JP2016207412A - Laser weldment and laser welding quality determination method for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser weldment and a laser welding quality determination method for a battery that enable the laser intensity applied to a battery exterior can processed portion to be checked based on grasp of the state of the processing trace of a test processed portion without observing the cross-section of a melt surface to determine welding quality.SOLUTION: A laser welding quality determination method for a battery is a welding quality determination method in a case where a current collector tab 12 of a battery is welded to a battery outer can 5. A first laser beam 23 having a spot diameter d smaller than the plate thickness h of the battery outer can is irradiated to form a welded portion 13. The battery outer can is irradiated with second and third laser beams having lower laser intensities than the first laser beam at the same time, and the shapes of first to third processing traces vary due to the difference in laser intensity to be irradiated, whereby the welding quality can be determined by only observing the appearance.SELECTED DRAWING: Figure 2A

Description

  The present invention relates to a laser welded article and a battery laser welding quality determination method. More specifically, the present invention relates to, for example, a joint structure between a battery outer can and a current collecting tab of a cylindrical battery and a method for determining whether or not the battery outer can and the current collecting tab are joined.

  In general, batteries can be broadly classified into primary batteries such as dry batteries or lithium batteries, and rechargeable secondary batteries such as nickel metal hydride batteries or lithium ion batteries. In addition, when classified by shape, there are a cylindrical shape, a square shape, a coin shape, and the like, and there are many types depending on the combinations. The structure of these main batteries was welded to a positive electrode and a negative electrode by inserting a power generation part composed of a positive electrode, a separator, and a negative electrode called an electrode body into a battery outer can made of metal such as iron or aluminum. A current collecting tab made of nickel or aluminum is welded to the battery outer can and the lid.

  In addition, a cylindrical battery centering on a personal computer has an electrode body in which a positive electrode plate and a negative electrode plate are wound in a spiral shape with a separator inserted into a cylindrical case, and a negative electrode lead welded to the negative electrode plate has A structure welded to the bottom of the case is common. And as a welding method, resistance welding is mainly used. The battery outer can or the current collecting tab tends to be thin in order to increase the volume of the electrode body for the purpose of increasing the battery capacity. Accordingly, a technique for stably welding the battery outer can and the current collecting tab is required.

  In recent years, in the resistance welding method, when the battery outer can and the current collecting tab are made thinner, there is a current control range for preventing the surface of the current collecting tab from being melted and obtaining a desired joint strength. Narrow. This is due to variations in the thickness of the battery outer can or current collecting tab, changes in the shape of the electrode rod, or the contact area between the battery outer can and current collecting tab. Became unstable, causing holes to be generated. In addition, scattering of the battery outer can material was also confirmed around the welded portion between the battery outer can and the current collecting tab, which also caused holes in the battery outer can.

  And in the conventional resistance welding, the sputter | spatter generate | occur | produced at the time of resistance welding entered the inside of a battery exterior can, and there existed a subject that the reliability of a battery deteriorated. Therefore, recently, the battery outer can and the current collecting tab are irradiated with a laser beam from the outside of the battery outer can to join the battery outer can and the current collecting tab to prevent spattering ( For example, see Patent Documents 1 to 3.)

  For example, FIG. 12 is a diagram showing a conventional sealed battery described in Patent Document 3 and a manufacturing method thereof.

  In FIG. 12, a current collecting tab 102 is in close contact with the bottom of the inner surface of the battery outer can 101. A laser beam 103 is irradiated from the outer bottom surface of the battery outer can 101 to melt the battery outer can 101 and the current collecting tab 102 to form a melting portion 104, and the battery outer can 101 and the current collecting tab 102 are joined. ing. Furthermore, since the melted portion 104 does not penetrate the current collecting tab 102 and the battery outer can 101 and the current collecting tab 102 are non-penetrated and joined, no spatter is mixed into the battery outer can 101. FIG. 13 further shows an enlarged detailed view of the melting part 104. However, for the sake of easy understanding, the figure is reversed so that the laser beam 103 is irradiated from above. The same elements as those in FIG. 12 are denoted by the same reference numerals, and the description thereof is omitted.

Japanese Patent No. 4175975 Japanese Patent No. 4547855 Japanese Patent No. 5306905

  However, in recent years, when the battery outer can and the current collecting tab are made thinner, the laser penetrates the thickness of the current collecting tab due to minute fluctuations in the laser intensity, or conversely, a predetermined depth of the current collecting tab portion. There has been a situation where the laser processing state and the processing result should be managed more strictly, such as no laser processing.

  In laser processing, even if the laser output at the processing point of the workpiece drops abnormally due to dirt, damage, or deterioration that occurs in any of the optical components in the laser beam path, the laser oscillator body grasps it. I can't do it. Therefore, as a method for confirming a welding defect due to laser processing, a destructive inspection such as an appearance inspection at a processing point after laser processing, a nondestructive inspection, or a peeling inspection by sampling has been used.

  The following methods are generally used as the laser intensity management method. However, it does not manage the machining state on the actual workpiece, but manages the state change up to the point before the machining point. There was a situation where the state at the actual machining point could not be managed.

As a general management method,
(1) Irradiation power monitoring inside the laser oscillator,
(2) There is power monitoring using light leakage at the laser head, and it is also used in actual mass production sites.

  In addition, as for grasping at the actual processing point, although it is a post-processing step, there is the above-mentioned appearance inspection method, mainly using a CCD camera or the like, the melting width and melting length of the laser processing part. There are also observations such as burning.

  In particular, as for grasping the laser intensity, it is often judged whether the processing surface is melted or not, the melting width is wide if the laser intensity is high, the melting width is narrow if the laser intensity is low, and the melting width is confirmed with a camera, It manages whether it is within the allowable range.

  However, in keyhole welding with a small laser beam diameter used in the present invention (described in detail later), even if the laser intensity changes, the melting depth changes, but the melting width hardly changes. Results are coming out. For this reason, conventionally, in the appearance inspection, it is impossible to determine whether the processed surface is melted or not. Therefore, in order to know the quality of the laser intensity irradiated to the processed surface, only the destructive test is used to check the laser intensity change. I couldn't.

  Therefore, it has been necessary to determine the change in the laser intensity, and thus the quality of the bonding strength, by a method other than the measurement of the work melt width conventionally used.

  Accordingly, an object of the present invention is to solve the above-mentioned problem, and to determine the quality of the joining strength without observing the cross section of the molten surface, and a laser welding quality determination method for laser welded articles and batteries. Is to provide.

To achieve the above object, a battery laser welding quality determination method according to one aspect of the present invention is a battery laser welding quality determination method in which a current collecting tab of a battery is welded to a battery outer can at a molten portion and joined. There,
Contacting the flat surface of the current collecting tab with the bottom surface of the inner surface of the battery outer can;
Irradiation that irradiates the outer bottom surface of the battery outer can with a first laser beam having a spot diameter smaller than the plate thickness of the battery outer can to form a first processing mark of the melted portion by the first laser beam. A process,
In the irradiation step, the first laser beam having the laser intensity for joining the battery outer can and the current collecting tab at the melting portion is irradiated to the outer bottom surface of the battery outer can, and at the same time, the first laser Irradiating the battery outer can simultaneously with irradiation of a second laser beam having a laser intensity lower than the laser intensity of the beam and irradiation of a third laser beam having a laser intensity lower than that of the second laser beam;
After the irradiation step, the method further includes a determination step of determining a bonding failure based on a shape of the second processing mark of the second laser beam and a shape of the third processing mark of the third laser beam.

  As described above, according to the laser welded article and battery laser welding quality determination method according to the aspect of the present invention, without observing the cross section of the melt surface, the laser intensity irradiated to the battery outer can processing portion, It can be confirmed by grasping the state of the machining mark, and the quality of welding can be judged. Therefore, it is possible to confirm the processing change at the time of laser welding by external observation, and it is not necessary to send a product with poor bonding to a subsequent process.

Sectional drawing which shows typically the structure of the sealed battery which is an example of embodiment of this invention The enlarged view of the junction part of the battery exterior can and the current collection tab which is an example of embodiment of this invention The longitudinal cross-sectional schematic diagram of the junction part of the battery exterior can and the current collection tab which is an example of embodiment of this invention The graph which each shows the laser intensity | strength and processing position which are supplied at the time of the laser processing to a fusion | melting part and a test process part in embodiment of this invention Explanatory drawing which shows the laser processing apparatus for enforcing the manufacturing method of the sealed battery which is an example of embodiment of this invention Explanatory drawing which shows the joining method by the conventional pulse YAG laser Explanatory drawing which shows the joining method by the fiber laser in embodiment of this invention Conceptual diagram for explaining the principle of keyhole welding The graph which showed the relationship between the irradiation laser intensity | strength in the keyhole welding of embodiment of this invention, and a fusion | melting depth The graph which showed the relationship between the fusion depth and the fusion width in the keyhole welding of embodiment of this invention Processed portion photographed by laser processing by keyhole welding according to an embodiment of the present invention Processed portion photographed by laser processing by keyhole welding according to an embodiment of the present invention The enlarged bottom view for demonstrating the laser intensity in the fusion | melting part and test process part of embodiment of this invention The longitudinal cross-sectional schematic diagram for demonstrating the laser intensity in the fusion | melting part and test process part of embodiment of this invention Graph showing the relationship between laser intensity and machining position in FIG. 8B The enlarged bottom view for demonstrating an example of the laser intensity in the fusion | melting part and test process part of embodiment of this invention The enlarged bottom view for demonstrating another example of the laser intensity in the fusion | melting part and test processing part of embodiment of this invention The enlarged bottom view for demonstrating another example of the laser intensity in the fusion | melting part and test process part of embodiment of this invention Explanatory drawing of the different laser processing pattern in the fusion | melting part and test processing part of embodiment of this invention Explanatory drawing of another laser processing pattern in the fusion | melting part and test processing part of embodiment of this invention Explanatory drawing which shows the laser processing apparatus for enforcing the battery manufacturing method in embodiment of this invention FIG. 10A is a schematic vertical cross-sectional view of a melting part and a test processing part in the battery manufacturing method of FIG. 10A. Explanatory drawing of the laser processing pattern in the fusion | melting part and test processing part of embodiment of this invention in the battery manufacturing method of FIG. 10A. Explanatory drawing which shows the laser processing apparatus for enforcing the battery manufacturing method in embodiment of this invention FIG. 11A is a schematic vertical cross-sectional view of a melting part and a test processing part in the battery manufacturing method of FIG. 11A. Explanatory drawing of the laser processing pattern in the fusion | melting part and test processing part of embodiment of this invention in the battery manufacturing method of FIG. 11A The figure which shows the conventional sealed type battery described in patent document 3, and its manufacturing method Enlarged view of the melting part of a conventional sealed battery

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, each embodiment or modification shown below exemplifies a method for manufacturing a cylindrical battery in which the present invention is specifically put into practical use, and the present invention is specified as a method for manufacturing a cylindrical battery. And is equally applicable to other embodiments within the scope of the claims, such as, for example, a prismatic battery. In addition, it is considered that the present invention can be applied not only to batteries but also to general laser bonding.

(Configuration common to the embodiments)
FIG. 1 is a cross-sectional view schematically showing a configuration of a sealed battery as an example of a laser welded product in an embodiment of the present invention.

  As shown in FIG. 1, a plurality of winding bodies 4 in which a positive electrode plate 1 and a negative electrode plate 2 are wound via a separator 3 are sandwiched between insulating plates 7 and 8 in a battery outer can 5. And is stored together with the electrolyte. The opening of the battery outer can 5 is sealed with a sealing plate 10 via a gasket 6. The positive electrode current collecting tab 11 led out from any one of the electrode plates (for example, the positive electrode plate 1) of the winding body 4 is laser welded to the sealing plate 10 at the melting portion 9. Further, the negative electrode current collecting tab 12 led out from the other electrode plate (for example, the negative electrode plate 2) is laser-bonded at a melting portion (laser melting portion) 13 on the outer bottom surface of the battery outer can 5. The battery outer can 5 is an example of a first workpiece. The current collecting tabs 11 and 12 are examples of the second workpiece. The sealed battery is an example of a laser welded product.

  Such a sealed battery is manufactured by the following manufacturing method.

  First, a wound body 4 is formed in which the positive electrode plate 1 and the negative electrode plate 2 are wound or laminated with a separator 3 interposed therebetween.

  Next, one end of each current collecting tab 11, 12 is connected to each electrode plate 1, 2 of the winding body 4.

  Next, the wound body 4 is accommodated in the battery outer can 5.

  Next, the current collecting tab 12 is disposed so that the other end of the current collecting tab 12 is in contact with the bottom surface of the inner surface of the battery outer can 5.

  Next, a laser beam 23 having a spot diameter d smaller than the plate thickness h of the battery outer can 5 is irradiated at an irradiation position on the outer bottom surface of the battery outer can 5, for example, approximately in the center, in a direction (central axis) perpendicular to the outer bottom surface. Or by irradiating at a fixed irradiation angle with respect to the direction orthogonal to the outer bottom surface to form the melting portion 13 (see FIG. 2A). The melting part 13 does not penetrate through the current collecting tab 12, and the battery outer can 5 and the current collecting tab 12 are non-through joined. Simultaneously with this irradiation, a plurality of test processing parts 14 are also formed by irradiating a plurality of laser beams 23 in the vicinity of the melting part 13 using diffraction.

  As a result, linear processing marks are formed as the melting portion 13 and the test processing portion 14 on the outer surface of the battery outer can 5.

  Hereinafter, it will be described in detail that the laser welding quality determination is performed based on the shape of the processing mark of the test processing unit 14.

(Configuration of sealed battery)
Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  FIG. 2A is an enlarged view of the joint melting portion 13 between the battery outer can 5 and the negative electrode current collecting tab 12 in the embodiment of the present invention. The shape or length of the melted portion 13 is changed depending on the required bonding strength or process. In FIG. 2A, the melting part 13 is shown by the simplest point, but details will be described later. Mainly in an actual process, the melting part 13 is constituted by a straight line having a certain length in order to ensure the bonding strength between the battery outer can 5 and the negative electrode current collecting tab 12. This indicates that the processing is performed while moving the battery outer can 5 to be processed in one direction while performing laser processing, so that the processing trace is a straight line.

  The test processing part 14 is usually located in the vicinity of the melting part 13 and forms the same shape as the melting part 13 and is mainly a point or a straight line, but is not the same depending on the laser processing method. It is also possible (such as in the case of the embodiment of FIG. 11 described later).

  FIG. 2B is a schematic cross-sectional view of FIG. 2A. The battery outer can 5 and the negative electrode current collecting tab 12 are joined at the joining and melting part 13. The melting part 13 does not penetrate the negative electrode current collector tab 12 and melts downward in the negative electrode current collector tab 12.

  FIG. 2C shows the laser intensity supplied at the time of laser processing to the melting part 13 and the test processing part 14, respectively. It is confirmed that the laser intensity 13S supplied to the melting part 13 is much larger than the laser intensity 14S supplied to the test processing part 14. For example, the laser intensity to the test processing part 14 is 1/100 or less of the laser intensity supplied to the melting part 13, and when there are a plurality of laser intensity, the supplied laser intensity is changed. Also in appearance, it can be confirmed that the melting width is different from the melting part 13. It is desirable that the test processing unit 14 has a laser intensity smaller than the melting unit 13 and a melting depth shallower.

  It is essential that these laser beams be supplied simultaneously from the same laser oscillation unit, and it is desirable to use a diffraction grating or the like as a method of creating such a laser profile. Details will be described later.

(Joining equipment)
Next, FIG. 3 shows a joining apparatus for joining the battery outer can 5 and the negative electrode current collecting tab 12 by forming the melting part 13 and the test processing part 14 shown in FIG. 2A.

  FIG. 3 shows a bonding apparatus (laser processing apparatus) including a laser oscillator 19, laser parallel light 20, a diffraction grating 21, a laser processing head 22, and a focused laser beam 23. Reference numeral 24 denotes a condensing point where the laser beam 23 condenses. The focused laser beam 23 is branched into a plurality of locations by the diffraction grating 21 for the melting portion 13 and the test processing portion 14.

  First, the beam quality (condensed spot diameter) of the laser beam 23 emitted from the laser oscillator 19 and the laser processing head 22 used in this bonding apparatus will be described. Although the laser beam 23 is branched by the diffraction grating 21, one of the beams will be described assuming that the beam intensity is the same although the laser intensity is different.

  The plate thickness of the battery outer can 5 is usually 0.2 to 0.5 mm, and the plate thickness of the negative electrode current collecting tab 12 is usually about 0.1 to 0.2 mm. In Patent Documents 1 to 3, laser welding is performed in a pointwise manner using a pulsed YAG laser or the like, for such a thin plate overlapping laser joining. The spot diameter of the pulse YAG laser is about φ0.6 mm, which is larger than the plate thickness of the battery outer can 5 and is heat conduction type laser welding.

(Problems of bonding method using conventional pulsed YAG laser)
FIG. 4 is a view showing a conventional method of joining the battery outer can 5 with a pulsed YAG laser. The laser beam 23 is irradiated on the upper surface of the battery outer can 5, and first, the upper surface of the battery outer can 5 is melted to form a melting portion 13 (see FIG. 4A).

  Next, when the laser beam 23 continues to be irradiated, the melted portion 13 spreads in a heat conductive manner, but there is an air layer between the battery outer can 5 and the negative electrode current collecting tab 12, and the heat conduction is divided. Has been. For this reason, the melting part 13 temporarily stays only in the battery outer can 5 and the negative electrode current collecting tab 12 is not melted (see FIG. 4B).

  Furthermore, when the laser beam 23 continues to be irradiated and the battery outer can 5 and the negative electrode current collecting tab 12 are in close contact with each other, the thermal energy of the melting portion 13 is transmitted to the negative electrode current collecting tab 12 and the negative electrode current collecting tab 12 is melted. Then, the negative electrode current collecting tab 12 and the battery outer can 5 are joined (see FIG. 4C). Since the surface melt size on the battery outer can 5 of the melting part 13 at this time is expanded by heat conduction, it is larger than the spot diameter φ0.6 mm of the laser beam 23, and is about φ1 mm as an example.

  On the other hand, as an example, the diameter of the wire bond for connecting each electrode of each sealed battery is φ0.2 mm, and the tip joint portion is about 0.4 mm. Since the surface melt size of the melted portion 13 is considerably larger than the wire bond tip joining size, the bonding reliability of the wire bond at the melted portion is lowered.

  Further, since the negative electrode current collecting tab 12 is thinner than the battery outer can 5 and has a smaller heat capacity, heat energy is easily transmitted to the negative electrode current collecting tab 12 and the negative electrode current collecting tab 12 is immediately penetrated and melted. (See FIG. 4 (d)). When the melting part 13 penetrates and melts the negative electrode current collecting tab 12, spatter is mixed inside the battery, leading to a short circuit or poor ignition, resulting in a failure.

  On the other hand, in FIG. 4B, if the input laser power is too strong, the spot diameter of the laser beam 23 is large and the plate thickness of the battery outer can 5 is thin. (See FIG. 4 (b ′)), and further, a hole 25 is formed in the negative electrode current collecting tab 12 (see FIG. 4 (d ′)), resulting in battery leakage failure.

  Therefore, if deep penetration type laser welding (keyhole welding) can be performed instead of heat conduction type laser welding, the surface melting area becomes small, so that the bonding reliability of wire bonds can be ensured, and through welding and hole welding are possible. Aperture 25 can be prevented. For example, since the fiber laser is far superior in laser beam quality to the conventional pulse YAG laser, the spot diameter can be made very small, for example, about φ0.02 mm. Therefore, the power density at the condensing point can be made very strong.

(Joint method using fiber laser in the embodiment)
FIG. 5 is a diagram showing a bonding method using a fiber laser used in the embodiment of the present invention.

  First, the laser beam 23B emitted from the fiber laser is locally irradiated on the upper surface of the battery outer can 5 to form the melted portion 13B in the battery outer can 5 and the power density of the laser irradiated portion is high. Vaporizes at the center of the melting portion 13B, and the keyhole 26 is formed by the evaporation repulsion force of the metal vapor (see FIG. 5A).

  Next, when the laser beam 23B enters the keyhole 26, the laser beam 23B is reflected from the inner surface of the keyhole 26, and the keyhole 26 grows deeply (see FIG. 5B). ).

  Further, when the laser beam 25B is continuously irradiated, the keyhole 26 grows deeply, and the molten portion 13B reaches the negative electrode current collecting tab 12 (see FIG. 5C).

  Next, when the laser irradiation is stopped (see FIG. 5D), the keyhole 26 disappears, the molten portion 13B is solidified, and the battery outer can 5 and the negative electrode current collecting tab 12 are joined. As an example, the spot diameter of the fiber laser is as small as φ0.02 to 0.05 mm, and the melt diameter or melt width of the melted part 13B is also as small as about 0.1 mm. Since this surface melt size is considerably smaller than the wire bond tip joint size, wire bond joint reliability at the melt portion 13B can be ensured.

(Keyhole welding principle)
FIG. 6 is a conceptual diagram for explaining the principle of keyhole welding. FIG. 6 shows a state where a keyhole 29 having a diameter X is generated by irradiating a plate-shaped member 27 having a thickness h with a laser beam 28. The keyhole 29 is maintained by balancing the evaporation repulsion force Pa of the metal vapor of the molten plate member 27 and the surface tension Ps of the molten plate member 27.

  At this time, the surface energy E (X) of the keyhole 29 is generally expressed by the following formula (1) (for example, Isamu Miyamoto “Fine High-Speed Welding of Metal Foil Using Single Mode Fiber Laser”; 58th Laser (See Processing Society Proceedings; March 2003).

E (X) = πG [hX + 1/2 (D ² −X ² )] (1)
Here, G is the surface energy of the liquid metal of the plate-like member 27, and D is the diameter of the melting region 30.

  From the equation (1), the following equation (2) is obtained.

dE / dX = πG (h−X) (2)
From Equation (2), when X> h, dE / dX <0, and the surface energy E decreases (dE) due to the increase in the diameter X of the keyhole 29 (dX). Become. On the other hand, in the case of X <h, dE / dX> 0, and the surface energy E increases (dE) due to the increase in the diameter X of the keyhole 29 (dX), so the diameter X of the keyhole 29 contracts, Equilibrium with evaporation repulsion force Pa.

  Therefore, if the laser beam 28 having the spot diameter d smaller than the thickness h of the plate member 27 is used, stable keyhole welding can be performed. Furthermore, by reducing the diameter D of the melting region 30 formed by keyhole welding from the thickness h of the plate-like member 27, more stable keyhole welding can be performed.

(Joint method with small surface melt size and little change in melt width even if processing power changes slightly)
As shown in FIGS. 5 and 6, in the keyhole welding used in the embodiment of the present invention, the surface melt size is small with respect to the penetration depth, and the melt width changes even if the machining power slightly changes. There may be few.

  The description will be described again with reference to FIGS. 7A to 7D.

  FIG. 7A is a graph showing the relationship between laser intensity and melting depth in keyhole welding. When the melting depth necessary for joining is within the range of the allowable melting depth 39, the variation in laser intensity needs to be within the laser intensity range 31. However, the laser intensity actually irradiated to the battery outer can 5 is unknown.

  FIG. 7B is a graph showing the relationship between the melt width and the melt depth during the same processing. When it is desired to confirm the laser intensity with the width of the melted portion 13 that can be determined from the appearance, the melt width 32 corresponding to the allowable melt depth 39 is very narrow.

  FIG. 7C and FIG. 7D show actual photographs of a non-defective product (joint good product) and a defective product (joint defective product), respectively. In FIG. 2A, the melting part 13 is indicated by a dot, but the photographs in FIGS. 7C and 7D are actual processes, and the melting part 13 on the battery outer can 5 is indicated by a line. The melt widths 33 and 34 are substantially the same width as can be seen from FIGS. 7C and 7D, and when this state is shown in FIG.

  As can be seen from FIG. 7B, the melt width does not change greatly even if the melt depth changes. Therefore, in this welding method, it can be said that it is difficult to confirm the change in the laser intensity at the melting part 13 appearing on the outer appearance of the battery outer can 5.

(Confirmation of changes in laser intensity)
Next, with reference to FIGS. 8A to 8F, an embodiment of the present invention for confirming the change in the laser intensity by observing the appearance of the battery outer can 5 will be described in more detail. From here, the shape of the melted part 13 is shown as a line in order to describe it closer to the actual process. As a means for making the shape of the melted portion 13 from a point to a line, an irradiation angle of a workpiece (such as a battery outer can 5 in the embodiment of the present invention) during laser processing is changed by using a known galvano mirror. Although a method of moving in one direction is taken, description of such a known configuration is omitted.

  And this time, the case where three types of test processing parts 14 (14a, 14b, 14c) with different laser intensities are applied will be described. In order to confirm the change in the laser intensity more accurately, the laser intensities are different. Although it is necessary to apply the test processing units 14 in multiple stages, in this specification, the test processing units 14 (14a, 14b, 14c) of three stages will be described as a representative example.

  8A and 8B are similar to FIGS. 2A and 2B, but are re-described as FIGS. 8A and 8B for ease of understanding.

  FIG. 8C is an enlarged view of the laser intensity 14S irradiated to the test processing unit 14 in FIG. 2C. As an example of the laser intensity 14S of the test processing unit 14, three different laser intensities 35-1 are shown. , 35-2, and 35-3, there are test processing portions 14a, 14b, and 14c. Since the laser intensity 35-1 is 1/100 or less of the laser intensity 13S of the melting part 13, the upper end of the laser intensity 13S is not shown. In this case, the laser intensity is decreased in the order of the laser intensity 35-1, the laser intensity 35-2, and the laser intensity 35-3. An example of the laser intensity ratio is, for example, 13S: 35-1: 35-2: 35-3 = 500: 50: 30: 10. However, 13S is the minimum laser intensity required when the battery outer can 5 and the negative electrode current collecting tab 12 are laser-bonded by the melting portion (laser melting portion) 13 on the outer bottom surface of the battery outer can 5.

  And the state of the melt mark at the time of processing with this laser processing profile is shown in FIGS. 8D to 8F.

  In order to realize this laser profile, means for decomposing the laser beam into a predetermined laser intensity, such as the diffraction grating 21 shown in FIG. 3, is necessary. A laser branching method using the diffraction grating 21 A well-known structure can be used for.

  FIG. 8D shows a case in which the laser intensity is higher than a predetermined level, and among the test processed parts 14a, 14b, 14c, the test processed parts 14a, 14b, 14c, that is, the laser intensity 35-1 to 35-3. The processing trace of the processing line is confirmed in all three.

  FIG. 8E shows a state of a predetermined laser intensity, and it can be confirmed that the processing trace of the processing line of the test processing portion 14c having a weak laser intensity 35-3 in the test processing portions 14a, 14b, and 14c has disappeared. .

  FIG. 8F shows a case where the laser intensity is weaker than a predetermined value, and the processing trace of the processing line is confirmed only in the test processing section 14a having the highest laser intensity 35-1 among the test processing sections 14a, 14b, and 14c. I can do it.

  That is, the case of FIG. 8E in which the processing traces of the processing lines with the laser intensities 35-1 and 35-2 among the processing lines with the laser intensities 35-1 to 35-3 can be confirmed is a non-defective product (bonding non-defective product). 8F with only the processing trace of the processing line of -1 and FIG. 8D in which the processing traces of the three processing lines with the laser intensities 35-1 to 35-3 can be confirmed are regarded as defective (joint defective products). I can do it. Therefore, the laser intensity irradiated to the battery outer can processing part is confirmed by grasping the state of the processing marks of the processing lines of the test processing parts 14a, 14b, and 14c without observing the cross section of the molten surface, and whether or not the welding is good. Judgment can be made.

  In this example, the test processing unit 14 is described as being in the state of processing traces of three processing lines with laser intensities 35-1 to 35-3. It is also possible to determine whether or not the product is good with the state of the processing traces of the two types of processing lines 35-2.

  According to this example, usually, the quality of the welded state requires observation of the joint surface by a destructive test, or nondestructive inspection using ultrasonic waves, but as described above, two or three types, etc. It is possible to make a pass / fail judgment based on the state of the machining trace of the machining line. If comprised in this way, only the external appearance test | inspection immediately after welding will be sufficient, and an installation investment or the addition of an inspection process becomes unnecessary. In addition, 100% inspection can be performed and quality control can be performed at a higher level.

  In this case, the non-defective product is a case where the processing trace of the processing line of the laser intensity 35-1 has a desired shape (straight line), and the defect is confirmed by two laser intensity 35-1 and 35-2, or the laser intensity 35- This is a case where only 1 is visible and the laser intensity 35-1 is other than the desired shape (disconnection).

  Although it can be confirmed by the above method that the laser intensity is within an appropriate range, the laser power ratio of 13S: 35-1: 35-2: 35-3 is appropriately set according to the actual processing conditions. It is important to. The determination of the ratio depends on the design of the diffraction grating 21.

  In addition, this time, the quality of welding is determined by the shape of each processing mark of the test processing unit 14 (presence / absence and state when it exists). However, fading occurred in the middle of each line. In such a case, it is determined by the process whether to determine the defect at that time.

  Note that the determination of each shape (the presence / absence and state of presence) of the processing marks of the test processing unit 14 can be performed if an imaging device such as a camera and a control unit are provided. For example, after the fusing unit 13 and the test processing unit 14 are imaged with an imaging device such as a camera, the imaged image information is binarized with the binarizing unit of the control unit, and then image processing with the image processing unit of the control unit After that, it can be determined by the determination unit of the control unit.

  9A and 9B show a similar example of FIG. 8A.

  FIG. 9A shows a case where there are three melted portions 13 and three test processed portions 14a, 14b and 14c having three different laser intensities 36-1 to 36-3 as the test processed portion 14. Yes. In the laser intensity 36-1 to 36-3, the laser intensity is decreased in the order of the laser intensity 36-1, the laser intensity 36-2, and the laser intensity 36-3.

  As described above, even when a plurality of melted portions 13, that is, a plurality of places are simultaneously processed as shown in FIG. 9A, it is possible to determine whether the product is good or bad by the same method as in FIG.

  FIG. 9B shows a case where there are test processing portions 14 on both sides of the melting portion 13, and a case where there are processing traces of processing lines with laser intensities 36-1 to 36-3 as described above. In this case, the pass / fail judgment is performed separately on both sides.

  According to such a configuration, it is possible to refer to the determination results on the left and right sides of the melted portion 13 in FIG. 9B as compared to the case of FIGS. 8B and 9A where the test processing portion 14 exists only on one side. Since this is possible, this is an example in which the state of the test processing unit 14 (such as the presence or absence of the processing trace of the processing line and the shape) can be confirmed with higher accuracy.

  Also in the above, similarly to the case of FIG. 8A, the test processed portions 14a, 14b, 14c having the laser intensities 36-1 to 36-3 or the melting portion 13 are used, the melting portion 13, and 36-1, 36- For example, if the processing traces of the processing lines with the laser intensity 36-1 and 36-2 can be confirmed from the state of the processing traces of the three types of processing lines 2), the laser intensity 36-1 alone or the laser intensity 36 is determined. When the processing traces of the three processing lines -1 to 36-3 can be confirmed, it can be determined that the processing is defective.

  In FIG. 9B, compared with FIG. 8A, it is possible to determine pass / fail from the welding results on both sides by providing test processing portions 14a, 14b, 14c for determining pass / fail on both sides of the melted portion 13 which is the main processed portion. Judgment can be made with higher accuracy.

  Next, embodiments according to the present invention will be described with reference to the drawings.

  FIG. 10A shows a laser processing apparatus similar to FIG. The difference is that laser irradiation is obliquely applied to the outer bottom surface of the battery outer can 5.

  FIG. 10B is a cross-sectional image of the processed part when processed in the state of FIG. 10A. Since the focused laser beam 23 is obliquely applied to the outer bottom surface of the battery outer can 5, the melting direction of the melting part 13 is oblique. The same applies to the test processing portions 14 (14a, 14b, 14c) formed by the laser beams (second to fourth laser beams) 23a, 23b, 23c branched from the laser beam (first laser beam) 23. It becomes slanted. However, since the laser beams 23a, 23b, and 23c are obliquely irradiated, the melting depth is shallower than in the case of FIG.

  FIG. 10C is a view of FIG. 10B as seen from the surface (outer bottom surface) of the battery outer can 5 with the melted portion (first processing trace) 13 and the test processing portion 14. As can be seen from FIG. 10C, the processing traces (second to fourth processing traces) of the melted portion 13, the test processing portion 14, and the test processing portions 14 a, 14 b, 14 c in the test processing portion 14 are shown in FIG. Looks like 8A. Also in the test processing parts 14a, 14b, 14c, the laser intensity 37-1 to 37-3 is shown as a case where the laser intensity is decreased in order from the test processing part 14a to the test processing part 14c.

  As a method for determining whether or not the bonding is good, as in the case of the determination method in FIG. 8A, if the processing traces of the processing lines with the laser intensities 37-1 and 37-2 can be confirmed, it is regarded as a non-defective product. If the processing traces of the three processing lines having the laser intensities 37-1 to 37-3 can be confirmed, it can be regarded as defective, and as the test processing 14, the two processing of the test processing portions 14a and 14b It can be understood that the quality of the processing marks on the line can be judged, and that the effect of the present invention can be obtained even with the processing method as shown in FIG. 10A.

  As shown in FIG. 10A, the beam irradiation width is widened by performing the oblique processing as compared with the vertical processing. Even in such a case, it is possible to make a pass / fail judgment based on how the machining traces of the machining line are visible, as in the other examples.

  Next, embodiments according to the present invention will be described with reference to the drawings.

  FIG. 11A shows a laser processing apparatus similar to FIG. 10A. The difference is that the battery outer can 5 also includes a rotation mechanism 51 such as a motor that rotates around a rotation center (laser processing center) 52 that passes through the condensing point 24. The purpose of processing by this method is to minimize the area of the melted portion 13 on the outer bottom surface of the battery outer can 5 of the melted portion 13, but to maximize the melted portion as the melted portion 13. Adopting a simple process and configuration.

  FIG. 11B is a cross-sectional image diagram of a processed portion when processed in the state of FIG. 11A. In this example, the focused laser beam 23 is obliquely applied to the outer bottom surface of the battery outer can 5, so that the processing trace is also oblique.

  Test processing portions 37 formed by the laser beams 23a, 23b, and 23c branched from the laser beam 23 are referred to as test processing portions 37a, 37b, and 37c.

  Since the battery outer can 5 is rotating, the test processing portions 37a, 37b, and 37c are present in an annular shape around the melting portion 13, and are present on both sides of the melting portion 13 when viewed as a cross section. It becomes a shape.

  11C is a view of FIG. 11B as seen from the outer bottom surface of the battery outer can 5 with the melting portion 13 and the test processing portions 37a, 37b, and 37c. As can be seen from FIG. 11C, the melting part 13 is a small circular point, and the appearance area of the melting part 13 is reduced. Further, the test processing portions 37a, 37b, and 37c are rotated, so that they appear to have an annular shape around the melting portion 13. Similarly to the case of FIG. 10A to FIG. 10C, the test processing portions 37a, 37b, and 37c are shown as cases where there are three types of laser processing lines at the laser intensities 38-1 to 38-3. Since the laser intensity is decreased in the order of 1 to 38-3, the thickness of the processing mark is also gradually reduced.

  The variation in the laser intensity in this laser processing process is similar to the case shown in FIGS. 8A to 10C. The presence or absence of processing traces of the laser intensity 38-1 to 38-3, the melted portion 13, and the laser intensity 38 The pass / fail judgment can be made based on the visibility of −1 and 38-2. For example, when processing traces with laser intensities 38-1 and 38-2 are visible, good products, only processing traces with laser intensity 38-1, or all processing traces with laser intensities 38-1 to 38-3 are visible. NG or the like. When the melted part 13 and the test processing parts 37a and 37b having two kinds of laser intensities 38-1 and 38-2 are used, if the processing marks of the melted part 13 and the laser intensity 38-1 are visible, the good part, the melted part 13 If all of the processing marks of the melted part 13 and the laser intensity 38-1, 38-2 are visible, it can be regarded as defective.

  In this example, the melting part 13 is a small circular point, and the appearance area of the melting part 13 is small. Even in such a case, it is possible to determine the quality of the joining at the melting portion 13 only by observing the appearance of the annular processing marks of the test processing portions 37a, 37b, 37c or the test processing portions 37a, 37b. In addition, since there exists a subject that a wire bonding cannot be performed on a welded part, the melted part 13 is set to a small circular point in this way. This is to meet the demand to increase the area of the region usable in the process. According to the present example, as described above, it is possible to perform the bonding quality determination only by the appearance inspection while responding to such a request.

  As described above, according to the laser welding quality determination method according to the embodiment, the welding is not affected at the same time as the welding of the battery outer can 5 and the current collecting tab 12 at the melting portion 13. A test processing portion 14 is provided on the processing surface with a low laser intensity 14S. By configuring in this way, it is possible to determine whether the laser joining at the melting part 13 in the joining of the battery outer can 5 and the current collecting tab 12 is good or bad by only observing the appearance of the test processing part 14 without observing the cross section of the melting surface. It can be judged. That is, by observing only the appearance of the battery outer can 5, in other words, by grasping the state of the processing trace of the test processing unit 14 (processing change at the time of laser welding), the laser intensity 13 S irradiated to the melted part 13 is appropriate bonding strength. It is possible to determine whether or not the product is defective.

  In addition, it can be made to show the effect which each has by combining arbitrary embodiment or modification of the said various embodiment or modification suitably. In addition, combinations of the embodiments, combinations of the examples, or combinations of the embodiments and examples are possible, and combinations of features in different embodiments or examples are also possible.

  The laser welded product and battery laser welding quality determination method of the present invention is a means for visually confirming the laser intensity fluctuation of a laser beam as a joining means, and the effect of eliminating a quality defect that a poorly joined product is passed to a subsequent process. It can be applied not only to batteries, but also to other fields using laser welding. The type of the sealed battery as an example of the laser welded product to which the present invention is applied is not particularly limited, and can be applied to a nickel hydride battery, a nickel cadmium battery, and the like in addition to a lithium ion secondary battery. . Further, the present invention is not limited to a cylindrical secondary battery, but can also be applied to a square secondary battery and a primary battery. Furthermore, as an example of the laser welded material, the positive electrode plate and the negative electrode plate are not limited to the electrode group wound through the separator, but may be a member laminated in a plurality of layers.

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Winding body 5 Battery outer can 6 Gasket 7 Upper insulating plate 8 Lower insulating plate 9 Melting part 10 Sealing plate 11 Positive electrode current collection tab 12 Negative electrode current collection tab 13 Melting part 13S Laser intensity 14, 14a, 14b, 14c Test processing part 14S Laser intensity 19 Laser oscillator 20 Laser parallel light 21 Diffraction grating 22 Laser processing head 23, 23a, 23b, 23c Laser beam 24 Condensing point 25 Perforated hole 26 Keyhole 27 Plate-shaped member 28 Laser Beam 29 Keyhole 30 Melting area 31 Laser intensity range 32 Melting width 33, 34 Melting width 35-1 to 35-3 Laser intensity 36-1 to 36-3 Laser intensity 37a, 37b, 37c Test processing parts 38-1 to 38 -3 Laser intensity 39 Allowable melting depth 51 Rotating mechanism 52 Center of rotation

Claims (6)

A battery laser welding quality determination method in which a current collecting tab of a battery is welded and joined to a battery outer can at a melting portion,
Contacting the flat surface of the current collecting tab with the bottom surface of the inner surface of the battery outer can;
Irradiation that irradiates the outer bottom surface of the battery outer can with a first laser beam having a spot diameter smaller than the plate thickness of the battery outer can to form a first processing mark of the melted portion by the first laser beam. A process,
In the irradiation step, the first laser beam having the laser intensity for joining the battery outer can and the current collecting tab at the melting portion is irradiated to the outer bottom surface of the battery outer can, and at the same time, the first laser Irradiating the battery outer can simultaneously with irradiation of a second laser beam having a laser intensity lower than the laser intensity of the beam and irradiation of a third laser beam having a laser intensity lower than that of the second laser beam;
After the irradiation step, the battery laser welding further includes a determination step of determining a bonding failure based on a shape of the second processing mark of the second laser beam and a shape of the third processing mark of the third laser beam. Pass / fail judgment method.   In the determination step, a case where the second machining trace can be confirmed is regarded as a non-defective product, and if the third machining trace can be confirmed, or at least a part of the second machining trace cannot be confirmed, the bonding failure The battery laser welding quality determination method according to claim 1, wherein:   The battery laser welding quality determination method according to claim 1 or 2, wherein, in the irradiation step, the first to third laser beams are obliquely irradiated to the outer bottom surface of the battery outer can.   In the irradiation step, the battery outer can is rotated around a laser processing center, the melted portion becomes circular, and other processing traces have an annular shape. A method for determining the quality of laser welding of the battery according to the description. In the laser welded product obtained by superposing the first work piece and the second work piece and performing laser welding,
A first processing mark on the laser beam irradiation surface of the first workpiece, wherein the overlapped surface of the first workpiece and the second workpiece is laser welded by laser beam irradiation;
A second machining trace obtained by laser melting only the laser beam irradiation surface of the first workpiece without penetrating the first workpiece;
A third processing mark obtained by laser melting only a laser beam irradiation surface of the first workpiece without penetrating the first workpiece with a laser intensity lower than that of the second processing mark;
A laser welded article. The laser weld is a battery;
The first workpiece is a battery outer can of the battery,
The second workpiece is a current collecting tab of the battery;
The laser welded product according to claim 5, wherein the current collecting tab is welded to the battery outer can.