JP5323371B2 - LED device manufacturing method - Google Patents

Description

  The present invention relates to an LED device on which an LED chip is surface-mounted.

  By developing LED chips that emit blue light or near ultraviolet light in the short wavelength range, LED devices that combine these LED chips with phosphors that absorb the light emission wavelength of LED chips and convert them into light in different wavelength ranges have been developed. Has been. Among them, a pseudo white LED device combining a blue LED chip and a YAG silver phosphor is widely used as an illumination light source or a liquid crystal display backlight source. Particularly, in general LED light sources for illumination, high brightness and long life are important problems.

  In general, as a substrate of an LED device on which an LED chip is surface-mounted, a molded body in which a lead frame material and a resin are integrally formed by injection molding, a flexible wiring substrate, a ceramic substrate having a wiring pattern, and the like are used. For LED chip mounting and wiring, wire bonding mounting or flip chip mounting is generally used depending on the chip type.

  FIG. 11 shows an example of a general LED device in which an LED chip is surface-mounted.

  Reference numeral 1 denotes an insulating substrate, which is made of a highly heat-resistant insulating resin or ceramic. 2 is an LED chip. The LED chip 2 is electrically joined to the LED chip mounting wiring part 3. Reference numeral 4 denotes a wiring conductor portion. In FIG. 11, the LED chip 2 is mounted on the LED chip wiring mounting wiring portion 3 with a die bond paste or silver paste made of epoxy resin, silicone resin or the like, and also serves as a wiring conductor portion through a bonding wire 5 made of gold, aluminum or the like. It is electrically joined to the LED chip mounting wiring part 3. When a copper-clad flexible substrate is used as a base material having the LED chip mounting wiring part 3 and the wiring conductor part 4, the wiring conductor part 4 is formed by patterning copper by chemical etching or the like. However, since copper is easily oxidized, an overcoat layer is generally provided. In FIG. 11, the copper of the conductor wiring portion 4 on the surface on which the LED chip 2 is disposed is covered with an insulating resist 6, and the LED chip mounting wiring portion 3 is nickel-plated on the copper, and the reflectance of the copper is mounted thereon. High silver plating. The wiring conductor 4 that is not covered with the insulating resist 6 except for the LED chip mounting wiring 3 is nickel-plated on copper and gold-plated or tin-plated on the copper for connection to an external electrode.

  12 is a diagram showing an example of a multi-chip substrate of the LED device shown in FIG. From the viewpoint of cost, a surface-mount type LED device generally uses a substrate as shown in FIG. 12, and a manufacturing method in which a large number of LED devices are manufactured on a single substrate and then cut into single pieces.

In the case of a white LED device that requires white light emission, it is particularly necessary to arrange a material that efficiently reflects light emitted from the LED chip around the LED chip.
Therefore, as shown in FIG. 11, the LED chip mounting wiring part surface on which the LED is mounted is often subjected to silver plating having a high reflectance so as to have both functions of the reflector and the wiring conductor part.

  However, silver is a thermally and chemically unstable substance, and its reflectance is reduced due to heat generation of LED chips or gas containing sulfur in the atmosphere, etc., so silver is used for LED chip mounting wiring parts. The LED device had problems with respect to stability of luminance and chromaticity and long life.

As one method of LED device structure with high brightness and long life, Patent Document 1 separates a light reflecting portion and a wiring conductor portion and provides a transparent inorganic oxide film layer on a reflecting plate by a vacuum thin film forming method. A wiring conductor portion is formed on the substrate.
Japanese Patent Laying-Open No. 2005-244152 (page 12, FIG. 3)

  However, in the case of the LED device as in the above-mentioned Patent Document 1, when all of the wiring conductor part, the inorganic oxide film layer, and the light reflecting part are formed by the vacuum thin film forming method, from the difference of each pattern and the difference of the target, It is difficult to form all the parts in one process, and there is a problem that the process becomes complicated.

  In addition, when a vacuum thin film forming method using a mask is used, the normal mask accuracy is about 100 microns, so that an LED device in which films having different patterns as in the above-mentioned document 1 are stacked is a small LED device. It seems that the application of is difficult.

  Therefore, an object of the present invention is to provide a high-luminance and long-life LED device that can be reduced in size with fewer steps.

  The LED device of the present invention is an LED device in which an LED chip is mounted on a substrate having an LED chip mounting wiring portion and a wiring conductor portion, and the LED chip mounting wiring portion has a specific metal ultrathin film. It is a feature.

  The LED device manufacturing method of the present invention is a method of manufacturing an LED device in which an LED chip is mounted on a substrate having an LED chip mounting wiring portion and a wiring conductor portion, and is specific to at least the LED chip mounting wiring portion. The process of forming a metal ultrathin film, the process of mounting and wiring an LED chip on the LED chip mounting wiring part on which a specific metal ultrathin film is formed, and the LED chip mounting on which a specific metal ultrathin film is formed And a step of heat-treating the substrate on which the LED chip is mounted and wired in the wiring portion.

  Further, the LED device manufacturing method of the present invention is an LED device manufacturing method in which an LED chip is mounted on a substrate having an LED chip mounting wiring portion and a wiring conductor portion, and at least the LED chip mounting wiring portion The method includes a step of forming a specific metal ultrathin film, and a step of mounting and wiring the LED chip on the LED chip mounting wiring portion on which the specific metal ultrathin film is formed.

  Furthermore, in the LED device of the present invention, the metal ultrathin film is preferably a film composed of a metal selected from titanium or aluminum.

  In the LED device manufacturing method of the present invention, the thickness of the ultrathin metal film is preferably 10 to 100 mm.

(Function)
The LED device of the present invention has a great point that an ultra-thin film formed on the silver surface is conductive after film formation and before heat treatment, and becomes a transparent oxide film by relatively low temperature heat treatment. Become.

  Titanium and aluminum are known as easily oxidizable metals, but heat treatment at 500 ° C. or higher is usually required to oxidize the entire metal thin film, which is usually about 1000 mm thick or thicker. However, these ultra-thin metal films have a film thickness of about several tens of millimeters and are considered to behave differently from normal thin films.

  These specific ultrathin metal films of several tens of thousands are scattered in islands immediately after film formation and are not considered to be a film that covers the entire surface of the underlying silver surface. Since the reaction activity is high, it is considered that the resin material used in a normal LED device changes into a metal oxide film by heat treatment at a relatively low temperature that can be withstood.

  Furthermore, the LED device of the present invention has sulfuration resistance even when the ultrathin film formed on the silver surface is not subjected to heat treatment. Dozens of ultrathin metal ultrathin films are scattered in islands immediately after film formation and are not considered to be a film that covers the entire surface of the underlying silver surface. Since it is smaller than hydrogen sulfide molecules, which are reactive gases, it is considered to have antisulfurization characteristics.

  According to the present invention, it is possible to provide an LED device having high luminance and long life characteristics without greatly changing the manufacturing process of the conventional LED device.

  Furthermore, the LED device according to the present invention can use general materials and methods such as a base material to be used, an LED chip, a wiring material and a wiring system for electrically connecting the LED chip and the wiring conductor, and a wiring conductor. Therefore, it is possible to contribute to cost reduction and miniaturization of LED devices having high luminance and long life characteristics.

(First embodiment)
The LED device which is 1st embodiment of this invention is shown in FIG. 1, and the manufacturing method is demonstrated based on FIG.

  Reference numeral 1 denotes an insulating base material having an LED chip mounting wiring portion 3 and a wiring conductor portion 4. As the insulating substrate 1, a high heat-resistant glass epoxy resin, BT resin (bismaleimide triazine), PBT resin (polybutylene terephthalate), hard silicone resin, ceramics, or the like is used.

  2 is an LED chip. A typical LED chip is an InGaN-based LED chip, and emits near-ultraviolet light, blue light, and green light depending on the composition ratio.

  As a mounting method of the LED chip 2, when an n-type electrode pad and a p-type electrode pad are provided on the upper surface of the LED chip 2, a die bond made of epoxy resin, silicone resin or the like on the LED chip wiring mounting wiring portion 3 is used. The LED chip 2 is mounted using a paste or a silver paste, and then electrical bonding between both electrode pads and the LED chip mounting wiring section 3 is bonded and mounted with a bonding wire such as gold or aluminum. In the case of the LED chip 2 provided with an n-type electrode pad and a p-type electrode pad on the upper and lower surfaces, respectively, the upper electrode pad is mounted with a bonding wire, and the lower electrode pad is mounted with a conductive paste such as silver paste. The When the n-type electrode pad and the p-type electrode pad are arranged on the lower surface of the LED chip 2, the LED chip 2 is mounted by flip chip mounting or the like. In the first embodiment, an example in which both electrode pads are provided on the upper surface of the LED chip 2 is shown.

  When a copper-clad flexible substrate using epoxy resin or BT resin is used as the insulating substrate 1 having the LED chip mounting wiring portion 3 and the wiring conductor portion 4, the wiring conductor portion 4 is formed by patterning copper by chemical etching or the like. However, since copper is easily oxidized, an overcoat layer made of metal or resin is generally provided. Most of the insulating resist 6 used as the overcoat layer is a liquid photo solder resist composed of an epoxy acrylate resin and a filler, and a desired pattern can be formed by coating, baking, developing and curing.

  The LED chip mounting wiring section 3 has nickel plating on copper and silver plating thereon. Nickel plating functions as a copper overcoat layer. The silver plating not only has a function as a wiring conductor, but also has a function of a reflecting plate that reflects light in all directions emitted from the LED chip.

  The first embodiment is an example in which titanium is used as a material for a specific ultra-thin metal film, and the entire surface of the LED chip mounting surface, that is, the insulating resist 6 and the LED chip mounting wiring portion 3 is subjected to heat treatment. An ultra-thin titanium film 11 is provided.

  The wiring conductor 4 that is not covered with the insulating resist 6 except for the LED chip mounting wiring 3 is nickel-plated on copper and gold-plated or tin-plated on the copper for connection to an external electrode.

  The reflection frame 12 has a shape and a reflection characteristic that gives directivity to light in all directions emitted from the LED chip, and includes a metal, ceramic, or a hard silicone resin mixed with a white filler, a heat resistant resin such as a liquid crystal polymer, Those having a surface plated with metal are used.

  The sealing resin 13 is made of a transparent silicone resin, epoxy resin, or the like. One of the roles of the sealing resin 13 is to protect the mounted LED chip 2 from mechanical shock. Moreover, the uniformity of the light emitted from the LED chip 2 can be improved by dispersing a transparent scattering material in the sealing resin 13. Further, by dispersing phosphors that absorb light emitted from the LED chip 2 and emit light of different wavelengths in the sealing resin 13, it is possible to obtain light in which the emission wavelengths from the LED chip 2 and the phosphor are mixed. . A pseudo white LED device using a blue LED as the LED chip 2 and a YAG silver phosphor that absorbs blue light and emits yellow light as a phosphor is widely known.

Next, a method for manufacturing the LED device of FIG. 1 will be described with reference to FIG.
Here, one LED device is extracted and shown, but actually, a multi-piece substrate is used as shown in FIG. FIG. 2A is a diagram showing the insulating base material 1 having the LED chip mounting wiring part 3 and the wiring conductor part 4. The wiring conductor portions 4 other than the LED chip mounting wiring portion 3 on the LED mounting surface are covered with an insulating resist 6. FIG. 2B shows a state in which the titanium ultra-thin film 10 is formed on the entire surface of the LED chip mounting surface after the substrate is cleaned. FIG. 2C is a diagram in which the LED chip 2 is mounted on the LED chip mounting wiring portion 3 with a die bonding agent and electrically bonded with a gold bonding wire 5. Since the titanium ultrathin film 11 after film formation is conductive and is a very thin film, the bonding wire 5 penetrates the titanium ultrathin film and is firmly bonded to the silver of the LED chip mounting wiring portion 3. FIG. 2D shows a state after the LED chip 2 is mounted, wired, and heat-treated. 11 is an ultra-thin titanium film after heat treatment. The titanium ultrathin film 11 after the heat treatment is transparent and becomes an insulating titanium oxide, the LED chip 2 of the LED chip wiring conductor portion 3 in the figure is mounted, and is bonded to the LED chip 2 by the bonding wire 5. The conduction between the right part and the left part joined to the LED chip 2 by the bonding wire 5 is cut off. FIG. 2E shows a case where a reflective frame 12 is disposed on an insulating resist 6 on which a titanium ultrathin film 11 after heat treatment is formed, and the LED chip 2 is sealed in the reflective frame 12. The LED device which is 1st embodiment of this invention with which resin 13 was filled is shown.

FIG. 3 shows another LED device according to the first embodiment of the present invention using titanium as a material for a specific ultra-thin metal film. In the case of the LED device of FIG. 3, the ultrathin titanium film 10 is formed by dividing the right side portion and the left side portion of the LED chip wiring conductor portion 3 using a mask or the like. The manufacturing method of this LED device is the following:
The mounting and wiring of the ED chip 2, the arrangement of the reflection frame 12, and the filling of the sealing resin 13 are performed.

  The LED device according to the first embodiment of the present invention shown in FIGS. 1 and 2 and FIG. 3 is an example in which the reflective resin 12 is filled with the sealing resin 13. LED devices are also included in embodiments of the present invention.

  In the LED device according to the first embodiment of the present invention shown in FIG. 4, the sealing resin 13 is arranged so as to cover the LED chip on the LED mounting wiring portion 3, and the sealing resin 13 and the reflection frame 12 do not contact each other. LED device of the form. In the LED device of such a form, there is a high risk that the LED chip mounting wiring part 3 not covered with the sealing resin 13 is directly exposed to the atmosphere and contaminated. However, the LED device of the present invention can solve these problems by having the titanium ultrathin film 11 after the heat treatment on the LED chip mounting wiring portion 3. Further, in the case where the titanium ultrathin film is patterned using a mask as in the example of the LED device of FIG. 3, the titanium ultrathin film 10 has the same function.

  The LED device according to the first embodiment of the present invention shown in FIG. 5 is an LED device without the reflection frame 12. As described above, there is a purpose to protect the LED chip 2 mounted as one of the functions of the sealing resin 13 from mechanical shock. However, the wiring breakage due to the ambient temperature or the temperature change between lighting and non-lighting. Therefore, the sealing resin 13 often uses a relatively soft rubber-like resin. Since soft resin inevitably has high gas permeability, in the case of an LED device whose side is not surrounded by a reflection frame made of hard resin, metal, ceramics, or the like, contamination by gas becomes a problem. However, the LED device of the present invention can solve these problems by having the titanium ultrathin film 11 after the heat treatment on the LED chip mounting wiring portion 3. Further, in the case where the titanium ultrathin film is patterned using a mask as in the example of the LED device of FIG. 3, the titanium ultrathin film 10 has the same function.

Next, FIG. 6 shows an example of a test substrate for examining the heat resistance of the silver surface on which the specific ultra-thin metal film is formed and the resistance to hydrogen sulfide gas (sulfur resistance). 6A is a plan view, and FIG. 6B is a cross-sectional view when the test substrate is cut along AA ′. A copper plating layer and a nickel plating layer were formed on the copper-bonded glass epoxy substrate 7, and the portions other than the evaluation portion 8 were covered with an insulating resist 9. The evaluation unit 8 formed a silver plating layer on the nickel plating layer. The area of the evaluation unit 8 is 49 mm ² (7 mm × 7 mm), which is a model of the LED chip mounting wiring unit in the LED device of the embodiment of the present invention.

Example 1
In this embodiment, an example in which titanium is used as a metal is shown.

  As pretreatment, plasma cleaning of the test substrate was performed with a plasma cleaning apparatus PC-300 (manufactured by Samco Corporation). The treatment conditions were RIE mode (reactive ion etching) using argon gas, and the treatment time was 4 minutes.

  After cleaning the substrate, a titanium film test substrate having a titanium ultrathin film layer of 30 mm on the substrate surface was obtained in advance using a sputtering apparatus with a known film forming speed.

  The obtained titanium film test substrate and the untreated test substrate were left in 100 ppm-hydrogen sulfide gas at 25 ° C. for 5 hours to conduct a sulfuration test.

FIG. 7 shows the change in reflectance at 450 nm in the evaluation part before and after the sulfidation test depending on the presence or absence of a titanium ultrathin film. Here, the reason why 450 nm was selected as the measurement wavelength in the reflectance measurement is that silver has a particularly low reflectance in the short wavelength region due to discoloration.
From the results of FIG. 7, it can be seen that the initial reflectance of the evaluation part of the titanium film test substrate is lower than that of the evaluation part of the untreated test substrate, but no discoloration due to hydrogen sulfide gas occurs.

  Moreover, the titanium film test substrate which had been heat-treated at 160 ° C. for 4 hours in advance showed similar sulfurization resistance.

  Furthermore, even when aluminum was used as the specific metal instead of titanium, the substrate after film formation and after heat treatment had similar sulfur resistance.

  From the above results, it can be seen that both the ultra-thin titanium film and the ultra-thin titanium film after heat treatment, and the ultra-thin aluminum film and the ultra-thin aluminum film after heat treatment have antisulfurization properties. There is a high possibility that a specific metal ultrathin film of several tens of kilometers is not an island-like film that covers the entire surface of the underlying silver surface, but the specific metal ultrathin film of the present invention is between the island and the island. Since the voids are smaller than hydrogen sulfide molecules, which are reactive gases, it is considered to have sulfurization resistance.

(Example 2)
Using the titanium film test substrate prepared in Example 1 and the untreated test substrate, a heat resistance test at 160 ° C. in the atmosphere was performed.

FIG. 8 shows the change in reflectance at 450 nm in the evaluation part before and after the heat resistance test depending on the presence or absence of the titanium ultrathin film.
From the results of FIG. 8, the evaluation part of the titanium film test substrate has heat resistance characteristics, and the initial reflectance is lower than that of the evaluation part of the untreated test substrate, but there is no discoloration due to heat. I understand.

It is known that silver grows and discolors due to heat and light. However, silver is oxidized not only by grain growth of silver alone but also by reaction with atmospheric gas and impurities in plating, and these reactions occur. It is said that discoloration due to silver particles generated when an object is re-reduced to silver by heat or light can occur.
The specific ultrathin metal film of the present invention is considered to suppress not only the growth of the silver particles themselves but also the re-reduction reaction from the silver reactant to silver.

  Moreover, further examination was added from the result of FIG. 8, since the reflectance of the evaluation part of a titanium film test board | substrate is higher after the heat test than the initial stage.

(Example 3)
The base material on which titanium was formed was changed from the experimental substrate for evaluation to a glass plate, and after washing the glass plate, a 30-nm titanium ultra-thin film layer was formed in the same manner as in Example 1. The produced titanium film glass plate was heat-treated under various conditions, and the transmittance before and after the treatment was measured.

FIG. 9 shows a change in transmittance at 450 nm by a heat treatment test of a titanium film-formed glass plate.
From the results of FIG. 9, the titanium ultrathin film increased in transmittance at 450 nm by the heat treatment, and the initial titanium ultrathin film was colored, but after the heat treatment, it became a transparent film. The spectrum of the transparent film after the heat treatment was consistent with that of titanium oxide.

Resin materials used in ordinary LED devices are base materials, adhesives, reflective frames, resists, etc., and have continuous high-temperature resistance such as reflow process, but general continuous heat resistance is 200 ° C or less .
It can be seen that the ultra-thin titanium film can be converted to titanium oxide by heat treatment at 200 ° C. or lower.

Example 4
An aluminum film substrate was prepared and subjected to a heat resistance test in the same manner as in Example 2 except that the sputtering target was changed from titanium to aluminum and the film thickness was changed to 34 mm.

FIG. 10 shows the change in reflectance at 450 nm in the evaluation part of the test substrate before and after the heat resistance test.
From FIG. 10, it was found that, similarly to Example 2, the evaluation part of the aluminum film test substrate also has heat resistance, and the reflectance is higher after the heat test than in the initial stage. Similar to the titanium ultrathin film, the aluminum ultrathin film is considered to undergo an oxidation reaction by heat treatment at 200 ° C. or lower.

  As described above, the LED device and the LED device manufacturing method of the present invention can be manufactured without greatly changing the manufacturing process of the conventional LED device by forming a specific ultra-thin metal film on the silver surface by a simple method. This is a high-brightness, long-life LED device that does not degrade the reflectance of the silver surface over time, and a method for manufacturing the LED device.

It is sectional drawing of the LED device of 1st embodiment of this invention. FIG. 3 is a cross-sectional view showing a manufacturing process of the LED device according to the first embodiment of the present invention. It is sectional drawing of the LED device of 1st embodiment of this invention. It is sectional drawing of the LED device of 1st embodiment of this invention. It is sectional drawing of the LED device of 1st embodiment of this invention. It is a figure of the test board | substrate in the Example of this invention. It is a figure which shows the result of the sulfide test in Example 1 of this invention. It is a figure which shows the result of the heat test in Example 2 of this invention. It is a figure which shows the result of the heat processing test in Example 3 of this invention. It is a figure which shows the result of the heat test in Example 4 of this invention. It is sectional drawing of a common LED device. It is the figure which showed an example of the multi-piece substrate of an LED device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation board | substrate 2 LED chip 3 LED chip mounting wiring part 4 Wiring conductor 5 Bonding wire 6 Insulating resist 7 Copper adhesion glass epoxy board 8 Evaluation part 9 Insulating resist 10 Titanium ultra-thin film 11 Titanium ultra-thin film 11 after heat processing 11 Reflection Frame 12 Sealing resin

Claims (2)

An LED device manufacturing method in which an LED chip is mounted on a substrate having an LED chip mounting wiring portion and a wiring conductor portion, and the LED chip mounting wiring portion is dotted in an island shape with a film thickness of 10 mm or more and less than 100 mm. Then, the step of forming a metal ultra-thin film in which the gap between the islands is smaller than hydrogen sulfide molecules, and mounting and wiring the LED chip on the LED chip mounting wiring part on which the metal ultra-thin film is formed The manufacturing method of an LED device which has a process and the process of heat-processing the base material by which the LED chip was mounted in the LED chip mounting wiring part by which the said metal ultrathin film was formed, and was wired. 2. The method of manufacturing an LED device according to claim 1 , wherein the ultrathin metal film is a film made of a metal selected from titanium and aluminum.

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