WO2018120007A1

WO2018120007A1 - Polymeric positive temperature coefficient device for battery cell protection

Info

Publication number: WO2018120007A1
Application number: PCT/CN2016/113469
Authority: WO
Inventors: Cheng Hu; Yingsong FU; Bing Wang; Chuanrong MIAO
Original assignee: Littelfuse Electronics (Shanghai) Co., Ltd.
Priority date: 2016-12-30
Filing date: 2016-12-30
Publication date: 2018-07-05

Abstract

Provided herein are approaches for battery cell protection. In one approach, a positive temperature coefficient (PTC) device may include a protection component including a first side and a second side, and a component housing encasing the protection component. The PTC device may further include a first terminal electrically connected through a first opening of the component housing to the first side of the protection component, and a second terminal electrically connected through a second opening of the component housing to the second side of the protection component. In some approaches, the PTC device includes at least one protection strap extending between the first and second terminals to provide enhanced mechanical coupling therebetween, particularly in the event of a fault.

Description

POLYMERIC POSITIVE TEMPERATURE COEFFICIENT DEVICE FOR BATTERY CELL PROTECTION

Field of the Disclosure

The disclosure relates generally to battery cell protection, and more particularly, to a polymeric positive temperature coefficient device for battery cell protection.

Background of the Disclosure

Batteries, such as lithium batteries, are sensitive to faults caused by external short circuits, uncontrolled charging, abuse of over-charging, and the like. In order to provide an over-temperature or over-current protection for a battery cell, various protection devices have been developed. One such protection device includes a positive temperature coefficient (PTC) device, which may contain PTC elements such as a PTC conductive polymer, e.g., a composition comprising an organic polymer and, dispersed or otherwise distributed therein, a particulate conductive filler, e.g. carbon black, or a metal or a conductive metal compound. Such devices may be referred to as polymer PTC, or PPTC resistors or resistive devices.

Current battery cell protection devices are located external to the battery cell in an effort to minimize damage to the battery cell. However, external positioning of the battery cell protection device prevents direct sensing of battery parameters such as current, temperature condition, etc.

Summary

In view of the foregoing, what is needed is a battery cell protection device for fault protection, wherein the battery cell protection device is arranged within a battery cell so as encapsulate a PTC component housed therein and to resist electrolyte corrosion.

In one approach, an exemplary positive temperature coefficient (PTC) device may include a protection component, a component housing surrounding the protection component, a first terminal electrically connected to a first side of the protection component, and a second terminal electrically connected to a second side of the protection component.

In another approach, an exemplary positive temperature coefficient (PTC) device may include a PTC protection component including a first side and a second side, a component housing encasing the PTC protection component, a first terminal electrically connected to the first side of the PTC protection component, and a second terminal electrically connected to the second side of the PTC protection component.

In yet another approach, an exemplary method may include providing a protection component including a first side and a second side, connecting a first terminal to the first side of the protection component and a second terminal to the second side of the protection component through, and surrounding the protection component with a component housing.

Brief Description of the Drawings

The accompanying drawings illustrate exemplary approaches of the disclosed embodiments so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is an isometric view of a device, such as a PTC device, according to exemplary approaches of the disclosure；

FIG. 2 is side cross-section view of the device of FIG. 1 according to exemplary approaches of the disclosure；

FIG. 3 is an exploded view of the device of FIG. 1 according to exemplary approaches of the disclosure； and

FIG. 4 depicts a process flow for forming the device of FIGs. 1-3 according to an exemplary approach of the disclosure.

The drawings are not necessarily to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict typical embodiments of the disclosure, and therefore should not be considered as limiting in scope. In the drawings, like numbering represents like elements.

Furthermore, certain elements in some of the figures may be omitted, or illustrated not-to-scale, for illustrative clarity. Furthermore, for clarity, some reference numbers may be omitted in certain drawings.

Detailed Description

Embodiments in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The system/circuit may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art.

For the sake of convenience and clarity, terms such as “top, ” “bottom, ” “upper, ” “lower, ” “vertical, ” “horizontal, ” “lateral, ” and “longitudinal” will be used herein to describe the relative placement and orientation of various components and their constituent parts. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or operations, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

As stated above, described herein are approaches for battery cell protection. In one approach, a PTC device may include a protection component including a first side and a second side, and a component housing encasing the protection component. The PTC device may further include a first terminal electrically connected through a first opening of the component housing to the first side of the protection component, and a second terminal electrically connected through a second opening of the component housing to the second side of the protection component. In some approaches, the PTC device includes at least one protection strap extending between the first and second terminals to provide enhanced mechanical coupling therebetween, particularly in the event of a fault condition.

In some approaches, the protection component is a passive protection component, such as a PTC chip, a negative temperature coefficient (NTC) chip, or a fuse. In other approaches, the protection component may include active protection components such as integrated circuits or sensors. The protection component may be embedded in a component housing made of a flexible material or molding, or a coating or encapsulation, such as epoxy. The active and/or passive components may be connected with a conductive layer to form a protection circuit with a set of terminals.

In some embodiments, the device is divided into multiple layers, namely a top layer, a central layer, and a bottom layer. For example, the top layer includes a first terminal, the central layer embeds and encapsulates the protection component (s) , as well as contains one or more soldering layers, and the bottom layer includes a second terminal. The first and second terminals, or lands, may be connected to external circuits or external equipment, thus protecting the battery cell.

As a result, embodiments of the present disclosure may provide at least the following advantages. Firstly, battery cell fault protection inside the battery cell is achieved, while corrosion or damage to the battery cell fault protection element is minimized. Secondly, by virtue of the battery cell protection device being is arranged within the component housing of the device, variation of cell parameters such as current, condition and temperature of electrolyte can be directly sensed, thus making battery cell fault protection more safe and reliable. Thirdly, when a thermal cut off (TCO) or PTC chip is employed, the PTC device can be reused to achieve repeatable protection.

Turning now to FIGS. 1-3, illustrated is an exemplary PTC device (hereinafter “device” ) 100 in accordance with embodiments of the present disclosure. As shown, the device 100 may include a protection component 102 encased within a component housing 106. The protection component 102 may including a first side 108 and a second side 110 opposite the first side. The first and

second sides

108, 110 may respectively include first and second conductive layers 112A-B (e.g., solder material) formed thereon. The device 100 may further include a first terminal 116 electrically connected through a first opening 120 of the component housing 106 to the first side 108 of the protection component 102, and a second terminal 124 electrically connected through a second opening 126 of the component housing 106 to the second side 108 of the protection component 102. Once joined, the protection component 102, the conductive layer 112, and the first and

second terminals

116, 124 form a protection circuit used to detect and mitigate the occurrence of a fault condition.

In some embodiments, the protection component 102 is the primary component for achieving the battery cell fault protection. The protection component 102 may include a thermal cut off (TCO) element, a thermal fuse or a positive temperature coefficient (PTC) circuit protection component. According to some embodiments, the PTC circuit protection component may be a polymer positive temperature coefficient (PPTC) circuit protection component. When a TCO or PTC circuit protection component is employed, the device 100 can be reused and achieve repeatable protection.

The protection component 102 may have any shape suitable for connection with the first and

second terminals

116, 124 and for arrangement within the component housing 106. According to other embodiments, the protection component 102 may be designed as a tape or as a chip-type element. When designed as a tape, the protection component 102 may have a width of about 1 mm to 5 mm, and a thickness of about 0.2 mm to 2 mm. However, the protection component 102 may take on other lengths, shapes, and/or sizes in other embodiments.

In some embodiments, the protection component 102 is selected from the non-limiting group consisting of: fuses, PTCs, NTCs, ICs, sensors, MOSFETS, resistors, and capacitors. Of these protection components, ICs and sensors are considered to be active protection components, while PTCs, NTCs, and fuses are considered to be passive components. In the embodiment shown, the protection component 102 may be a PTC chip. It will be appreciated, however, that the embodiments described herein are not limited to any number or particular type of protection component.

Furthermore, the PTC material of protection component 102 may be made of a positive temperature coefficient conductive composition comprising a polymer and a conductive filler. The polymer of the PTC material may be a crystalline polymer selected from the group consisting of polyethylene, polypropylene, polyoctylene, polyvinylidene chloride and a mixture thereof. The conductive filler may be dispersed in the polymer and is selected from the group consisting of carbon black, metal powder, conductive ceramic powder and a mixture thereof. Furthermore, to improve sensitivity and physical properties of the PTC material, the PTC conductive composition may also include an additive, such as a photo initiator, cross-link agent, coupling agent, dispersing agent, stabilizer, anti-oxidant and/or nonconductive anti-arcing filler.

As further shown, the device 100 may include the component housing 106 encasing the protection component 102. In some embodiments, the component housing 106 is sandwiched between the first and

second terminals

116, 124 and extends entirely around an outer perimeter of the protection component 102. The component housing 106 may have an exterior frame 130 and an interior opening 132 for receiving the protection component 102 therein. As shown, the component housing 106 may wrap around first and second ends 134A-B of the protection component 102, while the first and

second openings

120, 126 of the component housing 106 permit access by the first and

second terminals

116 and 124, respectively. By covering a sufficient distance beyond the protection component 102 using the component housing 106, sealing of the protection component 102 is improved.

Although not limited to any particular shape or configuration, the component housing 106 may have a generally rectangular shape. In some embodiments, the component housing 106 is made from an epoxy coating material. In other embodiments, the component housing 106 is made from a moldable material. In exemplary embodiments, the component housing 106 serves as an anti-corrosion sealing element used to prevent the protection component 102 from being eroded, for example, by elements present in a lithium polymer battery electrolyte. To accomplish this, in some particular embodiments, the component housing 106 combines with the first and

second terminals

116 and 124 to fully cover the protection component 102, as well as the first conductive layer 112A connecting the first terminal 116 with the first side 108 of the protection component 102 and the second conductive layer 112B connecting the second terminal 124 with the second side 110 of the protection component 102.

According to some particular embodiments, the component housing 106 is flexible so that the component housing 106 may conform to the thermal expansion or contraction of the protection component 102, thereby ensuring a sealing effect around the protection component 102. According to other embodiments, component housing 106 includes at least one of a heat shrinkable tube, an injection molded article, and a coating film. The material for the heat shrinkable tube may be plastic, including polyvinyl chloride (PVC) , polypropylene (PP) , ethylene-vinyl acetate copolymer (EVA) , polyethylene terephthalate (PET) , and the like. The material may be extrusion-molded into a plastic tube having a predetermined size and shape, and then the polymer is interlinked by using irradiation technique. The size of the tube is enlarged through a mold, and then the tube shrinks to reach a preset size and shape by means of interlinking the polymer by irradiation under a heating condition, thereby providing an insulation sealing for the component housing 106, and in turn rendering the protected part an anti-corrosion function by isolating it from the external environment.

According to some particular embodiments, the heat shrinkable tube may be a dual wall heat shrinkable tube. The material of outer wall of the dual wall heat shrinkable tube may be semi rigid PP, which provides a sufficient strength, and the material of inner wall may be soft PP, which aids with sealing. In the present disclosure, when a dual wall heat shrinkable tube is used, an increased sealing effect on the protection component 102 can be achieved.

In some embodiments, the heat shrinkable tube may include one or more anti-corrosion sealing layers provided on a boundary of the heat shrinkable tube (i.e., the interface between components covered by the heat shrinkable tube and the part not covered by the heat shrinkable tube) . The material for this anti-corrosion sealing layer may be an anti-corrosion plastic material, including liquid crystal polymer (LCP) , polybutylene succinate (PBS) , polyethylene (PE) , polycarbonate (PC) , and the like. By sealing the possible open area of the heat shrinkable tube by the anti-corrosion sealing layer, the sealing effect of the anti-corrosion sealing element is further improved.

In yet other embodiments, the component housing 106 may be formed by an injection molding or coating process. For example, the material used in the injection molding process may be an anti-corrosion plastic material, including liquid crystal polymer (LCP) , polybutylene succinate (PBS) , polyethylene (PE) , polycarbonate (PC) , and the like. According to some particular embodiments, the material used in the coating process may be a curable anti-corrosion material, including some thermal curable resins, such as epoxy resin, polyurethane, acrylic resin, silicone resin, poly (p-xylylene) polymers, and fluororesin. The component housing 106 may be molded around or applied as a coating to the protection component 102 after the first and

second terminals

116 and 124 have been coupled to the protection component 102. By doing, a better seal may be formed around the coupling of the protection component 102 and the first and

second terminals

116 and 124. Furthermore, in some embodiments, the component housing 106 may extend around or cover a portion of the first and

second terminals

116, 124, for example, along an outer surface 154 of each of the first and

second terminals

116, 124.

According to some particular embodiments, in the case the component housing 106 is formed by a coating process, the component housing 106 may include a structure of multiple layers. For example, the component housing 106 may include a flexible adhesive coating layer, an oxygen barrier layer, and an anti-corrosion coating layer, in this order, from the inside out. The use of layered component housing 106 having multiple coating layers may improve the protection effect on the protection component 102. For example, the main component of the flexible adhesive coating layer may be a silicone resin, which not only assures the bonding force between the component housing 106 and the protection component 102, but also provides a buffering function to reduce the occurrence of inner stress. The main component of the oxygen barrier layer may be an epoxy resin, which is capable of insulating the protection component 102 from the influence of oxidation, such as by oxygen gas and the like. The main component of the outermost anti-corrosion coating layer may be a fluororesin, which provides protection against the electrolyte inside the battery cell. The multiple layered component housing 106 is not limited to a three layers structure, however, and the number of the layers (for example, two layers) and the function of each layer may be selected as desired.

In some embodiments, the thickness of the component housing 106 may be from 0.02 mm to 1 mm. According to other embodiments, the thickness of the component housing 106 may be 0.1 mm or more, or 0.2 mm or more, and 0.5 mm or less, or 0.6 mm or less. A thickness of 0.02 mm or more may ensure the sealing strength of the component housing 106, while a thickness of 1 mm or less may avoid unnecessary bulk from being present within the device 100.

Referring still to FIGs. 1-3, the device 100 includes the first and

second terminals

116 and 124, which may be conductive terminals used for connecting the protection component 102 to a set of electrodes (not shown) . For example, the first terminal 116 may connect the protection component 102 to an inner electrode of the battery cell, and the second terminal 124 may connect the protection component 102 to an external electrode, thereby forming a connection in series.

Each of the first and

second terminals

116, 124 may have a protection component-bonding portion 136, an electrode-bonding portion 137, and a linking portion 138 extending therebetween. In exemplary embodiments, the protection component-bonding portion 136 is configured to bond with the protection component 102 and the component housing 106. In some embodiments, the linking portion 138 may have a relative lower strength, which renders enhanced flexibility, so as to ensure the free expansion of the protection component 102, and to improve the reliability of the protection component 102 for battery cell inside application.

As shown, the first and

second terminals

116 and 124 are disposed on opposite sides of the protection component 102 such that the protection component-bonding portion 136 of each of the first and

second terminals

116, 124 cover the first and

second openings

120, 126 of the component housing 106. Furthermore, the first terminal 116 may include a first protrusion 140 extending through the first opening 120 of the component housing 106, the first protrusion 140 being in electrical/physical contact with the first conductive layer 112A. Similarly, the second terminal 124 may include a second protrusion 142 extending through the second opening 126 of the component housing 106, the second protrusion 142 being in electrical/physical contact with the second conductive layer 112B.

In some non-limiting embodiments, the first and

second terminals

116, 124 each have a sheet shape. For example, the first terminal 116 (i.e., the upper terminal the device 100 as oriented in FIGs. 1-3) connects to the first side 108 of the protection component 102, and its linking portion 138 is flat or substantially flat, so that the electrode-bonding portion 137 is generally on a same plane as the protection component-bonding portion 136 and the first side 108 of the protection component 102. Similarly, the second terminal 124 (i.e., the lower terminal the device 100 as oriented in FIGs. 1-3) connects to the second side 110 of the protection component 102, and its linking portion 138 is flat or substantially flat, so that the electrode-bonding portion 137 is generally on a same plane as the protection component-bonding portion 136 and the second side 110 of the protection component 102. In other embodiments, each of the first and

second terminals

116 and 124 may take on different shapes or configurations.

As shown, the first protrusion 140 and the second protrusion 142 extend from the protection component-bonding portion 136 of the first terminal 116 and the second terminal 124, respectively. For example, the first and

second protrusions

140 and 142 may include a bumped out section that extends toward the protection component 102 in a perpendicular or substantially perpendicular direction so as to make contact with the first and second conductive layers 112A-B, respectively. In some embodiments, the first and

second terminals

116 and 124 may be connected to the protection component 102 in any suitable bonding manner, for example, using a riveted connection, or by welding (such as spot welding and laser welding) . For a tape-type or sheet-type protection component 102, the protection component-bonding portion 136 of each terminal may entirely cover the first and second surfaces/

sides

108, 110 of the protection component 102, or may only cover a part of the first and

second sides

108, 110 of the protection component 102. In some embodiments, when the protection component 102 is a PTC, in particular PPTC, current protection component having a large thermal expansion coefficient, partially covering the first and

second sides

108, 110 of the protection component 102 beneficially allows the protection component 102 sufficient area for thermal expansion.

The electrode-bonding portions 137 of the first and

second terminals

116, 124 may be bonded to electrodes (not shown) in known fashion. For example, the electrode-bonding portion 137 includes openings 144 to receive a riveted joint, and may be further bonded to the electrode in a welding manner. There is no particular limitation on the material of the first and

second terminals

116 and 124, and a metal, for example, nickel, copper, tinned copper, stainless steel or copper surfaced stainless steel, may be used. In some embodiments, when the first and

second terminals

116, 124 are in a sheet form, the thickness of the sheet conductive terminal is generally from 0.05 mm to 0.5 mm. A sheet conductive terminal having a thickness of 0.05 mm or more can ensure adequate strength.

Referring still to FIGs. 1-3, the device 100 further includes at least one protective strap 150 extending between the first and

second terminals

116 and 124. As shown, the protective strap 150 is a mechanical connector extending between an inner surface 152 of each of the first and

second terminals

116, 124 to the outer surface 154 of each of the first and

second terminals

116, 124. More specifically, the protective strap 150 includes a first section 151 coupled (e.g., adhesively) to the linking portion 138 of each of the first and

second terminals

116 and 124, and a central section 153 extending to the exterior frame 130 of the component housing 106. In some embodiments, the central section 153 may include a flat or generally flat surface 156 in abutment with the component housing 106 in an area proximate the first and second ends 134A-B of the protection component 102 to provide physical/mechanical support to the component housing 106. In one embodiment, the surface 156 is adhesively attached to the component housing 106.

An overlap 158 of the protective strap 150 extends from the central section 153 for engagement with the outer surface 154 of the first and

second terminals

116, 124 so as to provide further physical/mechanical support to the component housing 106. As shown, the overlap 158 may extend partially along the protection component-bonding portion 136 of each of the first and

second terminals

116, 124. In some embodiments, the overlap 158 does not extend over the first and

second protrusions

140, 142. However, in other embodiments, the overlap 158 may extend entirely over the protection component-bonding portion 136, including the first and

second protrusions

140, 142 to provide further physical/mechanical support to the component housing 106.

As further shown, each protective strap 150 may include a fastener 160 configured to engage a locking opening 162 provided through each of the first and

second terminals

116, 124. In some embodiments, the fastener 160 may have a button or rivet shape, which enhances mechanical/physical coupling of the protective strap 150 with each of the first and

second terminals

116, 124 when the fastener 160 is inserted through the locking opening 162.

In some embodiments, the protective strap 150 may be formed by an injection molding or coating process. For example, the material used in the injection molding process may be an anti-corrosion plastic material, including liquid crystal polymer (LCP) , polybutylene succinate (PBS) , polyethylene (PE) , polycarbonate (PC) , and the like. According to some particular embodiments, the material used in the coating process may be a curable anti-corrosion material, including some thermal curable resins, such as epoxy resin, polyurethane, acrylic resin, silicone resin, poly (p-xylylene) polymers, and fluororesin. The protective strap 150 may be flexible to accommodate thermal expansion or contraction resulting from the protection component 102.

Turning now to FIG. 4, an exemplary process 170 for providing battery cell protection will be described in greater detail. First, as shown at block 172, a protection component is provided, wherein the protection component includes a first side and a second side. In some embodiments, the protection component is one of: fuses, PTCs, NTCs, ICs, sensors, MOSFETS, resistors, and capacitors.

As shown at block 174, a first terminal is connected to the first side of the protection component, and a second terminal is connected to the second side of the protection component. In some embodiments, the first and second terminals are electrically connected with the protection component 102 via a conductive layer, such as a soldering material.

As shown at block 176, the protection component is surrounded with a component housing. In some embodiments, the component housing encases the protection component. In some embodiments, the component housing may wrap around first and second ends of the protection component, while first and second openings of the component housing permit access by first and second terminals, respectively. In some embodiments, the component housing may be molded around or applied as a coating to the protection component after the first and second terminals and have been coupled to the protection component. By doing, a better seal may be formed around the coupling of the protection component and the first and second terminals. In some embodiments, the component housing covers or surrounds a portion of the first and second terminals.

As shown at block 178, the first and second terminals may further be coupled together using a protection strap. In some embodiments, the first and second terminals each include a locking opening for receiving the protection strap. In some embodiments, the protection strap extends between an inner surface of the first terminal to an outer surface of the second terminal.

While the present disclosure has been described with reference to certain approaches, numerous modifications, alterations and changes to the described approaches are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claims. Accordingly, it is intended that the present disclosure not be limited to the described approaches, but that it has the full scope defined by the language of the following claims, and equivalents thereof. While the disclosure has been described with reference to certain approaches, numerous modifications, alterations and changes to the described approaches are possible without departing from the spirit and scope of the disclosure, as defined in the appended claims. Accordingly, it is intended that the present disclosure not be limited to the described approaches, but that it has the full scope defined by the language of the following claims, and equivalents thereof.

Claims

A positive temperature coefficient (PTC) device, comprising:

a protection component；

a component housing surrounding the protection component；

a first terminal electrically connected to a first side of the protection component； and

a second terminal electrically connected to a second side of the protection component.
The PTC device of claim 1, further comprising a first conductive layer connecting the first terminal with the first side of the protection component.
The PTC device of claim 2, further comprising a second conductive layer connecting the second terminal with the second side of the protection component.
The PTC device of claim 3, wherein the first and second conductive layers include a solder material.
The PTC device of claim 3, wherein the first terminal includes a first protrusion extending through a first opening of the component housing, the first protrusion in contact with the first conductive layer, and wherein the second terminal includes a second protrusion extending through a second opening of the component housing, the second protrusion in contact with the second conductive layer.
The PTC device of claim 1, further comprising at least one protection strap extending between the first and second terminals.
The PTC device of claim 6, wherein the first and second terminals each include an inner surface and an outer surface, and wherein the at least one protection strap extends between the inner surface of the first terminal and the outer surface of the second terminal.
The PTC device of claim 6, wherein the first and second terminals each include a locking opening for receiving the at least one protection strap.
The PTC device of claim 8, wherein the at least one protection strap includes a fastener extending through the locking opening.
The PTC device of claim 1, wherein the protection component includes a PTC protection component.
A positive temperature coefficient (PTC) device, comprising:

a PTC protection component including a first side and a second side；

a component housing encasing the PTC protection component；

a first terminal electrically connected to the first side of the PTC protection component； and

a second terminal electrically connected to the second side of the PTC protection component.
The PTC device of claim 11, further comprising a first conductive layer connecting the first terminal with the first side of the PTC protection component, and a second conductive layer connecting the second terminal with the second side of the protection component.
The PTC device of claim 12, wherein the first terminal includes a first protrusion extending through a first opening of the component housing, the first protrusion in contact with the first conductive layer, and wherein the second terminal includes a second protrusion extending through a second opening of the component housing, the second protrusion in contact with the second conductive layer.
The PTC device of claim 11, further comprising at least one protection strap extending between the first and second terminals.
The PTC device of claim 14, wherein the first and second terminals each include an inner surface and an outer surface, and wherein the at least one protection strap extends between the inner surface of the first terminal and the outer surface of the second terminal.
The PTC device of claim 14, wherein the first and second terminals each include a locking opening for receiving the at least one protection strap.
A method, comprising:

providing a protection component including a first side and a second side；

connecting a first terminal to the first side of the protection component and a second terminal to the second side of the protection component through； and

surrounding the protection component with a component housing.
The method of claim 17, further comprising coupling the first and second terminals using a protection strap, wherein the first and second terminals each include a locking opening for receiving the protection strap.
The method of claim 18, further comprising extending the protection strap between an inner surface of the first terminal to an outer surface of the second terminal.