Printed circuit board capacitor structure and method

• US 20010005304A1
• Filed: 02/01/2001
• Published: 06/28/2001
• Est. Priority Date: 11/05/1998
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lauffer, John M., Appelt, Bernd K.
• Granted Patent: US 6,625,857 B2
• Time in Patent Office: Days
• US Class Current: 361/312
• 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 29/435 Solid dielectric type
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49144 by metal fusion
• CPC Class Codes: Y10T 29/5102 Binding or covering and cutting

Abstract

A capacitive element for a circuit board or chip carrier having improved capacitance and method of manufacturing the same is provided. The structure 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 or softened followed by being fully cured or hardened. The lamination takes place by laminating a partially cured or softened sheet 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; thus the single dielectric sheets does not exceed about 2 mils and preferably does not exceed about 1.5 mils in thickness. 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 method of forming a capacitive element comprising the steps of:

selecting first and second sheets of electrically conducting material;

providing first and second layers of dielectric material between said sheets of electrically conducting material, said layers being either partially cured or softened, each of said layers being no thicker than about 2 mils;

laminating said layers of dielectric material together and to said sheets of conducting material, and fully curing or hardening said layers of dielectric material to form a capacitive structure with a dielectric component having a thickness of less than about 4 mils.

2. The method of

claim 1

wherein at least one of said layers of dielectric material is a glass cloth impregnated with a thermoset resin, and which thermoset resin is partially cured prior to lamination.

3. The invention as defined in

claim 1

wherein each of said layers of dielectric material is a glass cloth impregnated with a thermoset resin.

4. The invention as defined in

claim 3

wherein each of said layers of impregnated glass cloth are discrete elements before they are laminated to the sheets of conductive material.

5. The invention as defined in

claim 3

wherein at least one of said layers of impregnated glass cloth is first laminated to one of said sheets of conducting material prior to the lamination of both of the sheets of conducting material to both sheets of glass cloth.

6. The invention as defined as

claim 5

wherein each of said layers of glass cloth are laminated to one of said sheets of conducting material before the sheets of conducting material are laminated to both layers of glass cloth.

7. The invention as defined in

claim 2

wherein the thermoset resin is an epoxy.

8. The invention as defined in

claim 1

wherein at least one of the sheets of dielectric material is provided as a dry film.

9. The invention as defined in

claim 1

wherein at least one of the sheets of dielectric material is formed by coating a dielectric material on one of said sheets of conducting material and at least partially curing said coated material.

10. The invention as defined in

claim 1

wherein a third sheet of dielectric material is laminated between said first and second sheets of dielectric material.

11. The invention as defined in

claim 10

wherein the third sheet of dielectric material is provided as a dry film of material and the first and second sheets are formed by coatings on opposite sides of said third sheet of dielectric material.

12. The invention as defined in

claim 1

wherein said first and second sheets of dielectric material are different materials.

13. The invention as defined in

claim 12

wherein one of said dielectric sheets of material is a thermoplastic and one is a thermoset.

14. A method of forming a capacitive element comprising the steps of;

impregnating sheets of glass cloth with a epoxy resin;

curing said epoxy resin to a B-stage thereby forming dielectric sheets;

selecting at least two of said dielectric sheets which have a total thickness of no more than about 4 mils;

selecting two sheets of electrically conducting material;

forming a lay-up by stacking said sheets of electrically conducting material with the sheets of dielectric material sandwiched therebetween; and

laminating said lay-up to bond said dielectric sheets to said electrically conducting sheets and to each other and to fully cure said epoxy resin.

15. The invention as defined in

claim 14

wherein said dielectric component has a thickness of less than about 3 mils.

16. The invention as defined in

claim 14

wherein the dielectric component has a thickness of no more than about 2 mils.

17. A capacitive element, comprising;

at least two sheets of dielectric material, each sheet having a thickness of no more than about 2 mils, said sheets of dielectric material being bonded together to form a dielectric component having a thickness of no more than about 4 mils;

first and second sheets of conductive material;

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

18. The invention as defined in

claim 17

wherein said sheets of dielectric material contain at least one resin impregnated sheet of glass cloth.

19. The invention as defined in

claim 17

wherein there are at least two different types of dielectric sheets.

20. The invention as defined in

claim 17

wherein there are three sheets of dielectric material.

21. The invention as defined in

claim 18

wherein the sheets of cloth incorporate an epoxy resin which is fully cured.

22. A printed circuit board, comprising at least one capacitive element,

each said capacitive element comprising at least two sheets of dielectric material, each sheet having a thickness of no more than about 2 mils, said sheets of dielectric material being bonded together to form a dielectric component having a thickness of no more than about 4 mils;

first and second sheets of conductive material;

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

a layer dielectric material on each of said sheets of conductive material, and electric circuitry on at least one layer of said dielectric material connected to at least one of said sheets of conductive material.

23. The invention as defined in

claim 22

wherein there are electrical circuits on both layers of dielectric material.

24. The invention as defined in

claim 22

wherein there are at least two capacitive elements.

25. The invention as defined in

claim 23

wherein there is at least one signal plane interposed between two or adjacent one of said capacitive elements.

26. The invention as defined in

claim 23

wherein there are two signal planes interposed between two of said capacitive elements.