U.S. patent application number 11/600059 was filed with the patent office on 2007-06-21 for slim type backlight unit.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Ho Sik Ahn, Chul Hee Yoo.
Application Number | 20070139929 11/600059 |
Document ID | / |
Family ID | 37722112 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070139929 |
Kind Code |
A1 |
Yoo; Chul Hee ; et
al. |
June 21, 2007 |
Slim type backlight unit
Abstract
A backlight unit of the invention is reduced in thickness,
weight and manufacturing costs but improved in heat releasing
efficiency. In the backlight unit, a flexible printed circuit board
has at least one through hole perforated therein. An LED package is
disposed on a top portion of the flexible printed circuit board
corresponding to the through hole. The backlight unit of the
invention employs the flexible printed circuit board in place of a
metal printed circuit board as a means to conduct current to the
LED package. This produces a slimmer and lighter backlight unit and
also saves manufacturing costs. In addition, the LED package is
directly bonded onto a bottom plate by a heat conducting adhesive,
thereby ensuring heat generated from the LED package to be released
more quickly.
Inventors: |
Yoo; Chul Hee; (Suwon,
KR) ; Ahn; Ho Sik; (Incheon, KR) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
|
Family ID: |
37722112 |
Appl. No.: |
11/600059 |
Filed: |
November 16, 2006 |
Current U.S.
Class: |
362/294 ;
362/249.04 |
Current CPC
Class: |
H05K 2201/10106
20130101; H05K 3/0061 20130101; H05K 2201/0209 20130101; H05K
3/4069 20130101; H05K 2201/09072 20130101; F21V 29/70 20150115;
G02F 1/133603 20130101; H05K 1/189 20130101; H05K 1/0206
20130101 |
Class at
Publication: |
362/294 ;
362/249 |
International
Class: |
F21V 29/00 20060101
F21V029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 2005 |
KR |
10-2005-0124444 |
Claims
1. A backlight unit comprising: a flexible printed circuit board
having at least one through hole perforated therein; and an LED
package disposed on a top portion of the flexible printed circuit
board corresponding to the through hole.
2. The backlight unit according to claim 1, wherein the flexible
printed circuit board has an electrically-conducting pattern formed
on a top surface thereof, wherein the LED package further comprises
a lead frame connected to the pattern to receive current.
3. The backlight unit according to claim 1, wherein the flexible
printed circuit board is made of polyimide.
4. The backlight unit according to claim 1, wherein the flexible
printed circuit board further comprises a reinforcement plate
provided on a top surface or an underside surface thereof.
5. The backlight unit according to claim 1, further comprising: a
bottom plate where the flexible printed circuit board is mounted;
and a heat conducting adhesive formed in the through hole to
connect an underside surface of the LED package with a top surface
of the bottom plate.
6. The backlight unit according to claim 5, wherein the LED package
is configured such that the heat conducting adhesive is adhered in
an area where a heat sink is disposed.
7. The backlight unit according to claim 5, wherein the bottom
plate is made of a metallic material.
Description
CLAIM OF PRIORITY
[0001] This application claims the benefit of Korean Patent
Application No. 2005-124444 filed on Dec. 16, 2005 in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a backlight unit
incorporating a light emitting diode (LED) as a light source, and
more particularly, to a slimmer backlight unit which is reduced in
thickness, weight and manufacturing costs and improved in heat
releasing efficiency.
[0004] 2. Description of the Related Art
[0005] A light emitting diode (LED) converts an electrical signal
into an infrared ray, visible light or other form by using
properties of a compound, and is used for a signal
transmitting/receiving device.
[0006] In general, the LED is utilized in electronic home
appliances, remote controllers, display boards, displays and
various kinds of automation devices. The LED is largely broken down
into an Infrared Emitting Diode (IRED) and a Visible Light Emitting
Diode (VLED).
[0007] Such an LED is adopted adequately for e.g., the electronic
home appliances and display boards depending on intensity of light
outputted therefrom. A smaller and slimmer trend in the
telecommunication device has given rise to a surface mount device,
which is directly mountable on a printed circuit board.
[0008] Also, with broader applicability of the LED, higher
brightness is increasingly required especially in daily appliances
such as electric lights and rescue signal lights. Thus recently a
high output LED is in wide use. But this high output LED generates
heat significantly and accordingly when mounted in e.g., a
backlight unit with a small mounting area, heat from the LED fails
to be released properly, thereby undermining efficiency of the
product or causing malfunction. To overcome such a problem,
recently a backlight unit with excellent heat releasing properties
has been conceived.
[0009] With reference to the accompanying drawings, a conventional
backlight unit will be explained in detail.
[0010] FIG. 1 is an exploded perspective view illustrating the
conventional backlight unit and FIG. 2 is a cross-sectional view
illustrating the conventional backlight unit.
[0011] As shown in FIGS. 1 and 2, the conventional backlight unit
includes a bottom plate 10 for mounting each part therein, a Metal
Core Printed circuit Board (MCPCB) 20 disposed on the bottom plate,
an LED package 30 mounted on the MCPCB 20 and an optical sheet 40
for processing light generated from the LED package 30.
[0012] Also, the MCPCB 20 has an electrically-conducting pattern 22
formed thereon. The LED package 30 is connected to the pattern 22
by a lead frame 32. Furthermore, a heat conducting adhesive 50 is
disposed between an underside surface of the LED package and a top
surface of the MCPCB 20 to fix the LED package.
[0013] Heat generated from the LED package 30 is transferred to the
MCPCB 20 through the heat conducting adhesive 50 and then again to
the bottom plate 10 so as to be released outward. Here, the MCPCB
20 is made of a high heat conductivity metal, thereby releasing
heat generated from the LED package 30 to the outside faster. This
prevents heat generated from the LED package 30 from degrading
efficiency of the product or causing malfunction.
[0014] Such an MCPCB 20 transfers heat from the LED quickly. On the
other hand, the MCPCB 20 is relatively thick and heavy, thereby
adding thickness and weight to an overall backlight unit. In
addition, the MCPCB 20 is expensive, thereby increasing
manufacturing costs of the backlight unit.
SUMMARY OF THE INVENTION
[0015] The present invention has been made to solve the foregoing
problems of the prior art and it is therefore an object according
to certain embodiments of the present invention is to provide a
backlight unit which has electrically-conducting parts with less
thickness and weight, thereby achieving slimness and light weight,
releasing heat generated from the LED package more quickly and
reducing manufacturing costs.
[0016] According to an aspect of the invention for realizing the
object, there is provided a backlight unit including a flexible
printed circuit board having at least one through hole perforated
therein; and an LED package disposed on a top portion of the
flexible printed circuit board corresponding to the through
hole.
[0017] The flexible printed circuit board has an
electrically-conducting pattern formed on a top surface thereof,
wherein the LED package further comprises a lead frame connected to
the pattern to receive current.
[0018] The flexible printed circuit board is made of polyimide.
[0019] The flexible printed circuit board further comprises a
reinforcement plate provided on a top surface or an underside
surface thereof.
[0020] The backlight unit of the invention further includes a
bottom plate where the flexible printed circuit board is mounted;
and a heat conducting adhesive formed in the through hole to
connect an underside surface of the LED package with a top surface
of the bottom plate.
[0021] The LED package is configured such that the heat conducting
adhesive is adhered in an area where a heat sink is disposed.
[0022] Preferably, the bottom plate is made of a metallic
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0024] FIG. 1 is an exploded perspective view illustrating a
conventional backlight unit;
[0025] FIG. 2 is a cross-sectional view illustrating a conventional
backlight unit;
[0026] FIG. 3 is an exploded perspective view illustrating a
backlight unit according to the invention; and
[0027] FIG. 4 is a cross-sectional view illustrating a backlight
unit according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0028] Preferred embodiments of the present invention will now be
described in detail with reference to the accompanying
drawings.
[0029] FIG. 3 is an exploded perspective view illustrating a
backlight unit of the invention.
[0030] As show in FIG. 3, the backlight unit of the invention
includes a bottom plate 100, a flexible printed circuit board 200,
an LED package 300 and an optical sheet 400. The bottom plate 100
has each part mounted thereon. The flexible printed circuit board
200 has an electrically-conducting pattern formed on a top surface
thereof and through holes 202 perforated therein. The flexible
printed circuit board 200 is provided on the bottom plate 100. The
LED package 300 is disposed on a top portion of the flexible
printed circuit board corresponding to the through holes 202. The
optical sheet 400 is disposed over the LED package 300 to evenly
mix light generated from the LED package 300.
[0031] The LED package 300 includes lead frames 310 each having one
portion connected to the pattern 210 so as to receive current.
Therefore, current applied through the pattern 210 formed on the
flexible printed circuit board 200 is conducted through the lead
frames 310 to the LED package 300. In turn, the LED package emits
light toward the optical sheet 400.
[0032] In this embodiment, the flexible printed circuit board 200
is bar-shaped so that a plurality of LED packages 300 can be
arrayed in a line. Also, the through holes 202 are arranged in a
line at an equal distance along a length direction of the flexible
printed circuit board 200. But the flexible printed circuit board
200 can be shaped or the through holes 202 can be arranged with a
degree of freedom according to position of the LED package 300.
[0033] Furthermore, in this embodiment, to illustrate construction
of the invention more clearly, the pattern 210 and the lead frames
310 have a length along a width direction of the flexible printed
circuit board 200 and are arranged in parallel along a length
direction thereof. However, the pattern 210 and the lead frames 310
can be shaped and arranged with a degree of freedom. For example,
the pattern 210 and the lead frames 310 are arrayed in a line to
have a length along a length direction of the flexible printed
circuit board 210, thereby connected to the through holes 202.
Alternatively, the pattern 210 and the lead frames 310 can be
arranged with a degree of freedom regardless of the position of the
flexible printed circuit board 200. The pattern 210 and lead frames
310 are configured and arranged variously in a conventional
backlight unit, which thus will be explained in no more detail.
[0034] Preferably, the flexible printed circuit board 200 is made
of a material having heat resistance and chemical resistance such
as polyimide. This ensures the flexible printed circuit board 200
not to be deformed or impaired even in a reflow process for joining
the LED package 300 thereto.
[0035] FIG. 4 is a cross-sectional view illustrating a backlight
unit of the invention.
[0036] As shown in FIG. 4, the LED package 300 is disposed on a top
portion of the flexible printed circuit board 200 corresponding to
a through hole 202. A heat conducting adhesive 500 with high heat
conductivity is disposed in the through hole 202. Therefore an
underside surface of the LED package 300 is bonded to a top surface
of a bottom plate 100 by the heat conducting adhesive 500.
[0037] Heat generated by operation of the LED package 300 is
directly transferred to the bottom plate 100 through the heat
conducting adhesive 500 and then released outward. Here,
preferably, the bottom plate 100 is made of a high conductivity
material such as metal so as to receive heat from the LED package
300 more smoothly through the heat conducting adhesive 500.
Preferably, the LED package 300 has the heat conducting adhesive
500 adhered in an area where a heat sink (not illustrated) is
disposed, thereby transferring heat generated to the heat
conducting adhesive 500 more effectively.
[0038] In the conventional backlight unit, heat generated from the
LED package 300 is transferred to the bottom plate through the
metal printed circuit board. Therefore, heat conductivity of the
metal printed circuit board 20 is decreased, no matter how good it
is and accordingly heat releasing effect is reduced (See FIG. 2).
On the contrary, in the backlight unit of the invention, heat
generated from the LED package 300 is directly conducted to the
bottom plate 100 without passing through the flexible printed
circuit board 200. This advantageously increases heat transfer
efficiency and accordingly heat releasing effect.
[0039] Moreover, the metal printed circuit board 20 applied to the
conventional backlight unit typically has a thickness of 2 mm to 3
mm, thereby increasing an overall thickness of the backlight unit.
In contrast, the backlight unit of the invention employs the
flexible printed circuit board 200 having a thickness of about 0.15
mm in place of the metal printed circuit board 20 having a great
thickness, thereby reducing an overall thickness of the
product.
[0040] In addition, the metal printed circuit board 20 adopted for
the conventional backlight unit is made of a metallic material to
enhance heat conductivity. This adds weight to the overall
backlight unit and accordingly raises manufacturing costs thereof.
On the contrary, the backlight unit of the invention utilizes the
flexible printed circuit board 200 having a very small weight,
thereby reducing an overall weight of the backlight unit and
accordingly manufacturing costs thereof.
[0041] In general, the flexible printed circuit board 200 is made
of a flexible material having a thin thickness of 0.15 mm and thus
a very low strength. Therefore, the flexible printed circuit board
200, when bonded, may be crumpled or folded.
[0042] To overcome such problems, a reinforcement plate having
strength greater than that of the flexible printed circuit board
200 may be further provided on a top surface or an underside
surface thereof. Here excessive thickness of the reinforcement
plate increases thickness of the backlight unit and excessive
thinness of the reinforcing plate fails to reinforce the flexible
printed circuit board properly. Thus, preferably the reinforcing
plate has a thickness of about 0.3 mm.
[0043] As described above, even though the reinforcement plate is
further disposed on or underneath the flexible printed circuit
board 200, an overall thickness adds up to merely about 0.45 mm. As
a result, the backlight unit of the invention is reduced in overall
thickness over a conventional backlight unit which employs the
metal printed circuit board having a thickness of 2 mm to 3 mm.
[0044] As set forth above, according to preferred embodiments of
the invention, the backlight unit adopts a flexible printed circuit
board in place of a metal printed circuit board to conduct current
to an LED package. This produces a slimmer and lighter backlight
unit, thereby decreasing manufacturing costs. Also, the LED package
is directly joined onto a bottom plate by a heat conducting
adhesive, thereby releasing heat generated from the LED package
fast.
[0045] While the present invention has been shown and described in
connection with the preferred embodiments, it will be apparent to
those skilled in the art that modifications and variations can be
made without departing from the spirit and scope of the invention
as defined by the appended claims.
* * * * *