KR20210147401A - Dry removal method for contaminants - Google Patents

Abstract

An embodiment of the present invention relates to a dry type removal method for contaminants is a dry type removal method for contaminants for removing contaminants formed on one end of a battery in which a positive electrode cap portion and a negative electrode portion are located by using a laser. According to the present invention, the contaminants are removed by irradiating the laser toward one end of the battery, wherein the laser may be independently irradiated to each region by dividing the positive electrode cap region and the negative electrode region.

Description

DRY REMOVAL METHOD FOR CONTAMINANTS

The present invention relates to a method for dry removal of contaminants for removing contaminants formed on a substrate using a laser.

The battery may be classified into a non-rechargeable primary battery and a rechargeable secondary battery.

Among them, secondary batteries were mainly used in portable information devices such as laptops, camcorders, and mobile phones in the past, or small products such as electric appliances, but with recent technological development, their use has expanded as a rechargeable power source required to drive a motor of an electric vehicle. have.

A secondary battery used in an electric vehicle can be divided into a battery pack using a large pouch-type cell or a prismatic cell, and a battery pack using a cylindrical cell.

Since the cylindrical cell has a small capacity of the unit cell, it is necessary to use a relatively large number of unit cells, so there is a problem in that the number of holes in the welding process for electrical connection between cells increases, and the yield in the welding process becomes a problem.

Wire bonding is mainly used as a method for electrical connection of cylindrical cells, but there is a problem in that the quality of wire bonding is very sensitive to the surface state of the cylindrical cells.

For wire bonding, a wet cleaning process is generally used to remove contaminants from the cell surface to improve the cell surface condition. There can be problems with oxides being induced.

Even if there is no problem due to washing, the secondary battery is exposed to various physical and/or chemical contamination during manufacture and storage. Such contamination not only deteriorates the performance of the battery, but is also a factor in reducing the quality of the wire bonding process between unit cells required to form a large-capacity battery.

In addition, a plurality of single secondary battery cells are stored on a package after manufacturing. If contamination occurs while stored on the package, if a wet washing process is performed to remove contaminants, side effects of the wet washing process as described above can be further maximized.

Accordingly, it is necessary to introduce a dry removal method of contaminants that can remove contaminants formed on the substrate using a laser immediately before the wire bonding process for manufacturing the pack. In addition, it will also be necessary to derive laser conditions for wire bonding to be normally performed when applied to secondary battery cells.

The above-mentioned background art is technical information that the inventor possessed for the derivation of the embodiments of the present invention or acquired in the process of derivation, and it cannot be said that it is necessarily known technology disclosed to the general public prior to the filing of the embodiments of the present invention. none.

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a dry removal method of contaminants for removing contaminants formed on a substrate using a laser.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The dry removal method of contaminants according to one aspect of the present invention is a dry removal method of contaminants for removing contaminants formed on one end of a battery in which a positive electrode cap part and a negative electrode part are located using a laser, wherein the The contaminants are removed by irradiating a laser, but the anode cap region and the cathode region are divided and the laser is irradiated to each region independently.

In one embodiment of the present invention, the contaminants removed by the laser irradiation may include a battery electrolyte, an oxide film, or an organic material.

In one embodiment of the present invention, the wavelength of the laser may be 1000 to 1100 nm.

As an embodiment of the present invention, the energy density of the laser may be ^{10 to 100 kJ/m 2 .}

In one embodiment of the present invention, the peak output of the laser may be 3 ~ 30 MW/cm 2 .

In one embodiment of the present invention, the M ² value of the laser may be 2-50.

In one embodiment of the present invention, the pulse repetition rate per second of the laser may be 10 ~ 1000 kHz.

In one embodiment of the present invention, the pulse width of the laser may be 2 ~ 240 ns.

As an additional feature of the method for dry removal of contaminants according to one aspect of the present invention, a laser in which the anode cap region and the cathode region are separately irradiated may be used.

In one embodiment of the present invention, a plurality of the batteries are accommodated in a package with an open top, and after vision recognition is performed to distinguish each battery using a camera configured including a laser device and a coaxial optical system. , it is possible to independently irradiate the laser toward one end of each battery.

In this embodiment, it is preferable that the driving conditions of the laser irradiated to the anode cap region and the cathode region are different.

As an embodiment of the present invention, a mechanism for supplying an inert gas to the surfaces of the anode cap region and the cathode region during laser irradiation and a mechanism for sucking vapor phase byproducts generated by laser irradiation may be provided.

According to the dry removal method of contaminants according to one aspect of the present invention and an embodiment thereof, it is possible to induce normal wire bonding between substrates while facilitating removal of contaminants formed at one end of the battery.

1 is a diagram schematically illustrating one end of a cylindrical battery to which the dry removal method of contaminants according to an embodiment of the present invention can be applied.
2 is a diagram schematically illustrating one end of a battery in a planar shape.
3 is a photograph showing a state in which wire bonding is possible by irradiating a laser on the surface of an electrode contaminated with an organic material to remove the organic material.
4 is a photograph showing the result of selectively cleaning the anode region and the cathode region, and shows a state in which rust is removed by selecting only the cathode region in order to prevent damage to the gasket.
5 is a diagram schematically showing a ratio in which wire bonding is normally performed on the cathode part according to the energy density of the irradiated laser.
6 is a view showing an SEM photograph (500 magnification) of the cathode part according to the energy density of the irradiated laser.
7 is a diagram schematically illustrating a state in which a plurality of batteries are accommodated in a package.
8 is a graph showing a characteristic difference according ^{to M 2} , which is an index indicating a beam quality of a laser used in a method for dry removal of contaminants according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims. On the other hand, the terms used herein are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, "comprises" and/or "comprising" refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded. Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

1 is a diagram schematically showing one end of a cylindrical battery to which the dry removal method of contaminants according to an embodiment of the present invention can be applied, and FIG. 2 is a schematic plan view of one end of the battery.

One end 10 of the cylindrical battery has a positive electrode cap 11 disposed in the center, a negative electrode 12 disposed on the edge side, and a gasket 13 between the positive electrode cap 11 and the negative electrode 12 . are placed

In the method for dry removal of contaminants according to an embodiment of the present invention, a method for dry removal of contaminants by using a laser to remove contaminants formed on one end 10 of a battery in which the positive electrode cap portion 11 and the negative electrode portion 12 are located. As an example, the laser is irradiated toward one end 10 of the battery to remove contaminants, but the anode cap region (A) and the cathode region (B) can be divided to independently irradiate the laser to each region.

When the cylindrical battery is a lithium ion secondary battery, the positive electrode cap part 11 may be formed of, for example, aluminum (Al), an aluminum alloy, or an iron (Fe) plate material plated with nickel (Ni) on the surface, and the negative electrode part In (12), for example, an iron plate or stainless steel plate on which nickel is plated may be used, but the material is not limited thereto.

The gasket 13 disposed between the anode cap part 11 and the cathode part 12 is made of a PBT (Poly Butylene Terephthalate) or PP (PolyPropylene) material and can be easily damaged by a laser. It is necessary to separate the region and the cathode portion 12 so that the laser irradiation is performed independently so that the laser does not directly reach the gasket 13 .

When a plate of iron plated with nickel on the surface is used as the material of the negative electrode 12 , the negative electrode 12 is contaminated by the fluorine component in the _{electrolyte (LiPF 6 ) NiO X} , Ni(OH) ₂ Or Fe ₂ Oxides such as O ₃ may be formed. Such contamination of the electrode surface may occur during the manufacturing process or in the storage environment after production.

Meanwhile, these oxides and contaminants may be transferred to the anode cap 11 to form contaminants.

In an embodiment of the present invention, the contaminants formed in the anode cap portion 11 and the cathode portion 12 are divided into the anode cap region (A) and the cathode region (B) and independently irradiated with a laser to remove the contaminants. have it removed.

The wavelength of the laser may be selected from 300 to 2500 nm, more preferably from 500 to 1600 nm, very preferably from 1000 to 1100 nm. In this embodiment, a fiber pulse laser (wavelength: 1064 nm) typically used in the industry was used, and will be described based on this.

On the other hand, when the cylindrical battery is a secondary battery, wire bonding may be required between single cylindrical batteries to form a large-capacity secondary battery set. The surface roughness or the degree of oxide formation may be different, which may affect the wire bonding process.

Therefore, it is necessary to derive laser conditions in which wire bonding between cells can be normally performed.

3A shows a sample in which the surface of the anode part is intentionally contaminated with an organic material, and the wire bonding process cannot be performed on the contaminated surface.

In the case of organic contamination, since the contaminants are directly vaporized by a method called “Laser Ablation”, the wire bonding process can be normally performed as shown in FIG. .

Figure 4 (a) shows a sample in a state in which appearance defects and wire bonding became impossible due to rust generated in the negative electrode portion. Such surface contamination cannot be regenerated by the conventional wet cleaning method.

The surface of the state shown in Fig. 4(b) can be obtained by cleaning the cathode area by laser irradiation to prevent damage to the gasket, and through this, the appearance is good and the surface is normal in the wire bonding process. restored to a state in which it can be performed.

^{As an example of such laser cleaning, a multimode laser having an M 2} value of 10 or less was used to irradiate the laser with uniform energy to the cleaning area.

When the ^{value of M 2} is increased, the energy concentrated in the center of the beam focal point is uniformly distributed over a larger area. The graph of Figure 8 shows this characteristic.

When ^{a multimode laser having a high M 2} value is used, as shown in FIG. 8 , the effective energy area ratio required for contaminant removal within a beam spot size is wide, which is advantageous in terms of process performance.

In addition, it has an advantage in terms of forming a flat surface by maintaining the surface roughness at a low level due to the high uniformity of energy distribution within the beam focal size. The control of the M ² value is not essential because it is a condition experimentally confirmed by the material used in one embodiment of the present invention and the configuration of the related test, and may be selected and adjusted according to the purpose of the process.

When the laser wavelength is 1064 nm, the laser light absorptivity of aluminum used for the anode cap 11 in the cylindrical battery is about 4%, and the laser light absorptivity of the iron plate with nickel plating on the surface used for the cathode 12 . may be about 25-50%.

Since the absorption rate of the cathode part is relatively high compared to that of the anode, the temperature rise by laser irradiation is relatively fast. Equations 1 and 2 below represent the surface temperature rise caused by the laser irradiated to the surface of the material.

In Equations 1 and 2, T is the surface temperature, K is the thermal conductivity, ρ is the density, Cυ is the heat capacity, τ is the pulse width, I is the intensity.

According to the above equations, except for the intrinsic properties of the material, the intensity and the pulse width are variables that can be adjusted as laser process conditions.

As can be seen from Equation 2, the surface temperature is proportional to the square root of the pulse width and the intensity. If the surface temperature rises near the melting point by excessively increasing the laser intensity and pulse width, the flow of material on the surface occurs, increasing the surface irregularities and reactivity to form an oxide film, which greatly reduces the bonding strength in wire bonding. can

Therefore, in order to selectively remove contaminants within the range of minimizing damage that may occur to the material, it is important to select the conditions of the laser process required for cleaning.

Table 1 below summarizes the ratio of wire bonding to the anode cap part normally according to the energy density of the irradiated laser through an experiment, and FIG. 5 is a schematic view showing this.

In the ear bonding shown in Table 1, an aluminum wire with a diameter of 500 μm was commonly used for the anode and the cathode, and the Ÿ‡ wedge bonding method was used, and a 'Digital K&S wedge Bonder' was used as a bonding device. The test was performed in accordance with ASTM F459-13 'bond pull test'. Since the test equipment and test specifications are known, their description is omitted.

In this experiment, a plurality of samples were prepared in which contaminants were formed in the negative electrode part composed of an iron-based plate material plated with nickel on the surface. After immersing the upper end of the battery in an electrolyte diluted 10% with distilled water, the anode was dried and left at room temperature for several days. In an actual battery, there is a possibility that the surface of the upper end of the sample may be contaminated by a slight leakage of electrolyte during the sealing of the battery can, and this experiment is to implement such a situation.

After preparing a plurality of samples, dividing the prepared samples into several groups, irradiating a fiber pulse laser with different energy densities for each group, and then wire bonding to the corresponding cathode, the above-described bonding tensile test was performed.

In the bonding tensile test, it was determined that the weld was not broken and the wire was broken, and the ratio was calculated. When the laser energy density is 0, laser irradiation is not performed.

A case in which the wire was attached without falling off after attempting wire bonding on the anode cap part was regarded as normal wire bonding and the ratio was calculated. When the laser energy density is 0, it means that the sample is not irradiated with a laser.

Energy density of laser (kJ/m ² ) Normal wire bonding rate (%) 0 0 7.2 0 15.3 87.5 23.3 100 31.4 87.5 39.4 87.5 108.5 50

On the other hand, in the process of irradiating the laser to the anode cap portion or the cathode portion, an inert atmosphere is formed by supplying an inert gas such as _{nitrogen (N 2 ) or argon (Ar) to the surface to which the laser is irradiated.}

When the temperature of the metal surface constituting the anode cap portion or the cathode portion increases, the reactivity increases, so that oxide formation by contact with oxygen becomes active. Accordingly, a mechanism for blowing an inert gas through a nozzle to a surface on which a laser is irradiated or a process is performed inside a chamber filled with an inert gas is provided.

In addition, contaminants on the surface subjected to laser irradiation are vaporized to generate a fume including fine particles. These vapors may be adsorbed back to the surface of the substrate and act as contaminants and may harm the health of the operator.

Accordingly, a suction mechanism is provided around the surface of the substrate to which the laser is irradiated so as to remove by-products generated according to the laser process including the vapor.

The suction mechanism and the inert gas supply mechanism may be provided separately from each other or may be provided as a single unit.

Since such an inert gas supply mechanism and a suction mechanism are known per se, their construction and operation are not specifically described in this specification and are not shown in the drawings.

6 is a view showing an SEM photograph (30,000 magnification) of the cathode part according to the energy density of the irradiated laser.

6 (a), (b), (c), (d), (e), (f) shows that the laser energy density is in kJ/m ² units, 7.2, 15.3, 23.3, 31.4, 39.4, The case of 103.5 is shown.

If the energy density of the laser is 7.2 kJ / m ² is not performed normally, the bonding wire contaminants are not sufficiently removed, and if the energy density of the laser is 108.5 kJ / m ² has been transformed is plated nickel to the surface roughness ( It is estimated that the wire bonding is not normally performed because roughness is greatly increased and the oxide layer is thickened.

Through these results, when using a fiber pulse laser, it can be confirmed that the energy density of the laser for normal wire bonding while removing contaminants ^{is preferably 10 to 100 kJ/m 2 .}

Based on the range regarding the energy density of the laser, the peak power of the laser is 3 to 30 MW/cm ² , the M 2 value indicating the beam quality of the laser is 2 to 50, and the pulse repetition rate per second of the laser is 10 to 1000 kHz was found to be preferable.

7 is a diagram schematically illustrating a state in which a plurality of batteries are accommodated in a package.

A plurality of batteries 30 may be accommodated in the package P having an open top. The plurality of batteries 30 may be stored while being accommodated in the package P or delivered to a customer, and wire bonding may be performed while being accommodated in the package P as needed.

One end of the battery 30 may be contaminated during storage and delivery, and if each battery 30 has to be removed from the package P to undergo a contaminant removal process in order to remove the contaminants, the economic feasibility in terms of process cost and time is reduced. there is In addition, there is also a problem that re-contamination may occur in the process of accommodating the package P again after the contaminant removal process.

In this embodiment, after vision recognition so that each battery can be distinguished using a camera (not shown) configured including a laser device and a coaxial optical system, the laser is independently irradiated toward one end of each battery 30 desirable. Through this, it is possible to perform the contaminant removal process for all the cells 30 without separating and discharging each battery 30 from the package P.

In this embodiment, after vision recognition is performed by distinguishing the positive electrode cap portion 11 region and the negative electrode portion 12 region for each battery 30 using the above-described camera, the positive electrode cap portion 11 region and the negative electrode portion 12 It is preferable to vary the driving conditions of the laser irradiated to the area. Here, the driving condition of the laser means a condition corresponding to the irradiation condition of the laser irradiated to the anode cap portion 11 region and the irradiation condition of the laser irradiated to the cathode portion 12 region as described above.

According to an embodiment of the present invention, as shown in FIG. 2 , the anode cap region (A) and the cathode region (B) are distinguished and vision recognized through a camera, and each region (A, B) is distinguished and laser By irradiating the laser under different driving conditions, it is possible to remove contaminants and create a wire bonding environment optimized for each area, and also to prevent damage to the gasket (C).

Although the present invention has been described with reference to the above-mentioned preferred embodiments, various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, it is intended that the appended claims cover such modifications and variations as long as they fall within the gist of the present invention.

10: one end of the battery 11: positive electrode cap portion
12: negative electrode 13: gasket
30: battery A: positive electrode cap region
B: cathode region C: gasket
P: package

Claims (12)

A dry removal method of contaminants for removing contaminants formed on one end of a battery in which a positive electrode cap portion and a negative electrode portion are located using a laser, comprising:
Remove the contaminants by irradiating the laser toward one end of the battery,
The method for dry removal of contaminants by dividing the anode cap region and the cathode region to independently irradiate the laser to each region. According to claim 1,
The contaminants removed by the laser irradiation include a battery electrolyte, an oxide film, or an organic material, a dry removal method of contaminants. According to claim 1,
The wavelength of the laser is 1000 to 1100 nm, the dry removal method of the contaminants. According to claim 1,
The energy density of the laser is 10 ~ 100 kJ / m ² The dry removal method of the contaminants. According to claim 1,
The peak power of the laser is 3 to 30 MW/cm 2 of the method for dry removal of contaminants. According to claim 1,
The M ² value of the laser is 2 to 50, the dry removal method of the contaminants. According to claim 1,
The method of dry removal of contaminants, the pulse repetition rate per second of the laser is 10 ~ 1000 kHz. According to claim 1,
The pulse width of the laser will be 2 ~ 240 ns, the dry removal method of the contaminants. According to claim 1,
A method for dry removal of contaminants using a laser in which the anode cap region and the cathode region are separated and irradiated. According to claim 1,
A plurality of the batteries are accommodated in a package with an open top,
After vision recognition so that each cell can be distinguished using a camera including a laser device and a coaxial optical system, the laser is independently irradiated toward one end of each cell, dry removal method of contaminants . 11. The method of claim 10,
The dry removal method of contaminants by different driving conditions of the laser irradiated to the anode cap region and the cathode region. According to claim 1,
A method for dry removal of contaminants, wherein a mechanism for supplying an inert gas to the surfaces of the anode cap region and the cathode region during laser irradiation and a mechanism for sucking vapor phase by-products generated by laser irradiation are provided.

Images