JPH11291538A - Led print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an LED print head excellent in heat dissipation at low cost. SOLUTION: The LED print head 21 comprises a printed board 3, a driver IC chip 2 having rear surface bonded onto a printed wiring board 3 and a surface region 2a arranged with a transistor for driving an LED chip 1, the LED chip 1 bonded onto the driver IC chip 2, heat dissipation conductor 7 formed on the printed board 3, and heat transmission wires 6 for connecting the heat dissipation conductor 7 with a region 2c between the transistor region 2a and the LED chip mounting region 2b of the driver IC chip 2. The heat dissipation conductor 7 has opposite ends touching a part of a metal housing serving as a heat sink, i.e., a protrusion on the housing. Heat generated from the light emitting region 1a of the LED chip and the transistor region 2a of the driver IC chip 2 is collected at the region 2c and transmitted quickly to the housing through the heat transmission wires 6 of low thermal resistance, the heat dissipation conductor 7 and the protrusion on the housing before being radiated to the outer air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printer and the like comprising an LED module in which an LED (light emitting diode) chip and a driver IC chip for driving the LED module are integrated, and a substrate to which the LED module is fixed. The present invention relates to an LED print head used as a light source for exposing a photosensitive member.

[0002]

2. Description of the Related Art In the above-described LED print head, when the temperature of an LED chip rises, the amount of radiated light from the LED becomes small, and the printing speed of the printer fluctuates. For this reason, some of the above-mentioned LED print heads are designed to improve the heat radiation of the heat generated by the LED chip and the driver IC chip when the LED emits light and to suppress the temperature rise of the LED module. As such an LED print head, there is one using a substrate disclosed in, for example, JP-A-59-214279. This LED print head uses a laminated substrate in which a plurality of ceramic layers are laminated on a conductor layer, and an LED module in which an LED chip and a driver IC chip are integrated is placed on the ceramic layer side of the laminated substrate. Is fixed to a heat radiating plate made of aluminum or the like, whereby the substrate is formed as a heat-equalizing layer having good heat conduction, thereby suppressing a rise in temperature.

[0003]

However, since the ceramic layer has high hardness and poor workability, and it is difficult to form a multilayer ceramic layer and conductor layer, the above-mentioned laminated substrate has a high manufacturing cost. Further, since the above-mentioned laminated substrate has a lower heat radiation property than a metal base substrate of aluminum or the like, LE
When the power consumption of the D module increases and the amount of heat generated increases, it becomes impossible to cope with the problem and the temperature may increase.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide an LED print head having good heat dissipation and low manufacturing cost.

[0005]

In order to achieve the above object, an LED print head according to the present invention comprises a printed circuit board, a back surface fixed to the surface of the printed circuit board, and an LED printed on the front surface.
In a LED print head including a driver IC chip on which a transistor for driving the LED is formed, and an LED chip fixed on the surface of the driver IC chip, a heat dissipation conductor formed on a surface of a printed circuit board; A driver IC chip surface area between the chip mounting areas and a heat transfer wire provided between the heat dissipation conductors are further provided.

According to a second aspect of the present invention, the LED print head further includes a heat absorbing conductor formed in the surface area of the driver IC chip between the transistor forming area and the LED chip mounting area. Heat wire,
It is provided between the heat absorbing conductor and the heat radiating conductor. Claim 3 of the present invention
The LED print head according to claim 1, further comprising a housing on which the printed circuit board is mounted, and a housing protrusion integrally formed with the housing and in contact with the heat dissipation conductor. is there. Further, L according to claim 4 of the present invention.
The ED print head further includes a housing on which the back surface of the printed board is mounted, and a through hole formed in the printed board, wherein the heat dissipation conductor is provided on the back surface of the printed board via the through hole. It is characterized by being in contact with the housing.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a perspective view of an LED print head showing a first embodiment of the present invention. FIG. 2 is a top view of an exposure mechanism in a printer incorporating the LED print head according to the first embodiment of the present invention. 1 and 2 show an LED print head 2 according to a first embodiment of the present invention.
1 denotes an LED chip 1, a driver IC chip 2, a printed wiring board 3 (printed board), a first bonding wire 4, a second bonding wire 5, a third bonding wire 6 (heat transfer wire), The housing includes a heat dissipating conductor 7, a housing (not shown) on which the printed wiring board 3 is mounted, and a housing protrusion 8 integrally formed with the housing.

The LED chip 1 has a driver I surface.
It is fixed to the front surface of the C chip 2 and is disposed with the back surface facing upward. The LED chip 1 is a horizontally long chip, and light emitting portions (pn junctions) of a plurality of LEDs are arranged at equal intervals and in a row in one end surface (side surface) region 1a (see FIG. 1) on the long dimension side. It is a formed edge emitting type LED array. The light emitting section area 1a is a horizontally long area. The light emitting unit emits light in a direction substantially perpendicular to the end surface (side surface) where the light emitting unit region 1a is formed. Also, on the surface of the LED chip 1, individual electrode pads that are individually connected to the light emitting units are formed. Further, on the back surface of the LED chip 1, a common electrode common to all the light emitting units in the chip is formed.

The back surface of the driver IC chip 2 is fixed to the surface of the printed wiring board 3. This driver I
The C chip 2 is an IC for individually supplying a drive current to a plurality of LEDs of the LED chip 1. In the surface area 2a of the driver IC chip 2, the same number of final-stage transistors as the plurality of LEDs are formed for individually driving the plurality of LEDs (for individually turning on / off the drive current). I have. The transistor region 2a has a horizontally long L
A horizontally long area along the ED chip mounting area 2b,
This is a region where the surface region 2c is separated from the ED chip mounting region 2b. In the LED chip mounting area 2b, a plurality of driver electrode pads (not shown) that are individually connected to the last-stage transistors are formed. In addition, a surface region opposite to the region 2c with respect to the transistor region 2a includes:
A signal supplied from the printed wiring board 3 is input;
A plurality of signal input pads (not shown) are formed.

In the LED module in which the surface of the LED chip 1 is fixed to the surface of the driver IC 2, an anisotropic conductive adhesive is applied to the surface of the LED chip 1 or the surface of the driver IC 2, and the corresponding individual electrode pad and the driver electrode pad overlap. Thus, the LED array 1 and the driver IC 2 are thermocompression-bonded to each other. This allows
The corresponding individual electrode pads and driver electrode pads are electrically connected via an anisotropic conductive adhesive. The above-described anisotropic conductive adhesive is obtained by mixing a metal plating resin ball into an epoxy resin in an appropriate amount. This anisotropic conductive adhesive acts as a conductor only in the thickness direction (the direction perpendicular to the surface of the LED chip 1 and the surface of the driver IC 2) and acts as an insulator in the horizontal and vertical directions.

The printed circuit board 3 is a two-layer printed circuit board (a printed circuit board having two conductive layers) in which conductor layers are provided on both surfaces of a resin substrate, and a conductor wiring pattern is formed on the front and back surfaces by these conductor layers. It is. As the above resin, for example, a glass epoxy resin is used. This printed wiring board 3 is a horizontally long board. On the surface of the printed wiring board 3 (on the printed wiring board 3), a plurality of LED modules in which the LED chip 1 and the driver IC 2 are integrated are die-bonded in a horizontal row. Multiple LEs
The D module is die-bonded by fixing the back surface of the driver IC 2 to the surface of the printed wiring board 3 with an insulating adhesive such as a Si resin adhesive. In addition, the plurality of LED modules are die-bonded such that the light emitting area 1a of each LED chip 1 is aligned in a straight line along one edge on the long dimension side of the printed wiring board 3.

On the printed wiring board 3, a heat radiation conductor 7, a signal supply pad (not shown) for connecting to a signal input pad of the driver IC 2, and a ground (not shown) for connecting to a common electrode of the LED chip 1. And a connector terminal (not shown) to which a signal is supplied from the outside.

The first bonding wire 4 is connected to the driver I
The pad is provided between the signal input pad on the surface of C2 (on the driver IC 2) and the signal supply pad on the printed wiring board 3, and these pads are electrically connected. The number of the first bonding wires 4 is equal to the number of signal input pads of the driver IC 2 in each module. The second bonding wire 5 is an LED
It is provided between a common electrode on the back surface of the chip 1 and a ground pad on the printed wiring board 3, and electrically connects the common electrode and the ground pad. Three second bonding wires 5 are provided for each module.

Third bonding wire 6 (heat transfer wire)
Indicates the region 2c (the transistor region 2) on the driver IC 2
a) and the heat dissipation conductor 7 on the printed wiring board 3, and physically connects the area 2 c and the heat dissipation conductor 7. This third
The bonding wire 6 is not electrically connected to any electrode (signal line) on the driver IC 2. As the third bonding wire 6, for example, a slightly thicker gold wire is used. Two third bonding wires 6 are provided for each module.

The heat radiating conductor 7 is provided on the printed wiring board 3.
Formed horizontally from end to end along the module row,
It is a conductor with high thermal conductivity. The heat dissipation conductor 7 is connected to the region 2c of the driver IC 2 via the third bonding wire 6.
Physically connected to Further, the heat dissipation conductor 7 is not electrically connected to any signal line on the printed wiring board 3. Further, both ends of the heat dissipation conductor 7 are in direct contact with a housing projection 8 integrally formed with a housing (not shown) (see FIG. 2). The above-mentioned case is a metal body that protects the printed wiring board 3 and serves as a heat sink, and includes a lower case and an upper case. The housing projection 8 is formed integrally with the upper housing, the printed wiring board 3 is mounted on the lower housing, and the back surface of the printed wiring board 3 is in contact with the lower housing. Upper case is printed circuit board 3
Cover the sky above the surface. The printed wiring board 3 has its edge sandwiched between an upper housing and a lower housing, and is fixed to the housing.

Next, the operation of the LED print head 21 will be described with reference to FIGS. In FIG. 2, light emitted from the light emitting portion formed in the light emitting portion region 1a (see FIG. 1) of the LED chip 1 of the LED print head 21 enters the converging rod lens array 9.
The converging rod lens array 9 converges incident light from the LED print head 21 and irradiates the surface of the photosensitive drum 10.

Each LED of the LED chip 1 has a driver I
Current is supplied from the last stage transistor formed in the transistor region 2a (see FIG. 1) on C2 to emit light, and light is emitted from the light emitting unit. At this time, heat is generated. The locations where heat is generated are mainly two places: the light emitting portion region 1a of the LED chip 1 and the transistor region 2a of the driver IC 2. Most of the heat generated in the light emitting section region 1a is transmitted to the driver IC 2 via the anisotropic conductive adhesive. The above-mentioned heat conducted to the driver IC 2 is conducted substantially in the thickness direction in the driver IC 2 toward the printed wiring board 3. Further, the heat generated in the transistor region 2 a is also substantially conducted in the driver IC 2 toward the printed wiring board 3 in the thickness direction. Heat is generated in two places, the light emitting section area 1a of the LED chip 1 and the transistor area 2a of the driver IC 2, and the heat generated in the light emitting section area 1a of the LED chip 1 is transferred to the LED chip mounting area 2b on the driver IC 2.
Violent heat flow occurs in a region 2c between the LED chip mounting region 2b and the transistor region 2a on the driver IC 2, and the heat flow most easily concentrates in this region 2c.

The third bonding wire 6 is connected to the driver I
The area 2c where the heat flow is most likely to be concentrated on C2 and the heat dissipation conductor 7 on the printed wiring board 3 are directly connected. Further, since no electric signal is supplied to the heat dissipation conductor 7,
The heat dissipation conductor 7 itself does not generate heat. That is, L
The ED print head 21 has an original heat conduction path between the region 2 c on the driver IC 2 where heat flow is most likely to concentrate and the printed wiring board 3, via the inside and the back surface of the driver IC 2 and on the printed wiring board 3. In parallel with the area 2c on the driver IC 2 -the third bonding wire 6-
Another heat conduction path called a heat dissipation conductor 7 on the printed wiring board 3 is provided. Since the heat resistance of the heat conduction path formed by the third bonding wire 6 and the heat radiation conductor 7 is small, the heat conduction of the heat conduction path formed by the third bonding wire 6 and the heat radiation conductor 7 is higher than the original heat conduction path. Therefore, the heat generated in the light emitting portion region 1a of the LED chip 1 and the transistor region 2a of the driver IC 2 is
Printed wiring board 3 via third bonding wire 6
The heat is quickly conducted to the upper heat dissipation conductor 7.

Both ends of the heat radiating conductor 7 are in contact with a housing projection 8 which is a part of the housing which also functions as a heat sink. That is, the LED print head 21 is provided with a new heat dissipation path of the heat dissipation conductor 7-the housing projection 8-the housing. Since the thermal resistance of the heat dissipation conductor 7 and the housing projection 8 (casing) is small, the heat dissipation conductor 7 and the housing projection 8
The heat dissipation of the heat dissipation path by the (housing) is high and exerts its power in heat dissipation. Therefore, the heat flow that has flowed into the heat dissipation conductor 7 is quickly conducted to the housing projection 8 and quickly radiated into the outside air via the housing.

As described above, according to the first embodiment, the heat dissipation conductor 7 is provided on the printed wiring board 3 and the driver IC is provided.
2 and the LED chip mounting area 2
b is connected to the heat radiating conductor 7 by the third bonding wire 6, and both ends of the heat radiating conductor 7 are connected to the housing protrusions 8.
With such a structure, the heat dissipation can be improved, and the temperature rise of the LED module can be suppressed even if the power consumption of the LED module increases. As a result, the speed of the printer can be increased. Further, since an inexpensive glass epoxy resin substrate can be used for the printed wiring board 3, the cost can be reduced.

Second Embodiment FIG. 3 is a top view of an exposure mechanism in a printer incorporating an LED print head according to a second embodiment of the present invention. In FIG. 3, the same components as those in FIG. 1 or 2 are denoted by the same reference numerals. The LED print head 22 according to the second embodiment of the present invention includes an LED chip 1, a driver IC chip 2, a printed wiring board 3 (printed board), a first bonding wire 4, and a second bonding wire 5. , A third bonding wire 6 (heat transfer wire), a heat dissipation conductor 7, a housing (not shown) on which the back surface of the printed wiring board 3 is mounted, and a through hole 11 formed in the printed wiring board 3. ing.

An LED print head 22 according to a second embodiment of the present invention is different from the LED print head 21 shown in FIGS. 1 and 2 in that a through hole 11 is provided in a region of the printed wiring board 3 where the heat radiation conductor 7 is formed. The heat dissipating conductor 7 is brought into contact with the housing on the back surface of the printed wiring board 3 through the through hole 11, and the heat conducted to the heat dissipating conductor 7 on the printed wiring board 3 is transferred to the housing via the heat dissipating conductor 7 in the through hole 11. Is to be conducted. Since the printed wiring board 3 uses a glass epoxy resin substrate, the thermal conductivity between the front surface and the back surface is not good. However, when the through holes 11 are provided so that the heat dissipation conductor 7 reaches the back surface, the thermal conductivity between the front surface and the back surface is significantly improved. Note that the heat dissipation conductor 7 of the LED print head 22 is
It may not be in contact with the housing projection 8 (the housing projection 8
May be omitted).

Next, the operation of the LED print head 22 will be described with reference to FIG. As in the first embodiment, the heat generated in the light emitting portion region 1a of the LED chip 1 (see FIG. 1) and the transistor region 2a of the driver IC 2 (see FIG. 1) is combined with the transistor region 2a of the driver IC 2 and the LED. The heat is conducted to the heat dissipation conductor 7 through the region 2 c between the chip mounting regions 2 b and the third bonding wire 6.

The heat radiating conductor 7 extends from the front surface of the printed wiring board 3 to the back surface through the through hole 11, and is in direct contact with the metal housing which also functions as a heat sink on the back surface of the printed wiring board 3. That is, the LED print head 22 is provided with the heat radiating conductor 7-on the printed wiring board 3.
A new heat radiating path is provided between the heat radiating conductor 7 and the housing in the through hole 11. Since the thermal resistance of the heat radiation conductor 7 and the housing is small, the heat radiation conductor 7 and the through hole 1
The heat dissipation of the heat dissipation path by 1 is high and exerts its power in heat dissipation. Therefore, the heat flow flowing into the heat dissipation conductor 7 is quickly conducted to the housing and radiated into the outside air.

As described above, according to the second embodiment, the heat dissipation conductor 7 is provided on the printed wiring board 3 and the driver IC is provided.
2 and the LED chip mounting area 2
b is connected to the heat radiating conductor 7 by the third bonding wire 6, and the printed wiring board 3 is provided with a through hole 11 for penetrating the heat radiating conductor 7. By contacting the LED, the heat dissipation can be improved and the LED
Even if the power consumption of the module increases, the temperature rise of the LED module can be suppressed. As a result, the speed of the printer can be increased. The printed wiring board 3
Since an inexpensive glass epoxy resin substrate can be used, the cost can be reduced.

Third Embodiment FIG. 4 is a perspective view of an LED print head according to a third embodiment of the present invention. FIG. 5 is a top view of an exposure mechanism in a printer incorporating the LED print head according to the third embodiment of the present invention. 4 and 5, the same components as those in FIG. 1 or 2 are denoted by the same reference numerals. The LED print head 23 according to the third embodiment of the present invention shown in FIGS.
Driver IC chip 2, printed wiring board 3 (printed board), first bonding wire 4, second bonding wire 5, third bonding wire 6 (heat transfer wire), heat dissipation conductor 7, and printing A housing (not shown) on which the wiring board 3 is mounted, a housing protrusion 8 integrally formed with the housing, and the heat absorbing conductor 1 formed on the driver IC 2
2 is provided.

The LED print head 23 according to the third embodiment of the present invention is different from the LED print head 21 shown in FIGS.
A heat absorbing conductor 12 is formed in an area 2c between the LED chip mounting area 2a and the LED chip mounting area 2b, and the heat absorbing conductor 12 and the heat radiation conductor 7 on the printed wiring board 3 are physically connected by a third bonding wire 6. is there. The heat-absorbing conductor 12 is a conductor having a high heat-absorbing property formed in the horizontally long region 2c on the driver IC 2. This heat absorbing conductor 12 is not electrically connected to any electrode (signal line) on the driver IC 2. The heat absorbing conductor 12 is physically connected to the heat radiating conductor 7 on the printed wiring board 3 via the third bonding wire 6. Both ends of the heat dissipation conductor 7 are in direct contact with the housing projection 8 (see FIG. 5).

Next, the operation of the LED print head 23 will be described with reference to FIGS. Driver IC
Since no electric signal is supplied to the heat absorbing conductor 12 formed in the region 2c where the heat flow is most likely to be concentrated on the printed wiring board 2 and the heat radiating conductor 7 on the printed wiring board 3, the heat absorbing conductor 12 itself and the heat radiating conductor 7 themselves are not provided. No fever. The third bonding wire 6 is connected to a driver IC.
2 and the heat radiation conductor 7 on the printed wiring board 3 are directly connected. That is, the LED print head 2
3, a driver IC is provided between the region 2 c on the driver IC 2 where heat flow is most likely to concentrate and the printed circuit board 3.
2 in parallel with the original heat conduction path to the printed wiring board 3 through the inside and the back surface,
Another heat conduction path is provided, that is, the heat absorbing conductor 12 on the c-region 2 c, the third bonding wire 6, and the heat dissipating conductor 7 on the printed wiring board 3. Since the heat resistance of the heat conduction path formed by the heat absorbing conductor 12, the third bonding wire 6, and the heat radiation conductor 7 is small, the heat conduction of the heat conduction path is higher than the original heat conduction path. Therefore, heat generated in the light emitting portion area 1a of the LED chip 1 and the transistor area 2a of the driver IC 2 is quickly transmitted to the heat radiation conductor 7 on the printed wiring board 3 via the heat absorbing conductor 12 on the driver IC 2 and the third bonding wire 6. To conduct. By providing the heat absorbing conductor 12, the heat generated in the LED chip 1 and the driver IC 2 is conducted to the heat radiating conductor 7 more quickly than in the first embodiment.

Since both ends of the heat dissipation conductor 7 are in contact with the housing projection 8 which is a part of the housing, the heat dissipation conductor 7 is provided on the LED print head 23 in the same manner as in the first embodiment.
A new heat-dissipating path, namely, a housing projection 8-a housing is provided. Therefore, the heat flow that has flowed into the heat dissipation conductor 7 is
It is quickly transmitted to the housing projection 8 and quickly radiated into the outside air via the housing.

As described above, according to the third embodiment, the heat radiating conductor 7 is provided on the printed wiring board 3 and the heat absorption is made in the area 2c between the transistor area 2a and the LED chip mounting area 2b on the driver IC 2. By providing the conductor 12, connecting the heat-absorbing conductor 12 to the heat-radiating conductor 7 by the third bonding wire 6, and having both ends of the heat-radiating conductor 7 in contact with the housing projection 8, heat radiation can be improved. Even if the power consumption of the LED module increases, the LED
The temperature rise of the module can be suppressed. As a result, the speed of the printer can be increased. Further, since an inexpensive glass epoxy resin substrate can be used for the printed wiring board 3, the cost can be reduced.

Fourth Embodiment FIG. 6 is a top view of an exposure mechanism in a printer incorporating an LED print head according to a fourth embodiment of the present invention. In FIG. 6, the same components as those in FIG. 3, FIG. 4, or FIG. 5 are denoted by the same reference numerals. The LED print head 24 according to the fourth embodiment of the present invention includes the LED chip 1
Driver IC chip 2, printed wiring board 3 (printed board), first bonding wire 4, second bonding wire 5, third bonding wire 6 (heat transfer wire), heat dissipation conductor 7, and printing A housing (not shown) on which the back surface of the wiring board 3 is mounted, a through hole 11 formed in the printed wiring board 3, and a driver IC 2
And a heat absorbing conductor 12 formed thereon.

The LED print head 24 according to the fourth embodiment of the present invention differs from the LED print head 22 shown in FIG.
A heat absorbing conductor 12 is formed in an area 2c between the chip mounting areas 2b, and the heat absorbing conductor 12 and the heat radiating conductor 7 on the printed wiring board 3 are physically connected by third bonding wires 6. In other words, L in FIGS. 4 and 5
In the ED print head 23, the printed wiring board 3
A through hole 11 is provided in a region where the heat radiating conductor 7 is formed, and the heat radiating conductor 7 is brought into contact with the housing on the back surface of the printed wiring board 3 through the through hole 11, and
The heat conducted to the upper heat dissipation conductor 7 is conducted to the housing via the heat dissipation conductor 7 in the through hole 11. Since the printed wiring board 3 uses a glass epoxy resin substrate, the thermal conductivity between the front surface and the back surface is not good. However, when the through holes 11 are provided so that the heat dissipation conductor 7 reaches the back surface, the thermal conductivity between the front surface and the back surface is significantly improved. The heat dissipation conductor 7 of the LED print head 24 may not be in contact with the housing projection 8 (the housing projection 8 may not be provided).

Next, the operation of the LED print head 24 will be described with reference to FIG. LED print head 2
4 has a driver IC similar to the third embodiment.
2 between the region 2c where heat flow is most likely to concentrate and the printed circuit board 3 in parallel with the original heat conduction path to the printed circuit board 3 through the inside and the back surface of the driver IC 2 Another heat conduction path is provided, that is, the region 2c-the heat absorbing conductor 12 on the region 2c-the third bonding wire 6-the heat dissipating conductor 7 on the printed wiring board 3. Therefore, heat generated in the light emitting portion area 1a of the LED chip 1 and the transistor area 2a of the driver IC 2 is quickly transmitted to the heat radiation conductor 7 on the printed wiring board 3 via the heat absorbing conductor 12 on the driver IC 2 and the third bonding wire 6. To conduct.

Further, in the LED print head 24, similarly to the second embodiment, a new heat radiating path of the heat radiating conductor 7 on the printed wiring board 3, the heat radiating conductor 7 in the through hole 11, and the housing is provided. Is provided. Therefore, the heat flow flowing into the heat dissipation conductor 7 is quickly conducted to the housing,
Radiated into the open air.

As described above, according to the fourth embodiment, the heat dissipating conductor 7 is provided on the printed wiring board 3 and the heat absorption occurs in the area 2c between the transistor area 2a and the LED chip mounting area 2b on the driver IC 2. The conductor 12 is provided, the heat absorbing conductor 12 is connected to the heat radiating conductor 7 by the third bonding wire 6, and the printed wiring board 3 is provided with a through hole 11 for penetrating the heat radiating conductor 7. In this structure, heat dissipation can be improved, and even if power consumption of the LED module increases, temperature rise of the LED module can be suppressed. As a result, the speed of the printer can be increased. Also, since an inexpensive glass epoxy resin substrate can be used for the printed wiring board 3,
Cost reduction can be achieved.

In the first to fourth embodiments,
Although glass epoxy resin is used for the printed wiring board, another resin such as phenol resin or polyimide resin may be used. Further, the printed wiring boards in the second and fourth embodiments may be any as long as they can form through holes. In addition, the number of layers of the printed wiring board is 2
Although the number of layers is limited, the present invention does not limit the number of layers of the printed wiring board, and the number of layers may be three or more when another electrode cannot be routed to form a heat dissipation conductor.

In the first to fourth embodiments,
An edge emitting type LED chip was used, but a top emitting type LED chip was used.
An ED chip may be used. The present invention does not limit the light emission form of the LED chip, and the LED chip may be any one that constitutes an LED module together with the driver IC.

Further, both ends of the heat radiation conductor 7 are provided with the housing projections 8.
And the heat dissipation conductor 7 may be in contact with the housing on the back surface of the printed wiring board 3 through the through hole 11.

[0039]

As described above, according to the present invention, a heat dissipation conductor is provided on the surface of a printed circuit board, and the surface of the driver IC chip surface between the transistor forming area and the LED chip mounting area is formed by the heat dissipation wire. Is connected, the heat radiation can be improved, and even if the power consumption of the LED module increases, the rise in the temperature of the LED module can be suppressed. Therefore, there is an effect that the speed of the printer can be increased. In addition, since an inexpensive substrate such as a resin substrate can be used as the printed circuit board, the cost can be reduced.

Further, the heat radiation conductor is brought into contact with the housing projection, or a through hole is provided in the printed board, and the heat radiation conductor is brought into contact with the housing on the back surface of the printed board.
Alternatively, a heat-absorbing conductor is provided in the surface area of the driver IC chip between the transistor forming area and the LED chip mounting area, and this heat-absorbing conductor is connected to a heat-radiating conductor by a heat-transfer wire, thereby further improving heat radiation. This has the effect.

[Brief description of the drawings]

FIG. 1 is a perspective view of an LED print head according to a first embodiment of the present invention.

FIG. 2 is a top view of an exposure mechanism in the printer incorporating the LED print head according to the first embodiment of the present invention.

FIG. 3 is a top view of an exposure mechanism in a printer incorporating an LED print head according to a second embodiment of the present invention.

FIG. 4 is a perspective view of an LED print head showing a third embodiment of the present invention.

FIG. 5 is a top view of an exposure mechanism in a printer incorporating an LED print head according to a third embodiment of the present invention.

FIG. 6 is a top view of an exposure mechanism in a printer incorporating an LED print head according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 LED chip, 2 Driver IC chip, 2a
Transistor area, 2b LED chip mounting area,
2c area between 2a and 2b, 3 printed wiring board (printed board), 6 third bonding wire (heat transfer wire), 7 heat dissipation conductor, 8 housing projection, 11
Through hole, 12 heat absorbing conductor.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masumi Koizumi 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (4)

[Claims] 1. An LED print comprising: a printed circuit board; a driver IC chip having a back surface fixed to the surface of the printed circuit board and a transistor for driving an LED formed on the surface; and an LED chip fixed to the surface of the driver IC chip. The head further comprises: a heat dissipation conductor formed on a printed circuit board surface; a driver IC chip surface area between the transistor formation area and the LED chip mounting area; and a heat transfer wire provided between the heat dissipation conductor. An LED print head comprising: 2. The semiconductor device according to claim 1, further comprising: a heat absorbing conductor formed in a surface area of the driver IC chip between the transistor forming area and the LED chip mounting area, wherein the heat transfer wire is provided between the heat absorbing conductor and the heat radiating conductor. The L according to claim 1, wherein the L is provided.
ED print head. 3. The apparatus according to claim 1, further comprising: a housing on which the printed circuit board is mounted; and a housing protrusion integrally formed with the housing and in contact with the heat dissipation conductor.
Or the LED print head according to 2. 4. A printed circuit board further comprising: a housing on which the back surface of the printed circuit board is mounted; and a through hole formed in the printed circuit board, wherein the heat dissipation conductor is provided on the back surface of the printed circuit board via the through hole. The LED print head according to claim 1, wherein the LED print head is in contact with the housing.