JP5540506B2 - Window glass for solid-state image sensor package - Google Patents

Description

  The present invention relates to a window glass for a solid-state image sensor package that is attached to the front surface of a package that houses a solid-state image sensor, protects the solid-state image sensor, and is used as a transparent window.

The solid-state image sensor is an LSI chip, which is a light-receiving element, placed in a package made of alumina ceramic or resin, a color separation mosaic filter is placed on the light-receiving surface, wire bonding is performed, and a cover glass is sealed to the package opening with an adhesive. It has a structure. The cover glass used here not only protects the LSI chip by hermetic sealing with the package, but also efficiently introduces light into the light receiving surface, so it has optically homogeneous material characteristics with low internal defects and high transmittance. Characteristics are required. Moreover, the glass used for such a use must not generate | occur | produce a crack and distortion, when sealed with a package. That is, it is necessary to match the thermal expansion coefficients of the glass and the package material.
In addition, since solid-state imaging devices such as CCDs generate soft errors due to α rays emitted from the cover glass, the amount of radiation isotopes that emit α rays contained in the glass is reduced.

Incidentally, in addition to the above, the window glass for a solid-state imaging device package is required to be a highly reliable material with little deterioration with time. Specifically, high weather resistance and solarization resistance are required, which do not cause fogging on the glass surface due to moisture or decrease in transmittance due to solarization phenomenon during long-term use. In Patent Document 1, it is said that a glass having high reliability for long-time exposure can be obtained by adding an appropriate amount of PbO or TiO ₂ as a solarization inhibitor. In addition, Sb ₂ O ₃ is also known as a solarization inhibitor. Examples of the glass containing TiO ₂ or Sb ₂ O ₃ include glasses described in Patent Document 2 and Patent Document 3.

JP-A-7-233939 JP 2005-8509 A JP-A-2005-162600

For the window glass for a solid-state image sensor package, an ultraviolet curable adhesive has been used for the purpose of shortening the curing time in hermetic sealing with the package containing the solid-state image sensor.
However, when PbO, TiO ₂ , or Sb ₂ O ₃ is contained in the glass, the ultraviolet light used when the ultraviolet curable resin is cured is absorbed by the glass due to the light absorption characteristics of these elements. When hermetically sealing the material to the package, it takes a long time to cure the ultraviolet curable resin adhesive, and there is a problem that the capability of the assembly process of the solid-state imaging device is lowered.
On the other hand, in the glass cleaning process, ultraviolet irradiation is performed on the glass surface, and organic pollutants are decomposed and removed into volatile substances by the action of active oxygen separated from ozone generated by the action of ultraviolet rays, so-called ultraviolet cleaning. May be performed. In the ultraviolet cleaning, since ultraviolet rays having strong energy are irradiated in a short time, there is a possibility that the coloring (solarization) of the glass is promoted.
Further, in consideration of the recent global environment, it is demanded that as much as possible no environmentally hazardous substances be used in parts constituting home appliances such as video cameras. For glass parts, PbO, As ₂ O ₃ , Sb ₂ are also required. There is a need for environmentally friendly glasses that do not contain O ₃ .
In view of such circumstances, an object of the present invention is to provide a window glass for a solid-state imaging device package having high ultraviolet transmission characteristics while having high weather resistance and solarization resistance.

The window glass for a solid-state imaging device package of the present invention is, by mass%, SiO ₂ 58 to 75%, Al ₂ O ₃ 0.5 to 15%, B ₂ O ₃ 6 to 20%, Li ₂ O 0 to 7%. , Na ₂ O 0-15%, K ₂ O 0-15% (however, Li ₂ O + Na ₂ O + K ₂ O 2-20%), ZrO less than 0.01%, SnO ₂ 0-0.1%, Nb ₂ O ₅ 0~0.2%, (provided _{that, SnO 2 + Nb 2 O 5} 0.001~0.2%), containing Fe 2 O 3 0.0001~0.005%, and being substantially free of _as 2 O ₃ , It consists of borosilicate glass which does not contain Sb ₂ O ₃ , PbO, TiO ₂ or CeO ₂ .
Further, the borosilicate glass is characterized by containing SnO ₂ 0.002 to 0.04% by mass.
The borosilicate glass is substantially free of MgO, CaO, SrO, BaO, and ZnO, and the amount of α rays emitted from the glass is less than 0.0002 c / cm ² · h. To do.

The window glass for a solid-state imaging device package of the present invention contains SnO ₂ and Nb ₂ O ₅ in a total amount of 0.001 to 0.2%, and substantially contains As ₂ O ₃ , Sb ₂ O ₃ , and PbO. Therefore, a glass excellent in weather resistance can be obtained while considering the environment. Further, since it contains 0.002 to 0.005% of Fe ₂ O ₃ and does not substantially contain TiO ₂ or CeO ₂ , it is possible to prevent coloring due to the interaction of these elements, and thus a glass with high transmittance. Is obtained.

  Hereinafter, the best mode for carrying out the present invention will be described.

SnO ₂ is a component that prevents solarization, but when added, the glass has an ultraviolet absorbing performance. When the window glass for solid-state image sensor package and the package are sealed with an ultraviolet curable resin adhesive, if the glass has an ultraviolet absorption capability, the amount of ultraviolet light that reaches the ultraviolet curable resin adhesive when irradiated with ultraviolet rays Is reduced by being absorbed by the glass, and a long time is required for curing. For this reason, when it exceeds 0.1% in terms of SnO ₂ , the ultraviolet absorption performance of the glass is high, the curing time of the ultraviolet curable resin adhesive becomes long, and the workability is remarkably deteriorated. The content of SnO ₂ is preferably 0.002 to 0.04%, more preferably 0.002 to 0.015%. Note that, in the window glass for a solid-state image pickup device package of the present invention, the Sn component is defined by the content of SnO _2. This is an oxidation in which the content of Sn (tin) contained as a glass composition is an oxide. Expressed as a mass ratio when converted to stannic, it means being within a predetermined range. In addition, other components of the glass composition are similarly expressed in terms of the oxides described.

Nb ₂ O ₅ is a component that prevents solarization as in the case of SnO _2. However, if it exceeds 0.2% by mass, the glass is colored and the transmittance in the visible light region is lowered, which is not preferable.

If the total amount of SnO ₂ and Nb ₂ O ₅ that are anti-solarization components is less than 0.001%, a sufficient anti-solarization effect cannot be obtained, which is not preferable. The total amount of SnO ₂ and Nb ₂ O ₅ is preferably 0.002 to 0.04%, more preferably 0.002 to 0.015%.

Fe ₂ O ₃ is a component that prevents solarization, but is also a component that strongly absorbs ultraviolet rays, and if it exceeds 0.005% by mass, it is not preferable because the amount of ultraviolet rays absorbed by the glass increases. If it is less than 0.0001%, the effect of preventing solarization cannot be obtained, which is not preferable. Moreover, since Fe ₂ O ₃ is a component that is difficult to eliminate completely on industrial equipment, if it is less than 0.0001%, it is necessary to make the purity of various raw materials very high, which is not preferable because the raw material cost increases. . A preferable range is 0.0003% to 0.002%.

As ₂ O ₃ , Sb ₂ O ₃ , and PbO have been added in the conventional glass for the purpose of clarifying effect and prevention of solarization. However, since they are environmental impact substances, Should not be included. In the present invention, substantially not containing means that it is not intentionally added, and it is unavoidably mixed from raw materials and the like, and does not exclude inclusions that do not affect the intended properties. However, it is preferable to eliminate as much as possible.

Since TiO ₂ and CeO ₂ strengthen the coloring of glass due to interaction when Fe ₂ O ₃ is present in the glass, they are not substantially contained in the window glass for a solid-state imaging device package that requires high transmittance characteristics. Need to manage. In the state where the solid-state image sensor is mounted in the camera, the progress of solarization of glass due to external light is negligible. However, as described above, when using UV curable resin adhesive or cleaning glass with UV light, it takes a short time. In the present invention, this problem has been solved by avoiding the coexistence of those causative substances. TiO ₂ and CeO ₂ are powerful ultraviolet absorbers, and when added to glass, the glass has ultraviolet absorption performance. As described above, when the ultraviolet absorption performance of glass is high, the curing time of the ultraviolet curable resin adhesive becomes long.

Further, an embodiment of the present invention, the borosilicate glass, in _{mass%, SiO 2 58~75%, Al} 2 O 3 0.5~15%, B 2 O 3 6~20%, Li 2 It is characterized by containing O 0-7%, Na ₂ O 0-15%, K ₂ O 0-15% (however, Li ₂ O + Na ₂ O + K ₂ O 2-20%), less than 0.01% ZrO. However, the reason why the content of each component is limited as described above will be described below.

SiO ₂ is a main component constituting the glass skeleton and is a component that improves the durability of the glass. However, if it is less than 58%, chemical durability cannot be obtained, and if it exceeds 75%, the meltability is remarkably deteriorated. Preferably, it is 63 to 71%.

Al ₂ O ₃ is a component that improves the weather resistance of the glass, but if it is less than 0.5%, the chemical durability is not sufficient, and striae tends to occur in the glass that exceeds 15%. . Preferably, it is 1 to 15%.

B ₂ O ₃ is a component used for the purpose of improving the meltability and adjusting the viscosity. However, if it exceeds 20%, the weather resistance tends to decrease, and if it is less than 6%, the meltability tends to deteriorate. Preferably, it is 10 to 19%.

Li ₂ O, Na ₂ O and K ₂ O are components that act as fluxes and improve devitrification resistance. However, if the total amount is less than 2%, the effect is not obtained, and if it exceeds 20%, the weather resistance is deteriorated and the thermal expansion coefficient is increased. The content of each component, in mass%, the Li ₂ O 0 to 7%, 0 to 15% of Na ₂ O, it is preferable that 0 to 15% of _{K 2} O. When each content exceeds each upper limit, the thermal expansion coefficient becomes too large, or the weather resistance deteriorates.

ZrO ₂ is a substance containing U or Th as radioisotopes as impurities, and in order to minimize the amount of α-ray emission from the glass, it is less than 0.01%, preferably less than 0.005%, more preferably 0.8. It is desirable to keep it below 002%.

Alkaline earth metal oxides (MgO, CaO, SrO, BaO) are effective components for improving meltability, weather resistance, devitrification resistance and adjusting the thermal expansion coefficient. Then, it was confirmed that the amount of α rays emitted from the glass varies greatly. This is because, in the alkaline earth metal oxide raw material, the contents of U and Th related to the amount of α-ray emission can be managed in the ppb order, but the content of Ra related to the amount of α-ray emission is also controlled. It is difficult and is presumed to be affected by Ra. Specifically, the content of Ra mixed as an impurity in the raw material of the alkaline earth metal oxide is an order of magnitude lower than ppb, and it is difficult to accurately analyze the Ra of the content. Therefore, it is practically difficult to control the Ra content mixed as an impurity, which is considered to affect the variation in the amount of α-ray emission when an alkaline earth metal oxide is used as a glass raw material. .
Therefore, in the window glass for a solid-state imaging device package of the present invention, when the alkaline earth metal oxide is contained, the total amount of the alkaline earth metal oxide is preferably less than 1%. More preferably, the oxide is substantially not contained.

  ZnO is an effective component for preventing devitrification and improving chemical durability, but it is difficult to control the Ra content as in the case of alkaline earth metal oxides. Since the amount may vary, when ZnO is contained, the content is preferably 5% or less, and more preferably substantially free of ZnO.

As described above, by substantially not containing alkaline earth metal oxide and ZnO, the mixing of Ra into the glass can be suppressed, and the amount of α rays emitted from the glass is 0.0015 c / cm ^2. -It can be set to h or less. Thereby, the window glass for a solid-state image pickup device package of the present invention has a small amount of α-ray emission from the glass, and the use of this glass can reduce the possibility of an error occurring in the solid-state image pickup device.

In addition, the window glass for a solid-state imaging device package is required to be as small and small as possible (for example, 5 μm or less) for defect quality such as bubbles and foreign matters. Since the window glass for a solid-state image pickup device package of the present invention does not substantially contain As ₂ O ₃ and Sb ₂ O ₃ that have been used as fining agents in conventional glass, for the purpose of fining, sulfates and nitrates are used. It is desirable to add chlorides and fluorides alone or in combination as appropriate.
Since these components are all decomposition volatile components and volatilize as exhaust gas, the upper limit is preferably set to 0.5% or less in consideration of the cost of corrosion and treatment of the exhaust gas treatment apparatus in glass production. Moreover, in order to cut a bubble effectively, it is preferable to set it as 0.005% or more.

  Next, the manufacturing method of the window glass for solid-state image sensor packages of this invention is demonstrated.

First, the glass raw material which comprises each component of a desired composition is prepared. As the glass raw material used in the present invention, any form of compound such as oxide, hydroxide, carbonate, sulfate, nitrate, fluoride, and chloride can be used. In any glass raw material, it is preferable to use a high-purity glass raw material having a low radioisotope content (for example, a U content of 10 ppb or less and a Th content of 15 ppb or less). More preferably, in any raw material, the α-ray emission amount is 0.1 c / cm ² · h or less. When such a glass raw material is prepared into a glass raw material preparation, the U content is finally 10 ppb or less, the Th content is 20 ppb or less, and the α-ray emission amount is 0.01 c / cm ^2.・ H or less glass can be obtained.

Next, the glass raw material is prepared so that this raw material becomes glass having a desired composition, and the raw material is put into a melting tank.
The melting tank is a container selected from platinum, a platinum alloy, and a refractory. In the present invention, platinum and a platinum alloy are made of an alloy using a metal selected from the group consisting of platinum (Pt), iridium (Ir), palladium (Pd), rhodium (Rh), gold (Au), and alloys thereof. It is a container and can withstand high temperature melting.
Further, in order to minimize the α-ray emission of the glass, the radioactive isotope is α-ray emitting sources from the viewpoint of preventing contamination of ZrO ₂ containing many as an impurity, using the refractory of the ZrO ₂ in the molten bath It is preferable to use a melting facility that uses alumina refractory (Al ₂ O ₃ 95% or more) and quartz refractory, thereby suppressing radioactive isotopes mixed in the glass and emitting alpha rays. A small amount of glass can be obtained.

  By removing bubbles and striae in a defoaming tank or a stirring tank in which the glass melted in the melting tank is arranged on the downstream side, a homogenized high quality glass with few glass defects can be obtained. The glass described above is allowed to flow out through a nozzle or the like and cast into a mold, or rolled out and drawn into a plate shape to be formed into a predetermined shape. The slowly cooled glass is subjected to slicing, polishing and the like to obtain a glass having a predetermined shape.

  Hereinafter, the present invention will be described based on examples.

The sample used for each Example (No.1-No.17 of Table 1) and each comparative example (No.18-No.21 of Table 1) was created as follows.
First, a glass raw material was prepared so as to have the glass composition shown in Table 1, and this glass raw material mixture was melted at a temperature of 1550 ° C. for 5 hours in an electric furnace using molybdenum silicide as a heating element using a platinum crucible. After that, it was clarified and stirred. This glass was cast into a cast iron mold and slowly cooled to obtain 800 g of a glass sample (glass block). Further, this glass block was sliced, polished, etc., to obtain a glass having a predetermined shape (25 mm × 25 mm × 1 mm).

The obtained glass block and glass were evaluated for solarization resistance , α-ray emission amount, and foam. These results are shown in Table 1.

Solarization resistance was measured using a V-570 type UV-Vis near-infrared spectrophotometer (manufactured by JASCO Corporation) for glass of a predetermined shape (25 mm × 25 mm × 1 mm) that was optically polished on both sides to a thickness of 1 mm. The transmittance was measured. Next, after irradiating the glass with ultraviolet rays based on Japan Optical Glass Industry Association measurement standard JOGIS-04, the transmittance of the glass was measured again, and the change in transmittance at a wavelength of 400 nm before and after the ultraviolet irradiation was compared. Note that transmittance change (%) = [(transmittance before UV irradiation−transmittance after UV irradiation) / transmittance before UV irradiation] × 100 is 1% or more, “changed”, 1 The case of less than% was regarded as “no change”. Each glass of the example had a small change in transmittance before and after the ultraviolet irradiation , and had higher solarization resistance than each glass of the comparative example. The glass of Comparative Example (No.21) is had less transmittance change before and after the ultraviolet irradiation similarly to the glass of Example, which is considered because it contains the Sb ₂ O _3.

The amount of α-ray emission was measured using a glass flow proportional counter. As a result, all the glasses of the examples had an α-ray emission amount of 0.01 c / cm ² · h or less. In addition, each glass of Examples (No. 11, No. 15, No. 17) substantially not containing alkaline earth metal oxides (MgO, CaO, SrO, BaO) and ZnO emits alpha rays. The amount is 0.0015 c / cm ² · h or less, the α-ray emission amount is very low, and it has characteristics suitable as a window glass for a solid-state imaging device package.

The foam is a value obtained by measuring and observing a volume of about 300 g from a glass block and polishing both sides with a 20-fold stereo microscope, and converting the measured number of bubbles per kg. Each glass of Examples, although do not contain _As 2 _{O 3} and _Sb 2 _{O 3} which has been conventionally used as a fining agent, _Sb 2 _{O 3} Example Comparative containing the (No.21) and the number of bubbles Are equivalent and have suitable foam quality as a window glass for a solid-state imaging device package.

Next, in order to confirm the transmittance of the glass in the ultraviolet wavelength region, Example No. 1 and Example No. 4, Example No. 10, Comparative Example No. For each of the 20 glasses, the spectral transmittance at a thickness of 1 mm was measured. The results are shown in Table 2. From these, each glass of the example has a high transmittance in the ultraviolet wavelength region because the transmittance at 254 nm is 70% or more, and is a case where the glass is fixed to the package with an ultraviolet curable resin adhesive. In addition, the glass can be fixed in a short ultraviolet irradiation time without the ultraviolet rays to be irradiated being absorbed by the glass. In contrast, the glass of Comparative Example 20 containing 0.2% SnO ₂ had a transmittance at 254 nm of 25% or less. This is considered to be due to the ultraviolet absorption effect of SnO _{2. When} this glass is fixed to the package with an ultraviolet curable resin adhesive, a long ultraviolet irradiation time is required.

  According to the present invention, it is possible to provide a window glass for a solid-state imaging device package that has high weather resistance and solarization resistance, has high ultraviolet transmission characteristics, and is environmentally friendly.

Claims (3)

By _{mass%, SiO 2 58~75%, Al} 2 O 3 0.5~15%, B 2 O 3 6~20%, Li 2 O 0~7%, Na 2 O 0~15%, K 2 O 0-15% (however, Li ₂ O + Na ₂ O + K ₂ O 2-20%), ZrO less than 0.01%, SnO ₂ 0-0.1%, Nb ₂ O ₅ 0-0.2%, (however, SnO ₂ + Nb ₂ O ₅ 0.001 to 0.2%), Fe ₂ O ₃ 0.0001 to 0.005%, substantially As ₂ O ₃ , Sb ₂ O ₃ , PbO, TiO ₂ , A window glass for a solid-state imaging device package, which is made of borosilicate glass containing no alkali metal oxide and containing no CeO ₂ . The borosilicate glass is Sn% by mass. ₂   The window glass for a solid-state imaging device package according to claim 1, comprising 0.002 to 0.04%. The borosilicate glass is substantially free of MgO, CaO, SrO, BaO, and ZnO, and emits α rays from the glass to less than 0.0002 c / cm ² · h. Item 3. The window glass for a solid-state imaging device package according to Item 1 or 2