JP3882266B2 - Semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device in which semiconductor elements each having a different calorific value are arranged on the same support substrate, and more particularly to a semiconductor device using various light source support substrates in which light-emitting elements are mounted with high density. .
[0002]
[Prior art]
Today, various types of information terminal devices are becoming popular with the progress of office automation. Among them, information terminal devices using light emitting elements occupy an important position as optical printers. In particular, full-colorization has become possible with the development of semiconductor light-emitting elements capable of emitting ultra-high luminance in which RGB (red, green, and blue) each have a brightness of 1000 mcd or more. Such a printer has no noise and has a high printing speed. It has been attracting attention as a printer head for an optical printer that is used in the A device. Those using LED chips as light emitting elements in optical printer heads
1. Since the response speed is nanoseconds and parallelization is possible, high-speed driving is possible. 2. Since light emission can be controlled simply by inputting and outputting electrical signals, it can be driven at a wide range of speeds. 3. There is no start-up time for driving and no waiting time. 4). Compact and simple structure, excellent in downsizing, adjustment and maintenance. 5). Since it is a solid system and has no moving parts, it has excellent characteristics such as no noise and high reliability.
[0003]
When a light source unit using such a semiconductor light emitting element is driven, the light emitting element generates heat as it is driven. When the temperature of the light emitting element itself rises, the semiconductor characteristics change. Further, the temperature rise of the light emitting element may lead to malfunction of the light emitting element or destruction of the semiconductor element itself. Specifically, the light emission wavelength emitted from the light emitting element is shifted due to the influence of heat from the outside or the heat generated by driving the light emitting element itself. The light emission luminance of the light emitting element is decreased, or the luminance of the light emitting element is increased to the contrary. That is, there are changes in various characteristics of the semiconductor depending on the temperature. This is a problem in scanners and optical printer devices that perform sensing using their respective electrical / optical characteristics.
[0004]
Therefore, such a heat problem can be solved to some extent by arranging the light emitting elements on a metal plate or the like in consideration of heat dissipation as shown in FIG. In FIG. 5, an aluminum support substrate 503 with good heat dissipation is used as a support on which the LED chips 504 and 505 are arranged. An insulator layer 514 is formed of a heat-resistant epoxy resin on the aluminum support substrate 503 so that the LED chips are not electrically short-circuited. The insulator layer also acts as an adhesive. A copper foil 512 having a desired shape is formed on the insulator layer 514 so that each LED chip can be driven, thereby forming a conductive pattern. The LED chips 504 and 505 arranged close to each other are wire-bonded with a conductive pattern 512 and a gold wire 506. Heat generated by driving the LED chip is conducted to the aluminum support substrate 503 through the insulator layer 514. When the aluminum support substrate 503 dissipates heat, a semiconductor device in consideration of heat dissipation can be obtained.
[0005]
[Problems to be solved by the invention]
However, in the present day when stable semiconductor characteristics are required even in more severe environments such as higher driving speed, higher brightness of light emitting elements, and long-time use, the above configuration is not sufficient. When semiconductor elements made of different materials are used for the formed semiconductor, the drive characteristics tend to vary significantly. Also, those that require different semiconductor elements such as optical printer heads to be installed close to each other tend to cause significant fluctuations. A semiconductor with a large fluctuation range due to heat conduction from a semiconductor with a large calorific value, especially when a semiconductor with a large calorific value and a semiconductor with a large calorific value are mounted on the same base material and close to each other on the same layer. The electrical / optical properties of are significantly affected. In scanners and optical printer devices that sense using the respective electrical / optical characteristics, a slight change in characteristics will have a fatal adverse effect. Specifically, a desired color cannot be detected. There is a problem that the balance is lost as the temperature rises.
[0006]
[Means for Solving the Problems]
The semiconductor device of the present invention includes a conductive pattern disposed on a support substrate via an insulator layer, and two or more semiconductor elements electrically connected to the conductive pattern independently of each other. Two or more semiconductor elements have different calorific values at least during operation. That is, the two or more semiconductor elements are at least a first semiconductor element that generates a large amount of heat and a second semiconductor element that generates a small amount of heat. The first semiconductor element has a heat conduction path having better heat conduction with the support substrate through the conductive pattern than the second semiconductor element.
[0007]
According to another aspect of the semiconductor device of the present invention, each of the first and second semiconductor elements is a light emitting element.
[0008]
The semiconductor device according to claim 3, wherein the first semiconductor element is a nitride compound semiconductor, and the second semiconductor element is made of gallium phosphorus, gallium arsenide phosphorus, gallium aluminum arsenide, or indium gallium aluminum phosphorus. One type to be selected.
[0009]
The semiconductor device according to claim 4 uses a flexible substrate as the conductive pattern formed through the insulator layer.
[0010]
[Action]
In the present invention, a plurality of semiconductor elements having different temperature characteristics are arranged on a support substrate that functions as a heat dissipation portion. Further, a heat conduction path is formed between the semiconductor element that generates a large amount of heat and the support substrate. As a result, the heat conduction to the semiconductor light emitting device which is arranged close to the semiconductor element having a large heat generation amount and which has a small heat generation amount is extremely reduced. Each semiconductor element can dissipate heat to the heat dissipating part. Thermal separation can be performed so that the drive characteristics of semiconductor elements having different calorific values do not fluctuate. That is, a semiconductor device having stable characteristics can be obtained by arranging semiconductor elements close to each other on the same supporting substrate while being thermally independent.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
As a result of various experiments, the present inventor has found that a semiconductor device having stable characteristics can be obtained by thermally separating different semiconductor elements while enabling heat dissipation.
[0012]
That is, by providing a path with good thermal conductivity (good heat conduction path) on the side of the semiconductor element having a large amount of heat generation, the thermal influence on the side of the semiconductor element having a small amount of heat generation can be extremely reduced. For this reason, the heat from the semiconductor element having a large calorific value hardly causes an adverse effect on the adjacent semiconductor elements having a small calorific value. In addition, a semiconductor element having a small calorific value can be radiated while preventing thermal influence from others. Hereinafter, a specific configuration of the present invention will be described in detail.
[0013]
FIG. 2 is a schematic cross-sectional view of the semiconductor device of the present invention. In FIG. 2, an aluminum alloy having excellent heat dissipation is used as the support substrate 203. On the support substrate 203, a conductive pattern 212 formed of copper foil is provided so that each light emitting element can be driven. The conductive pattern 212 constitutes a flexible substrate that is pressure-bonded to both surfaces of the polyimide resin 211 and sealed with an epoxy resin 214. The flexible substrate is bonded to the metal support substrate 203 with an epoxy resin 215. An opening is partially provided on the surface of the flexible substrate. Using this opening, the electrodes of the LED chips 204 and 205 arranged on the flexible substrate and the copper foil as the conductive pattern 212 are electrically connected using a gold wire 206 or an Ag-containing epoxy resin. It is. As a semiconductor element, a LED chip 204 of a gallium nitride compound semiconductor capable of emitting blue or green light and an LED chip 205 using an indium / aluminum / gallium phosphorous semiconductor capable of emitting red light are close to each other. Provided. The LED chip 204 of a gallium nitride compound semiconductor with a large calorific value is fixed using a conductive paste containing Ag on a copper foil of a flexible substrate. This serves as part of the heat conduction path. Note that the LED chip 204 using a gallium nitride compound semiconductor has a semiconductor layer formed on sapphire and is electrically insulated from the copper foil. In addition, the copper foil serving as the conductive pattern on which the LED chip 204 is disposed is in contact with the aluminum support substrate 203 using a conductive paste containing Ag to form a heat conduction path 213. On the other hand, the LED chip 205 that generates a small amount of heat is electrically connected to the copper foil using a conductive paste, which is an epoxy resin containing Ag, and is fixed to the fixing system.
[0014]
The difference between the copper foils on which the LED chips are arranged is that only the copper foil on which the LED chips 205 are arranged is covered with the heat-resistant epoxy resin that constitutes the flexible substrate, and has no opening on the metal support substrate 203 side. That is. For this reason, the LED chip 204 is formed with a path (thermal conduction path) 213 having good thermal conductivity in the aluminum substrate using Ag paste and copper foil. On the other hand, the LED chip 205 having a smaller heat generation amount is released to the metal support substrate through an epoxy resin and an adhesive that serve as an insulator layer. The heat from the LED chip 204 is radiated to the aluminum support substrate 203 through the heat conduction path 213 having better thermal conductivity than the direction toward the LED chip 205 by the coated resin. Therefore, the heat released from the LED chip 204 with a large amount of heat generation is conducted to the aluminum support substrate 203 rather than to the LED chip 205 that is adjacent thereto. The semiconductor characteristics of the LED chip 205 are very unlikely to change due to heat from the LED chip 204 that generates a large amount of heat. In addition, each LED chip 204, 205 itself can efficiently release heat to the outside through the aluminum support substrate 203, so that a semiconductor device with extremely small fluctuation in semiconductor characteristics can be obtained.
[0015]
(Heat conduction passage 213)
The heat conduction passage 213 is a passage that efficiently conducts heat from the semiconductor element to the heat radiating portion. Therefore, examples of the heat conduction path 213 used in the present invention include resins containing various metal powders, bolts with excellent heat conduction, those in which the metal 313 is inserted into via holes as shown in FIG. 3, solder, and the like. . Al, Cu, and phosphor bronze are preferable as members having good thermal conductivity used in the heat conduction path. In addition, a part of the electric circuit can be configured using the heat conduction path. Furthermore, resin paste containing Ag, Au, Cu, and alloys thereof is preferable as a resin containing various metal powders and the like for ease of formation. As the base of the resin paste, an acrylic resin, an epoxy resin, a silicone resin, or the like is preferably used. The via hole is a hole for interlayer connection, and metal plating or the like may be formed inside.
[0016]
(Supporting substrate 203)
The support substrate 203 can efficiently conduct or release the driving heat from the semiconductor element to the outside. Moreover, what can fix the mounting state of a semiconductor element is preferable. Specific examples of the material for the support substrate include metals such as aluminum and copper, alloys thereof, stainless steel, and ceramics. Further, it is also possible to use a heat conducting element in which the inside of a metal tube made of copper having a capillary structure on the inner wall as a composite material is evacuated and water or a hydraulic fluid such as alternative chlorofluorocarbon is sealed. As a result, the heat accompanying the driving of the semiconductor element can be efficiently released, and the temperature rise of the semiconductor element can be prevented. It is also possible to configure an electric circuit by using a support substrate, a conductive pattern, and a heat conduction path.
[0017]
(Conductive pattern 212)
The conductive pattern 212 can supply power to each semiconductor element. A desired pattern is formed to supply power to each semiconductor as desired. In particular, in the present invention, the conductive pattern functions not only as an electrical path of the semiconductor element but also as a thermal path. Therefore, as a member used for the conductive pattern used in the present invention, a member having good electrical conductivity and thermal conductivity is preferable. Preferred examples of materials that satisfy such characteristics include copper, phosphor bronze, aluminum, gold, silver, platinum, and alloys thereof.
[0018]
(Insulator layers 214 and 215)
The insulator layers 214 and 215 maintain the insulation between the support substrate 203 and each conductive pattern 212. It also acts as a thermal barrier between semiconductor elements. As a result, the semiconductor elements are thermally separated from each other. If such an insulator layer is made too thick, heat dissipation from each semiconductor element to the support substrate is hindered, and if it is made too thin, not only the heat conduction between the semiconductor elements is performed, but also the dielectric strength is lowered. Further, not only between the support substrate 203 and the conductive pattern 212 but also the entire conductive pattern 212 can be covered to protect the conductive pattern. Furthermore, a plurality of insulator layers can be stacked. What coated such a conductive pattern 212 with the insulator layer can be utilized as a flexible substrate. When the light-emitting device is used for an optical printer head, it has a feature that even when the head portion is driven, conduction can be freely achieved by the flexible substrate. Moreover, the flexible substrate etc. which laminated | stacked the electroconductive pattern and the insulator layer can be arrange | positioned not only on one side of a support substrate but on both surfaces.
[0019]
Therefore, when the flexible substrate is bonded onto the metal support substrate, the cover film and the adhesive of the flexible substrate serve as an insulator layer. As a specific material for the insulator layer, a heat-resistant epoxy resin, a heat-resistant engineering plastic resin, a polyimide resin, or a laminate thereof is preferably used. When the semiconductor device is used in an optical printer head or the like, it is preferable that the insulator layer on the light emitting element side is colored in a dark color system in order to improve contrast.
[0020]
(Semiconductor elements 204 and 205)
Various semiconductor elements 204 and 205 are used as desired. In particular, the semiconductor elements used in the present invention include various semiconductor elements that differ in the amount of heat generated during operation (driving). Examples of semiconductor elements having different calorific values at the time of driving include those produced by using different configurations and different materials formed in accordance with a desired purpose. Specifically, a semiconductor light emitting layer such as ZnS, ZnSe, GaP, GaAs, InN, AlN, GaN, InGaP, InGaN, or InGaAlN is formed on a substrate by using a liquid phase growth method, MOCVD method, or the like as a semiconductor element. Suitable semiconductor elements are mentioned.
[0021]
Two or more different semiconductor elements can be arranged. When used as an optical printer head as a semiconductor light emitting element, a plurality of different semiconductor light emitting elements are arranged for higher definition and higher speed. As the number of semiconductor elements increases, the amount of heat generated increases, and the effects of the present invention become prominent.
[0022]
Semiconductor light-emitting elements usually have different materials and different configurations because the band gap differs depending on the emission wavelength. Therefore, the amount of heat generation and various characteristics differ depending on the semiconductor element. As a semiconductor element capable of emitting blue light as a semiconductor element that stably emits light with high brightness, a nitride-based semiconductor such as GaN or InGaN is preferably exemplified. As the semiconductor element capable of emitting green light, a nitride semiconductor such as GaN or InGaN is preferably used. Further, GaP, GaAsP, GaAlAs, InGaAlP, or the like is preferably used as a semiconductor element capable of emitting red light.
[0023]
Nitride-based compound semiconductors currently tend to emit light with ultra-high brightness, have a high driving voltage, and generate a large amount of heat as compared with GaP, GaAsP, GaAlAs, InGaAlP semiconductors, and the like. In addition, these semiconductor elements tend to have a large change in light emission luminance as the temperature rises. FIG. 4 shows the relative luminance in the temperature change of the LED chip using InGaN as a light emitting layer as a nitride compound semiconductor and the LED chip using a GaAsP semiconductor as a light emitting layer. It can be seen from FIG. 4 that the brightness of the LED chip using GaAsP greatly decreases as the temperature rises compared to the LED chip using InGaN. Note that InGaN is formed by changing the composition of In and using a semiconductor element capable of emitting green light with a large amount of In and a semiconductor element capable of emitting blue light with a relatively small amount of In. Hereinafter, although the Example of this invention is explained in full detail, it cannot be overemphasized that it is not limited only to this Example.
[0024]
【Example】
Example 1
An LED chip in which a nitride compound semiconductor is formed on a sapphire substrate was used as a semiconductor element having a large amount of heat generation. Specifically, an InGaN film formed by MOCVD on a sapphire substrate as a light emitting layer was used. By changing the composition, a B (blue) LED chip and a G (green) LED chip are respectively configured. Further, as an R (red) LED chip, an LED chip in which GaAlAs is formed on a GaAlAs substrate as a semiconductor element having a smaller amount of heat generation was used.
[0025]
As the support substrate on which the LED chip is arranged, an aluminum support substrate having a thickness of 1 mm and a square of 24 mm × 15 mm was used. A flexible substrate was used as a part of the insulator layer disposed on the aluminum support substrate and the conductive pattern.
[0026]
The flexible substrate is etched into a desired shape so that each LED chip can be driven after the copper foil is thermocompression bonded to the polyimide resin.
[0027]
The flexible substrate is sealed with a polyimide resin except for each LED chip installation location, an electrical connection location with the LED chip electrode, and the copper foil surface constituting the heat conduction path. In addition, the copper foil surface which comprises a heat conductive path is the copper foil surface by the side of the support substrate connected with the electroconductive pattern with which the LED chip which can light-emit green and blue using the gallium nitride compound semiconductor was loaded. is there.
[0028]
The copper foil of the flexible substrate and the aluminum support substrate were connected with a Cu paste using an epoxy resin so that the aluminum support substrate and the copper foil surface were easily conducted. The connection part is formed by removing a part of the aluminum support substrate and pouring and hardening a Cu paste. Further, the other flexible substrate surface and the aluminum support are bonded with an epoxy resin. By this connection, a heat conduction path is formed in a part of the copper foil pattern on which the LED chips capable of emitting BG are stacked and the aluminum support substrate. The RGB LED chips were bonded to the exposed surface of the copper foil with an Ag paste in the vicinity of a 520 μm pitch. The LED chip capable of emitting R is fixed on the exposed copper foil and electrically connected. The other electrode of the LED chip capable of emitting R is wire-bonded to a copper foil using a gold wire which is a conductive wire. Since the GB LED chip has a semiconductor layer formed on sapphire, each electrode of PN is formed on the same surface side. Each electrode of the LED chip capable of emitting GB and the exposed copper foil surface are wire-bonded with gold wires, respectively. In a semiconductor device on which each LED chip is mounted, a flexible substrate is extended from an aluminum support substrate, and a driving means for driving the LED chip is electrically connected. Thus, it can be used as an optical printer head capable of emitting desired light.
[0029]
The adjusted power was supplied to each LED chip of the semiconductor device so that white light of chromaticity point (X, Y) = (0.31, 0.31) could be emitted. Although it was continuously lit at room temperature for 100 hours, no color shift was confirmed. It was also found that there was almost no decrease in luminance, and that each semiconductor element was thermally separated and radiated heat.
[0030]
【effect】
With the semiconductor device according to the first aspect of the present invention, a semiconductor device capable of performing stable operation even when high energy is supplied for a long time can be provided.
[0031]
By using the semiconductor device according to the second aspect of the present invention, a semiconductor light emitting device with stable luminance and the like can be obtained.
[0032]
According to the semiconductor device of claim 3 of the present invention, a first semiconductor element that generates a large amount of heat and has a small characteristic change due to temperature, and a second semiconductor element that generates a small amount of heat and has a large characteristic change due to temperature, , Even when they are arranged close to each other, a light emitting device capable of emitting light with high brightness stably for a long time can be obtained.
[0033]
With the semiconductor device according to the fourth aspect of the present invention, it can be electrically connected to other circuits and can be moved. Therefore, it can be suitably used as an optical printer head.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an optical printer head using the present invention.
FIG. 2 is a schematic cross-sectional view showing the AA cross section of FIG. 1;
FIG. 3 is a schematic cross-sectional view showing another semiconductor device of the present invention.
FIG. 4 is a graph showing the temperature dependence of an indium gallium nitride semiconductor light emitting device and a gallium aluminum phosphorous semiconductor light emitting device.
FIG. 5 is a schematic cross-sectional view showing a semiconductor device shown for comparison with the present invention.
[Explanation of symbols]
101, 201... Opening 102... Insulator layer 103, 203 provided on the upper surface side. Metal support substrate 104, 204... ... Semiconductor light-emitting elements 106, 206 ... wire 211 ... polyimide resin 212 ... conductive pattern 213 ... Cu paste 214 serving as a heat conduction path ... insulator layer Skin 215 of flexible substrate ... Adhesive 313 as an insulator layer ... Cu plating 503 as a heat conduction path ... Aluminum support substrate 504, 505 ... LED chip 506 ... Gold wire 511 ...・ Heat-resistant epoxy resin 512 ... conductive pattern 514 ... epoxy resin

Claims (4)

A semiconductor device comprising: a conductive pattern disposed on a support substrate via an insulator layer; and two or more semiconductor elements electrically connected independently of the conductive pattern,
The semiconductor elements are at least a first semiconductor element having a large calorific value during operation and a second semiconductor element having a smaller calorific value than the first semiconductor element, and the first semiconductor element is conductive. A semiconductor device characterized by having a heat conduction path having better heat conduction with the support substrate than the second semiconductor element through the conductive pattern. The semiconductor device according to claim 1, wherein each of the first and second semiconductor elements is a light emitting element. The first semiconductor element is a nitride compound semiconductor, and the second semiconductor element is one selected from gallium phosphorus, gallium arsenide phosphorus, gallium aluminum arsenide, or indium gallium aluminum phosphorus. Item 14. A semiconductor device according to Item 1. The semiconductor device according to claim 1, wherein the conductive pattern formed through the insulator layer constitutes a flexible substrate.

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