JP5839861B2 - Optical semiconductor device lead frame, optical semiconductor device lead frame manufacturing method, and optical semiconductor device - Google Patents

Description

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

  2. Description of the Related Art Lead frames for optical semiconductor devices are widely used as constituent members of various display / illumination light sources that use light emitting elements, which are optical semiconductor elements such as LED (Light Emitting Diode) elements, as light sources. In the 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. Specifically, a silver plating layer is formed on the reflection surface (Patent Document 1), or 200 or after the silver or silver alloy film is formed. It is known that a heat treatment is performed at a temperature of 30 ° C. or more for 30 seconds or more, and the crystal grain size of the coating is 0.5 μm to 30 μm (Patent Document 2). Also, electrical contact materials for springs that have been heat-treated after rolling after silver plating are known, and the bonding strength between plated crystal grains is enhanced by rolling to improve wear resistance. Is known (Patent Document 3).

Japanese Patent Laid-Open No. 61-148883 Japanese Patent No. 4367457 Japanese Patent No. 3515226

  When silver or an alloy film thereof is simply formed by a known technique such as Patent Document 1, the reflectivity at a wavelength of 400 nm to 800 nm is 75% or more, and particularly 450 nm is about 85% (conventional example 1 described later). Was 85%). However, the reflectance required for the recent optical semiconductor devices, particularly LED lead frames, is still about several tens of percent of the light emission efficiency of the chip. A level (for example, 90% or more at a wavelength of 450 nm or more) has been demanded.

  Therefore, as in Patent Document 2, the reflectance of the visible light region is improved by setting the crystal grain size of the silver or silver alloy film to 0.5 μm to 30 μm on the surface of the base material having a surface roughness of 0.5 μm or more. An invention that has been raised to 90% or more has been disclosed, and methods such as the provision of plating thickness, roughness, and heat treatment to keep the crystal grain size within a specified range have been taken. However, when this method is used, since the material is subjected to heat treatment, there is a concern that the reflectance will decrease due to the progress of oxidation of the silver surface. In some cases, the deterioration and wire bonding properties are deteriorated. Furthermore, although it is adapted to the LED mounting base in Patent Document 2, the heat dissipation becomes a problem due to the recent appearance of high-power LEDs and the like. Therefore, it is speculated that it can be developed into a type using a copper or copper alloy lead frame with good heat dissipation, but if heat treatment is performed, the copper component of the base material diffuses to the silver surface, reducing the reflectance. Therefore, it was found that it was difficult to easily deploy the lead frame. For this reason, the present situation is that no lead frame having a better reflectivity than the conventional silver coating has been developed.

As a result of intensive studies, the present inventors have found that a crystal grain boundary formed by plating forms an absorption peak at the wavelength. Attempts were made to extinguish the absorption peak by reducing the crystal grain boundaries or by narrowing the gaps between the grain boundaries so that light is not absorbed.
In order to solve this problem, Patent Document 2 adopts a technique in which the crystal grain of silver plating is coarsened by a heat treatment after plating, the gap between the crystal grains is reduced, and as a result, the reflectance is increased. doing. However, even if the crystal grains are coarsened by heat treatment, for example, when considering a region where three or more crystal grains are close to each other, the gaps between the crystal grains are not necessarily completely eliminated or the gaps are narrowed. I can't do that. Therefore, when a product using such a heat-treated material is used, the base material or the base plating, which is the base material, is generated through the gap between the plated silver crystal grains due to the heat generated by the light emission of the light emitting element. It is thought that the layer is oxidized in contact with external air, and the oxidation of the plated silver is promoted to cause plating peeling. Further, if the crystal grains become coarser on the surface side, the roughness on the surface increases, and therefore it is conceivable that the reflectance is deteriorated by being affected by the larger surface roughness.

Therefore, the present invention is a lead frame for optical semiconductor devices used for LEDs, photocouplers, photointerrupters, etc., which has a higher reflectance than the conventional silver coating as a whole in the visible light region (wavelength 400 to 800 nm), In particular, an object of the present invention is to provide a lead frame that has good reflectivity when mounted on a chip that emits light in the vicinity of a wavelength of 450 nm, has high luminance, and excellent heat dissipation, and a method for manufacturing the same. In particular , after a heat treatment in the atmosphere at 150 ° C. for 3 hours after a heat treatment in the atmosphere at 150 ° C. for 3 hours at a wavelength of 400 to 800 nm in the visible light region , the reflectivity drop is within 5%. news at wavelengths above 450nm and aims to provide a lead frame of more than 90% reflectivity and a manufacturing method thereof.

  As a result of conducting sincerity studies in view of the above problems, in a lead frame for an optical semiconductor device in which a reflective layer made of silver is formed on the outermost surface of a conductive substrate by a plating method, plating is performed by performing plastic processing after forming the plating layer. By reducing the area ratio of the remaining plating structure to 50% or less without crushing the structure, the heat treatment is not performed and the crystal grain size is not controlled, and the reflectance in the visible light wavelength range of 400 to 800 nm is achieved. Has been found to be 85% or more and 90% or more at a wavelength of 450 to 800 nm, and the present invention has been made based on this finding.

That is, the said subject is solved by the following means.
(1) An optical semiconductor device lead frame comprising a reflective layer on at least one surface or both surfaces of the outermost surface of the conductive substrate, and a part or the entire surface of the conductive substrate, wherein the reflective layer emits at least an optical semiconductor element. in the outermost surface of the region that reflects light, at least the surface of the plating structure of silver is weave rolling plastic deformation sets of higher working rate of 22%, in at least the surface, the area ratio of plating tissue remaining rate of silver is 50% or less, reflectivity at a wavelength of 400 to 800 nm is 85% or more, and heat resistance is less than 5% when the heat treatment is performed in the atmosphere at 150 ° C. for 3 hours in the air at a wavelength of 450 nm. A lead frame for an optical semiconductor device.
(2) The lead frame for optical semiconductor devices according to (1), wherein the conductive substrate is made of copper, copper alloy, iron, iron alloy, aluminum, or aluminum alloy.
(3) The lead frame for an optical semiconductor device according to (1) or (2), wherein the thickness of the reflective layer after plastic deformation is 0.2 to 10 μm.
(4) The base body includes n metal layers (n is an integer of 1 or more) thereon, and the reflective layer is provided on the base body directly or via at least one of the metal layers. The lead frame for optical semiconductor devices according to any one of (1) to (3), wherein the lead frame is for optical semiconductor devices.
(5) A method of manufacturing a lead frame for a semiconductor device according to any one of (1) to (4), wherein light emitted from at least an optical semiconductor element is an outermost surface on a conductive substrate. After forming a reflective layer made of silver in the reflective region by plating, and further subjecting the reflective layer to plastic working to cause plastic deformation in the plated structure of the reflective layer, the plastic working method is the processing rate. wherein the rolling der Rukoto 22% or more, a manufacturing method of a lead frame for an optical semiconductor device.
(6 ) It comprises an optical semiconductor element and the lead frame for an optical semiconductor device according to any one of (1) to (4) provided at least at a place where the optical semiconductor element is mounted. An optical semiconductor device.

According to the present invention, after a silver reflective layer is formed on the outermost surface of the conductive substrate by plating, the reflective layer is further subjected to plastic working so that at least the surface of the plated structure has a processing rate of 22% or more. A wavelength in the visible light region when the area ratio (hereinafter referred to as plating structure residual ratio) of a shape having a plastic deformation rolling structure ( shape ) and similar to the plating structure shape remaining on the surface is 50% or less. The reflectance of 400 to 800 nm can be increased to 85% or more, and further, the reflectance can be increased to 90% or more at a wavelength of 450 nm or more. In addition, it has an excellent effect in improving the reflectance in the near ultraviolet region. In addition, by using a lead frame, heat dissipation is superior to direct formation on a circuit on a mounting substrate, and deterioration of the optical semiconductor device due to heat can be delayed.
Further, plastic working method is state of the request can be easily accomplished by performing a rolling pressure Engineering working ratio 22% or more after plating. That is, according to the present invention, the reflectance is generally higher than that of a conventional silver film at a wavelength of 400 to 800 nm that is in the visible light region, and particularly when the optical semiconductor chip that emits light near the wavelength of 450 nm is mounted, the reflectance is good. A lead frame having high luminance and excellent heat dissipation and a method for manufacturing the same can be provided.

1 is a schematic cross-sectional view of a first embodiment of a lead frame for an optical semiconductor device according to the present invention. It is a schematic sectional drawing of 2nd Embodiment of the lead frame for optical semiconductor devices which concerns on this invention. It is a schematic sectional drawing of 3rd Embodiment of the lead frame for optical semiconductor devices which concerns on this invention. It is a schematic sectional drawing of 4th Embodiment of the lead frame for optical semiconductor devices which concerns on this invention.

In the lead frame of the present invention, after a reflective layer made of silver is formed by a plating method such as electroplating, the reflective layer is further subjected to plastic working to form a plated structure made of silver (a metal structure formed by a plating method). ) Is at least plastically deformed on the surface. By causing plastic deformation in the plating layer, the bonding force of the grain boundaries of the crystal formed by plating is strengthened and dislocations are discharged. At the same time, silver is recrystallized by the energy of plastic processing, and at the same time, surface irregularities are formed. Smoothing can be achieved with a mechanically acting force. As a result, the reflectance of a wavelength of 400 to 800 nm can be improved, so that it is suitably used particularly for an optical semiconductor device on which an optical semiconductor light emitting chip having a wavelength of 450 nm to 800 nm is mounted. Among optical semiconductor devices, it is particularly effective for LEDs. In addition, it has an excellent effect in improving the reflectance in the near ultraviolet region.
Hereinafter, preferred embodiments of the present invention will be described in detail.

  Here, the plating structure remaining ratio not subjected to plastic working needs to be 50% or less, preferably 30% or less, of the region in the portion used as the reflective layer. Here, the plating structure residual rate typically means that a plating structure (a needle-like structure or a precipitated state of spherical particles) is formed over almost the entire area when a silver plating layer is formed by a plating method such as electroplating. On the other hand, even when plastic working is performed and plastic deformation occurs and the plating structure disappears, the area of the shape similar to the remaining plating structure remains when the shape similar to the plating structure remains on the subsequent surface Ratio [area of shape similar to remaining plating structure / area of measurement target area] (%). The lower this ratio, the better the reflection characteristics can be obtained, and it can be applied as a LED lead frame with higher brightness. In addition, as a result of plastic working, the plating structure or a shape similar thereto may not remain at all, so the lower limit value of the plating structure remaining rate is 0%. In the present invention, the plating structure remaining rate is preferably closer to 0%, and from the viewpoint of improving the reflectance, the plating structure remaining rate is most preferably 0%. Here, the “location used as the reflective layer” means that the LED module is formed by resin molding other than the light emitting portion when forming the LED module, but the lead frame when the LED chip emits light. It shows the part where the light reflection phenomenon occurs at the exposed part. That is, it is preferable that the plating structure remaining rate at the exposed portion of the lead frame that contributes to the reflection phenomenon is 50% or less, and the plating structure remaining rate of 50% or less on the entire surface is naturally good. Processing may be performed so that the plating structure remaining rate of the portion is 50% or less, and only that region becomes a portion used as a reflective layer of the LED.

The plating method may be a wet plating method such as an electroplating method or an electroless plating method, or a dry plating method such as a sputtering method.
As the plastic working may be plastic working of the rolling machining. According to the rolling machining, the whole of the material, including the base body is subjected to plastic working, the whole of the plating structure is subjected to plastic deformation.

In the present invention, the electroplating method for an electroless plating method or a metal structure formed by the sputtering method (plating structure), by plastic working of the rolling machining, the reflective layer at least the surface is plastically deformed plating tissue It is characterized by having it on the outermost surface. Here, the plastically deformed metal structure is different from the cast structure as is metallurgically clear in the present technical field, and is also different from the plated structure before deformation formed by plating. Specifically, fine crystals are usually observed on the surface after plating, and a needle-like structure, a precipitated state of spherical particles, and the like are observed. On the other hand, the surface state after subjected to rolling pressure Engineering after plating, since the processing pattern is formed in the roll-th rolling rolls and has a surface texture such as that transferred to the lead frame side, for example, generic It is possible to distinguish clearly by performing surface observation with an SEM at an observation magnification of 2000 to 10000 times.

The production method according to the present invention will be described in detail. A plating method (for example, electroplating method, electroless plating method or sputtering method) is applied to part or all of both surfaces or one surface of a conductive substrate (for example, strip material). subjected to, to form a reflective layer made of silver is subjected to plastic working of the rolling machining. Next, the shape of the lead frame due to error etching method.
A chip mounting portion is formed on the lead frame by a resin mold or the like, and an optical semiconductor module is manufactured by mounting an optical semiconductor chip, wire bonding, and sealing with resin or glass containing a phosphor.
In the conventional method, generally, a conductive substrate (such as strip member) by e etching process after the shape of the lead frame is performed with silver plating or gold / palladium / nickel plating. Moreover, in the method of the said patent document 2, it attaches to predetermined heat processing after metal plating, and makes the particle size of a plating layer coarse.
The present invention and the conventional method are the ones in which the present invention is a modification of the plating structure as a mechanical processing finish, whereas the conventional method is a simple processing finish by cladding, plating finish or heat treatment finish, or The structure is completely different in that the heat treatment for plating and rolling is improved.

  The lead frame for an optical semiconductor device of the present embodiment has a good reflectance characteristic and is easy to form a film by making the base body copper or copper alloy, iron or iron alloy, or aluminum or aluminum alloy, Lead frames that can contribute to cost reduction can be provided. In addition, the lead frame based on these metals or alloys has excellent heat dissipation characteristics, and the heat energy generated when the light emitter emits light can be smoothly discharged to the outside through the lead frame, and light emission It is expected that the lifetime of the element will be prolonged and the reflectance characteristics will be stabilized over a long period. This depends on the conductivity IACS (International Annealed Copper Standard) of the substrate, preferably at least 10% or more, more preferably 50% or more. Even if these substrates change, the reflectivity depends on the surface state of the reflective layer, and thus the reflectivity does not change, and only the heat dissipation and the physical properties of the substrate change.

  The lead frame for an optical semiconductor device of this embodiment can ensure long-term reliability by setting the thickness of the reflective layer made of silver after plastic deformation to 0.2 μm or more. On the other hand, when the thickness is 10 μm or less, the cost can be reduced without using a precious metal more than necessary. This is because the effect of long-term reliability is that the thickness of the reflective layer is saturated at 10 μm. The effect is sufficiently expected if it is 0.2 to 10 μm, preferably 0.5 to 7 μm, more preferably 1 to 5 μm. This is because when the reflective layer coating thickness after plastic deformation made of silver is less than 0.2 μm, the copper component of the base material tends to diffuse to the surface, so that the outermost layer coating thickness of at least 0.2 μm or more is formed. It means that it is preferable. Actually, a material having the above lower limit value or more was produced, and it was confirmed that the heat resistance was increased as compared with a material having a value below this value.

As described above, the reflective layer on the surface made of a metal such as silver or a silver alloy or an alloy thereof may be formed by wet plating using an electroplating method or an electroless plating method, or alternatively, the metal may be formed by sputtering. Alternatively, the substrate surface may be formed by plating and precipitating. Here, the electroplating method has been described as a representative example. However, in the case of the electroless plating method or the sputtering method, a metal such as silver or a silver alloy is used in the same manner as in the case of the electroplating method. Alternatively, a layer made of the alloy can be formed. For example, in the case of the electroless plating method, it may be formed by using a commercially available bath (for example, S.D. Ag40; manufactured by Sasaki Chemical Co., Ltd.) or the like. Can be used.
The coating thickness (initial thickness) before processing for achieving the thickness after plastic processing is not particularly limited, but is preferably in the range of 1 to 50 μm, for example.
In addition, since it is difficult to ensure 90% at a wavelength of 400 to 800 nm when the reflective layer is made of a silver alloy, silver is preferably used for the reflective layer, and its purity is preferably 99% or more.

  The lead frame for an optical semiconductor device of the present embodiment has a metal selected from the group consisting of nickel, nickel alloy, cobalt, cobalt alloy, copper, and copper alloy between the conductive substrate and the reflective layer made of silver. An intermediate layer made of an alloy can be formed. 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. When copper and copper alloy base materials are used, a nickel, nickel alloy, cobalt, or cobalt alloy layer is applied to the underlayer in order to suppress diffusion of base material components to the reflective layer due to heat generated when the light emitting element emits light. It is effective. Although the thickness of these base plating is not limited, the range of 0.2-2.0 micrometers is preferable.

Lead frame for an optical semiconductor device of this embodiment, the construction method of plastic working Ru Oh rolling machining. Other plastic processing methods include forging and rolling, but are not suitable because it is difficult to form a smooth and uniform surface to be a reflective layer, and productivity is low and costs are high. is there. Although a method of applying the reflective layer and the plastic working at a time by laminating by the clad method is also conceivable, it is not suitable for suitably controlling the noble metal coating film thickness on the order of several μm. For this reason, electroplating is excellent from the viewpoint of productivity and cost as a manufacturing method in which the thickness is appropriately controlled on the order of micrometers to form the reflective layer.

In the present embodiment, when the plastic working in a method of manufacturing a lead frame for a semiconductor device is a rolling, there is the influence of the surface roughness after plating, for example, rolling rate is to plate thickness after plating, Ru der 22% or more. It is preferable to manufacture the lead frame for optical semiconductors in such a processing rate range so that the plating structure residual rate can be easily adjusted to a suitable range. When the rolling process rate is equal to or more than the above lower limit value, the plating structure remaining rate is less affected by the roughness of the rolling roll, so that the plating structure remaining rate is stably 50% or less without depending on the roll roughness. And the reflectance can be sufficiently increased. There is no particular upper limit for the rolling rate, but it must be determined after adjusting the strength, hardness, and conductivity required for the material. If the rolling rate is high, the power required for the rolling mill is high. Not only does it increase and the environmental impact increases, but cracks and cracks during bending work tend to occur, so the upper limit is practically about 80%.
The mechanical processing to a material in which a part or all of the conductive substrate is coated with silver can be performed, for example, by rolling using a cold rolling mill. The rolling machine includes a 2-stage roll, a 4-stage roll, a 6-stage roll, a 12-stage roll, a 20-stage roll, and the like, and any rolling machine can be used.
It should be noted that the rolling process may be repeated any number of times from the plate thickness after plating to the product plate thickness of the optical semiconductor lead frame. By setting the number of rolling times to several times, the probability that the rolling roll comes into contact with the plated structure is increased, and as a result, it is easy to reduce the remaining ratio of the plated structure. Even 5 times or less is preferable. Note that the rolling roll used for the rolling process has an arithmetic average (Ra) of surface roughness of less than 0.1 μm in consideration of improving the reflectance on the lead frame side formed by transferring the rolls. preferable.
“Processing rate” indicates a ratio represented by “(plate thickness before processing−plate thickness after processing) × 100 / (plate thickness before processing)”.

Furthermore, in order to control the mechanical properties required, the rolling machining (also referred to as temper or low-temperature annealing) method by heat treatment, such as a batch type or an inter-running type after the plastic working by the applied, as well as refining, Although the grain boundary spacing can be narrowed by strengthening the bonding force between the crystal grains at the crystal grain boundary, it is necessary to limit the heat treatment to a level that does not reduce the reflectance.
The conditions for the heat treatment performed after the plastic working such as rolling are not particularly limited, but for example, the heat treatment may be performed at a temperature of 50 to 150 ° C. for 0.08 to 3 hours. preferable. If the temperature of this heat treatment is too high or the time is too long, the heat history becomes excessive and the reflectance is lowered.

  In the optical semiconductor device of this embodiment, the reflectance characteristics can be effectively obtained at low cost by using the lead frame of the present invention at least at a place where the optical semiconductor element is mounted. This is because the reflectance characteristic is sufficiently effective by forming a reflective layer made of silver only on the mounting portion of the optical semiconductor element. In this case, the reflective layer made of silver may be partially formed. For example, the reflective layer may be formed by partial plating such as stripe plating or spot plating, and then formed by plastic working. Manufacturing a lead frame in which the reflective layer is partially formed can reduce the amount of metal used in a portion where the reflective layer is unnecessary, and thus can be an environment-friendly and low-cost optical semiconductor device.

  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.

  FIG. 1 is a schematic cross-sectional view of a first embodiment of a lead frame for an optical semiconductor device according to the present invention. In the lead frame of this embodiment, a reflective layer 2 made of silver is formed on a conductive substrate 1, an optical semiconductor element 3 is mounted on a part of the surface of the reflective layer 2, and further broken by a bonding wire 7. The other lead frame insulated by the portion 9 (abbreviated as a broken line-shaped region in the figure) and the optical semiconductor element 3 are electrically connected to form a circuit. In the lead frame of this embodiment, the reflective layer 2 is plastically deformed after being formed by electroplating, and the plating structure remaining rate is 50% or less. The present invention can provide a lead frame for an optical semiconductor device that has a reflectance of 85% or more at a wavelength of 400 to 800 nm in the visible light region, particularly a reflectance of 90% or more at a wavelength of 450 to 800 nm, and has excellent reflection characteristics.

  FIG. 2 is a schematic 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. 2 is different from the lead frame shown in FIG. 1 in that an intermediate layer 4 is formed between the conductive substrate 1 and the reflective layer 2. Other points are the same as those of the lead frame shown in FIG.

FIG. 3 is a schematic sectional view of a third embodiment of the lead frame for an optical semiconductor device according to the present invention. FIG. 3 shows a state in which the LED module is formed by the mold resin 5 and the sealing resin 6 for convenience, a portion where the optical semiconductor element 3 is mounted and a portion that causes a reflection phenomenon in the vicinity thereof, and The reflective layer 2 is formed only inside the mold resin 5. In the present invention, it is also possible to form the reflective layer 2 made of silver only in the vicinity of the portion contributing to light reflection. In the schematic cross-sectional view in the present embodiment, the reflective layer 2 is formed with a step on the surface layer of the conductive substrate 1, but part or all of the reflective layer 2 is buried inside the conductive substrate 1 by plastic processing. You may do it.
In the present embodiment, the intermediate layer 4 is formed on the entire surface of the conductive substrate 1, but may be partially formed as long as it is interposed between the conductive substrate 1 and the reflective layer 2. .

  FIG. 4 is a schematic cross-sectional view of a fourth embodiment of the lead frame for optical semiconductor devices according to the present invention. In FIG. 4, a reflective layer 2 made of silver is formed on one side of a lead frame. As in this embodiment, it is possible to form the optical semiconductor device by forming the reflective layer 2 only on one side of the lead frame.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to this.

As an example, the conductive substrate shown in Table 1 having a thickness of 0.25 mm and a width of 180 mm was subjected to the following pretreatment and then subjected to the following electroplating treatment. Thereafter, in order to plastically deform the Ag-plated layer, by changing the more working ratio in rolling machining Invention Example 1, 3～4,6～9,12 24, the lead frame in Comparative Example 1 and Reference Example 1 (Examples having no intermediate layer and comparative examples correspond to the structure of the lead frame shown in FIG. 1, and examples having an intermediate layer correspond to the structure of the lead frame shown in FIG. 2). Reference Example 2 imitates Comparative Example 1 of Patent Document 3, and Reference Example 3 imitates Example 2 of Patent Document 3, and after the rolling process, heat treatment is performed at 240 ° C. for 4 hours. We prepared the product (heat-treated product). Moreover, about the plating finishing goods of the prior art example 1, after performing the pretreatment shown below to the electroconductive base | substrate shown in Table 1 of plate | board thickness 0.25mm and width 180mm, the electroplating process shown below is given and rolled. A lead frame was produced without performing this. In Conventional Example 2, a lead frame was prepared by heat-treating the plating material obtained in Conventional Example 1 at 300 ° C. for 5 minutes in a nitrogen atmosphere with a residual oxygen concentration of 500 ppm or less. Prepared the adjusted one.
Among the materials used as the conductive substrate, “C18045 (EFTEC-64T, Cu—Cr—Sn—Zn alloy material: Cu—0.3Cr—0.25Sn—0.5Zn)”, “C19400 (Cu— Fe-based alloy material: Cu-2.3Fe-0.03P-0.15Zn "", "C26000 (brass: Cu-30Zn)", "C52100 (phosphor bronze: Cu-8Sn-P)", and "C77000 ( “White: Cu-18Ni-27Zn” ”represents a copper or copper alloy substrate, and the numerical value after C indicates the type according to the CDA (Copper Development Association) standard. “C18045 (EFTEC-64T)” is a copper alloy manufactured by Furukawa Electric Co., Ltd.
“A2014” represents an aluminum or aluminum alloy substrate, and its component is defined in Japanese Industrial Standards (JIS H 4000: 2006, etc.).
“42 Alloy” represents an iron-based substrate, containing 42% by mass of nickel, and the balance of iron and inevitable impurities.
In addition, when the substrate was “A2014”, a pretreatment was performed through electrolytic degreasing / pickling / zinc replacement, and other substrates were subjected to electrolytic degreasing / pickling.
Moreover, before performing each silver plating, silver strike plating was performed.

(Pretreatment conditions)
[Electrolytic degreasing]
Degreasing solution: NaOH 60 g / liter Degreasing conditions: 2.5 A / dm ² , temperature 60 ° C., degreasing time 60 seconds [pickling]
Pickling solution: 10% sulfuric acid pickling condition: 30 seconds immersion, room temperature [zinc replacement] Used when the substrate is aluminum 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: 30 seconds immersion, room temperature [Ag strike plating]
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)
[Ni 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 5 A / dm ^2, temperature 50 ° C.
[Co 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.
[Cu 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.

(Silver plating conditions)
[Ag plating]
Plating solution: AgCN 50 g / liter, KCN 100 g / liter, K ₂ CO ₃ 30 g / liter Plating condition: current density 1 A / dm ² , temperature 30 ° C.

(Evaluation method)
The lead frames of the invention examples, reference examples, and conventional examples obtained in the manner described above were evaluated according to the following tests and standards. The results are shown in Table 1. The conventional example is a comparative example corresponding to the prior art.
(1A) Reflectance measurement: In a spectrophotometer (V660 (trade name, manufactured by JASCO Corporation)), continuous measurement was performed with a total reflectance of 300 nm to 800 nm. Of these, the total reflectance (%) at 400 nm, 450 nm, 600 nm, and 800 nm is shown in Table 1. The required characteristics were that the reflectance at a wavelength of 400 nm was 85% or more and the reflectance at a wavelength of 450 nm to 800 nm was 90% or more.
(1B) Heat resistance: After the heat treatment in the atmosphere at a temperature of 150 ° C. for 3 hours, the reflectance measurement was performed. As a result, the total reflectivity at a wavelength of 450 nm did not change at all, “AA”, the reflectivity decrease was within 2%, “A”, the reflectivity decrease was over 2% and within 5% “B” is indicated as “B”, “C” is indicated when the reflectance drop exceeds 5%, and “B” or higher is shown in Table 1 as a practical level at which stable reflectance can be obtained with excellent heat resistance.

As is clear from these results, the inventive example has a better reflectance at 400 to 800 nm than the conventional example, and satisfies 85% or more at 400 nm and 90% or more at 450 to 800 nm. In particular, in the invention examples in which the plating structure residual ratio is 50% or less, the reflectance is 90% or more at a wavelength of 450 nm, and 95% or more is satisfied at a wavelength of 450 to 800 nm. It can be seen that an excellent reflectance is obtained. Moreover, it was confirmed that the reflectance is excellent even in the near ultraviolet region.
On the other hand, Conventional Example 1 is a normal silver-plated product, but the reflectance at a wavelength of 400 nm is 85% or less, and further, the reflectance is 85% at a wavelength of 450 nm. Means that the brightness is as high as 5 to 10%. This is expected to be suitably used for optical semiconductors using these wavelengths due to the improved reflectivity in the examples of the present invention. Furthermore, Conventional Example 2 is an example in which heat treatment is performed after silver plating to increase the crystal grain size to 0.5 μm or more, but the initial reflectance is slightly lower than 85% at a wavelength of 400 nm, and further heat resistance It turns out that the nature is inferior. This is considered to be because when the lead frame type is subjected to heat treatment as in Conventional Example 2, the copper component of the base material is easily diffused to the surface layer, and as a result, it is inferior in heat resistance. For this reason, the example of the present invention in which heat treatment is not used can provide an optical semiconductor lead frame that is excellent in heat resistance and in which the reflectance is not easily deteriorated by heat.
Furthermore, in Reference Example 1, since the plating structure remaining rate of the reflective layer made of silver is higher than 50%, the reflectance at wavelengths of 400 nm and 450 nm is lower than 85% and 90%, respectively. It can be seen that the improvement is insufficient.
Furthermore, in Reference Example 2 and Reference Example 3, although the plating structure remaining rate of the reflective layer made of silver is less than 50%, excessive heat treatment is applied after rolling. As a result, the reflectivity is greatly decreased and the reflectivity is decreased over the entire wavelength range, so that it is necessary to prevent the above-described appropriate heat treatment condition from being exceeded.
From these results, after forming a reflective layer made of silver as the outermost layer by electroplating, the reflectance is 85% or higher at a wavelength of 400 nm and reflected at a wavelength of 450 to 800 nm by reducing the plating structure remaining rate to 50% or less. An excellent optical semiconductor device that can achieve a rate of 90% or more and exhibits excellent luminance by using the lead frame of the present invention for an optical semiconductor device and can maintain high luminance over a long period because of excellent heat resistance. You can see that it can be provided.

DESCRIPTION OF SYMBOLS 1 Conductive base | substrate 2 Reflective layer 3 which consists of silver Optical semiconductor element 4 Intermediate layer 5 Mold resin 6 Sealing resin 7 Bonding wire 9 Insulation part (The area | region containing an insulation part was abbreviate | omitted)

Claims (6)

A lead frame for an optical semiconductor device comprising a reflective layer on at least one side or both sides of the outermost surface of a conductive substrate, wherein the reflective layer reflects at least light emitted by an optical semiconductor element. in the uppermost surface of the region, at least the surface of the plating structure of silver is weave working rate of 22% or more rolling plastic deformation sets in at least the surface, the area ratio of plating tissue remaining rate of silver is less than 50% The reflectivity at a wavelength of 400 to 800 nm is 85% or more, and the heat resistance is within 5% when the heat treatment is performed in the atmosphere at 150 ° C. for 3 hours in the air at a wavelength of 450 nm. A lead frame for an optical semiconductor device.   2. The lead frame 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 lead frame for an optical semiconductor device according to claim 1, wherein a thickness of the reflective layer after the plastic deformation is 0.2 to 10 μm.   The base body has n metal layers (n is an integer of 1 or more) thereon, and the reflective layer is provided on the base body directly or via at least one metal layer. The lead frame for an optical semiconductor device according to claim 1, wherein the lead frame is an optical semiconductor device. 5. A method of manufacturing a lead frame for a semiconductor device according to claim 1, wherein silver is applied to a region on the outermost surface on the conductive substrate that reflects at least light emitted from the optical semiconductor element. after forming a plating method a reflective layer of further Upon causing subjected to plastic working plastic deformation plating tissue of the reflective layer on the reflective layer,該塑of rolling construction method is not less than% working rate 22 of processing wherein the machining der Rukoto method of manufacturing an optical semiconductor device lead frame. An optical semiconductor comprising: an optical semiconductor element; and the lead frame for an optical semiconductor device according to any one of claims 1 to 4, provided at least at a place where the optical semiconductor element is mounted. apparatus.

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