Circuit board and production of the same

• US 20030066683A1
• Filed: 10/25/2002
• Published: 04/10/2003
• Est. Priority Date: 08/21/2000
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Suzuki, Takeshi, Matsuoka, Susumu, Echigo, Fumio, Tomekawa, Satoru, Ogawa, Tatsuo, Nakatani, Yasuhiro, Ueda, Yoji, Andoh, Daizo, Bessho, Yoshihiro
• Granted Patent: US 6,691,409 B2
• Time in Patent Office: Days
• US Class Current: 174/262
• CPC Class Codes: H05K 1/036 Multilayers with layers of different types
• CPC Class Codes: H05K 1/0373 containing additives, e.g. fillers H05K1/036 takes precedence
• 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 2201/068 wherein the coefficient of thermal expansion is important
• CPC Class Codes: H05K 2203/1461 Applying or finishing the circuit pattern after another process, e.g. after filling of vias with conductive paste, after making printed resistors
• CPC Class Codes: H05K 3/20 by affixing prefabricated conductor pattern H05K1/187, H05K3/046, H05K3/4658, H05K3/4682 takes precedence
• CPC Class Codes: H05K 3/202 using self-supporting metal foil pattern
• CPC Class Codes: H05K 3/4069 for via connections in organic insulating substrates
• CPC Class Codes: H05K 3/4614 the electrical connections between the circuit boards being made during lamination
• CPC Class Codes: H05K 3/4652 Adding a circuit layer by laminating a metal foil or a preformed metal foil pattern H05K3/4647 takes precedence
• CPC Class Codes: H05K 3/4658 characterized by laminating a prefabricated metal foil pattern, e.g. by transfer
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing
• CPC Class Codes: Y10T 29/49126 Assembling bases
• 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 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 428/24917 including metal layer

Abstract

A circuit board is configured so as to include not less than two wiring layers, an insulator layer for electric insulation between the wiring layers, and an inner-via-hole conductive member provided in the insulator layer in a thickness direction of the insulator layer, for electric connection between the wiring layers. The insulator layer is made of a composite material containing an organic resin and a material having a smaller thermal expansion coefficient than that of the organic resin, and includes a surface part, a core part, and a surface part laminated in the stated order, the surface part having a high content of the organic resin, the core part having a low content of the organic resin. The wiring layers have a land portion that is connected with the inner-via-hole conductive member, the land portion being embedded so as to be substantially in contact with the core part, and the inner-via-hole conductive member has a thickness substantially equal to a thickness of the core part. According to this configuration, a part of the metal foil is embedded in the insulator layer so as to be in contact with the core layer. Therefore, this makes it possible to provide a circuit board in which portions of the conductive material can be selectively compressed, and which hence is capable of ensuring stable connection between layers.

Claims

1. A circuit board, comprising:

not less than two wiring layers;

an insulator layer for electric insulation between the wiring layers; and

an inner-via-hole conductive member provided in the insulator layer in a thickness direction of the insulator layer for electric connection between the wiring layers,

wherein;

the insulator layer is made of a composite material containing an organic resin and a material having a smaller thermal expansion coefficient than that of the organic resin, and includes a surface part, a core part, and a surface part laminated in the stated order, the surface part having a high content of the organic resin, the core part having a low content of the organic resin;

the wiring layers have a land portion that is connected with the inner-via-hole conductive member, the land portion being embedded so as to be substantially in contact with the core part; and

the inner-via-hole conductive member has a thickness substantially equal to a thickness of the core part.

2. The circuit board according to claim 1, wherein the land portion is embedded to a depth in a range of 2 μ

m to 50 μ

m.

3. The circuit board according to claim 1, wherein the land portion protrudes from the surface part.

4. The circuit board according to claim 3, wherein a height of protrusion of the land portion is in a range of 2 μ

m to 50 μ

m.

5. The circuit board according to claim 1, wherein the core part includes at least one selected from a fabric of an inorganic fiber, a nonwoven fabric of an inorganic fiber, and a synthetic resin film.

6. The circuit board according to claim 5, wherein the core part includes the inorganic fiber, and the inorganic fiber is glass.

7. The circuit board according to claim 5, wherein the synthetic resin film is a film made of at least one selected from the group consisting of polyimide, benzocyclobutene (BCB), polytetrafluoroethylene (PTFE), aramid, polyparaphenylene benzobisoxazole (PBO), and all aromatic polyesters.

8. The circuit board according to claim 5, wherein the core part further contains an inorganic filler.

9. The circuit board according to claim 8, wherein the inorganic filler is at least one filler selected from the group consisting of aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.

10. The circuit board according to claim 5, wherein the core part includes the synthetic resin fiber, and the synthetic resin film is made of a porous material.

11. The circuit board according to claim 10, wherein the porous material is impregnated with a composition of an inorganic filler and an organic resin.

12. The circuit board according to claim 11, wherein the porous material is made of a fluororesin, and the inorganic filler is at least one filler selected from the group consisting of aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.

13. The circuit board according to claim 1, wherein the organic resin is at least one resin selected from the group consisting of epoxy resins, polyimide resins, cyanate ester resins, phenol resol resins, all aromatic polyester resins, polyphenylene ether (PPE) resins, bismaleimide triazine resins, and fluororesins.

14. The circuit board according to claim 13, wherein the organic resin further is impregnated with at least one filler selected from the group consisting of aluminum hydroxide, aluminum oxide (alumina), silicon dioxide (silica), and silicon nitride.

15. The circuit board according to claim 1, wherein the inner-via-hole conductive member is made of a composition of a conductive filler and an organic resin.

16. The circuit board according to claim 15, wherein the conductive filler is made of at least one selected from the group consisting of gold, silver, copper, nickel, palladium, lead, tin, indium, and bismuth, alloys of these, and mixtures of these.

17. The circuit board according to claim 15, wherein a through hole filled with the inner-via-hole conductive member has a cross section in a tapered shape, and the inner-via-hole conductive member is put into the through hole from a wider opening of the through hole.

18. A circuit board producing method, the circuit board including not less than two wiring layers, an insulator layer for electric insulation between the wiring layers, and an inner-via-hole conductive member provided in the insulator layer in a thickness direction of the insulator layer for electric connection between the wiring layers,

the circuit board producing method comprising the steps of:

making an insulator layer of a composite material containing an organic resin and a material having a smaller thermal expansion coefficient than that of the organic resin so that the insulator layer includes a surface part, a core part, and a surface part laminated in the stated order, the surface part having a high content of the organic resin, the core part having a low content of the organic resin;

opening an inner via hole in the insulator layer in a thickness direction of the insulator layer, and filling the inner via hole with a conductive material;

providing metal foils on both sides of the insulator layer, each metal foil having a protruded portion at a predetermined position so that the position coincides with a position of the inner via hole filled with the conductive material;

applying heat and pressure to external sides of the metal foils by hot pressing so that the protruded portions of the metal foils come substantially in contact with the core part of the insulator layer, to cause the inner via hole filled with the conductive material to form an inner-via-hole conductive member with a thickness substantially equal to a thickness of the core part; and

etching the metal foils so as to leave the protruded portion as the land portion.

19. The circuit board producing method according to claim 18, wherein the land portion of the metal foil is formed by pattern formation by etching.

20. The circuit board producing method according to claim 18, wherein the metal foils are copper foils, and a rust prevention treatment selected from a blackening treatment and a chromate treatment is applied to recessed portions of the metal foils that have been recessed by etching to a predetermined thickness for forming a predetermined pattern.

21. The circuit board producing method according to claim 18, wherein a roughening treatment is applied to recessed portions of the metal foils that have been recessed by etching to a predetermined thickness for forming a predetermined pattern.

22. The circuit board producing method according to claim 18, wherein the inner via hole has a cross section in a tapered shape, and the conductive material is filled into the inner via hole from a wider opening thereof.

23. The circuit board producing method according to claim 18, wherein the conductive material is a conductive paste.

24. A circuit board producing method, the circuit board including not less than two wiring layers, an insulator layer for electric insulation between the wiring layers, and an inner-via-hole conductive member provided in the insulator layer in a thickness direction of the insulator layer for electric connection between the wiring layers,

the circuit board producing method comprising the steps of:

making an insulator layer of a composite material containing an organic resin and a material having a smaller thermal expansion coefficient than that of the organic resin so that the insulator layer includes a surface part, a core part, and a surface part laminated in the stated order, the surface part having a high content of the organic resin, the core part having a low content of the organic resin;

opening an inner via hole in the insulator layer in a thickness direction of the insulator layer, and filling the inner via hole with a conductive material;

providing transfer bases on both sides of the insulator layer, each of the transfer bases having a metal foil patterned in a predetermined pattern so as to coincide with a position of the inner via hole filled with the conductive material; and

applying heat and pressure to external sides of the transfer bases by hot pressing so that the metal foils come substantially in contact with the core part of the insulator layer, to cause the inner via hole filled with the conductive material to form an inner-via-hole conductive member with a thickness substantially equal to a thickness of the core part.

25. The circuit board producing method according to claim 24, wherein the inner via hole has a cross section in a tapered shape, and the conductive material is filled therein from a wider opening thereof.

26. The circuit board producing method according to claim 24, wherein the conductive material is a conductive paste.