Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2000-07-28
2002-07-02
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C501S002000, C501S010000, C106S031050
Reexamination Certificate
active
06413619
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of marking ceramic member made of ceramics, a low-temperature fired material and glass, which is used as an insulating substrate of a package for containing a semiconductor device, and a marked ceramic member.
BACKGROUND OF THE INVENTION
As a package for containing a semiconductor device, which is used for containing a semiconductor device, particularly a semiconductor integrated circuit device, for example, those comprising a package body made of ceramics such as alumina ceramics, low-temperature fired ceramics and electrical insulating materials such as glass, and an external lead terminal for electrically connecting the semiconductor device to an external circuit have been known.
In the package for containing the semiconductor device, a mark is formed occasionally on the external surface of the package in order to enable an operator or an automatic assembling machine to recognize product information such as product number and a direction of the package.
According to a conventionally known marking method, marking is conducted by irradiating the surface of the package body with laser light to solve the surface of the package body.
However, when using laser light, marking conditions drastically vary depending on characteristics such as heat resistance and color tone of a material to be marked such as package body. In case where the surface of the material to be marked shows a white or light color, it was difficult to form a clear contrast of color tone between the marking portion and the non-marking portion. Furthermore, a transparent product had such a drawback that the time required for marking becomes longer because laser light is easily transmitted.
To solve these drawbacks, various suggestions have hitherto been made. For example, Unexamined Patent Publication (Kokai) No. 4-210882 discloses a laser marking method comprising coating the surface of a ceramic member with a coating composition, irradiating the surface with laser light to form a mark, and removing the excessive coating composition. According to this method, since the coating composition is vaporized in a range irradiated with laser light and the surface of the ceramic member is carved, vapor of the coating composition is introduced into the formed concave portion, where the coating composition is solidified and deposited, and then baked to develop a black color.
Examined Patent Publication (Kokoku) No. 7-61551 discloses a laser marking method comprising irradiating a ceramic material or glass containing a radiation-sensitive additive made of an inorganic pigment such as zirconium vanadium yellow with laser light, thereby to induce a change in color in a range irradiated with laser light.
Unexamined Patent Publication (Kokai) No. 1-141091 discloses a laser marking method comprising etching the external surface of ceramics colored black by adding chromium oxide using a corrosive chemical such as hydrofluoric acid, and irradiating the etched surface with laser light to form a mark. According to this method, an original color of ceramics is lightened by the etching treatment, while the color changes to a deeper color within the laser light irradiation range so that a contrast of color between the range irradiated with laser light and the etched surface other than the range is enhanced, thereby making it easy to recognize the marking portion as the range irradiated with laser light.
The method described in Unexamined Patent Publication (Kokai) No. 4-210882 has such a drawback that the production cost becomes larger because of large number of processes such as coating of a coating composition, irradiation with laser light and removal of the coating composition.
The method of Examined Patent Publication (Kokoku) No. 7-61551 has such a drawback that, since a large amount of the additive (radiation-sensitive additive) other than the product composition such as ceramics and glass, an adverse influence is liable to be exerted on characteristics of the product and, therefore, the method can not be applied to only a product having a specific composition. Since control of a frequency of laser light is required to cause color change of the additive, process control becomes complicated.
The method described in Unexamined Patent Publication (Kokai) No. 1-141091 has such a drawback that, since the surface of ceramics is etched by using a corrosive chemical, when a metallized layer is formed on the surface of the ceramics, the strength of bonding between the metallized layer and ceramics is reduced. Since the process of etching is required, the number of processes increases, resulting in high production cost.
Furthermore, a conventional laser marking method has such a problem that, since the low-temperature fired material or glass product containing a large amount of a glass component hardly absorb laser light, the laser light irradiation time becomes larger, resulting in poor productivity.
SUMMARY OF THE INVENTION
A main object of the present invention is to provide a method of marking a ceramic member, capable of easily forming a mark having excellent visibility in a short time without increasing the number of processes.
Another object of the present invention is to provide a ceramic member on which a mark having excellent visibility is formed.
The present inventors have intensively studied to attain the objects described above. As a result, they have paid attention to the fact that a compound capable of developing different color tones by heating in different atmospheres exists, and found a new fact that a mark having excellent visibility can be formed easily in a short time without increasing the number of processes by containing the compound as a color changing agent in a ceramic green body, followed by firing in different atmospheres and further heat treatment. Thus, the present invention has been completed.
The marking method of the present invention comprises firing, in an atmosphere, a ceramic green body containing a color changing agent capable of developing different color tones by heating in different atmospheres, and heating a specific portion of the resulting sintered body in the other atmosphere to form a marking portion whose color tone is different from that of the other portion.
The different atmospheres are an oxidizing atmosphere and a reducing atmosphere, and the specific portion of the sintered body obtained by firing in any one of the atmospheres is heated in the other atmosphere.
The specific portion of the sintered body is preferably heated by irradiation with laser light, thereby making it possible to form a mark having excellent visibility in a short time.
The color changing agent includes, for example, a simple substance, an oxide or a composite oxide of at least one metal selected from the group consisting of Mn, Fe, V, Se and Cu. These metal elements or compounds have a property capable of changing the color tone by heating in different atmospheres.
At least 0.05% by weight of the color changing agent is preferably contained in the ceramic green body.
A ceramic member of the present invention has a marking portion, whose color tone is different from that of the other portion, formed on the surface. The ceramic member comprises ceramics containing a color changing agent, and the valence of the color changing agent in the marking portion is different from that of the color changing agent in the portion other than the marking portion.
In this case, the valence of the color changing agent in the marking portion is larger than that in the portion other than the marking portion.
The ceramics include, for example, glass ceramics. A circuit made of copper or silver is formed on the surface or in the ceramic member.
The other objects and advantages of the present invention will becomes apparent from the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the color changing agent capable of developing different color tones by heating in different atmospheres refers to the above-described compound capa
Furukubo Youji
Hamada Noriaki
Blackwell-Rudasill Gwendolyn
Hogan & Hartson L.L.P.
Jones Deborah
Kyocera Corporation
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