Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2001-02-20
2002-06-11
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C501S010000, C501S011000
Reexamination Certificate
active
06403200
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to insulator ceramic compositions used, for example, for multilayer circuit substrates, and more specifically, it relates to insulator ceramic compositions which can be appropriately used for hybrid multilayer circuit substrates in order to mount semiconductor elements and various electronic parts, and which can be fired together with conductive materials such as copper and silver.
2. Description of the Related Art
In recent years, high-speed and high frequency electronic equipment has been increased. In electronic parts mounted on the electronic equipment, high-speed and the high integration are required too, and furthermore, a highly densified mounting is required. In order to fulfill the aforementioned requirements, multilayer circuit substrates have hitherto been used as substrates for mounting the semiconductor elements and various electronic parts thereon. In the multilayer circuit substrates, conductor circuits and electronic part functional elements are integrated in the substrates so that the electronic equipment can be miniaturized.
As the materials constituting the aforementioned multilayer circuit substrates, alumina has been used frequently.
The firing temperature of alumina is relatively high at 1500 to 1600° C. Therefore, as the materials of the conductor circuits integrated in the multilayer circuit substrates made of alumina, high melting point metals, for example, Mo, Mo—Mn, and W, usually had to be used. There was a problem, however, in that these high melting point metals exhibit high electrical resistance.
Therefore, it is strongly required to use, as a conductor material, a low electrical resistance and inexpensive metal as copper compared to the aforementioned high melting point metals. In order to make it possible to use copper as a conductor material, it was proposed to use glass ceramics, crystallized glass, etc., which can be fired at a low temperature of 1000° C. or less (for example, Japanese Unexamined Patent Application Publication No.5-238774).
There was a problem, however, in that the aforementioned well-known substrate materials capable to being fired at a low temperature are likely not to fulfill the high mechanical strength and the high Q value requirements together.
SUMMARY OF THE INVENTION
The object of the present invention is to conquer the aforementioned drawbacks in the conventional techniques so as to provide an insulator ceramic which can be obtained by low temperature firing, can be fired together with relatively low melting point conductor materials such as silver and copper, exhibits superior mechanical strength, exhibits high Q value and exhibits superior high frequency characteristics.
Another object of the present invention is to provide a ceramic multilayer substrate, a ceramic electronic part and a laminated ceramic electronic part which are constituted using the aforementioned insulator ceramic, exhibit superior mechanical strength, exhibit high Q value and exhibit superior high frequency characteristics.
The present invention was made to solve the aforementioned problems. An insulator ceramic composition according to the present invention is characterized in comprising: (A) an MgO—MgAl
2
O
4
ceramic powder; and (B) a glass powder containing silicon oxide in a proportion of about 13 to 50 weight % in terms of SiO
2
, boron oxide in a proportion of about 3 to 60 weight % in terms of B
2
O
3
, and aluminum oxide in a proportion of 0 to about 20 weight % in terms of Al
2
O
3
.
In 100 weight % of the aforementioned glass powder, silicon oxide is contained in a proportion of about 13 to 50 weight %, preferably about 20 to 30 weight % in terms of SiO
2
. When the content of silicon oxide is about 13 weight % or less, the degree of crystallinity of the obtained sintered material is lowered, and the Q value is lowered. On the contrary, when the content of silicon oxide is about 50 weight % or more, the melting point of the glass is increased.
In the aforementioned glass powder, boron oxide is contained in a proportion of about 3 to 60 weight %, preferably about 30 to 60 weight % in terms of B
2
O
3
. Boron oxide primarily functions as a flux. When the content of boron oxide is about 3 weight % or less in terms of B
2
O
3
, the melting point becomes too high, on the contrary, when more than about 60 weight %, the moisture resistance of the obtained sintered material is lowered.
Furthermore, in the aforementioned glass powder, aluminum oxide is contained in a proportion of 0 to about 20 weight % in terms of Al
2
O
3
. The content of aluminum oxide may be 0 weight % in terms of Al
2
O
3
. That is, aluminum oxide is not necessarily contained. Therefore, the insulator ceramic composition according to the present invention containing no aluminum oxide is expressed as the insulator ceramic composition comprising the aforementioned (A) an MgO—MgAl
2
O
4
ceramic powder, and (B) a glass powder containing silicon oxide in a proportion of about 13 to 50 weight % in terms of SiO
2
and boron oxide in a proportion of about 3 to 60 weight % in terms of B
2
O
3
.
In the case in which the aforementioned aluminum oxide is present, when the content is more than about 20 weight % in terms of Al
2
O
3
, a fine sintered material cannot be obtained, and the Q value becomes small. In the case in which aluminum oxide is present, the lower limit thereof is more than 0 weight % in terms of Al
2
O
3
.
In the present invention, as the aforementioned glass powder, the one further containing at least an alkaline earth metal oxide selected from the group consisting of BaO, SrO, CaO and MgO in a proportion of about 10 to 40 weight % relative to the entirety of the aforementioned glass powder is preferable. More preferably, the aforementioned alkaline earth metal oxide is added to be contained in a proportion of about 20 to 30 weight % relative to the entirety of the glass powder.
The aforementioned alkaline earth metal oxide has a function of lowering the melting temperature in the manufacturing of the glass and functions as a component constituting the crystal in the crystallized glass. When the content of the aforementioned alkaline-earth metal oxide is less than about 10 weight %, the melting temperature may be increased, and when more than about 40 weight %, the deposition amount of crystals may be increased and the strength of the substrate may be lowered.
In another aspect of the present invention, the aforementioned glass powder contains at least an alkali metal oxide selected from the group consisting of Li
2
O, K
2
O and Na
2
O preferably in a proportion of about 10 weight % or less, more preferably in a proportion of about 2 to 5 weight %, relative to the entirety of the glass powder. The alkali metal oxide has a function of lowering the melting temperature. When the content of the alkali metal oxide is more than about 10 weight %, the Q value may be lowered.
In the present invention, the aforementioned insulator ceramic composition may contain zinc oxide, preferably in a proportion of about 15 weight % or less, more preferably in a proportion of about 10 weight % or less, in terms of ZnO. Zinc oxide has a function of lowering the firing temperature. When the content of the zinc oxide, however, is more than about 15 weight % in terms of ZnO, a fine sintered material may not be obtained. The aforementioned zinc oxide may be contained as a glass component.
In the present invention, copper oxide is contained preferably in a proportion of about 3 weight % or less, more preferably in a proportion of about 2 weight % or less relative to the entirety, in terms of CuO. Copper oxide has a function of lowering the firing temperature. When the content of the copper oxide, however, is more than about 3 weight %, the Q value may be lowered.
In a specified aspect of the present invention, when the composition in weight ratio of the aforementioned MgO—MgAl
2
O
4
ceramic powder is represented by the formula, xMgO—yMgAl
2
O
4
, the x and y are preferably constituted fulfilling the rela
Chikagawa Osamu
Mori Naoya
Blackwell-Rudasill Gwendolyn
Jones Deborah
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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