US20010015008A1 - Process for fabricating a thin multi-layer circuit board - Google Patents
Process for fabricating a thin multi-layer circuit board Download PDFInfo
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- US20010015008A1 US20010015008A1 US09/726,328 US72632800A US2001015008A1 US 20010015008 A1 US20010015008 A1 US 20010015008A1 US 72632800 A US72632800 A US 72632800A US 2001015008 A1 US2001015008 A1 US 2001015008A1
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/46—Manufacturing multilayer circuits
- H05K3/4644—Manufacturing multilayer circuits by building the multilayer layer by layer, i.e. build-up multilayer circuits
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0286—Programmable, customizable or modifiable circuits
- H05K1/0293—Individual printed conductors which are adapted for modification, e.g. fusable or breakable conductors, printed switches
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/22—Secondary treatment of printed circuits
- H05K3/24—Reinforcing the conductive pattern
- H05K3/243—Reinforcing the conductive pattern characterised by selective plating, e.g. for finish plating of pads
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/09—Shape and layout
- H05K2201/09209—Shape and layout details of conductors
- H05K2201/09654—Shape and layout details of conductors covering at least two types of conductors provided for in H05K2201/09218 - H05K2201/095
- H05K2201/09736—Varying thickness of a single conductor; Conductors in the same plane having different thicknesses
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/10—Using electric, magnetic and electromagnetic fields; Using laser light
- H05K2203/107—Using laser light
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/17—Post-manufacturing processes
- H05K2203/175—Configurations of connections suitable for easy deletion, e.g. modifiable circuits or temporary conductors for electroplating; Processes for deleting connections
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
- H05K3/027—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed by irradiation, e.g. by photons, alpha or beta particles
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
- H05K3/04—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed mechanically, e.g. by punching
- H05K3/046—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed mechanically, e.g. by punching by selective transfer or selective detachment of a conductive layer
- H05K3/048—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed mechanically, e.g. by punching by selective transfer or selective detachment of a conductive layer using a lift-off resist pattern or a release layer pattern
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
- H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
- H05K3/061—Etching masks
- H05K3/064—Photoresists
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/108—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern by semi-additive methods; masks therefor
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/22—Secondary treatment of printed circuits
- H05K3/28—Applying non-metallic protective coatings
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/38—Improvement of the adhesion between the insulating substrate and the metal
- H05K3/388—Improvement of the adhesion between the insulating substrate and the metal by the use of a metallic or inorganic thin film adhesion layer
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/4902—Electromagnet, transformer or inductor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/49126—Assembling bases
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/4913—Assembling to base an electrical component, e.g., capacitor, etc.
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/4913—Assembling to base an electrical component, e.g., capacitor, etc.
- Y10T29/49144—Assembling to base an electrical component, e.g., capacitor, etc. by metal fusion
Definitions
- the present invention relates to a process for fabricating a thin multi-layer circuit board on which can be mounted many electronic parts such as integrated circuits (ICs) and large size integulated circuits (LSIs).
- ICs integrated circuits
- LSIs large size integulated circuits
- a thin multi-layer circuit board which is obtained by forming an insulating layer on a plate-like substrate made of a suitable insulating material and interposing at least two wiring pattern layers in this insulating layer.
- the two wiring pattern layers are connected to each other at a suitable place through a via and the two wiring pattern layers constitute a predetermined circuit pattern.
- electronic part-mounting pads to which can be connected the leads of electronic parts, the electronic part-mounting pads being connected through vias to the wiring pattern layers in the insulating layer.
- An object of the present invention is to provide a thin multi-layer circuit board which is so constituted that, when a remodeling pad is being used, this remodeling pad can be easily cut, and a process for fabricating the same.
- Another object of the present invention is to provide a process for fabricating a thin multi-layer circuit board, which does not require a process for etching gold plating at the time of forming a pad by plating gold on the thin multi-layer circuit board.
- a further object of the present invention is to provide a process for fabricating a thin multi-layer circuit board which is capable of forming a thin chromium film on the wiring pattern layers without relying upon the lift-off method when a number of wiring pattern layers are stacked on an insulating plate-like substrate.
- a still further object of the present invention is to provide a process for fabricating a thin multi-layer circuit board which is capable of removing a defective wiring pattern layer without damaging the wiring pattern layers on the lower side when a number of wiring patterns are stacked on an insulating plate-like substrate.
- a yet further object of the present invention is to provide a method of pre-baking a photosensitive polyimide resin layer that is applied in the fabrication of a multi-layer circuit board, the pre-baking method making it possible not only to uniformly heat the insulating plate-like substrate from the back side thereof but also to carry out the operation with excellent efficiency, as well as to provide a heat-accumulating block used for the method of pre-baking.
- a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern using said wiring pattern layers, wherein a barrier metal exclusion zone is prepared by forming a metallic barrier layer on said wiring pattern layer in an electronic part-mounting region, a remodeling pad layer is formed on said metallic barrier layer neighboring said barrier metal exclusion zone, and an electronic part-mounting pad layer is formed neighboring said remodeling pad layer.
- a thin multi-layer circuit board which is obtained by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier layer is formed on the wiring pattern layer in an electronic part-mounting region, a barrier metal exclusion zone is included in said metallic barrier layer, and a remodeling pad layer and an electronic part-mounting pad layer are formed on said metallic barrier layer, said remodeling pad layer being arranged neighboring said barrier metal exclusion zone and said electronic part-mounting pad layer being arranged neighboring said remodeling pad layer.
- the barrier metal exclusion zone is prepared neighboring the remodeling pad layer.
- the wiring pattern layer is cut by a YAG laser along the barrier metal exclusion zone in order to cut the electrical connection between the remodeling pad and the wiring pattern layer. Therefore, destruction of the insulating layer in the thin multi-layer circuit board is minimized.
- the barrier metal is formed maintaining a sufficient thickness making it possible to prevent the barrier metal from being corroded at the time of soldering lead wires onto the electronic part-mounting pad and onto the remodeling pad.
- a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier layer is formed on the wiring pattern layer in an electronic part-mounting region, a pad-forming resist is formed in said metallic barrier layer, a gold pad layer of a predetermined shape is formed on said metallic barrier layer by using said pad-forming resist, and said pad-forming resist is removed.
- a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a pad-forming resist is formed on the wiring pattern layer in an electronic part-mounting region, a metallic barrier layer is formed on the wiring pattern layer, a gold pad layer of a predetermined shape is formed on the metallic barrier layer using the pad-forming resist, and said pad-forming resist is removed.
- the gold pad layer is formed into a predetermined shape by using the pad-forming resist without the need of using a highly toxic gold-etching solution, contributing to the safely of the operation.
- a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein the wiring pattern layers are formed on the insulating layers by sequentially forming a first thin chromium film, a copper layer and a second thin chromium film on said insulating layers followed by etching.
- the wiring pattern layers on the insulating layers are formed by sequentially forming the first thin chromium film, the copper layer and the second thin chromium film on the insulating layers followed by etching. Therefore, there is no need of employing a lift-off method for forming the second thin chromium film on the insulating layers.
- a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier film covers the wiring pattern layer every time a wiring pattern layer is formed.
- the metallic barrier film can be formed by either the lift-off method or an etching method.
- the metallic barrier film covers the wiring pattern layer every time a wiring pattern layer is formed. Therefore, a defective wiring pattern layer can be removed by wet-etching, and the etching solution is prevented from infiltrating into the wiring pattern layers of the lower side. It is therefore possible to form the wiring pattern again after a defective wiring pattern layer is removed, contributing greatly to decreasing the cost of producing the thin multi-layer circuit board.
- the heat-accumulating block is constituted by a block member having a flat heating surface, a pair of guide walls that extend in parallel along the opposing side edges of the heating surface of the block member, and rail elements that extend along the corners formed by the pair of guide walls and the heating surface, and the pair of guide walls have a lateral width which is slightly larger than a distance between the opposing side edges on one side of the insulating plate-like substrate.
- the heat-accumulating block is disposed in an atmosphere heated at a predetermined temperature, the insulating plate-like substrate is placed over the heat-accumulating block close thereto and is heated. Therefore, the insulating plate-like substrate can be uniformly heated from the back side thereof without being stuck to the heat-accumulating block.
- the insulating plate-like substrate is placed on the rail elements from the ends on one side of the pair of guide walls and is moved over the flat surface of the heat-accumulating block and is pulled out by being placed on the rail elements. Therefore, even when a plurality of such heat-accumulating blocks are arranged to be stacked in an oven, the insulating plate-like substrates can be easily put into, and pulled out of, the heat-accumulating blocks.
- FIGS. 1 to 16 are diagrams schematically illustrating the steps in a process for fabricating thin multi-layer circuit boards according to a first aspect of the present invention
- FIGS. 17 to 26 are diagrams schematically illustrating the steps in a process for fabricating thin multi-layer circuit boards according to a second aspect of the present invention.
- FIGS. 27 to 35 are diagrams schematically illustrating the steps in a process for fabricating thin multi-layer circuit boards according to a third aspect of the present invention.
- FIG. 36 is a diagram schematically illustrating a step in a process for fabricating thin multi-layer circuit boards according to a fourth aspect of the present invention.
- FIGS. 37 to 39 are diagrams schematically illustrating the steps in a process for applying a metallic barrier film onto a wiring pattern layer in the thin multi-layer circuit substrate shown in FIG. 36;
- FIGS. 40 to 42 are diagrams schematically illustrating the steps in another process for applying a metallic barrier film onto a wiring pattern layer in the thin multi-layer circuit substrate shown in FIG. 36;
- FIG. 43 is a diagram which schematically illustrates the principle of a pre-baking method according to a fifth aspect of the present invention.
- FIG. 44 is a graph showing the distribution of temperature rise of when a ceramic substrate is heated by the pre-baking method shown in FIG. 43;
- FIG. 45 is a graph showing the distribution of temperature rise of when a ceramic substrate is heated by a pre-baking method which is different from the pre-baking method shown in FIG. 43;
- FIG. 46 is a perspective view of a heat-accumulating block that is suited for putting into practice the pre-baking method according to the fifth aspect of the present invention.
- FIG. 47 is a diagram illustrating an end surface of the heat-accumulating block
- FIG. 48 is a graph showing the distribution of temperature rise of when a ceramic substrate is heated by using the heat-accumulating blocks of FIGS. 46 and 47;
- FIGS. 49 to 72 are diagrams schematically illustrating the steps in a conventional representative process for fabricating thin multi-layer circuit boards.
- a thin chromium film 12 is formed on, for example, a ceramic substrate 10 , and a thin copper film 14 is formed on the thin chromium film 12 .
- the thin chromium film 12 and the thin copper film 14 are usually formed by sputtering.
- a copper-plating resist 16 is formed on the thin copper film 14 as shown in FIG. 50.
- a copper-plated layer 18 is formed on the first wiring pattern as shown in FIG. 51.
- the copper-plating resist 16 is removed as shown in FIG.
- a thin chromium film 20 is formed again on the thin copper film 14 and on the copper-plated layer 18 as shown in FIG. 53.
- an etching resist 22 is formed on the first wiring pattern. Then, by effecting the etching, the thin copper film 14 and the thin chromium film 12 are removed from the regions other than the first wiring pattern as shown in FIG. 55. Thereafter, the etching resist 22 is removed to obtain a first wiring pattern layer 24 on the ceramic substrate 10 as shown in FIG. 56.
- the thin chromium film 12 has a thickness of, for example, about 0.08 ⁇
- the thin chromium film 22 has a thickness of, for example, about 0.15 ⁇
- copper layers ( 12 , 18 ) sandwiched between these thin chromium films have a thickness of, for example, about 5 ⁇ .
- an insulating layer such as a photosensitive polyimide resin layer 26 is applied thereon and is pre-baked as shown in FIG. 57. Then, the insulating layer 26 is developed by exposure to light through a predetermined pattern, and whereby a via hole 28 is formed at a predetermined portion of the insulating layer 26 as shown in FIG. 58.
- a thin chromium film 30 and a thin copper film 32 are formed thereon by sputtering as shown in FIG. 59.
- a plating resist 34 is formed on the thin copper film 32 as shown in FIG. 60. By plating copper on the plating resist 34 , a copper-plated layer 36 is formed on the second wiring pattern as shown in FIG. 61.
- the thin chromium film 30 has a thickness of, for example, about 0.08 ⁇
- the copper layers ( 32 , 36 ) on the thin chromium film 30 have a thickness of, for example, about 4 ⁇
- the nickel-plated layer 38 has a thickness of, for example, about 3 ⁇
- the gold-plated layer 40 has a thickness of, for example, about 0.6 ⁇ .
- a gold-etching resist 46 is formed in a predetermined pattern on the electronic part-mounting region, i.e., on the gold-plated layer 40 as shown in FIG. 66, and then gold is removed by etching. As shown in FIG. 67, therefore, the gold-plated layer 40 is partly removed and the nickel-plated layer 38 is exposed. Thereafter, the gold-etching resist 46 is removed as shown in FIG. 68, and, then, a chromium lift-off resist 48 is formed on the insulating layer 26 in order to form a thin chromium film on the second wiring pattern layer 44 . In this case, the chromium lift-off resist 48 is applied onto the gold-plated layer 40 , too, as shown in FIG. 69.
- a thin chromium film 50 is formed on the second wiring pattern layer 44 and on the chromium lift-off resist 48 as shown in FIG. 70.
- the chromium lift-off resist 48 is then removed as shown in FIG. 71, and the thin chromium film 50 is left on the second wiring pattern layer 44 only.
- an overcoat insulating layer 52 composed of a polyimide resin is applied onto the insulating layer 26 and onto the second wiring pattern layer 44 , and the surface of the gold-plated layer 40 is exposed to obtain a thin multi-layer circuit board.
- the gold-plated layer 40 is divided into three exposed pads 40 a , 40 b and 40 c .
- the pad 40 a serves as a part-mounting pad for soldering the lead wires when an electronic part is mounted.
- the pad 40 b serves as a remodeling pad that is used for remodeling or repairing the circuit wiring, and is used for soldering the lead wires as required for remodeling or repairing the circuit wiring.
- the pad 40 c is used for only electrically connecting the part-mounting pad 40 a and the remodeling pad 40 b to the wiring pattern layers 24 and 44 . Depending upon the cases, the pad 40 c may be covered with the overcoat insulating layer 52 .
- the nickel-plated layer 38 works as a metallic barrier layer for protecting the copper layers ( 32 , 36 ) when a lead wire is soldered onto the part-mounting pad 40 a and/or the remodeling pad. If described in detail, when there is no nickel-plated layer 38 , the solder material permeates into the copper layers ( 32 , 36 ) at the time of soldering, causing the electric properties and mechanical properties to change. In order to prevent the solder material from permeating into the copper layers ( 32 , 36 ), therefore, the nickel-plated layer 38 is necessary.
- the nickel-plated layer 38 must have a thickness of at least 3 ⁇ so that it works as a metallic barrier layer to a sufficient degree. When the thickness is smaller than 3 ⁇ , the nickel-plated layer 38 corrodes at the time of soldering, causing a problem in that the solder material permeates into the copper layers ( 32 , 36 ).
- the presence of a metallic barrier layer i.e., the nickel-plated layer 38 , becomes a problem at the time of remodeling or repairing the circuit wiring. That is, to remodel or repair the circuit wiring, the electrical connection between the remodeling pad 40 b and the wiring pattern layers 24 , 44 must be cut off. This is done by cutting the conductor layer between the remodeling pad 40 b and the pad 40 c by using a YAG laser beam.
- the nickel-plated layer 38 can be cut by increasing the output of the YAG laser beam but this causes the insulating layer 26 to be damaged to a large extent. It is not, therefore, possible to increase the output of the YAG laser beam.
- the thickness of the nickel-plated layer 38 can be decreased so that it can be easily cut by the YAG laser beam but this is accompanied by the problem of corrosion at the time of soldering.
- the conventional process for producing thin multi-layer circuit boards involves the processing for etching the gold-plated layer 40 (FIGS. 66 and 67). That is, the processing for etching the gold-plated layer 40 requires a strongly toxic solvent, and it is desirable to exclude such an etching processing from the steps of producing thin multi-layer circuit boards.
- the conventional process for producing thin multi-layer circuit boards employs a lift-off method for forming the thin chromium film 50 on the second wiring pattern layer 44 (FIGS. 69, 70, 71 ), which is another problem. That is, after the thin chromium film 50 is formed, it is not easy to remove the lift-off resist 48 and a relatively long period of time is required for the removal step.
- a further problem in the conventional process for producing thin multi-layer circuit boards resides in the pre-baking of the photosensitive polyimide resin.
- the photosensitive polyimide resin is used not only as an insulating material but also as a photoresist material at the time of forming a metal-plated layer.
- the polyimide resin is pre-baked when it is applied in the process for producing thin multi-layer circuit boards.
- pre-baking means vaporizing the solvent by leaving the polyimide resin in an atmosphere heated to a temperature of about 80°. In this case, it is desirable to uniformly heat the ceramic substrate from the back side thereof.
- via holes and the like are formed with a high resolution in the polyimide resin layer by exposure to light and development.
- a heat-accumulating block made of a material having excellent heat-accumulating property was placed in an oven and a ceramic substrate was placed on the heat-accumulating block in order to uniformly heat the ceramic substrate from the back side thereof. This resulted in failure because, though the ceramic substrate is uniformly heated, the polyimide resin that reached the back surface of the ceramic substrate when the polyimide resin was applied causes the ceramic substrate to stick onto the heat-accumulating block to hinder the workability to a great extent.
- FIGS. 1 to 17 of the accompanying drawings An embodiment of a process for fabricating thin multi-layer circuit boards according to a first aspect of the present invention will now be described with reference to FIGS. 1 to 17 of the accompanying drawings.
- the initial steps in the fabrication process according to the first aspect of the present invention are substantially the same as those of the conventional fabrication process described earlier, and are not mentioned again.
- FIG. 1 illustrates a state where a first wiring pattern layer 24 is formed on a ceramic substrate 10 , an insulating layer such as a photosensitive polyimide resin layer 26 is applied onto the first wiring pattern layer 24 and after pre-baked a via hole 28 is formed and, then, after the insulating layer 26 is cured, a thin chromium film 30 and a thin copper film 32 are formed by, for example, sputtering.
- a copper-plating resist 54 for forming a second wiring pattern as shown in FIG. 1.
- a copper-plated layer 56 is formed on the second wiring pattern as shown in FIG. 2 and, thereafter, the copper-plating resist 54 is removed as shown in FIG. 3.
- the diagramed region is an electronic part-mounting region.
- nickel and gold are further plated on the copper-plated layer 56 .
- a plating resist 58 is formed as shown in FIG. 4.
- a plating resist 58 a is formed on the copper-plated layer 56 to prepare a nickel exclusion zone on a portion thereof.
- nickel is plated to form a nickel-plated layer 60 as shown in FIG. 5 and, then, gold is plated on the nickel-plated layer 60 to form a gold-plated layer 62 .
- the plating resist is removed as shown in FIG. 6. In this case, a zone on a part of the surface of the copper-plated layer 56 , i.e., the zone to where the plating resist 58 a is applied turns into a nickel exclusion zone.
- an etching resist 64 is formed on the second wiring pattern as shown in FIG. 7.
- the thin copper film 32 and the thin chromium film 30 are removed from the regions other than the second wiring pattern as shown in FIG. 8.
- the etching resist 64 is removed to obtain a second wiring pattern layer 66 on the insulating layer 26 as shown in FIG. 9.
- the first wiring pattern layer 24 and the second wiring pattern layer 66 are electrically connected together by conducting metals in the via hole, and whereby a predetermined circuit pattern is constituted by these two wiring pattern layers 24 and 66 .
- a gold-etching resist 68 in a predetermined pattern as shown in FIG. 10 and, then, gold is etched.
- the gold-plated layer 62 is partly removed as shown in FIG. 11, and is divided into three pad layers.
- the gold-etching resist 68 is removed as shown in FIG. 12, the three gold-plated layers, which are the pad layers, serve as an electronic part-mounting pad 62 a , as a remodeling pad 62 b and as a connection pad 62 c .
- a chromium lift-off resist 70 is formed on the insulating layer 26 as shown in FIG.
- the chromium lift-off resist 70 is also formed on the electronic part-mounting pad 62 a and on the remodeling pad 62 b .
- a thin chromium film 72 is formed on the second wiring pattern layer 66 and on the chromium lift-off resist 70 as shown in FIG. 14.
- the chromium liftoff resist 70 is removed as shown in FIG. 15, and the thin chromium film 72 is left on the second wiring pattern layer 66 only. Then, as shown in FIG.
- an overcoat insulating layer 74 composed of a polyimide resin is applied onto the insulating layer 26 and onto the second wiring pattern layer 66 while exposing the electronic part-mounting pad 62 a and the remodeling pad 62 b through the overcoat insulating layer 74 .
- the remodeling pad 62 b When the remodeling pad 62 b is used for remodeling or repairing the circuit wiring in the thus fabricated thin multi-layer circuit board, the electric connection between the remodeling pad 62 b and the second wiring pattern layer can be easily cut off by a low output YAG laser or a similar laser. This is because, the nickel exclusion zone denoted by reference numeral 76 is used as a portion to be cut.
- the nickel-plated layer 60 can be formed maintaining a thickness of not smaller than 3 ⁇ and, preferably, maintaining a thickness of about 3.5 ⁇ , contributing to the corrosion resistance of the nickel-plated layer 60 when soldering lead wires to the electronic part-mounting pad 62 a and to the remodeling pad 62 b occurs.
- FIGS. 17 to 27 illustrate an embodiment of the process for fabricating thin multi-layer circuit boards according to a second aspect of the present invention.
- the initial steps in this fabrication process are substantially the same as those of the fabrication process according to the first aspect of the present invention. That is, a first wiring pattern layer 24 is formed on a ceramic substrate 10 , a photosensitive polyimide resin layer 26 is applied onto the first wiring patten layer 24 and after pre-baked a via hole 28 is formed, and, then, after the insulating layer 26 is cured, a thin chromium film 30 and a thin copper film 32 are formed by, for example, sputtering, and a copper-plating layer 56 is formed on the thin copper film 32 in order to form a second wiring pattern, which is the same as the fabrication process according to the first aspect of the present invention.
- nickel and gold are further plated on the copper-plated layer 56 in the electronic part-mounting region.
- a plating resist 78 is formed around the electronic part-mounting region as shown in FIG. 17, and on the inside thereof are formed plating resists 78 a and 78 b on the copper-plated layer 56 .
- nickel is plated to form a nickel-plated layer 80 as shown in FIG. 18 and, then, gold is plated on the nickel-plated layer 80 to form a gold-plated layer 82 . Thereafter, the plating resist is removed as shown in FIG. 20.
- an etching resist 84 is formed on the second wiring pattern and, then, etching is effected thereto remove the thin copper film 32 and the thin chromium film 30 from the regions other than the second wiring pattern as shown in FIG. 21. Then, the etching resist 84 is removed to obtain a second wiring pattern layer 86 on the insulating layer 26 as shown in FIG. 22.
- the nickel-plated layer 80 and the gold-plated layer 82 have, respectively, been divided into three by the plating resists 78 a and 78 b at the time of plating, and the divided gold-plated layer serves as the electronic part-mounting pad 82 a , as the remodeling pad 82 b and as the connection pad 82 c , eliminating the need of etching the gold-plated layer 80 .
- a chromium lift-off resist 88 is formed on the insulating layer 26 , as shown in FIG. 23 to form a thin chromium layer on the second wiring pattern layer 86 and, at this time, the chromium lift-off resist 88 is also formed on the electronic part-mounting pad 82 a and on the remodeling pad 82 b .
- a thin chromium film 90 is formed on the second wiring pattern layer 86 and on the chromium lift-off resist 88 as shown in FIG. 24. Then, as the chromium lift-off resist 88 is removed as shown in FIG.
- the thin chromium film 90 is left on the second wiring pattern layer 86 only. Thereafter as shown in FIG. 24, an overcoat insulating layer 92 composed of a polyimide resin is applied onto the insulating layer 26 and onto the second wiring pattern layer 86 while the electronic part-mounting pad 82 a and the remodeling pad 82 b are exposed through the overcoat insulating layer 92 .
- the aforementioned fabrication process has a feature in that there is no need to effect the etching for the gold-plated layer 82 and, hence, the use of a highly toxic etching solution can be avoided.
- the remodeling pad 82 b is disposed neighboring the nickel exclusion region and, hence, the electrical connection between the remodeling pad 62 b and the second wiring pattern layer 86 can be easily cut by a low output YAG laser or the like at the time of remodeling or repairing the circuit wiring as in first aspect of the present invention.
- the nickel-plated layer 80 may be extended without being divided. In this case, after the nickel-plated layer is formed in an extending manner, plating resists ( 78 a , 78 b ) as shown in FIG. 17 are formed on the nickel-plated layer in the electronic part-mounting region.
- FIGS. 27 to 36 illustrate an embodiment of the process for fabricating thin multi-layer circuit boards according to a third aspect of the present invention.
- the initial steps in this fabrication process are substantially the same as those of the fabrication process according to the first aspect of the present invention. That is, a first wiring pattern layer 24 is formed on a ceramic substrate 10 , a photosensitive polyimide resin layer 26 is applied onto the first wiring pattern layer 24 and is pre-baked to form a via hole 28 , and, then, after the insulating layer 26 is cured, a thin chromium film 30 and a thin copper film 32 are formed by, for example, sputtering, and a copper-plating layer 56 is formed on the thin copper film 32 in order to form a second wiring pattern, which are the same as in the fabrication process according to the first aspect of the present invention.
- a thin chromium film 94 is formed by, for example, sputtering on the thin copper film 32 and on the copper-plated layer 56 .
- a resist 96 is formed around the electronic part-mounting region as shown in FIG. 28 and, besides, resists 96 a and 96 b are formed on the thin chromium film 94 on the inside of the electronic part-mounting region.
- the etching is effected to remove the thin chromium film 94 from the electronic part-mounting region as shown in FIG. 29.
- a nickel-plated layer 98 is formed as shown in FIG. 30.
- a gold-plated layer 100 is formed by plating gold on the nickel-plated layer 98 and, then, plating resists 96 , 96 a and 96 b are removed as shown in FIG. 31.
- an etching resist 102 is formed on the second wiring pattern as shown in FIG. 32.
- the thin chromium film 94 , the thin copper film 32 and the thin chromium film 30 are removed from the regions other than the second wiring pattern as shown in FIG. 33.
- the etching resist 102 is removed to obtain a second wiring pattern layer 104 on the insulating layer 26 as shown in FIG. 34.
- FIG. 34 As the case of the embodiment (FIGS.
- the nickel-plated layer 98 and the gold-plated layer 100 are, respectively, divided into three by the plating resists 96 a and 96 b at the time of plating, and the divided gold-plated layers serve as an electronic part-mounting pad 100 a , as a remodeling pad 100 b and as a connection pad 100 c , eliminating the need of effecting the etching for the gold-plated layer 100 . Then, as shown in FIG.
- an overcoat insulating layer 106 composed of a polyimide resin is applied onto the insulating layer 26 and onto the second wiring pattern layer 104 while exposing the electronic part-mounting pad 100 a and the remodeling pad 100 b through the overcoat insulating layer 92 .
- the aforementioned fabrication process has a novel feature in that the thin chromium film 94 is formed on the second wiring pattern layer 104 formed on the insulating layer 26 without relying upon the lift-off method.
- This embodiment has not only the feature according to the first aspect of the present invention in that the electrical connection between the remodeling pad 100 b and the second wiring pattern layer 104 is easily cut by a low output YAG laser or the like at the time of remodeling or repairing the circuit wiring but also the feature, according to the second aspect of the present invention, that there is no need to etch the gold-plated layer 100 .
- the feature according to the third aspect of the present invention i.e., forming the thin chromium film on the insulating layer without relying upon the lift-off method, by itself constitutes an invention.
- FIG. 36 illustrates, in the form of an intermediate product, a thin multi-layer circuit board fabricated by the process for fabrication according to a fourth aspect of the present invention.
- This intermediate product is in a stage in which wiring pattern layers and polyimide resin layers are alternately stacked on a ceramic substrate 108 . That is, on the ceramic substrate 108 is formed a first wiring pattern layer 110 which is covered with a first polyimide resin insulating layer 112 . On the first polyimide resin insulating layer 112 is formed a second wiring pattern layer 114 which is covered with a second polyimide resin insulating layer 116 .
- the first to third wiring pattern layers 110 , 114 and 118 are connected together through vias formed in the polyimide resin insulating layers 112 , 116 and 120 , thereby to constitute a predetermined circuit pattern.
- the wiring patterns 110 , 114 and 118 respectively, include thin chromium films 110 a ; 110 b , 114 a ; 114 b , 116 a ; 116 b , as well as copper layers 110 c , 114 c and 118 c formed among the thin chromium films.
- the wiring pattern layers 110 , 114 , 118 and the polyimide resin insulating layers 112 , 116 , 118 can be formed through a variety of processes mentioned already.
- the thin chromium films 110 b , 114 b and 118 b are covered with a metallic barrier film 122 every time the wiring pattern layers 110 , 114 and 118 are formed, the metallic barrier film 122 being comprised of, for example, titanium nitride, platinum or the like.
- the metallic barrier film 122 can be incorporated at the time of forming the wiring pattern layers 110 , 114 and 118 relying, for example, upon the etching as shown in FIGS. 37 to 39 . Referring to FIG. 37, a first thin chromium film 110 a is, first, formed by sputtering on the ceramic substrate 108 and, then, copper is sputtered thereon.
- a copper layer 110 c is formed by plating copper on a region that corresponds to the first wiring pattern, then, a second thin chromium film 110 b is formed by sputtering and a metallic barrier film 122 is formed thereon by sputtering.
- an etching resist 124 is formed on a predetermined region and the etching is effected to obtain a first wiring pattern layer 110 as shown in FIG. 39.
- the metallic barrier film 122 of titanium nitride or platinum is very stable against an etching solution for chromium or copper.
- the etching solution will comprise concentrated hydrofluoric acid, concentrated nitric acid and water.
- the metallic barrier film 122 is composed of platinum, the etching solution will be aqua regia or a diluted aqua regia solution.
- the metallic barrier film can also be formed by the lift-off method. That is, a first thin chromium film 110 a is formed by sputtering on the ceramic substrate 108 and, then, copper is sputtered thereon. Next, a copper layer 110 c is formed by plating copper on a region corresponding to the first wiring pattern, and the first thin chromium film 110 a and the copper layer 110 c are formed into a predetermined wiring pattern by etching. Then, a lift-off resist 126 is formed thereon as shown in FIG. 40. Referring next to FIG. 42, a thin chromium film 110 b and a metallic barrier film 122 are formed by sputtering. Then, the lift-off resist 126 is removed to obtain a first wiring pattern layer 110 on the ceramic substrate 120 .
- a defective wiring pattern layer that is formed in the step of alternately stacking the wiring pattern layers and the polyimide resin insulating layers, can be formed again.
- the third wiring pattern layer 118 is removed without at all damaging the second wiring pattern layer 116 .
- the metallic barrier film 122 of the third wiring pattern layer 118 is removed by using the above-mentioned etching solution and, then, the second thin chromium film 118 b , copper layer 118 c and first thin chromium film 118 a are removed by using a known etching solution.
- the second wiring pattern layer 114 has been covered with the metallic barrier film 122 , and the etching solution for chromium and copper does not permeate into the second wiring pattern layer 114 through the via. Accordingly, the third wiring pattern layer 118 that has been removed can be formed again.
- the metallic barrier film 122 covers the second thin chromium films 110 b , 114 b and 118 b of the wiring pattern layers 110 , 114 and 118 .
- the metallic barrier film 122 may be formed between the copper layers 110 c , 114 b , 118 b and the second thin chromium films 110 b , 114 b , 118 b .
- the second thin chromium films 110 b , 114 b and 118 b may be damaged at the time of removing the defecting wiring pattern layer, but the damage does not extend to the copper layers 110 c , 114 b and 118 b .
- the photosensitive polyimide resin is used not only as an insulating material but also as a resist material.
- the ceramic substrate is put into the oven and is pre-baked. It was mentioned already that in this case, the ceramic substrate is uniformly heated from the back side thereof.
- a fifth aspect of the present invention is directed to improving the pre-baking method.
- FIG. 43 illustrates the principle of the pre-baking method according to the fifth aspect of the present invention, wherein reference numeral 128 denotes a heat-accumulating block which is made of, for example, aluminum.
- the heat-accumulating block 128 is left to stand in an oven (not shown) having an atmospheric temperature of, for example, about 80°.
- the heat-accumulating block 128 has a flat upper surface, and a pair of copper strips 130 are disposed along the opposing side edges on the surface thereof.
- a ceramic substrate 132 coated with the polyimide resin is placed on the pair of copper strips 130 , and a gap of about 0.3 mm is maintained between the upper surface of the heat-accumulating block 128 and the ceramic substrate 132 .
- the ceramic substrate 132 is gradually heated from the back side thereof by receiving radiant heat. At this moment, the rise in the temperature is measured at five points at equal distances along the diagonal of the ceramic substrate 132 . The results are shown in a graph of FIG. 44 from which it will be obvious that the temperature rises are nearly the same at all of the above-mentioned five points.
- FIG. 45 illustrates similar temperature rises in the case when the ceramic substrate 132 is placed on the upper surface of the heat-accumulating block. It can be regarded that the temperature rise is substantially the same at five points maintaining an equal distance along the diagonal lines of the ceramic substrate 132 . That is, it is desired to place the ceramic substrate 132 directly on the upper surface of the heat-accumulating block in order to uniformly heat the ceramic substrate 132 . As mentioned earlier, however, it is not possible to place the ceramic substrate 132 directly on the heat-accumulating block 128 .
- FIGS. 46 and 47 illustrate a heat-accumulating block 134 adapted to putting the pre-baking method of the present invention into practice.
- the heat-accumulating block 134 comprises a block member 138 having a flat heating surface 136 , a pair of guide walls 140 that extend in parallel along the opposing sides of the heating surface 136 of the block member 138 , and rail elements 142 that extend along the corners formed by the guide walls 140 and the heating surface 136 .
- the lateral width of the pair of guide wall portions 140 is slightly broader than the distance between the opposing side edges of the insulating plate-like substrate.
- the ceramic substrate 132 is placed on the rail elements 142 from the ends on one side of the pair of guide walls 140 , and is pushed; i.e., the ceramic substrate 132 can be easily moved on the flat surface 136 of the heat-accumulating block 134 and can be easily pulled out along the rail elements 142 .
- the ceramic substrates can be easily put into, and taken out from, the heat-accumulating blocks 134 , enabling the pre-baking processing to be quickly executed.
- FIG. 48 is a graph showing the results of the measurement of the temperature rise distribution in the manner described above in the case when the ceramic substrate 132 is heated by being placed on the heat-accumulating block 134 . It will be obvious from this graph that the ceramic substrate 132 is heated substantially uniformly though the temperature rise distribution is slightly disturbed immediately after the start of the heating.
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Abstract
A process for fabricating thin multi-layer circuit boards which allow the electrical conduction of remodeling pads to be easily cut do not use etching for gold, avoid the lift-off method for forming a thin chromium film on the wiring pattern layer, allow a defective wiring pattern layer to be removed, and which uses uniform heating of the substrate, from the back side thereof, at the time of pre-baking. A barrier metal (60) is excluded from a portion where the electrical conduction of a remodeling pad (62 b) is to be cut (FIGS. 1 to 16). Alternatively, gold-plating resist is formed in order to avoid the etching for gold (FIGS. 17 to 19). Alternatively, a thin chromium film is formed in advance by etching on the wiring pattern layer (FIGS. 27 to 33). Alternatively, a metallic barrier film (122) is formed on each of the wiring pattern layers so that the wiring pattern layer can be removed without affecting other wiring pattern layers (FIGS. 36 to 42). Alternatively, the substrate is disposed over a heat-accumulating block (138) adjacent thereto so that it is uniformly heated from the back side thereof during the pre-baking.
Description
- 1. Field of the Invention
- The present invention relates to a process for fabricating a thin multi-layer circuit board on which can be mounted many electronic parts such as integrated circuits (ICs) and large size integulated circuits (LSIs).
- 2. Related Art
- There has been known a thin multi-layer circuit board which is obtained by forming an insulating layer on a plate-like substrate made of a suitable insulating material and interposing at least two wiring pattern layers in this insulating layer. The two wiring pattern layers are connected to each other at a suitable place through a via and the two wiring pattern layers constitute a predetermined circuit pattern. Moreover, on the surface of the thin multi-layer circuit board are provided electronic part-mounting pads to which can be connected the leads of electronic parts, the electronic part-mounting pads being connected through vias to the wiring pattern layers in the insulating layer.
- An object of the present invention is to provide a thin multi-layer circuit board which is so constituted that, when a remodeling pad is being used, this remodeling pad can be easily cut, and a process for fabricating the same.
- Another object of the present invention is to provide a process for fabricating a thin multi-layer circuit board, which does not require a process for etching gold plating at the time of forming a pad by plating gold on the thin multi-layer circuit board.
- A further object of the present invention is to provide a process for fabricating a thin multi-layer circuit board which is capable of forming a thin chromium film on the wiring pattern layers without relying upon the lift-off method when a number of wiring pattern layers are stacked on an insulating plate-like substrate.
- A still further object of the present invention is to provide a process for fabricating a thin multi-layer circuit board which is capable of removing a defective wiring pattern layer without damaging the wiring pattern layers on the lower side when a number of wiring patterns are stacked on an insulating plate-like substrate.
- A yet further object of the present invention is to provide a method of pre-baking a photosensitive polyimide resin layer that is applied in the fabrication of a multi-layer circuit board, the pre-baking method making it possible not only to uniformly heat the insulating plate-like substrate from the back side thereof but also to carry out the operation with excellent efficiency, as well as to provide a heat-accumulating block used for the method of pre-baking.
- According to a first aspect of the present invention, there is provided a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern using said wiring pattern layers, wherein a barrier metal exclusion zone is prepared by forming a metallic barrier layer on said wiring pattern layer in an electronic part-mounting region, a remodeling pad layer is formed on said metallic barrier layer neighboring said barrier metal exclusion zone, and an electronic part-mounting pad layer is formed neighboring said remodeling pad layer.
- According to the first aspect of the present invention, furthermore, there is provided a thin multi-layer circuit board which is obtained by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier layer is formed on the wiring pattern layer in an electronic part-mounting region, a barrier metal exclusion zone is included in said metallic barrier layer, and a remodeling pad layer and an electronic part-mounting pad layer are formed on said metallic barrier layer, said remodeling pad layer being arranged neighboring said barrier metal exclusion zone and said electronic part-mounting pad layer being arranged neighboring said remodeling pad layer.
- In the process for fabrication and the thin multi-layer circuit board according to the first aspect of the present invention as described above, the barrier metal exclusion zone is prepared neighboring the remodeling pad layer. In using the remodeling pad, therefore, the wiring pattern layer is cut by a YAG laser along the barrier metal exclusion zone in order to cut the electrical connection between the remodeling pad and the wiring pattern layer. Therefore, destruction of the insulating layer in the thin multi-layer circuit board is minimized. Moreover, the barrier metal is formed maintaining a sufficient thickness making it possible to prevent the barrier metal from being corroded at the time of soldering lead wires onto the electronic part-mounting pad and onto the remodeling pad.
- According to a second aspect of the present invention, there is provided a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier layer is formed on the wiring pattern layer in an electronic part-mounting region, a pad-forming resist is formed in said metallic barrier layer, a gold pad layer of a predetermined shape is formed on said metallic barrier layer by using said pad-forming resist, and said pad-forming resist is removed.
- According to the second aspect of the present invention, there is provided a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a pad-forming resist is formed on the wiring pattern layer in an electronic part-mounting region, a metallic barrier layer is formed on the wiring pattern layer, a gold pad layer of a predetermined shape is formed on the metallic barrier layer using the pad-forming resist, and said pad-forming resist is removed.
- In the process for fabrication according to the second aspect of the present invention, the gold pad layer is formed into a predetermined shape by using the pad-forming resist without the need of using a highly toxic gold-etching solution, contributing to the safely of the operation.
- According to a third aspect of the present invention, there is provided a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein the wiring pattern layers are formed on the insulating layers by sequentially forming a first thin chromium film, a copper layer and a second thin chromium film on said insulating layers followed by etching.
- In the process for fabrication according to the third aspect of the present invention, the wiring pattern layers on the insulating layers are formed by sequentially forming the first thin chromium film, the copper layer and the second thin chromium film on the insulating layers followed by etching. Therefore, there is no need of employing a lift-off method for forming the second thin chromium film on the insulating layers.
- According to a fourth aspect of the present invention, there is provided a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier film covers the wiring pattern layer every time a wiring pattern layer is formed. The metallic barrier film can be formed by either the lift-off method or an etching method. When each wiring pattern layer is made up of a thin chromium film and a copper layer formed on the thin chromium film, the metallic barrier film covers the copper layer. When each wiring pattern layer is made up of a first thin chromium film, a copper layer formed on the thin chromium film and a second thin chromium film formed on the copper layer, the metallic barrier film covers the second thin chromium film.
- In the process for fabrication according to the fourth aspect of the present invention, the metallic barrier film covers the wiring pattern layer every time a wiring pattern layer is formed. Therefore, a defective wiring pattern layer can be removed by wet-etching, and the etching solution is prevented from infiltrating into the wiring pattern layers of the lower side. It is therefore possible to form the wiring pattern again after a defective wiring pattern layer is removed, contributing greatly to decreasing the cost of producing the thin multi-layer circuit board.
- According to a fifth aspect of the present invention, there is provided a method of pre-baking a photosensitive polyimide resin layer in a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a heat-accumulating block is arranged in an atmosphere of a predetermined temperature, and said insulating plate-like substrate is placed over the heat-accumulating block close thereto and is heated. Desirably, a gap of about 0.3 mm is maintained between the heat-accumulating block and the insulating plate-like substrate. Desirably, the heat-accumulating block is constituted by a block member having a flat heating surface, a pair of guide walls that extend in parallel along the opposing side edges of the heating surface of the block member, and rail elements that extend along the corners formed by the pair of guide walls and the heating surface, and the pair of guide walls have a lateral width which is slightly larger than a distance between the opposing side edges on one side of the insulating plate-like substrate.
- In the pre-baking method according to the fifth aspect of the present invention, the heat-accumulating block is disposed in an atmosphere heated at a predetermined temperature, the insulating plate-like substrate is placed over the heat-accumulating block close thereto and is heated. Therefore, the insulating plate-like substrate can be uniformly heated from the back side thereof without being stuck to the heat-accumulating block. With the heat-accumulating block according to the fifth aspect of the present invention, furthermore, the insulating plate-like substrate is placed on the rail elements from the ends on one side of the pair of guide walls and is moved over the flat surface of the heat-accumulating block and is pulled out by being placed on the rail elements. Therefore, even when a plurality of such heat-accumulating blocks are arranged to be stacked in an oven, the insulating plate-like substrates can be easily put into, and pulled out of, the heat-accumulating blocks.
- FIGS.1 to 16 are diagrams schematically illustrating the steps in a process for fabricating thin multi-layer circuit boards according to a first aspect of the present invention;
- FIGS.17 to 26 are diagrams schematically illustrating the steps in a process for fabricating thin multi-layer circuit boards according to a second aspect of the present invention;
- FIGS.27 to 35 are diagrams schematically illustrating the steps in a process for fabricating thin multi-layer circuit boards according to a third aspect of the present invention;
- FIG. 36 is a diagram schematically illustrating a step in a process for fabricating thin multi-layer circuit boards according to a fourth aspect of the present invention;
- FIGS.37 to 39 are diagrams schematically illustrating the steps in a process for applying a metallic barrier film onto a wiring pattern layer in the thin multi-layer circuit substrate shown in FIG. 36;
- FIGS.40 to 42 are diagrams schematically illustrating the steps in another process for applying a metallic barrier film onto a wiring pattern layer in the thin multi-layer circuit substrate shown in FIG. 36;
- FIG. 43 is a diagram which schematically illustrates the principle of a pre-baking method according to a fifth aspect of the present invention;
- FIG. 44 is a graph showing the distribution of temperature rise of when a ceramic substrate is heated by the pre-baking method shown in FIG. 43;
- FIG. 45 is a graph showing the distribution of temperature rise of when a ceramic substrate is heated by a pre-baking method which is different from the pre-baking method shown in FIG. 43;
- FIG. 46 is a perspective view of a heat-accumulating block that is suited for putting into practice the pre-baking method according to the fifth aspect of the present invention;
- FIG. 47 is a diagram illustrating an end surface of the heat-accumulating block;
- FIG. 48 is a graph showing the distribution of temperature rise of when a ceramic substrate is heated by using the heat-accumulating blocks of FIGS. 46 and 47; and
- FIGS.49 to 72 are diagrams schematically illustrating the steps in a conventional representative process for fabricating thin multi-layer circuit boards.
- Before a detailed explanation of some embodiments of the present invention is given, a conventional process for producing a thin multi-layer circuit board will be described with reference to the accompanying FIGS.49 to 72.
- Referring, first, to FIG. 49, a
thin chromium film 12 is formed on, for example, aceramic substrate 10, and athin copper film 14 is formed on thethin chromium film 12. Thethin chromium film 12 and thethin copper film 14 are usually formed by sputtering. Then, in order to form a first wiring pattern on thethin copper film 14, a copper-platingresist 16 is formed on thethin copper film 14 as shown in FIG. 50. By plating copper on the copper-plating resist 16, a copper-platedlayer 18 is formed on the first wiring pattern as shown in FIG. 51. After the copper-plated layer is formed, the copper-platingresist 16 is removed as shown in FIG. 52 and, then, athin chromium film 20 is formed again on thethin copper film 14 and on the copper-platedlayer 18 as shown in FIG. 53. Referring next to FIG. 54, anetching resist 22 is formed on the first wiring pattern. Then, by effecting the etching, thethin copper film 14 and thethin chromium film 12 are removed from the regions other than the first wiring pattern as shown in FIG. 55. Thereafter, theetching resist 22 is removed to obtain a firstwiring pattern layer 24 on theceramic substrate 10 as shown in FIG. 56. Thethin chromium film 12 has a thickness of, for example, about 0.08 μ, thethin chromium film 22 has a thickness of, for example, about 0.15 μ, and copper layers (12, 18) sandwiched between these thin chromium films have a thickness of, for example, about 5 μ. - After the first
wiring pattern layer 24 is formed on theceramic substrate 10, an insulating layer such as a photosensitivepolyimide resin layer 26 is applied thereon and is pre-baked as shown in FIG. 57. Then, the insulatinglayer 26 is developed by exposure to light through a predetermined pattern, and whereby a viahole 28 is formed at a predetermined portion of the insulatinglayer 26 as shown in FIG. 58. After the insulatinglayer 26 is cured, athin chromium film 30 and athin copper film 32 are formed thereon by sputtering as shown in FIG. 59. Then, in order to form a second wiring pattern on thethin copper film 32, a plating resist 34 is formed on thethin copper film 32 as shown in FIG. 60. By plating copper on the plating resist 34, a copper-platedlayer 36 is formed on the second wiring pattern as shown in FIG. 61. - In the region, i.e., in the electronic part-mounting region shown in FIGS.49 to 61, nickel and gold are further plated on the copper-plated
layer 36 thereby to form a nickel-platedlayer 38 and a gold-platedlayer 40. Then, the plating resist 34 is removed as shown in FIG. 62. Referring next to FIG. 63, an etching resist 42 is formed on the second wiring pattern, followed by etching to remove thethin copper film 32 and thethin chromium film 30 from the regions other than the second wiring pattern as shown in FIG. 64. Thereafter, the etching resist 42 is removed to obtain asecond wiring pattern 44 on the insulatinglayer 26 as shown in FIG. 65. As will be obvious from FIG. 65, the firstwiring pattern layer 24 and the secondwiring pattern layer 44 are connected to each other through conducting metals in a via hole, and a predetermined circuit pattern is constituted by these two wiring pattern layers 24 and 44. Thethin chromium film 30 has a thickness of, for example, about 0.08 μ, the copper layers (32, 36) on thethin chromium film 30 have a thickness of, for example, about 4 μ, the nickel-platedlayer 38 has a thickness of, for example, about 3 μ, and the gold-platedlayer 40 has a thickness of, for example, about 0.6 μ. - A gold-etching resist46 is formed in a predetermined pattern on the electronic part-mounting region, i.e., on the gold-plated
layer 40 as shown in FIG. 66, and then gold is removed by etching. As shown in FIG. 67, therefore, the gold-platedlayer 40 is partly removed and the nickel-platedlayer 38 is exposed. Thereafter, the gold-etching resist 46 is removed as shown in FIG. 68, and, then, a chromium lift-off resist 48 is formed on the insulatinglayer 26 in order to form a thin chromium film on the secondwiring pattern layer 44. In this case, the chromium lift-off resist 48 is applied onto the gold-platedlayer 40, too, as shown in FIG. 69. By effecting the chromium lift-off sputtering, athin chromium film 50 is formed on the secondwiring pattern layer 44 and on the chromium lift-off resist 48 as shown in FIG. 70. The chromium lift-off resist 48 is then removed as shown in FIG. 71, and thethin chromium film 50 is left on the secondwiring pattern layer 44 only. Then, as shown in FIG. 72, anovercoat insulating layer 52 composed of a polyimide resin is applied onto the insulatinglayer 26 and onto the secondwiring pattern layer 44, and the surface of the gold-platedlayer 40 is exposed to obtain a thin multi-layer circuit board. - In the conventional thin multi-layer circuit board shown in FIG. 72, the gold-plated
layer 40 is divided into three exposedpads pad 40 a serves as a part-mounting pad for soldering the lead wires when an electronic part is mounted. Thepad 40 b serves as a remodeling pad that is used for remodeling or repairing the circuit wiring, and is used for soldering the lead wires as required for remodeling or repairing the circuit wiring. Thepad 40 c is used for only electrically connecting the part-mountingpad 40 a and theremodeling pad 40 b to the wiring pattern layers 24 and 44. Depending upon the cases, thepad 40 c may be covered with theovercoat insulating layer 52. - In the above-mentioned thin multi-layer circuit board, the nickel-plated
layer 38 works as a metallic barrier layer for protecting the copper layers (32, 36) when a lead wire is soldered onto the part-mountingpad 40 a and/or the remodeling pad. If described in detail, when there is no nickel-platedlayer 38, the solder material permeates into the copper layers (32, 36) at the time of soldering, causing the electric properties and mechanical properties to change. In order to prevent the solder material from permeating into the copper layers (32, 36), therefore, the nickel-platedlayer 38 is necessary. The nickel-platedlayer 38 must have a thickness of at least 3 μ so that it works as a metallic barrier layer to a sufficient degree. When the thickness is smaller than 3 μ, the nickel-platedlayer 38 corrodes at the time of soldering, causing a problem in that the solder material permeates into the copper layers (32, 36). - In the conventional thin multi-layer circuit board, however, the presence of a metallic barrier layer, i.e., the nickel-plated
layer 38, becomes a problem at the time of remodeling or repairing the circuit wiring. That is, to remodel or repair the circuit wiring, the electrical connection between theremodeling pad 40 b and the wiring pattern layers 24, 44 must be cut off. This is done by cutting the conductor layer between theremodeling pad 40 b and thepad 40 c by using a YAG laser beam. Here, however, a problem arises that the nickel-platedlayer 38 cannot be desirably cut by the YAG laser beam. In particular, it becomes difficult to cut the nickel-platedlayer 38 when its thickness exceeds 3 μ. The nickel-platedlayer 38 can be cut by increasing the output of the YAG laser beam but this causes the insulatinglayer 26 to be damaged to a large extent. It is not, therefore, possible to increase the output of the YAG laser beam. The thickness of the nickel-platedlayer 38 can be decreased so that it can be easily cut by the YAG laser beam but this is accompanied by the problem of corrosion at the time of soldering. - Moreover, it has been pointed out that the conventional process for producing thin multi-layer circuit boards involves the processing for etching the gold-plated layer40 (FIGS. 66 and 67). That is, the processing for etching the gold-plated
layer 40 requires a strongly toxic solvent, and it is desirable to exclude such an etching processing from the steps of producing thin multi-layer circuit boards. - It has further been pointed out that the conventional process for producing thin multi-layer circuit boards employs a lift-off method for forming the
thin chromium film 50 on the second wiring pattern layer 44 (FIGS. 69, 70, 71), which is another problem. That is, after thethin chromium film 50 is formed, it is not easy to remove the lift-off resist 48 and a relatively long period of time is required for the removal step. - In the conventional process for producing thin multi-layer circuit boards, furthermore, there is a problem in sequentially stacking a number of wiring pattern layers on the ceramic substrate. In detail, when ten wiring pattern layers, for instance, are stacked on the ceramic substrate, up to nine wiring pattern layers can be properly formed but the tenth wiring pattern layer may be broken or short-circuited. If this happens, the device must be discarded as a defective product. Attempts have been made to remove the defective wiring pattern layer by wet-etching and to form the wiring pattern again but this permits the etching solution to infiltrate into the lower wiring pattern layers through the via. Therefore, the lower wiring pattern layers are damaged, and this makes it difficult to form the wiring pattern layer again.
- A further problem in the conventional process for producing thin multi-layer circuit boards resides in the pre-baking of the photosensitive polyimide resin. In detail, the photosensitive polyimide resin is used not only as an insulating material but also as a photoresist material at the time of forming a metal-plated layer. The polyimide resin is pre-baked when it is applied in the process for producing thin multi-layer circuit boards. Here, “pre-baking” means vaporizing the solvent by leaving the polyimide resin in an atmosphere heated to a temperature of about 80°. In this case, it is desirable to uniformly heat the ceramic substrate from the back side thereof. Thus, via holes and the like are formed with a high resolution in the polyimide resin layer by exposure to light and development. That is, via holes and the like can be formed accurately. For this purpose, a heat-accumulating block made of a material having excellent heat-accumulating property was placed in an oven and a ceramic substrate was placed on the heat-accumulating block in order to uniformly heat the ceramic substrate from the back side thereof. This resulted in failure because, though the ceramic substrate is uniformly heated, the polyimide resin that reached the back surface of the ceramic substrate when the polyimide resin was applied causes the ceramic substrate to stick onto the heat-accumulating block to hinder the workability to a great extent.
- Thus, in order to solve the above-mentioned problems and attain the objects of the present invention discussed hereinbefore, some embodiments of the first through fifth aspects of the present invention will be presented.
- An embodiment of a process for fabricating thin multi-layer circuit boards according to a first aspect of the present invention will now be described with reference to FIGS.1 to 17 of the accompanying drawings. The initial steps in the fabrication process according to the first aspect of the present invention are substantially the same as those of the conventional fabrication process described earlier, and are not mentioned again.
- FIG. 1 illustrates a state where a first
wiring pattern layer 24 is formed on aceramic substrate 10, an insulating layer such as a photosensitivepolyimide resin layer 26 is applied onto the firstwiring pattern layer 24 and after pre-baked a viahole 28 is formed and, then, after the insulatinglayer 26 is cured, athin chromium film 30 and athin copper film 32 are formed by, for example, sputtering. On thethin copper film 32 is formed a copper-plating resist 54 for forming a second wiring pattern as shown in FIG. 1. When copper is plated on the copper-plating resist 54, a copper-platedlayer 56 is formed on the second wiring pattern as shown in FIG. 2 and, thereafter, the copper-plating resist 54 is removed as shown in FIG. 3. - The diagramed region is an electronic part-mounting region. In this region, nickel and gold are further plated on the copper-plated
layer 56. For this purpose, a plating resist 58 is formed as shown in FIG. 4. In this case, a plating resist 58 a, too, is formed on the copper-platedlayer 56 to prepare a nickel exclusion zone on a portion thereof. After the plating resist is formed, nickel is plated to form a nickel-platedlayer 60 as shown in FIG. 5 and, then, gold is plated on the nickel-platedlayer 60 to form a gold-platedlayer 62. After the plating, the plating resist is removed as shown in FIG. 6. In this case, a zone on a part of the surface of the copper-platedlayer 56, i.e., the zone to where the plating resist 58 a is applied turns into a nickel exclusion zone. - After the plating resist is removed, an etching resist64 is formed on the second wiring pattern as shown in FIG. 7. By effecting the etching thereto, the
thin copper film 32 and thethin chromium film 30 are removed from the regions other than the second wiring pattern as shown in FIG. 8. Then, the etching resist 64 is removed to obtain a secondwiring pattern layer 66 on the insulatinglayer 26 as shown in FIG. 9. As will be obvious from FIG. 9, the firstwiring pattern layer 24 and the secondwiring pattern layer 66 are electrically connected together by conducting metals in the via hole, and whereby a predetermined circuit pattern is constituted by these two wiring pattern layers 24 and 66. - On the gold-plated
layer 62 is formed a gold-etching resist 68 in a predetermined pattern as shown in FIG. 10 and, then, gold is etched. As a result, the gold-platedlayer 62 is partly removed as shown in FIG. 11, and is divided into three pad layers. After, the gold-etching resist 68 is removed as shown in FIG. 12, the three gold-plated layers, which are the pad layers, serve as an electronic part-mountingpad 62 a, as aremodeling pad 62 b and as aconnection pad 62 c. Then, a chromium lift-off resist 70 is formed on the insulatinglayer 26 as shown in FIG. 13 in order to form a thin chromium film on the secondwiring pattern layer 66 and, at this time, the chromium lift-off resist 70 is also formed on the electronic part-mountingpad 62 a and on theremodeling pad 62 b. After the chromium lift-off sputtering is effected, athin chromium film 72 is formed on the secondwiring pattern layer 66 and on the chromium lift-off resist 70 as shown in FIG. 14. Then, the chromium liftoff resist 70 is removed as shown in FIG. 15, and thethin chromium film 72 is left on the secondwiring pattern layer 66 only. Then, as shown in FIG. 16, anovercoat insulating layer 74 composed of a polyimide resin is applied onto the insulatinglayer 26 and onto the secondwiring pattern layer 66 while exposing the electronic part-mountingpad 62 a and theremodeling pad 62 b through theovercoat insulating layer 74. - When the
remodeling pad 62 b is used for remodeling or repairing the circuit wiring in the thus fabricated thin multi-layer circuit board, the electric connection between theremodeling pad 62 b and the second wiring pattern layer can be easily cut off by a low output YAG laser or a similar laser. This is because, the nickel exclusion zone denoted byreference numeral 76 is used as a portion to be cut. According to the first aspect of the present invention, furthermore, the nickel-platedlayer 60 can be formed maintaining a thickness of not smaller than 3 μ and, preferably, maintaining a thickness of about 3.5 μ, contributing to the corrosion resistance of the nickel-platedlayer 60 when soldering lead wires to the electronic part-mountingpad 62 a and to theremodeling pad 62 b occurs. - FIGS.17 to 27 illustrate an embodiment of the process for fabricating thin multi-layer circuit boards according to a second aspect of the present invention. The initial steps in this fabrication process are substantially the same as those of the fabrication process according to the first aspect of the present invention. That is, a first
wiring pattern layer 24 is formed on aceramic substrate 10, a photosensitivepolyimide resin layer 26 is applied onto the firstwiring patten layer 24 and after pre-baked a viahole 28 is formed, and, then, after the insulatinglayer 26 is cured, athin chromium film 30 and athin copper film 32 are formed by, for example, sputtering, and a copper-plating layer 56 is formed on thethin copper film 32 in order to form a second wiring pattern, which is the same as the fabrication process according to the first aspect of the present invention. - After the copper-plated
layer 56 is formed, nickel and gold are further plated on the copper-platedlayer 56 in the electronic part-mounting region. For this purpose, a plating resist 78 is formed around the electronic part-mounting region as shown in FIG. 17, and on the inside thereof are formed plating resists 78 a and 78 b on the copper-platedlayer 56. After the plating resist is formed, nickel is plated to form a nickel-platedlayer 80 as shown in FIG. 18 and, then, gold is plated on the nickel-platedlayer 80 to form a gold-platedlayer 82. Thereafter, the plating resist is removed as shown in FIG. 20. - Referring to FIG. 20, after the plating resist is removed, an etching resist84 is formed on the second wiring pattern and, then, etching is effected thereto remove the
thin copper film 32 and thethin chromium film 30 from the regions other than the second wiring pattern as shown in FIG. 21. Then, the etching resist 84 is removed to obtain a secondwiring pattern layer 86 on the insulatinglayer 26 as shown in FIG. 22. Here, it should be noted that the nickel-platedlayer 80 and the gold-platedlayer 82 have, respectively, been divided into three by the plating resists 78 a and 78 b at the time of plating, and the divided gold-plated layer serves as the electronic part-mountingpad 82 a, as theremodeling pad 82 b and as theconnection pad 82 c, eliminating the need of etching the gold-platedlayer 80. - Thereafter, a chromium lift-off resist88 is formed on the insulating
layer 26, as shown in FIG. 23 to form a thin chromium layer on the secondwiring pattern layer 86 and, at this time, the chromium lift-off resist 88 is also formed on the electronic part-mountingpad 82 a and on theremodeling pad 82 b. After chromium lift-off sputtering is effected, athin chromium film 90 is formed on the secondwiring pattern layer 86 and on the chromium lift-off resist 88 as shown in FIG. 24. Then, as the chromium lift-off resist 88 is removed as shown in FIG. 25, thethin chromium film 90 is left on the secondwiring pattern layer 86 only. Thereafter as shown in FIG. 24, anovercoat insulating layer 92 composed of a polyimide resin is applied onto the insulatinglayer 26 and onto the secondwiring pattern layer 86 while the electronic part-mountingpad 82 a and theremodeling pad 82 b are exposed through theovercoat insulating layer 92. - The aforementioned fabrication process has a feature in that there is no need to effect the etching for the gold-plated
layer 82 and, hence, the use of a highly toxic etching solution can be avoided. According to this embodiment, furthermore, theremodeling pad 82 b is disposed neighboring the nickel exclusion region and, hence, the electrical connection between theremodeling pad 62 b and the secondwiring pattern layer 86 can be easily cut by a low output YAG laser or the like at the time of remodeling or repairing the circuit wiring as in first aspect of the present invention. In the fabrication method according to the second aspect of the present invention, i.e., in the fabrication which excludes the gold-etching processing, however, the nickel-platedlayer 80 may be extended without being divided. In this case, after the nickel-plated layer is formed in an extending manner, plating resists (78 a, 78 b) as shown in FIG. 17 are formed on the nickel-plated layer in the electronic part-mounting region. - FIGS.27 to 36 illustrate an embodiment of the process for fabricating thin multi-layer circuit boards according to a third aspect of the present invention. The initial steps in this fabrication process are substantially the same as those of the fabrication process according to the first aspect of the present invention. That is, a first
wiring pattern layer 24 is formed on aceramic substrate 10, a photosensitivepolyimide resin layer 26 is applied onto the firstwiring pattern layer 24 and is pre-baked to form a viahole 28, and, then, after the insulatinglayer 26 is cured, athin chromium film 30 and athin copper film 32 are formed by, for example, sputtering, and a copper-plating layer 56 is formed on thethin copper film 32 in order to form a second wiring pattern, which are the same as in the fabrication process according to the first aspect of the present invention. - After the copper-plated
layer 56 is formed as shown in FIG. 27, athin chromium film 94 is formed by, for example, sputtering on thethin copper film 32 and on the copper-platedlayer 56. After thethin chromium film 94 is formed, a resist 96 is formed around the electronic part-mounting region as shown in FIG. 28 and, besides, resists 96 a and 96 b are formed on thethin chromium film 94 on the inside of the electronic part-mounting region. After the resist is formed, the etching is effected to remove thethin chromium film 94 from the electronic part-mounting region as shown in FIG. 29. Then, in the electronic part-mounting region, a nickel-platedlayer 98 is formed as shown in FIG. 30. Thereafter, a gold-platedlayer 100 is formed by plating gold on the nickel-platedlayer 98 and, then, plating resists 96, 96 a and 96 b are removed as shown in FIG. 31. - After the plating resists are removed, an etching resist102 is formed on the second wiring pattern as shown in FIG. 32. By effecting the etching thereto, the
thin chromium film 94, thethin copper film 32 and thethin chromium film 30 are removed from the regions other than the second wiring pattern as shown in FIG. 33. Thereafter, the etching resist 102 is removed to obtain a secondwiring pattern layer 104 on the insulatinglayer 26 as shown in FIG. 34. As the case of the embodiment (FIGS. 17 to 26) according to the second aspect of the present invention, the nickel-platedlayer 98 and the gold-platedlayer 100 are, respectively, divided into three by the plating resists 96 a and 96 b at the time of plating, and the divided gold-plated layers serve as an electronic part-mountingpad 100 a, as aremodeling pad 100 b and as aconnection pad 100 c, eliminating the need of effecting the etching for the gold-platedlayer 100. Then, as shown in FIG. 35, anovercoat insulating layer 106 composed of a polyimide resin is applied onto the insulatinglayer 26 and onto the secondwiring pattern layer 104 while exposing the electronic part-mountingpad 100 a and theremodeling pad 100 b through theovercoat insulating layer 92. - The aforementioned fabrication process has a novel feature in that the
thin chromium film 94 is formed on the secondwiring pattern layer 104 formed on the insulatinglayer 26 without relying upon the lift-off method. This embodiment has not only the feature according to the first aspect of the present invention in that the electrical connection between theremodeling pad 100 b and the secondwiring pattern layer 104 is easily cut by a low output YAG laser or the like at the time of remodeling or repairing the circuit wiring but also the feature, according to the second aspect of the present invention, that there is no need to etch the gold-platedlayer 100. In addition, it should be understood that the feature according to the third aspect of the present invention, i.e., forming the thin chromium film on the insulating layer without relying upon the lift-off method, by itself constitutes an invention. - FIG. 36 illustrates, in the form of an intermediate product, a thin multi-layer circuit board fabricated by the process for fabrication according to a fourth aspect of the present invention. This intermediate product is in a stage in which wiring pattern layers and polyimide resin layers are alternately stacked on a
ceramic substrate 108. That is, on theceramic substrate 108 is formed a firstwiring pattern layer 110 which is covered with a first polyimideresin insulating layer 112. On the first polyimideresin insulating layer 112 is formed a secondwiring pattern layer 114 which is covered with a second polyimideresin insulating layer 116. On the second polyimideresin insulating layer 116 is formed a thirdwiring pattern layer 118 which is covered with a third polyimideresin insulating layer 120. The first to third wiring pattern layers 110, 114 and 118 are connected together through vias formed in the polyimideresin insulating layers wiring patterns thin chromium films 110 a; 110 b, 114 a; 114 b, 116 a; 116 b, as well as copper layers 110 c, 114 c and 118 c formed among the thin chromium films. The wiring pattern layers 110, 114, 118 and the polyimideresin insulating layers - In this embodiment, the
thin chromium films metallic barrier film 122 every time the wiring pattern layers 110, 114 and 118 are formed, themetallic barrier film 122 being comprised of, for example, titanium nitride, platinum or the like. Themetallic barrier film 122 can be incorporated at the time of forming the wiring pattern layers 110, 114 and 118 relying, for example, upon the etching as shown in FIGS. 37 to 39. Referring to FIG. 37, a firstthin chromium film 110 a is, first, formed by sputtering on theceramic substrate 108 and, then, copper is sputtered thereon. Next, acopper layer 110 c is formed by plating copper on a region that corresponds to the first wiring pattern, then, a secondthin chromium film 110 b is formed by sputtering and ametallic barrier film 122 is formed thereon by sputtering. Referring next to FIG. 38, an etching resist 124 is formed on a predetermined region and the etching is effected to obtain a firstwiring pattern layer 110 as shown in FIG. 39. Themetallic barrier film 122 of titanium nitride or platinum is very stable against an etching solution for chromium or copper. When themetallic barrier film 122 is composed of titanium nitride, therefore, the etching solution will comprise concentrated hydrofluoric acid, concentrated nitric acid and water. When themetallic barrier film 122 is composed of platinum, the etching solution will be aqua regia or a diluted aqua regia solution. - As shown in FIGS.40 to 42, furthermore, the metallic barrier film can also be formed by the lift-off method. That is, a first
thin chromium film 110 a is formed by sputtering on theceramic substrate 108 and, then, copper is sputtered thereon. Next, acopper layer 110 c is formed by plating copper on a region corresponding to the first wiring pattern, and the firstthin chromium film 110 a and thecopper layer 110 c are formed into a predetermined wiring pattern by etching. Then, a lift-off resist 126 is formed thereon as shown in FIG. 40. Referring next to FIG. 42, athin chromium film 110 b and ametallic barrier film 122 are formed by sputtering. Then, the lift-off resist 126 is removed to obtain a firstwiring pattern layer 110 on theceramic substrate 120. - In the process for fabrication according to the fourth aspect of the present invention, a defective wiring pattern layer that is formed in the step of alternately stacking the wiring pattern layers and the polyimide resin insulating layers, can be formed again. For instance, in case a defect is found after the third
wiring pattern layer 118 is formed, the thirdwiring pattern layer 118 is removed without at all damaging the secondwiring pattern layer 116. In detail, themetallic barrier film 122 of the thirdwiring pattern layer 118 is removed by using the above-mentioned etching solution and, then, the secondthin chromium film 118 b,copper layer 118 c and first thin chromium film 118 a are removed by using a known etching solution. In this case, the secondwiring pattern layer 114 has been covered with themetallic barrier film 122, and the etching solution for chromium and copper does not permeate into the secondwiring pattern layer 114 through the via. Accordingly, the thirdwiring pattern layer 118 that has been removed can be formed again. - In the embodiment according to the fourth aspect of the present invention, the
metallic barrier film 122 covers the secondthin chromium films metallic barrier film 122 may be formed between the copper layers 110 c, 114 b, 118 b and the secondthin chromium films thin chromium films - In the process for fabricating thin multi-layer circuit boards as described above, the photosensitive polyimide resin is used not only as an insulating material but also as a resist material. When the polyimide resin is applied, the ceramic substrate is put into the oven and is pre-baked. It was mentioned already that in this case, the ceramic substrate is uniformly heated from the back side thereof. A fifth aspect of the present invention is directed to improving the pre-baking method.
- FIG. 43 illustrates the principle of the pre-baking method according to the fifth aspect of the present invention, wherein
reference numeral 128 denotes a heat-accumulating block which is made of, for example, aluminum. The heat-accumulatingblock 128 is left to stand in an oven (not shown) having an atmospheric temperature of, for example, about 80°. The heat-accumulatingblock 128 has a flat upper surface, and a pair ofcopper strips 130 are disposed along the opposing side edges on the surface thereof. Aceramic substrate 132 coated with the polyimide resin is placed on the pair of copper strips 130, and a gap of about 0.3 mm is maintained between the upper surface of the heat-accumulatingblock 128 and theceramic substrate 132. Therefore, theceramic substrate 132 is gradually heated from the back side thereof by receiving radiant heat. At this moment, the rise in the temperature is measured at five points at equal distances along the diagonal of theceramic substrate 132. The results are shown in a graph of FIG. 44 from which it will be obvious that the temperature rises are nearly the same at all of the above-mentioned five points. FIG. 45 illustrates similar temperature rises in the case when theceramic substrate 132 is placed on the upper surface of the heat-accumulating block. It can be regarded that the temperature rise is substantially the same at five points maintaining an equal distance along the diagonal lines of theceramic substrate 132. That is, it is desired to place theceramic substrate 132 directly on the upper surface of the heat-accumulating block in order to uniformly heat theceramic substrate 132. As mentioned earlier, however, it is not possible to place theceramic substrate 132 directly on the heat-accumulatingblock 128. - FIGS. 46 and 47 illustrate a heat-accumulating
block 134 adapted to putting the pre-baking method of the present invention into practice. The heat-accumulatingblock 134 comprises ablock member 138 having aflat heating surface 136, a pair ofguide walls 140 that extend in parallel along the opposing sides of theheating surface 136 of theblock member 138, andrail elements 142 that extend along the corners formed by theguide walls 140 and theheating surface 136. The lateral width of the pair ofguide wall portions 140 is slightly broader than the distance between the opposing side edges of the insulating plate-like substrate. With this constitution, theceramic substrate 132 is placed on therail elements 142 from the ends on one side of the pair ofguide walls 140, and is pushed; i.e., theceramic substrate 132 can be easily moved on theflat surface 136 of the heat-accumulatingblock 134 and can be easily pulled out along therail elements 142. Even when a plurality of heat-accumulatingblocks 134 are arranged in a plurality of stages to be stacked in the up-and-down direction in the oven, the ceramic substrates can be easily put into, and taken out from, the heat-accumulatingblocks 134, enabling the pre-baking processing to be quickly executed. - FIG. 48 is a graph showing the results of the measurement of the temperature rise distribution in the manner described above in the case when the
ceramic substrate 132 is heated by being placed on the heat-accumulatingblock 134. It will be obvious from this graph that theceramic substrate 132 is heated substantially uniformly though the temperature rise distribution is slightly disturbed immediately after the start of the heating.
Claims (15)
1. A process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers (24, 66) and insulating layers (26, 78) on an insulating plate-like substrate (10), and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a barrier metal exclusion zone (76) is prepared while forming a metallic barrier layer (60) on said wiring pattern layer in an electronic part-mounting region, a remodeling pad layer (62 b) is formed on said metallic barrier layer neighboring said barrier metal exclusion zone, and an electronic part-mounting pad layer (62 a) is formed neighboring said remodeling pad layer (62 b).
2. A process for fabrication according to , wherein said metallic barrier layer (60) is formed by plating nickel, and said barrier metal extrusion zone is prepared by using a resist to plating at the time when nickel is plated.
claim 1
3. A thin multi-layer circuit board which is obtained by alternately stacking wiring pattern layers (24, 86) and insulating layers (26, 92) on an insulating plate-like substrate (10), and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier layer (80) is formed on the wiring pattern layer in an electronic part-mounting region, a barrier metal exclusion zone is included in said metallic barrier layer, and a remodeling pad layer (82 b) and an electronic part-mounting pad layer (82 a) are formed on said metallic barrier layer, said remodeling pad layer being arranged neighboring said barrier metal exclusion zone and said electronic part-mounting pad layer being arranged neighboring said remodeling pad layer.
4. A process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers (24, 104) and insulating layers (26, 106) on an insulating plate-like substrate (10), and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier layer is formed on the wiring pattern layer in an electronic part-mounting region, a pad-forming resist is formed in said metallic barrier layer, a gold pad layer of a predetermined shape is formed on said metallic barrier layer by using said pad-forming resist, and said pad-forming resist is removed.
5. A process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a pad-forming resist is formed on the wiring pattern layer in an electronic part-mounting region, a metallic barrier layer is formed on the wiring pattern layer, a gold pad layer of a predetermined shape is formed on the metallic barrier layer using the pad-forming resist, and said pad-forming resist is removed.
6. A process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein the wiring pattern layers are formed on the insulating layers by sequentially forming a first thin chromium film, a copper layer and a second thin chromium film on said insulating layers followed by etching.
7. A process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a metallic barrier film covers the wiring pattern layer every time said wiring pattern layer is formed.
8. A fabrication process according to , wherein said metallic barrier film is formed by a liftoff method.
claim 7
9. A fabrication process according to , wherein said metallic barrier film is formed by etching.
claim 7
10. A fabrication process according to , wherein said wiring pattern layers are constituted by a thin chromium film and a copper layer formed on said thin chromium film, and said metallic barrier film covers said copper layer.
claim 7
11. A fabrication process according to , wherein said wiring pattern layers are constituted by a first thin chromium film, a copper layer formed on said thin chromium film and a second thin chromium film formed on said copper layer, and said metallic barrier film covers said second thin chromium film.
claim 7
12. A method of pre-baking a photosensitive polyimide resin layer in a process for fabricating thin multi-layer circuit boards by alternately stacking wiring pattern layers and insulating layers on an insulating plate-like substrate, and electrically connecting said wiring pattern layers through vias in said insulating layers in order to constitute a predetermined circuit pattern by said wiring pattern layers, wherein a heat-accumulating block is arranged in an atmosphere of a predetermined temperature, and said insulating plate-like substrate is placed over the heat-accumulating block close thereto and is heated.
13. A pre-baking method according to , wherein a gap of about 0.3 mm is maintained between said heat-accumulating block and said insulating plate-like substrate.
claim 12
14. A heat-accumulating block used in the pre-baking method of , comprising a block member having a flat heating surface, a pair of guide walls that extend in parallel along the opposing sides of the heating surface of said block member, and rail elements extending along the corners formed by said pair of guide walls and by said heating surface, the lateral width of said pair of guide walls being slightly more than the distance between the opposing side edges on one side of said insulating plate-like substrate.
claim 12
15. A heat-accumulating block according to , wherein said rail elements have a thickness of about 0.3 mm.
claim 14
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US09/726,328 US6389686B2 (en) | 1994-02-25 | 2000-12-01 | Process for fabricating a thin multi-layer circuit board |
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP6028384A JPH07235772A (en) | 1994-02-25 | 1994-02-25 | Thin-film multilayer circuit board and production therefor |
JP06-028384 | 1994-02-25 | ||
JP6-028384 | 1994-02-25 | ||
US08/359,448 US5679268A (en) | 1994-02-25 | 1994-12-20 | Thin multi-layer circuit board and process for fabricating the same |
US08/878,198 US6184476B1 (en) | 1994-02-25 | 1997-06-18 | Thin multi-layer circuit board having a remodeling pad layer and a metallic barrier layer with an exclusion zone |
US09/726,328 US6389686B2 (en) | 1994-02-25 | 2000-12-01 | Process for fabricating a thin multi-layer circuit board |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US08/878,198 Division US6184476B1 (en) | 1994-02-25 | 1997-06-18 | Thin multi-layer circuit board having a remodeling pad layer and a metallic barrier layer with an exclusion zone |
Publications (2)
Publication Number | Publication Date |
---|---|
US20010015008A1 true US20010015008A1 (en) | 2001-08-23 |
US6389686B2 US6389686B2 (en) | 2002-05-21 |
Family
ID=12247169
Family Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US08/359,448 Expired - Fee Related US5679268A (en) | 1994-02-25 | 1994-12-20 | Thin multi-layer circuit board and process for fabricating the same |
US08/878,198 Expired - Fee Related US6184476B1 (en) | 1994-02-25 | 1997-06-18 | Thin multi-layer circuit board having a remodeling pad layer and a metallic barrier layer with an exclusion zone |
US09/726,328 Expired - Fee Related US6389686B2 (en) | 1994-02-25 | 2000-12-01 | Process for fabricating a thin multi-layer circuit board |
Family Applications Before (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US08/359,448 Expired - Fee Related US5679268A (en) | 1994-02-25 | 1994-12-20 | Thin multi-layer circuit board and process for fabricating the same |
US08/878,198 Expired - Fee Related US6184476B1 (en) | 1994-02-25 | 1997-06-18 | Thin multi-layer circuit board having a remodeling pad layer and a metallic barrier layer with an exclusion zone |
Country Status (2)
Country | Link |
---|---|
US (3) | US5679268A (en) |
JP (1) | JPH07235772A (en) |
Families Citing this family (16)
Publication number | Priority date | Publication date | Assignee | Title |
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JP3297591B2 (en) * | 1996-04-17 | 2002-07-02 | シャープ株式会社 | Method for manufacturing active matrix substrate and liquid crystal display device |
US6511759B1 (en) | 2000-02-07 | 2003-01-28 | Carl Schalansky | Means and method for producing multi-element laminar structures |
JP2002043467A (en) * | 2000-07-31 | 2002-02-08 | Hitachi Chem Co Ltd | Board for semiconductor package, its manufacturing method, semiconductor package using board and manufacturing method of semiconductor package |
JP2002374098A (en) * | 2001-04-13 | 2002-12-26 | Yamaha Corp | Semiconductor package and its mounting method |
US6477034B1 (en) * | 2001-10-03 | 2002-11-05 | Intel Corporation | Interposer substrate with low inductance capacitive paths |
US7081650B2 (en) * | 2003-03-31 | 2006-07-25 | Intel Corporation | Interposer with signal and power supply through vias |
JP4515858B2 (en) * | 2004-08-18 | 2010-08-04 | ローム株式会社 | Manufacturing method of thermal print head |
JP4599132B2 (en) * | 2004-10-19 | 2010-12-15 | 富士通株式会社 | Printed circuit board manufacturing method and printed circuit board |
KR20090061723A (en) * | 2007-12-12 | 2009-06-17 | 주식회사 동부하이텍 | Method of opening pad in semiconductor device |
US8592691B2 (en) * | 2009-02-27 | 2013-11-26 | Ibiden Co., Ltd. | Printed wiring board |
JP2011039905A (en) * | 2009-08-17 | 2011-02-24 | Panasonic Corp | Information processing device |
JP6668004B2 (en) * | 2015-06-09 | 2020-03-18 | カンタツ株式会社 | Circuit pattern manufacturing apparatus, circuit pattern manufacturing method, and circuit pattern manufacturing program |
JP2017028079A (en) * | 2015-07-22 | 2017-02-02 | イビデン株式会社 | Manufacturing method of printed wiring board and printed wiring board |
JP6839476B2 (en) | 2016-09-26 | 2021-03-10 | カンタツ株式会社 | Pattern forming sheet |
JP6892727B2 (en) | 2016-09-26 | 2021-06-23 | カンタツ株式会社 | Pattern manufacturing equipment, pattern manufacturing method and pattern manufacturing program |
JP2018182126A (en) | 2017-04-17 | 2018-11-15 | カンタツ株式会社 | Pattern forming sheet, pattern manufacturing apparatus, and pattern manufacturing method |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2509912C3 (en) * | 1975-03-07 | 1979-11-29 | Robert Bosch Gmbh, 7000 Stuttgart | Electronic thin film circuit |
JP2554358B2 (en) * | 1988-05-25 | 1996-11-13 | 沖電気工業株式会社 | Wiring board and method for manufacturing wiring board |
US5459634A (en) * | 1989-05-15 | 1995-10-17 | Rogers Corporation | Area array interconnect device and method of manufacture thereof |
CA2059020C (en) * | 1991-01-09 | 1998-08-18 | Kohji Kimbara | Polyimide multilayer wiring board and method of producing same |
US5118385A (en) * | 1991-05-28 | 1992-06-02 | Microelectronics And Computer Technology Corporation | Multilayer electrical interconnect fabrication with few process steps |
CA2083072C (en) * | 1991-11-21 | 1998-02-03 | Shinichi Hasegawa | Method for manufacturing polyimide multilayer wiring substrate |
US5329695A (en) * | 1992-09-01 | 1994-07-19 | Rogers Corporation | Method of manufacturing a multilayer circuit board |
US5274912A (en) * | 1992-09-01 | 1994-01-04 | Rogers Corporation | Method of manufacturing a multilayer circuit board |
-
1994
- 1994-02-25 JP JP6028384A patent/JPH07235772A/en not_active Withdrawn
- 1994-12-20 US US08/359,448 patent/US5679268A/en not_active Expired - Fee Related
-
1997
- 1997-06-18 US US08/878,198 patent/US6184476B1/en not_active Expired - Fee Related
-
2000
- 2000-12-01 US US09/726,328 patent/US6389686B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JPH07235772A (en) | 1995-09-05 |
US6389686B2 (en) | 2002-05-21 |
US6184476B1 (en) | 2001-02-06 |
US5679268A (en) | 1997-10-21 |
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