JPS62153142A - Ultraviolet ray transmitting glass - Google Patents

Abstract

PURPOSE:To obtain ultravilet ray transmitting glass having >=60% transmittanceat 254nm wavelength of glass with 11mm wall thickness thereof and 45-55X10<-7>/ deg.C average linear expansion coefficient, by providing a composition consisting of SiO2, B2O3, alkali metal oxide, alkaline earth metal oxide and ZnO of specific blend. CONSTITUTION:Raw materials are mixed to give the composition of ultraviolet ray transmitting glass as follows; 70-75wt% SiO2, 12-17wt% B2O3, 1-3wt% Al2O3, 4-8wt% total of Na2O, K2) and Li2O and 1-4wt% total of MgO, CaO, ZnO, BaO and SrO. For example, about 0.3wt% carbon as a reducing agent is added and the resultant blend is melted in an electric furnace, cast into a mold and anneaeld to afford the aimed ultraviolet ray transmitting glass.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to ultraviolet light transmitting glass, particularly ultraviolet erasable type E glass.
The present invention relates to an ultraviolet transmitting glass suitable for sealing with a metal frame as a PROM window.

[Conventional technology]

Conventionally, an alumina ceramic package has been used as a support for a storage semiconductor device EPROM (hereinafter referred to as EPROM), which can erase memory contents by irradiating an IC memory chip with ultraviolet rays, and a glass window for ultraviolet irradiation has been attached directly or in a frame to this package. It is attached through material. The manufacturing method for this ultraviolet-transmitting window involves placing a piece of glass on a frame material such as Kovar metal, sealing it to the frame material by softening and fusing the glass, and at the same time fire-polishing the glass so that the center is lens-shaped. A method is known in which glass is attached to a semiconductor package to form a window. In this method, borosilicate glass has mainly been used because of its good sealing properties.

[Problem that the invention seeks to solve]

The glass used for the glass core is required to have a coefficient of thermal expansion of about 45 to 55XlO-7/°C. Examples of glasses with a coefficient of thermal expansion of 45 to 55 x 10"-77C include borosilicate glass and aluminosilicate glass. However, these conventional glasses usually have an E.
Wavelength 2 of a mercury lamp used as a light source for erasing PROM
The transmittance at 54 nm is low, and when used in EPROM 2, there is a drawback that memory erasing efficiency by ultraviolet irradiation is low. Glasses with high ultraviolet transmittance include quartz glass and phosphate glass, with thermal expansion coefficients of 45 to 5.
There is no one in the 5xy range, and it cannot be sealed with Kovar metal.

The present invention has been made in consideration of the above circumstances, and has a glass thickness of 1.111, a transmittance of 60% or more at a wavelength of 254nrl, and a thermal expansion coefficient of 45 to 55XIO-7/
The present invention provides a glass having C.

[Failure to solve the problem]

The present invention has a weight percentage of Sigh 70-75%, 82
O゜12-17%, AlzOa 1-3%, Na, O+
K2O+Liz04~8%, MgO+ CaO+ Z
It has a composition of nO+ BaO+SrO 1 to 4%, and the transmittance of the glass is 1.1 mm thick at wavelength 2.
60% or more at 54 nm, and an average linear expansion coefficient of 4
It is an ultraviolet transmitting glass characterized by having a particle diameter of 5 to 55 x 10-7/''C.

Next, the reason for limiting the values of each component of the glass will be explained.

SiO2 is the main component forming glass, but if it exceeds 75%, the meltability will deteriorate, and if it is less than 70%, the ultraviolet transmittance will decrease due to the relative relationship with other components.

If B2O2 exceeds 17%, chemical durability deteriorates12
If it is less than %, the ultraviolet transmittance will decrease and the meltability will also deteriorate.

A12Oa works to increase chemical durability, but 3%
If it exceeds 1%, meltability deteriorates, and if it is less than 1%, there is no effect of improving chemical durability.

If the alkali metal oxide exceeds 8%, the chemical strength and durability will deteriorate, and the ultraviolet transmittance will also decrease, and if it is less than 4%, the coefficient of thermal expansion will become small and the meltability will deteriorate.

When the alkaline earth metal oxide and Zn○ exceed 4%, the ultraviolet transmittance decreases, and when it is less than 196%, the meltability and chemical durability deteriorate.

Further, as a substance that increases ultraviolet absorption, there is iron mixed in as an impurity. Of the iron, Fe3+ has particularly large absorption in the ultraviolet region, and is a cause of lowering the ultraviolet transmittance. Therefore, it is necessary to reduce the iron content, which is an impurity, and convert Fe3+ to Fe2+ by reduction.
Reducing e3+ is also effective in improving ultraviolet transmittance. This is achieved by adding and melting a reducing agent to a batch of glass raw materials, and effective reducing agents include carbon, tartaric acid, metallic silicon, and metallic aluminum. However, the iron content in the raw material is toopppm by weight.
If the following, an oxidizing refining agent such as As2O,
Sb2O. may be used together with an oxidizing agent.

[For production]

Due to the above composition, the transmittance at a wavelength of 254 nm at a wall thickness of 1.1 mm is 6096 or more, and the coefficient of thermal expansion is similar to that of Kovar metal, that is, the average coefficient of thermal expansion is 45 to 55.
A glass having X 10-'/'C is obtained.

〔Example〕

Next, examples of the present invention will be described. Glass compositions in the table are shown in weight %.

(Left below) Raw materials were prepared to have the glass composition shown above, and after adding 0.3% by weight of carbon as a reducing agent, the mixture was placed in a platinum crucible and heated in an electric furnace at 1400°C to 1480°C for 3 hours. After melting, a sample was taken from the mold and slowly cooled.
．． A glass plate was polished to prepare a sample for ultraviolet transmittance measurement. As can be seen here, the glass of this example has a thermal expansion coefficient of 46 to 53XIO-'/°C and can be sealed with Kovar metal, and also has a transmittance of 7
It achieves a high transmittance of 3 to 79%.

Note that the present invention is not limited to the above embodiments,
By adjusting the thermal expansion coefficient, sealing with alumina ceramics is possible, and it can also be applied to commonly used semiconductor-related alumina packages.

〔Effect of the invention〕

As described above, the glass of the present invention has a high ultraviolet transmittance, so when used as an ultraviolet transmitting window of an E P ROM, memory erasure by ultraviolet irradiation can be carried out efficiently. Since it has a coefficient of expansion, it can be easily sealed with Kovar metal, and is extremely suitable as a window glass for EPROMs whose window frames are made of metal such as Kovar metal.

Claims (1)

[Claims] SiO_2 70-75% by weight percentage, B_2O_3
12-17%, Al_2O_3 1-3%, Na_2
O+K_2O+Li_2O 4-8%, MgO+CaO
+ZnO+BaO+SrO having a composition of 1 to 4%, the transmittance of the glass is 60% or more at a wavelength of 254 nm in glass with a wall thickness of 1.1 mm, and the average linear expansion coefficient is 45 to 55 x 10^-^7/ UV-transparent glass characterized by a temperature of ℃.