U.S. patent application number 16/290243 was filed with the patent office on 2020-04-02 for ptc device.
The applicant listed for this patent is Polytronics Technology Corp.. Invention is credited to Wen Feng LEE, Chun Teng TSENG, David Shau Chew WANG.
Application Number | 20200105443 16/290243 |
Document ID | / |
Family ID | 69945044 |
Filed Date | 2020-04-02 |
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United States Patent
Application |
20200105443 |
Kind Code |
A1 |
TSENG; Chun Teng ; et
al. |
April 2, 2020 |
PTC DEVICE
Abstract
A PTC device comprises a current and temperature sensing
element, a first insulating layer, a second insulating layer, a
first electrode layer and a second electrode layer. The current and
temperature sensing device is a laminated structure comprising a
first conductive layer, a second conductive layer and a PTC
material layer. The first and second conductive layers are disposed
on first and second surfaces of the PTC material layer,
respectively. The second surface is opposite to the first surface.
The first and second insulating layers are disposed on the first
and second conductive layers, respectively. The first electrode
layer is disposed on the first insulating layer and electrically
connects to the first conductive layer. The second electrode layer
is disposed on the second insulating layer and electrically
connects to the second conductive layer. Corners of the current and
temperature sensing device are provided with insulating
members.
Inventors: |
TSENG; Chun Teng; (SANWAN
TOWNSHIP, TW) ; WANG; David Shau Chew; (TAIPEI CITY,
TW) ; LEE; Wen Feng; (Taoyuan City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Polytronics Technology Corp. |
Hsinchu |
|
TW |
|
|
Family ID: |
69945044 |
Appl. No.: |
16/290243 |
Filed: |
March 1, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01C 7/18 20130101; H01C
7/021 20130101; G01R 19/0092 20130101; H01C 7/13 20130101; H01C
1/1406 20130101; G01K 7/22 20130101; H01C 17/00 20130101; H01C
1/142 20130101 |
International
Class: |
H01C 7/02 20060101
H01C007/02; H01C 1/14 20060101 H01C001/14; H01C 17/00 20060101
H01C017/00; G01K 7/22 20060101 G01K007/22; G01R 19/00 20060101
G01R019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2018 |
TW |
107134108 |
Claims
1. A PTC device, comprising: a current and temperature sensing
element being a laminated structure of a first electrically
conductive layer, a second electrically conductive layer and a PTC
material layer, the first electrically conductive layer being
disposed on a first surface of the PTC material layer, the second
electrically conductive layer being disposed on a second surface of
the PTC material layer, the second surface being opposite to the
first surface; a first insulating layer disposed on the first
electrically conductive layer; a second insulating layer disposed
on the second electrically conductive layer; a first electrode
layer disposed on the first insulating layer and electrically
connecting to the first electrically conductive layer; a second
electrode layer disposed on the second insulating layer and
electrically connecting to the second electrically conductive
layer; wherein corners of the current and temperature sensing
element are provided with insulating members, wherein the first
insulating layer, the first electrically conductive layer, the PTC
material layer, the second electrically conductive layer and the
second insulating layer form a bottom surface facing a circuit
board, the first electrode layer retracts at edges relative to the
first insulating layer to form notches, and the second electrode
layer retracts at edges relative to the second insulating layer to
form notches, wherein the first electrode layer comprises a bulge
extending to an edge of the first insulating layer, and the second
electrode layer comprises another bulge extending to an edge of the
second insulating layer.
2. The PTC device of claim 1, wherein the insulating member extends
over the first electrically conductive layer, the PTC material
layer and the second electrically conductive layer.
3. The PTC device of claim 1, wherein the first and second
electrode layers serve as solder attach surfaces for soldering the
PTC device onto the circuit board.
4. The PTC device of claim 1, wherein the insulating member
comprises prepreg or resin.
5. The PTC device of claim 1, wherein the insulating member has a
hardness larger than that of the PTC material layer.
6. The PTC device of claim 1, wherein the insulating member has a
glass transition temperature higher than that of the PTC material
layer by at least 50.degree. C.
7. The PTC device of claim 1, wherein the first electrode layer,
the first insulating layer, the first electrically conductive
layer, the PTC material layer, the second electrically conductive
layer, the second insulating layer and the second electrode layer
are laminated in order.
8. The PTC device of claim 1, wherein the first electrode layer,
the first insulating layer, the first electrically conductive
layer, the PTC material layer, the second electrically conductive
layer, the second insulating layer and the second electrode layer
form a bottom surface facing the circuit board as an interface for
soldering onto the circuit board.
9. The PTC device of claim 1, further comprising: a first
electrically conductive hole penetrating through the first
insulating layer and connecting to the first electrode layer and
the first electrically conductive layer; and a second electrically
conductive hole penetrating through the second insulating layer and
connecting to the second electrode layer and the second
electrically conductive layer.
10. The PTC device of claim 9, wherein the first electrically
conductive hole is located at a center or a lateral surface of the
first insulating layer, and the second electrically conductive hole
is located at a center or a lateral surface of the second
insulating layer.
11. (canceled)
12. (canceled)
Description
BACKGROUND OF THE INVENTION
(1) Field of the Invention
[0001] The present application relates to a thermistor. More
specifically, it relates to a positive coefficient temperature
(PTC) device.
(2) Description of the Related Art
[0002] A PTC device can be used for circuit protection to avoid
over-temperature or over-current which would cause damages. A PTC
device usually comprise two electrodes and a resistive material
disposed therebetween. The resistive material has PTC feature,
i.e., it has an low resistance at a normal temperature; however,
when an over-current or an over-temperature occurs in the circuit,
the resistance instantaneously increases to extremely high
resistance (i.e., trip) to diminish the current for circuit
protection. The PTC device can be applied to temperature sensing
circuit to sense ambient temperature, so as to determine on whether
to take actions for over-temperature protection such as shutdown or
power off. When the temperature decreases to room temperature or
over-current no longer exists, the over-current protection device
returns to low resistance state so that the circuit operates
normally again. Because the PTC devices can be reused, they can
replace fuses or other temperature sensing devices to be widely
applied to high-density circuitries.
[0003] With lightweight and compact trends, electronic apparatuses
are getting smaller. For a cell phone, a number of components have
to be integrated into a limited space, in which an over-current
protection device is usually secured to a protective circuit module
(PCM) and its external lead will occupy a certain space. Therefore,
it is desirable to have a thin-type protection device that does not
take up much room. When the device is downsizing to form factor
0201, it is a great challenge on how to decrease the thickness of
the protection device for surface-mount applications.
[0004] According to specification of 0201, a device has a length of
0.6.+-.0.03 mm, a width of 0.3.+-.0.03 mm and a thickness of
0.25.+-.0.03 mm. In manufacturing, the length and width are doable,
but the thickness is too thin to be achieved. Nowadays, the
resistive material substrate of carbon black system can be at most
pressed to 0.2 mm in thickness, and the resistive material
substrate of ceramic filler system can obtain a thickness of
0.2-0.23 mm. If the resistive substrate is further engaged with
insulating (prepreg) layers and internal and external circuits
(electrodes) to form an over-current protection device as shown in
U.S. Pat. No. 6,377,467, not only is the thickness out of
specification but also the thickness may be equal to or larger than
width. As a result, the devices may topple when they are subjected
to packaging or other processes afterwards. Moreover, the
internal-and-external circuit design on a small size device
sometimes has misalignment between the internal circuit and
external circuit, and therefore the production yield will be
negatively impacted.
[0005] U.S. Pat. No. 9,007,166 proposes a solution to the aforesaid
problem. Without prepreg layers and external electrode layers, a
PTC composite substrate is devised to etch or cut an electrode
layer of the PTC composite substrate to form a groove isolating
right and left electrodes, so as to control the thickness of the
PTC over-current protection device to be smaller than or equal to
0.28 mm. However, the electrode layers of the PTC device are not
symmetrical, and therefore there is a need to verify the
orientation of the PTC device under electric testing and packaging.
Moreover, the groove may be misaligned due to inflation and
retraction of the PTC material during manufacturing, and the right
and left electrodes of unequal areas influence electric
characteristics. Without support of prepreg layers, the PTC device
may flaw due to insufficient strength during manufacturing.
Moreover, the PTC material may be molten caused by high temperature
during cutting. During a first cut, e.g., along X-axis, the molten
material is moved away by a cutter, burr or flash is not a serious
problem. However, during a sequential second cut, e.g., along
Y-axis, molten material residue may exist in the groove of the
first cut to incur burr or flash. The burr problem is less serious
for devices of large sizes and becomes more serious for devices of
small sizes. The burr incurs rough surfaces and uncontrollable
dimensions of the device and therefore impacts sequential processes
including tape and reel, surface mounting and soldering.
[0006] In view of the above, for downsizing PTC devices, it is a
great challenge to diminish burr or flash after cutting to avoid
the sequential tape and reel, SMT mounting and soldering
processes.
SUMMARY OF THE INVENTION
[0007] The present application provides a PTC device characterized
in over-current protection and/or over-temperature sensing. The PTC
device in which a current and temperature sensing element is
provided with insulating members at corners connecting to adjacent
lateral surfaces is devised to increase structural strength, avoid
burr or flash, and improve manufacturing yield.
[0008] In accordance with an embodiment of the present application,
a PTC device comprises a current and temperature sensing element, a
first insulating layer, a second insulating layer, a first
electrode layer and a second electrode layer. The current and
temperature sensing element is a laminated structure of a first
electrically conductive layer, a second electrically conductive
layer and a PTC material layer. The first electrically conductive
layer is disposed on a first surface of the PTC material layer, and
the second electrically conductive layer is disposed on a second
surface of the PTC material layer. The second surface is opposite
to the first surface. The first insulating layer is disposed on the
first electrically conductive layer, and the second insulating
layer is disposed on the second electrically conductive layer. The
first electrode layer is disposed on the first insulating layer and
electrically connects to the first electrically conductive layer.
The second electrode layer is disposed on the second insulating
layer and electrically connects to the second electrically
conductive layer. Corners of the current and temperature sensing
element are provided with insulating members.
[0009] In an embodiment, the insulating member extends over a
laminate of the first electrically conductive layer, the PTC
material layer and the second electrically conductive layer.
[0010] In an embodiment, the first and second electrode layers
serve as solder attach surfaces for soldering the PTC device onto a
circuit board.
[0011] In an embodiment, the insulating member comprises prepreg or
resin.
[0012] In an embodiment, the insulating member has a hardness
larger than that of the PTC material layer.
[0013] In an embodiment, the insulating layer has a glass
transition temperature (Tg) higher than that of the PTC material
layer by at least 50.degree. C.
[0014] In an embodiment, the first electrode layer, the first
insulating layer, the first electrically conductive layer, the PTC
material layer, the second electrically conductive layer, the
second insulating layer and the second electrode layer are
laminated in order.
[0015] In an embodiment, the first electrode layer, the first
insulating layer, the first electrically conductive layer, the PTC
material layer, the second electrically conductive layer, the
second insulating layer and the second electrode layer form a
bottom surface facing the circuit board as an interface for
soldering onto the circuit board.
[0016] In an embodiment, the PTC device further comprises a first
electrically conductive hole and a second electrically conductive
hole. The first electrically conductive hole penetrates through the
first insulating layer and connects to the first electrode layer
and the first electrically conductive layer. The second
electrically conductive hole penetrates through the second
insulating layer and connects to the second electrode layer and the
second electrically conductive layer.
[0017] In an embodiment, the first electrically conductive hole is
located at a center or a lateral surface of the first insulating
layer, and the second electrically conductive hole is located at a
center or a lateral surface of the second insulating layer.
[0018] In an embodiment, the first insulating layer, the first
electrically conductive layer, the PTC material layer, the second
electrically conductive layer and the second insulating layer form
a bottom surface facing the circuit board. The first electrode
layer retracts at edges relative to the first insulating layer to
form notches, and the second electrode layer retracts at edges
relative to the second insulating layer to form notches.
[0019] In an embodiment, the first electrode layer comprises a
bulge extending to an edge of the first insulating layer, and the
second electrode layer comprises another bulge extending to an edge
of the second insulating layer.
[0020] In a printed circuit board (PCB) process, the substrate for
making the current and temperature sensing element is drilled to
form holes. The holes are filled with resin or prepreg in a
sequential press process to form insulating members. The insulating
members are formed at the corners of the current and temperature
sensing element to avoid or diminish burrs after cutting, and
thereby improving tape, reel and soldering processes.
[0021] In the present application, the PTC device in which the
first electrode layer and the second electrode layer at two ends of
the laminate serve as solder attach surfaces for soldering onto a
circuit board is suitable to be made in small sizes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The present application will be described according to the
appended drawings in which:
[0023] FIGS. 1 through 5 show a manufacturing process of a PTC
device in accordance with an embodiment of the present
application;
[0024] FIG. 6 shows a PTC device in accordance with an embodiment
of the present application;
[0025] FIG. 7 shows a cross-sectional view of a PTC device applied
to a circuit board in accordance with an embodiment of the present
application;
[0026] FIG. 8 shows a PTC device in accordance with another
embodiment of the present application;
[0027] FIG. 9 shows a way of making a PTC device in accordance with
an embodiment of the present application;
[0028] FIG. 10 shows a PTC device in accordance with yet another
embodiment of the present application;
[0029] FIG. 11 shows a way of making a PTC device in accordance
with another embodiment of the present application; and
[0030] FIG. 12 shows a PTC device in accordance with an embodiment
of the present application.
DETAILED DESCRIPTION OF THE INVENTION
[0031] The making and using of the presently preferred illustrative
embodiments are discussed in detail below. It should be
appreciated, however, that the present application provides many
applicable inventive concepts that can be embodied in a wide
variety of specific contexts. The specific illustrative embodiments
discussed are merely illustrative of specific ways to make and use
the invention, and do not limit the scope of the invention.
[0032] Referring to FIG. 1, a composite substrate including a first
electrically conductive layer 13, a PTC material layer 12 and a
second conductive layer 14 is provided and the composite substrate
is drilled to form holes 31 with certain intervals therebetween.
Referring to FIG. 2, a first electrode layer 17, a first insulating
layer 15, the first electrically conductive layer 13, the PTC
material layer 12, the second electrically conductive layer 14, a
second insulating layer 16 and a second electrode layer 18 are
pressed to form a laminated structure. The first electrically
conductive layer 13 is disposed on a first surface of a PTC
material layer 12, and the second electrically conductive layer 14
is disposed on a second surface of the PTC material layer 12. The
second surface is opposite to the first surface. The first
insulating layer 15 is disposed on the first electrically
conductive layer 13, and the second insulating layer 16 is disposed
on the second electrically conductive layer 14. The first electrode
layer 17 is disposed on the first insulating layer 15, and the
second electrode layer 18 is disposed on the second insulating
layer 16. The first and second electrically conductive layers 13
and 14 may be copper layers. The first and second insulating layers
15 and 16 may comprise prepreg. The first and second electrode
layers 17 and 18 may comprise copper. Prepreg is flowable and
therefore can be filled in the holes 31 during pressing to form
insulating members 30. Alternatively, the holes 31 can be filled
with material such as resin before pressing to form the insulating
members 30. The material of the insulating members 30 is not
limited to prepreg or resin, other polymers with required features
such as insulation and hardness can be used instead.
[0033] The PTC material layer 12 comprises crystalline polymer and
conductive filler dispersed therein. The crystalline polymer
comprises polyethylene, polypropylene, polyvinyl fluoride, mixture
or copolymer thereof. The conductive filler may comprise
carbon-containing filler, metal filler, and/or ceramic filler. For
example, the metal filler may be nickel, cobalt, copper, iron, tin,
lead, silver, gold, platinum, or the alloy thereof. The ceramic
filler may be titanium carbide (TiC), tungsten carbide (WC),
vanadium carbide (VC), zirconium carbide (ZrC), niobium carbide
(NbC), tantalum carbide (TaC), molybdenum carbide (MoC), hafnium
carbide (HfC), titanium boride (TiB.sub.2), vanadium boride
(VB.sub.2), zirconium boride (ZrB.sub.2), niobium boride
(NbB.sub.2), molybdenum boride (MoB.sub.2), hafnium boride
(HfB.sub.2), or zirconium nitride (ZrN). Moreover, the conductive
filler may be the mixture, alloy, solid solution or core-shell of
the aforesaid metal and ceramic fillers.
[0034] Referring to FIGS. 3 and 4, FIG. 3 is a side view of the
laminated structure and FIG. 4 is a top view thereof. Holes 20 with
certain intervals are made in the laminated substrate. As shown in
FIG. 4, the hole 20 is located among adjacent four insulating
members 30. Vertical and horizontal dashed lines are predetermined
cutting lines and the insulating members 30 are located at
intersections of the vertical and horizontal cutting lines. Upper
holes 20 go through the first electrode layer 17 and the first
insulating layer 15 and stop at the first electrically conductive
layer 13. Lower holes 20 go through the second electrode layer 18
and the second insulating layer 16 and stop at the second
electrically conductive layer 14. The holes 20 may be directly made
by laser drilling which is suitable for small size holes and can
control the drilling depth precisely. Alternatively, the first
electrode layer 17 and the second electrode layer 18 can be etched
first and followed by laser drilling the first insulating layer 15
and the second insulating layer 16. The holes 20 may be made by
mechanical drilling. However, the first electrically conductive
layer 13 and the second electrically conductive layer 14 may be
partially and fully removed by mechanical drilling.
[0035] Referring to FIG. 5, the upper and lower holes 20 are filled
with electrically conductive material to form first electrically
conductive members 21 and second electrically conductive members
22. In an embodiment, the first and second electrically conductive
members 21 and 22 may be made by electroplating copper. During
electroplating, copper may be electroplated onto the first
electrode layer 17 and the second electrode layer 18 also to
increase their thicknesses. In case of large holes 20, the material
of the first and second electrically conductive members 21 and 22
may be not able to fully fill the holes 20. As a result, recesses
may be generated on the surfaces of the conductive members 21 and
22. The first and second electrode layers 17 and 18 may be plated
with tin to enhance solderability. Afterwards, the laminated
structure is divided along the cutting lines to form a plurality of
PTC devices 10. A single PTC device 10 is shown in FIG. 6. In an
embodiment, the PTC device 10 has equal width and thickness, that
is, as shown in FIG. 6, the first electrode layers 17 and 18 are
square. As such, the PTC device 10 is not affected even if it rolls
over. It should be noted that the first and second electrode layers
17 and 18 are not limited to square and may be rectangular. The
insulating members 30 are formed at corners of the middle of the
PTC device 10. The material of the insulating members 30 such as
prepreg or resin is tougher than the PTC material layer 12 and,
unlike the first electrically conductive layer and the second
electrically conductive layer, it has no metal ductility.
Therefore, the insulating members 30 can protect the PTC material
and avoid occurrence of burr or flash. To prevent the PTC material
layer 12 from generating burr or flash, a hardness of the
insulating member 30 is larger than that of the PTC material layer
12 or a glass transition temperature (Tg) of the insulating member
30 is higher than that of the PTC material layer 12 by at least
50.degree. C.
[0036] FIG. 7 shows the PTC device 10 soldered onto a circuit board
60 in accordance with an embodiment of the present application. The
PTC device 10 is soldered onto the circuit board 60 through solder
paste 61. The PTC device 10 comprises a current and temperature
sensing element 11, the first insulating layer 15, the second
insulating layer 16, the first electrode layer 17, the second
electrode layer 18, the first electrically conductive member 21 and
the second electrically conductive member 22. The current and
temperature sensing element 11 is a laminate comprising a first
electrically conductive layer 13, a second electrically conductive
layer 14 and a PTC material layer 12 laminated therebetween. The
insulating members 30 extend over the laminate of the first
electrically conductive layer 13, the second electrically
conductive layer 14 and the PTC material layer 12. More
specifically, four insulating members 30 are formed at corners of
the current and temperature sensing element 11. Each corner
connects adjacent lateral surfaces of the current and temperature
sensing element 11. The first electrode layer 17 is disposed on the
first insulating layer 15, and electrically connects to the first
electrically conductive layer 13. The second electrode layer 18 is
disposed on the second insulating layer 16, and electrically
connects to the second electrically conductive layer 14. The first
electrically conductive member 21 penetrates through the first
insulating layer 15 and connects to the first electrode layer 17
and the first electrically conductive layer 13. The second
electrically conductive member 22 penetrates through the second
insulating layer 16 and connects to the second electrode layer 18
and the second electrically conductive layer 14. In this
embodiment, the first electrode layer 17, the first insulating
layer 15, the first electrically conductive layer 13, the PTC
material layer 12, the second electrically conductive layer 14, the
second insulating layer 16 and the second electrode layer 18 are
stacked in order and form a bottom surface 24. The bottom surface
24 faces the circuit board 60 as an interface for soldering onto
the circuit board 60. During soldering, solder paste 61 climbs up
along the first electrode layer 17 and the second electrode layer
18. In other words, the first electrode layer 17 and the second
electrode layer 18 serve as solder attach surfaces when soldering
the PTC device 10 onto the circuit board 60.
[0037] When cutting to form the PTC devices 10, as shown in FIG. 5,
the bottom second electrode layer 18 may be stretched by the cutter
to cause burrs because of metal ductility. FIG. 8 shows a PTC
device 70 in accordance with another embodiment of the present
application. In comparison with the PTC device 10 shown in FIG. 6,
The first electrode layer 17 retracts at edges relative to the
first insulating layer 15 to form notches 26, and the second
electrode layer 18 retracts at edges relative to the second
insulating layer 16 to form notches 26 as well. In this embodiment,
the PTC device 70 is symmetrical. FIG. 9 shows a way of making the
first and second electrode layers 17 and 18 of the PTC device 70.
Before cutting, grooves 81 are made in the first and second
electrode layers 17 and 18. The grooves 81 surround the holes 20
and locate at cutting positions. The intersections of vertical and
horizontal grooves 81 correspond to the positions of the insulating
members 30. The width of the groove 81 is larger than cutting width
and is approximately the width of a cutter plus twice the width of
the notch 26. As a result, the cutter does not touch the first and
second electrode layers 17 and 18 when cutting to form the notches
26, so as to avoid burrs on the electrode layer 17 or 18.
[0038] FIG. 10 shows a PTC device 90 in accordance with yet another
embodiment of the present application. The first and second
electrode layers 17 and 18 of both the PTC device 90 and the PTC
device 70 retract their edges. Different from the PTC device 70,
the edges of the first electrode layer 17 of the PTC device 90
comprise bulges 27 extending to the edges of the first insulating
layer 15, and the edges of the second electrode layer 18 of the PTC
device 90 comprise bulges 28 extending to the edges of the second
insulating layer 16. One of the bulges 27 and one of the bulges 28
reach the bottom of the PTC device 90 to provide paths for solder
attachment or solder climbing. As such, it is advantageous to
enhance solder attachment especially for large notches 26. FIG. 11
shows a way of making the first and second electrode layers 17 and
18 of the PTC device 90. Grooves 91 are made in the first and
second electrode layers 17 and 18. The grooves 91 correspond to
cutting positions but are not continuous. The first and second
electrode layers 17 and 18 of neighboring devices 90 are partially
connected. The connection of the first and second electrode layers
17 and 18 form the bulges 27 and 28. In an embodiment, the width of
the bulge 27 or 28 is 20-60% of the width of the first or second
insulating layer 15 or 16. The width of the groove 91 is larger
than cutting width, and is approximately equal to the width of a
cutter plus twice the width of the notch 26. Because the bulges 27
and 28 are relatively small in comparison with the first and second
electrode layers 17 and 18, the burr issue can be diminished when
cutting the bulges 27 and 28 and solder attachment becomes more
effective.
[0039] The electrically conductive member 21 or 22 may be located
at but not limited to the center of the insulating layer 15 or 16.
Alternatively, the electrically conductive members 21 and 22 may be
located at center portions of lateral surfaces of the device as
long as they can electrically connect the first electrically
conductive layer 13 and the first electrode layer 17 and
electrically connect the second electrically conductive layer 14
and the second electrode layer 18. In the above embodiments, the
insulating layers 30 of prepreg or resin increase structural
strength to be suitable for device miniaturization.
[0040] FIG. 12 shows a PTC device of the present application, which
is similar to the device disclosed in U.S. Pat. No. 6,377,467
except insulating members are formed at corners of the device to
reduce burrs. A PTC device 40 comprises a current and temperature
sensing element 41, a first insulating layer 45, a second
insulating layer 46, a first electrode layer 47 and a second
electrode layer 48. The current and temperature sensing element 41
is a laminated structure comprising a first electrically conductive
layer 43, a second electrically conductive layer 44 and a PTC
material layer 42. The first electrically conductive layer 43 is
disposed on a first surface of the PTC material layer 42. The
second electrically conductive layer 44 is disposed on a second
surface of the PTC material layer 42. The second surface is
opposite to the first surface. The first insulating layer 45 is
disposed on the first electrically conductive layer 43, and the
second insulating layer 46 is disposed on the second electrically
conductive layer 44. The first electrode layer 47 has two sections
disposed on the first insulating layer 45 and the second insulating
layer 46, respectively, and electrically connects to the first
electrically conductive layer 43 through a conductive hole 49. The
second electrode layer 48 has two sections disposed on the first
insulating layer 45 and the second insulating layer 46,
respectively, and electrically connects to the second electrically
conductive layer 44 through a conductive hole 50. Insulating
members 51 are formed at four corners of the current and
temperature sensing element 41 of the PTC device 40. The material
of the insulating members 51 such as prepreg or resin is tougher
than the PTC material layer 42 and do not have metal ductility
which is inherent in the first electrically conductive layer 43 and
the second electrically conductive layer 44. The insulating members
51 can protect the PTC material and avoid occurrence of burr or
flash.
[0041] In addition to over-current protection applications, the PTC
device of the present application can conduct temperature sensing.
Insulating members formed at corners of the current and temperature
sensing element can effectively resolve burr problems and improve
sequential tape, reel and soldering processes. The PTC device is
made of a laminated structure through pressing and cutting, a
surface composed of laminated layers serves as a bottom surface for
soldering. Not only are the simple structure and manufacturing
process, but also it is suitable to be made for small devices such
as form factors 0402 and 0201. In an embodiment, the PTC device has
the same width and thickness to exclude the influence caused by
rollover.
[0042] The above-described embodiments of the present invention are
intended to be illustrative only. Numerous alternative embodiments
may be devised by persons skilled in the art without departing from
the scope of the following claims.
* * * * *