Production method for a multilayer ceramic substrate
An object of the invention is to connect different dielectrics electrically to each other in the direction of main surface of a sheet in a multilayer ceramic substrate and to increase the degree of flexibility in design and make the multilayer ceramic substrate compact in size. A multilayer ceramic substrate in accordance with the invention is formed of a plurality of laminated ceramic substrates including such a composite ceramic substrate of different materials that is made by inserting the second ceramic substrate in a pounched-out portion made in the first ceramic substrate and by planarizing its top and bottom surfaces, wherein a conductive layer is formed in a portion across a boundary between the first ceramic substrate and the second ceramic substrate of the interface of the composite ceramic substrate of different materials.
1. A production method of a multilayer ceramic substrate, comprising the steps of:
punching out a predetermined portion of a first green sheet attached to a support sheet;
overlaying a second green sheet peeled off from the support sheet on the first green sheet attached to the support sheet and bonding them provisionally;
inserting the second green sheet in the punched-out portion of the first green sheet attached to the support sheet to form a composite green sheet of different materials;
peeling off the second green sheet provisionally bonded to a surface of the first green sheet attached to the support sheet;
peeling off the support sheet from the first green sheet;
overlaying a plurality of composite green sheets of different materials and pressing them to mold a green sheet laminate; and
firing the green sheet laminate.
2. The production method of a multilayer ceramic substrate according to claim 1 , further comprising a step of bonding the composite green sheet of different materials to a second support sheet having no punched hole after the step of peeling off the second green sheet provisionally bonded to a surface of the first green sheet.
3. The production method of a multilayer ceramic substrate according to claim 1 , further comprising a step of forming a via hole in any one or both of the first green sheet and the second green sheet.
4. The production method of a multilayer ceramic substrate according to claim 1 , wherein, when the green sheet laminate is formed, the punched portions of the first green sheets are mated with each other in such a way that the second green sheets have portions overlapping each other above and below in a direction of lamination, a conductive paste is printed on a surface of the second green sheets inserted in the punched portions, and an internal conductive layer is interposed between the second green sheets.
5. The production method of a multilayer ceramic substrate according to claim 1 , wherein the first green sheet and the second green sheet are formed of materials whose dielectric constants are different from each other after firing.
6. The production method of a multilayer ceramic substrate according to claim 1 , wherein the first green sheet and the second green sheet are equal in thickness to each other.
7. The production method of a multilayer ceramic substrate according to claim 1 , wherein the first green sheet and the second green sheet have the same level of pressing compressibility and the same level of firing shrinkage.
8. The production method of a multilayer ceramic substrate according to any one of claims 1 to 3 , further comprising a step of printing a conductive paste on the composite green sheet of different materials.
9. The production method of a multilayer ceramic substrate according to claim 8 , wherein, in the step of printing a conductive paste on the composite green sheet of different materials, the conductive paste is printed across a boundary between the first green sheet and the second green sheet.