JP2011222881A - Led package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED package in which light-reflecting silver plating is clearly conducted on a package base and indium plating or indium-cobalt alloy plating is conducted on the silver plating, whereby a light reflection surface of LED is kept to have high luminance irrespective of time lapse or application of heat.SOLUTION: In an LED package having a cavity wich contains an LED chip joined to the bottom surface thereof and is filled with a transparent sealing material, at least the bottom surface of the cavity serving as a silver-plated reflection surface, indium plating or indium-cobalt (In-Co) alloy plating is conducted on the silver plating as protection film. Light-reflecting silver plating is clearly conducted on a package base to solve a problem of tarnishable silver plating, and indium plating or indium-cobalt (In-Co) alloy plating is conducted on the silver plating to prevent change of color over time, whereby high-luminance and high-efficient reflection surface of LED can be stably maintained even at a high temperature applied to LED.

Description

  The present invention relates to an LED package having an improved reflective surface of a cavity in which an LED (light emitting diode) chip is loaded.

  A light-emitting diode is a semiconductor light-emitting element that emits light when an electric current is applied, and is a PN junction diode made of a semiconductor such as GaAs or GaN. Then, positively charged holes (holes) are generated inside the P-type semiconductor, and negatively charged electrons are generated inside the N-type semiconductor, and light is generated when the two are combined. . Depending on the material used to make the PN junction diode, various colors can be emitted.

  White LEDs, which have recently been in the limelight, are used for various displays and illuminations. There are two light emission principles, one of which is a combination of the three primary colors red, green, and blue. The other is to cover the blue LED with a fluorescent material, and the yellow and the original blue emitted from these are synthesized to emit white light. In both cases, a blue LED is required, but this is a major share of the manufacturer, Nichia Chemical Co., Ltd., which succeeded in the invention.

  Regarding the appearance of the LED, there are a shell type, a chip type, a multi-segment type, and the like. In the package forming this, the member is divided into an anode (anode) and a cathode (cathode), an inverted trapezoidal cavity is formed so that at least one of them becomes the bottom surface, and an LED element (chip) is bonded to the bottom surface. And the cathode are connected by wires, and the cavity is filled with a transparent resin and sealed. Therefore, the light emitted from the LED element is reflected on the inner surface of the cavity and emitted from the transparent encapsulant to the outside.

  In order to use the bottom surface of the cavity as a reflecting surface (reflector), the anode and cathode substrates are plated with gold or silver. Among them, gold is excellent in that it is inactive with respect to various compounds and does not cause discoloration. However, since it absorbs blue light, it has a demerit that luminance is lowered as compared with silver plating. On the other hand, in order to protect the silver-plated part from corrosion due to moisture and chemicals, a proposal to prevent the light extraction effect from deteriorating due to discoloration of the silver plating by applying acrylic resin as a primer on the silver plating (Patent Document 1, Patent Document 2).

  In addition, when the conventional silver plating is generally subjected to a discoloration prevention treatment, the substrate of the package is formed separately into an anode and a cathode for the plating step, and both of them are subjected to degreasing and acid activation treatment, A base plating (Cu / Ni alloy or the like) is formed, and a silver plating is applied thereon, followed by a discoloration prevention treatment. For this, an organic discoloration inhibitor (2-heptadelimidazole, 2-mercaptobenzothiazole, thionalide, etc.) is used, and surface treatment is applied to the silver plating by dipping or coating.

2009-206124 2009-290180

  However, according to the conventional discoloration preventing treatment as described above, workability is not good, and discoloration of the silver plating on the surface of the package substrate cannot be stably prevented. In particular, when an organic discoloration inhibitor is used, it is vulnerable to heat, so it loses its function by receiving heat generated from the LED, and silver plating gradually becomes a feature because it reacts with sulfides in the atmosphere of silver. The situation of discoloration was inevitable. Moreover, since the reduction | decrease in reflection efficiency causes the heat | fever of LED to accumulate, there also existed a problem of causing a vicious circle.

  In view of the above situation, the present invention is to apply a silver plating that reflects light cleanly on the package base material, and by applying an indium plating or indium / cobalt alloy plating treatment on the silver plating, An object of the present invention is to provide an LED package in which the light reflection surface of the LED maintains high luminance even when it receives heat over time.

  In order to solve the above-described problems, the present invention provides an LED package in which an LED chip is bonded to a bottom surface and is provided with a cavity filled with a transparent encapsulant, and at least the bottom surface of the cavity is a reflective surface by silver plating. The LED package is characterized in that an indium plating or an indium cobalt (In-Co) alloy plating is applied as a protective film on the silver plating.

  Since the LED package is configured as described above, the silver plating is protected from being discolored by indium plating or indium cobalt (In-Co) alloy plating, but indium plating or indium cobalt (In-Co) alloy plating. Since it withstands high temperatures, this function is reliably performed.

  Indium (In) is an element having an atomic number of 49 and is one of Group 3 elements. Indium is a silver-white soft metal that is stable in air at room temperature. Currently, indium is in high demand for applications such as transparent conductive films, optical devices and semiconductors. Indium-cobalt alloy films have strong heat resistance and are difficult to thermally diffuse with films such as silver against heat, so they are ideal for use in industrial electronic components in the future.

About the characteristic of the film | membrane of an indium plating or an indium cobalt (In-Co) alloy plating, even if it is 0.0001 micrometer, it has the following characteristics.
(1) A soft silver-white uniform film without pinholes can be obtained.
(2) Does not affect the color and gloss of the base plating metal.
(3) The crystals of the film are uniform fine particles.
(4) In the case of an indium-cobalt alloy plating film, an alloy ratio of 50 to 98% indium and 50 to 2% cobalt is optimal.
(5) Even if the thickness of the film is only 0.0001 μm, it is excellent in acid / alkali resistance, sulfur gas resistance and the like.

  Until now, silver discoloration inhibitors using inorganic or organic compounds on the surface of silver have been developed and used, but no effect has been obtained under the environment of LEDs. The present invention pays attention to the characteristics of the above-mentioned indium plating or indium / cobalt alloy plating. In particular, in the reflective surface of the cavity of the LED package that requires stable high reflectance, indium plating or indium / cobalt ( Even if the In—Co) alloy plating is plated with a slight thickness of 0.0001 μm, the knowledge that silver discoloration can be surely prevented can be obtained and the intended purpose can be achieved.

  As described above, according to the LED package of the present invention, the package base material is subjected to silver plating that reflects light cleanly, and solves the disadvantage of silver plating that is easily discolored. By applying indium plating or indium-cobalt (In-Co) alloy plating, discoloration is prevented over time, and it is possible to stably maintain a high-brightness and high-efficiency reflective surface even at high temperatures related to LEDs. There is an effect.

It is sectional explanatory drawing of one procedure which shows the LED package of this invention in the outline production point of LED. It is explanatory drawing of the following procedure. It is explanatory drawing of the following procedure. It is explanatory drawing of the following procedure. It is explanatory drawing of the following procedure. It is explanatory drawing which LED completed. It is sectional explanatory drawing corresponding to FIG. 6 which shows another Example. It is sectional explanatory drawing corresponding to FIG. 6 which shows another Example.

  In the present invention, silver plating 5 is applied to one or both of the anode substrate 1a and the cathode substrate 1b constituting the LED package, and indium plating or indium cobalt (In-Co) mainly intended to prevent discoloration thereon. ) Alloy plating 7 is applied. Examples of indium plating include a cyanide bath, a sulfamate bath, and a borofluoride bath. In the case of an indium-cobalt alloy, it is a plating bath composed of an inorganic acid compound such as sulfamic acid or an organic acid compound such as citric acid.

  (1) A cyanide bath provides a glossy plating with good adhesion. However, it is necessary to use an insoluble anode, and the management of the bath is somewhat difficult compared to other baths.

[Cyanide bath composition and plating conditions]
Indium concentration 35g / 1
Potassium cyanide 100g / 1
Potassium hydroxide 60g / 1
Additive Appropriate amount pH 13 or more Bath temperature 20 to 30 ° C or more Cathode current density 1 to ^{2 A} / dm ²
Agitation Cathode locker

(2) In the sulfamate bath, indium can be used as an anode, and plating with good color tone can be obtained stably.
[Sulfamate bath composition and plating conditions]
Indium sulfamate 100g / 1
Sodium sulfamate 150g / 1
Sulfamic acid 25g / 1
Additive appropriate amount pH 1.5-2.5
Bath temperature 20-30 ° C
Cathode current density 1-2 A / dm ²
Stirring air

(3) The borofluoride bath can use indium for the anode, and the bath structure can be finely plated with little fluctuation.
Also, plating can be performed at a high concentration and a high current density.
[Borofluoride bath composition and conditions]
Indium borofluoride 230g / 1
Boric acid 20g / 1
Ammonium borofluoride 40g / 1
Additives Appropriate amount pH (with borofluoric acid) 1-2
Bath temperature 20-30 ° C
Cathode current density 1-2 A / dm ²
Stirring air

  A characteristic of the indium plating solution is that it is economical because the bath temperature is 20 to 30 ° C., and the stability of the plating solution is excellent. Moreover, since it can be used for a long time by the replenishment method and the management items of the plating solution are only pH and indium metal concentration, it is easy to manage the solution during work.

(4) An indium / cobalt alloy plating bath of a sulfamic acid compound has a low bath temperature and pH, and the crystal of the alloy film is dense.
[Sulfamic acid compound bath composition and plating conditions]
Indium sulfamate 100g / L
Cobalt sulfate 20g / L
Potassium sulfamate 200g / L
Monopotassium dihydrogen phosphate 30g / L
Additive appropriate amount pH 1.5-3.0
Bath temperature 20-30 ° C
Cathode current density 0.5 to 3.0 A / dm ²
Plating time 5 ~ 40 seconds

(5) The characteristics of the indium-cobalt alloy plating bath of organic acid compound are weak acidity, good plating coverage, stable ratio of alloy film, and the highest density of alloy film crystals. Gas etc. are good.
[Indium / cobalt alloy bath composition of organic acid compound and plating conditions]
Indium metal concentration 30g / L
Cobalt metal concentration 5g / L
Tartaric acid 120g / L
Potassium sodium tartrate 50g / L
Polyethylene glycol # 1000 1-2g / L
pH 3.6-5.4
Bath temperature 30-65 ° C
Agitation Machine / medium agitation Cathode current density 0.2-5A / dm ²
Plating time 3-60 seconds

  The characteristics of the indium-cobalt alloy plating film are the alloy ratio of indium 50 to 98% and cobalt 50 to 2%, and the crystal of the alloy film is the most dense, so the sulfur-resistant gas, acid-alkali resistance, etc. of the silver plating film are good It is. Therefore, it is highly likely to be widely used in fields such as electronic parts in the future.

  FIG. 1 to FIG. 6 show the package in the manufacturing procedure of the surface mount type LED (chip type), and the plating thickness is very small. In these figures, however, the plating thickness is excessive in the cross section for convenience of explanation. The thickness was shown.

  The base material of the package consists of an anode base material 1a and a cathode base material 1b, and both are obtained by processing a plate material with a press 3 (FIG. 1). Both of them are subjected to degreasing and acid activation (cleaning the surface after alkali degreasing), after the copper alloy base plating, silver plating 5 and indium plating or indium cobalt (In-Co) alloy plating 7 Are sequentially performed (FIG. 2). Indium plating is performed using the plating bath and conditions described in (1) (or (2), (3)) and in the case of indium-cobalt alloy plating (4) or (5).

  Next, the anode base material 1a and the cathode base material 1b are joined together by the resin molding part 9 by a kind of insert molding, and the cavity 11 is provided in the central part of the resin molding part 9 (FIG. 3). The cavity 11 has a bottom surface that is an exposed surface of the base materials 1a and 1b, and a silver plating 5 on the top surface that is a clean reflecting surface through an indium plating or indium cobalt (In-Co) alloy plating 7. . In addition, on the bottom surface, resin is filled between the anode base material 1a and the cathode base material 1b, and the interval is maintained. Further, the inner surface of the cavity 11 is inclined so that reflected light to the outside can be obtained.

  The LED chip 13 is fixed on the upper surface of the cathode substrate 1b with a silver paste (FIG. 4). The LED chip 13 is connected (bonded) to the anode substrate 1a and the cathode substrate 1b via gold wires 15a and 15b, respectively (FIG. 5). In this state, the cavity 11 is filled with a transparent encapsulant 17 made of acrylic resin.

  FIG. 7 shows a surface-mount type LED similar to the above-described embodiment (Note that, unlike FIGS. 1 to 6, the plating thickness is not shown in cross section. The same applies to FIG. 8).

  In this case, the anode base material 1a and the cathode base material 1b on which the silver plating 5 and the indium plating or the indium-cobalt (In-Co) alloy plating 7 have been applied with the copper alloy plating as a base joint with each other. In the upper part, the cathode base material 1b side is long and the anode base material 1a side is short. In this way, the LED chip 13 can be bonded to the cathode substrate 1b while being positioned as central as possible.

  FIG. 8 shows a bullet-type LED. Of the anode base material 1a and the cathode base material 1b, a bulging portion 14 is provided at the upper end portion of the cathode base material 1b, and a cavity 11 is formed by providing a recess there. Thus, the silver plating 5 and the indium plating or the indium-cobalt (In-Co) alloy plating 7 are applied only to the cathode base material 1b (whole) with the copper alloy plating as a base.

  Also in this case, the LED chip 13 is connected to the anode substrate 1a and the cathode substrate 1b via wires 15a and 15b, and the cavity 11 is filled with the transparent encapsulant 17, but the lens 19 is insert-molded. Thus, the anode substrate 1a and the cathode substrate 1b are integrated as an insert.

The silver plating for LEDs is required to have the following qualities, but these were effectively retained by the indium plating 7.
(1) Glossiness (0.4 to 0.8)
(2) Reflectivity maintenance (3) Sulfur resistance after heat resistance (300 ° C) (discoloration over time)
(4) Wire bondability With respect to these characteristics, the following tests were conducted and it was confirmed that these requirements were secured.
(I) Sulfur dioxide gas test as discoloration test (SO225 ± 5ppm, room temperature ± 1 ° C, humidity 80 ± 5%)
(B) Hydrogen sulfide gas test (H2S10 ± 2ppm, room temperature 40 ± 1 ° C, humidity 80 ± 5%)
Incidentally, as a comparative example, conventionally, the organic color change was generally prevented, but this film was broken at about 200 ° C. Since indium plating or indium-cobalt (In—Co) alloy plating 7 can withstand 300 ° C., it can be seen that the present invention is more excellent.

DESCRIPTION OF SYMBOLS 1a Anode base material 1b Cathode base material 5 Silver plating 7 Indium plating or indium-cobalt (In-Co) alloy plating 9 Resin molding part 14 Swelling part

Claims (5)

  An LED package having a cavity in which an LED chip is bonded to a bottom surface and filled with a transparent encapsulant, and at least the bottom surface of the cavity is a reflective surface by silver plating. Indium plating or indium cobalt on the silver plating An LED package, wherein (In—Co) alloy plating is applied as a protective film.   The anode base material and the cathode base material are integrated by molding the resin molding part with a space therebetween, and a recess is formed in the central part of the resin molding part to form a cavity in which both base materials are exposed on the bottom surface. By applying silver plating and indium plating or indium-cobalt (In-Co) alloy plating to the base material, the bottom surface of the cavity is coated with indium plating or indium-cobalt (In-Co) alloy plating on the silver plating as a protective film The LED package according to claim 1, wherein the LED package is a reflective surface.   An anode base material and a cathode base material which are integrated by resin molding of the lens are provided at a distance, and the cathode base material is provided with a bulging portion which protrudes toward the anode base material at the upper end portion, and is bulged. A cavity is formed by providing a recess in the part, and by applying silver plating and indium plating or indium-cobalt (In-Co) alloy plating to the cathode base material, the entire inner surface of the cavity is placed on the silver plating. The LED package according to claim 1, wherein the LED package is a reflective surface applied with indium plating or indium cobalt (In—Co) alloy plating as a protective film.   4. The LED package according to claim 1, wherein the protective film of the silver plating film is 100% indium in the case of indium single plating. 4. In the case of an indium / cobalt alloy plating film as a protective film for the silver plating film, the alloy ratio is 50% to 98% indium and 50% to 2% cobalt. LED package.

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