Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-06-05
2004-09-28
Mayes, Melvin C. (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S089160
Reexamination Certificate
active
06797093
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a glass ceramic multilayer substrate, and also relates to a glass ceramic multilayer substrate product obtained by using the manufacturing method. In detail, this invention relates to an improvement which can more reliably inhibit the undesired shrinkage that occurs in a sintering process for obtaining a glass ceramic multilayer substrate.
2. Description of the Related Art
When manufacturing a ceramic multilayer substrate having wiring conductors such as conductor film and via-hole conductor, the wiring conductors have to be subjected to sintering during the obtaining of the multilayer substrate. Accordingly, when a low resistance conductor such as Ag and Cu is used to form wiring conductors, the ceramic multilayer substrate has to be made of a material which can be sintered at a temperature equal to or lower than the melting point of Ag, Cu and the like. In order to meet such a requirement, a glass ceramic multilayer substrate has been put into actual use.
Usually, a glass ceramic multilayer substrate having wiring conductors formed by a low resistance conductor such as Ag, Cu may be manufactured in the following process. Namely, at first, a resin and a solvent are mixed into a powder mixture formed by a glass powder and a ceramic powder, so that a slurry is formed. This slurry is then formed into a plurality of sheets which can be used as green sheets. Subsequently, an electrically conductive paste containing an electrically conductive component which may be Ag or Cu is printed on the green sheets, thereby forming wiring conductors. Afterwards, a plurality of such green sheets each containing the wiring conductors are laminated one over another, thereby forming a laminated body which has not been sintered. Then, the laminated body is subjected to a sintering treatment, thereby obtaining the desired glass ceramic multilayer substrate.
However, the aforementioned sintering treatment has encountered the following problems. Namely, the shrinking behavior of the electrically conductive paste during the sintering process is different from that of the green sheets. Further, metal components contained in the electrically conductive paste will be dispersed into the glass material contained in the green sheets, and this will cause a change in the shrinking behavior of the glass material surrounding the wiring conductors. As a result, it is difficult to produce a glass ceramic multilayer substrate which is completely flat without any warpage.
Moreover, the sintering shrinkage of one glass ceramic multilayer substrate will not always be the same as that of another. This is because one batch of raw material can have a different quality from that of another, because the mixing ratio for making one group of green sheets can be different from the mixing ratio for making another group of green sheets, and further because the pressure for pressing one unsintered laminated body can be different from a pressure for pressing another unsintered laminated body. Under this circumstance, a conductor film formed on the outer surface of a glass ceramic multilayer substrate will often deviate from its correct position. As a result, the attachment size error will often go beyond an allowable range in a process where electronic parts are attached to a substrate in a manner as if flip chips are attached thereto, thus rendering it extremely difficult to ensure a high yield in an industrial production.
For this reason, it has long been demanded to provide an improved method for manufacturing an improved glass ceramic multilayer substrate, which method should satisfy the condition that when the sintering shrinkage in the plane direction of a glass ceramic multilayer substrate is small, and when its sintering process shrinking ratio (%) can be defined by the equation {(size before sintering)−(size after sintering)}×100/(size before sintering)}, the sintering process shrinking ratio is within 10%.
In order to meet the above requirement, Japanese Unexamined Patent Application Publication No. 4-243978 has suggested the following method for manufacturing an improved glass ceramic multilayer substrate. A plurality of green sheets each containing a glass powder and a ceramic powder as its solid components are laminated one above another to form an unsintered laminated body. Then, an arresting green sheet(s) containing as its solid component a ceramic powder which will not be sintered at a sintering temperature (this temperature is for sintering the unsintered laminated body) is/are laminated on one or both sides of the unsintered laminated body. If the sintering process is performed in such a state, it is possible to inhibit shrinkage in the plane direction of the laminated body, allowing a shrinkage only in the thickness direction, and thus producing a desired glass ceramic multilayer substrate having a high flatness. In this way, the above-described method makes it possible to manufacture a flat glass ceramic multilayer substrate.
However, the arresting green sheet(s) formed on one or both sides of the unsintered laminated body in the above-described method will have to be removed after the sintering process is over. Such green sheet(s) will not form part of the laminated product. Because of this, the total cost for manufacturing a glass ceramic multilayer substrate is high, since the entire manufacturing cost will include a cost for forming the arresting green sheet(s) and also a cost for removing the arresting green sheet(s).
In view of the above, one of the most noticeable techniques during the last several years was suggested in Japanese Unexamined Patent Application Publication Nos. 6-97656 and 6-172017. These patent publications disclose a method which involves a sintering process, but which employs first green sheets having a certain shrinking behavior and second green sheets having a different shrinking behavior from that of the first green sheets. According to this method, it is possible to inhibit shrinkage in the plane direction of the laminated body by sintering an unsintered laminated body formed by laminating these green sheets, thereby making it possible to produce a flat glass ceramic multilayer substrate.
The basic technical principles disclosed in the above patent publications may be stated as follows.
When a sintering process is first carried out at a relatively low temperature corresponding to a sintering temperature for sintering the first green sheets, the first green sheets will tend to shrink. However, since the sintering temperature at this time is lower than the sintering temperature for sintering the second green sheets, the second green sheets will be kept in an unsintered state, thus having almost no shrinkage. For this reason, the shrinkage in the plane direction of the first green sheets can be inhibited by an arresting action of the second green sheets. Then, once another sintering process is carried out at a relatively high temperature corresponding to a sintering temperature for sintering the second green sheets, the second green sheets will tend to shrink. At this time, the shrinkage in the plane direction of the second green sheets will be inhibited by an arresting action of the sintered first green sheets. In this way, the sintering shrinkage of the laminated body is greatly inhibited so that it occurs only in the thickness direction of the laminated body, with almost no shrinkage occurring in the plane direction thereof. As a result, it is possible to produce an improved glass ceramic multilayer substrate having a reduced shrinkage and an increased flatness.
However, the glass ceramic multilayer substrate manufacturing method disclosed in Japanese Unexamined Patent Application Publication Nos. 6-97656 and 6-172017 also has a problem that in carrying out the process disclosed in these patent publications, it will sometimes be difficult to sufficiently inhibit shrinkage in the plane direction of a laminated body during the sintering proce
Chikagawa Osamu
Moriya Yoichi
Sugimoto Yasutaka
Dickstein , Shapiro, Morin & Oshinsky, LLP
Mayes Melvin C.
Murata Manufacturing Co. Ltd.
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