JPH064838B2 - Adhesive composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a material for sealing a light-transmitting optical window in a solid-state imaging device and a package accommodating a solid-state imaging device, and more specifically, a package. The present invention relates to an adhesive composition for hermetically sealing an optical window for obtaining a solid-state image pickup device which prevents moisture from entering from the outside and has excellent image pickup characteristics, long life, and high reliability.

[Conventional technology]

Usually, in a solid-state image pickup device, a solid-state image pickup device such as a metal oxide semiconductor device is housed inside a ceramic or plastic package as a charge-coupled device, an optical window made of glass or plastic is arranged on the upper surface of the package, and an adhesive is used. Due to this, the structure is hermetically sealed.

Since this solid-state image sensor is used as an optical sensor, the essential requirement for hermetic sealing is to prevent moisture from entering the inside of the package and to prevent optical changes due to reaching the dew point inside the package. There is.

Generally, there are two methods for hermetically sealing the image pickup device depending on the material of the sealing material.

One is a glass sealing method and the other is a resin sealing method.

The glass sealing method uses low-melting glass called frit as an adhesive. This glass sealing method has high reliability with respect to moisture resistance, but it is 200 to 50 at the time of bonding.
It is necessary to fire at a high temperature of 0 ° C. However, in a color solid-state imaging device, which has been in increasing demand in recent years, a photosensitive organic film called a color filter array is formed on the element surface, and this organic film is deteriorated during the above firing. Occurred.

Therefore, at present, much research has been conducted on a resin encapsulation method using an organic polymer capable of adhering at a lower temperature (150 ° C. or lower).

However, an excellent adhesive for hermetically sealing an optical window of a solid-state image pickup device having sufficient moisture resistance and airtightness has not been obtained.

[Problems to be Solved by the Invention]

An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide a solid-state imaging device having good moisture resistance and high reliability without damaging a circuit or a color filter array formed on the solid-state imaging device. To provide an adhesive composition for hermetically sealing an optical window.

[Means for Solving the Problems]

The inventors of the present invention have made intensive studies to solve these problems, which could not be overcome by the conventional techniques, and have a solid-state bisphenol S type epoxy resin (I) derived from (A) bisphenol S and epichlorohydrin. ), Bisphenol A, and a resin mixture of bisphenol A type epoxy resin (b) which is liquid at room temperature and is derived from epichlorohydrin.

(B) Diaminodiphenylsulfone (C) Inorganic filler is an essential component, and the mixing ratio of (A) and (B) is (A) / (B) + (B) = 3 to 40 by weight ratio. The inventors have found that the optical window of the solid-state imaging device is hermetically sealed by using an adhesive characterized by being 100%, and have completed the present invention.

[Action]

As described above in the related art, the demand for color solid-state imaging devices is increasing, and the sealing method for optical windows is shifting from the glass sealing method to the resin sealing method. However, in the resin sealing method,
A considerable amount of water has been allowed to enter, and dew condensation inside the package has caused deterioration of imaging characteristics.

The feature of the present invention is that the adhesive for hermetically sealing the optical window has a very high sealing property or airtightness, and the intrusion of moisture into the package is extremely small.

Generally, in the case of resin encapsulation, there are two conceivable routes of water penetration: penetration from the adhesive interface and diffusion inside the resin.

The inventors investigated various combinations of epoxy resin and curing agent, sealed the solid-state image sensor, forcedly placed this device under high temperature and high humidity, and investigated the water intrusion route into the package. , It was found that the invasion of water occurs mainly at the interface between the adhesive for hermetically sealing the optical window and the package.

It is known that when the surface of the adherend such as ceramics is rough, the adhesive enters the pores on the surface of the adherend and a large adhesive force is expressed by the so-called anchor effect. The penetration of moisture into the package is the key to how deeply the stopping adhesive penetrates into the recesses on the adhesive surface.

The present inventors have found the following and have reached the present invention. That is, the bisphenol S-type epoxy resin has a high glass transition temperature once it reacts slowly with the amine compound as the curing agent, but once it is cured. On the other hand, in the reaction between the liquid bisphenol A type epoxy resin and the amine compound, the viscosity once decreases due to the temperature rise during curing, but the reaction rate is high, so that the viscosity rapidly rises. However, a resin mixture of bisphenol S type epoxy resin (a), bisphenol A type liquid at room temperature, and epoxy resin (b) [(b) / (b) + (b) = 3 to 40% by weight] is used as a curing agent. What is surprising when diaminodiphenyl sulfone is used is that the viscosity remains low during heat molding for a long time, so it penetrates deeply into the dents present on the adhesive surface, exerting a strong anchoring effect, and at the same time glass It was found that a cured product having a very high transition temperature can be obtained. Therefore, even in the pressure cooker test (hereinafter referred to as PCT), which is an accelerated moisture resistance test, it is easy to maintain the original characteristics and good results are obtained. In addition, since the cross-linking density of the cured product is very high, there is also an advantage of suppressing the moisture that diffuses in the resin and enters.

The bisphenol S-type resin may be any of various molecular weights or a bisphenol S-type epoxy resin in which an alkyl group or the like is introduced into the aromatic ring of the bisphenol S skeleton.

Further, as a result of various studies on the liquid epoxy resin which melts the bisphenol S type epoxy resin at room temperature, the bisphenol A type epoxy resin which is liquid at room temperature has the optimum moisture resistance. It is considered that this is because the bisphenol A type epoxy resin itself exhibits a high glass transition temperature when cured with diaminodiphenyl sulfone and, at the same time, has a low viscosity when heated, so that an anchor effect is easily exhibited.

Diaminodiphenyl sulfone is the most suitable curing agent. Because the epoxy resin of the present invention contains a highly reactive epoxy resin, diaminodiphenyl sulfone has a low reactivity with an epoxy group, so that the reaction rate is slow in heating for curing and the viscosity is low. Is kept low for a long time, and therefore the wettability with the adherend surface is good. Also, the glass transition temperature of the cured product is high,
Therefore, it has good moisture resistance. Furthermore, since the sulfone groups of the bisphenol S type epoxy resin and diaminodiphenyl sulfone have high polarity, a strong interaction works on the adhesive surface, the adhesive strength is high, and the moisture resistance for a long time is guaranteed.

Also, since the reactivity of the bisphenol S type epoxy resin and diaminodiphenyl sulfone is low, the compound in a semi-cured state called the so-called B stage does not show any change in the physical properties even at room temperature. Has a very long pot life.

Diaminodiphenylsulfone has various isomers depending on the position of the amino group, but any isomer can be used.

Quantitatively speaking, the proportion of the bisphenol S type epoxy resin in the epoxy resin is less than 3% by weight, but if it is less than 3% by weight, the reactivity becomes fast and the viscosity rises rapidly during curing and heating, and a sufficient anchor is obtained. The effect is not obtained and therefore the moisture resistance is also poor.

Since the bisphenol S type epoxy resin is solid at room temperature, if it is blended in a proportion of more than 40% by weight, the viscosity of the blend is high and the melt viscosity is also high. It is very difficult to get the anchor effect. Further, when a solvent is added to reduce the viscosity, it may cause generation of voids and the like, leading to a decrease in moisture resistance, and a solvent remaining in the resin is generated at the time of curing and agglomerates inside the package, resulting in deterioration of imaging characteristics. There is also a danger. Therefore, the proportion of the bisphenol S type epoxy resin needs to be in the range of 3 to 40% by weight.

As a result of a more detailed examination, it is found that the optimum proportion of the bisphenol S type epoxy resin is 10 to 20% by weight.
The amount of water that penetrates when applied to T is very small.

Next, as the inorganic filler used in the present invention, there are silica, alumina, calcium carbonate, magnesium oxide, magnesium hydroxide, boron nitride, zinc oxide and the like, which can be used alone or in combination of two or more kinds.

Further, it is more preferable that the inorganic filler is subjected to a coupling treatment with a silane-based or titanate-based coupling agent in order to improve the wettability with the resin.

These inorganic fillers impart appropriate viscosity and thixotropy properties and make them excellent in printing characteristics, and at the same time, since these inorganic fillers themselves do not absorb or permeate water, by increasing the addition amount, so-called bulk There is also an advantage that the amount of water absorption can be reduced.

The actual amount of addition is determined by the particle size of the filler, the specific surface area, etc., but is about 20 to 80% by weight, but if the printability, the presence or absence of voids, the wettability with the resin, etc. are considered, 50% by weight is desirable. If it is more than 80% by weight, the printability will deteriorate unless a solvent is added.

If necessary, other curing accelerators, defoaming agents, etc. may be added as appropriate.

[Examples] Example 1 5 parts by weight of bisphenol A type epoxy resin having an epoxy equivalent of 305 and 95 parts by weight of bisphenol A type epoxy resin having an epoxy equivalent of 190, and 32 parts by weight of 4,4'-diaminodiphenylsulfone. 0.5 parts by weight of boron fluoride biperidine complex salt and 60 parts by weight of zinc oxide having an average particle size of 0.5 μm are mixed and kneaded with a three-roll to disperse them evenly, and adhere to the solid-state image sensor for hermetic sealing of optical windows I got an agent.

This adhesive was applied by screen printing to the optical window glass of the solid-state imaging device with a thickness of 80 μm, and then 100 ° C.
Then, it was allowed to stand still in a dryer of No. 2 and cured to a so-called B-stage state of semi-curing to prepare an optical window.

Using this optical window, the package of the ceramic solid-state imaging device was hermetically sealed while pressure-bonded at a temperature of 150 ° C. The heating time is 1 hour.

This solid-state imaging device package is
Subjected to PCT test at 100% relative humidity for 24 hours, 48 hours
To find out the absolute water content inside the package after an hour,
Gas analysis was performed. As a result, the amount of water vapor was 10% by volume and 4% after being subjected to PCT for 24 hours.
It contained only a very small amount of water vapor of 18 vol% in 8 hours.

Further, the water permeability and the glass transition temperature were examined using the preservability at room temperature as the characteristic in the B stage state and the characteristic of the cured product.

Regarding the storability, the optical window was left at 24 ° C. and a relative humidity of 40%, and the moisture resistance was examined by the above-mentioned PCT. As a result, no change was observed for 6 months.

Also, make 100μm film with this adhesive,
The glass transition temperature of the one cured at 3 ° C. for 3 hours was measured by thermal analysis, and it showed a high glass transition temperature of 150 ° C. Regarding the water permeability, a film having a thickness of 100 μm was prepared and cured at 150 ° C. for 3 hours, and the result was measured by the cup method (JIS Z0208-1973). As a result, a very low water permeability of 5 (g / m ² , 24 hours) was obtained. Indicated.

Examples 2 to 4 Except for changing the proportion of the bisphenol S type epoxy resin in the epoxy resin mixture and the compounding amount of the curing agent as shown in Table 1, all were made in the same manner as in Example 1 for sealing optical windows. An adhesive was prepared and each evaluation shown in Example 1 was performed.

Moisture resistance was good in all of Examples 2, 3, and 4.
Regarding the storability, no change was observed for 6 months.

Example 5 An adhesive for hermetically sealing an optical window was prepared in the same manner as in Example 1 except that 3,3′-diaminodiphenylsulfone was used as a curing agent and spherical silica having an average particle size of 25 μm was used as a filler. And each evaluation shown in Example 1 was performed.

The humidity resistance was almost the same as that of Example 1, and the storage resistance was not changed for 6 months.

The glass transition temperature is 165 ° C., and it can be said that it is an adhesive agent for hermetically sealing an optical window, which has sufficient reliability as in Example 1.

Example 6 Epoxy equivalent 2 as bisphenol S type epoxy resin
The bisphenol S skeleton No. 10 into which a methyl group was introduced was used, and the compounding amount is as shown in Table 1. Other than that, an adhesive for optical window hermetic sealing was prepared by the same method as in Example 1 and each evaluation was performed. As a result, as in Example 1, very good results were obtained.

Comparative Example 1 As the epoxy resin, only a bisphenol A type epoxy resin which was liquid at room temperature and had an epoxy equivalent of 190 was used and compounded as shown in Table 1. Except for this, the optical window hermetically sealing adhesive was prepared and evaluated in the same manner as in Example 1.

Moisture resistance by PCT is that treated by PCT for 24 hours, water vapor amount is 21 vol%, 48 hours is 47 vo
The moisture absorption amount was 1%, which was several times that of Examples 1, 2 and 3.

In particular, as the time taken for PCT becomes longer, the amount of moisture absorption greatly increases, and it is expected that it cannot withstand long-term use under practically severe conditions.

Comparative Examples 2 and 3 Except that the ratio of the bisphenol S type epoxy resin in the epoxy resin mixture and the compounding amount of the curing agent were as shown in Table 1, the same procedure as in Example 1 was performed to hermetically seal the optical window. An adhesive was prepared and each evaluation shown in Example 1 was performed.

As a result, the moisture resistance was 20% by volume in Comparative Example 2 after 20 hours of PCT, 20% by volume in Comparative Example 3 and 35% by volume in Comparative Example 2 and 30% in Comparative Example 2.
The water content was 1%, which was about several times as large as that in the example, and the moisture resistance was insufficient.

Comparative Example 4 A bisphenol S-type epoxy resin was heated and dissolved in butyl cellosolve acetate to prepare a 70 wt% solution, which was blended as shown in Table 1. Except for this, the adhesive for optical window hermetic sealing was prepared in the same manner as in Example 1 and each evaluation was performed.

Regarding the performance, as shown in Table 1, the moisture resistance was poor. As a result of observing the fracture surface with a scanning electron microscope, many voids were generated, which is considered to be the cause of deteriorating the moisture resistance.

Comparative Example 5 4,4′-diaminodiphenylmethane was used as a curing agent, and the compounding amount was as shown in Table 1.
Except for this, an adhesive for hermetically sealing an optical window was prepared and evaluated in the same manner as in Example 1.

As a result, the moisture resistance was poor. Also, regarding the holding property, 3
It got worse after months. This is 4,4 'as a curing agent
-Since diaminodiphenylmethane is used, it is presumed that the reaction proceeded at room temperature and therefore the viscosity of the heat-melted product was high and the wettability on the adhesive surface was poor.

Comparative Example 6 A bisphenol S-type epoxy resin was used with an epoxy equivalent of 17
It was dissolved in a liquid bisphenol F type epoxy resin at room temperature of 0 and blended as shown in Table 1.

Except for that, an adhesive for optical window hermetic sealing was prepared and evaluated in the same manner as in Example 1. As a result, the moisture resistance was poor.

[Effects of the Invention] As can be seen from the above Examples and Comparative Examples, according to the present invention, it is possible to obtain a solid-state imaging device having excellent moisture resistance and high reliability, and the obtained solid-state imaging device is good. It has excellent imaging characteristics, has a long life, and guarantees high reliability.

Claims (1)

[Claims] 1. A bisphenol S-type epoxy resin (A) derived from bisphenol S and epichlorohydrin, which is solid at room temperature, and a bisphenol A-type epoxy resin (B) derived from bisphenol A and epichlorohydrin, which is liquid at room temperature. Resin mixture. (B) Diaminodiphenylsulfone (C) Inorganic filler is an essential component, and the mixing ratio of (A) and (B) is (A) / (B) + (B) = 3 to 40 by weight ratio. %, An adhesive composition for hermetically sealing an optical window of a solid-state imaging device.