Method of fabricating a multilayer ceramic capacitor
First Claim
1. A method of making a multilayer ceramic capacitor comprising the steps of:
- selecting a dielectric composition powder as a base material;
adding predetermined amounts of organic materials functioning as liquifiers, binders and plasticizers, the organic materials being easily evaporated and sublimed substantially below the sintering temperature, and adding selected dopants in powder form in predetermined amounts;
ball milling the combination of dielectric composition, dopants and organic materials to form a fully dispersed colloidal suspension slip and for a sufficient time to reduce the composition to particles having a predetermined size range;
casting the slip on a sheet of polyester film in tape form at an elevated temperature to evaporate a significant portion of the organics added to the dielectric composition powder, thereby forming a green tape;
forming a multilayer capacitor laminate green capacitor body of alternate layers of ceramic blanks formed from the green tape and electrodes by lamination under pressure, the electrodes as applied to the ceramic blanks being perforated within multiplicity of holes through which ceramic material passes during the laminating process;
completing removal of the organics by subjecting the green capacitor body to predetermined temperatures for predetermined periods of time according to a first schedule to form a partially cured capacitor;
sintering the partially cured capacitor at further predetermined temperatures for predetermined periods of time according to a second schedule; and
adding terminations to make selective electrical connection with the electrodes in the ceramic capacitor.
2 Assignments
0 Petitions
Accused Products
Abstract
A method of fabricating a large, rectangular, multilayer ceramic capacitor formed of alternating ceramic and electrode layers. Capacitors so formed have a high dielectric constant, extremely low leakage current and an extremely low dissipation factor. Exemplary capacitors can be made with a lead magnesium niobate dielectric composition powder to which is added several organic constituents, including a surfactant and a plasticizer, plus small amounts of several dopants, such as lithium niobate, copper oxide, magnesium titanate, manganese niobate and zirconium oxide. That total mixture is ball milled to form a slip with very small grain size. The slip is cast as a thin tape on a Mylar backing, cut into a plurality of blanks, and alternating layers of the green tape ceramic and electrode layers are laminated on a polyvinyl alcohol coated foundation plate. Firing and sintering steps are followed by application of electrical terminations to complete the capacitor. The final package is annealed to further improve the dielectric constant and the dissipation factor.
38 Citations
12 Claims
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1. A method of making a multilayer ceramic capacitor comprising the steps of:
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selecting a dielectric composition powder as a base material; adding predetermined amounts of organic materials functioning as liquifiers, binders and plasticizers, the organic materials being easily evaporated and sublimed substantially below the sintering temperature, and adding selected dopants in powder form in predetermined amounts; ball milling the combination of dielectric composition, dopants and organic materials to form a fully dispersed colloidal suspension slip and for a sufficient time to reduce the composition to particles having a predetermined size range; casting the slip on a sheet of polyester film in tape form at an elevated temperature to evaporate a significant portion of the organics added to the dielectric composition powder, thereby forming a green tape; forming a multilayer capacitor laminate green capacitor body of alternate layers of ceramic blanks formed from the green tape and electrodes by lamination under pressure, the electrodes as applied to the ceramic blanks being perforated within multiplicity of holes through which ceramic material passes during the laminating process; completing removal of the organics by subjecting the green capacitor body to predetermined temperatures for predetermined periods of time according to a first schedule to form a partially cured capacitor; sintering the partially cured capacitor at further predetermined temperatures for predetermined periods of time according to a second schedule; and adding terminations to make selective electrical connection with the electrodes in the ceramic capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of making a multilayer ceramic capacitor comprising the steps of:
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selecting a dielectric composition powder as a base material; adding predetermined amounts of organic materials functioning as liquifiers, binders and plasticizers, the organic materials being easily evaporated and sublimed substantially below the sintering temperature, and adding selected dopants in powder form in predetermined amounts; ball milling the combination of dielectric composition, dopants and organic materials to form a fully dispersed colloidal suspension slip and for a sufficient time to reduce the composition to particles a predetermined size range; casting the slip on a sheet of polyester film at an elevated temperature to evaporate a significant portion of the organics added to the dielectric composition powder, thereby forming a green tape; forming a multilayer green capacitor body of alternate layers of green tape and electrodes by lamination under pressure; completing removal of the organics by subjecting the green capacitor body to predetermined temperatures for predetermined periods of time according to a first schedule to form a partially cured capacitor, the first schedule comprising the steps of; placing the green capacitor body in an oven;
thenramping up the temperature in the oven at about 0.5°
to 2.0°
C. per minute to a level of about 295°
to 310°
C.;maintaining the oven temperature at about 295°
to 310°
C. for about 36 hours;
then ramping up the temperature in the oven at about 400°
to 500°
C.;maintaining the oven temperature at about 400°
to 500°
C. for about 24 hours; and
thenramping the oven temperature down to room temperature at about 30°
C. per minute;sintering the partially cured capacitor at further predetermined temperatures for predetermined periods of time according to a second schedule; and adding terminations to make selective electrical connection with the electrodes in the ceramic capacitor.
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12. A method of making a multilayer ceramic capacitor comprising the steps of:
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selecting a dielectric composition powder as a base material; adding predetermined amounts of organic materials functioning as liquifiers, binders and plasticizers, the organic materials being easily evaporated and sublimed substantially below the sintering temperature, and adding selected dopants in powder form in predetermined amounts; ball milling the combination of dielectric composition, dopants and organic materials to form a fully dispersed colloidal suspension slip and for a sufficient time to reduce the composition to particles having a predetermined size range; casting the slip on a sheet of polyester film in tape form at an elevated temperature to evaporate a significant portion of the organics added to the dielectric composition powder, thereby forming a green tape; forming a multilayer green capacitor body of alternate layers of green tape and electrodes by lamination under pressure; completing removal of the organics by subjecting the green capacitor body to predetermined temperatures for predetermined periods of time according to a first schedule to form a partially cured capacitor; sintering the partially cured capacitor at further predetermined temperatures for predetermined periods of time according to a second schedule, the second schedule comprising the steps of; placing the partially cured capacitor in a kiln;
thenramping up the temperature in the kiln at about 10°
-30°
C. per minute to a level of about 940°
-960°
C.;maintaining the kiln temperature at about 940°
-960°
C. for about 40-80 minutes;
thenramping down the kiln temperature at about 10°
-40°
C. per minute to a level of about 700°
-800°
C.;annealing the sintered capacitor by maintaining the kiln temperature at about 700°
-800°
C. for about 100-140 minutes; and
thenturning off the kiln and allowing it to cool; and adding terminations to make selective electrical connection with the electrodes in the ceramic capacitor.
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Specification