JP2015124427A - Plating solution used for lead frame or substrate for light emitting device, lead frame or substrate produced using the same and method of producing the same, and light emitting device comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silver or silver alloy plating solution which makes it possible to obtain a higher total luminous flux of a light emitting device as compared with conventional one.SOLUTION: A plating solution of the invention is a silver or silver alloy plating solution used for plating of a lead frame or substrate for a light emitting device, at least comprising 0.1 g/L or more and 15 g/L or less of a silver cyanide complex and 50 g/L or more and 250 g/L or less of an electrical conductive salt, and having a pH of 8 or more and 13.5 or less and a deposition efficiency of 0.5% or more and 50% or less.

Description

  The present invention relates to a silver or silver alloy plating solution used for plating of a lead frame or substrate for a light emitting device, a lead frame or substrate for a light emitting device manufactured using the same, a method of manufacturing the same, and light emission including the same. It relates to the device.

  A light-emitting device typified by a light-emitting diode (LED) is widely used as a light source for lighting, various displays, a liquid crystal television, and a backlight of a mobile phone. In many cases, silver plating is applied to the lead frame and various substrates in order to improve the mounting reliability of the light emitting device to these devices.

  Conventionally, the silver plating solution used when silver plating is applied to a lead frame or a substrate for a light emitting device is only a silver plating solution for a lead frame for an electronic device such as a transistor or an IC. It was. Regarding such a silver plating solution, for example, Patent Literature 1 and Patent Literature 2 describe a method for producing a brightener for glossing a silver plating film. For example, Patent Literature 3 and Patent Literature 4 describe a silver plating solution devised so that partial plating can be performed in order to improve die bonding property, wire bonding property, and productivity of a silver plating film. However, these have not been studied at all for the light reflection characteristics required for the light emitting device.

  On the other hand, in order to improve the light extraction efficiency of the light emitting device, for example, Patent Document 5 discloses a technique for adjusting the crystal size of a silver plating film, and Patent Document 6 discloses a technique for forming another film on the uppermost layer of the silver plating film. Patent Document 7 discloses a technique using silver alloy plating, but the silver plating solution used is not a novel one, but only a conventional silver plating solution.

  Currently, in order to realize higher light extraction efficiency of the light emitting device, improvement in performance as a lead frame as a mounting member or a reflector of a substrate is expected. However, the conventional silver plating solution or silver plating method may improve the reflectivity of the obtained silver plating film, but it does not necessarily improve the total luminous flux that is an indicator of the actual brightness of the light emitting device. there were.

U.S. Pat. No. 2,807,576 U.S. Pat. No. 3,580,821 U.S. Pat. No. 4,247,372 Japanese Patent Laid-Open No. 05-222569 Japanese Patent No. 4367457 JP 2011-204790 A

  Then, this invention is made | formed in view of this situation, and makes it a subject to provide the silver or silver alloy plating solution from which the high total luminous flux of a light-emitting device is obtained compared with the former.

  In order to solve the above problems, the plating solution of the present invention is a silver or silver alloy plating solution used for plating of a lead frame for a light emitting device or a substrate, and has a concentration of 0.1 g / L to 15 g / L. It contains at least a silver cyanide complex and an electric conductive salt of 50 g / L or more and 250 g / L or less, has a pH of 8 or more and 13.5 or less, and has a precipitation efficiency of 0.5% or more and 50% or less. To do.

  The lead frame or substrate for a light emitting device of the present invention has a silver or silver alloy plating film having a glossiness of 1.0 or more plated with the plating solution of the present invention on the surface, or is plated with the plating solution of the present invention. The surface is provided with a silver or silver alloy plating film having a reflectance of 90% or more with respect to light having a wavelength of 450 nm or more.

  The light-emitting device of the present invention includes the light-emitting device lead frame or substrate of the present invention and a light-emitting element mounted on the lead frame or substrate.

The method for producing a lead frame or substrate for a light emitting device according to the present invention comprises forming a base film of silver or a silver alloy having a thickness of 0.1 μm or more and 10 μm or less by electroplating on the surface of the substrate, Using a plating solution, electroplating is performed at a temperature of 15 ° C. to 60 ° C., a cathode current density of 0.5 A / dm ^{2 to} 30 A / dm ² and a plating time of 3 seconds to 3 minutes. Including a process.

  By applying the silver or silver alloy plating solution of the present invention to the plating of a lead frame for a light emitting device and a substrate, it is possible to improve the light emission efficiency of the light emitting device and stabilize the quality of the light emitting characteristics between the light emitting devices. Thereby, for example, the number of light emitting devices mounted in LED light bulbs and backlights for liquid crystal televisions can be reduced, and energy saving and manufacturing cost can be reduced. In addition, variation in light emission characteristics between light emitting devices can be suppressed, and manufacturing yield can be improved.

<Embodiment 1>
Embodiments of the invention will be described below. However, the silver or silver alloy plating solution described below, the lead frame or substrate for a light emitting device, and the manufacturing method thereof, and the light emitting device provided therewith are for embodying the technical idea of the present invention, Unless specifically stated, the invention is not limited to the following.

  In the present embodiment, the lead frame for a light emitting device refers to a lead frame on which at least a light emitting element is mounted, and preferably refers to a lead frame including a pair of a positive electrode and a negative electrode. The light emitting device substrate means a substrate on which at least a light emitting element is placed. Examples of the substrate include a printed substrate such as a resin (including a fiber reinforced resin), a ceramic substrate, a flexible substrate, and the like on which wirings and circuits are formed.

  For example, the light-emitting device is obtained by die-bonding a light-emitting element to a lead frame or a substrate with an adhesive such as silver paste or resin, wire bonding with a gold wire, or the like, and sealing with a sealing member such as resin. Often manufactured. The light emitting device is mounted by solder reflow or the like when mounted on, for example, an LED bulb or a backlight for a liquid crystal television.

Note that the light-emitting element is a nitride semiconductor (In _x Al _y Ga _1-xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1 from the viewpoint of emitting short-wavelength light that can excite the phosphor efficiently. ) Is preferable, but a gallium arsenide semiconductor or gallium phosphorus semiconductor may also be used. The emission wavelength of the light-emitting element is not particularly limited, but from the viewpoint of the color mixing relationship with the light emission of the phosphor and the light emission efficiency, for example, 400 nm to 530 nm can be mentioned, and preferably 430 nm to 490 nm, preferably 450 nm to 475 nm. The following is more preferable. Phosphors include cerium activated yttrium aluminum garnet, europium and / or chromium activated nitrogen-containing calcium aluminosilicate, europium activated sialon, europium activated silicate, manganese activated fluoride. Examples thereof include potassium silicate. Examples of the sealing member include a silicone resin, an epoxy resin, or a modified resin or a hybrid resin thereof. In addition, the lead frame or the substrate for the light emitting device may be provided with an enclosure for surrounding the light emitting element. Examples of the base material of the enclosure include thermosetting resins such as epoxy resins and silicone resins, thermoplastic resins such as polyamide resins and polycyclohexane terephthalate, and modified resins and hybrid resins thereof. These base materials may contain particles or fibers of glass, calcium silicate, potassium titanate, titanium oxide, zinc oxide, silicon oxide or the like as a filler or a coloring pigment. The enclosure can be formed by transfer molding, injection molding, or a dropping (potting) method.

  In order to industrially perform the assembly process and mounting process of such a light emitting device with stable quality, the lead frame and the substrate for the light emitting device are subjected to silver plating. Such silver plating is required to obtain a high total luminous flux as a light emitting device, in addition to demands such as highly reliable die / wire bonding, stable solder wettability, and high adhesion to a sealing resin. . However, the conventional silver plating has been developed as a silver plating for lead frames for electronic devices as described above, and has not been considered to satisfy the requirement of high total luminous flux.

  Accordingly, when a silver or silver alloy plating solution for use in plating of a lead frame or a substrate for a light emitting device is intensively studied, a silver cyanide complex of 0.1 g / L to 15 g / L and 50 g / L to 250 g / L are obtained. A lead frame or a substrate for a light-emitting device is used by using a plating solution containing at least an L or less electrical conductive salt, having a pH of 8 or more and 13.5 or less, and a deposition efficiency of 0.5% or more and 50% or less. It has been found that by applying silver or silver alloy plating, it is possible to manufacture a light emitting device in which the total luminous flux is dramatically improved as compared with the conventional case.

  The detailed mechanism for obtaining such an effect is not clear at present, but when the silver or silver alloy plating solution of the present embodiment is used, specific silver precipitate particles are generated on the plating surface. It is assumed that a high reflectivity is obtained in the visible range, and the function as a reflective film having a high reflectivity can be maintained even after the light emitting device is assembled.

  Of course, the silver or silver alloy plating film obtained by the plating solution of the present embodiment is required for conventional performance such as highly reliable die / wire bonding, stable solder wettability, and high adhesion to the sealing resin. It can be satisfied.

  A silver cyanide complex is used as the silver source of the silver or silver alloy plating solution of the present embodiment. Since the silver cyanide complex is stable in an aqueous solution and has a noble deposition potential, a dense silver or silver alloy plating film having good wire bonding properties can be obtained. The cyanogen silver complex preferably contains at least one selected from silver cyanide, potassium silver cyanide and sodium silver cyanide from the viewpoint of industrial availability.

  The concentration of the silver cyanide complex in the silver or silver alloy plating solution of the present embodiment is preferably 0.1 g / L or more and 15 g / L or less, and more preferably 2 g / L or more and 10 g / L or less. When the concentration of the silver cyanide complex is less than 0.1 g / L, the deposition efficiency becomes too low, and the plating time required to obtain a desired plating thickness becomes very long, which is not economical. On the other hand, when the concentration of the silver cyanide complex exceeds 15 g / L, the deposition efficiency becomes too high, and a silver or silver alloy plating film that can obtain a high total luminous flux cannot be obtained.

  The electrical conductive salt of the silver or silver alloy plating solution of the present embodiment is not particularly limited as long as it is an aqueous solution and has electrical conductivity, but it can be used stably industrially or economically. Alternatively, in order to produce a silver alloy plating solution, it is preferable to contain at least one selected from cyanate, phosphate, nitrate, citrate, and tartaric acid. In addition, soluble organic acid salts are also preferred. These compounds may be used alone or in combination of two or more. Examples of cyanate include potassium cyanide and sodium cyanide. Examples of the phosphate include potassium phosphate, sodium phosphate, ammonium phosphate, and potassium pyrophosphate. Examples of nitrates include potassium nitrate, sodium nitrate, and ammonium nitrate. Examples of the citrate include potassium citrate, sodium citrate, and ammonium citrate. Examples of tartaric acid include potassium tartrate and sodium tartrate.

  The concentration of the electrically conductive salt of the silver or silver alloy solution of the present embodiment is preferably 50 g / L or more and 250 g / L or less in order to make the electric resistance of the silver or silver alloy plating solution appropriate. If the concentration of the electroconductive salt is less than 50 g / L, the electric resistance of the plating solution becomes too high, and plating production with an appropriate cathode current density cannot be performed. On the other hand, if the concentration of the electrically conductive salt exceeds 250 g / L, the viscosity of the plating solution becomes excessive, ion mobility decreases, and plating with an appropriate cathode current density cannot be performed. It is not economical because there are many carry-outs.

  The pH of the silver or silver alloy plating solution of the present embodiment is preferably 8 or more and 13.5 or less. When the pH is less than 8, the silver cyanide complex becomes unstable and tends to be insoluble silver cyanide. On the other hand, if the pH exceeds 13.5, a large amount of alkali is required to maintain the pH, which is not economical. In addition, let pH here be a measured value at the liquid temperature of 25 degreeC.

  The deposition efficiency of the silver or silver alloy plating solution of the present embodiment is preferably 0.5% or more and 50% or less, and more preferably 1% or more and 40% or less. In addition, the precipitation efficiency here means what is calculated by the following formula according to Faraday's law.

  Deposition efficiency (%) = 100 × {96500 × precipitation weight (grams) × valence} / {atomic weight × current (ampere) × plating time (seconds)}

  When the deposition efficiency is less than 0.5%, a silver or silver alloy plating film capable of obtaining a high total luminous flux can be obtained. However, the plating time required for obtaining a desired plating thickness becomes very long, which is not economical. On the other hand, if the deposition efficiency exceeds 50%, a silver or silver alloy plating film that provides a high total luminous flux cannot be obtained.

  Examples of the silver alloy plating solution of the present embodiment include those added with a soluble metal salt such as gold, copper, palladium, platinum, nickel, and antimony in addition to the silver cyanide complex.

  In addition, various surfactants can be added to the silver or silver alloy plating solution of the present embodiment in order to suppress the occurrence of unevenness in the silver or silver alloy plating film. Examples of the surfactant include nonionic surfactants such as polyoxyalkyl ether condensates.

  Further, a pH buffering agent for stabilizing the pH can be added to the silver or silver alloy plating solution of the present embodiment. Examples of the pH buffer include boric acid, potassium metaborate, and phthalate.

  Moreover, you may add brighteners, such as a sulfur compound, a selenium compound, and an antimony compound, to the silver or silver alloy plating solution of this Embodiment.

  The silver or silver alloy plating solution of the present embodiment is coated with, for example, metallic silver, metallic silver alloy, stainless steel, platinum group metal, or platinum group metal, using an object to be plated (in this example, a lead frame or substrate) as an anode. The present invention can be applied to a plating method in which electroplating is performed by immersing in a plating solution using titanium as a cathode.

  The silver or silver alloy plating solution of the present embodiment is a so-called rack type plating method of a manual or automatic elevator system, a reel-to-reel type and an electroplating tank is an overflow type plating method, or an electronic device lead frame. Any of the jet-type plating methods employed for partial plating can be used.

  In the present embodiment, the liquid temperature at which silver or silver alloy plating is performed varies depending on the flow rate and stirring state of the plating apparatus, but is preferably approximately 15 ° C. or higher and 60 ° C. or lower. When the liquid temperature is less than 15 ° C., plating with a high current density cannot be performed, and energy loss for cooling the plating liquid in the summer increases. On the other hand, when the liquid temperature exceeds 60 ° C., the evaporation of the plating solution becomes large, and the adjustment of the liquid amount becomes difficult.

Moreover, in this Embodiment, the cathode current density which performs silver or silver alloy plating changes with the flow rates and stirring state of a plating apparatus. The cathode current density is preferably 0.5 A / dm ² or more and 10 A / dm ² or less in rack plating or overflow plating, and is preferably 5 A / dm ² or more and 30 A / dm ² or less in jet plating. When the cathode current density is less than 0.5 dm ² , the deposition rate is extremely reduced, which is not economical. On the other hand, when the cathode current density exceeds 30 A / dm ² , rough plating deposition occurs, and a silver or silver alloy plating film capable of obtaining a high total luminous flux cannot be obtained.

  Further, in the present embodiment, the plating time for performing silver or silver alloy plating can be appropriately adjusted according to the flow rate and stirring state of the plating apparatus, the liquid temperature, the cathode current density, and the concentration of the silver cyanide complex, but 3 seconds or more. 3 minutes or less is preferable. If the plating time is less than 3 seconds, a silver or silver alloy plating film that provides a high total luminous flux cannot be obtained. Further, even if the plating time exceeds 3 minutes, a silver or silver alloy plating film that can obtain a high total luminous flux cannot be obtained.

  Further, the silver or silver alloy plating solution of the present embodiment can be used for silver or silver alloy plating of a lead frame, but the lead frame after silver or silver alloy plating is formed into a lead frame that is plastically deformed by rolling or the like. Can also be applied.

In the present embodiment, a silver or silver alloy plating film having a thickness of 0.1 μm or more and 10 μm or less is formed on the surface of the substrate by electroplating, and then the silver or silver alloy plating solution of the present embodiment is used. Electroplating under conditions of a liquid temperature of 15 ° C. to 60 ° C., a cathode current density of 0.5 A / dm ^{2 to} 30 A / dm ² and a plating time of 3 seconds to 3 minutes. it can. In addition, as a base | substrate, 1 type chosen from copper, a copper alloy, iron, an iron alloy, aluminum, an aluminum alloy, a ceramic, and resin is mentioned.

  The glossiness of the silver or silver alloy plating film obtained in the present embodiment is not particularly limited, but is preferably 1.0 or more and more preferably 1.3 or more in order to obtain a high total luminous flux. preferable. Moreover, it is preferable that the glossiness of the base film is 1.0 or more because a higher total luminous flux can be easily obtained. The glossiness here is glossiness widely used in the lead frame industry. For example, Densitmeter Model 144 manufactured by GAM, Micro Surface Color Meter / Reflectometer VSR400 manufactured by Nippon Denshoku Industries Co., Ltd. It is a numerical value measured with a tometer (reflection densitometer) ND-11. Further, the reflectance of the silver or silver alloy plating film obtained in the present embodiment with respect to light having a wavelength of 450 nm or more is preferably 90% or more, and more preferably 95% or more. The silver or silver alloy plating film is preferably on the surface of the lead frame or substrate, but a translucent film may be provided on the silver or silver alloy plating layer. This film can be made of, for example, aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, a mixture thereof, or various resins.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited only to these Examples.

<Examples 1 to 23>
The light emitting devices of Examples 1 to 23 are manufactured as follows. As a lead frame material (base), a KLF194 (CDA No. C19400, iron content rate 2.3%) copper plate 0.11 mm made by Kobe Steel Co., Ltd. was used. LED open frame FLASH LED 6PIN OP1 (external dimension: 5050) type is used. First, this is degreased with an alkaline degreasing agent, then acid neutralized with dilute sulfuric acid, and then copper plating is applied in a thickness of 0.5 μm with a cyan bath. Thereafter, silver or silver alloy plating is performed with the plating solution of the present invention, washed with clean pure water, and then dried to produce a lead frame having a silver or silver alloy plating film on the surface. The silver or silver alloy plating is full silver plating or full silver alloy plating. This lead frame is placed in a mold, polyphthalamide resin is injected as a molding material, and cured to be removed from the mold. Then, an InGaN-based blue light-emitting diode element is placed on a resin-molded lead frame via a resin adhesive, and then heated and bonded at 150 ° C. for 1 hour. Thereafter, the electrode of the light emitting diode element and the lead frame are connected with a gold wire having a diameter of 25 μm. Next, a 20% proportion of YAG phosphor blended with the modified silicone resin is filled into the opening of the resin molded body and cured with a hot air dryer (curing conditions: 150 ° C., 4 hours), and sealed. Stop. Then, it cut | disconnects as an individual light-emitting device.

<Comparative Examples 1 and 2>
The light emitting devices of Comparative Examples 1 and 2 are fabricated in the same manner as the light emitting devices of Examples 1 to 23 except that a conventional silver plating solution is used.

<Evaluation 1>
The total luminous flux [Phi] v (lm) in the light emitting devices of Examples 1 to 23 and Comparative Examples 1 and 2 obtained as described above is measured with an integral type total luminous flux measuring apparatus. Table 1 shows the silver or silver alloy plating solution and the silver or silver alloy plating conditions and the total luminous flux Φv (lm) of the light emitting device in each of the examples and comparative examples.

<Examples 24-46>
The light emitting devices of Examples 24-46 are manufactured as follows. As a lead frame material (base), a KLF194 (CDA No. C19400, iron content rate 2.3%) copper plate 0.11 mm made by Kobe Steel Co., Ltd. was used. LED open frame FLASH LED 6PIN OP1 (external dimension: 5050) type is used. First, this is degreased with an alkaline degreasing agent, then acid neutralized with dilute sulfuric acid, and then copper plating is applied in a thickness of 0.5 μm with a cyan bath. Thereafter, using a silver plating solution of silver potassium cyanide = 70 g / L, potassium cyanide = 100 g / L, potassium selenium cyanide = 2 ppm, plating is performed at a liquid temperature of 25 ° C. and a current density of 3 A / dm ² for 2 minutes. A base film of silver plating having a glossiness of 1.5 μm of 3 μm is obtained. Thereafter, silver or silver alloy plating is performed with the plating solution of the present invention, washed with clean pure water, and then dried to produce a lead frame having a silver or silver alloy plating film on the surface. The silver or silver alloy plating is full silver plating or full silver alloy plating. This lead frame is placed in a mold, polyphthalamide resin is injected as a molding material, and cured to be removed from the mold. Then, an InGaN-based blue light-emitting diode element is placed on a resin-molded lead frame via a resin adhesive, and then heated and bonded at 150 ° C. for 1 hour. Thereafter, the electrode of the light emitting diode element and the lead frame are connected with a gold wire having a diameter of 25 μm. Next, a 20% proportion of YAG phosphor blended with the modified silicone resin is filled into the opening of the resin molded body and cured with a hot air dryer (curing conditions: 150 ° C., 4 hours), and sealed. Stop. Then, it cut | disconnects as an individual light-emitting device.

<Comparative Examples 3 and 4>
The light emitting devices of Comparative Examples 3 and 4 are produced in the same manner as the light emitting devices of Examples 24-46, except that a conventional silver plating solution is used.

<Evaluation 2>
The total luminous flux [Phi] v (lm) in the light emitting devices of Examples 1 to 23 and Comparative Examples 1 and 2 obtained as described above is measured with an integral type total luminous flux measuring apparatus. Table 2 shows the silver or silver alloy plating solution and the silver or silver alloy plating conditions and the total luminous flux Φv (lm) of the light emitting device in each example and comparative example.

  As shown in Table 1, the total luminous flux values of Examples 1 to 23 are about 6 to 10% higher than those of Comparative Examples 1 and 2. Moreover, as shown in Table 2, compared with Comparative Examples 3 and 4, the total luminous flux values of Examples 24-46 are about 10-15% higher.

Claims (7)

A silver or silver alloy plating solution used for plating of a lead frame or a substrate for a light emitting device,
It contains at least 0.1 g / L or more and 15 g / L or less of a silver cyanide complex and 50 g / L or more and 250 g / L or less of an electrically conductive salt, has a pH of 8 or more and 13.5 or less, and a deposition efficiency of 0.5. A plating solution that is not less than 50% and not more than 50%.   The plating solution according to claim 1, wherein the silver cyanide complex contains at least one selected from silver cyanide, potassium potassium cyanide, and sodium silver cyanide.   The plating solution according to claim 1 or 2, comprising at least one selected from cyanate, phosphate, nitrate, citrate, and tartrate as the electrically conductive salt. A lead frame or a substrate for a light emitting device, comprising a silver or silver alloy plating film having a glossiness of 1.0 or more plated with the plating solution according to any one of claims 1 to 3.
[Claim 5]
The lead frame or substrate for a light-emitting device according to claim 4, wherein the silver or silver alloy plating film has a reflectance of 90% or more with respect to light having a wavelength of 450 nm or more. A lead frame or a substrate for a light emitting device, comprising a silver or silver alloy plating film having a reflectance of 90% or more with respect to light having a wavelength of 450 nm or more plated with the plating solution according to any one of claims 1 to 3.
[Claim 7]
A light emitting device comprising: the lead frame or substrate for a light emitting device according to any one of claims 4 to 6; and a light emitting element placed on the lead frame or substrate. After a base film of silver or a silver alloy having a thickness of 0.1 μm or more and 10 μm or less is formed on the surface of the substrate by electroplating, the plating solution according to claim 1 is used to form a liquid Lead for light-emitting device including a step of performing electroplating under conditions of a temperature of 15 ° C. to 60 ° C., a cathode current density of 0.5 A / dm ^{2 to} 30 A / dm ² and a plating time of 3 seconds to 3 minutes. A method for manufacturing a frame or a substrate.   The method for manufacturing a lead frame or a substrate for a light emitting device according to claim 8, wherein the glossiness of the base film is 1.0 or more.