JP2012119147A - Battery module and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery module which has improved connection reliability between a wiring layer provided on a circuit board and terminals of a battery.SOLUTION: A battery module 10 comprises: a circuit board 20 having a wiring layer 26 formed on one main surface of an insulating resin layer 24; and a plurality of batteries 30 connected to the circuit board 20. The batteries 30 are connected in series via the wiring layer 26. A cathode terminal 50 and an anode terminal 60 of each of the batteries 30 are bonded to the wiring layer 26 by diffusion bonding.

Description

  The present invention relates to a battery module in which a plurality of batteries are connected in series.

  Generally, the electromotive force of a battery (single cell) is low, and it is about 4 V even in a lithium ion battery that is said to have a high electromotive force. Therefore, when a higher voltage is required, a plurality of batteries are connected in series and modularized.

  As a structure in which a plurality of batteries are modularized (battery module), a structure in which a wiring layer provided on a circuit board for battery monitoring and a battery terminal are connected by solder via a voltage detection line is known ( Patent Document 1).

JP 2010-123299 A

  In the structure in which the wiring layer provided on the circuit board and the battery terminal are connected by soldering, the connection reliability between the wiring layer and the battery terminal is lowered due to aging of the solder, and sufficient vibration resistance is obtained. There was a case that could not be done.

  This invention is made | formed in view of such a subject, The objective is to provide the technique which can improve the connection reliability of the wiring layer provided in the circuit board, and the terminal of a battery.

  One embodiment of the present invention is a battery module. The battery module is provided with a circuit board having a base material and a wiring layer provided on the base material, an electrode body, a housing in which the electrode body is housed, an external body, and an electrical connection to the electrode body. A battery module comprising: an external terminal connected to the external terminal; and the external terminal and the wiring layer are joined by diffusion bonding.

  According to the battery module of this aspect, the connection reliability can be improved because the wiring layer provided on the circuit board and the external terminal of the battery are integrated by diffusion bonding. As a result, the external terminal of the battery is prevented from being detached from the wiring layer due to vibration. Further, since there is no metal interface between the wiring layer and the external terminal of the battery, the resistance can be reduced.

  In the battery module of the above aspect, the joint between the external terminal and the wiring layer may be located at a position outside the region where the housing is projected onto the circuit board.

  One embodiment of the present invention is a method for manufacturing a battery module. The manufacturing method of the battery module includes a step of preparing a battery having an external terminal formed or coated with a metal containing copper as a main component and a circuit board having a wiring layer formed of a metal containing copper as a main component. Filling a solution eluting with copper oxide as a main component between the external terminal and the wiring layer to expose a metal having copper as a main component on the outermost surface of the external terminal and the wiring layer And pressurizing the external terminal and the wiring layer so as to reduce the distance between the external terminal and the wiring layer, and heating the external terminal and the wiring layer in a state where the external terminal and the wiring layer are pressurized. And a step of bonding.

  In the battery module manufacturing method of the above aspect, the solution may be inert to copper. The solution may include a substance having a ligand that forms a complex with copper. The complex may be heat decomposable. Further, the solution may be aqueous ammonia.

  ADVANTAGE OF THE INVENTION According to this invention, the connection reliability of the wiring layer provided in the circuit board and the terminal of a battery can be improved.

It is a disassembled perspective view of the battery module which concerns on embodiment. It is sectional drawing which shows schematic structure of a battery. It is a top view which shows the arrangement | sequence of the battery connected to the circuit board. FIG. 4A is a diagram showing a connection structure between the positive electrode terminal of the battery and the wiring layer of the wiring board. FIG. 4B is a diagram showing a connection structure between the negative electrode terminal of the battery and the wiring layer of the wiring board. FIG. 5A and FIG. 5B are schematic views showing a method for connecting a battery and a circuit board.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  FIG. 1 is an exploded perspective view of a battery module 10 according to an embodiment. The battery module 10 includes a circuit board 20, a plurality of batteries 30, and a housing 40.

  The circuit board 20 includes a metal substrate 22, an insulating resin layer 24, and a wiring layer 26.

  The metal substrate 22 is laminated on one main surface of the insulating resin layer 24. The metal substrate 22 is a member obtained by flattening a metal such as Al or Cu having excellent thermal conductivity, and has a function of improving the heat dissipation of the circuit board 20.

  The insulating resin layer 24 is a “base material” of the circuit board 20, and for example, heat such as melamine derivatives such as BT resin, liquid crystal polymer, epoxy resin, PPE resin, polyimide resin, fluorine resin, phenol resin, polyamide bismaleimide, and the like. A curable resin is exemplified. From the viewpoint of improving the heat dissipation of the circuit board 20, the insulating resin layer 24 desirably has high thermal conductivity. For this reason, it is preferable that the insulating resin layer 24 contains silver, bismuth, copper, aluminum, magnesium, tin, zinc, alloys thereof, and the like as a high thermal conductive filler.

  The wiring layer 26 is formed in a predetermined pattern on the other main surface of the insulating resin layer 24. The wiring layer 26 of the present embodiment is made of copper.

  A chip component 28 is mounted on one main surface of the circuit board 20. The chip component 28 includes a semiconductor element such as an IC and a passive element such as a resistor and a capacitor. The chip component 28 forms a circuit unit that monitors the voltage and temperature of the battery 30 and controls the connection state of the battery 30. More specifically, the circuit unit monitors the voltage and temperature of each battery 30, and when the voltage or temperature indicates abnormality, the circuit unit cuts off only the battery 30 or a plurality of batteries including the battery 30. .

  A battery 30 is connected to one main surface of the circuit board 20. A connection structure between the external terminal of the battery 30 and the wiring layer 26 of the circuit board 20 will be described later.

  The housing 40 is a container-like member that can accommodate the battery 30, and the circuit board 20 is assembled with the surface on which the battery 30 is provided inside the housing 40 so as to close the opening of the housing 40. . By housing the battery 30 in the housing 40, the battery 30 is protected from the external environment.

  FIG. 2 is a cross-sectional view showing a schematic structure of the battery 30. As shown in FIG. 2, the battery 30 includes an outer can (housing) 31 in which an electrode body 32 in which positive and negative electrodes are wound in a spiral shape is housed laterally with respect to the can axis direction of the outer can 31. The opening of the outer can 31 is sealed by the sealing plate 33. The sealing plate 33 is provided with a positive electrode terminal 50 and a negative electrode terminal 60 that protrude outward from the battery 30. The sealing plate 33 is formed with a gas discharge valve (not shown).

  The positive electrode terminal 50 is fitted into the positive electrode opening of the sealing plate 33 while being in contact with the gasket 34. The positive electrode terminal 50 is connected to the positive electrode tab member 53 on the battery inner side of the sealing plate 33. A recess 51 is provided at the end of the positive electrode terminal 50 fitted in the positive electrode opening of the sealing plate 33 such that a side wall is formed along the positive electrode opening of the sealing plate 33. The positive terminal 50 is fixed by caulking so that the edge part of the recessed part 51 spreads. The core part (not shown) of the positive electrode terminal 50 is made of aluminum, and a copper plating layer (not shown) covers the core part. An insulating plate 35 is provided between the positive electrode tab member 53 and the battery inner surface of the sealing plate 33. The insulating plate 35 and the gasket 34 are in contact with each other at the positive electrode opening of the sealing plate 33. Thereby, the positive electrode tab member 53 and the positive electrode terminal 50 are insulated from the sealing plate 33.

  The positive electrode tab member 53 is connected to the positive electrode current collector plate group 32 a protruding from one end face of the electrode body 32. The positive electrode current collector plate group 32 a is a bundle of a plurality of positive electrode current collector plates protruding from one end face of the electrode body 32.

  The negative electrode terminal 60 is fitted into the negative electrode opening of the sealing plate 33 while being in contact with the gasket 34. The negative electrode terminal 60 is connected to the negative electrode tab member 62 inside the sealing plate 33 on the battery side. A recess 61 is formed at the end of the negative electrode terminal 60 fitted in the negative electrode opening of the sealing plate 33 so that a side wall is formed along the negative electrode opening of the sealing plate 33. The negative terminal 60 is fixed by caulking so that the edge part of the recessed part 61 spreads. The entire negative electrode terminal 60 is made of copper. An insulating plate 35 is provided between the negative electrode tab member 62 and the battery inner surface of the sealing plate 33. In the negative electrode opening of the sealing plate 33, the insulating plate 35 and the gasket 34 are in contact with each other. Thereby, the negative electrode tab member 62 and the negative electrode terminal 60 are insulated from the sealing plate 33.

  The negative electrode tab member 62 is connected to the negative electrode current collector plate group 32 b protruding from the other end face of the electrode body 32. The negative electrode current collector plate group 32 b is a bundle of a plurality of negative electrode current collector plates protruding from the other end face of the electrode body 32.

  FIG. 3 is a plan view showing the arrangement of the batteries 30 connected to the circuit board 20. In the present embodiment, a total of ten batteries 30 are divided into five and each form a line. In FIG. 3, the circuit portion formed by the chip component 28 and the wiring for monitoring are not shown.

  The five batteries 30a forming the first row are arranged in parallel at predetermined intervals so that the longitudinal directions of the batteries 30 are substantially parallel. The tip portions of the positive electrode terminal 50 and the negative electrode terminal 60 of the battery 30a protrude from the casing of the battery 30a in the longitudinal direction of the battery 30a. The positive terminal 50 and the negative terminal 60 of the adjacent battery 30a are arranged so as to be opposite to each other. In the first row, the positive terminal 50 of one battery 30a and the negative terminal 60 of the other battery 30a adjacent to each other are connected to a common wiring layer 26a. That is, the wiring layer 26a functions as an interconnector. Thereby, the batteries 30a in the first row are connected in series.

  On the other hand, the five batteries 30b forming the second row are arranged in parallel at predetermined intervals so that the longitudinal directions of the batteries are substantially parallel. The tip portions of the positive electrode terminal 50 and the negative electrode terminal 60 of the battery 30b protrude from the casing of the battery 30b in the longitudinal direction of the battery 30b. The positive electrode terminal 50 and the negative electrode terminal 60 of the adjacent battery 30b are arranged to be opposite to each other. In the second row, the positive terminal 50 of one battery 30b and the negative terminal 60 of the other battery 30b adjacent to each other are connected to a common wiring layer 26b. That is, the wiring layer 26b functions as an interconnector. Thereby, the batteries 30b in the second row are connected in series.

  Further, the negative terminal 60 ′ serving as one terminal of the series connection of the batteries 30a forming the first row and the positive terminal 50 ′ serving as one terminal of the series connection of the batteries 30b forming the second row are common. It is connected to the wiring layer 26c. As a result, the battery 30a forming the first row and the battery 30b forming the second row are connected in series. The positive terminal 50 ″, which is one end of the series connection of the batteries 30 a forming the first row, is connected to the wiring layer 26 d. Further, the negative terminal 60 ″ serving as one end of the series connection of the batteries 30 b forming the second row is connected to the wiring layer 26 e. Wirings are routed from the wiring layers 26d and 26e to the outside of the circuit board 20, and can be connected to an external load.

  FIG. 4A is a diagram illustrating a connection structure between the positive terminal 50 of the battery 30 and the wiring layer 26 of the circuit board 20. FIG. 4B is a diagram showing a connection structure between the negative electrode terminal 60 of the battery 30 and the wiring layer 26 of the circuit board 20.

  As shown in FIG. 4A, the connecting portion of the positive electrode terminal 50 includes a core part 52 made of aluminum and a surface layer part 54 made of copper covering the periphery of the core part 52. The surface layer portion 54 is a plating layer formed around the core portion 52. The surface layer portion 54 and the wiring layer 26 are joined by diffusion bonding. Since the surface layer portion 54 and the wiring layer 26 are integrated by diffusion bonding, there is no interface between them. On the other hand, as shown in FIG. 4B, the connection portion of the negative electrode terminal 60 is formed of copper. The negative electrode terminal 60 and the wiring layer 26 are joined by diffusion bonding. Since the negative electrode terminal 60 and the wiring layer 26 are integrated by diffusion bonding, there is no interface between them.

  According to the battery module 10 described above, the battery external terminals (the positive electrode terminal 50 and the negative electrode terminal 60) and the wiring layer 26 of the circuit board 20 are joined by diffusion bonding, thereby providing an integrated structure. The connection reliability between the external terminal and the wiring layer 26 can be improved. As a result, it is possible to prevent the external terminals of the battery from being detached from the wiring layer 26 due to vibration. Moreover, since there is no metal interface between the external terminal of the battery and the wiring layer 26, the resistance can be reduced.

(Battery module manufacturing method)
Among the battery module manufacturing methods, in particular, a method for connecting a battery and a circuit board will be described with reference to FIGS. 5 (A) and 5 (B). In FIGS. 5A and 5B, one row of batteries 30 is shown for ease of explanation.

  First, the surface of the core portion of the positive electrode terminal made of aluminum is coated with copper using a plating method to form a surface layer portion. The battery 30 as shown in FIG. 3 is formed by using the positive electrode terminal obtained by covering the core with a metal containing copper as a main component and the negative electrode terminal formed using a metal containing copper as a main component. . In addition, the outermost surfaces of the positive electrode terminal and the negative electrode terminal of the battery 30 are formed of an oxide containing copper oxide as a main component by spontaneous oxidation of copper in the atmosphere. Here, in the expressions “mainly composed of copper” and “mainly composed of copper oxide”, “mainly composed” means that the content of copper or copper oxide is larger than 50%. .

  Next, as shown in FIG. 5A, with the predetermined position of the wiring layer 26 and the positive electrode terminal 50 and the negative electrode terminal 60 of the battery 30 aligned, and between the positive electrode terminal 50 and the wiring layer 26, and A solution (not shown) in which copper oxide is eluted or dissolved is filled between the negative electrode terminal 60 and the wiring layer 26. In the present embodiment, the solution is aqueous ammonia. The distance between the positive electrode terminal 50 and the wiring layer 26 when the solution is filled between the positive electrode terminal 50 and the wiring layer 26 is, for example, 1 μm. Similarly, the distance between the negative electrode terminal 60 and the wiring layer 26 is, for example, 1 μm.

When left at room temperature for about 1 minute, the copper oxide formed on the outermost surfaces of the positive electrode terminal 50 and the negative electrode terminal 60 is eluted in the solution, and the copper oxide disappears from the outermost surface of the positive electrode terminal 50. Moreover, the copper oxide formed in the outermost surface of the wiring layer 26 used as a junction part elutes in a solution, and copper oxide lose | disappears from the outermost surface of the wiring layer 26 used as a junction part. By elution of copper oxide into the solution, copper is exposed on the outermost surfaces of the positive electrode terminal 50 and the negative electrode terminal 60 and the corresponding outermost surface of the wiring layer 26. Moreover, a copper complex is formed in the solution. In the present embodiment, the copper complex is considered to exist as a thermally decomposable tetraammine copper complex ion represented by [Cu (NH ₃ ) ₄ ] ²⁺ . In addition, since ammonia water is inactive with respect to copper, the copper which comprises the positive electrode terminal 50, the negative electrode terminal 60, and the wiring layer 26 remains without reacting with ammonia water.

  Next, as shown in FIG. 5B, a positive electrode is used to reduce the distance between the positive electrode terminal 50 and the wiring layer 26 and the distance between the negative electrode terminal 60 and the wiring layer 26 using a press machine. The terminal 50 and the wiring layer 26 are pressurized. Similarly, the negative electrode terminal 60 and the wiring layer 26 are pressurized using a press. The pressure at the time of pressurization is 1 MPa, for example. In the present embodiment, the tip portions of the positive electrode terminal 50 and the negative electrode terminal 60 of the battery 30 protrude from the casing of the battery 30 in the longitudinal direction of the battery 30. In other words, the joint portion between the positive electrode terminal 50 and the wiring layer 26 and the joint portion between the negative electrode terminal 60 and the wiring layer 26 are positioned away from the region where the casing of the battery 30 is projected onto the circuit board 20. For this reason, when pressing is performed on the positive electrode terminal 50 and the negative electrode terminal 60, the casing of the battery 30 does not become an obstacle, and the positive electrode terminal 50 and the negative electrode terminal 60 can be pressed directly.

  Next, components other than copper in the solution are heated by heating the positive electrode terminal 50 and the wiring layer 26 and the negative electrode terminal 60 and the wiring layer 26 under a relatively low temperature condition of 200 ° C. to 300 ° C. Is removed to precipitate or recrystallize copper. In the present embodiment, the moisture evaporates by heating, and the tetraammine copper complex ions are thermally decomposed to evaporate the ammonia component. Thereby, the ratio of copper in the solution gradually increases, and the distance between the outermost surface of the positive electrode terminal 50 and the outermost surface of the wiring layer 26 gradually approaches due to pressurization by a press. Similarly, the distance between the outermost surface of the negative electrode terminal 60 and the outermost surface of the wiring layer 26 gradually approaches.

  Next, when the removal of components other than copper in the solution is completed, the outermost surface of the positive electrode terminal 50 and the outermost surface of the wiring layer 26 are joined by precipitated copper made of copper derived from copper oxide. Similarly, the outermost surface of the negative electrode terminal 60 and the outermost surface of the wiring layer 26 are joined by deposited copper made of copper derived from copper oxide. This deposited copper is excellent in orientation and stability. After the joining with the precipitated copper is completed, the heating is stopped and the joined portion with the precipitated copper is gradually cooled to about room temperature. The time from the start of heating to the stop of heating is, for example, 10 minutes. After the cooling is completed, the pressure is released, and the joining process of the positive electrode terminal 50 and the wiring layer 26 and the negative electrode terminal 60 and the wiring layer 26 is completed.

  In the junction structure shown in FIG. 4, the virtual boundary between the positive electrode terminal 50 and the wiring layer 26 coincides with the surface extending from the outermost surface of the wiring layer 26, but as described above, the positive electrode By pressing the terminal 50, the virtual boundary between the positive electrode terminal 50 and the wiring layer 26 can be pushed into the wiring layer 26 with respect to the surface extending the outermost surface of the wiring layer 26. is there. Similarly, the virtual boundary between the negative electrode terminal 60 and the wiring layer 26 may be pushed into the wiring layer 26 with respect to the surface extending the outermost surface of the wiring layer 26.

  According to the battery module manufacturing method described above, the external terminals of the battery 30 and the wiring layer 26 of the circuit board 20 can be joined under relatively low temperature conditions without using a large-scale facility such as a vacuum apparatus. . Specifically, the joint surface of the external terminal of the battery 30 and the joint surface of the wiring layer 26 are activated and then joined through the deposited copper. As a result, voids and by-products are prevented from being generated between the external terminals of the battery 30 and the wiring layer 26, so that the connection reliability between the external terminals of the battery 30 and the wiring layer 26 is improved. be able to.

  In addition, as the deposited copper responsible for joining the external terminal of the battery 30 and the wiring layer 26, copper derived from copper oxide that was present as an oxide film on the outermost surface of the external terminal of the battery 30 and the wiring layer 26 is used. Therefore, it is not necessary to separately prepare a bonding material in order to bond the external terminal of the battery 30 and the wiring layer 26. For this reason, the cost required for the connection between the external terminal of the battery 30 and the wiring layer 26 can be reduced.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added based on the knowledge of those skilled in the art. The form can also be included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Battery module, 20 Circuit board, 22 Metal substrate, 24 Insulation resin layer, 26 Wiring layer, 30 Battery, 31 Exterior can, 32 Electrode body, 50 Positive electrode terminal, 60 Negative electrode terminal

Claims (7)

A circuit board having a base material and a wiring layer provided on the base material;
A battery having an electrode body, a housing in which the electrode body is accommodated, and an external terminal provided outside the housing and electrically connected to the electrode body;
With
The battery module, wherein the external terminal and the wiring layer are joined by diffusion bonding.   2. The battery module according to claim 1, wherein a joint portion between the external terminal and the wiring layer is located away from a region where the housing is projected onto the circuit board. Preparing a battery having an external terminal formed or coated with a metal mainly composed of copper, and a circuit board having a wiring layer formed of a metal mainly composed of copper;
Filled between the external terminal and the wiring layer is a solution from which an oxide mainly composed of copper oxide is eluted, and exposes the metal mainly composed of copper on the outermost surface of the external terminal and the wiring layer. A process of
Pressurizing the external terminal and the wiring layer so as to reduce the distance between the external terminal and the wiring layer;
Bonding the external terminal and the wiring layer by heating in a state where the external terminal and the wiring layer are pressurized;
A method for manufacturing a battery module, comprising:   The method for producing a battery module according to claim 3, wherein the solution is inert to copper.   The method for manufacturing a battery module according to claim 3 or 4, wherein the solution contains a substance having a ligand that forms a complex with copper.   The method for producing a battery module according to claim 5, wherein the complex is heat decomposable.   The method for manufacturing a battery module according to claim 3, wherein the solution is aqueous ammonia.

Images