JP2000090906A - Lead joining structure and battery pack using the structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide lead joining structure stably joining leads having different materials and thicknesses and apply the structure to a battery pack. SOLUTION: A positive electrode lead 12 of a battery 3 is formed with foil- like aluminum, and joined with an outside output terminal 6a made of phosphor bronze through a positive electrode connecting lead 30 made of a clad material of aluminum and phosphor bronze.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead joining structure for joining leads of different metals and having different thicknesses.
Further, the present invention relates to a battery pack using the joining structure.

[0002]

2. Description of the Related Art The ratio of a battery to the volume and weight of a portable information device such as a cellular phone or a mobile computer is not small, and it is said that the battery holds the key to reducing the size, weight and thickness of the portable information device. Not too much. For example, the miniaturization of mobile phones has been remarkable, and has been realized to fit in a pocket. However, it cannot be said that the requirement for thinning is satisfied, and only when the thinning is realized, the portability becomes excellent. This thinning also depends on how thin the battery can be made. The conventional lithium-ion secondary battery has a limit in thinning, so a power generation element in which a positive electrode plate and a negative electrode plate are laminated via a polymer electrolyte sheet is housed in an outer case formed by a laminate sheet. Attempts have been made to construct a battery pack for a portable information device using the lithium polymer secondary battery.

[0003]

However, when a power generating element is accommodated in an outer case formed of a laminate sheet, the positive electrode lead and the negative electrode lead are drawn out from between the welding seals of the laminate sheet. In order to maintain the sealing property of the seal, the positive and negative leads need to be formed of an extremely thin metal material. Therefore, each of the positive and negative leads is formed by a foil-shaped lead, and there has been a problem that it is difficult to join them to components such as an external output terminal of the battery pack by spot welding or the like. In particular, since the positive electrode lead is formed of aluminum, when joined to phosphor bronze or the like that constitutes the external output terminal, the melting temperature and hardness of aluminum foil are lower than that of phosphor bronze. , And sufficient bonding strength cannot be obtained.

[0004] An object of the present invention is to provide a lead bonding structure in which a lead drawn from a battery can be bonded to a mating lead connected thereto with sufficient bonding strength, and a battery pack using this structure. To provide.

[0005]

In order to achieve the above object, a first invention of the present application is directed to a method in which a mating lead for joining a foil lead formed on a foil metal thin plate is made of a different metal material from the foil lead. In a lead joining structure for joining between the overlapping of the foil lead and the mating lead, a first metal material having good joining compatibility with the foil lead is provided. A clad material obtained by rolling and joining a second metal material having good joining compatibility with the lead is disposed between the foil lead and the mating lead.
And the metal lead and the mating lead and the second metal material are melt-bonded to connect the foil lead to the mating lead.

According to this joint structure, a cladding material is arranged between a foil-like lead made of a dissimilar metal and a mating lead.
Since the first metal material and the second metal material constituting the clad material are joined together so that the sides having good joining chemistry are aligned with the foil leads or the mating leads, a stable joining strength is obtained and the foil leads are obtained. And the opposing lead can be joined.

According to a second aspect of the present invention, a mating lead for joining a foil-like lead formed on a foil-like metal thin plate is formed of a metal material different from that of the foil-like lead and is relatively thick. In a lead joining structure for joining between a superposed lead and a mating lead, a first metal material having good joining compatibility with the foil lead and a metal material used for the mating lead are roll-joined. A clad material is formed, a mating lead is formed from the cladding material, and the first metal material of the mating lead and the foil lead are joined together to form a foil lead. It is configured to be connected to a lead.

According to this joining structure, the mating lead for joining the foil leads is formed of the clad material, so that the surface of the clad material having good joining compatibility with the foil leads is joined to the foil leads. Then, stable bonding strength can be obtained.

In the above construction, the clad material is formed of a metal material of the same material as the foil-shaped lead and a metal material of the same material as the mating lead. Structure can be obtained.

In a third aspect of the present invention, a secondary battery and a battery protection device including a circuit board on which a protection circuit is formed and a PTC element are housed in a pack case. In a battery pack in which the extracted positive electrode lead and negative electrode lead are connected to an external output terminal and the battery protection device, the secondary battery is formed by laminating a sheet-like positive / negative plate and a pair of power generation elements. The peripheral portion of the sheet is housed in an outer case sealed by welding, and a positive electrode lead and a negative electrode lead formed in a foil shape with different metal materials are drawn out from one side of the welded seal. Between the positive electrode counterpart lead connected to the output terminal and / or between the negative electrode lead and the negative electrode counterpart lead connected to the battery protection device,
It is characterized in that it is configured to be joined via a clad material having the same kind of metal surface as the material for forming the positive electrode lead or the negative electrode lead.

According to this structure, the positive electrode lead and the negative electrode lead drawn from the battery are joined to the positive and negative electrode mating leads via the cladding material. And can be joined by facing each other at a metal surface of the same kind, and a stable joining strength can be obtained by joining between similar metals.

In the above-mentioned battery pack, since the positive electrode lead is formed of a clad material having a metal surface of the same kind as the material of the positive electrode lead, the positive electrode lead is formed of aluminum in a foil shape in the lithium polymer battery. However, it is difficult to obtain the bonding strength of the positive electrode mating lead made of phosphor bronze or the like due to a low melting temperature and hardness, but by forming the positive electrode mating lead with a clad plate having an aluminum surface, When the aluminum foil of the positive electrode lead and the aluminum surface of the clad material are joined together, stable joining strength can be obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The embodiment described below is an example embodying the present invention, and does not limit the technical scope of the present invention.

In this embodiment, the present invention is applied to a battery pack configured as a battery power source for a portable telephone, in which a positive electrode and a negative electrode lead drawn from an internal battery are connected to each component of the battery pack. And a battery pack to which the lead bonding structure according to the above is applied.

FIG. 1 is an exploded view of the configuration of the battery pack according to the embodiment. The battery pack 1 has an upper case 2a.
Battery 3 configured as a lithium polymer secondary battery in a pack case 2 composed of
A battery unit 1 containing a safety unit (hereinafter referred to as SU) 4 having a protection circuit and a PTC 5 which is a critical temperature resistance element is accommodated.
An external output terminal 6a for electrically connecting the
6b and 6c.

The battery pack 1 is configured to be removably mountable in a mobile phone, and includes a pack case 2
The upper case 2a that constitutes a part of the outer case of the mobile phone. Therefore, the upper case 2a is formed so as to exhibit the strength and aesthetic appearance as a device exterior. The upper case 2a and the lower case 2b are formed by resin molding, accommodate the battery 3 and the battery protection device 8, and are integrated by joining the two cases.

As shown in FIG. 2, the battery 3 is formed by laminating a sheet-like positive electrode plate and a negative electrode plate into a plurality of layers via a separator made of a polymer electrolyte sheet. The power generation element 10 is housed in a flexible outer case 11 made of a laminate sheet. The outer case 11 is formed by folding a laminate sheet cut in a strip shape into two, forming a bag by welding and sealing hatched portions on both sides, and accommodating the power generating element 10 therein. Positive electrode lead to positive electrode lead 1
2. The negative electrode lead 13 is pulled out from the negative electrode plate, the lead drawing side 11b is welded and sealed, and the inside of the outer case 11 is sealed. As shown in FIG. 1, the seal sides 11a on both sides are folded back toward the upper surface to reduce an increase in useless flat space. The battery 3 thus configured is
Compared with a conventional structure in which positive and negative electrodes are wound like a conventional lithium-ion secondary battery, the battery can be formed in a flat plate shape, and the battery pack 1 can also be formed thin. Can be contributed to.

The battery protection device 8 is provided with a protection circuit for controlling the charge and discharge to protect the battery 3 from overdischarge or overcharge on the circuit board 14 and the battery 4 from the excessive discharge current due to short circuit or the like. 3 is provided with a PTC element 5 for protecting the module 3 and supplied in an assembled state as shown in the figure. As shown in FIG. 3, the battery protection device 8 includes the circuit board 14 and the PTC at a predetermined position of the lower case 2b.
The device 5 is mounted with the plate surface direction parallel to the plate surface of the battery 3. After the battery protection device 8 is attached to the lower case 2b, as shown in FIG. 4, the battery 3 is housed in the lower case 2b, and the positive electrode lead 30 and the negative electrode lead 33 drawn out of the battery 3 are connected to the battery protection device. After connection with the device 8, the upper case 2a is joined to the lower case 2b to complete the battery pack 1.

The procedure for disposing the battery protection device 8, the battery 3, and the external output terminals 6a to 6c in the lower case 2b is performed as described below.

As shown in FIG. 1, the terminal mounting portions 19a, 19a, 90
9b and 19c are formed as recesses, respectively, and slit-like terminal insertion holes 22 are formed at two places in the upper and lower portions on the bottom surface of the recesses, as shown in FIG. As shown in FIG. 1, the external output terminals 6a, 6b and 6c formed in a U-shape are press-fitted into the terminal insertion holes 22 from both ends thereof. External output terminal 6a serving as a positive terminal
Has one of its tip portions formed longer, so that when it is mounted on the lower case 2b, the insertion tip is located above the joint hole 23 formed in the lower case 2b. I will peep. The end of the positive electrode connection lead 30 shown in FIG.
The two are joined by spot welding. FIG. 6 is a cross-sectional view showing a mounted state of the external output terminal 6a.
The end of the positive electrode connection lead 30 is placed on the insertion tip of the external output terminal 6a as shown by the up and down arrows, and one of the welding electrodes is inserted through the joint hole 23 to contact the insertion tip of the external output terminal 6a.
The other is applied to the positive electrode connection lead 30 to perform spot welding, and the two are joined. This positive electrode connection lead 30 is formed using a clad material, and is connected to the external output terminal 6a.
Phosphor bronze which is a material for forming
Is formed by rolling and joining to 0.15 mmt of phosphor bronze and 0.05 mmt of aluminum in correspondence with aluminum, which is a material for forming. In bonding with the external output terminal 6a, the surface of the phosphor bronze of the clad material is superimposed on the insertion end of the external output terminal 6a, and the same kind of metal is bonded, so that the melting temperature and hardness are the same. , Stable bonding strength can be obtained.

Further, the external output terminals 6a to 6c are press-fitted from the upper and lower terminal insertion holes 22 and 22 and fitted into the lower case 2b, and are joined to respective components provided in the lower case 2b. Therefore, a secure mounting structure is obtained. FIG.
As shown in FIG. 7, since the battery pack 1 is mounted in close contact with the bottom surfaces of the terminal mounting portions 19a to 19c, the pressure from the connection probe 44 pressed for electrical connection when the battery pack 1 is mounted on the mobile phone. Thus, a reliable connection state can be obtained, and an electrical connection with low contact resistance can be made.

Next, as shown in FIG.
The test terminals 24a and 24b provided on the lower case 2b
The battery protection device 8 is positioned by fitting into the test terminal windows 29a and 29b formed in the lower case 2b.
At the end of the FIG. 7 is a cross-sectional view showing the arrangement of the test terminals 24b. The portion of the test terminal 24b whose front end is bent in a U-shape is fitted into one side of the test terminal window 29b for positioning and, at the same time, the lower end is placed in the lower case. 2b. Since the tips of the test terminals 24a and 24b are located outside from the outside through the test terminal windows 29a and 29b, the inspection probe 43 is brought into contact with the inspection probe 43 at the time of the production inspection after the completion of the battery pack 1 to provide an electrical inspection. Is done.

When the battery protection device 8 is positioned on the lower case 2b, as shown in FIG. 8, the circuit board 14 constituting the SU 4 is connected to the external output terminals 6 mounted on the lower case 2b.
The external output terminals 6a, 6b, 6c are arranged below the soldering lands 31a, 31b, 31c formed on the circuit board 14 and arranged below the a, 6b, 6c. The external output terminals 6a, 6b, and 6c are soldered to the soldering lands 31a, 31b, and 31c, respectively, so that the terminals are connected. At the same time, the external output terminals 6a to 6c and the battery protection device 8 are placed on the lower case 2b. The position is fixed.

As shown in FIG. 8B, since the plate surfaces of the circuit board 14 and the PTC element 5 are arranged in parallel with the bottom surface of the lower case 2b, the thickness of the portion accommodating the battery protection device 8 is increased. Space in the vertical direction can be reduced. Furthermore,
As shown in FIG. 4, a space in the thickness direction for accommodating the lead lead-out side 11b of the battery 3 on the battery protection device 8 can be created, and the battery pack 1 can be used without creating a wasteful space in the pack case 2. Improved miniaturization.
In addition, the lead lead side 11b covers the upper surface of the battery protection device 8, thereby preventing the positive electrode lead 12 and the negative electrode lead 13 drawn from the battery 3 from coming into contact with the battery protection device 8. In a state where the battery protection device 8 is provided, the negative electrode connection lead 3 provided on the battery protection device 8 is provided.
3 and the positive electrode connection lead 30 are arranged in an upright state at the end of the lower case 2b.

Next, as shown in FIG. 4, the battery 3 is accommodated in the lower case 2b with its lead lead-out side 11b facing the battery protection device 8 side. The battery 3 is arranged such that the lead extraction side 11b covers the battery protection device 8, and the accommodation position is determined between the concave portion 32 formed in the lower case 2b and the positioning convex portion. The positive electrode lead 12 and the negative electrode lead 13 drawn out from the lead extraction side 11b of the battery 3 face the positive electrode connection lead 30, respectively. This positive electrode lead 1
2 and the positive electrode connection lead 30 and the negative electrode lead 13 and the negative electrode connection lead 33 are joined by spot welding.

FIG. 9 shows the connection between the positive electrode lead 12 and the positive electrode connection lead 30. The positive electrode lead 12 is formed of aluminum having a thickness of 80 μm in the form of a foil and has a very low strength in view of its hardness. The positive electrode connection lead 30 is formed of a clad material formed by rolling and joining aluminum and phosphor bronze, as described above, in order to surely perform joining by spot welding. When the positive electrode connection lead 30 and the positive electrode lead 12 are spot-welded with the positive electrode lead 12 facing the aluminum-side surface of the positive electrode connection lead 30, stable bonding is achieved by melting of the same metal of aluminum. In addition, the negative electrode lead 13
Is formed of copper having a thickness of 80 μm, there is no problem in the bonding property with phosphor bronze. Therefore, the negative electrode connection lead 33 can be formed of phosphor bronze and securely connected by spot welding.

As shown in FIG. 10, the positive electrode connection lead 30 is formed by joining a clad material 30b formed by joining phosphor bronze and aluminum to a base portion 30a made of phosphor bronze by spot welding with the surface of phosphor bronze being aligned. It can also be configured. When joining the positive electrode lead 12 to the positive electrode lead 12 with the aluminum surface of the clad material 30b and spot welding between the clad material 30b and the positive electrode lead 12, the aluminum material is melted and joined,
Reliable joining can be performed.

Next, as shown in FIG. 9A, after the positive electrode lead 12 and the positive electrode connection lead 30 are joined,
As shown in (b), the lead lead-out side 11b of the battery 3
Folded up. The joint between the negative electrode lead 13 and the negative electrode connection lead 33 is similarly bent. Since there is the lead lead-out side 11b between the bent portion and the battery protection device 8, there is no possibility that the positive electrode lead 12 and the negative electrode lead 13 come into contact with the battery protection device 8 to cause an abnormality. Further, by applying an insulating coat to the soldering surface of the circuit board 14 after the soldering of the external output terminals 6a to 6c, insulation can be more reliably ensured.

As described above, in the battery 3, the positive electrode lead 12 and the negative electrode lead 13 are pulled out from one and the same side, and the battery protection device 8 is disposed on the side from which the lead is drawn. 8, there is no lead routing unlike the conventional configuration, and the external output terminal 6a
6c and the battery protection device 8 are fixed at predetermined positions of the lower case 2b, so that the connection between the respective components housed in the pack case 2 is made robust and reliable, and the battery protection device 8 is used as a battery pack 1 for portable equipment. In addition to the thinness of the device, it has robustness.

After each component is accommodated in the lower case 2b by the above-described steps, the upper case 2 is placed in the lower case 2b.
a is joined by ultrasonic welding, and as shown in FIG.
It is assembled into a thin battery pack 1. After this assembly, an inspection probe is inserted into the test terminal windows 29a and 29b to make contact with the test terminals 24a and 24b, and an inspection is performed to determine whether the battery pack 1 operates normally. Test terminal window 29 of battery pack 1 that passed the inspection
A blind sheet is adhered to the recess 35 provided with a, 29b, the joining window 23 and the like, and each opening is closed.

FIG. 11A shows that the battery pack 1 is connected to the lower case 2.
In the plan view seen from the side b, the surface facing the flat surface of the battery 3 is formed to be thin, and an elastic deformation surface 15 that is elastically deformed when the thickness of the battery 3 changes due to expansion is formed. I have. An outer peripheral portion 16 is formed to protrude so as to surround the elastic deformation surface 15. Furthermore, since the elastically deforming surface 15 is formed to be thin, it is possible to prevent the battery 3 from being damaged by piercing with a blade or the like.
A stainless thin plate (metal thin plate) 7 is adhered to a portion of the elastic deformation surface 15 excluding a peripheral portion. At the corner of the stainless steel plate 7, a protruding portion 7a that contacts the outer peripheral portion 16 is formed so that positioning can be performed when the stainless steel plate 7 is attached to the elastic deformation surface 15.

The stainless steel plate 7 has an elastically deformable surface 1.
5 may be adhered to the entire surface of the elastic deformable surface 15 if the thickness of the stainless steel plate 7 is set to the minimum thickness at which the strength against piercing can be obtained. Therefore, the elastic deformation of the elastic deformation surface 15 is not hindered.

FIG. 12 is a cross-sectional view taken along the line AA of FIG. 11A. The elastic deformation surface 15 is formed to be thin with a thickness of 0.22 mm in this configuration. Has an outer peripheral portion 16 formed at a predetermined height. A protruding height of the outer peripheral portion 16 is formed between the top of the outer peripheral portion 16 and the surface of the stainless steel plate 7 adhered to the elastic deformation surface 15 so that a step H is formed. Note that the step H in this configuration is
Is set to 0.4 mm.

In the battery 3, the electrode plate expands due to repeated charge / discharge and aging, and the thickness of the battery 3 increases. Battery 3
When the thickness of the battery 3 increases and exceeds the height of the battery accommodating space between the upper case 2a and the lower case 2b, the pressure due to the expansion of the battery 3 is reduced in thickness and easily deformed. The deformed surface 15 is pushed out and elastically deformed.

Since the expansion of the electrode plate of the battery 3 having the electrode plate laminated structure occurs as a change in the thickness of the entire battery 3, the surface of the elastically deforming surface 15 that comes into contact with the battery 3 is pushed up on average. As shown in FIG. 12 (b), the outer peripheral portion 16 is elastically deformed at the peripheral portion in contact with the outer peripheral portion 16. The thickness of the lithium polymer secondary battery in this configuration was 3.91 mm, and the thickness due to expansion over the entire life after repeated charge / discharge was 4.31 m.
m, and data in which an expansion of 0.4 mm occurs is obtained. As described above, since the space formed by the step H having a height of 0.4 mm and surrounded by the outer peripheral portion 16 is formed on the elastically deformable surface 15, the battery pack 1 can be operated even after the entire life of the battery pack 1 has elapsed. There is no change in the maximum thickness. Also, since the stainless steel plate 7 is adhered to the surface of the elastic deformation surface 15 except for the periphery, the flat state is maintained by the elastic deformation of the surroundings and the flat state is maintained in combination with the average thickness change of the battery 3. Bulges into the outer peripheral portion 16. Therefore, an arc-shaped bulge does not occur due to the expansion of the battery having the conventional configuration, giving a sense of incongruity to the shape of the battery pack, and does not adversely affect the device due to the arc-shaped bulge.

The battery pack 1 having the above-described structure is mounted on a portable telephone 9 as shown in a sectional view in FIG.
Since the battery pack 1 is thinned, the mobile phone 9 itself is also thinned, and the mobile phone 9 is slim enough to be inserted into a pocket. On the opposite side (front side) of the mobile phone 9 on which the battery pack 1 is loaded, a push key 17, a multilayer circuit board 18 having a contact circuit formed by the push key 17, and a support for supporting the multilayer circuit board 18 A plate 19 is provided, a gap between the support plate 19 and the battery pack 1 is about 0.05 mm between the outer peripheral portion 16 and the stainless steel plate 7 adhered on the elastically deformable surface 15. Are provided with a gap of about 0.45 mm.

With this configuration, when a strong pressure is applied from the front side of the mobile phone 9, the outer peripheral portion 16 is
9 serves to support the deformation. In addition, the battery 3 increases in thickness due to expansion of the electrode plate due to charge / discharge or aging, but the elastically deformable surface 15 is elastically deformed in accordance with the expansion of the battery 3 as described above. The change in thickness due to expansion is suppressed in the space formed inside surrounded by 16, and the influence of expansion is not exerted on the device side.

In the above configuration, the dimension of the accommodation space of the battery 3 in the pack case 2 in the thickness direction is set to be slightly larger than the thickness of the battery 3 in consideration of the thickness dimension error of the battery 3. However, since the elastically deformable surface 15 is configured to be elastically deformed, the size of the accommodation space of the battery 3 in the pack case 2 in the thickness direction may be smaller than the thickness of the battery 3. it can. By housing the battery 3 in the pack case 2 formed in this way, the battery 3 is always under pressure from both sides in the compression direction by the elastically deforming surface 15, and the expansion of the electrode plate is suppressed. Effect can be obtained.

When the battery 3 does not expand, it is formed to have a thickness such that the elastic deformation surface 15 does not receive pressure in the compression direction, and when the battery 3 expands, the elastic deformation surface 15 is pressed. The effect of suppressing the expansion of the electrode plate can be obtained even when pressure is applied in the compression direction by the force to be applied.

The expansion of the battery 3 causes the elastic deformation surface 15
When the battery is elastically deformed, if the thickness of the peripheral portion where the amount of deformation is largest is made smaller than the thickness of the other portions, the elastic deformation of the peripheral portion becomes easy, and the followability of the battery 3 to expansion can be improved. Conversely, if the thickness of the peripheral portion is made thicker than the thickness of other portions, it becomes difficult to deform, so that a compressive force is applied to the battery 3 against the expansion of the battery 3 to prevent the electrode plate of the battery 3 from expanding. Pressurization is suppressed, and expansion of the battery 3 can be suppressed.

The configuration of the battery pack 1 described above has been described with respect to an example in which the configuration is applied to a battery power source of a mobile phone.
The same configuration can be applied to a mobile computer, an electronic organizer, a transceiver, and the like.

[0042]

As described above, according to the present invention, by connecting a foil-shaped lead to a mating lead having a different material and thickness via a clad material, the same quality as the foil-shaped lead of the clad material can be obtained. Since the foil-shaped lead can be joined to the surface of the material and joined, stable joining is possible. By applying this lead bonding structure to a battery pack, a foil-shaped lead drawn from a battery is bonded to each component of the battery pack. By interposing the clad material, which is different from the lead on the side, the bonding property is reduced, so that reliable bonding can be performed, and a highly reliable battery pack can be configured.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a battery pack according to an embodiment.

FIG. 2 is a plan view showing a schematic configuration of a battery.

FIG. 3 is a perspective view showing a state in which a battery protection device is provided in a lower case.

FIG. 4 is a perspective view showing a state where a battery protection device and a battery are provided in a lower case.

FIG. 5 is a side view of a lower case showing a configuration of a terminal mounting portion.

FIG. 6 is a cross-sectional view for explaining attachment of an external output terminal and joining with a positive electrode connection lead.

FIG. 7 is a cross-sectional view illustrating a mounting structure of a test terminal.

8A is a plan view and FIG. 8B is a side view showing an arrangement state of the battery protection device.

FIGS. 9A and 9B are cross-sectional views showing a connection between a positive electrode lead and a positive electrode connection lead (a) and a stored state of the lead (b).

FIG. 10 is a cross-sectional view showing another embodiment of the joint structure between the positive electrode connection lead and the positive electrode lead.

11A is a plan view and FIG. 11B is a side view showing a completed state of the battery pack.

FIGS. 12A and 12B are cross-sectional views taken along line AA of FIG. 12A for explaining the deformation of the elastically deformable surface when the battery is expanded, and FIG.

FIG. 13 is a cross-sectional view showing a state where a battery pack is mounted on a mobile phone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery pack 2 Pack case 2a Upper case 2b Lower case 3 Battery 4 Protection circuit (SU) 5 PTC element 6a, 6b, 6c External output terminal 10 Power generation element 11 Exterior case 11b Lead-out side 12 Positive lead 13 Negative lead 30 Negative lead connection 33 negative electrode connection lead 30b clad material

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shigeo Aoki 1006 Kazuma Kadoma, Osaka Prefecture F-term (reference) in Matsushita Electric Industrial Co., Ltd. 5E085 BB17 CC03 EE02 FF08 HH11 JJ50 5H020 AA06 AS06 AS13 AS13 CC06 DD02 DD07 5H022 AA09 AA19 BB12 CC09 CC12

Claims (5)

[Claims] 1. A mating lead for joining a foil lead formed on a foil metal thin plate is formed of a metal material different from that of the foil lead to be relatively thick. In a lead joining structure for joining between superimposed layers, a clad material obtained by rolling and joining a first metal material having good joining compatibility with the foil-like lead and a second metal material having good joining compatibility with the mating lead Are disposed between the foil lead and the mating lead, and the foil lead is melt-bonded between the foil lead and the first metal material and between the mating lead and the second metal material. Characterized in that the lead connection structure is connected to a mating lead. 2. A mating lead for joining a foil lead formed on a foil metal thin plate is formed of a metal material different from that of the foil lead and is relatively thick. In the lead bonding structure for bonding between the superposed layers, a first metal material having good bonding compatibility with the foil lead and a metal material used for the mating lead are roll-bonded to form a clad material. A mating lead is formed of a clad material, and the first metal material of the mating lead and the foil lead are joined to each other so that the foil lead is connected to the mating lead. A lead bonding structure characterized by being made. 3. The lead bonding structure according to claim 1, wherein the clad material is formed of a metal material of the same material as the foil lead and a metal material of the same material as the mating lead. 4. A positive electrode lead and a negative electrode drawn out of the secondary battery, in which a secondary battery, a circuit board having a protection circuit formed thereon, and a battery protection device including a PTC element are housed in a pack case. In a battery pack in which leads are connected to an external output terminal and the battery protection device, the secondary battery is formed by laminating sheet-like positive and negative electrode plates. A positive electrode lead and a negative electrode lead, each of which is formed in a foil shape from a different metal material, are drawn out from one side of the welded and sealed outer casing, and the positive electrode lead and the positive electrode connected to the external output terminal are formed. The same kind of material as that of the positive electrode lead or the negative electrode lead is formed between the opposing leads and / or between the negative electrode lead and the negative electrode counter lead connected to the battery protection device. Battery pack characterized by comprising configured to bonded via a clad material having a metal surface. 5. The battery pack according to claim 4, wherein the positive electrode lead is formed of a clad material having a metal surface of the same kind as a material for forming the positive electrode lead.