Printed circuit board capacitor structure and method

• US 6,815,085 B2
• Filed: 05/12/2003
• Issued: 11/09/2004
• Est. Priority Date: 11/05/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Appelt, Bernd K., Lauffer, John M.
• Primary Examiner(s): La Villa, Michael
• Application Number:
  US10/436,335
• Publication Number:
  US 20030202314A1
• Time in Patent Office: 547 Days
• Field of Search: 428/325, 428/626, 428/630, 428/674, 428/113, 428/190, 428/220, 428/297.4, 428/300.7, 428/301.4, 428/335, 428/339, 428/426, 428/432, 428/433, 428/416, 428/417, 428/418, 428/336, 361/271, 361/311, 361/312, 361/313, 361/314, 361/321.1, 361/321.5, 361/324
• US Class Current: 428/626
• CPC Class Codes: H05K 1/0366 reinforced, e.g. by fibres, fabrics H05K1/036 takes precedence
• CPC Class Codes: H05K 1/162 incorporating printed capacitors
• CPC Class Codes: H05K 2201/0195 Dielectric or adhesive layers comprising a plurality of layers, e.g. in a multilayer structure
• CPC Class Codes: H05K 2201/0209 Inorganic, non-metallic particles
• CPC Class Codes: H05K 2201/0355 Metal foils
• CPC Class Codes: H05K 2201/09309 Core having two or more power planes; Capacitive laminate of two power planes
• CPC Class Codes: H05K 3/429 Plated through-holes specially for multilayer circuits, e.g. having connections to inner circuit layers
• CPC Class Codes: H05K 3/4641 having integrally laminated metal sheets or special power cores
• CPC Class Codes: Y10T 428/12569 Synthetic resin
• CPC Class Codes: Y10T 428/12597 Noncrystalline silica or noncrystalline plural-oxide component [e.g., glass, etc.]
• CPC Class Codes: Y10T 428/12903 Cu-base component
• CPC Class Codes: Y10T 428/24124 Fibers
• CPC Class Codes: Y10T 428/2476 Fabric, cloth or textile component
• CPC Class Codes: Y10T 428/24994 Fiber embedded in or on the surface of a polymeric matrix
• CPC Class Codes: Y10T 428/249952 At least one thermosetting synthetic polymeric material layer
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/264 Up to 3 mils
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/269 including synthetic resin or polymer layer or component

Abstract

A capacitive element for a circuit board or chip carrier is formed from a pair of conductive sheets having a dielectric component laminated therebetween. The dielectric component is formed of two or more dielectric sheets, at least one of which can be partially cured followed by being fully cured. The partially cured sheet is laminated to at least one other sheet of dielectric material and one of the sheets of conductive material. The total thickness of the two sheets of the dielectric component does not exceed about 4 mils and preferably does not exceed about 3 mils. The use of two or more sheets of dielectric material makes it very unlikely that two or more defects in the sheets of dielectric material will align, thus greatly reducing the probability of a defect causing a failure in test or field use.

Claims

1. A capacitive element, comprising:

two sheets of thermoplastic or thermosetting resinous dielectric material, each sheet having a thickness of less than about 1 mil and each sheet comprising a sheet of glass cloth impregnated with a resin, said sheets of dielectric material being formed from different dielectric materials and being bonded together to form a dielectric component being free of pin hole defects, said dielectric component having a total thickness of less than about 2 mils; and

first and second sheets of conductive material;

wherein

said dielectric component is laminated between said first and second sheets of conductive material and is fully cured or hardened.

2. The capacitive element according to claim 1 wherein at least one of the sheets of glass cloth is impregnated with an epoxy resin which is fully cured.

3. The capacitive element according to claim 1 wherein at least one of the dielectric sheets is filled with particles having a high dielectric constant, the particles having a size distribution between about 0.1 microns and about one-half of the thickness of the sheet.

4. The capacitive element according to claim 3 wherein the particles are selected from the group consisting of barium titanate, strontium titanate, lead-zinc titanate, tantalum oxide and mixtures thereof.

5. The capacitive element according to claim 1 wherein the capacitance of the element is at least about 500 pico farads per square inch.

6. A capacitive element, comprising:

three sheets of thermoplastic or thermosetting resinous dielectric material, each of the sheets having a thickness of less than about 1 mil and comprising a sheet of glass cloth, and each of said sheets of dielectric material impregnated with a resin, said sheets being bonded together to form a dielectric component being free of pin bole defects, and having a total thickness of less than about 3 mils; and

first and second sheets of conductive material;

wherein

said dielectric component is laminated between said first and second sheets of conductive material and is fully cured or hardened.

7. The capacitive element according to claim 6 wherein at least one of the three sheets of glass cloth is impregnated with an epoxy resin.

8. The capacitive element according to claim 6 wherein at least one of the dielectric sheets is filled with particles having a high dielectric constant, the particles having a size distribution between about 0.1 microns and about one-half of the thickness of the sheet.

9. The capacitive element according to claim 8 wherein the particles are selected from the group comprising barium titanate, strontium titanate, lead-zinc titanate, tantalum oxide and mixtures thereof.

10. The capacitive element according to claim 6 wherein the capacitance is at least about 500 pico farads per square inch.

11. The capacitive element according to claim 6 wherein at least two of the sheets of dielectric material are formed from different resinous dielectric materials.