Electric heating – Metal heating – By arc
Reexamination Certificate
2002-01-14
2002-12-10
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06492616
ABSTRACT:
FIELD OF TECHNOLOGY
This invention relates to a laminate comprising at least one layer of resin film and at least two layers of patterned conductors. Furthermore, this invention relates to a process for laser beam machining of resin film for a wiring board and to a process for manufacturing a wiring board, particularly a rigid-flexible printed wiring board (often abbreviated to a rigid-flex wiring board) and a double-sided carrier tape from a laminate containing the laser beam-machined resin film as an insulating layer.
TECHNICAL BACKGROUND
Rigid-flex wiring boards and double-sided carrier tapes are laminates comprising at least one layer of resin film and at least two layers of patterned conductors and at least one of the layers of resin film has a specified plural number of openings.
A rigid-flex wiring board consists of a rigid part and a flex part and both ends of the flex part are integrated with the rigid part and electrically connected. In the preparation of such a wiring board, a method most often used first makes a rigid wiring board of a layered structure resembling an integration of both ends of the flex part and the rigid part and thereafter removes the part of the rigid layer which corresponds to the flex part.
The layered structure of the integrated rigid and flex parts contains at least one layer of flexible wiring board, at least one layer of rigid wiring board and at least one layer of resin film, the last one being placed between the layers of rigid and flexible wiring boards and acting as an adhesive layer. The layer of wiring board contains at least one layer of patterned conductor, that is, a circuit layer and a resin layer.
The aforementioned method is explained as an example. The flexible wiring board after formation of the circuit and coating with the coverlay is laminated to an insulating layer which has an opening in the cable portion to the rigid part or the portion corresponding to the flex part; on this insulating layer is placed the rigid wiring board which has a layer of conductor with a circuit formed thereon and has an opening or an area marked by a cut-off line for later removal in the portion corresponding to the aforementioned flex part, readily removable resin or a parting spacer is inserted in the aforementioned opening in the rigid wiring board if necessary, and the assembly is integrated by lamination under heat and pressure and then subjected to drilling of holes, plating with copper, formation of the circuit on the outer layer and so on. Thereafter, any resin or parting spacer inserted in the aforementioned opening is removed or any area marked by the cut-off line is removed to complete the preparation of a rigid-flex wiring board.
As described above, the manufacture of rigid-flex wiring boards usually requires the use, both as an interlayer adhesive sheet and as an insulating layer between the flexible and rigid wiring boards, of resin film with an opening formed in the portion where the flexible wiring board is exposed to become the flexible layer. Conventionally, a procedure such as die punching and pin punching has been used to form an opening of a specified shape at a specified spot in the resin film intended for the manufacture of a rigid-flex wiring board such as the aforementioned. There has been a demand for establishment of a process for manufacturing rigid-flex wiring boards involving the use of resin film as an interlayer adhesive layer of higher accuracy and efficiency.
In a double-sided carrier tape useful as an electronic part, wiring patterns such as inner lead are arranged on the surface of a tape-shaped insulating base material and these patterns are connected to the ground patterns on the back of the base material by means of via holes and device holes.
A via hole is a through-hole which pierces the insulator and reaches a lead and its wall is plated with copper to provide a conductive path from the patterns on the surface to those on the back side. Wet etching is adopted for making via holes and is performed as follows. A copper foil is coated with a photoresist, photolithography is applied to form the desired via hole pattern, the exposed copper foil is etched and the photoresist is peeled off thereby forming a via hole pattern on the copper foil and exposing the insulator at the spot where the desired via hole is to be formed. Thereafter, using the copper foil on which the desired via hole pattern has been formed as an etching mask, the base material is immersed in a strongly alkaline solution to etch the entire exposed portion of the insulator and remove it completely to form a through-hole.
However, a trend toward higher density of wiring patterns in recent years has necessarily created the same trend toward higher density of via holes and there has been a demand for establishment of a process for manufacturing double-sided carrier tapes involving the use of resin film as an insulating layer of higher accuracy and efficiency.
The pulsed carbon dioxide gas laser beam is known to be applicable to drilling of holes in resin film constituting a wiring board or a carrier tape [J. Phys. D: Appl. Phy. 30 (1997) L19 and elsewhere]. However, the pulsed laser beam needs to be applied without a break in case the object to be machined extends continuously beyond the irradiation range of one pulse of the pulsed laser beam, for example, in case a slender continuous area is drilled to form openings; this means that irradiation with plural pulses takes a long time or removal of resin occupying a continuous wide area takes a long time and, in consequence, it is difficult to drill holes in the resin efficiently. Concretely, this difficulty rises in the cases where the resin to be removed occupies an area of more than 0.2 cm
2
which is the standard irradiation range per pulse of the pulsed laser beam.
An object of this invention is to provide a highly efficient and accurate process for laser beam machining of resin film to be used in laminates such as wiring boards and carrier tapes. Another object is to provide a highly efficient and accurate process for manufacturing rigid-flex wiring boards. Still another object is to provide a highly efficient and accurate process for manufacturing double-sided carrier tapes.
DISCLOSURE OF THE INVENTION
The present inventors have conducted intensive studies, arrived at the following findings which can solve the aforementioned problems, and completed this invention; a continuous-wave laser beam which is scanned with regularity in one or two ways can machine the resin with the product quality equal to or higher than that obtainable by a pulsed laser beam due to the annealing effect characteristic of a continuous-wave laser beam, realize a high average output at the same time thereby making it possible to form an opening in the resin at high speed and, in addition, remove resin occupying an area of 0.2 cm
2
or more, which has been difficult to do by the conventional technique of laser beam machining.
In a laminate comprising at least one layer of resin film and at least two layers of patterned conductors, this invention relates to a laminate wherein openings are formed in at least one of the layers of resin film by irradiating the resin film with a continuous-wave laser beam which is scanned in one or two ways while moving the resin film nearly at a right angle to the scanning direction of the laser beam with the use of a continuous-wave carbon dioxide gas laser beam machine equipped with a device for scanning the laser beam in one or two ways and a worktable capable of moving the resin film nearly at a right angle to the scanning direction of the laser beam.
Moreover, this invention relates to a process for laser beam machining of resin film for a wiring board or to a process for manufacturing resin film for a multilayer wiring board which comprises forming openings in the resin film by irradiating the resin film with a continuous-wave laser beam which is scanned in one or two ways while moving the resin film nearly at a right angle to the scanning direction of the laser beam with t
Ii Masakazu
Kohno Mitsuru
Tanaka Takashi
Yoshizawa Keiji
Birch & Stewart Kolasch & Birch, LLP
Dunn Tom
Johnson Jonathan
Nippon Steel Chemical Co. Ltd.
LandOfFree
Processes for laser beam machining of resin film for wiring... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Processes for laser beam machining of resin film for wiring..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Processes for laser beam machining of resin film for wiring... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2986671