Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-06-12
2001-09-25
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S830000, C029S846000, C174S254000, C174S259000, C156S268000, C216S017000, C216S020000
Reexamination Certificate
active
06293008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is in the field of printed circuit boards and relates to a method for producing a foil circuit board.
2. Description of Related Art
According to a foil technology such as is described in the international patent application with the publication number WO 93/26143 of the same applicants, thin circuit boards are produced from foils or films of an electrically insulating material (e.g. polyimide or epoxy resin) coated on one or both sides with e.g. copper. The production of these foil circuit boards essentially comprises producing conductors and plated through holes on a foil coated on both sides using known photographic and chemical/physical methods. A circuit board obtained in this way with an insulating foil layer and two conductor layers can be laminated on one or both sides with a further insulating foil (coated on one side with metal) with the aid of, in each case, an adhesive coating. The further insulating foil or foils are then once again provided with conductors and plated through-holes. These method steps can be repeated any number of times, so that foil circuit boards are obtained comprising a plurality of insulating foil layers and a plurality of conductor layers.
As such, insulating foil circuit boards are very thin and, particularly if they only comprise a few foil layers are also flexible. Prior to assembly the boards are normally laminated onto a rigid substrate, which leads to circuit boards that correspond, as regards thickness and format, to the normal standards.
If foil circuit boards are built up from several insulating foil layers, their flexibility very significantly decreases. In this way, even without a substrate, very thin circuit boards can be produced that have an adequate natural rigidity as compared with standard circuit boards for assembly purposes. Such circuit boards are e.g. used for multichip modules.
Electronic components and circuit boards assembled therewith are becoming increasingly smaller. Also, equipment and apparatus in which such circuit boards are installed are increasingly smaller in size as well. It would be advantageous in many cases if the circuit boards could be housed in the equipment in such a way as to save more space, i.e. if they could be adapted in an optimum manner, particularly in a flexible or bendable manner with respect to the equipment shape or at least the shape of the equipment inner space allocated thereto. However, it is still necessary for the assembly of circuit boards to prevent, by adequate rigidity of the circuit board, stresses in the connections between the electronic components and conductors on the circuit board which can be caused by circuit board deformations.
SUMMARY OF THE INVENTION
An object of the invention is to provide insulating foil circuit boards that satisfy both of the aforementioned conditions. Namely, the foil circuit boards according to the invention are flexible and bendable to enable adaptation thereof to the environment, while being rigid enough to facilitate assembly thereof.
The central idea of the invention is based on the fact that insulating foil circuit boards are zonally flexible and zonally rigid. In the flexible areas, compared with the rigid areas, one or more outer insulating foil layers are interrupted or have a reduced thickness such that a flexible area is, overall, thinner than a rigid area. Production of insulating foil circuit boards according to the invention includes an etching step, preferably a plasma etching stage, wherein at least one of the outermost insulating foil layers of the circuit board is removed in a larger surface manner at locations corresponding to desired flexible areas. This etching stage can be performed on the last laminated-on insulating foil layer or layers or can be repeated for further laminated-on insulating foil layers. The method is particularly advantageous if, in the same etching stage, the openings necessary for the plated through-holes are produced in the corresponding insulating foil layer.
This leads to insulating foil circuit boards having rigid and flexible areas. Through a corresponding design of the transition between the rigid and flexible areas this can be made quasi-continuous, which prevents an area made flexible for bending purposes from breaking at the transition to the rigid area. The thickness difference or the difference in the number of insulating foil layers between rigid and flexible areas is of a random nature and will be adapted as a function of the complexity of the electronic circuit (number of insulating foil layers in the rigid area) and the desired flexibility (number of insulating foil layers in the flexible area). The flexible area has at least one insulating foil layer and the rigid area at least two. For increasing their natural rigidity, the rigid areas can also be drawn onto a rigid substrate.
The layout of the printed circuit board according to the invention is obviously such that the rigid areas are assembled, whereas there are only interconnecting conductors in the flexible areas.
As has already been mentioned, insulating foil circuit boards with rigid and flexible areas can be used where there are difficult space conditions. However, it is also possible to equip, e.g., multichip modules with flexible marginal areas, which can then be used for connection to a rigid circuit board.
REFERENCES:
patent: 3589004 (1971-06-01), Shaheen
patent: 4931134 (1990-06-01), Hatkevitz et al.
patent: 5004639 (1991-04-01), Desai
patent: 5095628 (1992-03-01), McKenney et al.
patent: 5142448 (1992-08-01), Kober et al.
patent: 5144534 (1992-09-01), Kober
patent: 5144742 (1992-09-01), Lucas et al.
patent: 5262594 (1993-11-01), Edwin et al.
patent: 5288542 (1994-02-01), Cibulsky
patent: 5347712 (1994-09-01), Yasuda et al.
patent: 5499444 (1996-03-01), Doane, Jr. et al.
patent: 5638597 (1997-06-01), Cuttings et al.
patent: 5655291 (1997-08-01), Todd et al.
patent: 3302857 A1 (1984-08-01), None
patent: 4249026 (1993-03-01), None
patent: 534290 (1993-03-01), None
patent: 575292 (1993-12-01), None
patent: 0025225 (1979-08-01), None
patent: WO 93/26143 (0000-01-01), None
Martinelli Marco
Schmidt Walter
Chang Rick Kiltae
Dyconex Pantente AG
Rankin, Hill Porter & Clark LLP
Young Lee
LandOfFree
Method for producing foil circuit boards does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing foil circuit boards, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing foil circuit boards will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2512914