U.S. patent application number 10/072505 was filed with the patent office on 2002-11-21 for printed circuit board comprising an embedded functional element therein.
Invention is credited to Chu, Edward Fu-Hua, Ma, Yun-Ching, Wang, David Shau-Chew.
Application Number | 20020170747 10/072505 |
Document ID | / |
Family ID | 21682464 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020170747 |
Kind Code |
A1 |
Chu, Edward Fu-Hua ; et
al. |
November 21, 2002 |
Printed circuit board comprising an embedded functional element
therein
Abstract
The present invention discloses a PCB comprising a substrate, at
least one circuit layer and at least one insulating layer,
characterized in that the PCB further comprises at least one
embedded functional material such as a PTC, and NTC and ZTC
material. If the PTC material is applied in the present invention,
a normal resistance of the present invention will be substantially
smaller than that of the conventional PTC protection apparatus
since the area of the PTC material of the present invention is
larger than that of the conventional PTC protection apparatus.
Moreover, through an electrically conductive hole, an upper
electrode and a lower electrode respectively lying on top and
bottom surfaces of the functional material are respectively
connected with an apparatus mounted on a surface of the PCB to form
a conductive circuit. Thus, at least one over-current protection
apparatus which is usually mounted on the surface of the PCB is
eliminated, and the surface utilization rate of the PCB is
improved.
Inventors: |
Chu, Edward Fu-Hua; (Taipei,
TW) ; Ma, Yun-Ching; (Taipei Hsien, TW) ;
Wang, David Shau-Chew; (Taipei, TW) |
Correspondence
Address: |
Harold V. Stotland
Seyfarth Shaw
42nd Floor
55 East Monroe Street
Chicago
IL
60603-5803
US
|
Family ID: |
21682464 |
Appl. No.: |
10/072505 |
Filed: |
February 5, 2002 |
Current U.S.
Class: |
174/256 ;
174/260; 174/262; 428/209; 428/901 |
Current CPC
Class: |
H05K 2201/10022
20130101; H05K 1/0201 20130101; H05K 1/167 20130101; H05K
2201/10151 20130101; H05K 3/4644 20130101; H05K 1/095 20130101;
Y10T 428/24917 20150115; H05K 2201/09309 20130101; H05K 3/429
20130101 |
Class at
Publication: |
174/256 ;
174/260; 174/262; 428/209; 428/901 |
International
Class: |
H05K 001/03 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 20, 2001 |
TW |
090204687 |
Claims
What is claimed is:
1. A printed circuit board (PCB), comprising a substrate, at least
one circuit layer and at least one insulating layer, characterized
in that the PCB further comprises at least one embedded PTC
material layer and an upper electrode and a lower electrode
respectively lying on top and bottom surfaces of the at least PTC
material layer, and the upper electrode and the lower electrode are
electrically connected to an apparatus mounted on a surface of the
PCB through an electrically conductive hole to form a conductive
circuit.
2. The printed circuit board of claim 1, which is formed by a
build-up process.
3. The printed circuit board of claim 1, wherein the electrical
conductive hole used for connecting the upper electrode or the
lower electrode to the apparatus mounted on the surface of the PCB
is formed by mechanical drilling and then electroplating the hole,
electroless plating the hole or filling the hole with a conductive
paste.
4. The printed circuit board of claim 1, wherein the PTC material
layer is divided into several sections according to the
requirements of a resistance value and a location.
5. The printed circuit board of claim 1, wherein the PTC material
comprises a polymer and a conductive filler.
6. The printed circuit board of claim 5, wherein the polymer is
selected from the group consisting of polyethylene, polypropylene,
polyoctylene, polyvinylidene chloride and a mixture thereof.
7. The printed circuit board of claim 5, wherein the conductive
filler is selected from the group consisting of a carbon black,
metal powder, conductive ceramic powder and a mixture thereof.
8. The printed circuit board of claim 1, wherein the material of
the upper and the lower electrodes are selected from the group
consisting of copper, nickel, aurum and an alloy thereof.
9. The printed circuit board of claim 1, wherein the upper
electrode and the lower electrode are formed by a electroplating or
electroless plating process.
10. The printed circuit board of claim 1, wherein the upper
electrode and the lower electrode are formed by attaching a rough
surface of a metal foil to the PTC material layer and then being
processed by hot pressing.
11. The printed circuit board of claim 1, wherein two embedded
adjacent or non-adjacent PTC material layers can be connected in
parallel for decreasing a normal resistance value.
12. A printed circuit board (PCB) comprising a substrate, at least
one circuit layer and at least one insulating layer, characterized
in that the PCB further comprises at least one embedded NTC
material layer, an upper electrode and a lower electrode
respectively lying on top and bottom surfaces of the NTC material
layer and the upper electrode and the lower electrode are
electrically connected to an apparatus mounted on a surface of the
PCB through an electrically conductive hole for forming a
conductive circuit.
13. The printed circuit board of claim 12, wherein the electrically
conductive hole used for connecting the upper electrode or the
lower electrode with the apparatus mounted on the surface of PCB is
formed by mechanical drilling and then electroplating the hole,
electroless plating the hole or filling the hole with a conductive
paste.
14. The printed circuit board of claim 12, wherein the NTC material
layer is divided into several sections according to the
requirements of a resistance value and a location.
15. The printed circuit board of claim 12, wherein the NTC material
comprises a polymer and a conductive filler.
16. The printed circuit board of claim 15, wherein the polymer is a
crystalline polymer or a noncrystallinee polymer.
17. The printed circuit board of claim 15, wherein the conductive
filler is selected from the group consisting of a carbon black,
metal powder, conductive ceramic powder and a mixture thereof.
18. The printed circuit board of claim 12, wherein two embedded
adjacent or non-adjacent NTC material layers can be connected in
parallel for decreasing a normal resistance value.
19. A printed circuit board (PCB) comprising a substrate, at least
one circuit layer and at least one insulating layer, characterized
in that the PCB further comprises at least one embedded ZTC
material layer, an upper electrode and a lower electrode
respectively lying on top and the bottom surfaces of the ZTC
material layer, and the upper electrode and the lower electrode are
electrically connected to an apparatus mounted on the surface of
the PCB through an electrically conductive hole for forming a
conductive circuit.
20. The printed circuit board of claim 19, wherein the electrical
conductive hole used for connecting the upper electrode or the
lower electrode with the apparatus mounted on the surface of PCB is
formed by mechanical drilling and then electroplating the hole,
electroless plating the hole or filling the hole with a conductive
paste.
21. The printed circuit board of claim 19, wherein the ZTC material
layer is divided into several sections according to the
requirements of a resistance value and a location.
22. The printed circuit board of claim 19, wherein the ZTC material
comprises a polymer and a conductive filler.
23. The printed circuit board of claim 22, wherein the polymer is a
crystalline polymer or a noncrystalline polymer.
24. The printed circuit board of claim 22, wherein the conductive
filler is selected from the group consisting of a carbon black,
metal powder, conductive ceramic powder and a mixture thereof.
25. The printed circuit board of claim 19, wherein two embedded
adjacent or non-adjacent ZTC material layers can be connected in
parallel for decreasing a normal resistance value.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a printed circuit board
(PCB), and more particularly, to a printed circuit board comprising
an embedded internal functional element.
[0003] 2. Description of the Prior Art
[0004] Since the portable electronic products (such as cellular
phone, notebook computer, hand-held camera and personal digital
assistant, etc.) are getting more and more popular nowadays,
over-current protection apparatuses for avoiding the occurrence of
over-current or the over-temperature of the portable electric
products are increasingly important.
[0005] In the protection apparatuses, a positive temperature
coefficient (PTC) over-current protection apparatus is used
extensively because of its characteristics of being resettable,
sensitive to temperature and stable in reliability. Thus, the PTC
over-current protection apparatus has been widely applied to
protect batteries, especially second batteries, such as the
nickel-hydrogen battery or the lithium battery, etc.
[0006] A PTC conductive composition material (PTC material) is
utilized as a current sensitive element of the PTC over-current
protection apparatus, because the resistance of the PTC material is
very sensitive to temperature variation. Because the resistance of
the PTC material is very low at its normal temperature, the circuit
can operate normally. However, if the over-current or
over-temperature of the battery occurs because of improper usage,
the resistance of the PTC material will increase immediately for at
least ten thousand times (such as 10.sup.4 ohm) so that the PTC
material will be at a high-resistance state. Therefore, the over
current will be counterchecked and thereby the object of protecting
circuit elements of the battery is achieved.
[0007] FIG. 1 is a schematic diagram showing connection of a
conventional PTC over-current protection apparatus. One terminal of
the PTC over-current protection apparatus 12, mounted on the
surface of a printed circuit board 10, is connected to a power
supply 11 and the other terminal is connected to a first integrated
circuit 13. Generally, the normal value of the electrical
resistance of the PTC over-current protection apparatus 12 is
obtained according to the conventional formula: 1 R = .times. l A
,
[0008] in which R is the resistance in ohms, .rho. is the
resistivity in ohms-cm of the PTC material, I is the length between
two electrodes and A is the effective area of the protection
apparatus 12. Since the size of the printed circuit board of the
portable electronic product becomes smaller and smaller, the
footprint of the PTC over-current protection apparatus 12 mounted
on the printed circuit board also needs to be decreased
comparatively. According to the above formula, as the normal
resistance of the PTC over-current protection apparatus 12 is
increased, the power consumption will increase such that the
working voltage of the first integrated circuit 13 connected with
the protection apparatus will be dropped.
[0009] Furthermore, the printed circuit board has the trend of
small size and high density at the present day. Therefore, the
number of internal layers of the PCB has increased to be even more
than 12, especially in small, thin and light products, such as
cellular phone, personal digital assistant (PDA) and digital
camera, etc. Generally, a main process of processes for
manufacturing the multi-layer printed circuit board is a so-called
build-up process. The build-up process forms the printed circuit
board by stacking a circuit layer and an insulation layer one by
one, such that a multi-layer PCB having vias and high density is
formed. FIGS. 2(a) to 2(e) depicts a conventional build-up process.
In FIG. 2(a), a substrate 20 is provided, which is composed of a
glass fiber and a resin. A first conductive layer 21, such as a
copper foil, is applied to the surface of the substrate 20. In FIG.
2(b), the first conductive layer 21 is etched by a chemical method
for forming an isolating area 22. In FIG. 2(c), an insulating layer
23 is applied to the surface of the first conductive layer 21. In
FIG. 2(d), the insulating layer 23 is etched by a laser or chemical
method for forming a conductive via 24. In FIG. 2(e), a second
conductive layer 25 is applied to the insulating layer 23 by a
method of plating or electroless plating. In the above-mentioned
plating process, the conductive via 24 will be filled with a
conductive material to conduct the first conductive layer with the
second conductive layer. Therefore, the conductive layer and the
insulating layer can be stacked one by one if the above steps are
repeated over and over, and thus a multi-layer printed circuit
board is formed. Moreover, any two conductive layers of the printed
circuit board can also be connected by a electrically conductive
hole. The electrically conductive hole is formed by mechanical
drilling and plating the hole, electrolessly plating the hole or
filling the hole with a conductive paste so as to connect two
conductive layers together. FIG. 3 depicts a diagram of the
electrically conductive hole; wherein a first conductive layer 31
is connected to a second conductive layer 32 and a second terminal
point 36 through a first conductive hole 33. However, if the first
conductive layer 31 needs to be connected to a first terminal point
35 without being connected to a second conductive layer 32, an
etched area 37 is formed around a second conductive hole 34 in the
second conductive layer 32, and thus the second conductive hole 34
and the second conductive layer 32 are isolated.
[0010] Since the size of the printed circuit board 10 is decreased,
the area for mounting the electrical apparatus is limited.
Therefore, how to increase the utilization area of the printed
circuit board is a critical problem to be tackled with. For this
purpose, the present invention discloses a printed circuit board
having an embedded internal over-current protection apparatus to
increase the utilization area of the PCB and decrease the normal
resistance. Moreover, the surface of the PCB can accommodate more
devices, since the over-current protection apparatus mounted on the
PCB surface is not necessary. On the other hand, an external damage
to the surface mount over-current protection apparatus will be
avoided.
SUMMARY OF THE INVENTION
[0011] A major object of the present invention is to provide a
printed circuit board (PCB) with an increased area of an embedded
internal functional element for the benefit of decreasing the
normal resistance. Thus, the power consumption of this invention is
much lower than an over-current protection apparatus being surface
mounted on the PCB surface and the dropping of the working voltage
will also be significantly reduced.
[0012] A second object of the present invention is to make the
embedded functional element constituted by one or more than one
internal layers of the printed circuit board. Since this embedded
functional element design utilizes more effective area of
over-current protection apparatus without utilizing any area of PCB
surface, the resulted electrical rating of embedded functional
element in the printed circuit board such as maximum working
current is higher.
[0013] A third object of the present invention is to make the
functional element to constitute a resistive or sensing element,
and thus the number of the apparatuses mounted on the surface of
the PCB is decreased and the utilization rate of the PCB is
improved.
[0014] In order to achieve the above objects and to avoid the
disadvantages of the prior art, the present invention discloses a
PCB, characterized in that besides the conductive layer and the
insulating layer, the PCB further comprises at least one functional
element either current-sensitive or temperature-sensitive layer,
such as the positive temperature coefficient (PTC) element,negative
temperature coefficient (NTC) element, or zero temperature
coefficient (ZTC) element. The functional element comprises a
functional material, an upper electrode and a lower electrode, and
the functional material is selected from the group consisting of
PTC material, ZTC material and NTC material. If the PTC element is
applied in the present invention, the normal resistance of the
present invention will be smaller than that of conventional PTC
protection apparatus since the area of the PTC element of the
present invention is larger than that of conventional PTC
protection apparatus. Moreover, through an electrically conductive
hole, an upper electrode and a lower electrode respectively lying
on the top and bottom surfaces of the functional PTC element are
respectively connected with an apparatus mounted on the surface of
the PCB to form a connecting circuit. Thus, the PTC overcurrent
protection apparatus which is usually mounted on the surface of the
PCB is eliminated, and the surface utilization rate of the PCB will
be improved while the over-current protection mechanism through the
entire circuitry is still maintained.
[0015] The foregoing and other objects and advantages of the
invention and the manner in which the same are accomplished will be
clearly shown based on the following detailed description taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 depicts a schematic diagram showing connection of a
conventional PTC over-current protection apparatus;
[0017] FIGS. 2(a) to 2(e) depicts the steps of a conventional
build-up process;
[0018] FIG.3 depicts the diagram of a conventional electrically
conductive hole;
[0019] FIG. 4 depicts a perspective view of a first embodiment of
the present invention;
[0020] FIG. 5 depicts a perspective view of a second embodiment of
the present invention;
[0021] FIG. 6 depicts a temperature-resistance diagram for the PTC,
NTCand ZTC material.
DETAILED DESCRIPTION OF THE INVENTION
[0022] FIG. 4 depicts a perspective view of a first embodiment of
the present invention. One of the technical features of the present
invention is to make the functional element be a part of a printed
circuit board 10. The functional element layer of the present
invention is not limited to one layer or multi-layers. In one
preferred embodiment of the present invention, the functional
element is a PTC element. The printed circuit board 10 comprises an
embedded internal PTC material layer 41, which is covered with an
upper electrode 44 and a lower electrode 45 respectively on top and
bottom surfaces of the PTC material layer 41. The function of the
combination of the PTC material layer 41, the upper electrode 44
and the lower electrode 45 is equivalent to the function of the PTC
over-current protection apparatus 12 shown in FIG. 1. A power
supply 11 is connected to the lower electrode 45 through a first
electrically conductive hole 42 and then to the upper electrode 44
through the PTC material layer 41. The upper electrode 44 is
connected to a first integrated circuit device 13 through a second
electrically conductive hole 43. The first electrical conductive
hole 42 is isolated from the upper electrode 44 by a first etched
area 46 and the second electrically conductive hole 43 is also
isolated from the lower electrode 45 by a second etched area 47, to
define a connection between the power supply 11 and the first
integrated circuit device 13. Therefore, the circuit from the power
supply 11 through the PTC material 41 to the first integrated
circuit 13 is equivalent to the circuit of FIG. 1. The first and
the second electrically conductive holes 42, 43 are formed by
mechanical drilling and then electro-plating the hole, electroless
plating the hole or filling the hole with a conductive paste. The
first etched area 46 and the second etched area 47 are formed by a
chemical etching process. In addition, the process for forming the
PCB of the present invention is unrestricted, and it can thus be
the above-mentioned build-up process or the vias or the other
related process.
[0023] The PTC material layer 41 is made of a positive temperature
coefficient conductive composition comprising a polymer and a
conductive filler. The polymer of the PTC material is a crystalline
polymer selected from the group consisting of polyethylene,
polypropylene, polyoctylene, polyvinylidene chlorideand a mixture
thereof. The conductive filler is dispersed in the above polymer
and is selected from the group consisting of carbon black, metal
powder, conductive ceramic powder and a mixture thereof. To improve
sensitivity and physical properties of the PTC material layer, the
PTC conductive composition further comprises an additive, including
a photo initiator, cross-link agent, coupling agent, dispersing
agent, stabilizer, anti-oxidant and nonconductive anti-arcing
filler. The upper electrode 44 and the lower electrode 45 are both
made of a metal foil, such as copper, nickel, aurum and the alloy
thereof. Those electrodes 44 and 45 are formed by electroplating,
electroless plating or hot pressing technology, in which the metal
foil in the hot pressing process is attached to the PTC material
layer with its nicro-rough surface.
[0024] Since the conventional PTC over-current protection apparatus
12 is replaced by the combination of the embedded PTC material
layer 41, the upper electrode 44 and the lower electrode 45, the
amount of the apparatuses mounted on the surface of the PCB is
decreased and thus the utilization rate of the PCB surface is
increased. Moreover, because the surface area of the PTC element is
increased, the normal resistance measured according to the
above-mentioned conventional formula is decreased substantially.
Thus, the increase in the power consumption of the entire circuitry
and the decrease in the supplied working voltage of the first
integrated circuit are avoided. In addition, the PTC material layer
of the PCB 10 can be made of at least two adjacent or non-adjacent
layers. The adjacent or non-adjacent PTC material layers can be
connected in parallel for further decreasing the normal
resistance.
[0025] FIG. 5 depicts a perspective view of a second embodiment of
the present invention. The PTC material layer 41 shown in FIG. 4 is
divided into several sections according to the requirement of
resistance and location. For example, the PTC material layer is
divided into a first PTC material section 51, a second PTC material
section 52, a third PTC material section 53 and a fourth PTC
material section 54. Each of the PTC material sections executes not
only the over-current protection function mentioned above but also
the resistance function. For example, the first integrated circuit
13 is electrically connected to an upper electrode 55 through a
third conductive hole 56 and a second integrated circuit 14 is
electrically connected to a lower electrode 57 through a fourth
conductive hole 58. Thus, an electrical circuit is formed from the
first integrated circuit 13 to the second integrated circuit 14 due
to the normal resistance effect of the second embedded PTC section
52. In other words, the PTC section characteristics of the present
invention can be applied to replace conventional resistors to
increase the surface utilization rate of the PCB 10.
[0026] In another preferred embodiment of the present invention,
the functional material layer 41 is made of the negative
temperature coefficient (NTC) conductive composition or the zero
temperature coefficient (ZTC) conductive composition. The NTC
conductive composition comprises a polymer and a conductive filler.
The polymer of the composition is a crystalline polymer or a
noncrystalline polymer, which is selected from the group consisting
of polyethylene, polypropylene, polyoctylene, polyvinylidene
chloride and a mixture thereof. The conductive filler is dispersed
in the polymer and is selected from the group consisting of a
carbon black, metal powder, conductive ceramic powder and a mixture
thereof Moreover, the ZTC conductive composition comprises a
polymer and a conductive filler. The polymer is a crystalline
polymer or a noncrystalline polymer, which is selected from the
group consisting of a polyethylene, polypropylene, polyoctylene,
polyvinylidene chloride and a mixture thereof. The conductive
filler is dispersed in the polymer and is selected from the group
consisting of a carbon black, metal powder, conductive ceramic
powder and a mixture thereof. FIG. 6 depicts a
temperature-resistance diagram for the PTC NTC and ZTCmaterials.
Therefore, the PCB of the present invention has not only the
function of the resistor but also the function of the temperature
sensor.
[0027] The methods and features of this invention have been
sufficiently described in the above examples and descriptions. It
should be understood that any modifications or changes without
departing from the spirits of the invention are intended to be
covered in the protection scopes of the invention.
* * * * *