United States Patent 19
`Sera et al.
`
`[54] FLEXIBLE WIRING BOARD AND ITS
`FABRICATION METHOD
`
`[75]
`
`Inventors: Naoki Sera, Tsuyama; Toshiharu
`Fukui, Nara; Kouji Tanabe, Katano;
`Futoshi Matsui, Tsuyama,all of Japan
`
`[73] Assignee: Matsushita Electric Industrial Co.,
`Ltd., Osaka, Japan
`
`[21] Appl. No.: 815,993
`
`{22] Filed:
`
`Mar. 10, 1997
`
`Related U.S. Application Data
`
`[60] Continuation of Ser. No. 463,988, Jun. 5, 1995, abandoned,
`which is a division of Ser. No. 132,036, Oct. 5, 1993, Pat.
`No. 5,461,202.
`
`[30]
`
`Foreign Application Priority Data
`
`Oct. 5, 1992
`Nov. 30, 1992
`
`[TP]
`[IP]
`
`Japan wessccssssseseccsnsessarsesenvesenss 4-265993
`Japan w..ccsscsssssssessscessersovens 4-320230
`
`Vint. Choceccccccccssccsssnnacsarssnnsesecsesescesssecseeens BOSD 5/12
`CST]
` [52] U.S. Cl.........
`427/96; 427/98; 427/405
`[58] Field of Search... 427/96, 98, 282,
`427/304, 383.1, 402, 405
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`UC
`
`US005733598A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,733,598
`Mar. 31, 1998
`
`.........cscssescccseeseen 427/98
`
`4,411,980 10/1983 Haney et al.
`4,559,357 12/1985 Matsumoto.
`4,569,902
`2/1986 Saito ccecssscossasvssseersssesssersssssessanee 427/98
`4,670,351
`6/1987 Keane et all. scssscssssesssarssssesersoee 427/98
`wae 427/98
`4,734,156
`3/1988 Iwasa ween
`
`6/1988 Takada etal. wessscsssssssssssenseereene 427/98
`4,752,555
`4,898,648
`2/1990 Cusamio ...csssccsssssscsssecesssesseeseseeses 427/98
`5,132,772
`7/1992 Fetty .
`5,235,139
`8/1993 Bengstonet al. .
`5,294,755
`3/1994 Kawakami et al.
`5,360,946
`11/1994 Fegeret al. .
`
`.
`
`Primary Examiner—Michael Lusignan
`Assistant Examiner—Brian K. Talbot
`
`Attorney, Agent, or Firm—Ratner & Prestia
`
`{57]
`
`ABSTRACT
`
`A flexible wiring board includesa printed conductivecircuit
`layer formed on an insulating film, a metallic layer formed
`on the printed conductive circuit layer, and an insulating
`layer formed on the metallic layer. A method of making a
`flexible wiring board includes the steps of forming a con-
`ductive circuit layer by screen printing a wiring pattern
`using a conductive paste, baking the printed wiring pattern,
`and forming a metallic layer on the printed conductive
`circuit layer by a plating method.
`
`4,182,781
`
`1/1980 Hooper etal...ecsesssnenseansees 427/98
`
`13 Claims, 10 Drawing Sheets
`
`
`
`1
`
`APPLE 1027
`Apple v. Koss
`IPR2021-00381
`
`APPLE 1027
`Apple v. Koss
`IPR2021-00381
`
`1
`
`

`

`US. Patent
`
`Mar. 31, 1998
`
`Sheet 1 of 10
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`Mar. 31, 1998
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`Mar. 31, 1998
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`U.S. Patent
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`Mar. 31, 1998
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`Mar. 31, 1998
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`Mar.31, 1998
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`U.S. Patent
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`Mar. 31, 1998
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`Mar. 31, 1998
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`5,733,598
`
`1
`FLEXIBLE WIRING BOARD AND ITS
`FABRICATION METHOD
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application is a continuation of application Ser. No.
`08/463,988 filed Jun. 5, 1995 now abandoned, which is a
`division of application Ser. No. 08/132,036, filed Oct. 5,
`1993 now U.S. Pat. No. 5,461,202.
`
`BACKGROUND OF THE INVENTION
`
`Thepresent inventionrelates to a flexible wiring boardfor
`use in operating panels of various kinds of electronic equip-
`ment and its fabrication method.
`
`One method of the prior art flexible wiring board fabri-
`cation is removing unnecessary portions of copper foil by
`etching from a flexible board on which copperfoil is pasted,
`and leaving circuit portions of the copper foil to form a
`conductive circuit.
`
`Another method of the prior art flexible wiring board
`fabrication is by printing a circuit pattern on a flexible board
`with use of a conductive paste which was prepared by
`dispersing conductive powders such as a silver powder or
`the like into resin varnish and baking the printed pattern to
`complete a conductive circuit layer.
`However,in the case of the flexible wiring board that uses
`copper foil, the disposition of the waste solution released
`from a etching process is costly and the environmental
`contamination problems caused by disposing harmful waster
`solution tend to become serious. Besides, the copper foil
`raises a question of insufficient durability against bending
`strains.
`
`In the case of the flexible wiring board that uses a
`conductive paste to form a printed conductive circuit, there
`are questionsof high resistance of the circuit pattern, inferior
`quality of the circuit, and poor solderability of the printed
`conductive circuit.
`
`SUMMARY OF THE INVENTION
`
`The present invention is intended for solving the afore-
`mentioned problems, and its object is to provide a flexible
`wiring board characterized by low resistance wiring circuits,
`good soiderability, excellent durability against bending
`strains, or the like.
`In addition to the foregoing, it aims at offering a method
`for fabricating flexible wiring boards, which features safety
`to the environment, low costs, or the like.
`The flexible wiring board of the present invention is
`composed of a printed conductive circuit layer formed at
`specified places on an insulating film, a metallic layer
`formed on the printed conductive circuit layer, and an
`insulating layer formed on the metallic layer.
`Also, the method for fabricating a flexible wiring board as
`disclosed by the present invention comprises the steps of
`forming wiring patterns at specified places on an insulating
`film by meansof a screen printing using a conductive paste,
`forming a conductive circuit layer by baking the conductive
`paste, forming a metallic layer on the printed conductive
`circuit layer by means of a plating method, and forming an
`insulating layer on the metallic layer at places excluding at
`least lands for soldering.
`The present invention makes it possible to bring about
`such effects as low resistance in the circuits, excellent
`conducting quality, easy soldering to the metallic layer
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`2
`formed on the printed conductive circuit layer, excellent
`durability against bending strains without causing breakage
`in the printed conductive circuit layer, no necessity of
`disposing the harmful waste solution produced from fabri-
`cation processes resulting in protection of the environment
`from contamination and reduced production costs due to
`simplified fabrication processes, or the like.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG.1(a) is a perspective view of a flexible wiring board
`as a first exemplary embodimentof the present invention.
`FIG. 1(5) is a cross-sectional view cutting across an
`important area Al of the flexible wiring board as shown in
`FIG. 1(a).
`FIG. 1(c) is a cross-sectional view cutting across an
`important area A2 of the flexible wiring board as shown in
`FIG. 1(a).
`FIG.2(a)is a cross-sectional view of an important area of
`a flexible wiring board as a second exemplary embodiment
`of the present invention.
`FIG. 2(b) is a cross-sectional view of another important
`area of the flexible wiring board as the second exemplary
`embodiment of the present invention.
`FIG. 3 is a cross-sectional view of a flexible wiring board
`as a third exemplary embodimentof the present invention.
`FIG.4 is a cross-sectional view of a flexible wiring board
`as a fourth exemplary embodimentof the present invention.
`FIG. 5(a) is a top plan view of a flexible wiring board as
`a fifth exemplary embodiment of the present invention.
`FIG. 5(b) is a cross-sectional view of a flexible wiring
`board as a fifth exemplary embodiment of the present
`invention.
`
`FIG. 6 is a cross-sectional view of a flexible wiring board
`as a sixth exemplary embodiment of the present invention.
`FIG. 7 is a cross-sectional view of a flexible wiring board
`as a seventh exemplary embodiment of the present inven-
`tion.
`
`FIG.8 is a perspective view of a flexible wiring board as
`an eighth exemplary embodiment of the present invention.
`FIG. 9 is a cross-sectional view to show an important area
`of a specific example wherein the flexible wiring board of
`the eighth exemplary embodimentofthe present invention is
`used as a connector.
`
`FIG. 10(a) is a cross-sectional view of a flexible wiring
`board as a ninth exemplary embodiment of the present
`invention.
`
`FIG. 10(2) is a top plan view of the flexible wiring board
`as the ninth exemplary embodimentof the present invention.
`FIG.11 is a cross-sectional view of a flexible wiring board
`as a tenth exemplary embodimentof the present invention.
`FIG. 12 is a cross-sectional view of a flexible wiring
`board as an eleventh exemplary embodimentof-the present
`invention.
`FIG. 13 is a cross-sectional view of a flexible wiring
`board as a twelfth exemplary embodiment of the present
`invention.
`
`FIG. 14 is a cross-sectional view of a flexible wiring
`board as a thirteenth exemplary embodiment of the present
`invention.
`
`FIG. 15 is a cross-sectional view of a flexible wiring
`board as a fourteenth exemplary embodimentofthe present
`invention.
`
`FIG. 16 is a cross-sectional view of a flexible wiring
`board as a fifteenth exemplary embodiment of the present
`invention.
`
`12
`
`12
`
`

`

`5,733,598
`
`3
`FIG. 17 is a cross-sectional view of a flexible wiring
`board as a sixteenth exemplary embodimentof the present
`invention.
`FIG. 18 is a cross-sectional view of a flexible wiring
`board as a seventeenth exemplary embodiment of the
`present invention.
`FIG. 19 showsthe fabrication process for a flexible wiring
`board as an eighteenth exemplary embodiment of the present
`invention.
`FIG. 20 showsthe fabrication process for a flexible wiring
`board as a nineteenth exemplary embodiment ofthe present
`invention.
`
`10
`
`Key to Symbol
`
`
`15
`
`4
`resin is mainly formed of polyvinyl chloride resin, urethane
`resin, epoxy resin or a modified resin thereof.
`The insulating film 1 used is polyimide, polyester,
`polyetherimide, polyether, etherketone, polysulfone,
`polyethersulfone, polyphenylene sulfide, or the like. The
`insulating layer 4 is formed by coating an insulating paste by
`means of a printed method, but it can also be formed by
`laminating insulating films. It is also possible to make a
`flexible wiring board which has the printed conductive
`circuit layer 2, the metallic layer 3, and the insulating layer
`4 disposed not only on one surface of the insulating film 1,
`butalso has them disposed sequentially on the other surface
`of the insulating film 1. It is further possible to make a
`flexible wiring board which has additionally a second
`printed conductive circuit layer, a second metallic layer, and
`a secondinsulating layer disposed sequentially on the insu-
`lating layer 4.It is still further possible to make a multiple-
`layer flexible wiring board by having more than one of a
`flexible wiring board, which has the printed conductive
`circuit layer 2, the metallic layer 3, and the insulating layer
`4 disposed on the insulating layer 1, put together one over
`the other. As the means of putting the respective flexible
`wiring boards together, an adhesive or an adhesive sheet can
`be used. It is also possible to form the metallic layer 3 by
`means of a metal deposition method or other methods of
`disposing metallic thin films in addition to the plating
`method.
`
`EXAMPLE 2
`
`FIG. 2(a) and FIG.2(6)illustrate the structure ofa flexible
`wiring board as a second exemplary embodiment of the
`presentinvention. Thedifference ofthe flexible wiring board
`as described in FIG. 2 from that of FIG. 1 is in having a
`reinforcement plate 8 disposed on the bottom surface of the
`insulating film 1. On accountof the reinforcementplate 8,
`the soldered portions and the vicinity thereof becomestron-
`ger against the strains caused by bending.A film ofpolyester
`such as polyethylene terephthalate or the like, or a plate of
`aluminum or the like is used as the reinforcement plate 8.
`
`EXAMPLE 3
`
`FIG. 3 shows the structure of a flexible wiring board as a
`third exemplary embodiment of the present invention. The
`difference from the flexible wiring board of FIG. 1 is in
`having a printed conductive circuit layer 9 used as a jumper
`disposed on the insulating layer 4. The printed conductive
`circuit layer 9 used as a jumper is formed of a conductive
`paste which has goodadhesion to the metallic layer 3 of the
`underneath circuit and is similar to the one used in Example
`1.
`
`EXAMPLE 4
`
`FIG. 4 illustrates the structure of a flexible wiring board
`as a fourth exemplary embodimentof the present invention.
`Thedifference from the flexible wiring board of FIG. 1 is in
`having no metallic layer 3 disposed along the curved por-
`tions of the flexible wiring board of FIG. 4. On accountof
`this structure, a better performance against bending strains
`can be realized when compared with the flexible wiring
`board of FIG. 1.
`the insulating layer 4 was
`According to Example 1,
`formed by means of a printing method. However,
`the
`insulating layer 4 can also be formed by laminating insu-
`lating films.
`According to Example 3, the printed conductive circuit
`layer 9 for jumper was formed by a conductive paste, but a
`
`20
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`25
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`30
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`45
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`50
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`55
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`1, 11, 21, 41, 51, 61, 71, 81
`2, 15, 22, 42, 52, 62, 72, 82
`
`3, 19, 24, 43, 73, 83
`4, 16, 23, 25, 44, 53, 63, 74, 84
`12
`28, 37
`47
`
`Insulating Film
`Printed Conductive
`Circuit Layer
`Metallic Layer
`Insulating Layer
`Copper Conductor
`Reinforcement Plate
`Printed Conductive
`Layer for Shielding
`Printed Adhesive Layer
`Printed Release Agent
`Layer
`Soft Reinforcement
`Material Layer
`Hard Reinforcement
`Material Layer
`Material Layer Through
`35
`Hole
`
`
`34
`55
`
`64a
`
`64b
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`With the help of examples,
`explained in detail.
`
`the present
`
`invention is
`
`EXAMPLE1
`
`A flexible wiring board is described as a first exemplary
`embodiment of the present invention with the help of FIG.
`1(a) through FIG. 1(c). In FIG. 1(a) to FIG. 1(c), a printed
`conductive circuit layer 2 and a circuit pattern are disposed
`on one principal surface of an insulating film 1 by means of
`a screen printing method or the like. A metallic layer 3 is
`formedonthe printed conductive circuit layer 2 by means of
`a plating method. An insulating layer 4 is disposed on the
`metallic layer 3 except it is not disposed on lands for
`soldering 5a. Solder 5 serves as a connecting meansto join
`a chip component 6 and. a leaded component7 to the lands
`for soldering 5a formed of the metallic layer 3.
`In addition, the insulating layer 4 can also be disposed on
`the surface of the insulating film 1 where no metallic layer
`4 is disposed as well as on metallic layer 3.
`The printed conductive circuit layer 2 is formed by means
`of a printed method using a conductive paste which is
`prepared by dispersing conductive powdersof silver, copper
`palladium, or the like into resin or the like which has good
`adhesion to the insulating film 1, and then baking the
`conductive paste. The resin used is polyester resin, epoxy
`resin, urethane resin or a modified resin thereof.
`The metallic layer 3 is formed of copper, solder, nickel,
`gold, or the like disposed on the printed conductive circuit
`layer 2 by means of electroplating or electroless plating. The
`insulating layer 4 is formed mainly of a resin which has
`flexibility and good adhesion to the insulating film 1. Such
`
`13
`
`13
`
`

`

`5,733,598
`
`5
`metallic layer can also be disposed over the printed conduc-
`tive circuit layer 9 by meansof a plating method.
`As described in the foregoing,the flexible wiring boards
`of Example 1 through Example 4 have a structure including
`a printed conductive circuit layer 2, which excels in adhe-
`sion and flexibility, disposed on an insulating film 1, a
`metallic layer 3 disposed on the printed conductive circuit
`layer 2 by means of a plating method, and a flexible
`insulating layer 4 disposed on the surface of the metallic
`layer 3 except for the soldering lands 5¢ at a minimum.
`Onaccount of the foregoing structure, such features have
`better flexibility than that of the conductive circuit layer
`formed by means of a prior art etching method, good
`solderability due to the metallic layer 3, and circuit resis-
`tance as low as that of the conductive circuits formed by
`means of an etching method can be realized. Besides, there
`is a benefit in realizing a low cost and making an excellent
`flexible wiring board by more simplified fabrication pro-
`cesses and by more effective utilization of resources when
`compared with the etching method.
`Next, with the help of FIG. 5(a) through FIG. 20, the
`exemplary applications of the foregoing flexible wiring
`boardsof the present invention will be explained as Example
`5 to Example 19.
`
`EXAMPLE5
`
`FIG. 5(a) and FIG. 5(2) show the structure of a flexible
`wiring boardas a fifth exemplary embodimentofthe present
`invention. As illustrated in the drawings, a printed conduc-
`tive circuit layer 15 is disposed by patterning on an insu-
`lating film 11 by means of a screen printing method or the
`like. A metallic layer 19 is disposed on the printed conduc-
`tive circuit layer 15 by means of a plating method. An
`insulating layer 16 is disposed on the surface of the metallic
`layer 19 except for the connecting area by a printing method.
`A soldering area 14 formed on a copper conductor 12, which
`was formed by an etching method and covered with an
`insulating film 13 except for soldering area 14,
`is for
`connection with the copper conductor 12 by soldering.
`Polyimideresin or the like having high thermal resistance
`is used as the insulating film 13. A copper clad polyimide
`board, wherein the polyimide insulating film and the copper
`conductor 12 are put together by lamination, is used as the
`aforementioned copper conductor 12 covered with the insu-
`lating film 13.
`Further, the printed conductive circuit layer 15 is formed
`of a conductive paste which is prepared by dispersing
`conductive powders of silver, copper, palladium or the like
`into a resin or the like that shows good adhesion to the
`insulating film 11. The resin is polyester resin, epoxy resin,
`urethane resin or a modified resin thereof. The metallic layer
`19 is formed of copper, solder, nickel, gold or the like
`disposed on the printed conductive circuit layer 15 by means
`of electroplating or electroless plating. The insulating layer
`16 is mainly formed from a flexible resin such as polyvinyl
`chloride resin, urethane resin or epoxy resin, or a modified
`resin thereof which have good adhesion to the insulating
`film 1i. The insulating film 11 used is polyimide, polyester,
`polyetherimide, polyetheretherketone, etherketone,
`polysulfone, polyethersulfone, polyphenylene sulfide or the
`like.
`
`EXAMPLE6
`
`FIG. 6 showsthe structure of a flexible wiring board as a
`sixth exemplary embodiment of the present invention. What
`
`6
`differs in the present example from Example 5 shown in
`FIG.5(a) and FIG. 5(8) is explained below. A metallic layer
`19a is formed onlyat the connecting area, where a soldering
`area 14 is located, for securing durability against bending
`strains.
`
`In the foregoing Example 5 and Example 6, the copper
`clad polyimide board formed of the copper conductor 12 is
`connected with the flexible wiring board of the present
`invention. The copper clad polyimide board having high
`thermal resistance facilitates is connected with component
`parts by soldering, and the connecting areas at both sides
`being metallic make it possible to connect by reliable
`soldering. This results in enhanced connecting reliability
`and also elimination of steps such as heat sealing or the like.
`The metallic layer 9 formed on the printed conductive circuit
`layer 15 by means of a plating method contributes to a
`reduction of wiring resistance. Additionally, the copper clad
`polyimide board is required to be used only at limited places
`with resultant contributionto realization of low cost and yet
`excellent flexible wiring boards.
`
`EXAMPLE 7
`
`FIG.7 illustrates the structure of a flexible wiring board
`as a seventh exemplary embodiment of the present inven-
`tion. In FIG. 7, a printed conductive circuit layer 22 is
`disposed on the insulating film 21. A first insulating layer 21
`is formed selectively on the printed conductive circuit layer
`22 and also on the surface of the insulating film 21 where
`conductive circuits are not formed. A metallic layer 24 is
`disposed on the printed conductive circuit layer 22. A second.
`insulating layer is provided. A second printed conductive
`circuit layer 26 is disposed on the printed conductive circuit
`layer 22 and metallic layer 24. Another insulating layer 27
`is provided. A reinforcement plate 28 is joined by adhesion
`with the insulating film 21.
`More specific aspects of Example 7 are explained here.
`The printed conductive circuit layer 22 is prepared by screen
`printing a specified pattern with use of a conductive paste
`(DX-121H made by TOYOBO) onan insulating film 21
`formedof polyesterfilm 75 jm thick, and then by baking at
`150° C. for 30 minutes. The insulating layer 23 is disposed.
`by screen printing with use of an insulating resist paste
`(FC-30G made by SHIKOKIKA-SED), and then by baking at
`150° C. for 30 minutes. The metallic layer 24 formed of
`copper of 15 um thick and solder of 5 pm thick, is disposed
`by means of electroplating. Then, a different printed con-
`ductive circuit layer 26 is formed by screen printing in the
`same way as the printed conductive circuit layer 22 was
`formed, and then another different insulating layer 27 is
`formed by screen printing in the same way asthe insulating
`layer 23 was formed to complete a multi-layer wiring
`structure. The reinforcement plate 28 is an aluminum sheet
`1 mm thick.
`
`In addition, the conductive paste for the printed conduc-
`tive circuit layer 22 can be selected from the conductive
`pastes which were prepared by dispersing conductive pow-
`ders of metals such as silver, copper, palladium or the like
`into resins such as polyester, epoxy, urethane or the modi-
`fication thereof, all having good adhesion to the insulating
`film 1. The metallic layer 24 can be formed of a metal
`selected from copper, solder, nickel, gold, or the like and
`disposed on the printed conductive circuit layer 22 by means
`of electroplating or electroless plating. The insulating layers
`23, 25 and 27 can be selected from materials which are
`flexible and mainly formed of rubber resin, vinyl resin,
`urethane resin, epoxy resin or a modified or mixed resin
`
`10
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`15
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`20
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`25
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`14
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`5,733,598
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`7
`thereof, all having good adhesionto the insulating film 21.
`The material for the insulting film 21 can be polymide,
`polyester, polyetherimide, polyether-etherketone,
`polysulfone, polyethersulfone, polyphenylenesulfide, or the
`like.
`The foregoing flexible wiring board as explained in
`Example 7 is characterized by disposing the printed con-
`ductive circuit
`layer 22, which excels in adhesion and
`flexibility, on the insulating film 21, forming the flexible
`insulating Jayer 23 on the area (area B) of the printed
`conductive circuit layer 22, where good durability against
`bendingstrains is required, disposing the metallic layer 24
`on the printed conductive circuit layer 22 by means of
`plating, and forming the flexible insulting layer 25 on the
`surface of the metallic layer 24 except for the connecting
`area of the soldering land.
`Accordingly, the conductivecircuit layer has better flex-
`ibility than the one formed by the prior art etching method,
`andsoldering to the metallic layer 24 is made possible. Also,
`low wiring resistance almost equal to the resistance of the
`conductive circuit formed by etching can be realized.
`Further, a low cost and yet excellent flexible wiring board,
`which can benefit from simpler processes and better utili-
`zation of resources when compared with using the etching
`method, can be realized.
`EXAMPLE8
`
`FIG.8 illustrates the structure of a flexible wiring board
`as an eighth exemplary embodiment of the present inven-
`tion. In FIG.8, a printed conductive circuit 34 is disposed on
`the insulating film 33, a metallic layer 32 is formed on the
`printed conductive circuit 34, an insulting layer 35 is
`provided, and a reinforcementplate 37 is held by squeezing
`between surfaces of the bent insulating film 33. The printed
`conductive circuit layer 34 is formed by patterning on the
`insulating film 33 by means of a screen printing method or
`the like, the metallic layer 32 is disposed on the printed
`conductive circuit layer 34 by plating, and the insulating
`layer 35 is formed on areas except for a connecting terminal
`C. The reinforcement plate 37 is disposed in the space
`formed by bending the insulating film 33 to reinforce the
`connecting terminal C.
`In addition, the printed conductive circuit layer 34 is
`formed of a conductive paste which was prepared by dis-
`persing conductive powders metals such as silver, copper,
`palladium or the like into resins such as polyester, epoxy,
`urethane or the modification thereof, all having good adhe-
`sion to the insulting film 33. The metallic layer 32 is formed
`of a metal selected from copper, solder, nickel, gold, or the
`like and disposed on the printed conductive circuit layer 34
`by electroplating or electroless plating. The insulating layer
`35 is mainly formed of materials which are flexible and have
`good adhesionto the insulating film 33, such as vinyl resin,
`urethaneresin, epoxy resin or a modified resin thereof. The
`materials for the insulating film 33 are polyimide, polyester,
`polyetherimide, polyether-etherketone, polysulfone,
`polyethersulfone, polyphenylenesulfide, or the like. The
`reinforcement plate is a polyester film, a phenol laminated
`board,a glass epoxy laminated board, an aluminumplate, or
`the like.
`FIG.9 showsa specific example wherein the terminal end
`of the flexible wiring board illustrated in FIG. 8 is used as
`a connecting means, and shows how the terminal end of the
`flexible wiring board can be soldered to a land 39 of a
`printed circuit board 38 by solder 40.
`EXAMPLE 9
`
`A ninth exemplary embodimentof the present invention is
`explained with the help of FIG. 10(a) and FIG. 10(6). The
`
`8
`explanation is made only on the points where Example 9
`differs from Example 8. Item 37a is a reinforcementplate
`formed of a solderable metal such a aluminum,orthelike,
`and the reinforcement plate 37a is also soldered to the land
`39 ofthe printedcircuit board 38 by the solder 40 to enhance
`the connecting strength.
`Thus,
`the flexible wiring boards of Example 8 and
`Example 9 described in the foregoing have a structure
`wherein the reinforcement plate 37a is held by the bent
`connecting terminal C which makes it possible to provide a
`flexible wiring board which can be easily mounted on a
`printed circuit board.
`
`EXAMPLE 10
`
`A tenth exemplary embodimentof the present invention is
`explained with the help of FIG. 11. In FIG. 11, a printed
`conductive layer 47 for shielding is disposed on a insulating
`film 41 by means of screen printing or the like, and an
`insulating layer 44 is further disposed on the printed con-
`ductive layer 47 with another printed conductive circuit
`layer 42 formed bypatterning on the insulating layer 44 by
`meansof a screen printing method orthe like. Item 43is a
`metallic layer disposed on the printed conductive circuit
`layer 42 by meansofplating, and furtherthe insulating layer
`44 is disposed on the areas surrounding the soldering land
`situated on the metallic layer 42. A soldered area 45 fixes a
`componentpart 46 by soldering to the Jand formed of metal.
`In addition, the printed conductive circuit layer 42 and the
`printed conductive circuit layer 47 for shielding are formed
`of a conductive paste which was prepared by dispersing
`conductive powders of metals such as silver, copper, pallu-
`dium or the like into resins such as polyester, epoxy,
`urethane or a modification thereof, all having good adhesion
`to the insulatingfilm 41 andinsulating layer 44. The metallic
`layer 43 is formed of a metal selected from copper, solder,
`nickel, gold, or the like and disposed on the printed con-
`ductive circuit
`layer 42 by means of electroplating or
`electroless plating.
`The insulating layer 44 is mainly formed of materials,
`which are flexible and have good adhesionto the insulating
`film 41, such as vinyl resin, urethaneresin, epoxy resin or a
`modified resin thereof.
`The insulating film 41 material is polyimide, polyester,
`polyetherimide, polyetheretherketone, polysulfone,
`polyethersulfone, polyphenylenesulfide, or the like.
`In addition, it is possible to make a flexible wiring board
`comprising a printed conductive circuit layer 42 disposed on
`one principal surface of an insulating layer 41, a metallic
`layer 43 having a soldering land formed on the printed
`conductive circuit layer 42 by meansof plating, an insulat-
`ing layer 44 disposed on the surface of the metallic layer 43
`except for the area where the soldering land is located, a
`printed conductive layer for shielding disposed on the insu-
`lating layer 44, and a secondinsulating layer formed on the
`conductive layer for shielding.
`
`EXAMPLE11
`
`FIG. 12illustrates the structure of a flexible wiring board
`as an eleventh exemplary embodiment of the present
`invention,
`Only the differences between the present example and
`Example 10 are explained below.
`The difference from foregoing Example 10 is that a
`reinforcement plate 48 is disposed on the bottom surface of
`the insulating film 41.
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`15
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`The reinforcementplate strengthens the soldered places or
`the like against bending strains. The reinforcementplate 8 is
`a polyester film such as ethylene terephthalate or the like, or
`an aluminum plate or the like.
`
`EXAMPLE12
`
`FIG.13illustrates the structure ofa flexible wiring board
`as a twelfth exemplary embodimentof the present invention.
`Only the differences between the present example and
`Example 10 are explained below.
`The difference from foregoing Example 10 is that a
`printed conductive circuit layer 48, serving as a jumper
`crosses over the metallic layer 43, disposed on the insulating
`layer 44.
`
`10
`
`15
`
`EXAMPLE13
`
`FIG.14 illustrates the structure of a flexible wiring board
`as a thirteenth exemplary embodimentof the present inven-
`tion.
`
`20
`
`Only the difference between the present example and
`Example 10 are discussed below.
`The difference from foregoing Example 10 is that a
`curved section D is formed as well as a metallic layer 43.
`Metallic layer 43, is not formed on the curved section D
`area. This construction ensures excellent durability against
`bending strains. Metallic layer 43 is formed plating.
`
`EXAMPLE 14
`
`FIG.15 illustrates the structure of a flexible wiring board
`as a fourteenth exemplary embodimentof the present inven-
`tion.
`
`The differences between the present example, and
`Example 10 is provided below.
`Thedifference from Example 10 is that a conductive layer
`47a serving as a shield is formed on a surface of the
`insulating film 41 opposite to the surface where the printed
`conductive circuit layer 42 is disposed instead of on the
`same side. An insulating film 44 is also formed on the
`conductive layer 47a.
`The conductive layer 47a may be form by plating.
`Asdescribed in Example 10 to Example 14, by having the
`conductive layer 47 or the conductive layer 47a, serving as
`a shield, it has become possible to provide a flexible wiring
`board which is low in cost and excellent in shielding effects.
`
`EXAMPLE 15
`
`A fifteenth exemplary embodiment of the present inven-
`tion is explained with the help of FIG. 16.
`layer 52 is
`In FIG. 16, a printed conductive circuit
`disposed on an insulating film 51 with a cover coat insulat-
`ing layer 53 superimposed on the printed conductive circuit
`layer 52.
`On the bottom surface of the insulating film 51 a printed
`layer of adhesive material 54 is disposed on the bottom
`surface of the insulating film 51, a printed layer of mold
`release material 55 is disposed on the printed layer of
`adhesive material 54, and a reinforcement plate 56 is
`attached by adhesion onto the printed layer of adhesive
`material 54 in the same way.
`After screen printing a specified pattern on a polyester
`insulating fi