Patent Description:
In general, an electronic device, such as a notebook computer, a mini notebook computer, a net book, a mobile computer, an ultramobile personal computer (UMPC) or a portable multimedia player (PMP), uses a battery pack as a portable power source, and the battery pack may have a plurality of battery cells connected in series and/or in parallel. The battery pack may include a protective circuit module (PCM) for protecting battery cells against over-charge, over-discharge, and/or over-current. The battery cells and the PCM may be housed together in a case. <CIT> describes a secondary battery including a circuit board unnecessitating a cut-out portion. The secondary battery includes a battery cell having a cell tab, a protective circuit module electrically connected to the cell tab and having a circuit pattern formed therein, and a connection tab attached to the protective circuit module and electrically connected to the circuit pattern, wherein the connection tab includes a conductive layer adhered to the protective circuit module and including a first plating layer formed on the conductive layer and a second plating layer formed on the first plating layer, and the cell tab is welded to the connection tab.

Embodiments of the present disclosure provide a battery pack which can observe welding quality from its appearance while preventing a circuit board from being damaged when laser beam welding is performed in a state in which a protective circuit module and battery cells are mounted on a frame.

These and other aspects and features of the present disclosure will be described in or will be apparent from the following description of exemplary embodiments of the present disclosure.

According to an aspect of the present disclosure, a battery pack is provided as set out in claim <NUM>, preferred embodiments are defined in dependent claims <NUM>-<NUM>.

According to another aspect of the invention, there is provided a method of forming a battery pack as set out in claim <NUM>.

The battery pack according to the present disclosure can prevent a circuit board from being damaged when laser beam welding is performed in a state in which the battery cell and the protective circuit module are mounted in a frame.

In addition, the battery pack according to the present disclosure can inspect welding quality from its appearance during welding of the electrode tab.

Hereinafter, embodiments of the present disclosure will be described in detail. The subject matter of the present disclosure, however, may be embodied in many different forms and should not be construed as being limited to the example (or exemplary) embodiments set forth herein. Rather, these example embodiments are provided so that this disclosure will be thorough and complete and will convey the aspects and features of the present disclosure to those skilled in the art.

<FIG> is a perspective view of a battery pack according to an embodiment of the present disclosure. <FIG> is an exploded perspective view of the battery pack shown in <FIG>.

As shown in <FIG> and <FIG>, the battery pack <NUM> of the present disclosure may include battery cells <NUM>, a protective circuit module <NUM> electrically connected to the battery cells <NUM>, a frame <NUM> accommodating the battery cells no and the protective circuit module <NUM> together, and a cover <NUM> covering the battery cells <NUM>, the protective circuit module <NUM> and the frame <NUM>.

<FIG> is an enlarged perspective view illustrating a state in which battery cells, a protective circuit module and a frame are coupled to one another in the battery pack shown in <FIG>. <FIG> is an enlarged perspective view of a battery cell shown in <FIG>. Hereinafter, a configuration of the battery pack shown in <FIG> and <FIG> will be described with reference to <FIG>.

Each of the battery cells <NUM> may be configured such that an electrode assembly (not shown) and an electrolyte (not shown) are accommodated in a case <NUM>. The electrode assembly may be fabricated by stacking a stacked structure having a separator positioned between a positive electrode plate and a negative electrode plate or winding the stacked structure in a jelly-roll configuration. The electrode assembly may be sealed after being accommodated in the case <NUM> with the electrolyte. The thus configured battery cell <NUM> may be a pouch-type secondary battery having the electrode assembly accommodated in the pouch-type case <NUM>. The battery cell <NUM> may include a first electrode tab <NUM> protruding from a front surface and electrically connected to the negative electrode plate and a second electrode tab <NUM> spaced a predetermined distance apart from the first electrode tab <NUM>, outwardly protruding from the front surface and electrically connected to the positive electrode plate. For example, the first electrode tab <NUM> may be a first tab, and the second electrode tab <NUM> may be a second tab, but aspects of the present disclosure are not limited thereto. Polarities of the first electrode tab <NUM> and the second electrode tab <NUM> may be reversed.

The battery cell <NUM> may have the first electrode tab <NUM> outwardly extending and protruding through a planar portion 111a provided in the case <NUM>.

The construction of the second electrode tab <NUM> will be described in detail below, but in essence the second electrode tab <NUM> comprises a lead plate 115a electrically connected to an electrode tab portion <NUM> which protrudes through the planar portion 111a but is bent back on itself.

The case <NUM> may consist of an upper pouch and a lower pouch, which are prepared by folding a rectangular pouch film in a lateral direction x. In addition, the case <NUM> may have a planar portion 111a and welding portion 111b, which are created by fusing and bonding the upper pouch and the lower pouch.

The welding portions 111b may mean portions extending a predetermined length in the lateral direction x from opposite sides of the case <NUM> and bent toward the upper pouch to then be adhered and fixed to the side portions of the case <NUM>.

The planar portion 111a may mean a planarly extending portion that outwardly extends in a back-and-forth direction y of the battery cell <NUM>. In addition, the planar portion 111a may be a portion from which the first electrode tab <NUM> and the electrode tab portion <NUM> protrude. In addition, insulation tapes 112a and 113a may further be positioned for achieving insulation between the case <NUM> and the electrode tab portion <NUM> and between the case <NUM> and the first electrode tab <NUM>, respectively.

The battery cell <NUM> may have the electrode tab portion <NUM> bent twice upward and toward the planar portion 111a so as to be parallel with the planar portion 111a. In addition, an end of the electrode tab portion <NUM> parallel with the planar portion 111a may be electrically connected to a temperature sensing element <NUM>. Here, the temperature sensing element <NUM> may be positioned on the planar portion 111a. In addition, the temperature sensing element <NUM> may include a temperature cut-off element 114a, and a first tab 114b and a second tab 114c electrically connected to opposite sides of the TCO 114a. Here, when a temperature of the battery cell <NUM> exceeds a reference value, the TCO 114a may operate as a fuse that cuts off current. The temperature sensing element <NUM> may have the first tab 114b brought into contact with and coupled to the electrode tab portion <NUM> and the second tab 114c brought into contact with and coupled to a lead plate 115a that is a metal plate that functions as an electrode tab <NUM> for the purpose of making external connections. Here, the first tab 114b and the second tab <NUM> may be a metal or an equivalent thereof. For example, the temperature sensing element <NUM> may be electrically connected between the electrode tab portion <NUM> and the lead plate 115a.

In the present disclosure, the temperature sensing element <NUM> is configured to be connected to the battery cell <NUM>. However, the temperature sensing element <NUM> may be provided in the protective circuit module <NUM>. Here, the second electrode tab <NUM> and the first electrode tab <NUM> of the battery cell <NUM> may be electrically connected to the protective circuit module <NUM>, respectively.

The lead plate 115a outwardly extends from the planar portion 111a in the back-and-forth direction y to then be substantially parallel with the first electrode tab <NUM>. The lead plate 115a may be made of a metal or an equivalent thereof. The lead plate 115a may be electrically connected to the electrode tab portion <NUM> through the temperature sensing element <NUM>. In addition, the temperature sensing element <NUM> and the second electrode tab <NUM> may be covered by an insulation tape <NUM> with the planar portion 111a, thereby being fixed and electrically protected. In addition, the lead plate 115a (second electrode tab) and the first electrode tab <NUM> may be welded to the protective circuit module <NUM> to then be electrically connected to the protective circuit module <NUM>. In the following description and claims, for the sake of convenient explanation, references to the electrode tabs of the battery cell <NUM> are references to the first electrode tab <NUM> and the lead plate 115a, since these are the parts which are coupled to the electrode tab coupling portions <NUM>, <NUM>.

In addition, the battery cell <NUM> shown in <FIG> may be inverted such that the temperature sensing element <NUM> is positioned under the planar portion 111a, to then be received in the frame <NUM>. The battery cell <NUM> may be mounted in a cell mount portion 130a of the frame <NUM>.

The battery cell <NUM> may include a plurality of battery cells <NUM> mounted in the frame <NUM> such that side surfaces of adjacent ones of the battery cells <NUM> are positioned to face each other. Here, since the welding portions 111b are fixed to side portions of the battery cell <NUM> using a tape 110x, the battery cell <NUM> can be easily injected or ejected into/from the frame <NUM>. In addition, after the battery cell <NUM> are mounted in the frame <NUM>, the battery cell <NUM> may have side portions adhered to top surfaces of adjacent ones of the battery cells <NUM> so as to facilitate handling, to then be coupled and fixed. Here, opposite side surfaces of each of the battery cells <NUM> are surfaces fixed at the welding portions 111b using the tape 110x and extending in the back-and-forth direction y. Four battery cells <NUM> arranged such that side surfaces of two of the four battery cells <NUM> face each other are shown in <FIG>, but the present disclosure is not limited to the numbers in the illustrated embodiment. The plurality of battery cells <NUM> may be positioned sequentially side-by-side in the lateral direction x. For example, one of the battery cells <NUM> may be positioned such that its side surfaces face its adjacent battery cells <NUM>.

The protective circuit module <NUM> may be mounted in a module mount portion 130b of the frame <NUM>. The module mount portion 130b may be positioned between a front wall 131a and the cell mount portion 130a in the frame <NUM>. The protective circuit module <NUM> may be mounted in a module support portion <NUM> provided in the module mount portion 130b. In addition, the protective circuit module <NUM>, which is shaped of a plate extending in the lateral direction x along the front wall 131a of the frame <NUM>, may be positioned between the front wall 131a of the frame <NUM> and the battery cell <NUM> and may have a predetermined width in the back-and-forth direction y. Here, the battery cells <NUM> may be positioned in the rear of the protective circuit module <NUM>.

The protective circuit module <NUM> includes the plate-shaped, or planar, circuit board <NUM> having a plurality of wire patterns. The circuit board <NUM> shaped of a plate may extend in the lateral direction x along the front wall 131a of the frame <NUM>. In addition, the circuit board <NUM> may further include a plurality of protection devices (not shown) electrically connected to the plurality of wire patterns. In addition, the protective circuit module <NUM> may further include electrode tab coupling portions <NUM> and <NUM> connected to the opposite-side electrode tabs <NUM> and <NUM> of the battery cells <NUM>. The electrode tab coupling portions <NUM> and <NUM> may be electrically connected to the wire patterns provided in the circuit board <NUM>. In addition, the electrode tab coupling portions <NUM> and <NUM> may electrically connect in series or in parallel each of the plurality of battery cells <NUM> by the wire patterns provided in the circuit board <NUM>.

In addition, the circuit board <NUM> may be electrically connected to a connector <NUM> that is outwardly exposed and protruded. The protective circuit module <NUM> may be electrically connected to the exterior through the connector <NUM> and may control charge and discharge operations of the battery cells <NUM>.

The electrode tab coupling portions <NUM> and <NUM> to be electrically connected to the battery cells <NUM> may be mounted on the top surface of the circuit board <NUM>. The electrode tab coupling portions <NUM> and <NUM> may include a first electrode tab coupling portion <NUM> and a second electrode tab coupling portion <NUM>. The circuit board <NUM> may include a plurality of electrode tab coupling portions <NUM> and <NUM> electrically connected to the plurality of battery cells <NUM>, respectively. In addition, the plurality of electrode tab coupling portions <NUM> and <NUM> may be positioned to be spaced apart from one another in the lateral direction x. In addition, the plurality of electrode tab coupling portions <NUM> and <NUM> are positioned to correspond to the opposite-side electrode tabs <NUM> and <NUM> of the battery cells <NUM>.

Here, the first electrode tab coupling portion <NUM> may be electrically connected to the first electrode tab <NUM> of the battery cell <NUM> by laser beam welding, and the second electrode tab coupling portion <NUM> may be electrically connected to the lead plate 115a (second electrode tab <NUM>) of the battery cell <NUM> by laser beam welding. Such welding will now be described in detail.

The frame <NUM> may define assembled positions of the battery cells <NUM> and the protective circuit module <NUM>. The frame <NUM> may be made of an insulating material, such as, for example, a polymer compound molded by heat or a pressure. The frame <NUM> may enclose the battery cells <NUM> and the protective circuit module <NUM> positioned within the frame <NUM> and may include outer walls <NUM> shaped of a rectangular ring extending in an up-and-down direction z, which is a thickness direction of the frame <NUM>.

The frame <NUM> may include the module mount portion 130b provided at a region adjacent to the front wall 131a among four outer walls <NUM> and cell mount portion 130a provided at the rear of the module mount portion 130b. In the frame <NUM>, the cell mount portion 130a and the module mount portion 130b may be provided within a region enclosed by the outer walls <NUM>. The front wall 131a may be a surface having a connector hole 131aa allowing the connector <NUM> of the protective circuit module <NUM> to be outwardly exposed and protruded.

Here, both of a top surface and a bottom surface of the frame <NUM> may be opened on the cell mount portion 130a. In addition, the frame <NUM> may have a bottom surface <NUM> on the module mount portion 130b. That is to say, the bottom surface <NUM> may be provided at a region of the frame <NUM>, which is adjacent to the front wall 131a. In addition, the module support portion <NUM> upwardly protruding to support the protective circuit module <NUM> may be provided on the bottom surface <NUM> of the module mount portion 130b of the frame <NUM>.

The frame <NUM> may have the bottom surface <NUM> provided on the module mount portion 130b, which is a region of the front wall 131a. In addition, the module support portion <NUM> provided in the module mount portion 130b may be brought into contact with a bottom surface of the circuit board <NUM>. Here, the module support portion <NUM> may have a height smaller than that of the outer walls <NUM> of the frame <NUM>. The module support portion <NUM> may include a plurality of module support portions located at a plurality of regions of the module mount portion 130b to support the protective circuit module <NUM> at a plurality of locations so as to be securely mounted. In addition, the module support portion <NUM> may further include a rib <NUM> supporting the circuit board <NUM> in contact with the bottom surface of the circuit board <NUM> at a region adjacent to a board throughhole 121a of the circuit board <NUM>. The rib <NUM> may be provided to withstand a pressure applied when the battery cell <NUM> and the protective circuit module <NUM> are welded.

The cover <NUM> may be installed to cover the top and bottom surfaces of the frame <NUM> having the battery cells <NUM> and the protective circuit module <NUM> mounted thereon. The cover <NUM> may include an upper cover <NUM> and a lower cover <NUM>. The upper cover <NUM> may be coupled to the frame <NUM> from above so as to cover the top surface of the battery cell <NUM> and the top surface of the protective circuit module <NUM>. The lower cover <NUM> may be coupled to the frame <NUM> from below so as to cover the bottom surface of the battery cell <NUM> and the bottom surface <NUM> of the frame <NUM>. The battery cell <NUM> and the protective circuit module <NUM> may be accommodated inside the frame <NUM> and the cover <NUM>. The cover <NUM> may provide protection for the battery cell <NUM> and the protective circuit module <NUM> from external elements and/or environmental exposure.

<FIG> is a cross-sectional view taken along the line <NUM>-<NUM> of <FIG>. For brevity, the frame <NUM> positioned under the protective circuit module <NUM> is not shown in <FIG>. However, as described above, the circuit board <NUM> may be welded to the battery cells <NUM> in a state in which the battery cells <NUM> are mounted in the frame <NUM>. Specifically, the rib <NUM> positioned under the frame <NUM> may support a bottom portion of the circuit board <NUM>.

The protective circuit module <NUM> is fixed by connecting the first electrode tab coupling portion <NUM> onto the circuit board <NUM> using a conductive adhesion member 121a. Here, the conductive adhesion member 121a may be prepared using a general solder. The conductive adhesion member 121a is provided along edges of a bottom surface, except for a central region, of the first electrode tab coupling portion <NUM>. Accordingly, a space is created between the central region of the first electrode tab coupling portion <NUM> and the circuit board <NUM>. The protection layer <NUM> is further be positioned in the space. Specifically, the protection layer <NUM> may have an area corresponding to the first electrode tab <NUM> located on the first electrode tab coupling portion <NUM>. Therefore, irrespective of places of the first electrode tab <NUM>, into which laser beam L is irradiated, the circuit board <NUM> can be covered by the protection layer <NUM> when performing welding for coupling the first electrode tab <NUM> to the first electrode tab coupling portion <NUM> of the circuit board <NUM>. During general laser beam welding, the laser beam L penetrates a material to be welded to then reach the circuit board positioned under the material, causing damage to the circuit board. In the battery pack <NUM> according to the embodiment of the present disclosure, however, even when the laser beam L for welding the first electrode tab <NUM> with the first electrode tab coupling portion <NUM> penetrates into the first electrode tab coupling portion <NUM>, the underlying protection layer <NUM> may block the laser beam L, thereby preventing the circuit board <NUM> from being damaged by the laser beam L.

The first electrode tab coupling portion <NUM> may have a larger area than the first electrode tab <NUM>. Accordingly, the first electrode tab coupling portion <NUM> can extend more than the first electrode tab <NUM> on the circuit board <NUM> to then be exposed. Therefore, when the first electrode tab <NUM> is mounted on the first electrode tab coupling portion <NUM> and welding is then performed, it can be visually inspected whether welding is being conducted at an accurate position.

The protection layer <NUM> may include one or more materials selected from the group consisting of gold, aluminum, iron, platinum, molybdenum, tantalum and chrome, or an alloy thereof, which can be fabricated as a thin film.

In the aforementioned embodiment, for brevity, the protection layer <NUM> located under a portion where the first electrode tab <NUM> and the first electrode tab coupling portion <NUM> are coupled to each other has been shown and described. However, protection layers may also be located under a portion where the second electrode tab <NUM> (lead plate 115a) and the second electrode tab coupling portion <NUM> are coupled to each other. In this case, the protection layers may include the same material as the protection layer <NUM> located under the first electrode tab <NUM>, but may optionally include a different material from the protection layer <NUM>.

Hereinafter, a configuration of a battery pack according to another embodiment of the present disclosure will be described.

<FIG> is an enlarged perspective view of a battery pack according to another embodiment of the present disclosure. <FIG> are cross-sectional views taken along the line <NUM>-<NUM> of <FIG>.

The battery pack according to another embodiment of the present disclosure may include a battery cell <NUM>, a protective circuit module <NUM> electrically connected to the battery cell <NUM>, a frame (not shown) accommodating the battery cell <NUM> and the protective circuit module <NUM>, and a cover (not shown) covering the battery cell <NUM>, the protective circuit module <NUM> and the frame.

Referring to <FIG>, <FIG>, the protective circuit module <NUM> may include a protection layer <NUM> further extending from a first electrode tab coupling portion <NUM> along a surface of the circuit board <NUM> to then be exposed.

The protection layer <NUM> may include a first layer 224a for protecting the circuit board <NUM> from laser beams and a second layer 224b covering the first layer 224a.

The first layer 224a may include the same material as the protection layer <NUM> according to the previous embodiment of the present disclosure, including, for example, one or more materials selected from the group consisting of gold, aluminum, iron, platinum, molybdenum, tantalum and chrome, or an alloy thereof.

The second layer 224b may cover at least a top surface of the first layer 224a. For example, the second layer 224b located only on the top surface of the first layer 224a is shown in <FIG>, and the second layer 224b covering the top and bottom surfaces and side surfaces of the first layer 224a is shown in <FIG>. When the second layer 224b covers at least the top surface of the first layer 224a, welding quality can be visually inspected through the exposed second layer 224b. In detail, the second layer 224b may be exposed at an upper portion of the circuit board <NUM>. In addition, the second layer 224b may include a material, the color of which varies according to the temperature. In detail, when laser beam welding is performed by applying laser beams from upper portions of the first electrode tab <NUM> and the first electrode tab coupling portion <NUM>, heat derived from welding may be transferred to the protection layer <NUM> positioned under the first electrode tab coupling portion <NUM>, thereby changing the color of the second layer 224b of the protection layer <NUM>. In addition, the operator can visually inspect whether welding has been stably conducted by identifying a change in the color of the second layer 224b. Here, since the laser beam used in the welding is blocked by the first layer 224a, welding quality can be observed through the color change of the second layer 224b without a separate process while preventing the circuit board <NUM> from being damaged, thereby securing an increased operation speed and reliability.

To achieve this, the second layer 224b may include a thermochromic ink, the color of which varies according to welding heat. In addition, usable examples of the thermochromic ink used for the second layer 224b may include a thermocolor ink, a silk ink or a photo solder resist (PSR) ink. Specifically, the thermocolor ink may be selected from materials changing their colors at a temperature of the protection layer <NUM> ranging from <NUM> to <NUM> during laser beam welding.

Specifically, the thermocolor ink is a material having a dielectric constant varied with the temperature, consequently undergoing a change in the displayed color, and may generally be referred to a temperature sensing ink or a chameleon ink. In addition, if the thermocolor ink exists in both of a reversible version or an irreversible version according to whether to revert back to its original color, the reversible thermocolor ink and irreversible thermocolor ink can be both employed as the second layer 224b. In detail, one of three types of ink, including a metallic complex ink, a cholesteric liquid crystal ink, and a Metamo (metamorphosis) color ink, can be used as the reversible ink, and a thermo color ink can be used as the irreversible thermocolor ink. Therefore, if the second layer 224b is prepared by coating the thermocolor ink, the operator can determine that the second electrode tab <NUM> and the second electrode tab coupling portion <NUM> have been stably welded to each other based on the color change.

Meanwhile, the silk ink and the PSR ink, which are widely used in the manufacture of a PCB, indicate a white colorant and a green colorant, respectively, and have a particle size of less than <NUM>, making it advantageous to fabricate the second layer 224b as a thin film. However, if the heat applied during laser beam welding is transferred to the silk ink or the PSR ink, a color change may occur. In particular, the inventor of the present disclosure discovered that the color change occurred in a temperature range of between <NUM> and <NUM>. Therefore, when the second layer 224b is prepared by coating the silk ink or the PSR ink, the color change can be visually observed by the operator, and based on the color change, the operator can determine that the welding between the second electrode tab <NUM> and the second electrode tab coupling portion <NUM> has been stably conducted.

In addition, when the second layer 224b is prepared by coating the thermocolor ink, the operator can also determine based on the color change that the welding between the second electrode tab <NUM> and the second electrode tab coupling portion <NUM> has been stably conducted.

In addition, in order to allow the operator to easily observe the color change of the second layer 224b, the protection layer <NUM> can be configured to extend a predetermined length (<NUM>) from the second electrode tab coupling portion <NUM> along the surface of the circuit board <NUM> to then be exposed.

Here, the extending length (<NUM>) of the protection layer <NUM> may be in a range from <NUM> to <NUM>. If the extending length (<NUM>) of the protection layer <NUM> is greater than or equal to <NUM>, the protection layer <NUM> is exposed from the second electrode tab coupling portion <NUM> even if there is a slight misalignment between the second electrode tab coupling portion <NUM> and the protection layer <NUM> during welding, thereby allowing the operator to easily observe welding quality by visual inspection. In addition, if the extending length (<NUM>) of the protection layer <NUM> is less than or equal to <NUM>, the heat generated during laser beam welding can be sufficiently transferred to the protection layer <NUM>, thereby ensuring the color change of the protection layer <NUM> by exposure to the heat.

The extending length (<NUM>) of the protection layer <NUM> is preferably in a range from <NUM> to <NUM>. If the extending length (<NUM>) of the protection layer <NUM> is less than or equal to <NUM>, a color changing effect by the heat derived from laser beams can be enhanced. Therefore, the operator can more easily determine, by visual inspection, that the welding has been stably conducted.

Hereinafter, a battery pack according to still another embodiment of the present disclosure will be described.

<FIG> is an enlarged perspective view of a battery pack according to still another embodiment of the present disclosure. <FIG> is a plan view illustrating a conductive pattern provided on a protective circuit module shown in <FIG> in a state in which a second electrode tab is not coupled to the protective circuit module.

The battery pack according to still another embodiment of the present disclosure may include battery cells <NUM>, a protective circuit module <NUM> electrically connected to the battery cell <NUM>, a frame <NUM> accommodating the battery cell <NUM> and the protective circuit module <NUM>, and a cover <NUM> covering the battery cell <NUM>, the protective circuit module <NUM> and the frame <NUM>.

Referring to <FIG> and <FIG>, the protective circuit module <NUM> may include a protection layer <NUM> further extending from a first electrode tab coupling portion <NUM> along a surface of the circuit board <NUM> to then be exposed.

The protection layer <NUM> may include a first layer 324a for protecting the circuit board <NUM> from laser beams and a second layer 324b extending from the first layer 324a to then be exposed.

The first layer 324a may include the same material as the protection layer <NUM> according to the previous embodiment of the present disclosure, including, for example, one or more materials selected from the group consisting of gold, aluminum, iron, platinum, molybdenum, tantalum and chrome, or an alloy thereof.

The second layer 324b may include a material, the resistance of which varies according to the heat transferred during laser beam welding. As an example, the second layer 324b may include the same material as the protection layer <NUM> or the first layer 324a, including, for example, one or more materials selected from the group consisting of gold, aluminum, iron, platinum, molybdenum, tantalum and chrome, or an alloy thereof. As another example, the second layer 324b may include an insulating material, and a PSR ink may be coated on the second layer 324b. As discussed above, the PSR ink, which is widely used in the manufacture of a PCB, has a particle size of less than <NUM>, making it advantageous to fabricate the second layer 324b as a thin film. In addition, not only the color but also the resistance of the PSR ink vary according to the heat generated during welding, the PSR ink can be applied for use in the second layer 324b. Representative usable examples of the PSR ink may include PSR-<NUM> or PSR-<NUM> manufactured by Taiyo Ink, Co. , and R500 Z28 manufactured by Japan OTC.

Therefore, the second layer 324b may include the same material as the first layer 324a or may include a different material from the first layer 324a.

In addition, the second layer 324b may extend from the first layer 324a in at least one direction along the surface of the circuit board <NUM> to then be exposed. Therefore, the operator can easily determine whether the welding has been stably conducted by measuring the resistance of the exposed second layer 324b.

Claim 1:
A battery pack (<NUM>) comprising:
a protective circuit module (<NUM>) including a circuit board (<NUM>), an electrode tab coupling portion (<NUM>, <NUM>) mounted on a top surface of the circuit board (<NUM>), and a protection layer (<NUM>, <NUM>, <NUM>) positioned under the electrode tab coupling portion (<NUM>, <NUM>);
a conductive adhesive member (121a) arranged on edges of a bottom surface of the electrode tab coupling portion to fix the electrode tab coupling portion to the top surface of the circuit board (<NUM>), wherein the conductive adhesive member is not arranged in a central portion of the bottom surface of the electrode tab coupling portion, thereby defining a space between a central region of the electrode tab coupling portion (<NUM>) and the circuit board (<NUM>) in which the protection layer is arranged, and
a battery cell (<NUM>) including an electrode tab (<NUM>, <NUM>) protruding at one end, and coupled to a top surface of the electrode tab coupling portion (<NUM>, <NUM>) by welding, wherein the protection layer is configured to protect the circuit board from a laser beam during the welding process, and
wherein the electrode tab (<NUM>, <NUM>) of the battery cell, and the electrode tab coupling portion (<NUM>, <NUM>) and the protection layer (<NUM>, <NUM>, <NUM>) of the protective circuit module are stacked and coupled on top of one another.