JP5950563B2 - 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 base material, and after the light emitting element is mounted on the lead frame, the light emitting element and its peripheral part are prevented from being deteriorated due to external factors such as heat, moisture, and oxidation. The light emitting element and its periphery are sealed with resin, ceramic or the like.
In the case of an LED using a lead frame, a material such as a copper strip is formed into a punched shape by pressing or etching, and then plated with Ag, Au / Pd, or the like.

By the way, when the LED element is used as an illumination light source, the reflection material of the lead frame has a high reflectance in the entire visible light wavelength range (400 to 800 nm) (for example, the reflectance with respect to a reference material such as barium sulfate or aluminum oxide). 80% or more).
Furthermore, in the LED for illumination and backlight using white light, from the viewpoint of color rendering properties, instead of the conventionally used blue LED element and yellow phosphor, a near ultraviolet / ultraviolet LED element and RGB phosphor ( Techniques using red, green, and blue) have been developed. In this method, the reflective material of the optical semiconductor device is required to have a high reflectance in the near ultraviolet region (wavelength 340 to 400 nm) and the visible light region (wavelength 400 to 800 nm).

  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, it is known that a silver plating layer is formed on the reflection surface (Patent Document 1).

  On the other hand, as a method of improving the reflectance by giving gloss after plating, a method of giving a gloss by performing press processing after plating (Patent Document 2) is known.

  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. (Patent Document 3) is known.

  On the other hand, it is known to increase heat dissipation while enhancing the light reflection efficiency by covering the side reflecting surface with a metal lead frame by deep drawing (Patent Document 4).

  However, when only silver or an alloy film thereof is simply formed as in Patent Document 1, the decrease in the reflectance particularly in the near ultraviolet region (wavelength of 340 to 400 nm) is large, and it is short from about 400 nm in the visible light region. It was found that the reflectance reduction on the wavelength side (around 300 nm to 400 nm) is inevitable.

  Further, in the method of improving the reflection efficiency by producing gloss by a method of performing press working after plating as in Patent Document 2, a relatively high working rate is required to increase the reflectance. For this reason, in the press work of only a part of the flat portion, there is a problem that cracks are very likely to occur at the bent portion of the press processed portion and the original flat portion. In particular, it has been found that when the processing as shown in FIG. As a result, the copper of the base substrate is exposed from the cracked part, and after mounting the optical semiconductor device, the reflectance is lowered due to corrosion of the exposed part and copper contamination of the lead frame surface, and further, the element is damaged by elution of copper ions. The case of giving

  Since Patent Document 3 is intended for use as an electrical contact material, Patent Document 3 has no knowledge of optical properties such as reflectance, and specifically discloses a technique related to rolling for the purpose of improving reflectance. It has not been.

  Furthermore, when a lead frame is formed by the method of Patent Document 3 and mounted on, for example, an LED that is an optical semiconductor device, a fracture surface is always formed by pressing. The exposed surface of the base increases as the thickness of the base increases, especially when the surface of the base is disposed near the LED element and is resin-molded without extrapolation. Since copper is exposed in the same manner as in the case of Patent Document 2, there is a concern that corrosion, a decrease in reflectance, and damage to the LED element occur in the same manner.

  In addition, when the process of forming an optical semiconductor device is performed by the method of Patent Document 3, there is a problem in that a material is brought into contact with a mold or the like when the lead frame is conveyed, so that scratches due to sliding are easily formed. is there. This is because not only the reflectance is lowered due to sliding flaws, but also the cause of adhesion of impurities, even though the reflectance is already increased. It has been found that this causes a decrease in wire bonding properties. For this reason, it is necessary to solve these problems at the time of transportation in an area contributing to reflection of the lead frame.

  In general, including the technique described in Patent Document 4, in the deep drawing process, the surface of the deep drawing material whose reflectivity has been increased by sliding with the mold during the deep drawing process. There is an unavoidable problem that large scratches are formed, and as a result, there is a high possibility that the luminance improvement rate is lower than expected. Furthermore, since deep drawing is often performed in several stages, there are concerns about the complexity of the processing method and the occurrence of cracks caused by bending into a complicated shape.

Japanese Patent Laid-Open No. 61-148883 Japanese Patent Laid-Open No. 61-156679 Japanese Patent No. 3515226 JP 2010-245359 A

Therefore, the present invention provides an optical semiconductor device lead frame used in an LED, photocoupler, photointerrupter or the like whose emission wavelength includes the near ultraviolet to visible light range (wavelength 340 to 800 nm). 400 nm), particularly in the vicinity of a wavelength of 375 nm and in the visible light region (wavelength of 400 to 800 nm), particularly in the case of mounting an element that emits light in the vicinity of a wavelength of 450 nm, the reflectance in the recess for mounting the optical semiconductor element is 375 nm. With a reflectance of 75% or more at a wavelength of 450%, a reflectance at a wavelength of 450 nm of 85% or more, and a reflectance at a wavelength of 600 nm of 90% or more, high brightness and excellent heat dissipation, and corrosion even if a fracture portion is exposed. To provide a lead frame for an optical semiconductor device having no long-term reliability and damage to LED elements and LED elements, and a method for manufacturing the same. To. Another object is to provide an optical semiconductor device using this lead frame. In particular, the present invention is to obtain a reflection layer having high reflectance Ru der woven rolling deformation set by subjecting the rolling plating of silver or a silver alloy, mounting a subsequent step (described later, optical semiconductor elements The brightness is maintained by maximizing the high reflectance even after a step of forming a recess by a pressing method and a step of punching outside the recess at the same time as the formation of the recess or in a separate process) Another object is to provide a lead frame for an optical semiconductor device and a method for manufacturing the same, in which the maximum is improved.

  As a result of diligent investigations in view of the above-described problems of the prior art, the present inventors have conducted a lead frame for an optical semiconductor device in which a reflective layer made of silver or a silver alloy is formed on the outermost surface of a conductive substrate by a plating method. In the present invention, the reflective layer is excellent in the reflectivity of light in the near-ultraviolet region with a wavelength of 340 to 400 nm by forming a metallized structure by crushing the plated structure by rolling after forming the plated layer, The semiconductor with excellent light reflectivity, which can improve the reflectivity in the visible light range of 400 to 800 nm by several percent compared to the conventional silver plating film and is close to the theoretical value of silver. In the lead frame for equipment, by forming a recess for mounting the optical semiconductor element, it has excellent light reflectivity in the ultraviolet to visible light range, excellent light extraction efficiency, and bending bending. The lead frame for optical semiconductor devices that can improve the long-term reliability when assembled as a device, improve the adhesion to the mold resin, and maintain the highly reflective surface state to the maximum is obtained. I found. The present invention has been completed based on this finding.

That is, according to the present invention, the above problem 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 made of silver or a silver alloy is a rolled deformation structure , and the rolled surface of the lead frame for an optical semiconductor device is a recess for mounting an optical semiconductor element. have a reflectance at the concave portion is 75% or more reflectivity at a wavelength of 375 nm, 85% or more reflectivity at a wavelength of 450 nm, and wherein der Rukoto reflectivity of 90% or more at a wavelength of 600nm A lead frame for an optical semiconductor device.
(2) The lead for an optical semiconductor device according to (1), wherein the maximum depth of the concave portion is 0.5 to 3 times the thickness of the lead frame after the rolling process. flame.
(3) In the item (1) or (2), the reduction rate of the thickness of the lead frame after the rolling process at the bottom of the recess is 10% or less of the thickness before forming the recess. The lead frame for optical semiconductor devices as described.
(4) The silver or silver alloy forming the reflective layer is silver, silver-tin alloy, silver-indium alloy, silver-rhodium alloy, silver-ruthenium alloy, silver-gold alloy, silver-palladium alloy, silver-nickel The lead frame for an optical semiconductor device according to any one of (1) to (3), which is an alloy, a silver-selenium alloy, a silver-antimony alloy, or a silver-platinum alloy.
(5) A method for manufacturing a lead frame for a semiconductor device according to any one of (1) to (4), wherein at least light emitted from an optical semiconductor element is reflected on the outermost surface of the conductive substrate. At least a surface of a plated structure made of silver or a silver alloy by performing a rolling process and a step of forming a layer made of silver or a silver alloy in a region to be electroplated, an electroless plating method or a sputtering method. A step of forming a reflective layer having a rolled structure, and a recess formed by a pressing method at a place where an optical semiconductor element is mounted on a rolled surface of the lead frame for an optical semiconductor device after the reflective layer is formed And a step of performing a punching process on the outside of the concave part at the same time as the formation of the concave part or in a separate process, and exposing the conductive substrate in the punched part. Wherein the method of manufacturing an optical semiconductor device lead frame.
(6) The method for manufacturing a lead frame for an optical semiconductor device according to (5), wherein a rolling rate for forming the reflective layer is 1% or more and 80% or less.
(7) The arithmetic average height Ra of the rolling roll used in the rolling process for forming the reflective layer is 0.001 to 0.15 μm, as described in (5) or (6) Of manufacturing a lead frame for an optical semiconductor device.
(8) An optical semiconductor device, wherein an optical semiconductor element is mounted on the optical semiconductor device lead frame according to any one of (1) to (4).
(9) The optical semiconductor device according to (8), wherein an emission wavelength of the optical semiconductor element is 340 nm to 800 nm.

  According to the lead frame for an optical semiconductor device of the present invention, a plated layer made of silver or a silver alloy is formed on the outermost surface of the conductive substrate, and then a rolling process is performed to have a rolled and deformed processed structure. And having a reflective layer with an increased reflectivity, and further, by mounting the optical semiconductor element in the recess, the optical reflectivity in the near ultraviolet to visible light region (wavelength 340 to 800 nm) is excellent, and Since the efficiency of extracting light to the outside is superior to the conventional one in which the mounting portion of the optical semiconductor element is formed in a planar shape, high luminance can be obtained. Furthermore, since the reflective layer is formed by rolling after plating, the adhesion between the conductive substrate and the reflective layer is improved, and the ability to follow the bending of the reflective layer is increased, so that the conductive substrate is exposed. There is an effect that becomes difficult to do.

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. It is the schematic of an example of the manufacturing method of the lead frame for optical semiconductor devices which concerns on this invention.

The lead frame of the present invention is a lead for an optical semiconductor device having a reflective layer whose reflectance is increased by forming a plating layer made of silver or a silver alloy on the outermost surface of a conductive substrate and then rolling it. The frame is characterized in that, after the reflective layer is formed by the rolling process after plating, a recess for mounting the optical semiconductor element is formed by pressing.
Preferred embodiments of the present invention will be described with reference to the drawings as appropriate.

The conditions for the rolling process in the present invention are preferably cold working at a working temperature in the range of 25 ° C. to 100 ° C. and performed at a rolling reduction of 1 to 80%, but are not limited thereto. In the present invention, the simple rolling means the cold working, that is, cold rolling.
In particular, by setting the processing rate at the time of rolling after forming the reflective layer to 1% or more, the reflectance can be reduced over a wide range from near ultraviolet light to visible light region, which could not be achieved by conventional bright silver plating. It can be easily improved to the theoretical value level. As a result, the reflection characteristics are good, and in particular when using a light emitting element having a wavelength of 340 to 400 nm in the near ultraviolet region, and further in a visible light region of 400 to 800 nm, it is more reflective than conventional silver plating materials. An excellent lead frame for an optical semiconductor device can be provided.
Further, a more preferable light extraction efficiency can be achieved by setting the depth of the recess formed in the lead frame to be not less than 0.5 times and not more than 3 times the thickness of the lead frame after the rolling process. Can do. This is because, considering the light extraction efficiency, the luminance decreases as the number of times the light is reflected by the reflective layer, so that the depth of the concave portion needs to minimize the number of reflections. In addition, since the probability of occurrence of cracks in the bent portion increases as the depth of the recess increases, it is preferable that a depth of 0.5 to 3 times the thickness of the lead frame after the rolling process is formed. As a result, the light extraction efficiency can be increased, and the occurrence of cracks at the bent portion when the recess is formed can be suppressed.

Further, the reduction rate (in FIG. 1) of the thickness of the lead frame (reference symbol t ′ in FIG. 1) from the thickness of the lead frame after rolling (reference symbol t in FIG. 1) at the bottom of the formed recess. In terms of a symbol, t ′ × 100 / t) is preferably 10% or less. This is because the reflective layer whose reflectance has already been increased by rolling is formed in advance, so that the processing rate is not high enough to increase the reflectance. As a result, since it is not necessary to reduce the thickness of the lead frame at the bottom of the recess, the difference in the processing rate at the bent portion when forming the recess can be reduced, so that the generation of cracks at the bent portion is further suppressed. It becomes easy.
Here, as is apparent from the figure, the thickness of the lead frame in the present invention means the total thickness of the conductive substrate and the reflective layer provided thereon. When an intermediate layer is provided between the conductive substrate and the reflective layer, the thickness of the lead frame means the sum of the plate thickness of the conductive substrate, the thickness of the reflective layer, and the thickness of the intermediate layer. . Furthermore, as will be described later, since the reflective layer and the intermediate layer may be provided only on the surface on which the optical semiconductor device is mounted on the conductive substrate, the thickness of the reflective layer and the thickness of the intermediate layer in this case , And means the thickness provided on only one surface of the conductive substrate. On the other hand, since the reflective layer and the intermediate layer can be provided on both the surface (front surface) on which the optical semiconductor device is mounted on the conductive substrate and the back surface thereof, the thickness of the reflective layer and the thickness of the intermediate layer in this case The thickness of each of the two layers provided on both the front and back surfaces of the conductive substrate is meant. Furthermore, since the intermediate layer is not limited to one layer and may be provided in two or more layers, the thickness of the intermediate layer means the total thickness of all the intermediate layers provided on the conductive substrate.

  Furthermore, the recess for mounting the optical semiconductor element on the lead frame is formed by, for example, a pressing method after the rolling process for increasing the reflectivity. In any case, the fracture surface (surface indicated by reference numeral 6 in FIGS. 1 to 4) formed by pressing, which is a punching process for forming a lead frame in a region different from the concave portion, is an element. Processing that does not become the same plane as the bottom surface of the recess that is the mounting portion (the surface indicated by reference numeral 2a in FIG. 1) is performed. For this reason, since the formation of scratches due to the sliding of the punch in the punching process for the punching process is kept to a minimum, the press for forming the recesses after plating and rolling other than the pressing process for the punching process Even after processing, the surface state of the highly reflective reflective layer can be maintained to the maximum. In addition, the portion formed on the side surface of the recess (the surface indicated by reference numeral 2b in FIG. 1) is also formed of a highly reflective reflective layer, so that conventionally the portion formed mainly of white resin is also a metal. By forming it with a lead frame, there is no concern about a decrease in reflectivity due to resin degradation or the like, and an optical semiconductor device excellent in reflectivity can be provided. As a further effect, the conductive substrate (for example, copper) is intentionally exposed at the press end in the press working for the punching process, so that the adhesiveness with the mold resin can be enhanced as compared with the conventional silver plating layer. .

  As a result of the above, it has excellent reflectivity of light in the ultraviolet to visible light range, excellent light extraction efficiency, improved bending workability, improved adhesion to the mold resin, and a highly reflective surface An optical semiconductor device lead frame that can maintain the state to the maximum and has excellent long-term reliability can be obtained. Further, by using this optical semiconductor device lead frame, it is possible to provide an optical semiconductor device with higher brightness than in the prior art.

A layer made of silver or a silver alloy is rolled to form a reflective layer with increased reflectivity, thereby eliminating or significantly suppressing unnecessary absorption peaks in the vicinity of a wavelength of 345 nm to 355 nm, thereby improving the reflectivity. Therefore, it is preferably used for an optical semiconductor device in which a light emitting element having a wavelength range of 340 to 400 nm, particularly an emission wavelength of about 375 nm is mounted. At the same time, even in the visible light wavelength region of 400 nm to 800 nm, the reflectance can be increased to the theoretical value of silver.
A method of improving the reflection efficiency by producing a gloss by pressing after plating is disclosed in the prior art, but a relatively high processing rate is required to increase the reflectance. For this reason, in the press work of only a part of the flat surface portion, a convex portion formed by the bending portion of the press work portion and the original flat surface portion (the portion indicated by reference numerals R1 ′ and R2 ′ in FIG. 1). In this case, cracks are very likely to occur. As a result, the underlying conductive substrate (for example, copper) is exposed at the site where the crack occurs, and the reflectance decreases due to corrosion of the exposed portion and copper contamination of the lead frame surface after mounting the optical semiconductor device. It is not preferable because the element may be damaged by elution of copper ions. According to the present invention, since the reflective layer is formed by rolling after plating, the adhesion between the conductive substrate and the reflective layer is improved, and the ability to follow the bending of the reflective layer is enhanced. Furthermore, since the reflection layer that has been made highly reflective has already been formed by rolling, it is possible to form the recesses at a low processing rate, and thus there are few problems with such conventional techniques.

As described above, in the lead frame of the present invention, after the reflective layer is formed by the rolling process after the plating, the recess for mounting the optical semiconductor element is formed by the press process. Thus, by forming a reflective layer by rolling on the entire periphery forming the recess, it becomes difficult to cause a difference in processing rate due to the formation of the recess, and it is easy to suppress the occurrence of cracks in the bent portion, and the rolling process is performed. As a result, the adhesion between the conductive substrate and the reflective layer is improved and the ability to follow the bent portion of the reflective layer is increased, so that the substrate is difficult to be exposed.
In addition, since the optical semiconductor element is mounted in the recess, the reflection layer around the optical semiconductor element mounting position, which contributes to the light reflection, is prevented from sliding with the mold when the lead frame is punched. Is done. As a result, the formation of scratches due to sliding is minimized in the vicinity of the place where the optical semiconductor element is mounted, so that the highly reflective surface state of the reflective layer can be maintained to the maximum. In addition, since the portion formed as the side surface of the recess is also in a highly reflective surface state, the reflective layer at that location is also excellent in reflectance. As a result, the portion mainly made of white resin can be formed with a metal lead frame in the past, so there is no concern about a decrease in reflectance due to deterioration of the resin, etc., and it is formed with a highly reflective reflective layer. Therefore, a lead frame for a semiconductor device excellent in light reflectance and heat dissipation can be obtained. Furthermore, the recess can be processed without going through complicated steps by being formed by, for example, an overhanging process using a press method, which is relatively easy to process, and the bottom surface of the recess (indicated by reference numeral 2a in FIG. 1). Both of the scratches caused by sliding with the punches on the surface and the side surface (the surface indicated by reference numeral 2b in FIG. 1) can be minimized.
In addition, the fracture surface formed by press working to form the lead frame (the surface indicated by reference numeral 6 in FIGS. 1 to 4) is the bottom surface of the recess that is the element mounting portion (the surface indicated by reference numeral 2a in FIG. 1). ) Is processed in the same plane. For this reason, since the formation of scratches due to sliding is minimized, the highly reflective surface state can be maintained to the maximum. In addition, the portion formed as the side surface of the recess is also formed by a highly reflective layer. For this reason, conventionally, a portion mainly formed of white resin is also formed of a metal lead frame, so that there can be provided an optical semiconductor device that is free from the concern of a decrease in reflectance due to deterioration of the resin and has excellent reflectance. In the case of conventional silver plating, as a further effect, the conductive substrate (for example, copper) is intentionally exposed at the press end (the surface indicated by reference numeral 6 in FIGS. 1 to 4). It can be significantly increased compared to

  The maximum depth of the recess formed in the lead frame is preferably not less than 0.5 times and not more than 3 times the thickness of the lead frame after the rolling process. This is because, considering the light extraction efficiency, the luminance decreases as the number of times the light is reflected by the reflective layer, so that the depth of the concave portion needs to minimize the number of reflections. In addition, since the probability of occurrence of cracks in the bent portion increases as the depth of the recess increases, it is preferable that a depth of 0.5 to 3 times the thickness of the lead frame after the rolling process is formed. As a result, the light extraction efficiency is increased, and it is possible to suppress the occurrence of cracks at the bent portion caused by pressing during the formation of the recess. If it is the said range, it will be excellent in the light extraction efficiency, but in order not to generate | occur | produce a crack in a bending part, it is more preferable that the depth of a recessed part is 2 times or less of the thickness of the lead frame after a rolling process.

  Further, the bottom of the recess (the surface indicated by reference numeral 2a in FIG. 1) and the plane (the surface indicated by reference numeral 2c in FIG. 1) at the height before being processed are in the same plane. It should just be given so as not to become. The shape of the recess is not particularly limited, but for example, a shape viewed from the top is preferably a circle, an ellipse, a square, a rectangle, a hexagon or the like because the light extraction efficiency is good. There is no particular limitation on the shape of the side surface (the surface indicated by reference numeral 2b in FIG. 1), but a design in consideration of light extraction efficiency is required. In particular, when a planar side surface is formed, the angle formed by the bottom surface (2a in FIG. 1) and the side surface of the recess (2b in FIG. 1) is set to the bottom surface (2a in FIG. 1). ) In the range of 10 ° to 60 °, and more preferably in the range of 20 ° to 45 °. When bending is performed, the bending radius (the portion indicated by reference numerals R1 and R2 in FIG. 1) is designed to have a bending radius that does not cause cracking of the conductive substrate and the surface reflection layer. For example, the inner bending radius (R, unit mm) is preferably in the range of 5 times or less the thickness (unit mm) of the lead frame after the rolling process, and is 0.5 to 3 times. More preferably, it is within the range.

  Further, the reduction rate of the thickness of the lead frame (t ′ (mm) in FIG. 1) at the bottom of the recess formed after the rolling process is the thickness after the rolling process of the flat part before the recess processing (FIG. 1). Middle (t (mm)) is preferably 10% or less, more preferably 5% or less. This is because a reflective layer having a higher reflectance is formed in advance before the formation of the recess, so that a high processing rate that increases the reflectance is not required when forming the recess. As a result, since it is not necessary to reduce the thickness of the lead frame at the bottom of the recess, the difference in the processing rate in the bent portion when forming the recess is very small, so that cracks are further generated in the bent portion. There is an effect of being easily suppressed.

  Further, the silver or silver alloy forming the reflective layer in the lead frame for optical semiconductor devices of the present invention is silver, silver-tin alloy, silver-indium alloy, silver-rhodium alloy, silver-ruthenium alloy, silver-gold alloy, A lead frame having good reflectivity and good productivity is made of a material selected from the group consisting of silver-palladium alloy, silver-nickel alloy, silver-selenium alloy, silver-antimony alloy, and silver-platinum alloy. In particular, silver, a silver-tin alloy, a silver-indium alloy, a silver-palladium alloy, a silver-selenium alloy, or a silver-antimony alloy is more preferable from the viewpoint of improving the reflectance.

  The method for forming the silver or silver alloy layer to be the reflective layer is not particularly limited, and for example, it is formed by electroplating, electroless plating, or sputtering. These methods are preferable because the management of the plating coating thickness is relatively easy and processing at a low temperature is possible. Among them, the electroplating method is most preferable because of excellent productivity.

As described above, the reflective layer on the surface made of silver or a silver alloy may be formed by wet plating by an electroplating method or an electroless plating method, or by a dry method on the surface of the conductive substrate by a sputtering method. You may form by performing plating and making it precipitate. Here, the electroplating method is described as a representative example, but in the case of the electroless plating method and the sputtering method, a layer made of silver or a silver alloy is used in the same manner as in the case of the electroplating method. 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.
In the lead frame for an optical semiconductor device of the present invention, the thickness of the reflective layer after the rolling process made of silver or a silver alloy is not particularly limited. For example, the lower limit is 0.2 μm or more. Thus, the reflectivity can be stably increased, and deterioration due to heating in a subsequent process such as wire bonding or sealing with resin or glass can be suppressed. When it is thinner than the lower limit (for example, 0.1 μm), discoloration due to heating occurs, and the conductive substrate is easily exposed by the concave processing. For this reason, in order to prevent discoloration due to heating or processing more stably, the thickness of the reflective layer after rolling is preferably 0.5 μm or more, more preferably 1.0 μm or more. On the other hand, the upper limit value of the thickness of the reflective layer is preferably 30 μm or less, more preferably 10 μm or less, and even more preferably 5 μm, from the viewpoints of reduction of silver as a noble metal and plating processing costs.
In order to reduce the amount of noble metal used, the coating thickness of the reflective layer may be different between the surface on which the optical semiconductor element is mounted and the back surface thereof. This is because the back surface may be sufficient if solderability is ensured. For example, the thickness of the reflective layer made of silver or a silver alloy on the back surface may be about 0.1 μm. By doing so, not only the amount of noble metal used is reduced, but also the amount of power used during production is reduced, and therefore, an environment-friendly and low-cost lead frame for an optical semiconductor device can be provided.

  In the present invention, a metallographic structure (plating structure) formed by electroplating, electroless plating or sputtering is provided on the outermost surface with a reflective layer having a processed structure deformed by rolling. To do. Here, the metallographic structure having a processed structure is different from the cast structure as well as from the plated structure before deformation formed by plating, as is apparent metallurgically in the present technical field. Specifically, after the normal plating, a fine crystal structure is observed on the surface, and a needle-like structure, a precipitated state of spherical particles, and the like are observed. On the other hand, the surface state after rolling after plating exhibits a surface property such that the rolls of the rolling rolls are transferred to the lead frame side. For example, the observation magnification is 2000 to 10,000 times with a general-purpose SEM. The surface can be clearly distinguished by observing the surface.

  Furthermore, according to the lead frame of the present invention, not only the wavelength of 340 to 400 nm in the near ultraviolet region but also the wavelength of 400 to 800 nm in the visible light region can reach the physical theoretical value of the reflectance of silver as much as possible. I can do it. This is because the reflectivity is about 98% at a wavelength of 450 nm when pure silver is formed on a mirror substrate such as silicon by sputtering. It is a numerical value that cannot be achieved. The inventors have made a rolling structure after plating to cause deformation in the rolling structure by rolling, reduce the fine irregularities by crushing the plating structure, and reduce and eliminate the grain boundaries. As a result of having reduced the light absorption phenomenon to the limit, it has been clarified that the reflectance can be brought close to the theoretical value even in the visible light region. As a result, by using the lead frame according to the present invention, excellent luminance can be obtained even in a conventional optical semiconductor device in the visible light range, and a blue light emitting element having a wavelength range of 400 to 800 nm, particularly a light emission wavelength of around 450 nm is mounted. It is suitably used for an optical semiconductor device.

  In the present invention, the reflection layer made of silver or a silver alloy may be formed on the outermost surface of at least a portion that contributes to light reflection (that is, a region that reflects at least light emitted from the optical semiconductor element). In other portions, a reflective layer may or may not be provided, and even if a layer other than the reflective layer is formed, there is no particular problem in terms of reflectivity.

The lead frame for an optical semiconductor device of the present invention is not particularly limited with respect to the conductive substrate, but for example, copper or copper alloy, iron or iron alloy, or aluminum or aluminum alloy can be used. By using these materials as the conductive substrate, it is possible to provide a lead frame that has good reflectance characteristics, can easily form a coating of a reflective layer or an intermediate layer, and can contribute to cost reduction. 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 of time. This depends on the conductivity of the substrate, preferably at least 10% by IACS (International Annealed Copper Standard), more preferably 50% or more.
In the present invention, the thickness of the lead frame at the bottom of the concave portion after formation of the concave portion (reference symbol t ′ in FIGS. 1 and 2) is not particularly limited, but is usually 0.05 to 1 mm. Yes, preferably in the range of 0.1 to 0.5 mm. That is, the thickness of the conductive substrate after the formation of the recess is expressed as a difference obtained by subtracting the thickness of the reflective layer from the thickness t ′ of the lead frame at the portion, or if provided. For example, it is expressed as a difference obtained by subtracting the total thickness of the intermediate layer and the reflective layer.

  The lead frame for an optical semiconductor device of the present invention includes nickel, nickel alloy, cobalt, cobalt alloy, copper, and a copper alloy between the conductive base and the reflective layer made of silver or a silver alloy. An intermediate layer made of a selected metal or alloy may be provided. The intermediate layer is suitably formed by plating, for example.

For example, when an iron-based substrate is used, the thermal conductivity of the material is relatively low. Therefore, by providing a copper or copper alloy layer as an intermediate layer, the heat dissipation can be improved without impairing the reflectance. Furthermore, since the plating layer which is the copper or copper alloy layer 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 or a copper alloy is used as the conductive substrate, nickel, nickel alloy, cobalt, or cobalt alloy is used as an intermediate layer in order to suppress diffusion of the substrate component to the reflective layer due to heat generated when the light emitting element emits light. It is effective to provide these layers.
The thickness of these intermediate layers is not particularly limited in the present invention, but is preferably 0.05 to 2.0 μm, more preferably 0.2 to 1.0 μm.
In order to improve the adhesion between the conductive substrate and the reflective layer in the lead frame, it is preferable to use copper or a copper alloy as a material constituting the intermediate layer. Furthermore, a two-layer intermediate layer may be used as the base of the reflective layer, for example, by performing nickel (Ni) plating after copper (Cu) plating.

The production method according to the present invention will be described in detail using an example.
A plating layer made of silver or a silver alloy is formed on part or all of both or one side of a conductive substrate (for example, strip material) using electroplating, electroless plating, or sputtering, and then rolled. By performing the processing, a reflective layer with an increased reflectance is formed. Next, in a step where a concave portion is provided by a press method, for example, in a place where the optical semiconductor element is mounted, and at the same time as the concave portion formation or in a separate step, the outer side of the concave portion is subjected to a punching process. The processed fracture portion is subjected to a step of exposing the base body to obtain a predetermined lead frame shape. An optical semiconductor module is manufactured by sealing the lead frame with an outer resin mold, mounting of an optical semiconductor element, wire bonding, and resin or glass containing a phosphor.
In the conventional method, generally, a conductive base (such as a strip) is formed into a lead frame shape by press working or etching, and thereafter, bright silver plating or gold / palladium / nickel plating is performed. In the present invention and the conventional method, the present invention is obtained by modifying the plating structure as a mechanical processing finish, whereas in the conventional method, the plating finishes or plating in which the reflectance is not taken into consideration. The structure and reflectivity are completely different from each other in terms of rolling and heat treatment.

In addition, the processing rate (also referred to as the rolling reduction or the area reduction rate) of the rolling process after forming the reflective layer made of silver or a silver alloy is preferably 1% or more, more preferably 10% or more, and further preferably 20% or more. is there. On the other hand, as the upper limit of the processing rate, if it exceeds 80%, not only the effect of improving the reflection characteristics is saturated, but also the base body undergoes work hardening, the elongation rate decreases, and cracks and cracks during bending are likely to occur. Therefore, it is preferably 80% or less, more preferably 60% or less, and still more preferably 50% or less.
“Processing rate” indicates a ratio represented by “(plate thickness before processing−plate thickness after processing) × 100 / (plate thickness before processing)”.

Rolling to a material in which a part or all of the conductive substrate is coated with silver or a silver alloy is performed by, for example, 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 suitably.
The processing rate in the rolling process is preferably 1% or more, more preferably 10% or more, and even more preferably 20% or more. The gap between the crystal grain boundaries of silver or a silver alloy is sufficiently narrowed to obtain a rolling deformation structure. It can be rolled and the adhesion between the substrate and the reflective layer is improved and the ability to follow the bent portion of the reflective layer can be enhanced.
The rolling roll used for the rolling process is an arithmetic average (Ra) of the surface roughness, preferably less than 0.15 μm, more preferably, in consideration of improving the reflectance on the lead frame side formed by transferring the rolls. Ra is less than 0.05 μm. When the roughness increases, the reflectivity cannot be sufficiently increased, and the unevenness to which the rolling rolls are transferred at the time of bending is relatively large, which causes the base to crack. It becomes easy. On the other hand, the lower limit value of the arithmetic average (Ra) of the surface roughness of the rolling roll is not particularly limited, and may be a lower limit value of a commonly used rolling roll.

  Moreover, the optical semiconductor device of the present invention is provided with a plated layer made of silver or a silver alloy at least at a location where light generated from the optical semiconductor element is reflected, and has a processed structure deformed by rolling. By using the lead frame of the present invention having the above, it is possible to obtain reflection characteristics with high luminance at low cost. This is because the reflectance characteristics can be sufficiently improved by forming the reflective layer only at the location where the light generated from the optical semiconductor element is reflected. In the case where the mounting surface of the optical semiconductor element is only one surface of the lead frame, in the double-sided plating material, the optical semiconductor element mounting surface may be thick and the non-mounting surface may be thin.

  Furthermore, the reflective layer may be partially formed, and may be formed by partial plating such as single-sided plating, stripe plating, spot plating, and then rolling. Manufacturing a lead frame in which the reflective layer is partially formed can reduce the amount of metal used in the part where the reflective layer is unnecessary, so that a lead frame with a low environmental load can be obtained. Fewer optical semiconductor devices can be obtained.

Furthermore, in order to control the required mechanical properties, heat treatment (also referred to as tempering or low-temperature annealing) is performed by a technique such as batch type or running type after mechanical processing such as rolling. At the same time, the bonding force between the crystal grains can be strengthened at the crystal grain boundaries to narrow the intergranular spacing, but it is necessary to limit the heat treatment to a level that does not lower the reflectivity.
The conditions for the heat treatment performed after mechanical processing such as rolling are not particularly limited. For example, the heat treatment is performed at a temperature of 50 to 150 ° C. for 0.08 to 3 hours. It is 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 present invention, the reflectance is excellent or the high reflectance is a spectrophotometer (for example, V660 (trade name, manufactured by JASCO Corporation)) when the barium sulfate standard plate is 100%. When the total reflectance is continuously measured from the ultraviolet region to the visible light wavelength range of 300 nm to 800 nm with respect to the bottom center diameter of 0.5 mm of the recess of the lead frame, the reflectance at the near ultraviolet wavelength of 375 nm is 75% or more, visible light It means that the reflectance at a wavelength of 450 nm is 85% or more and 90% or more at a wavelength of 600 nm.

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 or a silver alloy is formed on a conductive substrate 1, and an optical semiconductor element 3 is mounted in a recess 4 on a part of the surface of the reflective layer 2. Yes. Further, the other lead frame insulated by the breaking portion 6 formed as a lead frame and the optical semiconductor element 3 are electrically connected by the bonding wire 5 to form a circuit. The concave portion is formed in a suitable shape such as a circle, an ellipse, a square, a rectangle, or a hexagon as viewed from above in the figure. The bottom surface (2a) and the side surface (2b) of the concave portion are the bottom surfaces of the concave portions. Is formed by an angle (7) formed by the perpendicular line from the side surface of the recess and the side surface of the recess, and each of the bent portions R1 and R2 is formed by pressing. In the present invention, in the lead frame of the present embodiment, the reflective layer 2 is formed by electroplating, for example, and then has a processed structure that is deformed by rolling, and has a near-ultraviolet region and a visible light region (wavelength 340 nm). The lead frame for an optical semiconductor device is excellent in reflection characteristics (˜800 nm).

The maximum depth (the maximum value of the distance between the bottom surface 2a and the top surface 2c) of the recess 4 formed in the lead frame is 0.5 to 3 times the thickness of the lead frame after the rolling process. Is preferable, and it is more preferable that it is 2 times or less.
Further, when the side surface of the recess as shown in FIG. 1 is not a curved surface, the angle 7 formed by the bottom surface and the side surface of the recess is preferably 10 ° to 60 ° from the perpendicular to the bottom surface, and is 20 ° to 45 °. More preferably. This angle 7 can also be adjusted in order to increase the light extraction efficiency by changing it appropriately according to the shape of the chip.
The bending radii at the bending portions R1 and R2 are preferably set to be not more than 5 times the thickness of the lead frame at the bottom of the recess after the formation of the recess, in order to prevent cracking due to bending. More preferably, it is 5 to 3 times. The bending radii at all two bending portions of R1 and R2 may be the same or different depending on the location, but are preferably formed with the same bending radius.
Furthermore, the thickness of the lead frame after being rolled (reference symbol t ′ in FIGS. 1 and 2) of the thickness of the lead frame (reference symbol t ′ in FIGS. 1 and 2) at the bottom of the formed concave portion. It is preferable that the reduction rate from is 10% or less. That is, by satisfying t ≧ t ′ ≧ 0.9 × t, occurrence of cracks in the bent portion can be further suppressed.

  In FIG. 1, the base 1 is exposed at the break 6 formed when the lead frame is formed by pressing, etching, or the like. This is because the substrate 1 is deliberately exposed at the press end, so that a component having better adhesion with the resin than silver appears, and the adhesion with the mold resin used when forming the optical semiconductor device is improved. This is because it can be higher than conventional silver. The fractured portion 6 may be subjected to a coating process such as by providing solderability by extrapolation plating or the like by a conventional method except for a portion that is in close contact with the mold resin, and particularly when adhesion is not required. Then, masking or the like may be performed to protect the reflective layer 2 and a process of covering only the fracture portion 6 may be performed.

  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 8 is formed between the base 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. In the lead frame of the embodiment shown in FIG. 3, the reflective layer 2 that has been rolled, for example, after electroplating is formed on the surface on which the optical semiconductor element is mounted, and the back surface thereof has, for example, solderability The reflective layer 2 is arranged with a coating thickness of about 0.1 μm to 0.5 μm thinner than the semiconductor element mounting surface. In this way, it is possible to change the coating thickness depending on the surface, or to not form the reflective layer 2 at all on the back surface of the optical semiconductor device mounting surface. As a result, a lead frame for an optical semiconductor device is provided that not only contributes to cost reduction because the amount of noble metal used is reduced, but is also environmentally friendly.

  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. FIG. 4 shows a state in which the optical semiconductor module is formed by the mold resin 9 and the sealing resin 10 for convenience. As described above, since the portion where the light emitted from the optical semiconductor element 3 is reflected is almost reflected by the reflective layer 2 formed in the concave portion, conventionally, the portion mainly formed of white resin is also included. By forming with a lead frame, there can be provided a long-term reliability lead frame for an optical semiconductor device and an optical semiconductor device that do not have a concern about a decrease in reflectance due to resin degradation or the like.

FIG. 5 is a view schematically showing an example of a method for manufacturing an optical semiconductor device lead frame according to the present invention. The method for producing a lead frame for an optical semiconductor device according to the present invention includes, for example, (1) a step of preparing a conductive substrate, and (2) a layer made of silver or a silver alloy in a region that reflects at least light emitted from the optical semiconductor element. Forming a reflective layer with increased reflectivity by applying a rolling process, and (4) reflecting. A step of forming a concave portion by, for example, a press method at a place where the optical semiconductor element is mounted after the layer is formed, and (5) a blanking process is performed on the outside of the concave portion at the same time as the concave portion formation or in a separate step. The punched portion is a step of obtaining a lead frame in which the base is exposed, (6) a step of forming an outer resin with a mold resin, and (7) mounting an optical semiconductor element to perform wire bonding. Process , Including step, a city of forming an optical semiconductor device and Fuko an optical semiconductor device using the (8) a sealing resin.
Thus, by forming a recess for mounting the optical semiconductor element in the next step (4) in the reflective layer formed in the step (3), the formation of scratches due to sliding near the position where the optical semiconductor element is mounted. Since it is kept to a minimum, a highly reflective surface state can be maintained to the maximum. In addition, since the portion formed as the inner surface of the recess (2b in FIG. 1) is also a highly reflective surface state, by conventionally forming the portion mainly formed of white resin with a metal lead frame, Since there is no concern about a decrease in reflectivity due to resin degradation or the like, an optical semiconductor device with long-term reliability can be provided. Further, by exposing the conductive substrate to the fracture portion (6 in FIGS. 1 to 4) formed in the step (5), the adhesiveness with the mold resin formed in the step (6) is improved. This can be remarkably improved as compared with the case of plating.
From these effects, it is possible to obtain a lead frame for an optical semiconductor device that improves long-term reliability when incorporated as a device, improves adhesion to a mold resin, and can maintain a highly reflective surface state to the maximum extent. A suitable manufacturing method is provided.

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

Example 1
As Example 1, as a conductive substrate, a substrate having a width of 50 mm: C18045 (Cu-0.3Cr-0.25Sn-0.5Zn, manufactured by Furukawa Electric Co., Ltd., trade name: EFTEC-64T), the thickness is 0.3 mm or 0.15 mm was prepared. This was subjected to the following pretreatment. Thereafter, matte silver (Ag) plating having a thickness of 5 μm shown below was formed on a substrate having a thickness of 0.3 mm. The base having a thickness of 0.15 mm was plated with bright silver (Ag—Se alloy) having a thickness of 2.5 μm shown below.
The alloy number indicates the type according to the CDA (Copper Development Association) standard. In addition, the number before each element represents content and the unit is the mass%.
In either case, pretreatment through electrolytic degreasing and pickling steps was performed. Also, before each silver or silver alloy plating, the silver strike plating is performed, and the outermost layer plating thickness is the thickness after rolling including the silver strike plating thickness (thickness at the position on the bottom of the formed recess). )).

The pretreatment conditions in Example 1 are shown below.
(Pretreatment conditions)
[Cathode 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 [Ag strike plating] coating thickness 0.01 μm
Plating solution: KAg (CN) ₂ 5 g / liter, KCN 60 g / liter Plating condition: current density 2 A / dm ² , plating time 4 seconds, temperature 25 ° C.

The liquid composition and plating conditions for the reflective layer plating used in Example 1 are shown below.
(Silver plating conditions)
[Ag plating]: Matte silver 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.
[Ag-Se alloy plating]: Bright silver plating plating solution: KCN 150 g / liter, K ₂ CO ₃ 15 g / liter, KAg [CN] ₂ 75 g / liter, Na ₂ O ₃ Se · 5H ₂ O 5 g / liter : Current density 2A / dm ² , temperature 50 ° C

Next, after forming a matte silver plating film of 5 μm on both sides on an Ag strike plating product obtained using a conductive substrate having a plate thickness of 0.3 mm as Invention Example 1, a 6-high rolling mill ( Using a work roll having a roll roughness Ra≈0.05 μm using Hitachi, Ltd.), the processing rate (or rolling reduction) at the time of rolling relative to the initial plate thickness is 50%, that is, the plate thickness of the flat portion after rolling ( A reflective layer-formed product having a symbol t) of 0.15 mm in FIG. 1 was obtained. Thereafter, the depth of the concave portion is set to 0.15 mm (1.0 times the plate thickness after rolling) by pressing, and the bending radius (the bending radius at the bending portion corresponding to the symbols R1 and R2 in FIG. 1) R = 0 The lead frame is formed by forming a recess in a rectangle having a size of 2.0 mm × 1.5 mm under the condition of an angle of 22.5 ° between the bottom perpendicular of the recess and the side surface (reference numeral 7 in FIG. 1). Obtained. The thickness of the formed reflective layer is reduced by the processing rate with respect to the initial coating thickness. Therefore, when the processing rate is 50%, the initial coating thickness is 50%, which is formed in Invention Example 1. The reflective layer thickness was 2.5 μm. Furthermore, when the plate thickness reduction rate “(t−t ′) × 100 / (t)” at the bottom of the concave portion of the lead frame at this time was measured with a micrometer, it was 2%.
Further, as Conventional Example 1, after forming a matte silver plating film of 5 μm on both sides on an Ag strike plating product obtained using a conductive substrate having a plate thickness of 0.3 mm, the press working rate is 50% with a press machine. A lead frame in which a recess was formed with the same dimensions as above while being crushed was prepared. When the plate thickness reduction rate at this time was measured with a micrometer, it was 50%. Further, as a conventional example 2, an Ag strike plating product obtained using a conductive substrate having a thickness of 0.15 mm was subjected to press working with the same dimensions (2.0 mm × 1.5 mm rectangle) as described above. After forming the recess, a lead frame having a bright silver plating of 2.5 μm was prepared. In Conventional Example 2, since neither rolling nor pressing is performed after the plating is formed, the thickness of the reflective layer does not decrease and remains unchanged.

(Evaluation method)
The lead frames of the inventive examples and the conventional examples obtained as described above were evaluated according to the following tests and standards.
(1A) Reflectance measurement: in a spectrophotometer (V660 (trade name, manufactured by JASCO Corporation)), the bottom center of the concave portion with a total reflectance of a wavelength of 300 nm to 800 nm when the barium sulfate standard plate is taken as 100% Continuous measurement was performed on the reflectance at φ 0.5 mm. Among these, Table 1 shows the total reflectance (%) at a wavelength of 375 nm in the near ultraviolet region, and further at wavelengths of 450 nm and 600 nm in the visible light region. The required characteristics were that the reflectance at a wavelength of 375 nm in the near ultraviolet region was 75% or more, the reflectance at a wavelength of 450 nm in the visible light region was 85% or more, and 90% or more at a wavelength of 600 nm.
(1B) Bending crack resistance: In a bending part (location corresponding to R1, R1′R2, R2 ′ in FIG. 1) generated by forming a concave portion, a microscope (VH-8000 (trade name, KEYENCE CORPORATION) Manufactured)) and magnified 200 times, and the presence of bending cracks exposing the substrate was investigated. As a result of observation, the case where a crack occurred even at one place was described as “Yes”, and the case where no crack was found as “No”. “None” is a required characteristic.
The results are shown in Table 1.

The following can be seen from the results in Table 1.
In Invention Example 1, the reflectance at the bottom is 75% or more at a wavelength of 375 nm, 85% or more at a wavelength of 450 nm in the visible light region, and 90% or more at a wavelength of 600 nm. In addition, no cracks were observed in the bent portion when the recess was formed.
On the other hand, in Conventional Example 1 in which the reflective layer was formed by pressing rather than rolling, the required characteristics were satisfied, but the reflectance was low, as compared with Invention Example 1 in which the reflective layer was formed by rolling. Moreover, the crack in the bending part has generate | occur | produced and the mode that the electroconductive base | substrate was exposed was seen. This is because when the reflective layer is formed by press working, it is necessary to locally increase the processing rate, and therefore cracks are likely to occur due to the difference in plate thickness.
In addition, the reflection layer is formed by gloss plating after forming the recess, and the conventional example 2 which is not subjected to rolling or pressing on the entire surface satisfies the required characteristic of a reflectance of 85% or more at a wavelength of 450 nm in visible light. In addition, since the reflection characteristics are lower than those of the inventive examples, it can be seen that the inventive optical semiconductor device can provide an excellent luminance.
As a result, according to the present invention, the reflective layer is formed by rolling after plating of silver or a silver alloy, and the concave portion is formed by pressing after the reflective layer is formed. By forming the recess so that the reduction rate of the lead frame thickness (t ′ × 100 / t in terms of the symbol in FIG. 1) is 10% or less, a reflective layer that could not be achieved by the conventional product can be obtained. It can be seen that a lead frame for an optical semiconductor device having reflectivity close to physical characteristics and excellent bending workability can be provided.

(Example 2)
As Example 2, as a conductive substrate, a substrate having a width of 50 mm shown in Table 2 was subjected to the following pretreatment, and then the intermediate layer (if applicable) and the reflective layer shown in Table 2 were respectively electroplated. In addition, a recess having the same shape as in Example 1 is formed by press working, and the reduction rate of the thickness of the lead frame after the rolling process at the bottom surface of the recess is 10% or less of the thickness before the rolling process. An invention example, a reference example, and a conventional example were obtained. It is known that the thickness of each coating layer changes at the same reduction rate as each rolling process rate, the thickness of the conductive substrate after rolling after formation of the reflective layer, the intermediate layer (if applicable), and the reflective layer The total plate thickness including each coating thickness, that is, the lead frame thickness is 0.2 mm. Therefore, considering the rolling rate, the initial plate thickness, intermediate layer thickness, and reflective layer initial coating (during plating) thickness It was formed by changing. Thereafter, using a 6-high rolling mill (manufactured by Hitachi, Ltd.) and performing rolling using a roll whose surface roughness Ra of the rolled work roll is changed as shown in Table 2, the configuration shown in Table 2 The lead frames of the inventive examples and the reference examples were obtained. In addition, as a conventional example, the same lead frame of Conventional Example 2 as that formed in Example 1, in which bright silver plating was applied after forming a recess, was compared. In addition, as a conventional electrical contact material, in order to prepare what simulated the comparative example 1 of the patent document 3 as the reference example 5, and what simulated the example 2 of the patent document 3 as the reference example 6, respectively, it rolled. After the processing, what was heat-treated at 240 ° C. for 4 hours in an air atmosphere was prepared.
In addition, electrolytic degreasing and pickling were performed in the same manner as in Example 1.

The pretreatment conditions in Example 2 are shown below.
(Pretreatment conditions)
[Cathode 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 [Ag strike plating] coating thickness 0.01 μm
Plating solution: KAg (CN) ₂ 5 g / liter, KCN 60 g / liter Plating condition: current density 2 A / dm ² , plating time 4 seconds, temperature 25 ° C.

The liquid composition and plating conditions of the intermediate layer plating used in Example 2 are shown below.
(Interlayer 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 5A / 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.

The liquid composition and plating conditions for the reflective layer plating used in Example 2 are shown below.
(Reflective layer plating conditions)
[Ag plating]: Matte silver 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.
[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 Plating condition: current density 1 A / dm ² , temperature 40 ° C.
[Ag-In alloy plating]
Plating solution: KCN 100 g / liter, NaOH 50 g / liter, AgCN 10 g / liter, InCl ₃ 20 g / liter Plating condition: current density 2 A / dm ² , temperature 30 ° 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 Se · 5H ₂ O 5 g / liter Plating condition: 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 Plating conditions: current density 1 A / dm ² , temperature 50 ° C.

Among the materials used as the conductive substrate, “C14410 (Cu-0.15Sn-0.01P, manufactured by Furukawa Electric Co., Ltd., trade name: EFTEC-3)”, “C19400 (Cu—Fe alloy material) , Cu-2.3Fe-0.03P-0.15Zn) "," C18045 (Cu-0.3Cr-0.25Sn-0.5Zn, Furukawa Electric Co., Ltd., trade name: EFTEC-64T) " “C26000 (brass, Cu-30Zn)” and “C52100 (phosphor bronze, Cu-8Sn-P)” represent a copper or copper alloy substrate, and the alloy number represents a type according to CDA (Copper Development Association) standards. In addition, the number before each element represents content and the unit is the mass%.
Before each silver or silver alloy plating, the silver strike plating is performed, and the outermost layer plating thickness is the thickness after rolling including the silver strike plating thickness (thickness at the position on the bottom of the formed recess) It was written as.

(Evaluation method)
The lead frames of the invention examples, reference examples and conventional examples obtained as described above were evaluated according to the following tests and standards.
(2A) Reflectance measurement: In a spectrophotometer (V660 (trade name, manufactured by JASCO Corporation)), the bottom of the concave portion with the total reflectance when the barium sulfate standard plate is 100% is applied to a wavelength of 300 nm to 800 nm. Continuous measurement was performed on the reflectance at the center φ0.5 mm. Among these, Table 3 shows the total reflectance (%) at a wavelength of 375 nm in the near ultraviolet region, and further at wavelengths of 450 nm and 600 nm in the visible light region. The required characteristics were that the reflectance at a wavelength of 375 nm in the near ultraviolet region was 75% or more, the reflectance at a wavelength of 450 nm in the visible light region was 85% or more, and 90% or more at a wavelength of 600 nm.
(2B) Resistance to bending cracking: In a bent portion (location corresponding to R1, R1′R2, R2 ′ in FIG. 1) generated by forming a concave portion, a microscope (VH-8000 (trade name, KEYENCE CORPORATION) ))), And the presence or absence of bending cracks that expose the substrate is investigated, and those that do not generate cracks are marked as “excellent”, and they are wrinkled but not cracked. "Good" if it is "Good", "Fair" if it is slightly cracked but the base is not exposed, and "No" if it is cracked and the base is exposed Represented by “x”. “Available” or higher was regarded as a practical level.
(2C) Heat resistance: The reflectivity after subjecting each lead frame to heat treatment at 200 ° C. for 2 hours in the atmosphere was measured, and the change in reflectivity before and after heating was regarded as heat resistance. Evaluation was based on the rate of decrease from the reflectance before heating. When the reflectivity decrease rate at a wavelength of 450 nm after heating is less than 5%, it is judged as “good”, and when the reflectivity decrease rate is between 5% and less than 10%, it is judged as “good”. “Δ” and those with a reflectance reduction rate of 10% or more were judged as “impossible” and represented by “x”. “Available” or higher was regarded as a practical level.
The above results are shown in Table 3.

  As is clear from these results, a comparison is made between Conventional Example 2 in which the reflective layer is formed by gloss plating after forming the recesses and not subjected to rolling or pressing on the entire surface and Invention Example 12 in which the rolling is performed. Obviously, the inventive example has a higher reflectance, which is very effective for increasing the reflectance. Further, in another example of the present invention, the reflectance at a wavelength of 340 nm to 400 nm, particularly 375 nm, which is in the near ultraviolet region is good, 75% or more at a wavelength of 375 nm, and 85% at a wavelength of 450 nm in the visible light region. As described above, 90% or more was satisfied at 600 nm. In particular, a lead frame for an optical semiconductor device that exhibits excellent reflectivity characteristics and has excellent bending workability and heat resistance because the rolling process rate is 1% or more and 80% or less, more preferably 10 to 60%. You can see that it can be provided.

Furthermore, in Reference Example 1, since the coating thickness of the reflective layer, which is the outermost layer, is as thin as 0.1 μm, the heat resistance is inferior and the reflectance at wavelengths of 375 nm and 600 nm is improved, but it is inferior to Invention Example 25. It can be seen that the coating thickness of the reflective layer as the outermost layer is preferably 0.2 μm or more.
Further, in Reference Example 2, the processing rate at the time of rolling after forming the plating layer for forming the reflective layer is as low as 0.5%, so that the reflectance remains at a level that is not sufficient.
Furthermore, in Reference Example 3, the processing rate (area reduction rate) during rolling after forming the plating layer for constituting the reflective layer is in a state exceeding 80%, but the reflectivity and heat resistance are excellent, It was confirmed that the bending workability was inferior.
From the results of Reference Example 2 and Reference Example 3, it can be seen that the area reduction rate is preferably 1 to 80%. Furthermore, when bending workability and reflectance are emphasized, a surface reduction rate of 20 to 60% is more preferable.
Furthermore, in Reference Example 4, the roll roughness of the rolling process exceeds 0.15 μm. In this case, although the reflectivity is high, the finer roll roughness shows a further effect of improving the reflectivity. I understand that Further, it is confirmed that the bending processability is inferior due to the unevenness of the roll roughness transfer. For this reason, it is preferable to implement the roll roughness at the time of rolling with a roll having a Ra of 0.15 μm or less, and more preferably with a roll of 0.05 μm or less.
Furthermore, Reference Example 5 and Reference Example 6 are examples in which heat treatment (low-temperature annealing) is performed after plating and rolling, and each simulates Patent Document 3, but the thermal history due to low-temperature annealing was excessive. The overall reflectivity decreased. Moreover, since the rolling roll roughness is not considered in the conventional technique as described in Patent Document 3, it can be seen that the reflectance is not sufficiently improved and the bending workability is also inferior. Thus, it can be seen that the present invention cannot be easily achieved simply by developing the conventional technology. For this reason, when performing heat processing after rolling, it turns out that it is necessary to apply, fully considering reflectance.

Example 3
As Example 3, a substrate: C14410 (Cu-0.15Sn-0.01P, manufactured by Furukawa Electric Co., Ltd., trade name: EFTEC-3), a width of 30 mm, and a thickness of 0.3 mm was prepared. After performing the pre-treatment shown below, the following matte silver (Ag) plating or bright silver (Ag-Se alloy) plating is applied without forming an intermediate layer, and a 6 μm thick plating film is formed. Obtained.
In either case, pretreatment through electrolytic degreasing and pickling steps was performed. Also, before each silver or silver alloy plating, the silver strike plating is performed, and the outermost layer plating thickness is the thickness after rolling including the silver strike plating thickness (thickness at the position on the bottom of the formed recess). )).

The pretreatment conditions in Example 3 are shown below.
(Pretreatment conditions)
[Cathode 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 [Ag strike plating] coating thickness 0.01 μm
Plating solution: KAg (CN) ₂ 5 g / liter, KCN 60 g / liter Plating condition: current density 2 A / dm ² , plating time 4 seconds, temperature 25 ° C.

The liquid composition and plating conditions for the reflective layer plating used in Example 3 are shown below.
(Reflective layer plating conditions)
[Ag plating]: Matte silver 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.
[Ag-Se alloy plating]: Bright silver plating plating solution: KCN 150 g / liter, K ₂ CO ₃ 15 g / liter, KAg [CN] ₂ 75 g / liter, Na ₂ O ₃ Se · 5H ₂ O 5 g / liter : Current density 2A / dm ² , temperature 50 ° C

Next, the matte silver-plated product obtained in the above process is rolled into the initial plate thickness using a work roll having a roll roughness Ra≈0.04 μm using a 6-high mill as a reflective layer forming treatment. A reflecting layer-formed product having a rate of 50%, that is, a plate thickness (lead frame thickness after rolling) of 0.15 mm was obtained. Then, by pressing, the depth of the recess, the bending radius (the bending radius at the location corresponding to R1 and R2 in FIG. 1), the angle between the bottom perpendicular to the recess and the side surface, the bottom area of the recess, and the bottom of the recess The thickness of the lead frame was adjusted to form a recess. However, the bending radius R was applied so as to be the same in any bending portion. The thickness of the formed reflective layer is reduced by the processing rate with respect to the initial coating thickness. Therefore, when the processing rate is 50%, the initial coating thickness is 50%. The layer thickness was all 3 μm. Thereafter, a lead frame for the optical semiconductor device of the invention example and the reference example was obtained through a press process for forming a lead frame, that is, press processing for punching outside the concave portion (optical semiconductor device mounting position).
In addition, with respect to the same conventional example 2 formed in Example 1 and Example 2, which is the bright silver plated product obtained in the above process, the conventional example 2 in which the reflective layer is formed by plating after forming the recess. A lead frame for an optical semiconductor device was fabricated and compared.
Further, as Comparative Example 1, after forming the reflective layer by the same matte silver plating and rolling as described above, the pressing step for forming the lead frame without forming the concave portion, that is, outside the optical semiconductor device mounting position. A lead frame for an optical semiconductor device obtained through press working for punching was prepared and compared with a product having a recess.

(Evaluation method)
The lead frames of the invention examples, reference examples and conventional examples obtained as described above were evaluated according to the following tests and standards.
(3A) Measurement of reflectivity ratio: In a spectrophotometer (V660 (trade name, manufactured by JASCO Corporation)), barium sulfate is subjected to a pressing process for lead frame formation, that is, the punching process. Continuous measurement was performed on the reflectance in the entire area of the concave portion (location corresponding to 4 in FIG. 1, that is, the entire area of the bottom surface 2a and the side surface 2b) over the wavelength range of 300 nm to 800 nm when the total reflectance of the standard plate was 100%. . Among these, the total reflectance (%) at a wavelength of 450 nm, which is a visible light region, is the sum of the measured bottom area (area 2a in FIG. 1) and inner surface (area 2b in FIG. 1), The reflectance ratio multiplied by the inner surface area (mm ² ) of the recess (total reflectance / surface area inside the recess;% / mm ² ) was calculated, and the reflectance ratio after bright plating in Conventional Example 2 was 1.00 (% / mm ² ). That is, if this value is 1 or more, it means that the reflectance is higher than the conventional example and the light extraction efficiency is high.
(3B) Bending crack resistance: In a bending part (location corresponding to R1, R1′R2, R2 ′ in FIG. 1) generated by forming a recess, a microscope (VH-8000 (trade name, Keyence Corporation) is used. ))), And the presence or absence of bending cracks that expose the substrate is investigated, and those that do not generate cracks are marked as “excellent”, and they are wrinkled but not cracked. "Good" if it is "Good", "Fair" if it is slightly cracked but the base is not exposed, and "No" if it is cracked and the base is exposed Represented by “x”. “Available” or higher was regarded as a practical level.
The results are shown in Table 4.

From the results of Table 4, in Comparative Example 1 in which no recess was formed, a large number of sliding scratches were generated by the pressing process, which is a punching process when forming the lead frame, and the reflectance ratio was greatly reduced. For this reason, although the initial reflectance before being subjected to the press working for forming the lead frame is high, the reflectance ratio after being subjected to the press working for forming the lead frame is smaller than that of the conventional example 2. I understand that As a result, it can be seen that, by forming the recess according to the present invention, sliding scratches in the vicinity of the optical semiconductor element mounting portion are significantly suppressed, and the reflection efficiency of the formed reflective layer can be maintained to the maximum.
Further, from the results in Table 4, in Reference Example 7 in which the maximum depth of the formed recess is three times or more the thickness of the lead frame, cracks occurred in the bent portion and the reflectance ratio was 1. It can be seen that the reflectance of light is not as good as that of Invention Example 39 under the same conditions except that the depth is 05 or less than 3 times the thickness of the lead frame. On the other hand, in Reference Example 8 where the maximum depth of the recess is less than 0.5 times the thickness of the lead frame, the reflectance ratio is not improved, the reflection efficiency is not so high, and the light extraction efficiency It turns out that there is no change compared with the conventional product. As a result, the maximum depth of the recess to be formed is at least 0.5 times the thickness of the lead frame, at most 3 times the thickness of the lead frame, more preferably 2 times or less, It can be seen that the lead frame for an optical semiconductor device can be formed without causing cracks in the bent portion, and the light extraction efficiency is high.
Moreover, it turns out that the bending crack can be preferably suppressed by making the bending radius in the bending process of the location in which the recessed part was formed into 5 times or less of the thickness of a lead frame.
Furthermore, as a result of Table 4, in Reference Example 9, the angle (angle formed by the bottom perpendicular to the concave portion and the side surface of the concave portion) is 0 °, so that the light extraction efficiency is not improved so much. It can be seen that cracks have occurred in. From this, from the viewpoint of improving the bending workability and the reflection efficiency, the angle formed by the bottom surface and the side surface of the recess is preferably 10 ° to 60 ° from the perpendicular to the bottom surface, and more preferably 20 ° to 45 °. It can be seen that this is preferable, and in this case, a lead frame for an optical semiconductor device with high luminance can be provided.

1 Conductive substrate 2 Reflective layer (rolled layer)
3 Optical Semiconductor Element 4 Recess 5 Bonding Wire 6 Press End after Lead Frame Formation (Exposed Portion of Conductive Base)
7 Angle between bottom surface perpendicular to recess and side surface 8 Intermediate layer 9 Mold resin 10 Sealing resin

Claims (9)

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 consisting of silver or a silver alloy is the rolling deformation tissue, rolling surfaces of the lead frame for the optical semiconductor device, have a concave portion for mounting the optical semiconductor element , reflectance at the concave portion is 75% or more reflectivity at a wavelength of 375 nm, 85% or more reflectivity at a wavelength of 450 nm, the reflectance at a wavelength of 600nm is characterized der Rukoto 90%, light Lead frame for semiconductor devices.
  2. The lead frame for an optical semiconductor device according to claim 1, wherein the maximum depth of the recess is 0.5 to 3 times the thickness of the lead frame after the rolling process.   3. The optical semiconductor device according to claim 1, wherein a reduction rate of the thickness of the lead frame after the rolling process at the bottom of the recess is 10% or less of the thickness before the formation of the recess. Lead frame.   The silver or silver alloy forming the reflective layer is silver, silver-tin alloy, silver-indium alloy, silver-rhodium alloy, silver-ruthenium alloy, silver-gold alloy, silver-palladium alloy, silver-nickel alloy, silver The lead frame for optical semiconductor devices according to any one of claims 1 to 3, wherein the lead frame is a selenium alloy, a silver-antimony alloy, or a silver-platinum alloy.   5. A method of manufacturing a lead frame for a semiconductor device according to claim 1, wherein silver or silver is applied to a region on the outermost surface of the conductive substrate that reflects at least light emitted from an optical semiconductor element. A structure in which a layer made of a silver alloy is formed by any one of an electroplating method, an electroless plating method, or a sputtering method, and a rolling process is performed, and at least a surface of a plated structure made of silver or a silver alloy is rolled. Forming a reflective layer on the rolled surface of the lead frame for an optical semiconductor device after the reflective layer is formed, and forming a recess by a pressing method at a place where the optical semiconductor element is mounted. A step of performing a punching process on the outside of the concave part at the same time as the formation of the concave part or in a separate process, and exposing the conductive substrate at the punched part. The symptom, method for fabricating a lead for an optical semiconductor device frame.   6. The method for manufacturing a lead frame for an optical semiconductor device according to claim 5, wherein a rolling rate for forming the reflective layer is 1% or more and 80% or less.   The lead for an optical semiconductor device according to claim 5 or 6, wherein an arithmetic average height Ra of a rolling roll used for rolling to form the reflective layer is 0.001 to 0.15 µm. Manufacturing method of the frame.   An optical semiconductor device, wherein an optical semiconductor element is mounted on the lead frame for an optical semiconductor device according to claim 1.   9. The optical semiconductor device according to claim 8, wherein an emission wavelength of the optical semiconductor element is 340 nm to 800 nm.

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