KR20070000833A - Printed circuit board mounted led - Google Patents

Abstract

A printed circuit board mounted with an LED is provided to improve heat emitting performance by widening heat transferring cross sections of first and second copper bumpers. In a printed circuit board(60) mounted with an LED(62), a copper wiring and a first copper layer(61a) are separately formed at an upper surface of the printed circuit board(60). The LED(62) is mounted at one part of the first copper layer(61a). A second copper layer(63) is installed at a lower surface of the printed circuit board(60). First and second lead wires(64a,64b) are connected to a cathode electrode and an anode electrode of the LED(62) contacted to the first copper layer(61a). A first copper bumper(66a) fills a first via hole formed on the printed circuit board(60) of the lower part of the LED(62). A plurality of second copper bumpers(66b) fills a second via holes formed on the circumference of the printed circuit board(60) mounted with the LED(62).

Description

Printed circuit board mounted with LED {PRINTED CIRCUIT BOARD MOUNTED LED}

1 is a structural cross-sectional view of a printed circuit board mounted with an LED according to the prior art.

FIG. 2 is a bottom side view of the printed circuit board of FIG. 1.

3 is a cross-sectional view of a printed circuit board on which an LED is mounted according to another conventional technology.

4 and 5 are top and bottom side views of the printed circuit board on which the LED of FIG. 3 is mounted.

6 is a structural cross-sectional view of a printed circuit board on which an LED is mounted according to an embodiment of the present invention.

7 and 8 are top and bottom side views of a printed circuit board on which the LED of the present invention is mounted.

9a and 9b are experimental results showing the structure of a printed circuit board according to the prior art and the heat transfer performance according thereto.

10A and 10B are experimental results showing the structure of a printed circuit board and heat transfer performance according to the related art.

11A and 11B are experimental results showing the structure of a printed circuit board to which the technique of the present invention is applied and the heat transfer performance thereof.

12A and 12B are experimental results showing the structure of a printed circuit board to which the technology of the present invention is applied and the heat transfer performance thereof.

Explanation of symbols on the main parts of the drawings

60, 110, 120: printed circuit board 61: copper wiring

61a: first copper layer 62, 111, 121: LED

63: 2nd copper layer 64a, 64b: 1st, 2nd lead wire

66a: first copper bumper 66b: second copper bumper

112, 122: copper bumper 113, 123: copper layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board, and more particularly, to a printed circuit board on which an LED suitable for quickly dissipating heat generated from an LED is mounted.

CRT (Cathode Ray Tube), one of the commonly used display devices, is mainly used for monitors such as TVs, measuring devices, information terminal devices, etc., but the miniaturization of electronic products due to the weight and size of CRT itself It was unable to actively respond to the demand for weight reduction.

Therefore, in the trend of miniaturization and light weight of various electronic products, CRT has a certain limit in weight and size, and is expected to be replaced. Liquid crystal display (LCD) and gas discharge using electro-optic effects Plasma Display Panel (PDP) and Electro Luminescence Display (ELD) using the electroluminescent effect, among others, are being actively studied for the liquid crystal display device.

In order to replace the CRT, a liquid crystal display device having advantages such as small size, light weight, and low power consumption has been recently developed to be able to perform a sufficient role as a flat panel display device, and not only a monitor of a laptop computer but also a desktop computer. The demand for liquid crystal display devices continues to increase as they are used in monitors and large information display devices.

On the other hand, since most of the liquid crystal display devices are light-receiving elements that display an image by controlling the amount of light source coming from the outside, a separate light source for illuminating the liquid crystal panel, that is, a backlight unit, is necessary. The unit is divided into the edge method and the direct method according to the position where the lamp unit is installed.

Light sources constituting the backlight unit include a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), an external electrofluorescent lamp (EEFL), and the like.

CCFL uses a fluorescent discharge tube in which mercury gas containing argon, neon, and the like is sealed at a low pressure in order to take advantage of a penning effect. Electrodes are formed at both ends of the tube, and the cathode is formed in a wide plate shape.When voltage is applied, as in the sputtering phenomenon, charged particles in the discharge tube collide with the plate-shaped cathode to generate secondary electrons, which excite surrounding elements to excite the plasma. Form.

These elements emit strong ultraviolet light, which in turn excites the phosphor, causing the phosphor to emit visible light.

In the EEFL, mercury gas is contained in the fluorescent discharge tube, and external electrodes are formed outside the tube.

However, as described above, since CCFL and EEFL use mercury, there is a risk of polluting the environment. Therefore, LEDs are in the spotlight as such environmentally friendly light sources.

However, such LEDs have low light efficiency and generate a large amount of heat, thereby degrading the reliability of the LED package including the light emitting chip.

In order to solve this problem, the printed circuit board on which the LED is mounted uses an expensive aluminum printed circuit board having excellent heat dissipation performance instead of using a plastic insulating material. However, when using an aluminum printed circuit board as described above, there is a problem that the price competitiveness is significantly lowered.

Hereinafter, a printed circuit board on which a conventional LED is mounted will be described with reference to the accompanying drawings.

1 is a structural cross-sectional view of a printed circuit board on which an LED is mounted according to the prior art, and FIG. 2 is a bottom side view of the printed circuit board of FIG. 1.

In the printed circuit board on which the LED according to the prior art is mounted, as illustrated in FIGS. 1 and 2, the copper layer 11 and the copper wiring 11a are separated from each other and formed on the printed circuit board 10. The LED 12 is mounted in one region above the copper layer 11.

In addition, first and second lead wires 13a and 13b for applying a driving voltage to the cathode electrode and the anode electrode of the LED 12 are contacted on the copper layer 11.

At this time, the copper layers 11 around the first and second lead wires 13a and 13b are patterned and isolated so that the first and second lead wires 13a and 13b are not shorted.

In this case, as shown in FIG. 2, the printed circuit board 10 is integrally formed by connecting both the lower portion and the periphery of the LED 12.

The LED mounting printed circuit board 10 configured as described above is made of a plastic material which is more competitive than aluminum material.

However, although the printed circuit board is made of a plastic material as described above, the price is competitive, it is difficult to dissipate heat generated from the LED efficiently, there is a problem in reliability.

Next, a printed circuit board on which an LED is mounted according to another conventional technique for solving the heat dissipation problem will be described.

3 is a cross-sectional view of a printed circuit board on which an LED is mounted according to another conventional technology, and FIGS. 4 and 5 are top and bottom views of the printed circuit board on which the LED of FIG. 3 is mounted.

In the printed circuit board on which the LED according to another conventional technology is mounted, as illustrated in FIGS. 3, 4, and 5, a copper wiring 31 and a first copper layer 31a are formed on an upper surface of the printed circuit board 30. ) Is isolated, the LED 32 is mounted in one region above the first copper layer 31a, and the second copper layer 33 is formed on the bottom surface of the printed circuit board 30. At this time, the printed circuit board 30 is made of a low-cost plastic.

First and second lead wires 34a and 34b for applying a driving voltage to the cathode electrode and the anode electrode of the LED 32 are contacted on the first copper layer 31a.

At this time, the first copper layer 31a is patterned and isolated from the copper wiring 31 around the first and second lead wires 34a and 34b so that the first and second lead wires 34a and 34b are not shorted. .

4 and 5, a plurality of first via holes 35a are formed below the LED 32, and the printed circuit board 30 is mounted around the printed circuit board 30. Second via holes 35b are formed to penetrate the substrate 30.

A copper bridge 36 is formed on the side surfaces of the first and second via holes 35a and 35b to serve as bridges for connecting the first and second copper layers 31a and 33.

The above-described printed circuit board 30 in which the LED is mounted has a very low thermal conductivity (about 0.35 W / mK) of the printed circuit board 30 made of plastic, which does not diffuse heat generated by the LED 32. Therefore, the second copper layer 33 is formed under the printed circuit board 30, and the first via hole 35a is formed under the LED 32, and the first lower portion is formed through the copper bridge 36. Heat is emitted to the second copper layer 33, and second via holes 35b are formed in the printed circuit board 30 around the LEDs 32, and the upper copper wirings 31 are formed through the copper bridges 36. Heat is transferred to heat.

However, typically, the copper bridge 36 and the first and second copper layers 31a and 33 formed in the first and second via holes 35a and 35b and the printed circuit board 30 have a thickness thereof. There is a limit to heat dissipation because it is very thin, about 70㎛.

In addition, the centers of the first and second via holes 35a and 35b are perforated to allow air to flow, thereby reducing the heat transfer area, and the heat conductivity of the air is extremely low (approximately 0.026 W / mK). Falls.

As described above, since the heat transfer area through the first and second via holes 35a and 35b is extremely limited, there is a limit to improving heat dissipation performance.

Next, the heat dissipation performance of the conventional LED-mounted printed circuit boards configured as described above will be described with reference to experimental data.

9A and 9B are experimental results showing the structure of a printed circuit board according to the prior art and the heat transfer performance thereof, and FIGS. 10A and 10B illustrate the structure and the heat transfer performance of the printed circuit board according to another conventional technique. The experimental results are shown.

First, in the structure shown in FIG. 9A, the printed circuit board 90 on which the LED 91 is mounted is integrally formed without a hole, and the copper layer 92 is formed only on the lower portion of the printed circuit board 90. In this case, the conventional FIG. 1 is shown in a simplified manner. At this time, the printed circuit board 90 is made of plastic.

When the printed circuit board 90 is configured in this manner, as shown in FIG. 9B, when heat is generated by driving the LED 91, the LED 91 is heated between a minimum of 67 ° C. and a maximum of 178 ° C. It can be seen that it has a distribution.

Next, in the structure shown in FIG. 10A, an LED 101 is mounted in one region of the printed circuit board 100, and a via hole 102 is disposed below the printed circuit board 100 on which the LED 101 is mounted. The copper layer 103 is formed on the bottom surface of the printed circuit board 100, and the copper bridge 104 is formed on the side of the via hole 102 to be in contact with the LED 101 and the copper layer 103. In this case, the configuration of FIG. 3 is shown in a simplified manner. At this time, the printed circuit board 100 is made of plastic.

When the printed circuit board 100 is configured as described above, as shown in FIG. 10B, when heat is generated by driving the LED 101, the LED 101 is between a minimum of 75 ° C. and a maximum of 140 ° C. It can be seen that it has a heat distribution.

The above-described printed circuit boards in which the conventional LEDs are mounted have the following problems.

First, the configuration in which the printed circuit board is integrally formed of a plastic material is competitive in price, but it is difficult to efficiently dissipate heat generated from the LED, thereby causing a problem in reliability.

Second, the heat dissipation structure through the via hole is not only extremely limited in the heat transfer area because the center of the via hole is perforated through the air, and the heat conduction of the air is extremely low. There is a limit to improving performance.

The present invention has been made to solve the above problems, an object of the present invention is to provide a printed circuit board mounted with an LED suitable for rapidly dissipating heat generated from the LED to improve the heat dissipation performance.

It is still another object of the present invention to provide a printed circuit board on which an LED is suitable for improving the cost competitiveness of a printed circuit board on which an LED is mounted and for improving productivity by securing surface mount technology (SMT) workability.

According to an embodiment of the present invention, a printed circuit board on which an LED is mounted includes: a copper wiring and a first copper layer formed on an upper surface of the printed circuit board; An LED mounted on one region of the first copper layer; A second copper layer formed on the bottom surface of the printed circuit board; First and second lead wires connected to a cathode electrode and an anode electrode of the LED contacted on the first copper layer; A first copper bumper filling a first via hole formed in the printed circuit board under the LED; And a plurality of second copper bumpers filling the second via holes formed at an edge of the printed circuit board on which the LED is mounted.

The printed circuit board is characterized in that it is made of a low-cost plastic.

The first copper layer to which the first and second lead wires contact is patterned and isolated from the peripheral copper wiring.

The first copper bumper may be formed in the width of the LED in order to increase the heat transfer area.

The first copper bumper is connected to the second copper layer formed under the printed circuit board, and the second copper bumper is connected to the second copper layer and the copper wiring.

The second copper bumper around the LED is further characterized in that it is configured to freely adjust the size and number.

와 같은 식으로 나타낼 수 있고, 이 때 상기 'T'는 상기 LED의 온도, 'Tref'는 대략 25℃의 상온, 'd'는 제 1, 제 2 구리범퍼의 높이, 'Q'는 상기 LED에서 발생하는 열, 'k'는 열전도도이고 'A'는 상기 제 1, 제 2 구리범퍼의 단면적을 의미하는 것을 특징으로 한다. The heat transfer characteristics of the LED

In this case, 'T' is the temperature of the LED, 'Tref' is a room temperature of approximately 25 ℃, 'd' is the height of the first and second copper bumpers, 'Q' is the LED Heat generated at 'k' is thermal conductivity and 'A' is characterized in that it means the cross-sectional area of the first and second copper bumper.

Hereinafter, a printed circuit board on which an LED is mounted according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

6 is a cross-sectional view of a printed circuit board on which an LED is mounted according to an embodiment of the present invention, and FIGS. 7 and 8 are top and bottom views of a printed circuit board on which an LED of the present invention is mounted.

In the printed circuit board on which the LED is mounted according to the embodiment of the present invention, as illustrated in FIGS. 6, 8, and 9, the copper wiring 61 and the first copper layer (not shown) on the upper surface of the printed circuit board 60 ( 61a) is isolated, the LED 62 is mounted in one region above the first copper layer 61a, and the second copper layer 63 is formed on the bottom surface of the printed circuit board 60. At this time, the printed circuit board 60 is made of a low-cost plastic.

First and second lead wires 64a and 64b for applying a driving voltage to the cathode electrode and the anode electrode of the LED 62 are contacted on the first copper layer 61a.

At this time, the first copper layer 61a is patterned and isolated from the copper wiring 61 around the first and second lead wires 64a and 64b so that the first and second lead wires 64a and 64b are not shorted. .

As shown in FIGS. 7 and 8, the printed circuit board 60 has a first copper bumper 66a formed to fill the first via hole formed under the LED 62. A second copper bumper 66b is formed to fill the second via holes formed in the printed circuit board 60 around the package. Although the width of the first copper bumper 66a may be arbitrarily formed, the first copper bumper 66a may be formed by the width of the entire lower portion of the LED 62 to increase the heat transfer area.

At this time, the first copper bumper 66a filled in the first via hole is connected to the second copper layer 63 formed under the printed circuit board 60, and the second copper bumper 66b is connected to the second copper layer ( 63 is connected to the copper wiring 61.

Accordingly, the first and second copper bumpers 66a and 66b serve as heat transfer paths for transferring heat generated from the LED 32 to the second copper layer 63 and the copper wiring 61.

The printed circuit board according to the present invention configured as described above has a second copper layer on the bottom surface of the printed circuit board 60 through the first copper bumper 66a in which heat generated from the LED 62 is primarily wide. Widely diffused and radiated to 63, and the remaining heat is widely diffused and radiated to the upper copper wiring 61 through the second copper bumper 66b formed around the LED 62.

As described above, since the heat transfer cross-sectional areas of the first and second copper bumpers 66a and 66b are wide, the heat dissipation performance is greatly improved.

In addition, the second copper bumper 66b around the LED 62 may be configured by freely adjusting its size and number. In this way, not only can the heat generated from the LED 62 be more effectively released, but also the desired temperature can be easily adjusted.

The reason why the printed circuit board 60 is made of plastic is to proceed by soldering when the first and second lead wires 64a and 64b are contacted with the first copper layer 61a of the LED 62. When the printed circuit board 60 is made of aluminum, the heat of the first copper layer 61a is well discharged through the aluminum, so that lead does not melt well, so that the first and second lead wires 64a and 64b are soldered. This is difficult to fix. As such, when the printed circuit board is made of aluminum, it is difficult to secure not only high price but also surface mount technology (SMT) workability.

In addition, even when the printed circuit board 60 having the above structure is attached on another structure, in particular, a heat transferable structure, the contact area is improved, and heat transfer to the outside is more actively performed. That is, in addition to improving the heat dissipation performance of the printed circuit board itself, it is possible to improve the heat dissipation performance when mounted on other structures.

Such heat transfer characteristics are represented by the following [Formula 1].

-----[식1]

----- [Equation 1]

If [Expression 1] is expressed in terms of T, it is the same as [Formula 2].

-----[식2]

----- [Equation 2]

'Q' is the heat generated in the LED, 'k' is the thermal conductivity, 'A' is the cross-sectional area of the first and second copper bumpers, 'T' is the temperature of the LED, 'Tref' is approximately 25 ℃ room temperature And 'd' means the height of the first and second copper bumpers.

As shown in [Equation 2], if the cross-sectional area A of the copper bumper for heat transfer is large, the value of dQ / kA is decreased, thereby lowering the temperature of the LED.

As shown in [Formula 1] and [Formula 2], the temperature of the LED depends on the cross-sectional area of the copper bumper, and the copper bumper is formed to cover the entire via hole rather than the copper bridge formed along the side of the conventional via hole. The configured invention can lower the temperature of the LED more effectively.

Next, the heat dissipation performance of the printed circuit board with the LED of the present invention having the above configuration will be described with reference to the experimental data.

11A and 11B are experimental results showing the structure of a printed circuit board to which the technology of the present invention is applied and the resulting heat transfer performance. The experimental results showing the performance.

First, in the structure shown in FIG. 11A, the LED 111 is mounted in one region of the printed circuit board 110, and the LED 111 is narrower than the width of the LED 111 on the printed circuit board 110 under the LED 111. When there is a via hole, and the via hole is filled by the copper bumper 112, and the copper layer 113 is formed below the printed circuit board 110, when the width is narrower than the copper bumper shown in Figure 6 of the present invention It is presented. At this time, the printed circuit board 110 is made of plastic.

In the case where the printed circuit board 110 is configured as described above, as shown in FIG. 11B, when heat is generated by driving the LED 111, the LED 111 generates heat between a minimum of 77 ° C. and a maximum of 134 ° C. FIG. It can be seen that it has a distribution.

Next, in the structure shown in FIG. 12A, an LED 121 is mounted in one region of the printed circuit board 120, and a via hole is formed in the printed circuit board 120 under the LED 121. The copper bumper 122 fills the via hole, and the copper layer 123 is formed on the lower portion of the printed circuit board 120. The copper bumper 122 has a wide cross section as wide as that of the LED 121. have. At this time, the printed circuit board 120 is made of plastic. This is a simplified representation of Figure 6 of the present invention.

In the case where the printed circuit board 120 is configured as described above, as shown in FIG. 12B, when heat is generated by driving the LED 121, the LED 121 generates heat between at least 81 ° C. and at most 115 ° C. It can be seen that it has a distribution.

The above experimental result diagram is compared with the conventional experimental result diagram as follows.

In the conventional printed circuit board, when the temperature distribution of the LED is configured as shown in FIG. 9A, the temperature distribution of the LED shows a temperature difference of 111 ° C from minimum 67 ° C to maximum 178 ° C. The temperature difference of 65 degreeC was shown as the maximum 140 degreeC in 75 degreeC.

In contrast, when the printed circuit board of the present invention is configured as shown in FIG. 11A, the temperature distribution of the LED shows a temperature difference of 57 ° C., with a minimum of 77 ° C. and a maximum of 134 ° C. Showed a temperature difference of 34 ° C. with a minimum of 81 ° C. and a maximum of 115 ° C.

As a result of the above, if the copper bumper is configured as in the present invention, it is possible to not only lower the maximum temperature of the LED, but also to reduce the difference between the minimum and maximum temperature of the LED. The smallest minimum and maximum temperature differences indicate that the heat generated by the LEDs has been effectively dissipated.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the above embodiments, but should be defined by the claims.

The printed circuit board on which the LED according to the present invention is mounted has the following effects.

First, by constructing the printed circuit board made of plastic, it is possible to increase the price competitiveness and to reduce the weight than when composed of aluminum.

Second, by configuring the copper bumper to fill the via hole in the printed circuit board, it is possible to improve the heat dissipation performance of the LED by increasing the heat transfer area.

Third, the printed circuit board is made of plastic, thereby facilitating SMT work for mounting the first and second lead wires of the LED, thereby improving productivity.

Claims (7)

A copper wiring and a first copper layer formed on an upper surface of the printed circuit board; An LED mounted on one region of the first copper layer; A second copper layer formed on the bottom surface of the printed circuit board; First and second lead wires connected to a cathode electrode and an anode electrode of the LED contacted on the first copper layer; A first copper bumper filling a first via hole formed in the printed circuit board under the LED; And a plurality of second copper bumpers filling second via holes formed at edges of the printed circuit board on which the LEDs are mounted. The method of claim 1, The printed circuit board is a printed circuit board, the LED is mounted, characterized in that consisting of a low-cost plastic. The method of claim 1, And the first copper layer contacted with the first and second lead wires is patterned and isolated from the surrounding copper wiring. The method of claim 1, The first copper bumper is a printed circuit board, the LED is mounted, characterized in that to increase the heat transfer area, the width of the LED can be formed. The method of claim 1, The first copper bumper is connected to the second copper layer formed on the lower portion of the printed circuit board, the second copper bumper is connected to the second copper layer and the copper wiring is mounted LED Printed circuit board. The method of claim 1, The second copper bumper around the LED further comprises the size and number of freely configured to configure the printed circuit board mounted with the LED. The method of claim 1, The heat transfer characteristics of the LED

Wherein 'T' is the temperature of the LED, 'Tref' is a room temperature of approximately 25 ℃, 'd' is the height of the first and second copper bumpers, 'Q' is the LED The heat generated, 'k' is a thermal conductivity and 'A' means a cross-sectional area of the first and second copper bumper, the printed circuit board mounted with the LED.

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