JP2014072247A - Substrate of lead frame for high reflectivity optical semiconductor device having long term reliability, lead frame for optical semiconductor device using the same and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate of a lead frame for optical semiconductor device combining high reflectivity from near-ultraviolet to visible light range and excellent corrosion resistance, and ensuring excellent workability and productivity, and to provide a lead frame for optical semiconductor device using the same, and manufacturing methods therefor.SOLUTION: In a substrate of a lead frame for optical semiconductor device having a surface plating layer 2 composed of silver or a silver alloy on the surface of a conductive base material 1, the surface plating layer 2 has a thickness of 0.5-10 μm, and at least one kind of fine particles 8 of aluminum oxide or barium sulfate is contained 1-10% by volume ratio in the surface plating layer 2. In the particle size distribution of the fine particles 8, median diameter Rof the fine particles 8 is 0.05-1 μm, and the fine particles 8 are exposed and/or stuck onto the surface of the surface plating layer 2, so that the projection area of particles will be 15-30% for the surface area of the surface plating layer 2 in the area ratio.

Description

  The present invention relates to a lead frame base for an optical semiconductor device, a lead frame for an optical semiconductor device using the same, and a manufacturing method thereof.

  An optical semiconductor device lead frame is widely used as a constituent member of various display / illumination light sources using light emitting elements, which are optical semiconductor elements such as LED (Light Emitting Diode) elements, as light sources. In this optical semiconductor device, for example, a lead frame is arranged on a substrate, and after the light emitting element is mounted on the lead frame, the deterioration of the light emitting element and its peripheral parts due to external factors such as heat, moisture, and oxidation are prevented. The light emitting element and its periphery are sealed with resin.

  By the way, when the LED element is used as an illumination light source, the reflective material of the lead frame has a high reflectance in the entire visible light wavelength range (for example, 400 to 800 nm) (for example, the reflectance with respect to a reference material such as barium sulfate or aluminum oxide). Is 80% or more).

  In response to such a demand, a layer (film) made of silver or a silver alloy is formed on the lead frame on which the LED element is mounted, particularly for the purpose of improving the light reflectance in the visible light region (hereinafter referred to as reflectance). ) Is often formed. It is known that the silver film has a high reflectance in the visible light region, and a silver plating layer is formed on the reflection surface (Patent Document 1), or after formation of the silver or silver alloy film, at 200 ° C. or more for 30 seconds or more. It is known that the reflectance in the visible light region can be further increased by performing heat treatment so that the crystal grain size of the film is 0.5 μm to 30 μm (Patent Document 2). In addition, the applicant performs plastic working after forming the silver or silver alloy film, and makes the plating film made of silver or silver alloy a plastically deformed structure (Patent Document 3), so that the near ultraviolet region (wavelength of 340 to 400 nm). ) Suggests that the reflectance in the visible light region can be made higher.

  Thus, the silver or silver alloy film has good reflectivity in the visible light region or reflectivity from the near ultraviolet region to the visible light region, but has poor sulfidation resistance, and the surface is sulfided when used for a long period of time. There is a problem that the reflectance from the near ultraviolet region to the visible light region is lowered.

  As a countermeasure, there is a method (Patent Document 4) for forming a corrosion-resistant film on a silver or silver alloy film. However, this method has problems such as a decrease in reflectance in the visible light region and a complicated manufacturing process.

  As another countermeasure, a method of improving the reflectance of silver or silver alloy film and imparting corrosion resistance by dispersing (eutectoid) particles having high reflectance and corrosion resistance in silver or silver alloy film. (Patent Document 5). However, in this method, when the amount of particles dispersed in the silver or silver alloy film increases, there arises a problem that the workability of the film is lowered. In addition, when distributing particles near the surface of the silver or silver alloy film that contributes to the reflectance of visible light, the same amount of particles as those near the surface are dispersed inside the film that does not contribute to the reflectance. As a result, productivity is low.

Japanese Patent Laid-Open No. 61-148883 Japanese Patent No. 4367457 JP 2012-28757 A JP 2012-9542 A JP 2011-222603 A

  The present invention disperses fine particles having high reflectance and good corrosion resistance in the surface and the surface of the surface plating layer made of silver or a silver alloy, and by controlling the distribution state within a predetermined range, Provided is a lead frame substrate for an optical semiconductor device that has high reflectivity and good corrosion resistance in the near ultraviolet region to visible light region, and has good workability and productivity, and an optical semiconductor device lead frame using the same. This is the issue. Another object of the present invention is to provide a lead frame substrate for an optical semiconductor device and a method for manufacturing a lead frame for an optical semiconductor device using the same.

The object of the present invention is achieved by the following means.
(1) A lead frame substrate for an optical semiconductor device having a surface plating layer made of silver or a silver alloy on the surface of a conductive substrate,
The surface plating layer has a thickness of 0.5 to 10 μm,
1 to 10% by volume of at least one fine particle of aluminum oxide or barium sulfate in the surface plating layer,
In the particle size distribution of the fine particles, the median diameter _{R m} of the fine particles is 0.05 to 1 [mu] m,
The fine particles are exposed and / or adhered on the surface of the surface plating layer so that the projected area of the particles is 15 to 30% in terms of the area ratio with respect to the surface area of the surface plating layer. A lead frame substrate for an optical semiconductor device.
(2) The lead frame substrate for an optical semiconductor device according to the item (1), wherein 90% or more of the fine particles have a particle size of R _m ± 0.25 μm.
(3) The lead frame substrate for an optical semiconductor device according to (1) or (2), wherein the conductive substrate is made of copper, copper alloy, iron, iron alloy, aluminum, or aluminum alloy. .
(4) Any one of (1) to (3) having at least one intermediate layer made of nickel, nickel alloy, cobalt, cobalt alloy, copper or copper alloy between the conductive substrate and the surface plating layer 2. A lead frame substrate for an optical semiconductor device according to item 1.
(5) A lead frame for an optical semiconductor device comprising the substrate for a lead frame for an optical semiconductor device according to any one of (1) to (4).
(6) Disperse at least one fine particle of aluminum oxide or barium sulfate having a median diameter R _{m of} 0.05 to 1 μm in a silver or silver alloy plating solution,
Plating the surface of the conductive substrate with the plating solution to form a surface plating layer to a thickness of 0.5 to 10 μm,
The lead frame for an optical semiconductor device according to any one of (1) to (4), which includes each step of adjusting the amount of the fine particles exposed and / or attached on the surface plating layer in this order. A method for manufacturing a substrate.
(7) Disperse at least one fine particle of aluminum oxide or barium sulfate having a median diameter R _{m of} 0.05 to 1 μm in a silver or silver alloy plating solution,
Plating the surface of the conductive substrate with the plating solution to form a surface plating layer to a thickness of 0.5 to 10 μm,
Adjusting the amount of the fine particles exposed and / or adhered on the surface plating layer;
The method for manufacturing a lead frame for an optical semiconductor device according to the item (5), which includes the steps of forming and processing into a predetermined shape in this order.

According to the present invention, fine particles having high reflectivity and good corrosion resistance are dispersed inside and on the surface plating layer made of silver or a silver alloy, and the distribution state is appropriately controlled, so that the visible state can be seen from the near ultraviolet region. It is possible to obtain a lead frame substrate for an optical semiconductor device having both high reflectivity and corrosion resistance in the optical region, and good workability and productivity.
Since it has such characteristics, the lead frame substrate for optical semiconductor devices obtained by the present invention is suitable as a material for lead frames for optical semiconductor devices, for example.

It is sectional drawing of one Embodiment of the base | substrate for lead frames for optical semiconductor devices of this invention. It is sectional drawing of another one Embodiment of the base | substrate for lead frames for optical semiconductor devices of this invention. It is a schematic sectional drawing of 1st Embodiment of the lead frame for optical semiconductor devices of this invention. It is a schematic sectional drawing of 2nd Embodiment of the lead frame for optical semiconductor devices of this invention. It is a schematic sectional drawing of 3rd Embodiment of the lead frame for optical semiconductor devices of this invention. It is a schematic sectional drawing of 4th Embodiment of the lead frame for optical semiconductor devices of this invention. It is a schematic sectional drawing of 5th Embodiment of the lead frame for optical semiconductor devices of this invention. It is a schematic sectional drawing of 6th Embodiment of the lead frame for optical semiconductor devices of this invention.

  Embodiments of a lead frame substrate for optical semiconductor devices according to the present invention will be described below with reference to the drawings. Each embodiment is merely an example, and the scope of the present invention is not limited to each embodiment. In addition, the illustrated form schematically shows the configuration necessary for the description, and the ratio of the size of each layer or fine particle and the size of each layer is not limited to the illustrated one.

  One preferred embodiment of the substrate for a lead frame for optical semiconductor devices of the present invention has a surface plating layer (reflective layer) 2 on a conductive substrate 1 as shown in the schematic sectional view of FIG. The fine particles 8 (8a, 8b, 8c) having a high reflectance and good corrosion resistance are dispersed in a predetermined dispersion state in and on the surface plating layer 2. In another preferred embodiment of the lead frame substrate for an optical semiconductor device of the present invention, as shown in the schematic sectional view of FIG. 2, at least one layer is provided between the conductive substrate 1 and the surface plating layer 2. An underplating layer (intermediate layer) 4 may be provided. In FIG. 2, only the fine particles 8a and 8c are shown for convenience, but the fine particles 8b shown in FIG.

  The lead frame substrate for an optical semiconductor device controls the distribution of fine particles 8 dispersed in and on the surface plating layer 2 to increase the amount of fine particles exposed and / or adhered and dispersed on the surface. As a result, the effect of the fine particles 8 can be efficiently obtained in the vicinity of the surface of the surface plating layer 2 as compared with the case where the fine particles are uniformly dispersed inside and on the surface of the surface plating layer 2, and the optical semiconductor device lead. The processability and productivity of the frame substrate can also be improved.

  The conductive substrate 1 is preferably made of, for example, copper, iron, aluminum, or at least one alloy thereof. These composite clad materials may also be used. By using these metal substrates or alloy substrates, it is possible to provide a lead frame substrate for an optical semiconductor device that has good reflectance characteristics, can easily form a surface plating film, and has high productivity. In addition, a lead frame using a lead frame substrate for an optical semiconductor device based on these metals has excellent heat dissipation characteristics, and heat energy generated when the light emitter emits light is transmitted through the lead frame. Since the light can be emitted smoothly to the outside, the lifetime of the light-emitting element and the long-term reflectance characteristics are expected to be stabilized. This depends on the conductivity of the base material IACS (International Annealed Copper Standard). The conductivity of the substrate is preferably at least 10% IACS or more, and more preferably 50% IACS or more. Even if the base material changes, the reflectivity depends on the surface state of the reflective layer. Therefore, the reflectivity does not change greatly, and the heat dissipation and the physical characteristics of the base material change mainly.

  Between the conductive substrate 1 and the surface plating layer 2, at least one base plating layer (intermediate layer) 4 may be formed. The undercoat layer 4 is preferably made of nickel, cobalt, copper, or at least one alloy thereof. For example, when an iron-based base material is used, the heat conductivity of the material is relatively low, so that the heat dissipation can be improved without impairing the reflectance by applying copper and a copper alloy layer to the base plating. . Furthermore, since the copper plating contributes to the improvement of plating adhesion, it is possible to prevent deterioration of adhesion due to heat generation when the light emitting element emits light. In the case of using copper and a copper alloy base material, nickel, cobalt, or at least one of them is used as the base plating layer 4 in order to suppress diffusion of the base material component to the surface plating layer due to heat generated when the light emitting element emits light. It is effective to apply a seed alloy layer.

  The thickness of the base plating layer 4 is not particularly limited, but is preferably 0.2 to 2 μm. If the thickness is less than 0.2 μm, the effect of preventing thermal diffusion of the base material component to the surface layer side may not be sufficiently exhibited. On the other hand, if the thickness is larger than 2 μm, the effect of preventing thermal diffusion is saturated, and there is a risk of processing cracks during molding.

  The surface plating layer 2 is preferably made of silver or a silver alloy. Silver or silver alloy has good reflectivity, conductivity and thermal conductivity from the near ultraviolet to visible light range, and relatively good corrosion resistance, so surface plating used for lead frame substrates for optical semiconductor devices Suitable as a layer. The silver or silver alloy forming the surface plating layer in the lead frame substrate for optical semiconductor devices of the present invention may be silver, silver-tin alloy, silver-indium alloy, silver-rhodium alloy, silver-ruthenium alloy, silver-gold. A material selected from the group consisting of alloys, silver-palladium alloys, silver-nickel alloys, silver-selenium alloys, silver-antimony alloys, and silver-platinum alloys can be used. By using these silver or silver alloys, a lead frame with good reflectance and good productivity can be obtained.

  However, when a silver alloy is used for the surface plating layer 2, it may be difficult to make the reflectance in the visible light region higher than 90%. Therefore, silver is particularly preferable for the surface plating layer, and its purity is It is preferable that it is 99 mass% or more.

  The thickness of the surface plating layer 2 is 0.5 to 10 μm, and preferably 1 to 5 μm. When the surface plating layer is too thin, the base material component easily diffuses to the surface, and the long-term reliability of the plating material may be reduced. On the other hand, if it is too thick, the improvement in long-term reliability of the lead frame substrate for optical semiconductor devices cannot be expected any more, and the use of precious metal more than necessary reduces the productivity and increases the production cost.

  It is desirable that the fine particles 8 dispersed in and on the surface plating layer 2 have a higher reflectance from the near ultraviolet region to the visible light region than silver and are chemically stable. As such a material, aluminum oxide, barium sulfate, or the like is preferable. Since the intrinsic reflectance of the fine particles is reduced due to the presence of impurities, the impurities contained in the fine particles are preferably 5% by mass or less.

  The fine particles 8 are dispersed in the surface plating layer 2 in a volume ratio of 1 to 10%, preferably 3 to 8%. Under production conditions where too few fine particles are dispersed in the surface plating layer, the amount of fine particles exposed and / or adhered and dispersed on the surface is reduced, and the reflectance of visible light from the near ultraviolet region on the surface of the lead frame substrate for optical semiconductor devices is reduced. The improvement of corrosion resistance cannot be expected. If the amount is too large, the workability when processing the lead frame substrate for optical semiconductor devices may be reduced, and it exists inside the surface plating layer, contributing to the reflectance and corrosion resistance of visible light from the near ultraviolet region. As a result, the amount of fine particles that are not increased increases, so that productivity is reduced.

  The fine particles 8 are exposed and / or attached to the surface of the surface plating layer 2 so that the projected area of the particles is 15 to 30%, preferably 20 to 25% in terms of the surface area of the surface plating layer. If there are too few fine particles exposed and / or attached to the surface of the surface plating layer, it is not possible to improve the reflectance and corrosion resistance of visible light from the near ultraviolet region on the surface of the surface plating layer. On the other hand, if the amount is too large, the wire bonding property on the surface of the surface plating layer is lowered, and the reliability of the lead frame for an optical semiconductor device manufactured using the lead frame substrate for an optical semiconductor device may be lowered.

Here, the state where the fine particles are exposed means that a part of the fine particles embedded in the surface plating layer is exposed from the surface of the surface plating layer as shown by the fine particles 8a in FIGS. It means that it is in a state.
On the other hand, the state in which the fine particles are attached means that the fine particles are not embedded in the surface plating layer and are attached on the surface plating layer as shown by the fine particles 8b in FIG. To do. Adhesion is physical adhesion with the surface plating layer by intermolecular force of fine particles. As described above, although not shown in FIG. 2, also in the embodiment of FIG. 2, fine particles 8b may exist together with the fine particles 8a or instead of the fine particles 8a.

On the surface of the surface plating layer, there are fine particles attached in this way and exposed fine particles. In the present invention, fine particles on the surface of the surface plating layer may be constituted only by adhesion, or may be constituted only by exposure. Of course, the present invention may be configured such that particles exposed on the surface and particles adhering to the surface coexist.
In addition to these exposed or adhered fine particles, in the present invention, as shown by fine particles 8c in FIGS. 1 and 2, the state in which the fine particles are entirely embedded and dispersed in the surface plating layer is a predetermined dispersion. Always present in proportion.

In the present invention, the aluminum oxide, the particle size distribution of at least one of the fine particles of barium sulfate, or fluorine resin, a median diameter R _m of the fine particles made to be 0.05 to 1 [mu] m, preferably, 0. 3 to 0.7 μm. When the average particle diameter of the fine particles is too small, the fine particles are aggregated in the plating bath when manufacturing the lead frame substrate for an optical semiconductor device, and the fine particles cannot be dispersed in the surface plating layer. On the other hand, if it is too large, the workability of the lead frame substrate for optical semiconductor devices is degraded. In the present invention, by using fine particles satisfying the predetermined particle size distribution, the effect of these particle sizes can be obtained favorably on average.
The particle size distribution of the fine particles can be appropriately adjusted by the method described later.

Furthermore, in the present invention, it is preferable that 90% or more of the fine particles have a particle size of R _m ± 0.25 μm. That is, it is preferable that 90% or more of the individual fine particles in the entire fine particles have a particle size r (μm) that falls within the range of R _m −0.25 ≦ r ≦ R _m +0.25. Adjusting the particle size to such a range is preferable in terms of “there is a small number of particles that do not contribute to the improvement of reflectivity and particles that contribute to a decrease in processability, so that both reflectivity and processability can be achieved”. . In addition, if the particle size falling within this range is less than 90%, “the number of particles that do not contribute to the improvement in reflectivity and the particles that contribute to the decrease in processability increases, so that both reflectivity and processability can be achieved. It is not preferable because “it disappears”.

  The fine particles 8 can be dispersed inside and on the surface plating layer 2 by immersing the conductive substrate 1 in a plating solution in which fine particles are dispersed and performing electroplating or electroless plating. The amount of fine particles dispersed in the surface plating layer can be adjusted by the fine particle concentration in the plating solution, the current density during plating, and the stirring strength.

  In dispersing the fine particles 8 in and on the surface plating layer 2, a surfactant may be used. The surfactant is not particularly limited, and may be cationic, anionic, nonionic, amphoteric, etc., as long as the fine particles 8 can be dispersed in the plating solution and dispersed inside and on the surface plating layer 2. Any surfactant may be used.

  The dispersion amount of the fine particles 8 adhered and / or exposed and dispersed on the surface of the surface plating layer 2 can be controlled by providing a fine particle amount adjustment step after plating, such as cleaning, grinding, and surface treatment. In an ordinary lead frame substrate, after plating, fine particles adhering to and / or exposed and dispersed on the surface of the surface plating layer are removed by washing or the like. However, in the present invention, the fine particle amount adjusting step is performed to control the amount of fine particles 8 to adjust the fine particle amount in the vicinity of the surface of the lead frame substrate for optical semiconductor devices. As a result, it is possible to obtain a lead frame substrate for an optical semiconductor device that has good reflectivity and corrosion resistance from the near ultraviolet region to the visible light region, and has both workability and productivity.

  For example, when the fine particle amount adjusting step is performed by washing with water, the washing time and washing strength (flow rate, water pressure, etc.) are adjusted. Moreover, when it is desired to increase the amount of dispersion due to adhesion and / or exposure of fine particles to the surface of the surface plating layer 2, a technique such as electrophoresis can be used. In this manner, the dispersion amount of the fine particles 8 adhered and / or exposed and dispersed on the surface of the surface plating layer 2 is adjusted.

Next, in the present invention, the particle size distribution of the fine particles 8 can be adjusted as follows.
(1) Classification is performed by wet classification such as classification / filtration, centrifugal separation, hydrocyclone, etc. of commercially available fine particles.
・ Classify by dry classification such as cyclone and shaking.
(2) Pulverization of fine-particle commercial products by wet pulverization such as bead mill.
・ Crush by dry fine grinding such as dry bead mill.
(3) Use / mixing of commercially available fine particles, fine particles having a predetermined particle size distribution may be used as they are, or two or more thereof may be mixed and used.
In the present invention, the particle size distribution of the fine particles 8 can be measured by particle size distribution measurement using a laser diffraction method, a dynamic light scattering method, an ultrasonic method, or the like.

  The above-mentioned lead frame substrate for optical semiconductor devices has good reflectivity and corrosion resistance from the near ultraviolet region to the visible light region, and has both good workability and productivity. Can be suitably used.

  Embodiments of a lead frame for optical semiconductor devices according to the present invention will be described below with reference to the drawings. Each figure shows a state in which an optical semiconductor element is mounted on a lead frame. Each embodiment is merely an example, and the scope of the present invention is not limited to each embodiment. In addition, the illustrated form is omitted to the extent necessary for the description, and the dimensions and the specific lead frame or element structure are not construed as being limited to the illustrated one. 3 to 8, the fine particles 8 (8a, 8b, 8c) are not shown.

  FIG. 3 is a schematic cross-sectional view of the first embodiment of the lead frame for an optical semiconductor device according to the present invention. In the lead frame of this embodiment, the surface plating layer 2 made of silver or a silver alloy is formed on both surfaces of the conductive substrate 1, and the optical semiconductor element 3 is mounted on a part of the surface plating layer 2. ing. Furthermore, the other lead frame and the optical semiconductor element 3 insulated by the bonding wire 7 at a broken portion (abbreviated as a broken line-shaped region in the drawing) are electrically connected to form a circuit. Has been. In the present invention, the lead frame of the present embodiment disperses the fine particles 8 having a high reflectance from the near ultraviolet region to the visible light region and having good corrosion resistance on the inside and the surface of the surface plating layer 2, thereby enabling the near ultraviolet region. In addition, the lead frame for an optical semiconductor device has excellent reflection characteristics in the visible light region (wavelength of 340 nm to 800 nm) and good corrosion resistance.

  FIG. 4 is a schematic cross-sectional view of a second embodiment of the lead frame for an optical semiconductor device according to the present invention. The lead frame of the embodiment shown in FIG. 4 is different from the lead frame shown in FIG. 3 in that a base plating layer 4 is formed between the conductive substrate 1 and the surface plating layer 2. Other points are the same as those of the lead frame shown in FIG.

  FIG. 5 and FIG. 6 show surface plating in which fine particles 8 having good reflectivity in the near ultraviolet region to visible light region and good corrosion resistance are dispersed inside and on only one surface on which the optical semiconductor element is mounted. FIG. 7 is a schematic cross-sectional view of the third and fourth embodiments in which a layer 2 is disposed, and the difference between FIG. 5 and FIG. 6 is the presence or absence of a base plating layer 4.

  FIG. 7 is a schematic sectional view of a fifth embodiment of a lead frame for an optical semiconductor device according to the present invention. FIG. 7 shows a state in which the optical semiconductor module is formed by the mold resin 5 and the sealing resin 6 for convenience, and a part where the optical semiconductor element 3 is mounted and a part that causes a reflection phenomenon in the vicinity thereof. And the surface plating layer 2 is formed only inside the mold resin 5. In the present embodiment, the base plating layer 4 is formed on the entire surface of the conductive substrate 1, but is partially formed as long as it is interposed between the conductive substrate 1 and the surface plating layer 2. It may be. Further, the surface plating layer 2 is formed up to the middle of the lower part of the mold resin 5, but it is only necessary to cover a region that is a part contributing to the reflection phenomenon, and only to the outside of the mold resin 5 or only inside the mold resin. It may be covered. In the present invention, it is also possible to form the surface plating layer 2 made of silver or a silver alloy only in a portion that contributes to light reflection.

  FIG. 8 is a schematic cross-sectional view of a sixth embodiment of a lead frame for optical semiconductor devices according to the present invention. FIG. 8 shows a state in which the optical semiconductor module is formed of the mold resin 5 and the sealing resin 6 for convenience, as in FIG. The embodiment of FIG. 8 differs from FIG. 7 in that the base plating layer 4 is provided only on the surface of the conductive substrate 1 on which the optical semiconductor element 3 is disposed, and that the surface plating layer 2 is a conductive group. It is provided on the entire surface of the material 1.

  Hereinafter, although the present invention is explained still in detail based on an example, the present invention is not limited to this.

The conductive base material shown in Table 1 below was plated with the following silver or silver alloy plating solution in which fine particles of aluminum oxide or barium sulfate were dispersed. The fine particles made of aluminum oxide or barium sulfate were dispersed in a predetermined dispersion amount inside and on the surface plating layer made of silver or silver alloy provided by this plating treatment. By providing the surface plating layer in this way, a lead frame substrate for an optical semiconductor device was produced by the following method. Furthermore, the lead frame for an optical semiconductor device can be obtained by punching the base body into a predetermined shape.
Table 1 shows the amount of fine particles dispersed inside the surface plating layer and the exposure and / or adhesion dispersion amount of fine particles on the surface of the surface plating layer (total dispersion amount of exposed fine particles and adhering fine particles). In Table 1, the amount of fine particles dispersed inside the surface plating layer is the amount of internal dispersion of fine particles, and the amount of fine particles exposed and / or attached dispersion on the surface of the surface plated layer (the total amount of dispersion described above) is the amount of fine particles attached to the surface. , Each abbreviated.

  Among the materials used as the conductive substrate, “C14410 (Cu-0.15Sn: Furukawa Electric Co., Ltd., trade name: EFTEC-3)”, “C18045 (Cu—Cr—Sn—Zn-based alloy material: Cu-0.3Cr-0.25Sn-0.5Zn: manufactured by Furukawa Electric Co., Ltd., trade name EFTEC-64T), "C19400 (Cu-Fe based alloy material: Cu-2.3Fe-0.03P-) 0.15Zn) "," C26800 (brass: Cu-35Zn) "," C52100 (phosphor bronze: Cu-8Sn-0.03P) ", and" C77000 (Yellow: Cu-18Ni-27Zn) "are copper or This represents a copper alloy substrate, and the numerical value after C indicates the type according to the CDA (Copper Development Association) standard. “A2014” represents a base material of aluminum or an aluminum alloy, and its component is defined in Japanese Industrial Standards (JIS H 4000: 2006, etc.). “42 Alloy” represents an iron-based base material, which contains 42% by mass of nickel, and the balance of iron and inevitable impurities.

  A conductive substrate having a thickness of 0.25 mm and a width of 180 mm is subjected to a degreasing treatment and a pickling treatment as plating pretreatment, followed by a silver strike plating treatment and a surface plating layer formation, followed by a washing and drying process. A substrate for a lead frame for a semiconductor device was produced. Moreover, the sample which performed the 1 micrometer base metal-plating layer formation between the pickling process and the silver strike plating process was also produced. When the base material was “A2014”, a zinc substitution process was performed between the pickling process and the formation of the base plating layer.

As described in Table 1, the plating solution for forming the surface plating layer was used after dispersing aluminum oxide fine particles or barium sulfate fine particles having a median particle diameter of 0.05 μm to 1.0 μm. Both aluminum oxide and barium sulfate are those manufactured by Kanto Chemical Co., Ltd., and by combining grinding with a bead mill, classification by filtration, and mixing, fine particles having a particle size distribution of 90% or more in advance are R _m ± 0. After adjusting to 25 μm, it was dispersed in the plating solution. The particle size distribution of the fine particles was determined by using Spectris Co., Ltd. for the dispersion liquid in which the fine particles were dispersed in water or in a surfactant (EA-150 (trade name), manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) solution. ) Measured by a dynamic light scattering method (DLS analysis) using Zeta Sizer Nano ZS (trade name) manufactured by Malvern Division.

(Pretreatment conditions)
[Electrolytic degreasing]
Degreasing solution: NaOH 60 g / liter Degreasing conditions: Current density 2.5 A / dm ² , temperature 60 ° C., degreasing time 60 seconds [pickling treatment]
Pickling solution: 10% by mass sulfuric acid pickling condition: room temperature, 30 seconds immersion [zinc replacement treatment]
Zinc replacement solution: NaOH 500 g / liter, ZnO 100 g / liter, tartaric acid (C ₄ H ₆ O ₆ ) 10 g / liter, FeCl _{2 2} g / liter Treatment conditions: Room temperature, immersion for 30 seconds [silver strike plating treatment]
Plating solution: KAg (CN) ₂ 4.45 g / liter, KCN 60 g / liter Plating condition: current density 5 A / dm ² , temperature 25 ° C.

(Under plating conditions)
[Nickel plating]
Plating _{solution: Ni (SO 3 NH 2)} 2 · 4H 2 O 500g / l, NiCl ₂ 30 g / _l, H ₃ BO ₃ 30g / l Plating Conditions: current density 5A / dm ^2, temperature 50 ° C.
[Cobalt plating]
Plating _{solution: Co (SO 3 NH 2)} 2 · 4H 2 O 500g / l, CoCl ₂ 30 g / _l, H ₃ BO ₃ 30g / l Plating Conditions: current density 5A / dm ^2, temperature 50 ° C.
[Copper plating]
Plating solution: CuSO ₄ .5H ₂ O 250 g / liter, H ₂ SO ₄ 50 g / liter, NaCl 0.1 g / liter Plating condition: current density 6 A / dm ² , temperature 40 ° C.

(Surface plating conditions)
[Silver plating]
Plating solution: AgCN 50 g / liter, KCN 100 g / liter, K ₂ CO ₃ 30 g / liter, aluminum oxide fine particles or barium sulfate fine particles 1 to 100 g / liter Plating conditions: current density 1 A / dm ² , temperature 30 ° C.
[Ag-Sn alloy plating]
Plating solution: KCN 100 g / liter, NaOH 50 g / liter, AgCN 10 g / liter, K ₂ Sn (OH) ₆ 80 g / liter, aluminum oxide fine particles or barium sulfate fine particles 1 to 100 g / liter Plating conditions: current density 1 A / dm ² 、 Temperature 40 ℃
[Ag-In alloy plating]
Plating solution: KCN 100 g / liter, NaOH 50 g / liter, AgCN 10 g / liter, InCl ₃ 20 g / liter, aluminum oxide fine particles or barium sulfate fine particles 1 to 100 g / liter Plating conditions: current density 2 A / dm ² , temperature 30 ° C.
[Ag-Pd alloy plating]
Plating solution: KAg [CN] ₂ 20 g / liter, PdCl ₂ 25 g / liter, K ₄ O ₇ P ₂ 60 g / liter, KSCN 150 g / liter, aluminum oxide fine particles or barium sulfate fine particles 1 to 100 g / liter Density 0.5A / dm ² , temperature 40 ° C
[Ag-Se alloy plating]
Plating solution: KCN 150 g / liter, K ₂ CO ₃ 15 g / liter, KAg [CN] ₂ 75 g / liter, Na ₂ O ₃ Se5H ₂ O 5 g / liter, aluminum oxide fine particles or barium sulfate fine particles 1 to 100 g / liter Conditions: current density 2 A / dm ² , temperature 50 ° C.
[Ag-Sb alloy plating]
Plating solution: KCN 150 g / liter, K ₂ CO ₃ 15 g / liter, KAg [CN] ₂ 75 g / liter, C ₄ H ₄ KOSb 10 g / liter, aluminum oxide fine particles or barium sulfate fine particles 1 to 100 g / liter Current density 1A / dm ² , temperature 50 ° C

Measurement of internal dispersion of fine particles:
The cross section of the lead frame substrate for an optical semiconductor device was directly observed with an electron microscope (magnification 10,000 times), and the internal dispersion amount of the fine particles was measured from the observed image.

Measurement of the amount of fine particles attached to the surface:
The surface of the lead frame substrate for an optical semiconductor device was directly observed with an electron microscope (magnification 10,000 times), and the total amount of dispersion that was exposed and / or adhered to the surface of the fine particles was measured from the observed image.

Measurement of particle size distribution:
The above-mentioned fine particles whose particle size distribution is adjusted are dispersed in water or an aqueous solution of a surfactant EA-150 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Using Zetasizer Nano ZS (trade name) manufactured by Malvern Division, measurement was performed by a dynamic light scattering method (DLS analysis).

  The following evaluation was performed about the Example and comparative example of Table 1. The results are shown in Table 2.

Reflectance measurement:
Using a spectrophotometer U-4100 (trade name, manufactured by Hitachi High-Technologies Corporation), total reflectance was continuously measured in a wavelength range of 300 nm to 800 nm. Among these, Table 2 shows the total reflectance (%) in the ultraviolet region to the near ultraviolet region of 340 nm, 375 nm, and 400 nm, and further in the visible light region of 450 nm and 600 nm. It is required that the reflectance at a wavelength of 340 nm is 60% or more, the reflectance at 375 nm is 75% or more, the reflectance at 400 nm is 80% or more, and 90% or more at wavelengths of 450 nm and 600 nm in the visible light region. Characteristic.

Sulfurization test (described in JIS H8502):
Corrosion state of H ₂ S 3 ppm, 24 hours later, was carried out the rating number (RN) evaluation. Here, when the rating number is 9 or more, it means that the decrease in luminance is as small as several percent even if the optical semiconductor element (LED element) is lit for 10,000 hours, and it has good corrosion resistance and long-term performance. Shows high reliability. On the other hand, when the rating number is less than 9, it was determined that the corrosion resistance is insufficient.

Wire bonding property (WB property):
Under the following wire bonding conditions, the bonding strength was measured after the 10-point test.
Wire bonder: SWB-FA-CUB-10 (trade name, manufactured by Shinkawa Co., Ltd.)
Wire: 25 μm Gold Wire bonding temperature: 150 ° C.
Capillary: 1820-17-437GM
1st condition: 10msec, 45Bit, 45g
2nd condition: 10 msec, 100 bits, 130 g
When the value of (strength-3σ) is 49.0 mN or more, “Excellent” is indicated as “◎”, and when 29.4 mN or more and less than 49.0 mN is indicated as “Good”, “◯” is indicated, and less than 29.4 mN However, those that could be joined were indicated as “△” as “possible”, and “X” was indicated as “impossible” when they were not joined at all. Among these, the evaluation of ◎ ○ △ was judged to be a practical pass level, and the × was judged to be a fail level. Here, σ represents the standard deviation of the intensity of 10-point measurement.

Bending workability:
A test piece having a length of 30 mm and a width of 10 mm was cut out from the produced lead frame substrate for an optical semiconductor device so that the length direction was parallel to the rolling direction, and bent by a press machine (manufactured by Nippon Automatic Machine Co., Ltd.). The bending workability when bending at a radius R = 0.5 mm was examined. The maximum bending portion of the bent test piece was observed using a microscope (manufactured by Keyence Co., Ltd.) at a magnification of 175 to determine the bending workability. As a result of observing the maximum bending part, “Good” indicates that there is no crack, “Good” indicates that there is a crack, and “No” indicates that there is a wrinkle or minor crack, and there is a large crack. A thing was shown as "x" as "impossible". Among these, the evaluation of ◯ △ was judged to be a practical pass level, and the evaluation of × was judged to be a fail level.

As shown in Table 2, the optical semiconductor device lead frame substrate and the optical semiconductor device lead frame of the present example all have reflectivity, corrosion resistance, wire bonding property, bending processing from the near ultraviolet region to the visible light region. The property was good.
In contrast, the comparative example was inferior to any one or more characteristics. In Comparative Example 1 in which the fine particles were not dispersed inside and on the surface plating layer, the reflectance and corrosion resistance at wavelengths of 375 nm, 400 nm, and 450 nm were inferior. In Comparative Examples 2 and 6 in which the particle size of the fine particles was too large and Comparative Examples 3 and 7 in which the amount of fine particle dispersion in the surface plating layer was too large, bending workability was inferior. In Comparative Examples 4 and 8, in which the fine particle exposure and / or adhesion dispersion amount on the surface plating layer surface was too small, the reflectance at wavelengths of 375 nm and 450 nm was inferior, and the corrosion resistance was insufficient. In Comparative Examples 5 and 9 in which the fine particle exposure and / or adhesion dispersion amount on the surface plating layer was too large, the wire bonding property was inferior.

DESCRIPTION OF SYMBOLS 1 Conductive base material 2 Surface plating layer 3 Optical semiconductor element 4 Base plating layer 5 Mold resin 6 Sealing resin 7 Bonding wire 8 Fine particle 8a Fine particle adhering to the surface of the surface plating layer 8b Fine particle exposed on the surface of the surface plating layer 8c Fine particles embedded and dispersed in the surface plating layer

Claims (7)

A lead frame substrate for an optical semiconductor device having a surface plating layer made of silver or a silver alloy on the surface of a conductive substrate,
The surface plating layer has a thickness of 0.5 to 10 μm,
1 to 10% by volume of at least one fine particle of aluminum oxide or barium sulfate in the surface plating layer,
In the particle size distribution of the fine particles, the median diameter _{R m} of the fine particles is 0.05 to 1 [mu] m,
The fine particles are exposed and / or adhered on the surface of the surface plating layer so that the projected area of the particles is 15 to 30% in terms of the area ratio with respect to the surface area of the surface plating layer. A lead frame substrate for an optical semiconductor device. 2. The lead frame substrate for an optical semiconductor device according to claim 1, wherein 90% or more of the fine particles have a particle size of Rm ± 0.25 [mu] _m .   The lead frame substrate for an optical semiconductor device according to claim 1, wherein the conductive substrate is made of copper, copper alloy, iron, iron alloy, aluminum, or aluminum alloy.   The at least one intermediate | middle layer which consists of nickel, a nickel alloy, cobalt, a cobalt alloy, copper, or a copper alloy between the said electroconductive base material and the said surface plating layer is described in any one of Claims 1-3. Lead frame substrate for optical semiconductor devices.   The lead frame for optical semiconductor devices which consists of the base | substrate for lead frames for optical semiconductor devices of any one of Claims 1-4. Dispersing at least one fine particle of aluminum oxide or barium sulfate having a median diameter R _{m of} 0.05 to 1 μm in a silver or silver alloy plating solution,
Plating the surface of the conductive substrate with the plating solution to form a surface plating layer to a thickness of 0.5 to 10 μm,
5. The lead frame substrate for an optical semiconductor device according to claim 1, further comprising, in this order, steps for adjusting the amount of the fine particles exposed and / or attached on the surface plating layer. 6. Production method. Dispersing at least one fine particle of aluminum oxide or barium sulfate having a median diameter R _{m of} 0.05 to 1 μm in a silver or silver alloy plating solution,
Plating the surface of the conductive substrate with the plating solution to form a surface plating layer to a thickness of 0.5 to 10 μm,
Adjusting the amount of the fine particles exposed and / or adhered on the surface plating layer;
The method for manufacturing a lead frame for an optical semiconductor device according to claim 5, comprising the steps of forming and processing into a predetermined shape in this order.