JP2011129658A - Lead frame for optical semiconductor device, method for manufacturing the same, and optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead frame having high reflectance between an ultraviolet region and a near-infrared region, good wire bonding performance and excellent corrosion resistance, and a method for manufacturing the lead frame. <P>SOLUTION: A lead frame has an outermost surface layer, which is formed of either gold, palladium, platinum or an alloy thereof, at least in a portion subjected to wire bonding, in an upper layer of a reflection layer formed of rhodium or an rhodium alloy on a conductive substrate. By forming the outermost surface layer to have a thickness of 0.001-0.05 μm, a lead frame for an optical semiconductor device can be provided, wherein the lead frame is excellent in light reflectance, also has good corrosion resistance, and achieves further improved reliability in wire bonding performance. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

The lead frame for optical semiconductor devices is, for example, an LED (Light Emitting D).
It is widely used as a constituent member of various display / illumination light sources using optical semiconductor elements (light-emitting elements) such as iode 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 reflection material of the lead frame has a high reflectance in the entire visible light wavelength range (400 to 700 nm) (for example, a reflectance with respect to a reference substance such as barium sulfate or aluminum oxide). 80% or more). In recent years, LED elements have also been used as light sources for measuring / analyzing instruments using ultraviolet rays, and the reflective material is required to have a high reflectance even in the near ultraviolet region (wavelength of 340 to 400 nm). It is coming.

As a method for realizing an LED that emits white light, red (R), green (G), blue (B
) A method of arranging three chips that emit all colors, a method of using a sealing resin in which a yellow phosphor is dispersed in a blue LED chip, and a red and green LED chip that emits wavelengths from the ultraviolet to the near ultraviolet region, respectively. The method using a sealing resin in which a blue phosphor is dispersed is roughly divided into three main methods.
Conventionally, a method using a sealing resin in which a yellow phosphor is dispersed in a blue chip has been the mainstream. However, this method has recently been changed to a light emission wavelength band from the viewpoint that the color rendering property of the red system is particularly insufficient. A technique using an LED chip including an ultraviolet region has attracted attention.

In response to such demands, a layer made of silver or a silver alloy (in particular, for the purpose of improving the light reflectance in the visible light region (hereinafter referred to as reflectance) on the lead frame on which the LED element is mounted (
Many films are formed. A silver film is known to have a high reflectance in the visible light region. For example, as disclosed in Patent Document 1, it is known to form a silver plating layer on a reflective surface.

It is also known to use a metal other than silver as the reflective layer. For example, a lead frame whose outermost surface is coated with palladium (Pd) as shown in Patent Document 2 has been studied, and solderability is improved. Therefore, a lead frame in which a gold coating layer is provided on a palladium layer as shown in Patent Document 3 has been studied.

Further, a lead frame coated with rhodium (Rh) having a relatively good reflectivity from the ultraviolet region to the near infrared region has been studied. For example, a lead frame having a three-layer plating structure as shown in Patent Document 4, A lead frame is proposed in which the first layer is Ni, the second layer is palladium or a palladium alloy, and the outermost surface is coated with rhodium.

Japanese Patent Laid-Open No. 61-148883 JP 59-168659 A Japanese Patent No. 2543619 JP 2005-129970 A

However, the lead frames of each patent document have the following problems. For example,
In the technique described in Patent Document 1, the reflection layer in the optical semiconductor device turns black, and the reflectance in the visible light region is 1.
There is a case where a phenomenon of decreasing to near 0% may occur. This phenomenon occurs when there is a slight gap between the sealing resin and the lead frame, sulfur components in the atmosphere, halides in the flux residue, etc. enter the lead frame, and the silver on the lead frame surface becomes silver sulfide or It is thought to be caused by the fact that it becomes a silver halide compound and changes its color to black.

In the technique described in Patent Document 2, long-term reliability is superior to that of Silver in Patent Document 1, while palladium on the outermost surface has a reflectivity of about 35 to 45% in the ultraviolet region to the near ultraviolet region, The reflectance in the visible light region is about 45 to 65%, and the reflectance is low, but the reflectance is low. In the technique described in Patent Document 3, for example, the reflectance when a gold plating of 0.02 μm is applied to an upper layer of 0.01 μm of palladium plating is 70% or more at a wavelength of 600 to 800 nm, but is reflected at the short wavelength side. The reflectance is low and the reflectance at a wavelength of 400 nm is about 30%, and other techniques are required to increase the reflectance of the lead frame.

Moreover, in the technique described in Patent Document 4, when Rh is formed on the outermost layer, the reflectance at a wavelength of 300 to 340 nm in the ultraviolet region to the near ultraviolet region is improved more than Pd and Au, and about While it has been increased to 50% or more, it has been found that there is a problem of poor bonding with a gold bonding wire used to ensure electrical continuity with the LED chip. Although this detailed factor is unknown, Au and Rh do not form a compound near room temperature (25 ° C.) when viewed from the phase diagram, and thus it is considered that wire bonding is difficult.

Therefore, the present invention provides a lead frame for an optical semiconductor device used for an LED, photocoupler, photointerrupter, etc., having a good reflectivity from the ultraviolet region to the near infrared region, a good wire bonding property, a corrosion resistance and An object of the present invention is to provide a lead frame excellent in long-term reliability and a manufacturing method thereof.

As a result of conducting sincerity studies in view of the above problems, a lead frame for an optical semiconductor device in which a layer made of rhodium or a rhodium alloy is formed as a light reflecting layer on a conductive substrate, and further, gold, palladium, Thickness 0.001-0.05 made of platinum or an alloy thereof
By covering at least a portion to which wire bonding is performed with a μm metal layer, it has excellent reflectivity for light from the ultraviolet region to the near infrared region, specifically, a wavelength of 300 to 800 nm, and has good corrosion resistance, and The present inventors have found that a lead frame for a semiconductor device having excellent wire bonding properties can be obtained, and have reached the present invention based on this finding.

That is, the said subject is solved by the following means.
(1) A lead frame for an optical semiconductor device in which a reflective layer made of rhodium or a rhodium alloy is formed on a conductive substrate, wherein gold, palladium, platinum or an alloy thereof is formed on at least a part of the surface of the reflective layer A lead frame for an optical semiconductor device, wherein an outermost layer having a thickness of 0.001 to 0.05 μm is formed.
(2) The lead frame for an optical semiconductor device according to (1), wherein the reflective layer has a thickness of 0.005 to 0.5 μm.
(3) Rhodium or rhodium alloy forming the reflective layer is rhodium, rhodium-tin alloy, rhodium-copper alloy, rhodium-cobalt alloy, rhodium-silver alloy, rhodium-aluminum alloy, rhodium-indium alloy, rhodium-iridium. The optical semiconductor device according to (1) or (2), comprising a material selected from the group consisting of an alloy, a rhodium-ruthenium alloy, a rhodium-palladium alloy, a rhodium-nickel alloy, and a rhodium-platinum alloy. Lead frame.
(4) One or more intermediate layers are provided between the conductive substrate and the reflective layer, and the intermediate layer is made of nickel or nickel alloy, cobalt or cobalt alloy, copper or copper alloy, palladium or palladium. The lead frame for optical semiconductor devices according to any one of (1) to (3), wherein the lead frame is made of a metal or alloy selected from a group of alloys.
(5) When the intermediate layer contains nickel or a nickel alloy, cobalt or a cobalt alloy, copper or a copper alloy, the thickness of the layer composed of these components is 0.2 to 2.0 μm in total. The lead frame for optical semiconductors according to (4).
(6) When said intermediate | middle layer contains palladium or a palladium alloy, the thickness of the layer which consists of said palladium or palladium alloy is 0.005-0.2 micrometer in total, It is characterized by the above-mentioned. Lead frame for optical semiconductors.
(7) An optical semiconductor device comprising the optical semiconductor device lead frame according to any one of (1) to (6) above and an optical semiconductor element, and a portion where wire bonding is performed and An optical semiconductor device, wherein the outermost layer is provided in the vicinity.
(8) The optical semiconductor device according to (7), wherein the reflective layer and the outermost layer are provided in the vicinity of a place where the optical semiconductor element is mounted.

According to the present invention, the reflectance in the entire wavelength range of 300 to 800 nm exhibits excellent reflection characteristics of at least 50% immediately after formation or after an environmental test, and the reflectance does not decrease with time. An optical semiconductor lead frame having excellent long-term reliability can be obtained. Furthermore, a lead frame for an optical semiconductor device can be obtained in which the wire bonding property, which is insufficient with rhodium or a rhodium alloy, is remarkably improved.
As a result, although the initial reflectivity is not as high as that of silver or silver alloys, the decrease in reflectivity during long-term use was remarkable due to sulfur discoloration in silver, whereas in the present invention, the lead frame has excellent corrosion resistance. Therefore, it can be suitably used as a lead frame for optical semiconductor devices having excellent long-term reliability. In addition, the conventional technology can improve the reflectance from about 30% especially in the short wavelength region to 50% or more, and the conventional rhodium is only formed on the outermost layer and the bonding property is difficult. It has a greatly improved effect.

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 a schematic sectional drawing of 5th Embodiment of the lead frame for optical semiconductor devices which concerns on this invention.

An embodiment of the present invention will be described.
The lead frame of the present invention has an outermost layer formed of gold, palladium, platinum, or an alloy thereof on an upper surface of a reflective layer made of rhodium or a rhodium alloy on a conductive substrate at least at a place where wire bonding is performed. is doing. The thickness of the outermost layer is 0.001 to 0.0
5 μm. If the thickness of the outermost layer is less than 0.001 μm, it is not preferable because sufficient wire bonding strength cannot be secured. On the other hand, if the thickness of the outermost layer is larger than 0.05 μm, not only the effect of improving the wire bonding property is saturated, but also the amount of noble metal used as the material of the outermost layer is increased and it takes time to cover it. Is not preferable. The thickness of the outermost layer is 0
. If it is thicker than 05 μm, the amount of light reaching the reflective layer will be greatly reduced, and the reflectivity of the outermost layer will be inferior to that of the reflective layer, so the reflectivity of rhodium or rhodium alloy used as the reflective layer will be effective. Therefore, even when the outermost layer is formed on the surface of the reflective layer, the thickness needs to be 0.05 μm or less. In order to minimize the decrease in reflectivity and improve the wire bonding property, 0.003 to 0.00 is preferable.
The thickness may be 03 μm, more preferably 0.005 to 0.02 μm.

Further, the purity of the metal (gold, palladium or platinum) or an alloy thereof forming the outermost layer is preferably 90% or more, more preferably 99% or more, thereby further improving the reliability of the wire bonding property. Can do. This is because the heat resistance temperature of the sealing resin is about 1 when the LED chip is to be bonded to the lead frame with a gold wire, for example.
In view of the fact that a resin of about 70 ° C. is often used, the temperature during wire bonding may be about 150 ° C. in the LED manufacturing process, but the purity of the metal forming the outermost layer is 90% or more. Even if bonding is performed at this temperature, connection reliability can be improved. On the other hand, when the purity of the metal forming the outermost layer is less than 90%, the bonding strength at the time of wire bonding is insufficient, the number of wire bonding errors increases, and the production efficiency decreases. May occur. When these metal components are alloys, the total component purity of gold, palladium, or platinum may be 90% or more, more preferably 99% or more. For example, Au (gold) -50% Pt ( Good wire bonding properties can be obtained even with platinum.

As the conductive substrate of the optical semiconductor device lead frame of the present invention, for example, copper or copper alloy, iron or iron alloy, aluminum or aluminum alloy, etc. are preferably used.
Among the substrates, examples of copper alloys include CDA (Copper Development).
As an example of a standard alloy, C19400 (Cu-Fe alloy material:
For example, Cu-2.3Fe-0.03P-0.15Zn), C26000 (brass: Cu-
30Zn), C26800 (brass: Cu-35Zn), C52100 (phosphor bronze: Cu-)
8Sn-P) and C77000 (white and white: Cu-18Ni-27Zn). Also, CDA standard alloy C14410 (Cu-0.15Sn: EFTE manufactured by Furukawa Electric Co., Ltd.)
C-3), C18045 (Cu-0.3Cr-0.25Sn-0.2Zn alloy: EFTEC-64T manufactured by the same company), C52180 (Cu-8Sn-0.1Fe-0.05Ni-0.
04P: F5218 manufactured by the same company, C70250 (Cu-3.0Ni-0.65Si-0.1)
5Mg: EFTEC-7005) manufactured by the company is also a suitable example.
Moreover, as an example of an iron alloy among the substrates, Japanese Industrial Standards (JIS G 4305: 20
05) Specified stainless steel (SUS301, SUS304, SUS401), Fe-N
Examples include 42 alloy (Fe-42% Ni) which is an i alloy.
Among the substrates, examples of aluminum alloys include Japanese Industrial Standards (JIS H 400).
0: 2006 etc.) and A1100, A2014, A3003, A5052 and the like.

It is easy to form the reflective layer and the outermost layer film on these substrates, and a lead frame with good productivity can be provided. In addition, the lead frame based on these metals has excellent heat dissipation characteristics, and heat energy generated when the light emitter emits light can be smoothly discharged to the outside through the lead frame. Long life and long-term stabilization of reflectance characteristics are expected. This depends on the conductivity of the substrate, for example 10% I
ACS (International Annealed Copper Standard)
rd) or more is preferable, and 50% IACS or more is more preferable.
Iron alloy SUS304, etc. and 42 alloy are generally less than 10% IACS, but suitable for applications that require strength as a lead frame, applications that do not require strong heat dissipation, and general-purpose LED applications. Can be used.

The plate thickness and plate width of the conductive substrate are not particularly limited, but the lead frame size in the LED is generally 0.05 to 1.0 mm and about 10 to 200 mm.
The lead frame for an optical semiconductor device of the present invention satisfies various characteristics at least in the above size.

In the lead frame for an optical semiconductor device of the present invention, the long-term reliability of the light reflectance can be ensured by setting the thickness of the reflective layer made of rhodium or rhodium alloy to 0.005 μm or more. If the thickness of the reflective layer is too thick, the effect of long-term reliability is saturated, and cracking is likely to occur during pressing. Therefore, the thickness of the reflective layer is preferably 0.5 μm or less. The thickness of the reflective layer is more preferably used in the range of 0.01 to 0.2 μm from the viewpoint of characteristics and production cost.

The rhodium or rhodium alloy forming the reflective layer in the optical semiconductor device lead frame of the present invention is rhodium, rhodium-tin alloy, rhodium-copper alloy, rhodium-cobalt alloy, rhodium-silver alloy, rhodium-aluminum alloy, Rhodium-indium alloy,
By comprising a material selected from the group of rhodium-iridium alloy, rhodium-ruthenium alloy, rhodium-palladium alloy, rhodium-nickel alloy, rhodium-platinum alloy,
A lead frame with good reflectivity and good productivity can be obtained, but rhodium is preferably used from the viewpoint of improving reflectivity.

The lead frame for an optical semiconductor device according to the present invention includes nickel, a nickel alloy, cobalt, a cobalt alloy, copper, a copper alloy, palladium, and a palladium alloy between the conductive substrate and the reflective layer made of rhodium or rhodium alloy. By forming at least one intermediate layer made of a metal or alloy selected from the group, the material constituting the conductive substrate diffuses into the reflective layer due to heat generated when the light emitting element emits light. Therefore, the deterioration of the reflectance characteristic due to the light is prevented, and the reflectance characteristic becomes stable over a long period of time. Since the long-term reliability is improved by forming the intermediate layer, it is possible to form the reflective layer relatively thin with the thickness within the range of the present invention. In addition, the adhesion between the substrate and the reflective layer is improved.

Here, the thickness of the intermediate layer is determined in consideration of pressability, heat resistance, productivity, and the like. When the intermediate layer contains nickel or nickel alloy, cobalt or cobalt alloy, copper or copper alloy, the total thickness (total thickness) of the intermediate layer composed of these components is 0.2 to 2.0 μm. More preferably, 0.5 to 1.0 μm is preferable. Further, when the intermediate layer contains palladium or a palladium alloy, since the heat resistance is particularly excellent, the total thickness of the intermediate layer of these components is preferably 0.005 to 0.2 μm, more preferably 0.008 to 0.1 μm. When the intermediate layer is composed of two or more kinds of mixed layers, for example, when the intermediate layer is composed of two layers of a nickel layer and a palladium layer, the thickness of the nickel layer may be 0.2 to 2.0 μm. The thickness of 0.005 to 0.2 μm satisfies the required characteristics. Further, when palladium is formed as an intermediate layer, a further effect of corrosion resistance can be obtained by forming any layer of nickel, nickel alloy, cobalt, and cobalt alloy after forming the first layer. Although the intermediate layer can be formed of a plurality of layers, it is usually preferable to have two or less layers in consideration of productivity.

The lead frame for an optical semiconductor device of the present invention is preferably formed by a wet or dry plating method as a method that can be formed while suitably adjusting the coating thickness. As another forming method, there is a clad method, but a wet or dry plating method is preferable from the viewpoint of facilitating the control of the thickness on the order of submicrometers.

In addition, an optical semiconductor device formed by mounting an optical semiconductor element using the lead frame for an optical semiconductor device of the present invention seals at least the vicinity where the optical semiconductor element is mounted, that is, the light emitting element and its periphery. By using the lead frame of the present invention inside the formed resin, the reflectance characteristics can be obtained effectively at low cost. This is because the reflectance characteristic can be enhanced by forming a reflective layer made of rhodium or a rhodium alloy only in the vicinity of the portion including the mounting portion of the optical semiconductor element. In this case, the reflective layer made of rhodium or rhodium alloy may be partially formed, and may be formed by, for example, partial plating such as stripe plating or spot plating. Manufacturing a lead frame in which the reflective layer is partially formed can reduce the amount of metal used in the portion where the reflective layer is not formed, and thus can be an optical semiconductor device with less environmental load.

In addition, the optical semiconductor device of the present invention can provide an optical semiconductor device with good wire bonding performance at low cost by using a lead frame having an outermost layer formed only at a location where wire bonding is performed. This is because the outermost layer with excellent bonding properties is formed only at the places where wire bonding is performed, and the effect of improving the wire bonding properties without greatly reducing the reflectivity of the rhodium or rhodium alloy as the reflective layer Is obtained. In this case, on the entire upper surface of the lead frame or the upper part of the reflective layer formed partially,
For example, the outermost layer may be formed by partial plating such as stripe plating or spot plating.
Manufacturing a lead frame in which the outermost layer is partially formed can reduce the amount of metal used in a place where bonding properties are not required, so that an optical semiconductor device with less environmental load can be obtained.

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.

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 rhodium or rhodium alloy is formed on a conductive substrate 1, and an outermost layer 3 made of gold, palladium or platinum is formed on the upper layer of the reflective layer 2, An optical semiconductor element 4 is mounted on a part of the optical semiconductor element 4, and wire bonding 5 is applied between the outermost layer 3 and the optical semiconductor element 4. In the lead frame of this embodiment, the thickness of the outermost layer 3 is formed to be 0.001 to 0.05 μm, the reflectivity of rhodium or rhodium alloy is not substantially lowered, and the ultraviolet to near infrared region of 300 to 800 nm. The lead frame for an optical semiconductor device is excellent in reflection characteristics. In the schematic cross-sectional view, a state in which a circuit is formed in a broken line portion via an insulator or the like, and is suitably used for an optical semiconductor application is shown.

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 6 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 reflective layer 2 and the outermost layer 3 are formed in the portion where the optical semiconductor element 4 is mounted and in the vicinity thereof, that is, the portion including the inside of the resin formed by sealing the light emitting element and its periphery. Is shown. In the present invention, it is also possible to form the reflective layer 2 made of rhodium or rhodium alloy at least in a portion that contributes to light reflection.
In the present embodiment, the intermediate layer 6 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, the reflective layer 2 is formed only in a portion where the optical semiconductor element 4 is mounted and in the vicinity thereof, and the outermost layer 3 which is an upper layer thereof is formed only in the vicinity of the portion necessary for wire bonding. Is shown. As in this embodiment, the outermost layer 3 can be formed only in a portion where wire bonding is necessary.

FIG. 5 is a schematic sectional view of a fifth embodiment of a lead frame for an optical semiconductor device according to the present invention. In FIG. 5, the reflective layer 2 is formed only at and near the portion where the optical semiconductor element 4 is mounted, and the outermost layer 3 as the upper layer is formed on the entire surface including the portion necessary for wire bonding. It shows how it is. For this reason, for example, the outermost layer 3 is also formed in the region A in FIG. 5, and the outermost layer 3 is made of gold, palladium, platinum, or an alloy thereof. Therefore, when forming the optical semiconductor device, the region A Can be easily soldered. As in this embodiment, it is possible to form the outermost layer 3 entirely for the purpose of imparting solderability.

Although any method can be used for manufacturing the lead frame for a semiconductor device, the reflective layer 2,
The outermost layer 3 and the intermediate layer 6 are preferably formed by a wet or dry plating method.

Example 1
As Example 1, the conductive substrate shown in Table 1 having a thickness of 0.3 mm and a width of 50 mm was subjected to the following pretreatment and then subjected to the following electroplating treatment, whereby the invention shown in Table 1 was formed. Lead frames of Examples 1 to 68, Comparative Examples 1 and 2, and Conventional Examples 1 to 3 were produced. Among these, the invention examples 44 to 56 show that the intermediate layer has two layers and is configured in the order of “left / right” elements from the side close to the conductive substrate, and the coating thickness is also Shown in the same way.
Among the materials used as the conductive substrate, “C14410”, “C18045”, “C
19400 "," C26800 "," C52100 "," C52180 "," C7025 "
"0" and "C77000" represent a copper or copper alloy substrate, and the numerical value after C is the above-mentioned C
Indicates the type according to the DA standard.
“A1100”, “A2014”, “A3003”, and “A5052” represent aluminum or aluminum alloy substrates, respectively,
4000: 2006)).
“SUS304” and “42 alloy” represent an iron-based substrate, and “SUS304”
Is a stainless steel defined by Japanese Industrial Standard (JIS G 4305: 2005)
4% by mass, containing 8% by mass of nickel, the balance being iron-based alloy consisting of iron and inevitable impurities), “4
“2 alloy” represents an alloy containing 42% by mass of nickel and the balance being iron and inevitable impurities.
In addition, when the substrate is aluminum, it undergoes electrolytic degreasing, pickling, and zinc replacement treatment processes, and when it is stainless steel, it undergoes electrolytic degreasing and activation treatment steps.
The pre-processing which passed through the pickling process was performed.

The treatment solution composition and treatment conditions for each pretreatment and the plating solution composition and plating conditions for each plating used in Example 1 are shown below.
(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 substitution] Used when the substrate is aluminum Zinc substitution 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 [activation treatment] Used when the substrate is stainless steel Activation treatment solution: NiCl ₂ 40 g / liter, HCl 400 g / liter Processing conditions: 1.5 A / dm ² , temperature 40 ° C., processing time 10 seconds

(Intermediate layer plating conditions)
[Ni plating]
Plating _{solution: Ni (SO 3 NH 2)} 2 · 4H 2 O 500g / l, NiCl ₂ 30
g / liter, H ₃ BO ₃ 30 g / liter Plating condition: 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 / liter, H ₃ BO ₃ 30 g / liter Plating condition: current density 5 A / dm ² , temperature 50 ° C.
[Pd plating]
Plating solution: Pd (NH ₃ ) ₂ Cl ₂ 45 g / liter, NH ₄ OH 90 ml / liter, (NH ₄ ) ₂ SO ₄ 50 g / liter Plating condition: current density 1 A / dm ² , temperature 30 ° C.
[Pd—Ni plating] Pd-20% Ni plating plating solution: Pd (NH ₃ ) ₂ Cl ₂ 40 g / liter, NiSO ₄ 45 g / liter,
NH ₄ OH 90 ml / liter, (NH ₄ ) ₂ SO ₄ 50 g / liter Plating conditions: current density 1 A / dm ² , temperature 30 ° 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.

(Plating conditions for the reflective layer)
[Rh plating]
Plating solution: RHODEX (trade name, Nippon Electroplating Engineers Co., Ltd.)
Made)
Plating conditions: 1.3 A / dm ² , temperature 50 ° C.
[Ag plating] (Conventional example)
Plating solution: AgCN 50 g / liter, KCN 100 g / liter, K ₂ CO ₃ 3
0 g / liter plating conditions: current density 0.05 to 5 A / dm ² , temperature 30 ° C.
[Pd plating] (Conventional example)
Plating solution: Pd (NH ₃ ) ₂ Cl ₂ 45 g / liter, NH ₄ OH 90 ml / liter, (NH ₄ ) ₂ SO ₄ 50 g / liter Plating condition: current density 1 A / dm ² , temperature 30 ° C.

(Outermost layer plating conditions)
[Au plating]
Plating solution: KAu (CN) ₂ 14.6 g / liter, C ₆ H ₈ O ₇ 150 g / liter, K ₂ C ₆ H ₄ O ₇ 180 g / liter Plating condition: current density 1 A / dm ² , temperature 40 ° C.
[Au-Co plating] Au-0.3% Co plating solution: Autoronex GVC (trade name, manufactured by Nippon Electroplating Engineers Co., Ltd.)
Plating conditions: 5 A / dm ² , temperature 50 ° C.
[Pd plating]
Plating solution: Pd (NH ₃ ) ₂ Cl ₂ 45 g / liter, NH ₄ OH 90 ml / liter, (NH ₄ ) ₂ SO ₄ 50 g / liter Plating condition: current density 1 A / dm ² , temperature 30 ° C.
[Pt plating]
Plating solution: Pt (NO ₂ ) (NH ₃ ) ₂ 10 g / liter, NaNO ₂ 10 g / liter, NH ₄ NO ₃ 100 g / liter, NH ₃ 50 ml / liter Plating conditions: current density 5 A / dm ² , temperature 80 ° C.

(Plating thickness measurement)
X-ray fluorescence film thickness measurement system (SFT9400: product name, SII Nanotechnology (
Measurement was performed after preparing calibration curves of each plating thickness configuration with a collimator diameter of 2 mm.

(Evaluation methods)
The lead frames of the invention examples and comparative examples in Table 1 obtained as described above were evaluated according to the following tests and standards. The results are shown in Table 2.
(1) Reflectivity measurement: In a spectrophotometer (V660 (trade name, manufactured by JASCO Corp.)), continuous measurement was performed with a total reflectance of 300 nm to 800 nm. Of these, 300 nm,
Table 2 shows the total reflectance (%) at 340 nm, 400 nm, 600 nm, and 800 nm. As an evaluation standard, the reflectance is 50% in the entire wavelength range of 300 to 800 nm.
It means that a material exceeding 1 is considered to be good and can be used as a standard for an optical semiconductor lead frame.
(2) Wire bonding property (WB property): 10
After the point test, the joint strength is measured. If the value of (strength-3σ) is 49.0 mN or more, it is judged as “excellent” and marked with “」 ”in the table, 29.4 mN or more and less than 49.0 mN Is judged as “good” and marked with “◯” on the table, and those that are less than 29.4 mN but can be joined are judged as “possible” and marked with “△” on the table. Those that were not joined were determined to be “impossible” and “
The results are shown in Table 2 with “x” marks.
Wire bonder: SWB-FA-CUB-10, manufactured by Shinkawa Co., Ltd. Wire: 25 μm Gold wire Bonding temperature: 150 ° C.
Capillary: 1820-17-437GM
1st condition: 10 msec. , 45Bit, 45g
2nd condition: 10 msec. , 100bit, 130g
In addition, for the heat resistance evaluation, the same wire bonding property evaluation was also performed for those subjected to atmospheric heating at a temperature of 150 ° C. for 3 hours.
(3) Corrosion resistance: Rating number (RN) evaluation was performed about the sulfide state (described in JIS H8502), H ₂ S 3 ppm, and the corrosion state after 24 hours. The results are shown in Table 2.
Here, when the rating number is 9 or more, it means that the decrease in luminance is as small as several percent even when the optical semiconductor element (LED element) is lit for 10,000 hours, indicating that long-term reliability is high. .
(4) Reflectance measurement after sulfurization test: spectrophotometer (V-660 (trade name, manufactured by JASCO Corporation)
), Continuous measurement was carried out with the total reflectance ranging from 300 nm to 800 nm. Of these, at 400 nm, the value (%) comparing the reflectance before and after the sulfidation test is shown in Table 2.
(5) Bending workability: In the produced lead frame, a sample having a length of 30 mm and a width of 10 mm was cut out so that the length direction was parallel to the rolling direction, and bent by a press machine (manufactured by Nippon Automatic Machine Co., Ltd.). Bending workability was examined at a radius R = 0.5 mm. The maximum bending portion of the processed test piece was observed using a microscope (manufactured by Keyence Co., Ltd.) at a magnification of 175 to determine the bending workability. As a result of observing the maximum bending part, it is determined that the crack does not exist as “good” and the table is marked with “○”, and the one with wrinkles and minor cracks is determined as “good”. A "△" mark is attached to the mark, and those with large cracks are judged as "impossible" and "X" in the table
These are shown in Table 2 with marks. The bending workability was evaluated as “practical” or higher.

As is clear from these results, the upper layer of rhodium has a thickness of 0.001 to 0.05 μm.
Inventive Examples 1 to 68 coated with gold (Au—Co alloy is Au—0.3% Co alloy), palladium, and platinum, the reflectance at wavelengths of 300 nm to 800 nm is 50% at all wavelengths.
% Satisfied. In addition, all the wire bonding properties are good, but when rhodium of Conventional Example 2 is formed on the outermost layer, it is clear that wire bonding cannot be performed, and the wire bonding properties are greatly improved by the present invention. I understand that. In particular, as shown in Invention Examples 7 to 17, when the gold thickness is in the range of 0.001 to 0.02 μm, the reflectivity is all 60% or more in the region of 300 to 800 nm, and
It can be seen that the wire bonding property is excellent at 005 μm or more. For this reason, it is judged that the outermost layer thickness is preferably 0.003 to 0.03 μm, and more preferably 0.005 to 0.02 μm.
In addition, the inventive examples 1 to 68 have greatly improved corrosion resistance compared to the example in which the outermost surface described in the conventional example 1 is silver, and this result has a long-term reliability compared to the conventional silver-plated product. It suggests that there is.
Further, when comparing the inventive examples 1 to 68 with the example in which the outermost surface described in the conventional example 3 has an Au / Pd plating configuration, the inventive example has better reflectivity. The used optical semiconductor device (LED) is expected to have higher brightness than conventional products.
Furthermore, as described in Invention Examples 30 to 35, when the thickness of rhodium exceeds 0.005 μm,
In the region where the reflectance is 300 to 800 nm, all become 60% or more, and a further improvement in luminance is expected. On the other hand, when the thickness exceeds 0.5 μm, the effect of improving the reflectivity is saturated, but the pressability tends to be deteriorated.
Furthermore, as described in Invention Examples 24 to 29, when the intermediate layer is Ni, the corrosion resistance is further improved when the thickness is 0.2 μm or more, but the bending workability tends to deteriorate when the thickness exceeds 2.0 μm. I understand. On the other hand, as described in Invention Examples 36 to 43, when the intermediate layer is Pd, the thickness is 0.00.
When the thickness is 5 μm or more, the corrosion resistance is further improved, but when it exceeds 0.2 μm, the bending workability tends to be deteriorated. Further, as described in Invention Examples 44 to 56 in which these intermediate layers are two layers, the corrosion resistance is remarkably improved as compared with the case of each single layer, but when the Pd thickness exceeds 0.2 μm or Ni layer When the thickness exceeds 2.0 μm, it can be seen that the bending workability tends to deteriorate.

Further, as in Comparative Example 1, when the outermost layer thickness is thinner than the range of the present invention, it can be seen that the pull strength of wire bonding is lowered and the bonding property after the heat resistance test is poor.
In Comparative Example 2, it can be seen that when the outermost layer thickness is thicker than the range of the present invention, the wire bonding is maintained, but the reflectance at a wavelength of 300 to 400 nm is less than 50%.
From these facts, by using a lead frame manufactured in an appropriate coating thickness configuration range of the present invention for an optical semiconductor device, it has excellent reflectivity from 300 nm ultraviolet region to 800 nm near infrared region, and excellent long-term reliability. Obviously, an optical semiconductor device can be manufactured.

(Example 2)
As Example 2, Furukawa Electric Co., Ltd. having a plate thickness of 0.3 mm and a 30 mm square as a conductive substrate.
A copper alloy EFTEC-3 (Cu-0.15% Sn: equivalent to CDA standard alloy C14410) was used, and after the degreasing step and pickling step, Ni plating was applied to the entire surface as an intermediate layer.
. 5 μm, 0.02 μm Rh plating as the reflective layer, 0.01 Au plating as the outermost layer
A product formed to a thickness of μm was produced, and Invention Example 69 was produced as a full-surface plated product. On the other hand, the plating configuration was the same, and only the outermost Au plating coating portion was partially formed in a 3 mm square at the central portion of the substrate, and Invention Example 70 was manufactured as a partially plated product. In the partially plated product, an insulating masking tape (# 631S;
Masking was performed by pasting the product name, manufactured by Teraoka Seisakusho Co., Ltd. All pretreatment conditions and plating conditions were the same as in Example 1.

(Evaluation methods)
The following evaluation was performed about the full plating product and partial plating product which were obtained as mentioned above.
(1) Reflectivity measurement: In a spectrophotometer (V660 (trade name, manufactured by JASCO Corp.)), continuous measurement was performed with a total reflectance of 300 nm to 800 nm. The measurement area was a 20 mm square area at the center of the test piece. This is because the outermost layer of the overall plated product completely covers the reflectance measurement region, whereas the partially plated product has the outermost layer formed only in the 3 mm square portion, and the portion where the reflective layer is exposed It means that it exists.
Table 3 shows the total reflectance (%) at 300 nm, 340 nm, 400 nm, 600 nm, and 800 nm. As an evaluation standard, in the entire wavelength range of 300 to 800 nm,
It means that a material having a reflectance exceeding 50% is considered to be good and can be used as a standard for an optical semiconductor lead frame.
(2) Wire bonding property (WB property): 10
After the point test, the joint strength is measured. If the value of (strength-3σ) is 49.0 mN or more, it is judged as “excellent” and marked with “」 ”in the table, 29.4 mN or more and less than 49.0 mN Is judged as “good” and marked with “◯” on the table, and those that are less than 29.4 mN but can be joined are judged as “possible” and marked with “△” on the table. Those that were not joined were determined to be “impossible” and “
The results are shown in Table 3 with “x” marks. In addition, the wire bonding area | region was implemented in the part in which the outermost layer was formed in 1st side and 2nd side.
Wire bonder: SWB-FA-CUB-10, manufactured by Shinkawa Co., Ltd. Wire: 25 μm Gold wire Bonding temperature: 150 ° C.
Capillary: 1820-17-437GM
1st condition: 10 msec. , 45Bit, 45g
2nd condition: 10 msec. , 100bit, 130g
In addition, for the heat resistance evaluation, the same wire bonding property evaluation was carried out even for those subjected to atmospheric heating at a temperature of 150 ° C. for 3 hours.
(3) Outermost layer coverage: From the outermost layer plating area, the outermost layer noble metal coverage during the entire plating and partial plating was calculated. The coverage was expressed as a percentage of the area of the object to be plated with respect to the covering area of the outermost layer plating.

From these results, both of the inventive examples show a reflectance of 50% or more in all wavelength regions and excellent wire bonding properties, but the partially plated product is particularly 300-
It can be seen that the reflectance is slightly good in the wavelength region of 600 nm, which is close to or almost the same as that of pure Rh. This is the result of maximizing the reflectivity of the reflective layer by minimizing the decrease in reflectivity by forming the outermost layer only where it is necessary for wire bonding. The outermost layer is partially formed. It can be seen that this is more preferable. In addition, the precious metal coverage of the outermost layer is suppressed to 1/100 of the partially plated product, and as a result, the amount of precious metal used for the outermost layer can be reduced to 1/100, which can reduce the environmental burden. Recognize. From these facts, it can be seen that the lead frame in which only the portion requiring wire bonding is coated is more excellent in characteristics and manufacturing cost than the coating of the outermost layer on the entire surface.

DESCRIPTION OF SYMBOLS 1 Conductive base | substrate 2 Reflective layer 3 Outermost layer 4 Optical semiconductor element 5 Wire (bonding wire)
6 Middle class

Claims (8)

An optical semiconductor device lead frame in which a reflective layer made of rhodium or a rhodium alloy is formed on a conductive substrate, wherein at least a part of the surface of the reflective layer has a thickness made of gold, palladium, platinum or an alloy thereof. A lead frame for an optical semiconductor device, wherein an outermost layer having a thickness of 0.001 to 0.05 μm is formed. The lead frame for an optical semiconductor device according to claim 1, wherein the reflective layer has a thickness of 0.005 to 0.5 μm. The rhodium or rhodium alloy forming the reflective layer is rhodium, rhodium-tin alloy,
Rhodium-copper alloy, rhodium-cobalt alloy, rhodium-silver alloy, rhodium-aluminum alloy, rhodium-indium alloy, rhodium-iridium alloy, rhodium-ruthenium alloy, rhodium-palladium alloy, rhodium-nickel alloy, rhodium-platinum alloy The lead frame for optical semiconductor devices according to claim 1, wherein the lead frame is made of a material selected from a group. One or more intermediate layers are provided between the conductive substrate and the reflective layer, and the intermediate layer is made of nickel or nickel alloy, cobalt or cobalt alloy, copper or copper alloy, palladium or palladium alloy. Consisting of a metal or alloy selected from
The lead frame for optical semiconductor devices according to claim 1. When the intermediate layer contains nickel or a nickel alloy, cobalt or a cobalt alloy, copper or a copper alloy, the thickness of the layer made of these components is 0.2 to 2.0 μm in total, The lead frame for optical semiconductors according to claim 4. 5. The optical semiconductor according to claim 4, wherein when the intermediate layer includes palladium or a palladium alloy, a total thickness of the palladium or the palladium alloy is 0.005 to 0.2 μm. Lead frame. An optical semiconductor device comprising the lead frame for an optical semiconductor device according to any one of claims 1 to 6 and an optical semiconductor element, wherein the outermost layer is provided at a position where wire bonding is performed and in the vicinity thereof. An optical semiconductor device provided. 8. The optical semiconductor device according to claim 7, wherein the reflective layer and the outermost layer are provided in the vicinity of a place where the optical semiconductor element is mounted.

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