JPH04222855A - Epoxy resin sealing material for photosemiconductor - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin sealing material for photosemiconductor having low linear expansion property, hygroscopic property and heat generation in curing and high transparency. CONSTITUTION:(A) 100 pts.wt. epoxy resin is blended with (B) 30-80 pts. wt. phenolic curing agent (e.g. phenol novolak resin) and 10-85 pts.wt. filler (e.g. globular glass, preferably consisting of barium borosilicate glass) having refractive index satisfying the formula [n (matrix) is refractive index of a cured product obtained by curing components except filler in all sealing materials; n (filler) is refractive index of filler].

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to photocouplers,
A device that simultaneously mounts a light receiving and emitting device inside an element such as a photointerrupter, and transmitting and receiving signals between the light receiving device and the light emitting device.
This invention relates to an epoxy resin encapsulating material that can inexpensively encapsulate optical semiconductors called "composite optical devices."

0002

2. Description of the Related Art Conventionally, there are the following photocouplers, for example. FIG. 3 shows the sealing structure of a conventional photocoupler. This photocoupler has a light emitting element 2a and a light receiving element 2b mounted on lead frames 1a and 1b, respectively. Light emitting element 2a
and the light receiving element 2b are arranged facing each other so that the light emitted from the light emitting element 2a effectively reaches the light receiving element 2b. The light emitting element 2a is a gallium-arsenic semiconductor and is weak against stress, so it is surrounded by transparent silicone gel (
Protected by covering with silicone potting) 3. These parts are sealed with a transfer-molded translucent resin 4. The translucent resin 4 has an epoxy resin, a phenolic curing agent, and a filler as main components, and has low linear expansion, low hygroscopicity, low curing heat generation, and the like. Around the translucent resin 4, furthermore,
It is protected by covering it with a normal black sealing material 5 and performing double molding.

0003

[Problems to be Solved by the Invention] However, the light-transmitting resin used in the conventional photocouplers mentioned above is
Since light is easily scattered and reflected at the interface between the matrix resin (resin component) and the filler,
With a thickness of m, a light transmittance of only about 20 to 23% can be obtained. Therefore, it is difficult for the signal light emitted from the light emitting element to effectively reach the light receiving element, so it is not possible to increase the distance between the light emitting element and the light receiving element. As a result, there was a problem in that the dielectric strength between the two electronic circuit systems deteriorated.

In view of these circumstances, it is an object of the present invention to provide an epoxy resin encapsulating material for optical semiconductors that has low linear expansion, low hygroscopicity, low curing heat generation, and is highly transparent. do.

[0005]

[Means for Solving the Problems] In order to solve the above problems, an epoxy resin encapsulating material for optical semiconductors according to each of the inventions of claims 1 to 3 contains an epoxy resin, a phenolic curing agent, and a filler. The sealing material is characterized in that the filler has a refractive index that satisfies the relationship of formula (I) below.

[0006]n(matrix)−0.02≦n(filler
)≦n(matrix)+0.07...(I
) [In the formula, n (matrix) represents the refractive index of a cured product obtained by curing components other than the filler among all the sealing materials, and n (filler) represents the refractive index of the filler. ] According to the invention of claim 2, glass is further contained as the filler.

[0007] According to the third aspect of the invention, furthermore, a spherical filler is used as the filler. Note that the refractive index is, for example, a numerical value commonly called nD. In addition, n (matrix) is, for example, room temperature (2
0°C). In order to solve the above problem, it is essential to increase the light transmittance, and the most effective means for this purpose is to match the refractive index of the filler in the composition with the refractive index of the matrix resin. be.

It is a well-known fact that if the refractive index can be perfectly matched, a cured product containing a filler can be made transparent. Since the temperature dependence of the refractive index is different from that of the inorganic filler (the temperature dependence of the organic material is greater), it is impossible to match the refractive index of the two, including the temperature change.

[0009] The inventors conducted research in view of the transparency and operating temperature range (for example, usually about 0 to 100°C) required for optical semiconductors, and found that as a filler,
They have discovered that by using a material with a refractive index that satisfies the above formula (I), transparency for optical semiconductors can be ensured over the entire range of approximately 0 to 100°C. In addition to the above-mentioned essential components, the sealing material of the present invention may contain a curing accelerator, a coupling agent, and other additives that function when dissolved in the matrix resin. Even when other components are added in addition to the essential components, it is essential that the refractive index of the filler falls within a range that satisfies the above formula (I). Further, even if a substance deteriorates transparency, it may be added in a small amount as long as it can ensure transparency for use in optical semiconductors.

[0010] The size etc. of the filler used in this invention include:
Although there are no particular limitations, it is preferable that the particle size and particle size distribution be those used as a filler for ordinary sealing materials, since the viscosity increases when the amount of filler is increased and bubbles are likely to occur. For example, an average particle size of 1 to 30 μm is preferred. If it is out of these ranges, there is a risk that the fluidity during molding may deteriorate or the gate during transfer molding may become clogged.

[0011] There are no particular restrictions on the shape of the filler, but spherical fillers are preferable to crushed ones. This is because, as shown in FIG. 1, when the spherical filler 6 is dispersed in the matrix resin 7, the probability that the incident light 8 exceeding the critical angle will be scattered (reflected) is small; As shown in , when the crushed filler 16 is dispersed in the matrix resin 7, there is a high probability that the incident light 8 exceeding the critical angle will be scattered (reflected), and even a small difference in refractive index will reduce the transparency. This is because there is a tendency to decrease. The spherical filler is preferably a true sphere, but it is usually a crushed filler (
(having a sharp tip) whose sharp part is rounded by a method called thermal spraying is also called spherical, and the effect of this invention is that
Higher than crushed ones.

[0012] In order to have the effects described above,
It is preferable that the refractive index of the constituent resin is about 1.61. Therefore, it is preferable to use barium borosilicate glass, lead borosilicate glass, or the like having a refractive index higher than that as the filler. Among these glasses,
In particular, those having a refractive index in the range of 1.53 to 1.68 are preferred.

To further explain the range of refractive indexes mentioned above, in order to fill the matrix resin with powder and obtain transparency, it is preferable that the refractive indexes of the two are the same, but if there is a difference between the two, the matrix resin The relationship of refractive index of resin<refractive index of filler makes it possible to achieve better transparency. Although the reason is unknown, it has been experimentally confirmed that the allowable range for optical semiconductors is the range expressed by the following formula (II). (Refractive index of matrix resin -0.02)
~(Refractive index of matrix resin +0.09


...(II) Now, the refractive index of the inorganic filler is 0 to 10
Although it does not change much at 0°C, the refractive index of the cured matrix resin at 100°C is 0.0 compared to that at 0°C.
About 2 times smaller. Therefore, the refractive index at 20°C of a cured product using all components other than the filler in the sealing material is n(
In the range of 0 to 100°C, the refractive index of the cured product is from n(matrix) to n(matr
ix) changes by about -0.02. The condition for satisfying the above-mentioned relational expression (II) over this entire temperature range is the above-mentioned relational expression (I).

[0014] As the curing agent for the epoxy resin used in this invention, a phenolic curing agent is essential. amine type,
Acid anhydride curing agents are not preferred because they have poor heat resistance and moisture resistance. Preferred examples of phenolic curing agents include:
For example, phenol novolak resin, cresol novolak resin, etc. can be mentioned. This invention includes:
As epoxy resin, ordinary glycidyl ether type epoxy resin (bisphenol A type, bisphenol F type,
Any epoxy resin may be used, including novolac type, cresol novolac type, etc.).

[0015] In the present invention, the blending ratio of the constituent components is not particularly limited, but for example, epoxy resin 100%
It is preferable to use 30 to 80 parts by weight of a phenolic curing agent, 10 to 85 parts by weight of a filler having a methylol group refraction index, and 0 to 2 parts by weight of other compounds based on the weight part. If the ratio of the phenolic curing agent is out of the above range, the T of the cured product will be
g is low, the electrical properties are deteriorated, and the hygroscopicity may also be high. If the proportion of the filler is below the range, the linear expansion coefficient and moisture absorption rate of the sealing material will increase, resulting in a decrease in reliability. If it exceeds the viscosity, the viscosity may become high and molding may not be possible. If the proportion of other compounds exceeds the above range, there is a risk that the transparency of the cured product will decrease significantly. However, 0.5 parts by weight or more may be added as long as it does not impair transparency.

The form of the sealing material of the present invention is not particularly limited, and may be liquid or powder formed into a molding material. Furthermore, it may be a granule or a pellet or tablet. When used as a molding material, it is preferable to knead the entire composition in a homodisper to advance B-stage formation. The material must be thoroughly kneaded to ensure good affinity between the filler and the matrix resin, and must be molded so that no macroscopic bubbles remain. Avoid contamination with dust during kneading to prevent substances that cause opacity from being mixed in.
It is also preferable to use a hard material such as ceramic or stainless steel for the kneader.

[0017]

[Operation] By using a filler having a refractive index within the range that satisfies the above formula (I), it is possible to maintain high transparency while maintaining the low linear expansion, low hygroscopicity, and low curing heat generation of conventional sealing materials. sex(
For example, 3 to 4 times that of conventional products) can be achieved.

[0018]

[Examples] Specific examples and comparative examples of the present invention are shown below, but the present invention is not limited to the following examples. In the following examples, the filler has the following refractive index:
A non-alkali glass A was used, and in the comparative example, a filler B mainly composed of silica and having the following refractive index was used.

A: n = 1.62 [alkali-free glass (manufactured by Yamamura Glass), crushed] B: n = 1.51 [normal fused silica (RD-8, manufactured by Tatsumori Co., Ltd.), crushed] The average particle diameters of these fillers were 20 μm for A and 15 μm for B. Further, the refractive index was measured using an Abbe refractometer. -Example- Cresol novolak type epoxy resin (ESC manufactured by Sumitomo Chemical Co., Ltd.) as epoxy resin
N195XL (epoxy equivalent: 195) and phenol novolac resin (PSM6200 manufactured by Arakawa Chemical Co., Ltd.) as a phenolic curing agent were blended in the proportions shown in Table 1 below, and heated at 80°C for 10 minutes using a mixing roll. Kneading was carried out to obtain an epoxy resin sealing material.

The obtained sealing material was molded into a predetermined shape using a transfer molding machine, and then its physical properties were measured by the following method. In addition, for measuring light transmittance and hue,
Samples with a thickness of 1 mm and a thickness of 2 mm were used. Measurement of physical properties/coefficient of linear expansion: Measured by TMA, and calculated values at 50 to 80°C.・Light transmittance; using a UV photometer, 660 nm (
The transmittance in red light) was adopted.・Others: The color was visually checked.

- Reference Example - In the example, an epoxy resin sealing material was obtained in exactly the same manner as in the example except that the filler was not included. The refractive index of the obtained sealing material was measured at 20° C. and found to be 1.61. Moreover, it was 1.59 when measured at 100°C.

- Comparative Example - In the example, instead of filler A having a refractive index of 1.62, filler A with a refractive index of 1.59 (=1.61-
An epoxy resin sealing material was obtained in exactly the same manner as in the example except that filler B having a refractive index of less than 0.02) was used, and its physical properties were measured. The above results are shown in Table 1.

[0023]

[Table 1]

As shown in Table 1, the sealing material according to the example had almost the same coefficient of linear expansion and color as the sealing material according to the comparative example, but the light transmittance was extremely high. This was confirmed.

[0025]

Effects of the Invention The epoxy resin encapsulant material for optical semiconductors according to the present invention has low linear expansion, low moisture absorption, and low curing heat generation, as well as high transparency (for example, 3 to 4 times that of conventional products). Excellent. Therefore, by encapsulating an optical semiconductor using the encapsulating material of the present invention, it is possible to design a highly efficient composite optical device without increasing the current amplification factor on the transistor side, or to design a composite optical device with high dielectric strength. It becomes possible to generate. For example, even if the distance between the light-emitting element and the light-receiving element is twice that of the conventional product, it is possible to send and receive more optical information than the conventional product.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing the path of incident light to a sealing material using a spherical filler.

FIG. 2 is a cross-sectional view schematically showing a path of incident light to a sealing material using a crushed filler.

FIG. 3 is a cross-sectional view showing the sealing structure of a conventional photocoupler.

[Explanation of symbols]

6 Spherical filler 7 Matrix resin 16 Crushed filler

Claims (3)

[Claims] 1. A sealing material containing an epoxy resin, a phenolic curing agent, and a filler, characterized in that the filler has a refractive index that satisfies the relationship of formula (I) below. Epoxy resin encapsulation material for optical semiconductors. n
(matrix)-0.02≦n(filler)≦n
(matrix)+0.07...(I) [where n(
matrix) represents the refractive index of a cured product obtained by curing components other than the filler among all the sealing materials, and
er) represents the refractive index of the filler. ] 2. The epoxy resin sealing material for optical semiconductors according to claim 1, wherein the filler is glass. [Claim 3] Claim 1 or 2, wherein the filler is spherical.
The described epoxy resin sealing material for optical semiconductors.