JP2011040668A - Optical semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical semiconductor device that is sealed with a sealing resin, and excellent in durability of reflection efficiency, especially, in a sulfur containing gas environment. <P>SOLUTION: In the optical semiconductor device constituted by connecting and mounting an electrode of an optical semiconductor element to a lead frame in a cup-shaped premolded package molded integrally with the lead frame through a conductive adhesive or conductive wires, and sealing the inside of the premolded package with the sealing resin, the lead frame is coated with silver plating having a surface of ≤0.3 μm in center-line average roughness (Ra) and ≤2 μm in 10-point average roughness (Rz). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical semiconductor device, and more particularly to an optical semiconductor device excellent in durability of reflection efficiency in a sulfur gas atmosphere.

As a resin composition for protecting a coating of an optical semiconductor element such as a light emitting diode (LED), the cured product is required to have transparency, and is generally an epoxy such as a bisphenol A type epoxy resin or an alicyclic epoxy resin. An epoxy resin composition comprising a resin and an acid anhydride curing agent is used (see Patent Document 1: Japanese Patent No. 3241338, Patent Document 2: Japanese Patent Laid-Open No. 7-25987). However, the cured product of such an epoxy resin composition has a problem that it has low light resistance or is colored due to light deterioration because of its low transmittance of light having a short wavelength.
And an organic compound containing at least two carbon-carbon double bonds reactive with SiH groups in one molecule, a silicon compound containing at least two SiH groups in one molecule, and a hydrosilylation catalyst. Addition-curable silicone resin compositions have also been proposed (see Patent Document 3: JP 2002-327126 A and Patent Document 4: JP 2002-338833 A). However, the cured product of such a silicone resin composition has a higher gas permeability than conventional epoxy resins, so that the sulfide gas existing in the storage environment and the use environment permeates, and the sulfide gas and the light emitting device package. As a result of the sulfurization reaction with the silver plating surface of the lead frame, the silver plating surface changes to black silver sulfide. As a result, the light reflection efficiency on the silver plating surface decreases and the light emission intensity of the light emitting element deteriorates over time. As a result, there is a problem that long-term reliability cannot be maintained.

Japanese Patent No. 3241338 JP 7-25987 A JP 2002-327126 A JP 2002-338833 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical semiconductor device excellent in durability of reflection efficiency in a sulfurized gas atmosphere.

In order to achieve the above object, the present inventors have intensively studied, and as a result, when the surface roughness of the silver-plated lead frame used in the optical semiconductor device exceeds a certain value, a silicone resin which is a sealing resin However, since the sealing resin and the silver plating surface adhere to each other with the void remaining, the optical semiconductor device is left in an atmosphere containing sulfur gas. In this case, the sulfurized gas permeates through the sealing resin and accumulates in voids existing at the interface between the silver plating surface and the sealing resin, causing a sulfurization reaction on the silver plating surface, and the sulfurization reaction causes the adhesion between the silver plating surface and the sealing resin. Has been found to spur further sulfurization reactions.
Therefore, in order to prevent such a sulfurization reaction, it is considered necessary to bond the interface between the sealing resin and the silver plating surface with no voids, and the surface roughness of the silver plating is calculated as the centerline average roughness. When the thickness (Ra) is 0.3 μm or less and the 10-point average roughness (Rz) is 2 μm or less, it has been found that an optical semiconductor device having excellent durability of reflection efficiency in a sulfur gas atmosphere can be obtained. The invention has been completed.

That is, the present invention provides the following optical semiconductor device.
Claim 1:
An electrode of the optical semiconductor element is connected to the lead frame via a conductive adhesive or a conductive wire inside a cup-shaped pre-molded package integrally formed so that the lead frame is arranged on the inner bottom surface, and the optical semiconductor element is An optical semiconductor device in which the inside of the pre-mold package is sealed with a sealing resin while the lead frame has a center line average roughness (Ra): 0.3 μm or less and a 10-point average roughness (Rz) An optical semiconductor device coated with silver plating having a surface of 2 μm or less.
Claim 2:
2. The optical semiconductor device according to claim 1, wherein a material of the lead frame is copper or a copper-based alloy.
Claim 3:
The optical semiconductor device according to claim 1, wherein the sealing resin is a cured product of an addition-curable silicone resin composition.

  ADVANTAGE OF THE INVENTION According to this invention, the optical semiconductor device excellent in durability of the reflection efficiency in sulfur gas atmosphere can be provided.

It is a schematic sectional drawing of the typical optical semiconductor device of this invention. It is sectional drawing showing the state of the interface of the sealing resin in the typical optical semiconductor device of this invention, and the silver plating surface of a lead frame. It is sectional drawing showing the state of the interface of the sealing resin and the silver plating surface of a Lee frame in the conventional typical optical semiconductor device.

Hereinafter, the present invention will be described in more detail.
FIG. 1 is a schematic sectional view of a typical optical semiconductor device 1 of the present invention.
The optical semiconductor device 1 of the present invention has an electrode of an optical semiconductor element 3 (not shown) formed in a cup-shaped pre-molded package 2 integrally formed so that a lead frame 6 is disposed on the inner bottom surface. The optical semiconductor device 1 is connected to the lead frame 6 via a wire 5 to mount the optical semiconductor element 3 and the inside of the premolded package 2 is sealed with a sealing resin 7. Center line average roughness (Ra): 0.3 μm or less and 10-point average roughness (Rz): coated with silver plating having a surface of 2 μm or less.
Here, Ra and Rz can be measured based on JIS B 0601 (1982).

  Thus, by covering the lead frame 6 with silver plating having a surface with Ra: 0.3 μm or less and Rz: 2 μm or less, the sealing resin 7 is interfaced with the silver plating surface as shown in FIG. Therefore, when such an optical semiconductor device 1 is left in an atmosphere in which a sulfide gas exists, even if the sulfide gas permeates the sealing resin 7, the sulfide gas should be accumulated. Since there is no gap at the interface between the silver plating surface and the sealing resin 7, the sulfidation reaction on the silver plating surface hardly occurs and the adhesion between the silver plating surface and the sealing resin 7 is not broken. Therefore, it is possible to obtain the optical semiconductor device 1 that is excellent in the durability of the reflection efficiency in the sulfurized gas atmosphere.

  On the other hand, when Ra and Rz on the surface of the silver plating exceed the above values, the sealing resin 7 cannot enter the irregular surface of the surface of the silver plating, and the sealing resin and silver remain in the state where the gap 8 remains as shown in FIG. If such an optical semiconductor device is left in an atmosphere containing sulfide gas because the plating surface is adhered, the sulfide gas passes through the sealing resin 7 and exists at the interface between the silver plating surface and the sealing resin 7. In the void 8 that accumulates, the silver plating surface undergoes a sulfurization reaction, and the adhesion between the silver plating surface and the sealing resin 7 is broken by the sulfuration reaction, which further accelerates the sulfurization reaction. In particular, such a sulfidation reaction on the surface of the silver plating is a reaction that produces black silver sulfide, so that the optical semiconductor device has a remarkably inferior reflection efficiency.

The smaller the Ra and Rz of the silver plating surface covering the lead frame 6, the more preferable. However, from the viewpoint of plating technology and surface processing, Ra: 0.03 μm or more and Rz: 0.1 μm or more are practical, respectively. is there.
In such silver plating having Ra and Rz, the lead frame 6 is subjected to silver plating treatment by electrolytic plating, electroless plating, hot-dip plating, vacuum deposition plating, etc. It is obtained by buffing with a polishing cloth soaked with an abrasive or the like and adjusting the value.

As the material of the main body of the lead frame 6, known copper, copper-based alloys such as Cu / Sn / Cu, Cu / Sn / Bi, and Sn / Ag / Cu are preferably used from the viewpoint of conductivity and cost.
For the conductive adhesive 4, a known silver paste is preferably used.

And the connection between the electrode (not shown) located on the lower surface of the optical semiconductor element 3 and the silver-plated lead frame 6 located immediately below is 150 to 300 ° C. for several minutes through the conductive adhesive 4 (silver paste). The connection between the counter electrode of the electrode (not shown) located on the upper surface of the optical semiconductor element 3 and the conductive wire 5 (made of Au, etc.) and the conductive wire 5 and the silver-plated lead frame 6 are connected in a few hours. Are connected by a known wire bonding method.
The inside of the pre-mold package 2 on which the optical semiconductor element 3 obtained in this way is mounted is finally sealed with a sealing resin 7 to form the optical semiconductor device 1.

Such a sealing resin 7 is particularly an addition containing (A) an organosilicon compound having a non-covalent double bond group, (B) an organohydrogenpolysiloxane, and (C) a platinum-based catalyst as essential components. A curable silicone resin composition is preferably used.
(A) component:
The component (A) includes the following general formula (1):
R ¹ R ² R ³ SiO— (R ⁴ R ⁵ SiO) _a — (R ⁶ R ⁷ SiO) _b —SiR ¹ R ² R ³ (1)
(In the formula, R ¹ represents a non-covalent double bond group-containing monovalent hydrocarbon group, and R ^{2 to} R ⁷ represent the same or different monovalent hydrocarbon groups, among which R ^{4 to} R ^7. Preferably represents a monovalent hydrocarbon group excluding an aliphatic unsaturated bond, and R ⁶ and / or R ⁷ represents an aromatic monovalent hydrocarbon group, and 0 ≦ a + b ≦ 500, preferably 10 ≦ a + b ≦ 500, 0 ≦ a ≦ 500, preferably 10 ≦ a ≦ 500, 0 ≦ b ≦ 250, preferably 0 ≦ b ≦ 150.
Can be used.

In this case, R ¹ has an aliphatic unsaturated bond represented by an alkenyl group having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, and R ^{2 to} R ⁷ have 1 to 20 carbon atoms, particularly 1 to 10 carbon atoms. Are preferably alkyl groups, alkenyl groups, aryl groups, aralkyl groups, etc., among which R ^{4 to} R ⁷ are preferably alkyl groups other than aliphatic unsaturated bonds such as alkenyl groups, An aryl group, an aralkyl group, etc. are mentioned. R ⁶ and / or R ⁷ is preferably an aromatic monovalent hydrocarbon group such as an aryl group having 6 to 12 carbon atoms such as a phenyl group or a tolyl group.

  The organopolysiloxane of the general formula (1) includes, for example, cyclic diorganopolysiloxanes such as cyclic dimethylpolysiloxane, cyclic diphenylpolysiloxane, and cyclic methylphenylpolysiloxane that constitute the main chain, and divinyltetramethyl that constitutes the terminal group. It can be obtained by alkali equilibration reaction with disiloxanes such as disiloxane, dimethyltetravinyldisiloxane, hexavinyldisiloxane, diphenyltetravinyldisiloxane, divinyltetraphenyldisiloxane, etc. Chlorine content is not contained.

（上記式において、ｋ，ｍは、０≦ｋ＋ｍ≦５００を満足する整数であり、好ましくは５≦ｋ＋ｍ≦２５０で、０≦ｍ／（ｋ＋ｍ）≦０．５を満足する整数である。） Specific examples of the organopolysiloxane of the general formula (1) include the following.

(In the above formula, k and m are integers satisfying 0 ≦ k + m ≦ 500, preferably 5 ≦ k + m ≦ 250, and integers satisfying 0 ≦ m / (k + m) ≦ 0.5.)

  The component (A) has a three-dimensional network structure including a trifunctional siloxane unit, a tetrafunctional siloxane unit, and the like as necessary in addition to the organopolysiloxane having the linear structure of the general formula (1). Organopolysiloxane can also be used in combination.

  The content of the non-covalent double bond group in the component (A) is 1 to 50 mol%, preferably 2 to 40 mol%, more preferably 5 to 30 mol% of all monovalent hydrocarbon groups. . If the content of the non-covalent double bond group is less than 1 mol%, a cured product cannot be obtained, and if it is more than 50 mol%, the mechanical properties may be deteriorated.

  Moreover, content of the aromatic group in (A) component is 0-95 mol% of all the monovalent hydrocarbon groups, Preferably it is 10-90 mol%, More preferably, it is 20-80 mol%. When an appropriate amount of the aromatic group is contained in the resin, there is an advantage that the mechanical properties are good and the production is easy. Another advantage is that the refractive index can be controlled by introducing an aromatic group.

(B) component:
As the component (B), an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule is used. Such an organohydrogenpolysiloxane acts as a crosslinking agent, and includes a SiH group in the component and a non-covalent double bond-containing group (typically an alkenyl group) such as a vinyl group in the component (A). Are cured to form a cured product.

  In addition, the organohydrogenpolysiloxane has an aromatic hydrocarbon group, thereby increasing compatibility when the organosilicon compound having a non-covalent double bond group as the component (A) has a high refractive index, A transparent cured product can be provided. Therefore, in the organohydrogenpolysiloxane of the component (B), the organohydrogenpolysiloxane having an aromatic monovalent hydrocarbon group can be included as part or all of the component (B).

  Further, in the organohydrogenpolysiloxane of the component (B), the organohydrogenpolysiloxane having a glycidyl structure can be included as a part or all of the component (B), and the organohydrogenpolysiloxane has a glycidyl structure. By having a containing group, a sealing resin composition for optical semiconductors having high adhesiveness to the substrate can be provided.

Examples of the organohydrogenpolysiloxane include, but are not limited to, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (dimethylhydrogen Siloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane, 1-glycidoxypropyl-1,3,5,7-tetramethylcyclotetrasiloxane, 1,5-glycidoxypropyl-1,3,5 7-tetramethylcyclotetrasiloxane, 1-glycidoxypropyl-5-trimethoxysilylethyl-1,3,5,7-tetramethylcyclotetrasiloxane, trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends Trimethylsiloxy group-blocked dimethylsiloxa・ Methyl hydrogensiloxane copolymer, dimethylpolysiloxane blocked with dimethylhydrogensiloxy at both ends, dimethylsiloxane blocked with dimethylhydrogensiloxy group at both ends ・ Methylhydrogensiloxane copolymer, methylhydrogensiloxane blocked at both ends with trimethylsiloxy group・ Diphenylsiloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane at both ends ・ Diphenylsiloxane ・ dimethylsiloxane copolymer, trimethoxysilane polymer, (CH ₃ ) ₂ HSiO _1/2 unit and SiO _4/2 unit And a copolymer composed of (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units, and (C ₆ H ₅ ) SiO _3/2 units.

Moreover, the organohydrogenpolysiloxane obtained using the unit shown by the following structure can also be used.

Examples of such organohydrogenpolysiloxanes include the following.

  The molecular structure of such an organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures, but the number of silicon atoms (or the degree of polymerization) in one molecule is 2. One or more, preferably 2 to 1,000, more preferably about 2 to 300 can be used.

  The compounding amount of such an organohydrogenpolysiloxane is such that the silicon atom-bonded hydrogen atom (SiH) in the component (B) per non-covalent double bond group (typically alkenyl group) in the component (A). It is preferable to include an amount sufficient to give 0.75 to 2.0 groups).

(C) component:
As the component (C), a platinum-based catalyst is used. Examples of the platinum-based catalyst include chloroplatinic acid, alcohol-modified chloroplatinic acid, platinum complexes having a chelate structure, and the like. These can be used alone or in combination of two or more.
The compounding amount of these catalyst components is a curing effective amount and may be a so-called catalyst amount, and is usually 0.1 to 0.1 parts by mass in terms of platinum group metal per 100 parts by mass of the total amount of the components (A) and (B). It is used in the range of 500 ppm, especially 0.5-100 ppm.

(D) Other ingredients:
The addition-curable silicone resin composition used in the present invention contains the above-described components (A) to (C) as essential components, and various silane coupling agents may be added thereto as necessary.
For example, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3- Glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, N-2 (amino Ethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxy Run, 3-aminopropyltriethoxysilane, N- phenyl-3-aminopropyl trimethoxysilane, and 3-mercaptopropyl trimethoxysilane, trimethoxysilane, tetramethoxysilane and oligomers thereof, and the like. These silane coupling agents can be used alone or in combination of two or more.
The blending amount of the silane coupling agent is preferably 10% by mass or less (0 to 10% by mass), particularly 5% by mass or less (0 to 5% by mass) of the entire composition.

  In addition, the addition curable silicone resin composition used in the present invention may include, for example, BHT or vitamin B as an antioxidant, or a known discoloration inhibitor as long as it does not deteriorate the performance of the optical semiconductor device. For example, organic phosphorus-based discoloration inhibitors, photodegradation inhibitors such as hindered amines, etc., reactive ethers such as vinyl ethers, vinyl amides, epoxy resins, oxetanes, allyl phthalates, vinyl adipates, etc. A sealing resin composition may be prepared by adding a reinforcing filler such as silica or precipitated silica, a flame retardant, a phosphor, an organic solvent, or the like. Moreover, you may color with a coloring component.

Preparation method of addition curable silicone resin composition:
The addition-curable silicone resin composition is prepared by stirring, dissolving, mixing, and dispersing the components (A) to (C) and the desired other component (D) at the same time or separately while applying heat treatment as necessary. Can be obtained.
Although the apparatus used for these operations is not particularly limited, a lykai machine equipped with a stirring and heating apparatus, a three roll, a ball mill, a planetary mixer, and the like can be used. Moreover, you may combine these apparatuses suitably.

  The addition curable silicone resin composition thus obtained is used for sealing an optical semiconductor device, and examples of the optical semiconductor element include LED, photodiode, CCD, CMOS, photocoupler, etc. It is effective for LED sealing.

  As a sealing method, a known method according to the type of the light-emitting element is adopted, and the curing conditions of the addition-curable silicone resin composition are in a temperature range from room temperature (20 to 30 ° C.) to about 200 ° C. Although a time range of about 10 seconds to several days can be adopted, it is preferable to set the time range from about 1 minute to about 10 hours at a temperature range of 80 to 180 ° C. from the viewpoint of curing quality, workability, and the like.

  The optical semiconductor device encapsulated with the cured product of the addition-curable silicone resin composition thus obtained is excellent in heat resistance, moisture resistance, and light resistance in combination with the silver-plated lead frame having the above surface roughness. As a result, it is possible to provide an optical semiconductor device excellent in durability of reflection efficiency without discoloring the surface of the silver plating that also serves as a reflector in a sulfur gas atmosphere.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to the following Example. In the following examples, parts indicate parts by mass.

[Example 1]
Silver plating as shown in FIG. 1 is performed by injection molding using a silver plating lead frame 6 having surface roughness (Ra, Rz) = (0.05 μm, 0.5 μm) and a thermoplastic resin manufactured by Solvay. A premold package 2 having a bottom surface with a concave cross section formed integrally with the lead frame 6 was produced.
Next, an InGaN semiconductor having a main emission peak of 460 nm is mounted as the LED chip 3 on the silver-plated lead frame 6 on the bottom surface of the pre-mold package 2, and both electrodes are connected to the respective silver via the silver paste 4 and the gold wire 5. It was connected to the plating lead frame 6 to obtain an LED device before resin sealing. In addition, the hardening conditions of a silver paste and the connection method (wire bonding method) of a gold wire followed the well-known method.
Furthermore, an organohydrogenpolysiloxane represented by the following formula (ii) is added to 100 parts of both-end vinyldimethylsiloxy-blocked dimethylpolysiloxane represented by the following formula (i) with respect to the vinyl group in the formula (ii): (ii) ) In the formula, the molar ratio of SiH groups is 1.5, and 0.05 parts of octyl alcohol-modified solution of chloroplatinic acid is added to this, and the mixture is well agitated, followed by addition-curable silicone resin composition. Was prepared, poured into the recesses of the LED device before resin sealing, cured at 150 ° C. for 4 hours, and sealed as a sealing resin 7 to complete the LED device 1.

（但し、Ｌ＝４５０）

(However, L = 450)

（但し、Ｌ＝１０、Ｍ＝８）

(However, L = 10, M = 8)

[Examples 2 and 3]
An LED device exactly as in Example 1 except that a silver-plated lead frame 6 having surface roughness (Ra, Rz) = (0.10 μm, 0.8 μm) and (0.2 μm, 1.5 μm) was used. 1 was completed. These were designated as Examples 2 and 3, respectively.

[Comparative Examples 1 and 2]
The LED device was fabricated in the same manner as in Example 1 except that a silver-plated lead frame having surface roughness (Ra, Rz) = (0.35 μm, 2.5 μm) and (0.5 μm, 3.5 μm) was used. Completed. These were designated as Comparative Examples 1 and 2, respectively.

The LED devices of Examples 1 to 3 and Comparative Examples 1 and 2 thus obtained were sealed in a hydrogen sulfide gas generation container (concentration: 30 ppm), left to stand, and turned on with a current of 25 mA. The appearance intensity of the substrate (lead frame) surface of each LED device was observed every 0, 10, 30, 50, and 100 hours, and the decay rate of the emission intensity with respect to the initial emission intensity was measured.
The results are shown in Table 1.

In Examples 1 to 3, even when left in a hydrogen sulfide gas generation container for 100 hours, the LED device substrate (silver-plated lead frame) was not blackened due to sulfuration, and the emission intensity was hardly reduced.
However, in Comparative Example 1, after standing for 10 hours, blackening due to sulfuration of the LED device substrate (silver-plated lead frame) was observed, and the emission intensity was reduced by 10%. Further, in Comparative Example 2 in which the surface roughness of the silver plating was rough, the light emission intensity decreased by 15% due to the sulfuration of the substrate after standing for 10 hours, and after 100 hours, the light emission intensity decreased to the initial light emission intensity of 64%.

DESCRIPTION OF SYMBOLS 1 Optical semiconductor device 2 Premold package 3 Optical semiconductor element 4 Conductive adhesive 5 Conductive wire 6 Lead frame (silver plated)
7 Sealing resin 8 Air gap

Claims (3)

  An electrode of the optical semiconductor element is connected to the lead frame via a conductive adhesive or a conductive wire inside a cup-shaped pre-molded package integrally formed so that the lead frame is arranged on the inner bottom surface, and the optical semiconductor element is An optical semiconductor device in which the inside of the pre-mold package is sealed with a sealing resin while the lead frame has a center line average roughness (Ra): 0.3 μm or less and a 10-point average roughness (Rz) An optical semiconductor device coated with silver plating having a surface of 2 μm or less.   2. The optical semiconductor device according to claim 1, wherein a material of the lead frame is copper or a copper-based alloy.   The optical semiconductor device according to claim 1, wherein the sealing resin is a cured product of an addition-curable silicone resin composition.

Images