(12) United States Patent
`Komatsubara et al.
`
`US006841737B2
`US 6,841,737 B2
`Jan. 11, 2005
`
`(10) Patent No.:
`(45) Date of Patent:
`
`(54) WIRED CIRCUIT BOARD
`(75) Inventors: Makoto Komatsubara, Osaka (JP);
`Shigenori Morita, Osaka (JP); Tadao
`Ookawa, Osaka (JP); Toshio Shintani,
`Osaka (JP)
`(73) Assignee: Nitto Denko Corporation, Osaka (JP)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`(21) Appl. No.: 10/195,392
`(22) Filed:
`Jul. 16, 2002
`(65)
`Prior Publication Data
`US 2003/0026078 A1 Feb. 6, 2003
`Foreign Application Priority Data
`(30)
`Jul. 17, 2001
`(JP) ....................................... 2001–216812
`
`(51) Int. Cl." .................................................. H05K 7/06
`(52) U.S. Cl. ....................... 174/250; 174/255; 174/257;
`174/258
`
`(58) Field of Search ................................. 361/749–751;
`174/254, 250, 255–258, 261
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`1/1973 Kilby et al. ................ 174/251
`3,711,626 A *
`5,446,245 A * 8/1995 Iwayama et al. .....
`... 174/261
`6,388,201 B2 * 5/2002 Yamato et al. ........
`... 174/255
`6,399,899 B1 * 6/2002 Ohkawa et al. ............. 174/261
`* cited by examiner
`Primary Examiner—John B. Vigushin
`(74) Attorney, Agent, or Firm—Jean C. Edwards, Esq.;
`Dickinson Wright PLLC
`(57)
`ABSTRACT
`A wired circuit board having a terminal portion formed as a
`flying lead that can provide enhanced strength of the con
`ductive pattern, both sides of which are exposed, by simple
`construction to effectively prevent disconnection of the
`conductive pattern. The wired circuit board having the
`terminal portion formed as the flying lead in which the both
`sides of the conductive pattern are exposed includes, in
`crossing areas where ends of a cover-side opening and ends
`of a base-side opening and the conductive pattern are
`crossed each other, (i) the widened portions formed in the
`conductive pattern or (ii) cover-side projections and base
`side projections formed in the cover layer and the base layer,
`respectively.
`
`7 Claims, 15 Drawing Sheets
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`18
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`(a)
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`(b)
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 1 of 15
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`US 6,841,737 B2
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 2 of 15
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`US 6,841,737 B2
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`F | G. 3
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 3 of 15
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`US 6,841,737 B2
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`F | G. 4
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 4 of 15
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`US 6,841,737 B2
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`HUTCHINSON EXHIBIT 1001
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 5 of 15
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`F | G. 9
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 6 of 15
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`US 6,841,737 B2
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 7 of 15
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`US 6,841,737 B2
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 8 of 15
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`US 6,841,737 B2
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`U.S. Patent
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`Jan. 11, 2005
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`US 6,841,737 B2
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`US. Patent
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`Jan. 11,2005
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`US. Patent
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`Jan. 11,2005
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`U.S. Patent
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`Jan. 11, 2005
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`U.S. Patent
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`Jan. 11, 2005
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`HUTCHINSON EXHIBIT 1001
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`U.S. Patent
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`Jan. 11, 2005
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`US 6,841,737 B2
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`U.S. Patent
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`Jan. 11, 2005
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`Sheet 15 of 15
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`US 6,841,737 B2
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`HUTCHINSON EXHIBIT 1001
`
`

`

`1
`WIRED CIRCUIT BOARD
`
`US 6,841,737 B2
`
`The present invention claims priority from Japanese
`Patent Application Serial No. 2001-21812 filed Jul. 17,
`2001, which is herein incorporated by reference.
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a wired circuit board and,
`more particularly, to a wired circuit board suitably used for
`a suspension board with circuit.
`2. Description of the Prior Art
`The wired circuit boards used for electronic/electric
`equipment are usually provided with terminal portions to
`connect with external connecting terminals.
`In recent years, the so-called “flying lead” in which the
`terminal portions are formed on both sides of the conductive
`pattern, rather than in only either side thereof, is in wide
`spread use in order to meet the demand for electronic/
`electric equipment to have increasingly higher density and
`reduced size. It is known, for example, in a suspension board
`with circuit used for a hard disk drive that the terminals are
`provided in the form of flying lead.
`To be more specific, the suspension board with circuit
`comprises a supporting board 1 of stainless steel foil, a base
`layer 2 of an insulating material formed on the supporting
`board 1, a conductive pattern 3 formed on the base layer 2
`in the form of a specified circuit pattern, and a cover layer
`4 of an insulating material, for covering the conductive
`pattern 3, as shown in FIG. 21. The terminal portions 5
`provided in the form of the flying lead are formed on both
`sides of the conductive pattern 3 in the following manner.
`The cover layer 4 is opened to expose a front side of the
`conductive pattern 3, while also the supporting board 1 and
`the base layer 2 are opened to expose a back side of the
`conductive pattern 3. If necessary, metal plated layers 6 are
`formed on the both sides of the thus exposed conductive
`pattern 3 by nickel/gold plating and the like.
`Thereafter, these terminal portions formed as the flying
`lead are bonded to external connecting terminals by apply
`ing supersonic vibration thereto by use of a bonding tool and
`the like.
`In this terminal portion formed as the flying lead, since the
`both sides of the conductive pattern are exposed, the super
`sonic vibration is easily transmitted to the terminals. This is
`suitable for the bonding using the supersonic vibration: on
`the other hand, this provides the disadvantage that the
`conductive pattern exposed at both sides thereof is weak in
`physical strength and is subject to stress concentration at
`edge portions of the openings in the base layer and cover
`layer, to cause easy disconnection of the conductive pattern.
`SUMMARY OF THE INVENTION
`It is the object of the invention to provide a new wired
`circuit board having a terminal portion formed as a flying
`lead in which both sides of a conductive pattern are exposed
`that can provide enhanced strength of the conductive pattern
`by simple construction to effectively prevent the occurrence
`of disconnection of the conductive pattern.
`The present invention provides a wired circuit board
`comprising a first insulating layer, a conductive pattern
`formed on the first insulating layer, a second insulating layer
`formed on the conductive pattern, and an opening, formed at
`the same position of the conductive pattern, for allowing the
`first insulating layer and the second insulating layer to open,
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`so as to form a terminal portion in which front and back sides
`of the conductive pattern are exposed, wherein at least any
`one of the first insulating layer, the second insulating layer
`and the conductive pattern has reinforcing portions for
`reinforcing the conductive pattern formed at ends of the
`opening in crossing areas where ends of the opening and the
`conductive pattern cross each other.
`Also, the present invention provides a wired circuit board
`comprising a metal supporting layer, a first insulating layer
`formed on the metal supporting layer, a conductive pattern
`formed on the first insulating layer, a second insulating layer
`formed on the conductive pattern, and an opening, formed at
`the same position of the conductive pattern, for allowing the
`metal supporting layer and the first insulating layer, and the
`second insulating layer to open, so as to form a terminal
`portion in which front and back sides of the conductive
`pattern are exposed, wherein at least any one of the first
`insulating layer, the second insulating layer and the conduc
`tive pattern has reinforcing portions for reinforcing the
`conductive pattern formed at ends of the opening in crossing
`areas where ends of the opening and the conductive pattern
`cross each other.
`In the wired circuit boards mentioned above, since at least
`any one of the first insulating layer, the second insulating
`layer and the conductive pattern has the reinforcing portions
`for reinforcing the conductive pattern formed at the ends of
`the opening in the crossing areas where the ends of the
`opening and the conductive pattern cross each other, the
`physical strength of the conductive pattern at the ends of the
`opening can be reinforced. This can produce the effect that
`for example, when the conductive pattern, both sides of
`which are exposed, is subject to stress concentration at the
`end portions of the opening in the process of bonding the
`terminal portion and the external connecting terminal by
`applying superSonic vibration of a bonding tool, the discon
`nection of the conductive pattern can be effectively
`prevented, thus providing improved bonding reliability.
`In addition, the present invention provides a wired circuit
`board comprising a first insulating layer, a conductive pat
`tern formed on the first insulating layer, a second insulating
`layer formed on the conductive pattern, and an opening,
`formed at the same position of the conductive pattern, for
`allowing the first insulating layer and the second insulating
`layer to open, so as to form a terminal portion in which front
`and back sides of the conductive pattern are exposed,
`wherein the conductive pattern has widened portions formed
`to extend in a widthwise direction substantially orthogonal
`to an extending direction of the conductive pattern in
`crossing areas where ends of the opening and the conductive
`pattern cross each other.
`Also, the present invention provides a wired circuit board
`comprising a metal supporting layer, a first insulating layer
`formed on the metal supporting layer, a conductive pattern
`formed on the first insulating layer, a second insulating layer
`formed on the conductive pattern, and an opening, formed at
`the same position of the conductive pattern, for allowing the
`metal supporting layer and the first insulating layer, and the
`second insulating layer to open, so as to form a terminal
`portion in which front and back sides of the conductive
`pattern are exposed, wherein the conductive pattern has
`widened portions formed to extend in a widthwise direction
`substantially orthogonal to an extending direction of the
`conductive pattern in crossing areas where ends of the
`opening and the conductive pattern cross each other.
`In the wired circuit boards mentioned above, since the
`conductive pattern has widened portions formed to extend in
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`3
`a widthwise direction substantially orthogonal to the extend
`ing direction of the conductive pattern in the crossing areas
`where the ends of the opening and the conductive pattern
`cross each other, the physical strength of the conductive
`pattern at the ends of the opening can be reinforced. This can
`produce the effect that for example when the conductive
`pattern both sides of which are exposed is subject to stress
`concentration at the end portions of the opening in the
`process of bonding the terminal portion and the external
`connecting terminal by applying supersonic vibration of the
`bonding tool, the disconnection of the conductive pattern
`can be effectively prevented, thus providing improved bond
`ing reliability.
`Further, the present invention provides a wired circuit
`board comprising a first insulating layer, a conductive pat
`tern formed on the first insulating layer, a second insulating
`layer formed on the conductive pattern, and an opening,
`formed at the same position of the conductive pattern, for
`allowing the first insulating layer and the second insulating
`layer to open, so as to form a terminal portion in which front
`and back sides of the conductive pattern are exposed,
`wherein the first insulating layer and/or the second insulat
`ing layer have projections projecting from ends of the
`opening onto the conductive pattern in the opening in the
`crossing areas where the ends of the opening and the
`conductive pattern cross each other.
`Also, the present invention provides a wired circuit board
`comprising a metal supporting layer, a first insulating layer
`formed on the metal supporting layer, a conductive pattern
`formed on the first insulating layer, a second insulating layer
`formed on the conductive pattern, and an opening, formed at
`the same position of the conductive pattern, for allowing the
`metal supporting layer and the first insulating layer, and the
`second insulating layer to open, so as to form a terminal
`portion in which front and back sides of the conductive
`pattern are exposed, wherein the first insulating layer and/or
`the second insulating layer have projections projecting from
`ends of the opening onto the conductive pattern in the
`opening in the crossing areas where the ends of the opening
`and the conductive pattern cross each other.
`In the wired circuit boards mentioned above, since the
`first insulating layer and/or the second insulating layer have
`projections projecting from the ends of the opening onto the
`conductive pattern in the opening in the crossing areas
`where the ends of the opening and the conductive pattern
`cross each other, the physical strength of the conductive
`pattern at the ends of the opening can be reinforced. This can
`produce the effect that for example when the conductive
`pattern both sides of which are exposed is subject to stress
`concentration at the end portions of the opening in the
`process of bonding the terminal portion and the external
`connecting terminal by applying supersonic vibration of the
`bonding tool, the disconnection of the conductive pattern
`can be effectively prevented, thus providing improved bond
`ing reliability.
`The wired circuit board of the present invention can
`provide high bonding reliability so that the wired circuit
`board can be used as the suspension board with circuit, even
`when formed as the flying lead in which both sides of the
`conductive pattern are exposed.
`BRIEF DESCRIPTION OF THE DRAWINGS
`In the drawings:
`FIG. 1 shows an embodiment of a wired circuit board
`(wherein a widened portion is formed) of the present inven
`tion: (a) is a sectional view of a principal portion of a
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`US 6,841,737 B2
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`4
`terminal portion of the wired circuit board; and (b) is a plan
`view of the terminal portion of the same.
`FIG. 2 is an enlarged plan view of FIG. 1(b).
`FIG. 3 illustrates the production processes of a wired
`circuit board shown in FIG. 1:
`(a) shows the step of forming a conductive pattern on a
`base layer;
`(b) shows the step of forming a base layer on the con
`ductive pattern;
`(c) shows the step of forming a cover-side opening on the
`cover layer at a portion thereof at which terminals are to be
`formed;
`(d) shows the step of forming a base-side opening on the
`base layer at a portion thereof at which terminals are to be
`formed; and
`(e) shows the step of forming a metal plated layer on each
`of front and back sides of the conductive pattern exposed in
`the cover-side opening and the base-side opening.
`FIG. 4 shows another embodiment of the wired circuit
`board (wherein a cover-side projection and a base-side
`projection are formed) of the present invention: (a) is a
`sectional view of a principal portion of a terminal portion of
`the wired circuit board; and (b) is a plan view of the terminal
`portion of the same.
`FIG. 5 is an enlarged view of the plan view shown in FIG.
`4(b).
`FIG. 6 is an enlarged view of the plane view of another
`embodiment shown in FIG. 4(b).
`FIG. 7 shows in section a principal portion of another
`embodiment (only the cover-side projection is formed) of
`the wired circuit board shown in FIG. 4(a).
`FIG. 8 shows in section a principal portion of still another
`embodiment (only the base-side projection is formed) of the
`wired circuit board shown in FIG. 4(a).
`FIG. 9 is a plan view of a suspension board with circuit
`presented as one embodiment of the wired circuit board of
`the present invention.
`FIG. 10 illustrates the production processes of the sus
`pension board with circuit shown in FIG. 9:
`(a) shows the step of forming a coating of a precursor of
`a photosensitive polyimide resin on a supporting board;
`(b) shows the step of exposing the coating to light through
`a photomask;
`(c) shows the step of developing the coating to form it into
`a predetermined pattern;
`(d) shows the step of curing the patterned coating to form
`the base layer,
`(e) shows the step of forming a conductive pattern on the
`base layer;
`(f) shows the step of forming a coating of a precursor of
`a photosensitive polyimide resin on the conductive pattern;
`(g) shows the step of exposing the coating to light through
`a photomask;
`(h) shows the step of developing the coating to form it into
`a predetermined pattern;
`(i) shows the step of curing the patterned coating to form
`the cover layer;
`(j) shows the step of opening the supporting board at
`portions thereof at which the external-side connecting ter
`minals are formed;
`(k) shows the step of opening the base layer at portions
`thereof at which the external-side connecting terminals are
`formed; and
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`(1) shows the step of forming a metal plated layer on each
`side of the exposed conductive pattern.
`FIG. 11 shows an embodiment of a suspension board with
`circuit shown in FIG. 9 (wherein a widened portion is
`formed) of the present invention: (a) is a sectional view of
`a principal portion of an external-side connecting terminal of
`the suspension board with circuit; and (b) is a plan view of
`the external-side connecting terminal of the same.
`FIG. 12 shows an embodiment of a suspension board with
`circuit shown in FIG. 9 (wherein a cover-side projection and
`a base-side projection are formed): (a) is a sectional view of
`a principal portion of an external-side connecting terminal of
`the suspension board with circuit; and (b) is a plan view of
`the external-side connecting terminal of the same.
`FIG. 13 shows in section a principal portion of another
`embodiment (only the cover-side projection is formed) of
`the suspension board with circuit shown in FIG. 12(a).
`FIG. 14 shows in section a principal portion of still
`another embodiment (only the base-side projection is
`formed) of the suspension board with circuit shown in FIG.
`12(a).
`FIG. 15 shows an embodiment of a suspension board with
`circuit shown in FIG. 9 (wherein the conductive pattern has
`a concave form and a widened portion is formed): (a) is a
`sectional view of a principal portion of an external-side
`connecting terminal of the suspension board with circuit;
`and (b) is a plan view of the external-side connecting
`terminal of the same.
`FIG. 16 illustrates the production processes of the sus
`pension board with circuit shown in FIG. 15:
`(a) shows the step of forming a coating of a precursor of
`a photosensitive polyimide resin on a supporting board;
`(b) shows the step of exposing the coating to light through
`a photomask;
`(c) shows the step of developing the coating to form it into
`a predetermined pattern;
`(d) shows the step of curing the patterned coating to form
`the base layer,
`(e) shows the step of forming a conductive pattern on the
`base layer;
`(f) shows the step of forming a coating of a precursor of
`a photosensitive polyimide resin on the conductive pattern;
`(g) shows the step of exposing the coating to light through
`a photomask;
`(h) shows the step of developing the coating to form it into
`a predetermined pattern;
`(i) shows the step of curing the patterned coating to form
`the cover layer;
`(j) shows the step of opening the supporting board at
`portions thereof at which the external-side connecting ter
`minals are formed;
`(k) shows the step of opening the base layer at portions
`thereof at which the external-side connecting terminals are
`formed; and
`(1) shows the step of forming a metal plated layer on each
`side of the exposed conductive pattern.
`FIG. 17 is a schematic plan view of an embodiment of a
`photomask used for exposing the coating to light in the step
`of FIG. 16(b):
`(a) shows a semi-translucent striped pattern having an
`average transmission ratio of about 50%;
`(b) shows a semi-translucent latticed pattern having an
`average transmission ratio of about 25%;
`
`5
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`(c) shows a semi-translucent circular staggered pattern
`having an average transmission ratio of about 25%; and
`(d) shows a semi-translucent circular staggered pattern
`having an average transmission ratio of about 70%.
`FIG. 18 shows an embodiment of a suspension board with
`circuit shown in FIG. 9 (wherein the conductive pattern has
`a concave form and a cover-side projection and a base-side
`projection are formed): (a) is a sectional view of a principal
`portion of an external-side connecting terminal of the sus
`pension board with circuit; and (b) is a plan view of the
`external-side connecting terminal of the same.
`FIG. 19 shows in section a principal part of another
`embodiment of a suspension board with circuit shown in
`FIG. 18(a) (wherein only the cover-side projection is
`formed).
`FIG. 20 shows in section a principal part of still another
`embodiment of a suspension board with circuit shown in
`FIG. 18(a) (wherein only the base-side projection is
`formed).
`FIG. 21 shows a conventional suspension board with
`circuit: (a) is a sectional view of a principal portion of a
`terminal of the suspension board with circuit; and (b) is a
`plan view of the terminal of the same.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Referring to FIG. 1, there is shown an embodiment of a
`wired circuit board of the present invention. FIG. 1(a) is a
`sectional view of a principal portion of a terminal portion of
`the wired circuit board; and FIG. 1(b) is a plan view of the
`terminal portion of the same. In FIG. 1(a), the wired circuit
`board 11 comprises a base layer 12 formed as a first
`insulating layer of insulating material, a conductive pattern
`13 formed on the base layer 12 in the form of a specified
`wired circuit pattern, and a cover layer 14 formed as a
`second insulating layer of insulating material on the con
`ductive pattern 13. The conductive pattern 13 is provided in
`the form of a plurality of lines of wires 13a, 13b, 13c and
`13d arrayed in parallel with each other with spaced at a
`predetermined interval, as shown in FIG. 1(b).
`The insulating materials of the base layer 12 and the cover
`layer 14 that may be used include, for example, synthetic
`resins, such as polyimide resin, acrylic resin, polyether
`nitrile resin, polyether sulfonic resin, polyethylene tereph
`thalate resin, polyethylene naphthalate resin and polyvinyl
`chloride resin. Polyimide resin is preferably used.
`The base layer 12 and the cover layer 14 usually have
`thickness of 1–30 um, or preferably 2–20 um.
`The conductive materials used for the conductive pattern
`13 include, for example, copper, nickel, gold, solder or
`alloys thereof. Copper is preferably used. The conductive
`pattern 13 usually has thickness of 2–30 um, or preferably
`5–20 um.
`This wired circuit board 11 is formed in the following
`way. First, as shown in FIG. 3(a), the conductive pattern 13
`is formed on the base layer 12 formed in a film-like form, in
`the form of the specified wired circuit pattern by a known
`patterning process, such as a subtracting process, an additive
`process and a semi-additive process. Then, as shown in FIG.
`3(b), the base layer 12 is covered with the cover layer 14 in
`a known method, for example, by adhesive bonding a
`film-like resin to the conductive pattern 13 or by applying a
`photosensitive resin to the conductive pattern 13 and then
`curing that resin.
`In the wired circuit board 11 thus formed, as shown in
`FIG. 1(a), the cover layer 14 is opened to expose a frontside
`
`HUTCHINSON EXHIBIT 1001
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`7
`of the conductive pattern 13 and also the base layer 12 is
`opened to expose a back side of the conductive pattern 13 in
`such a manner that the exposed front side of the conductive
`pattern 13 and the exposed back side of the same correspond
`in position to each other so as to expose the both sides of the
`conductive pattern 13. Then, on the both sides of the
`exposed conductive pattern 13, metal plating layers 15 are
`formed thereby forming the terminal portion 16 in the form
`of the flying lead.
`This terminal portion 16 is formed in the following
`manner. First, a cover-side opening 17 is formed in the cover
`layer 14 in a portion thereof in which the terminal portion 16
`is to be formed, in a known method, such as drilling, laser
`machining, etching and patterning of photosensitive resin, as
`shown in FIG. 3(c). Likewise, a base-side opening 18 is
`formed in the base layer 12 in a portion thereof correspond
`ing to the cover-side opening 17, in a known method, such
`as drilling, laser machining, etching and patterning of pho
`tosensitive resin, as shown in FIG. 3(d). The cover-side
`opening 17 and the base-side opening 18 are opened into a
`rectangular shape to cover all the lines of wire 13a, 13b, 13c
`and 13d.
`As shown in FIG. 3(e), the metal plating layers 15 are
`formed by plating on both sides of the conductive pattern 13
`exposed in the cover-side opening 17 and the base-side
`opening 18.
`No particular limitation is imposed on the plating method
`used for forming the metal plated layer 15. The metal plating
`layer 15 may be formed by either of electrolysis plating and
`electroless plating. Also, no particular limitation is imposed
`on the metals used for the plating. Known metals may be
`used for the plating. It is preferable that the electrolysis
`nickel plating and the electrolysis gold plating are performed
`in sequence so that a gold plated layer 20 is formed on a
`nickel plated layer 19. The nickel plated layer 19 and the
`gold plated layer 20 each have thickness of the order of 1–5
`Aum.
`The wired circuit board 11 has the terminal portion 16 in
`the form of the flying lead. In the terminal portion 16,
`widened portions 22 as reinforcing portions which extend in
`a widthwise direction substantially orthogonal to an extend
`ing direction of the conductive pattern 13 are provided in the
`conductive pattern 13 in crossing areas 21 where the ends of
`the cover-side opening 17/base-side opening 18 and the
`conductive patterns 13 cross each other, as shown in FIG.
`1(b).
`To be more specific, the widened portions 22 are formed
`in the respective lines of wire 13a, 13b, 13c and 13d at
`positions thereof which correspond to the crossing areas 21
`(two areas per each line of wire) and arranged with space
`from each other along the longitudinal direction of the lines
`of wire 13a, 13b, 13c and 13d. The widened portions 22 are
`formed in such a generally round shape as to protrude
`widthwise from the lines of wire 13a, 13b, 13c and 13d.
`As shown in FIG. 2, each widened portion 22 is arranged,
`with its generally outer half portion embedded in the cover
`layer 14/base layer 12 and its generally inner half portion
`exposed in the cover-side opening 17/base-side opening 18,
`when a maximum widthwise length 23 between the adjacent
`lines of wire is defined as a boundary between the outer half
`portion and the inner half portion. Thus, the terminals 16 are
`formed in such a dumbbell shape that the lines of wire 13a,
`13b, 13c and 13d are protruded widthwise at both ends
`thereof in the cover-side opening 17/the base-side opening
`18.
`Each widened portion 22 is so formed that the maximum
`widthwise length 23 is 1.1–4 times, or preferably 2–3 times,
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`as longer as a usual line width 24 of the lines of wire 13a,
`13b, 13c and 13d exposed outside in the cover-side opening
`17/base-side opening 18. To be more specific, a widthwise
`part of widened portion 22 at the maximum widthwise
`length 23 is 20–1,000 um in length and a lengthwise part of
`the widened portion 22 extending in a longitudinal direction
`of the lines of wire 13a, 13b, 13c and 13d is 50–500 um in
`length.
`The widened portions 22 may be formed in any shape
`other than the generally round shape, as long as they are
`shaped to protrude widthwise and have widths larger than
`the usual width. For example, the widened portion 22 may
`be formed in rectangle.
`The terminal portion 16 having this widened portion 22
`can be formed in the processes given below. The widened
`portions 22 are formed with the patterning of the wired
`circuit pattern in the process of forming the conductive
`pattern 13. Then, in the processes of FIGS. 3(c) and (d), the
`cover layer 14 and the base layer 12 are each opened so that
`the maximum widthwise length 23 of the widened portion
`22 can be within the crossing areas 21 and thereby the
`cover-side opening 17 and the base-side opening 18 are
`formed. Thereafter, in the process shown in FIG. 3(e), the
`metal plated layer 15 is formed on each side of the conduc
`tive pattern 13 exposed in the cover-side opening 17 and the
`base-side opening 18.
`In this formation of the wired circuit board 11, since the
`widened portions 22 widened in the widthwise direction of
`the conductive pattern 13 are formed in the conductive
`pattern 13 in the crossing areas 21 where the ends of the
`cover-side opening 17/the base-side opening 18 and the
`conductive pattern 13 are crossed each other, the physical
`strength of the conductive pattern 13 at the ends of the
`cover-side opening 17 and at the ends of the base-side
`opening 18 can be reinforced. This can produce the effect
`that for example when the conductive pattern 13 is subject
`to stress concentration at exposed portions thereof at ends of
`the cover-side opening 17 and base-side opening 18 in the
`process of bonding the terminal portions 16 and the external
`connecting terminals by applying supersonic vibration of a
`bonding tool, the disconnection of the conductive pattern 13
`can be effectively prevented, thus providing improved con
`nection reliability.
`In addition, the wired circuit board 11 may be formed so
`that the terminal portion 16 presented in the form of this
`flying lead can have cover-side projections 25 formed as the
`reinforcing portions and base-side projections 26 formed as
`the reinforcing portions, as shown in FIG. 4. Specifically, the
`cover-side projections 25 are formed to project from the
`ends of the cover-side opening 17 onto the conductive
`pattern 13 in the cover-side opening 17 in the cover layer 14
`in the crossing areas 21 where the ends of