JP5602578B2 - LED lead frame - Google Patents

Description

  The present invention relates to an LED lead frame constituting a light emitting device using a light emitting diode (LED) used as a light source for a backlight of a liquid crystal display, a lighting fixture, an automobile headlamp, a rear lamp, and the like.

  2. Description of the Related Art In recent years, light-emitting devices using LED elements as light sources have spread in a wide range of fields and applied to various devices, taking advantage of energy saving and long life. As an example of a light-emitting device using an LED element as a light source, the structure and operation of a surface-mounted light-emitting device will be described with reference to FIG. 2A and 2B are external views of a surface-mounted light-emitting device using an LED element as a light source. FIG. 2A is an overhead view, and FIG. 2B is a plan view (top view).

  As shown in FIGS. 2A and 2B, the light emitting device 10 is electrically connected to an LED element (described as “LED” in the drawing) and an electrode (not shown) of the LED element. A pair of lead frames 1a and 1b, which are conductors for supplying a driving current to the LED element, and a resin molded body 2 that supports them are provided. Specifically, the resin molded body 2 has a cup shape in which a concave LED element mounting portion 22 in which the LED element is accommodated is formed, and the LED element mounting portion 22 is opened upward. The lead frames 1a and 1b are belt-shaped, and each penetrates from the outside of the resin molded body 2 to the inside of the LED element mounting portion 22. In each of the lead frames 1a and 1b, a region disposed on the bottom surface of the LED element mounting portion 22 is referred to as an inner lead portion, and a region extending outside the resin molded body 2 is referred to as an outer lead portion.

  The LED element is mounted substantially at the center of the bottom surface of the LED element mounting portion 22, but since one lead frame 1a is disposed at this position, the LED element is bonded to the upper surface of the lead frame 1a with an adhesive (not shown). Is done. The electrodes of the LED elements are connected to the inner lead portions of the pair of lead frames 1a and 1b by bonding wires (wires). Further, the LED element mounting portion 22 is sealed by being filled with a transparent sealing resin (not shown) such as an epoxy resin. And each outer lead part of a pair of lead frames 1a and 1b is connected to a power source (not shown), a drive current is supplied to the LED element, the LED element emits light, and this light is emitted from the opening of the LED element mounting part 22 Irradiated to the outside of the light emitting device 10. In addition, “upper” in this specification indicates the side on which the LED element of the lead frame is mounted in principle.

  In such a light emitting device 10, the light emitting portion (light emitting layer) of the LED element emits light, and light is emitted around the light emitting portion and irradiated in all directions. Among these lights, the light irradiated upward is directly emitted from the opening of the LED element mounting portion 22 to the outside of the light emitting device 10 and used as illumination light or the like. However, the other light irradiated to the side and downward is incident on the side and bottom surfaces of the LED element mounting portion 22 and the surfaces of the lead frames 1a and 1b (inner lead portions) on the bottom surface. Therefore, the resin molded body 2 and the lead frames 1a and 1b are required to have a high light reflectance (hereinafter referred to as reflectance) so that these surfaces reflect light incident from the LED element well. Yes. For example, the resin molded body 2 is formed of a white resin, or a reflective film is formed on each surface of the LED element mounting portion 22 (not shown). On the other hand, the lead frames 1a and 1b are known to be excellent in conductivity and having a reflective film formed on the surface of a common lead frame material made of Cu or Cu alloy as a substrate. In particular, Ag is the most suitable material for such a reflective film because it exhibits the highest reflectance among metals and reflects a large amount of light.

However, Ag reacts with the halogen ions and sulfur contained in the atmosphere and the sealing resin as the usage time of the light emitting device 10 elapses, and a halide or sulfide (Ag ₂ S) such as chloride (AgCl) is formed on the surface. As a result, the surface of the reflective film is discolored or agglomerated due to these products, and the surface is roughened, and Ag is also agglomerated by the heat generated from the LED element, so that the reflectance deteriorates. is there. In addition, when an epoxy resin is used as the sealing resin, Ag in the reflective film diffuses into the transparent epoxy resin and precipitates as Ag nanoparticles, and changes its color to brown to deteriorate the light transmittance.

  In order to solve this problem, for example, Patent Document 1 discloses that an Ag—Au alloy plating layer in which a silicone resin is applied as a sealing resin and chloride or sulfide is difficult to form on a pure Ag plating layer on a reflective surface. A lead frame is further described. In Patent Document 2, an Ag alloy film containing Ge and Bi is formed by plating or the like, and then a reflector (corresponding to the resin molded body 2 in FIG. 2) is formed from a thermoplastic resin, or heat treatment is performed. A lead frame is described in which Ge and Bi of the Ag alloy film are diffused and concentrated on the surface by heating at that time, making it difficult to form silver halide.

JP 2008-91818 A (Claims 1 and 2, paragraph numbers 0015 to 0016) JP 2008-192635 A (Claim 1)

  However, the Ag-Au alloy film of Patent Document 1 is made of an alloy containing Au as a main component, in which the Ag content is limited to less than 50% by mass in order to make it difficult to form chlorides and sulfides. Therefore, the reflectance is inferior and the cost is also increased. In the Ag alloy film of Patent Document 2, it is difficult to form an Ag alloy film in which the Ge and Bi concentrations are controlled by plating, and the Ge and Bi are stably concentrated on the surface of the Ag alloy film by the subsequent heat treatment. It is also difficult to make it. In particular, the temperature and time are insufficient for the diffusion of Ge to prevent sulfide formation. In such an Ag alloy film, the formation of sulfide cannot be sufficiently suppressed. As a resin curing catalyst, metal chlorides such as chloroplatinic acid, metal sulfides, and the like are included.

  An object of the present invention is to provide an LED lead frame including a reflective film that can maintain a high reflectance for a long period of time and can be stably and easily formed. is there.

  The present inventors form an Ag film by plating in order to obtain a smooth surface shape relative to the surface shape of the Cu substrate, and protect the Ag film (Ag plating film) from sulfides in the environment. The idea was to form a protective film. Furthermore, Ag aggregation due to heat tends to be suppressed as the crystal grain size increases, so the Ag-containing film is only an Ag plating film having a relatively large crystal grain size. And about the protective film, even if it was a thin film which does not impair the high reflectance of Ag plating film, the component which can ensure the barrier property with respect to Ag plating film was discovered.

That is, the LED lead frame according to the present invention includes a substrate made of copper or a copper alloy, and an Ag plating film having a thickness of 0.6 μm or more and 8 μm or less formed on at least one side of the substrate, and A metal oxide film of one metal selected from V , Cr, Zr, Nb, Mo, Hf, Ta, and W or an alloy composed of two or more on the Ag plating film has a thickness of 0.5 nm to 15 nm. The root mean square roughness of the surface provided with the metal oxide film is 30 nm or less.

  In this way, by forming an Ag plating film having a high reflectivity and further providing an oxide film of a predetermined metal or alloy on the surface thereof, it is possible to prevent halogen ions and sulfur from coming into contact with the Ag plating film from the outside. And a reflective film with excellent durability.

  In the LED lead frame according to the present invention, a Ni plating film having a thickness of 0.5 μm or more may be further formed between the substrate and the Ag plating film. At this time, the film thickness of the Ag plating film may be 0.2 μm or more, and the total film thickness of the Ni plating film and the Ag plating film is 8 μm or less.

  Thus, by forming a Ni plating film having a large effect of suppressing the diffusion of Cu from the substrate due to heat on the substrate, the diffusion of Cu from the substrate to the surface is suppressed. It becomes a more excellent reflective film. Further, by forming the Ni film by plating, the surface can be sufficiently smoothed even if the thickness of the Ag plating film is suppressed.

  The LED lead frame of the present invention is equipped with an LED element, uses the emitted light with high efficiency to improve the brightness of the illumination light, and suppresses deterioration of the illumination light due to the passage of usage time. A light emitting device. Further, it is not necessary to precisely control the components of the reflective film, such as adding an element imparting durability to Ag in a range where the reflectance is not impaired, and it can be easily formed.

(A), (b) is sectional drawing which shows the structure of the lead frame for LED which concerns on embodiment of this invention. It is an external view which shows the structure of the surface mount type light-emitting device which uses a LED element as a light source, (a) is an overhead view, (b) is a top view. It is sectional drawing which shows the structure of the light-emitting device using the LED lead frame which concerns on this invention, and is a figure corresponding to the AA arrow directional cross-sectional view of FIG. It is a schematic diagram of the lead frame for LED which concerns on another embodiment of this invention, and its board | substrate, (a) is a top view of a board | substrate, (b) is a top view which provided the resin molding in the lead frame for LED ( The figure corresponding to the partial enlarged view of a), (c) is a BB arrow directional cross-sectional view of (b).

  The LED lead frame of the present invention is a component for constituting a light emitting device mounted using an LED element as a light source, and the shape and form of the light emitting apparatus, the LED element mounting form, and the form provided to the user as a product, etc. Depending on the configuration, it is configured in the required shape and form. Hereinafter, the LED lead frame of the present invention will be described in detail with reference to the drawings.

〔Lead frame〕
An LED lead frame (hereinafter referred to as a lead frame) according to an embodiment of the present invention will be described with reference to FIG. The lead frame 1 according to the present invention is a wiring for supplying a driving current for causing the LED element as a light source to emit light when incorporated in the light emitting device 10 shown in FIGS. 2 and 3, for example. The reflective plate reflects the light emitted from the LED element.

  A lead frame 1 according to the embodiment shown in FIG. 1A includes a substrate 11, an Ag plating film 13 formed on at least one surface of the substrate 11, and a metal oxide film 15 formed thereon, Is provided. The Ag plating film 13 and the metal oxide film 15 may be formed only on the upper surface (hereinafter referred to as an appropriate surface) of the substrate 11 on which the LED element is mounted, or the lower surface (rear surface) of the substrate 11. Further, it may be formed on both sides of the substrate 11, and further, only on a part of the surface of the substrate 11, for example, a region where light emitted from the LED element is incident when incorporated in the light emitting device 10. May be. Therefore, the lead frame 1 may have the substrate 11 exposed on the back surface or other regions on the front surface, or two layers or any one of these films 13 and 15 are formed. (For example, refer to FIG. 4C).

(substrate)
The substrate 11 is made of copper or a copper alloy and is formed into the shape of the lead frame 1. As a copper alloy, an alloy containing copper as a main component and containing one or more elements such as Ni, Si, Fe, Zn, Sn, Mg, P, Cr, Mn, Zr, Ti, and Sb, for example, A Cu—Fe—P-based copper alloy can be used. Although the thickness of the substrate 11 is not particularly limited, it is determined according to the shape and form of the light emitting device, as with the shape, and is formed into a base plate (rolled plate) having the required thickness by rolling or the like, and this is pressed. It can be manufactured by forming into a required shape by processing or etching.

(Ag plating film)
In the lead frame 1 according to the present invention, the Ag plating film 13 has a role of reflecting light emitted from the LED element when the light emitting device is used. The Ag film can be formed by physical vapor deposition such as sputtering. However, even if the film formed by physical vapor deposition is formed thick, the surface shape of the base is maintained at the surface shape of the film. That is, since the Ag plating film 13 is formed so as to fill the unevenness of the surface of the substrate 11 and the surface becomes smooth, not only the high reflectivity of Ag but also the reflectivity of the lead frame 1 is made smooth. To make it even higher. Furthermore, the Ag plating film 13 has a relatively large crystal grain size, and an action (aggregation resistance) that suppresses aggregation of Ag due to heat is obtained.

  As long as the Ag plating film 13 is a plating film that forms a smooth surface, it may be any of a matte Ag plating, a semi-gloss Ag plating, and a glossy Ag plating formed by a known plating method. In order to emit light emitted from the LED element to the outside with high efficiency, gloss Ag plating is most preferable. Further, the component is not limited to Ag alone (pure Ag), and may be a plating film formed of an Ag alloy as long as the high reflectance of Ag is maintained. For example, an alloy with a noble metal such as an Ag—Au alloy or an Ag—Pd alloy, an Ag—Bi alloy, or the like can be given.

  The film thickness of the Ag plating film 13 is 0.6 μm or more and 8 μm or less. If the thickness of the Ag plating film 13 is thin, the surface roughness of the substrate 11 is also affected, but the surface of the Ag plating film 13 is not sufficiently smooth. The metal oxide film 15 formed on the Ag plating film 13 and serving as the outermost surface of the lead frame 1 is extremely thin and is a film formed by physical vapor deposition, so that the surface shape of the base is maintained, and the surface of the Ag plating film 13 is maintained. The roughness substantially matches the surface roughness of the lead frame 1. That is, since the surface (reflecting surface) of the lead frame 1 is not smooth, when the light emitting device is used, the diffuse reflection in the reflection increases and the loss of the amount of emitted light increases. Furthermore, when the lead frame 1 is used as the light emitting device 10, Cu diffuses from the substrate 11 to the Ag plating film 13 due to heat. However, if the Ag plating film 13 is thin, Cu reaches the surface. The surface of the Ag plating film 13 may be discolored to reduce the reflectance. Therefore, in order to smooth the surface of the lead frame 1 (the surface of the metal oxide film 15), the thickness of the Ag plating film 13 is 0.6 μm or more, preferably 0.7 μm or more, more preferably 1 μm or more. . Even if the thickness of the Ag plating film 13 exceeds 8 μm, the effect of smoothing the surface is saturated, and if it is formed unnecessarily thick, the cost increases. Therefore, the thickness of the Ag plating film 13 is 8 μm or less. And preferably 7 μm or less, more preferably 6 μm or less.

(Metal oxide film)
The metal oxide film 15 is provided on the outermost surface of the lead frame 1 on the Ag plating film 13, and when used as a light emitting device, Ag of the Ag plating film 13 is composed of halogen ions or sulfur contained in the atmosphere or a sealing resin. It has a role as a protective film for preventing black browning and aggregation by reaction and preventing Ag from diffusing from the Ag plating film 13 into the sealing resin. The metal oxide film 15 is an oxide film of one kind of metal selected from Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W or an oxide film of two or more kinds of alloys.

  Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W each form a stable oxide film (passive film) on the surface in the atmosphere or the like, and thus hardly react with halogen ions or sulfur. Further, these metals have a volume ratio of oxide to the original metal (PB ratio: Pilling-bedworth ratio) exceeding 1, and expand due to oxidation. When the hole is formed, the pinhole is closed by oxidizing to become a metal oxide film. Even if such a metal oxide film 15 is extremely thin, specifically, a film thickness of 2 nm or less, it constitutes a dense protective film that covers the surface of the Ag plating film 13, and the Ag plating film 13 is made of halogen from the outside. Prevent contact with ions and sulfur.

  Further, even if these metal oxide films are coated on the surface of the Ag plating film 13, the reflectance of the lead frame 1 does not greatly decrease from the high reflectance of the Ag plating film 13. In particular, when the metal oxide film 15 is an oxide film of a metal of Ti, Zr, or Ta or an oxide film of an alloy of these metals, the lead frame 1 can be formed even if the metal oxide film 15 is formed to a certain extent. It is preferable because the reflectance does not decrease so much and can be made a sufficient thickness as a protective film for the Ag plating film 13.

  The thickness of the metal oxide film 15 is 0.5 nm or more. When the thickness of the metal oxide film 15 is less than 0.5 nm, it is insufficient as a protective film for the Ag plating film 13. The thicker the metal oxide film 15 is, the higher the effect as a protective film is. Therefore, the thickness is preferably 0.8 nm or more, more preferably 1.0 nm or more. On the other hand, the metal oxide film 15 absorbs a lot of light when the film thickness increases, and when the film thickness exceeds 15 nm, the reflectance of the lead frame 1 is significantly reduced. Therefore, the thickness of the metal oxide film 15 is 15 nm or less, preferably 13 nm or less.

  The film thickness of the metal oxide film 15 can be measured by an X-ray photoelectron spectroscopy (XPS) method. Specifically, using an X-ray photoelectron spectroscopy analyzer, the metal element and oxygen element O contained in the metal oxide film 15 from the surface of the lead frame 1 (surface of the metal oxide film 15) to the depth (film thickness) direction. In addition, each concentration of Ag contained in the Ag plating film 13 is measured to obtain a profile from the surface in the depth direction. The depth at which the concentration (content ratio) of the metal element contained in the metal oxide film 15 is reduced to ½ of the maximum concentration can be defined as the film thickness of the metal oxide film 15.

  The metal oxide film 15 is preferably formed by physical vapor deposition, and it is particularly preferable to use a sputtering method. When forming a metal oxide film using a sputtering method, a metal oxide film may be formed directly using a metal oxide target having the same composition as the metal oxide film, or a metal (alloy) target may be used to form a metal oxide film. After the film (alloy film) is formed, the metal film may be oxidized in an oxygen atmosphere such as the air to form a metal oxide film. However, when a metal oxide film having a thickness of 2 nm or less is formed, pinholes may be formed during the film formation, so that the oxidation treatment is performed after the metal film is formed. When forming a metal oxide film having a thickness of more than 2 nm, any target of metal oxide or metal (alloy) may be used.

  As another embodiment of the present invention, a Ni plating film may be further formed under the Ag plating film. That is, the lead frame 1B according to the embodiment shown in FIG. 1B includes a substrate 11, a Ni plating film 12 formed on at least one surface of the substrate 11, and an Ag plating film 13 formed thereon. And a metal oxide film 15 formed thereon. Similarly to the Ag plating film 13 and the metal oxide film 15, the Ni plating film 12 only needs to be formed at least in a region where light emitted from the LED element is incident when incorporated in the light emitting device 10. Or may be formed on both sides. The substrate 11, the Ag plating film 13, and the metal oxide film 15 are the same as the lead frame 1 shown in FIG. A laminated film of the Ni plating film 12 and the Ag plating film 13 is appropriately shown as a Ni / Ag plating film 14. Hereinafter, the Ni plating film 12 will be described.

(Ni plating film)
In the lead frame 1 </ b> B, the Ni plating film 12 is formed on the surface of the substrate 11 and provided as a base of the Ag plating film 13. Since Ni has an effect of suppressing diffusion of Cu due to heat (Cu diffusion resistance) higher than that of Ag, the Ni plating film 12 has the Cu from the substrate 11 due to heat when the lead frame 1B is used as the light emitting device 10. Diffusion to the Ag plating film 13 via the Ni plating film 12 is suppressed. As a result, even if the thickness of the Ag plating film 13 is made thinner than that of the lead frame 1, Cu reaches the surface of the Ag plating film 13, the surface of the Ag plating film 13 is discolored, and the reflectance decreases. Can be prevented. In order to sufficiently obtain Cu diffusion resistance, that is, heat resistance by the Ni plating film 12, the thickness of the Ni plating film 12 is preferably 0.5 μm or more, more preferably 0.8 μm or more, and further preferably 1 μm or more.

  Further, the Ni plating film 12, like the Ag plating film 13, fills the unevenness of the surface of the substrate 11 and smoothes the surface, so that the surface of the Ag plating film 13 is smoothed together with the Ag plating film 13. Also has a role. The upper limit of the thickness of the Ni plating film 12 is not specified, but the total thickness with the Ag plating film 13 (the thickness of the Ni / Ag plating film 14) is smooth even if the film thickness exceeds 8 μm. If the effect of crystallization and Cu diffusion resistance is saturated and an unnecessarily thick film is formed, the cost increases. Therefore, the total film thickness of the Ni plating film 12 and the Ag plating film 13 is 8 μm or less.

  As long as the Ni plating film 12 is a plating film that forms a smooth surface, the component is not limited to Ni alone, and is formed of, for example, a Ni alloy such as a Ni—Co alloy, a Ni—P alloy, or a Ni—Fe alloy. The plating film may be formed by a known plating method such as electroplating. Furthermore, a bright Ni plating film can form a smooth surface with respect to the surface roughness of the substrate 11, and can further smooth the surface of the Ag plating film 13 formed thereon. ,preferable.

  As described above, since the Ni plating film 12 smoothes the surface of the Ag plating film 13 together with the Ag plating film 13, the Ag plating film 13 is thicker than the surface of the lead frame 1 alone as it smoothes the surface. Can be made thinner. Specifically, the film thickness of the Ag plating film 13 may be 0.2 μm or more, and the surface of the Ag plating film 13 can be sufficiently smoothed by the entire Ni / Ag plating film 14. In this way, in the lead frame 1B, the Ni plating film 12 is formed on the substrate 11 and used as the base of the Ag plating film 13, so that the Ag plating film 13 which is a film containing Ag having a high raw material cost is thickened. There is no need to

  The plan view shape of the lead frames 1 and 1B (hereinafter collectively referred to as the lead frame 1 as appropriate) is not particularly limited, and is designed according to the shape and form of the light emitting device. For example, the substrate 11A (see FIG. 4 (a)), a plurality of lead frames 1A may be connected. Further, the lead frame 1 may be a coiled strip or the like. In this case, the lead frame 1 is processed by cutting, molding, or the like according to the shape or the like of the light emitting device when the light emitting device is manufactured.

(Surface roughness)
The lead frame 1 has a root mean square roughness Rrms (Root Mean Square Roughness) of 30 nm or less on the surface (the surface on the side where the metal oxide film 15 is formed). The root mean square roughness Rrms used as an index representing the smoothness of the surface in the present invention is a value represented by the following formula (1), and is a standard deviation of the surface height of the unevenness present on the surface. Therefore, for example, even if the arithmetic average roughness Ra is equal, the surface having more high protrusions and deep valleys has a larger Rrms. That is, the larger the Rrms, the more severe the surface unevenness, and the light incident on such a surface is more reflected by diffuse reflection and the regular reflectance decreases. In the lead frame 1, if the regular reflectance of the surface is low and the reflection due to diffuse reflection is large, the light extraction efficiency is lowered when the light emitting device is used. Specifically, if Rrms exceeds 30 nm, sufficient illumination light may not be obtained when the light emitting device is formed. On the contrary, as Rrms is smaller, the surface becomes smoother and the regular reflectance is improved, so that the light extraction efficiency when the light emitting device is obtained is improved. Therefore, the Rrms of the surface of the lead frame 1 according to the present invention is 30 nm or less, preferably 25 nm or less, more preferably 20 nm or less.

ここで、Ｚave：表面高さの平均値、Ｚji：個々の表面高さの測定値、Ｎ：測定点の数を示す。
具体的には、例えば、原子間力顕微鏡を用いて、任意の領域について表面高さ（Ｚji）を測定して、式（１）によってＲｒｍｓを算出することができる。好ましくは、複数の領域について測定し、その平均値を適用する。

Here, Zave: average value of surface height, Zji: measured value of individual surface height, N: number of measurement points.
Specifically, for example, by using an atomic force microscope, the surface height (Zji) can be measured for an arbitrary region, and Rrms can be calculated by equation (1). Preferably, measurement is performed for a plurality of regions, and the average value is applied.

  In order to form the lead frame 1 having such a small mean square roughness Rrms of the surface, it is only necessary to reduce the unevenness of the underlying surface so as to have the same degree of Rrms. However, it is difficult to make the substrate 11 have such a smooth surface. As described above, the substrate 11 is manufactured by forming a rolled plate made of copper or a copper alloy. The oxide film formed on the rolled surface or the oxide embedded by rolling after the oxide film is dropped. In order to remove this, a polishing process after rolling is essential. Since the polishing marks remain on the surface by this step, the surface of the substrate 11 becomes rough, and the Rrms becomes 60 to 100 nm. As described above, the outermost metal oxide film 15 is extremely thin and is formed by physical vapor deposition, so that the surface shape of the base is maintained. Accordingly, the Ag plating film 13 or the underlying Ni plating film 12 fills the unevenness of the surface of the substrate 11 to smooth the underlying surface on which the metal oxide film 15 is formed, that is, the Ag plating film 13 surface. Specifically, as the thickness of the Ag plating film 13 or the Ni / Ag plating film 14 increases, the smoothing increases with respect to the surface roughness of the substrate 11 (the reduction amount of Rrms increases). Further, if the surface of the substrate 11 is previously etched with an acid using a mixed solution of strong acid mainly composed of nitric acid (Kirin's acid) or the unevenness of the surface of the substrate 11 is crushed by coining, Ag plating is performed. Even if the film 13 or the Ni / Ag plating film 14 is formed thin, smoothness can be obtained, which is more preferable.

  In addition, the smoother the surface of the Ag plating film 13 that is the base of the metal oxide film 15, the more difficult the pinholes are formed even in a thin film, so the effect of the Ag plating film 13 as a protective film is enhanced. In other words, when the surface of the Ag plating film 13 is rough, it is necessary to increase the thickness of the metal oxide film 15. As described above, the lead frame 1 according to the present embodiment forms the Ag plating film 13 that substantially matches the surface roughness so that the root mean square roughness Rrms is 30 nm or less in order to improve the light extraction efficiency. However, by setting the Ag plating film 13 to such a surface roughness, if the thickness of the metal oxide film 15 is 0.5 nm or more, pinholes are hardly formed.

[Lead frame manufacturing method]
The lead frame according to the present invention is not particularly limited as long as it can form the above-described configuration, and may be manufactured by any method. For example, the lead frame 1 shown in FIG. 1A includes a substrate manufacturing step S1 for manufacturing the substrate 11, an Ag plating step S3 for forming an Ag plating film 13 on the substrate 11, and a metal oxide film on the surface of the Ag plating film 13. 15 can be manufactured by a method including a metal oxide film forming step S4 for forming the semiconductor layer 15. Moreover, the lead frame 1B shown in FIG.1 (b) can be manufactured by the method which further performs Ni plating process S2 which forms the Ni plating film 12 in the board | substrate 11 before Ag plating process S3 (illustration omitted). . In addition, a code | symbol is attached | subjected for description to each process. Below, an example of the manufacturing method of the lead frame 1B is demonstrated.

(Substrate manufacturing process)
In the substrate manufacturing step S1, a copper or copper alloy material is continuously cast to produce a cast plate (for example, a thin plate ingot), and then annealing, cold rolling, intermediate annealing and aging treatment, and finish rolling, A base plate having a required thickness is manufactured through a process such as polishing. The base plate 11 can be obtained by forming the base plate into a required shape by press working or the like.

(Ni plating process)
When forming the Ni plating film 12, it is preferable to pre-treat the substrate 11 with a degreasing solution, electrolytic degreasing, and an acid solution in advance. For example, after the substrate 11 is immersed in a degreasing solution and degreased, the counter electrode is made of stainless steel 304, and a DC voltage is applied so that the lead frame side is negative, and electrolytic degreasing is performed for about 30 seconds. It can be performed by immersing in a 10% sulfuric acid aqueous solution for about 10 seconds.

The Ni plating film 12 is formed using, for example, a known plating bath such as a watt bath, a wood bath, a sulfamic acid bath, a Ni plate as a counter electrode, a current density of 5 A / dm ² , a plating bath temperature of 50 ° C., etc. Can be performed by electroplating. Moreover, it can also be set as a gloss Ni plating film using the plating bath which added the brightener. In this electroplating, the Ni plating film 12 having a desired film thickness can be obtained by adjusting the current density, plating plate speed (plating time), and the like. Further, when the Ni plating film 12 is formed only on one side (upper surface) of the substrate 11 or only in a part of the region, masking is performed with a masking tape or the like on the lower surface or other region, and then electroplating is performed in a plating bath. Thus, the Ni plating film 12 can be formed only on a desired portion of the substrate 11.

(Ag plating process)
As the Ag plating film 13, for example, a known plating bath such as a cyan bath or a thiosulfate bath is used, with an Ag (purity 99.99%) plate as a counter electrode, a current density of 5 A / dm ² , a plating bath temperature of 15 ° C., etc. A film can be formed by performing electroplating under the conditions described above. Moreover, it can also be set as a gloss Ag plating film using the plating bath which added the brightener. In this electroplating, the Ag plating film 13 having a desired film thickness can be obtained by adjusting the current density, the plating threading speed (plating time), etc., as in the Ni plating step S2. In addition, when the Ag plating step S3 is performed after the Ni plating step S2, the substrate 11 after the Ni plating film 12 is formed (Ni plating) in the Ni plating step S2 is lifted from the plating bath and washed with water. It is preferable to carry out continuously without drying. Therefore, when masking is performed in the Ni plating step S <b> 2, the Ag plating film 13 is formed in the same region as the region where the Ni plating film 12 is formed on the substrate 11, that is, the entire surface of the Ni plating film 12.

  When the lead frame 1 is manufactured, it is preferable to perform the same pretreatment on the substrate 11 as the Ni plating step S2 in order to form the Ag plating film 13 directly on the substrate 11 without performing the Ni plating step S2. Further, when the Ag plating film 13 is formed only on one surface (upper surface) of the substrate 11 or only in a part of the region, masking is performed with a masking tape or the like on the lower surface or the region other than that, and then electroplating is performed in a plating bath. Thus, the Ag plating film 13 can be formed only on a desired portion of the substrate 11.

(Metal oxide film formation process)
In the metal oxide film forming step S4, the metal oxide film 15 is formed on the surface of the Ag plating film 13 by using a sputtering method. In order to improve the adhesion between the Ag plating film 13 and the metal oxide film 15, before the film formation. In addition, dirt existing on the surface of the Ag plating film 13 may be removed by irradiating the Ag plating film 13 with an Ar ion beam or applying a high frequency in an Ar atmosphere. First, a metal oxide target whose composition is adjusted according to the composition of the metal oxide film 15 to be deposited is placed on the electrode of the sputtering apparatus, and the substrate 11 on which the Ag plating film 13 is formed is placed in the chamber of the sputtering apparatus. To do. Next, after evacuating the chamber to a pressure of 1.3 × 10 ⁻³ Pa or less, Ar gas is introduced into the chamber, and the pressure in the chamber is set to a predetermined pressure, for example, about 2 × 10 ⁻² Pa. adjust. Then, a predetermined discharge voltage is applied to the ion gun to generate Ar ions, and a predetermined acceleration voltage and beam voltage are further applied to irradiate the Ag plating film 13 with the Ar ion beam. After that, while introducing Ar gas into the chamber, the pressure in the chamber is adjusted to about 0.27 Pa, and sputtering is performed by applying a DC voltage (output 100 W) to the metal oxide target, so that the metal oxide film 15 Is deposited. In the case of this method, the metal oxide film 15 has a thickness exceeding 2 nm so that pinholes are not formed.

  As another example of the metal oxide film forming step S4, a metal film (or alloy film) is formed on the Ag plating film 13 using a target as a non-oxide metal (alloy) material, and then the metal film is oxidized. A method of forming the metal oxide film 15 will be described. The step of forming a film with a sputtering apparatus is the same as described above except that a metal (alloy) target whose composition is adjusted according to the metal component of the composition of the metal oxide film to be formed is placed on the electrode. After the metal film is formed, the chamber is opened or removed from the chamber and exposed to the atmosphere, whereby the metal film is oxidized and becomes the metal oxide film 15.

  As described above, the lead frame 1B can be manufactured by performing the steps S1, S2, S3, and S4 in this order. Further, the lead frame 1 can be manufactured by performing the steps S1, S3, and S4 in this order. Further, in the Ni plating step S2 and the Ag plating step S3, the Ag plating film 13 or the Ni / Ag plating film 14 is formed on the entire surface without masking the substrate 11 (11A), and in the metal oxide film forming step S4, one side ( When the metal oxide film 15 is formed only on the surface), the lead frames 1 and 1B shown in FIG. 4C can be manufactured. In addition, the Ni plating step S2 and the Ag plating step S3 or further the metal oxide film forming step S4 can be performed before forming in the substrate manufacturing step S1, and then processed into a desired shape.

[Light emitting device]
Next, an example of a light-emitting device incorporating the lead frame according to the present invention will be described. As described above, the light emitting device 10 is a general surface mount type light emitting device. As shown in FIGS. 2 and 3, in the light emitting device 10, the lead frame 1 (or the lead frame 1B) according to the present invention is formed as a pair of strip-like lead frames 1a and 1b, and a concave LED element mounting portion 22 is formed. The cup-shaped resin molded body 2 is supported. Specifically, each of the lead frames 1a and 1b penetrates from the outside of the resin molded body 2 to the inside of the LED element mounting portion 22, and the LED element mounting portion 22 with the surface on which the metal oxide film 15 is formed facing upward. Is disposed on the bottom surface. And LED element (it describes as "LED" in a figure) is adhere | attached on the lead frame 1a so that it may be mounted in the approximate center in the bottom face of the LED element mounting part 22. FIG. The electrodes of the LED elements are connected to the pair of lead frames 1a and 1b (inner lead parts) in the LED element mounting part 22 by bonding wires (wires). Further, the LED element mounting portion 22 is sealed by being filled with a transparent sealing resin (not shown).

  Such a light emitting device 10 is manufactured by forming the resin molded body 2 so that the lead frame 1 (1a, 1b) penetrates, and then mounting and sealing the LED element. Hereinafter, an example of a method for manufacturing the light emitting device 10 by incorporating the lead frame 1 according to the present invention will be described.

  The resin molded body 2 is formed by molding a resin that is an insulating material. Therefore, the resin molded body 2 is integrated with the lead frames 1a and 1b by injection molding (insert molding) or the like so that the lead frames 1a and 1b penetrate from the outer side to the inner side (LED element mounting portion 22). It is preferable to be molded. The resin has only to have heat resistance of 200 ° C. or higher, and engineering plastics such as polyamide (PA) resin, super engineering plastics such as polyphenylene sulfide (PPS) resin, and the like can be used.

  LED elements are mounted on the lead frames 1a and 1b supported by the resin molded body 2. First, an adhesive (not shown) made of a silicone die bond material or the like is applied to the surface of the lead frame 1a (inner lead part) at the approximate center of the bottom surface of the LED element mounting part 22, and the LED element is adhered and mounted thereon. To do. Next, the electrode of the LED element is connected to the portion (inner lead portion) disposed on the bottom surface of the LED element mounting portion 22 of the lead frames 1a and 1b by wire bonding. And it seals by filling sealing resin, such as an epoxy resin, in the LED element mounting part 22, and it becomes the light-emitting device 10 which mounted the LED element as a light source. In the case of the lead frame 1A connected in plural by the substrate 11A shown in FIG. 4 (a), the resin molded body 2A is molded as shown in FIGS. 4 (b) and 4 (c). After the LED element is mounted and sealed to be manufactured into a light emitting device, it is used after being separated by a thick broken line.

  The lead frame 1 may be manufactured in, for example, a bullet-type light emitting device without forming the resin molded body 2 (not shown). In this case, the substrate 11 is formed into a cup shape by press forging a thick portion of a deformed strip (rolled plate having a different thickness in the rolling width direction), and the plate thickness is thin outside the cup shape. The part is made into a shape extending in a strip shape. Then, a Ni plating film 12, an Ag plating film 13, and a metal oxide film 15 are formed on the cup-shaped inner surface of the substrate 11 to form a lead frame. The cup-shaped inner surface serves as the inner lead portion of the lead frame 1a and the LED element mounting portion 22, and the strip-shaped portion serves as the outer lead portion. This is combined with a lead frame 1b (which may be composed only of the substrate 11) made of a separate member to form a set of lead frames. In such a lead frame, the LED element is mounted and mounted on a cup-shaped inner bottom surface, and the cup-shaped interior is filled with a sealing resin and sealed. By adopting such a structure, the lead frame 1 can be formed not only under the LED element but also on the side reflection surface.

  In the light emitting device obtained by using such a lead frame 1, the Ag plating film 13 is unlikely to cause aggregation or discoloration of Ag due to heat, and is further coated with the metal oxide film 15, thereby allowing halogen ions, sulfur, etc. Therefore, the light emitted from the LED element is stably reflected and taken out as light from the light emitting device. Furthermore, since the Ag plating film 13 does not cause precipitation of Ag nanoparticles and does not discolor a sealing resin such as an epoxy resin, the light emitted from the LED element can be used with high efficiency. . Moreover, since the surface (reflective surface) of the lead frame 1 can regularly reflect most of the light emitted from the LED element and suppress the diffuse reflection, the brightness of the light emitting device equipped with the LED element can be improved.

  Hereinafter, the present invention will be described in more detail by way of examples of the present invention, but the present invention is not limited to the following examples.

[Sample preparation]
In the following manner, samples of the lead frames 1 and 1B having the laminated structure shown in FIGS. 1A and 1B are obtained from the Ni plating film thickness, the Ag plating film thickness, and the metal oxide film components and The film thickness was changed.

(Production of substrate)
A Cu-Fe-P copper alloy plate (KLF194H, manufactured by Kobe Steel, Ltd.) having a thickness of 0.1 mm was pressed to produce a substrate (substrate 11A) having the shape shown in FIG. . The root mean square roughness Rrms of the surface of this substrate was measured by the method described later to be 70 nm.

(Plating pretreatment)
The substrate was immersed in a degreasing solution as a pretreatment for plating, and the counter electrode was made of stainless steel 304. A DC voltage was applied so that the substrate side was negative, and electrolytic degreasing was performed for 30 seconds. Immersion for 10 seconds.

(Formation of Ni plating film)
The surface (entire surface) of the substrate after the pretreatment was subjected to bright Ni plating at a current density of 5 A / dm ² with a watt bath with the following components and a liquid temperature of 50 ° C., with a current density of 5 A / dm ² , and shown in Table 1. A Ni plating film having a film thickness was formed, pulled up from the Ni plating bath, and washed with water.
Ni plating bath component Ni sulfate: 250 g / L
Ni chloride: 40 g / L
Boric acid: 35 g / L
Additive A: 3 ml / L
Additive B: 10 ml / L

  The film thickness of the Ni plating film was controlled by adjusting the plating time based on the plating speed. That is, the dummy substrate is plated for a certain period of time under the same conditions as described above, and the adhesion amount of Ni is determined by measuring the weight difference between the dummy substrate and the plating, and this adhesion amount is determined as the plating area, the theoretical density of Ni, Further, the Ni plating film thickness (plating speed) deposited per unit time was calculated by dividing by the plating time, and the plating time for forming a desired film thickness was calculated from the plating speed.

(Formation of Ag plating film)
An Ag plating film having the thickness and composition shown in Table 1 was formed by the following method on the substrate after the pretreatment or the substrate on which the Ni plating film was formed.

An Ag plating film having a composition of Ag (pure Ag) is a cyan bath having the following components and a liquid temperature of 50 ° C., a counter electrode is an Ag (purity 99.99%) plate, current density is 5 A / dm ² , and gloss Ag Plating was applied. The film thickness of the Ag plating film was controlled by adjusting the plating time based on the Ag plating rate calculated by plating on the dummy substrate, similarly to the film thickness of the Ni plating film.
Ag plating bath component Silver potassium cyanide (I): 50 g / L
Potassium cyanide: 40 g / L
Potassium carbonate: 35 g / L
Additive C: 3 ml / L

An Ag plating film having a composition of Ag-0.2 at% Bi alloy is an Ag-Bi alloy plating bath with a liquid temperature of 25 ° C. and a Bi concentration of 100 mg / L. The counter electrode is a Pt plate and the current density is 3 A / dm. ^In Step ² , Ag—Bi alloy plating was performed. The film thickness of the Ag-Bi alloy plating film is obtained by plating the dummy substrate for a certain period of time under the same conditions as described above, measuring the film thickness of the plating film by cross-sectional SEM observation, calculating the plating speed, and calculating the desired plating speed. The plating time for forming the film thickness was calculated. Further, in order to analyze the composition of the Ag plating film, a plating film was formed under the same conditions as described above using stainless steel 304 as a dummy substrate. The plating film is peeled off from the dummy substrate and dissolved in nitric acid, and then the dissolved nitric acid solution is analyzed using an ICP (inductively coupled plasma) emission spectroscopic analyzer (ICPS-8000, manufactured by Shimadzu Corporation) to obtain a composition. Asked.

(Metal oxide film formation)
A metal oxide film was formed on the substrate plated with Ag by the following method. The substrate on which the Ag plating film or the Ni / Ag plating film was formed was placed in the chamber of a sputtering apparatus provided with a metal target (diameter 10.16 cm (4 inches φ) × thickness 5 mm) for the metal oxide film shown in Table 1. Arranged. Next, the chamber was evacuated with a vacuum pump so that the pressure in the chamber was 1.3 × 10 ⁻³ Pa or less, and Ar gas was introduced into the chamber to adjust the pressure in the chamber to 0.27 Pa. In this state, a DC voltage (output 100 W) is applied to the metal target for sputtering, and a metal film is formed on the Ag plating film by changing the film thickness. As a metal oxide film, the lead frame 1 sample was produced.

[Measurement and evaluation]
With respect to the obtained lead frame sample, the thickness of the metal oxide film was measured by the following method, and the root mean square roughness Rrms of the surface (the surface on which the metal oxide film was formed, the same applies hereinafter) was measured. Moreover, the regular reflectance of the surface was measured and heat resistance and sulfidation resistance were evaluated. The results are shown in Table 1.

(Measurement of metal oxide film thickness)
The thickness of the metal oxide film was measured by performing X-ray photoelectron spectroscopy (XPS). Using the fully automated X-ray photoelectron spectrometer (Physical Electronics Quantera SXM) on the surface of the sample, the concentrations of metal element, oxygen element O, and Ag contained in the metal oxide film shown in Table 1 were determined. Measured from the surface in the depth direction. Measurement conditions were as follows: X-ray source: monochromatic Al—Kα, X-ray output: 43.7 W, X-ray beam diameter: 200 μm, photoelectron extraction angle: 45 °, Ar ⁺ sputtering rate: about 0.6 nm / in terms of SiO ₂ Minutes. The depth at which the concentration of the metal element contained in the metal oxide film was reduced to ½ of the maximum concentration was taken as the film thickness of the metal oxide film.

(Measurement of root mean square roughness)
Using an atomic force microscope (AFM) (SPI-4000, manufactured by SII), the root mean square roughness Rrms of any three regions was measured. The measurement conditions were: deflection amount: -1.0, I gain: 0.2, P gain: 0.1, scanning area: 10 μm × 10 μm, and scanning frequency: 1 Hz. The average value was calculated from the measured values obtained at the three locations.

(Measurement of regular reflectance)
Using an automatic absolute reflectance measurement system (manufactured by JASCO Corporation), the specular reflectance is obtained by measuring the spectral reflectance up to a wavelength of 250 to 850 nm under the conditions of an incident angle of 5 ° and a reflection angle of 5 °. 70% or more was accepted.

(Heat resistance evaluation)
As a heat resistance test, the sample was heated in a thermostatic bath at 150 ° C. for 6 hours and subsequently heated at 260 ° C. for 5 minutes. After the test, the regular reflectance of the surface was measured by the same method as described above, and a test piece with a decrease in regular reflectance by a heat resistance test of less than 5 points was accepted.

(Sulfuration resistance evaluation)
As a sulfidation resistance test, a sample was exposed for 96 hours in a chamber adjusted to a hydrogen sulfide concentration of 3 ppm, a temperature of 40 ° C., and a humidity of 80%. After the test, the regular reflectance was measured in the same manner as described above, and a test in which the decrease in regular reflectance by the sulfidation resistance test was less than 20 points was accepted.

  As shown in Table 1, sample no. 1 to 12, since the thickness of the Ag plating film is within the range of the present invention, the root mean square roughness of the surface is sufficiently small, and the component and film thickness of the metal oxide film are within the range of the present invention. High reflectivity and excellent heat resistance and sulfidation resistance. In particular, since the deterioration due to the sulfidation resistance test was suppressed, it was confirmed that the metal oxide film had a sufficient barrier property to the Ag plating film. Sample No. No. 4, even if the Ag plating film is thin, the Ni plating film is provided as the base, so that the Ag (pure Ag) plating film and the metal (Ta) oxide film have the same thickness without providing the Ni plating film. Sample No. Compared with 1, the heat resistance was improved.

  In contrast, sample no. No. 17 had a high initial reflectivity due to the formation of a sufficiently thick Ni / Ag plating film, but since the metal oxide film was not formed on the surface, the Ag plating film deteriorated due to the heat resistance test and the sulfidation resistance test. The reflectivity deteriorated remarkably. Sample No. In Nos. 14 and 15, the metal oxide film was insufficient in thickness, and a sufficient effect as a protective film could not be obtained. In particular, sample no. No. 14 was presumed that a pinhole was formed because the Ni plating film was not formed and the film thickness of the Ag plating film was insufficient, so that the base surface was rough and the thin metal oxide film was formed. The durability was further lowered than 15. Similarly, sample no. No. 13, although the thickness of the metal oxide film was within the range of the present invention, it was presumed that a pinhole was generated because the base surface was rough, and a sufficient effect as a protective film could not be obtained. Sample No. In Nos. 13 and 14, since the Ni plating film was not formed and the film thickness of the Ag plating film was insufficient, Cu of the substrate diffused and oxidized on the surface by the heat resistance test, the surface was discolored and the reflectance was deteriorated. . On the other hand, sample No. In No. 16, the initial reflectance decreased because the metal oxide film was excessive.

  Sample No. No. 18 formed a Sn oxide film which is not a metal oxide film of the present invention. However, when the Sn film is formed to a thickness of 2 nm, Sn aggregates and disperses in an island shape regardless of the surface roughness of the base. Therefore, even after oxidation in the atmosphere, a smooth film was not formed. For this reason, the Sn oxide film has a large surface mean square roughness and low initial reflectance, and further, the Ag plating film is not completely covered as a continuous film, and the effect as a protective film cannot be obtained.

1,1A, 1B Lead frame (LED lead frame)
11, 11A Substrate 12 Ni plating film 13 Ag plating film 14 Ni / Ag plating film 15 Metal oxide film

Claims (2)

A substrate made of copper or a copper alloy, and an Ag plating film having a thickness of 0.6 μm or more and 8 μm or less formed on at least one side of the substrate,
Further, a metal oxide film of one kind of metal selected from V , Cr, Zr, Nb, Mo, Hf, Ta, and W or an alloy composed of two or more kinds is formed on the Ag plating film with a thickness of 0. It is formed to be 5 nm or more and 15 nm or less,
An LED lead frame, wherein the surface having the metal oxide film has a root mean square roughness of 30 nm or less. A substrate made of copper or a copper alloy, a Ni plating film having a thickness of 0.5 μm or more formed on at least one side of the substrate, and an Ag plating having a thickness of 0.2 μm or more formed on the Ni plating film A total film thickness of the Ni plating film and the Ag plating film is 8 μm or less,
Further, a metal oxide film of one kind of metal selected from V , Cr, Zr, Nb, Mo, Hf, Ta, and W or an alloy composed of two or more kinds is formed on the Ag plating film with a thickness of 0. It is formed to be 5 nm or more and 15 nm or less,
An LED lead frame, wherein the surface having the metal oxide film has a root mean square roughness of 30 nm or less.

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