GB2130019A - Flexible circuit board - Google Patents
Flexible circuit board Download PDFInfo
- Publication number
- GB2130019A GB2130019A GB08302377A GB8302377A GB2130019A GB 2130019 A GB2130019 A GB 2130019A GB 08302377 A GB08302377 A GB 08302377A GB 8302377 A GB8302377 A GB 8302377A GB 2130019 A GB2130019 A GB 2130019A
- Authority
- GB
- United Kingdom
- Prior art keywords
- base sheet
- circuit board
- flexible circuit
- boundary
- flexible
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- 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
- H05K3/281—Applying non-metallic protective coatings by means of a preformed insulating foil
-
- 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
- H05K1/0277—Bendability or stretchability details
- H05K1/028—Bending or folding regions of flexible printed circuits
- H05K1/0281—Reinforcement details thereof
-
- 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
- H05K1/11—Printed elements for providing electric connections to or between printed circuits
- H05K1/118—Printed elements for providing electric connections to or between printed circuits specially for flexible printed circuits, e.g. using folded portions
-
- 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
- H05K2201/20—Details of printed circuits not provided for in H05K2201/01 - H05K2201/10
- H05K2201/2009—Reinforced areas, e.g. for a specific part of a flexible printed circuit
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Manufacturing & Machinery (AREA)
- Structure Of Printed Boards (AREA)
- Non-Metallic Protective Coatings For Printed Circuits (AREA)
Abstract
A flexible circuit board comprises a base film 1 with a circuit pattern 2 thereon, a cover film 3 over part of the circuit pattern which leaves an exposed connection portion 2A of the circuit pattern, and reinforcing elements 5 attached to or forming a part of the base film in alignment with the edge of the cover film to prevent stress concentrations which cause breaking of the circuit pattern. <IMAGE>
Description
SPECIFICATION
Flexible circuit board
This invention relates to the field of flexible circuit boards. More particularly, this invention relates to printed circuit flexible circuit boards provided with a partial cover film which leaves exposed end portions of the circuit pattern for connection to other circuits or components.
Flexible circuit boards are known in the prior art which have the basic structure of a plastic base film, a circuit pattern on the base film, and a plastic cover film which covers most, but not all of the circuit pattern, the cover film leaving exposed some of the circuit pattern so that the circuit pattern may be connected to another electrical circuit. Prior art circuit boards of this type have a stress concentration problem in that there are different bending charcteristics or different flexure strengths in the circuit board between the portion which has the cover film and the portion which does not have the cover film. The practical results of this difference in flexure or bending strengths is that a stress concentration line exists across the circuit pattern at the location of the boundary line of the cover film.This stress concentration feature is most undesirable because it may result in breaking of the circuit pattern which will, of course, destroy the effectiveness and usefulness of the circuit board.
The above-discussed and other problems of the prior art are overcome or alleviated by the flexible circuit board of the present invention. In accordance with the present invention, reinforcing structure is attached to the base sheet to dissipate or mitigate to a large extent the concentration of stresses due to bending moments or otherwise which would exist in the prior art. The reinforcing structure is in the form of protruding parts from the base sheet at the ends of the edge line defined by the junction of the cover sheet with the base sheet. These reinforcing protrusions may consist of elements integrally formed in the base sheet, or they may be elements separately formed and suitably attached to the base sheet.Since the base sheet is typically a flexible plastic material, it is particularly convenient and easy to form the base sheet with integral protrusions; or the protrusions may be added to the base sheet in a separate manufacturing step.
The above-discussed and other advantages of the present invention will be apparent to and understood by those skilled in the art from the following detailed description and drawings.
Referring now to the drawings, wherein like elements are numbered alike in the several
FIGURES:
FIGURE 1 is a top plan view of a flexible printed circuit board in accordance with the prior art.
FIGURE 2 is a top plan view of a flexible printed circuit board in accordance with the present invention.
FIGURE 3 is a side elevation view of the flexible printed circuit board of FIGURE 2.
Referring first to FIGURE 1, a flexible printed circuit board in accordance with the prior art is shown. A base sheet 1, typically of thin flexible plastic, has a series of conductors 2 thereon forming a circuit pattern. The circuit pattern may be formed by any conventional printed circuit or similar technique. A cover film 3, also typically of thin flexible plastic, covers and is bonded to the base sheet or film 1 up to a boundary line 4. End portions 2A of the conductors are left exposed to provide for interconnection portions to connect the condutors to another circuit or to circuit components.This structure shown in FIGURE 1 is conventional and well known in the art, with the cover film 3 serving to protect against unintentional and unwanted circuit connections to the conductors or to protect against short circuiting by accidential interconnection of the conductors, and also to protect against environmental hazards.
In a flexible circuit board such as shown in
FIGURE 1, the portion covered by cover film 3 and the portion having the exposed conductors 2A naturally have different flexure or bending strengths or characteristics. It is also known that structures such as shown in FIGURE 1, bending stresses are concentrated along the edge or boundary line 4. Hence, edge or boundary line 4 defines an area of stress concentration where breaking of the conductors 2 tends to occur.
Naturally, breaking of the conductors is a very serious matter, and especially so if it should occur in a device or instrument subsequent to installation of the circuit board, because operation of the device or instrument of which the circuit board forms a part may be totally interrupted or seriously impaired. All of this may lead to serious problems, especially in the field of flexible circuit boards where it is very important to have highly reliable flexible circuit board products which are free from problems of this type and which are required to undergo large numbersof flexing cycles in normal use.
Reffering now to a joint consideration of
FIGURES 2 and 3, the structure of the present invention is shown wherein reinforcing structure is incorporated into the printed circuit board to largely dissipate or mitigate the stress concentrations due to bending moments or bending stresses. The flexible circuit board shown in FIGURES 2 and 3 has the same general components 1, 2, 2A, 3 and 4 as in the prior art structure of FIGURE 1. However, in accordance with the present invention, reinforcing elements 5 form a part of lower circuit film 1 and protrude from the lower circuit film 1 at either one or both ends of boundary line 4. FIGURE 2 shows the reinforcing elements 5 protruding from base sheet 1 at both ends of line 4, and that is a preferred configuration; but the invention also contemplates structure having only one of the reinforcing elements 5.The protruding reinforcing elements 5 may be in the form of semi-circular elements as shown in FIGURE 2, or they may be in other forms or shapes such as rectangles or in other oval or arcuate shapes. The particular shape is not important, as long as the reinforcing elements 5 form part of base sheet 4 and protrude from base sheet 4 at one or both ends of boundary line 4 and
are positioned so that they overlap or extend on
both sides of boundary line 4. Reinforcing
elements 5 may be formed by any convenient shaping process, such as punching, and they may be formed as an integral part of base sheet or film
1 in the same punching or forming process in which the base sheet is formed.Alternately, the
reinforcing elements 5 may be formed as separate
members and then bonded, such as by thermosetting or pressure sensitive resin material, to the appropriate positions at the edge of base film 1. In this latter case, it is possible, and perhaps particularly convenient in some manufacturing process, to form the entire flexible circuit structure other than the reinforcing elements 5, and then at a suitable time during the manufacturing process position the reinforcing elements 5 at the appropriate locations and bond them to the base sheet 1.
Because of the presence of the reinforcing elements as an integral part of base sheet 1 (either by being formed as a part of the base sheet or being integrally bonded thereto), and because of the location of the reinforcing elements 5 whereby they straddle the ends of boundary 4, the bending stresses which would in the prior art tend to be concentrated along boundary line or edge 4 of the cover film are dissipated or mitigated, thus eliminating or significantly reducing the problem of conductor breakage because of bending stress concentrations in base film 1 along edge 4. The resulting circuit board of the present invention has the significant advantage over the prior art in that it provides at very low cost a highly reliable and improved product wherein the risk of conductor line breaking due to stress concentrations along boundary line 4 is virtually eliminated, while at the same time the basic flexible properties of the circuit board are maintained unimpaired. The invention also has the advantage of being an easily and economically implemented solution to a potentially serious problem.
While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
Claims (8)
1. A flexible circuit board having:
a base sheet with electrically conductive circuit means thereon;
a cover sheet on said base sheet covering less than all of said base sheet and leaving part of said circuit means exposed, said cover sheet having an edge portion defining a boundary beyond which the base sheet and circuit means extend; and
reinforcing means on said base sheet at at least one end of said boundary.
2. A flexible circuit board as in claim 1 wherein: said reinforcing means straddles the end of said boundary.
3. A flexible circuit board as in claim 2 wherein: said reinforcing means is an integrally formed part of said base sheet.
4. A flexible circuit board as in claim 2 wherein: said reinforcing means is bonded to said base sheet.
5. A flexible circuit board having:
a base sheet with electrically conductive circuit means thereon;
a cover sheet on said base sheet covering less than all of said base sheet and leaving part of said circuit means exposed, said cover sheet having an edge portion defining a boundary beyond which the base sheet and circuit means extend; and
reinforcing means on said base sheet at opposite ends of said boundary.
6. A flexible circuit board as in claim 5 wherein: said reinforcing means straddle the ends of said boundary.
7. A flexible circuit board as in claim 6 wherein: said reinforcing means are integrally formed parts of said base sheet.
8. A flexible circuit board as in claim 6 wherein: said reinforcing means are bonded to said base sheet.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP1226882U JPS58116271U (en) | 1982-01-30 | 1982-01-30 | flexible circuit board |
Publications (3)
Publication Number | Publication Date |
---|---|
GB8302377D0 GB8302377D0 (en) | 1983-03-02 |
GB2130019A true GB2130019A (en) | 1984-05-23 |
GB2130019B GB2130019B (en) | 1985-04-17 |
Family
ID=11800616
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB08302377A Expired GB2130019B (en) | 1982-01-30 | 1983-01-28 | Flexible circuit board |
Country Status (4)
Country | Link |
---|---|
JP (1) | JPS58116271U (en) |
DE (1) | DE3302994A1 (en) |
FR (1) | FR2520964B1 (en) |
GB (1) | GB2130019B (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4815981A (en) * | 1986-12-22 | 1989-03-28 | Teikoku Tsushin Kogyo Co., Ltd. | Flexible printed circuit board terminal structure |
US4913662A (en) * | 1989-03-06 | 1990-04-03 | Nadin Noy | Flat, flexible, cable construction and connector attached thereto |
US5005105A (en) * | 1988-05-13 | 1991-04-02 | Alps Electric Co., Ltd. | Stress-relieving flexible circuit board holder plate |
GB2300310A (en) * | 1995-04-26 | 1996-10-30 | Nec Corp | Interconnection of circuit boards using plural conductors |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3009010A (en) * | 1958-02-10 | 1961-11-14 | Sanders Associates Inc | Printed circuit harness and connector |
FR1434935A (en) * | 1963-11-04 | 1966-04-15 | Sanders Associates Inc | Inhibitor of deformation of a thermoplastic material |
US3772776A (en) * | 1969-12-03 | 1973-11-20 | Thomas & Betts Corp | Method of interconnecting memory plane boards |
JPS5232956A (en) * | 1975-09-09 | 1977-03-12 | Kubota Ltd | Extrusion molding machine |
US3997229A (en) * | 1975-09-15 | 1976-12-14 | Thomas & Betts Corporation | Flexible connecting means |
-
1982
- 1982-01-30 JP JP1226882U patent/JPS58116271U/en active Pending
-
1983
- 1983-01-28 FR FR8301325A patent/FR2520964B1/en not_active Expired
- 1983-01-28 GB GB08302377A patent/GB2130019B/en not_active Expired
- 1983-01-29 DE DE19833302994 patent/DE3302994A1/en active Granted
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4815981A (en) * | 1986-12-22 | 1989-03-28 | Teikoku Tsushin Kogyo Co., Ltd. | Flexible printed circuit board terminal structure |
US5005105A (en) * | 1988-05-13 | 1991-04-02 | Alps Electric Co., Ltd. | Stress-relieving flexible circuit board holder plate |
US4913662A (en) * | 1989-03-06 | 1990-04-03 | Nadin Noy | Flat, flexible, cable construction and connector attached thereto |
GB2300310A (en) * | 1995-04-26 | 1996-10-30 | Nec Corp | Interconnection of circuit boards using plural conductors |
US5717556A (en) * | 1995-04-26 | 1998-02-10 | Nec Corporation | Printed-wiring board having plural parallel-connected interconnections |
GB2300310B (en) * | 1995-04-26 | 1999-07-21 | Nec Corp | Printed-wiring board |
Also Published As
Publication number | Publication date |
---|---|
GB8302377D0 (en) | 1983-03-02 |
GB2130019B (en) | 1985-04-17 |
DE3302994C2 (en) | 1988-07-07 |
JPS58116271U (en) | 1983-08-08 |
FR2520964B1 (en) | 1985-07-19 |
FR2520964A1 (en) | 1983-08-05 |
DE3302994A1 (en) | 1983-08-18 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930128 |