one of claims 1 to 8,
An ultrasonic soldering apparatus, characterized in that a uniform and thin solder layer is formed by setting the moving speed of the iron tip to 150 mm/s to 200 mm/s.
10. The method according to any one of claims 1 to 9,
Ultrasonic soldering apparatus, characterized in that the material of the iron tip or the material for coating the iron tip is made of a material of high hardness and wear resistance.
11. The method of claim 10.
Ultrasonic soldering apparatus, characterized in that the material is any one of titanium, titanium alloy, silicon or silicon alloy.
12. The method of claim 10 or 11,
The ultrasonic soldering device, characterized in that the coating thickness of the iron tip is 5 ~ 15㎛.
According to claim 1,
Instead of the solder preheating device, the solder slide device, and the iron tip moving device, a ribbon or wire, which is a lead wire that is pre-solder attached and draws a current to the outside, is placed on the substrate or a portion of the film formed on the substrate, the iron tip portion and an iron tip moving device for moving the iron tip in the soldering direction at a predetermined speed while pressing
An ultrasonic soldering apparatus characterized in that solder previously attached to a ribbon or wire is dissolved by an iron tip portion, and ultrasonic waves are applied to remove adhesions on adjacent substrate portions, and the molten solder is attached to the substrate portion for soldering.
14. The method of claim 13,
The wire rod is an ultrasonic soldering device, characterized in that the circular-shaped wire rod is slightly crushed.
An ultrasonic soldering method for soldering a substrate or a portion of a film formed on the substrate, the method comprising:
a substrate preheating device for preheating the substrate to be soldered or the substrate on which the film is formed to a predetermined temperature lower than the melting temperature of the solder;
an iron tip heating device for adjusting a soldering iron tip portion close to a portion of the substrate having a predetermined temperature preheated by the substrate preheating device to a predetermined temperature at which the solder supplied in a state of applying ultrasonic waves is melted;
an ultrasonic oscillator for supplying the ultrasonic wave to the iron tip portion heated by the iron tip heating device;
a solder preheating device for preheating the thread-shaped solder supplied to the iron tip to a temperature lower than a temperature at which the thread-shaped solder is dissolved;
a solder slide device for adjusting a speed at which the thread-shaped solder preheated by the solder preheating device is supplied to the heated iron tip portion;
an iron tip moving device that moves the iron tip in a soldering direction at a predetermined speed while supplying the pre-heated thread-like solder by the solder slide device to the heated iron tip close to the substrate at a predetermined speed;
install,
An ultrasonic soldering method, characterized in that the preheated thread-like solder is melted by an iron tip portion, and ultrasonic waves are applied to remove the adhesion of the adjacent substrate portion, and the molten solder is attached to the substrate portion for soldering.
16. The method of claim 15,
Instead of the solder preheating device, the solder slide device, and the iron tip moving device, a ribbon or wire, which is a lead wire that is pre-solder attached and draws current to the outside, is pressed against the substrate or a portion of the film formed on the substrate with the iron tip portion, Installing an iron tip moving device that moves the iron tip in the soldering direction at a predetermined speed,
An ultrasonic soldering method characterized in that solder previously attached to a ribbon or wire is melted by an iron tip part, and ultrasonic waves are applied to remove the adhesion on the adjacent substrate, and the molten solder is attached to the substrate for soldering.

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