Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
1999-09-01
2001-10-30
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S325000, C430S258000, C430S259000
Reexamination Certificate
active
06309805
ABSTRACT:
The present invention is directed to a method of securing and processing thin film materials such as those used to form embedded electrical components of multi-layer printed circuit boards.
BACKGROUND OF THE INVENTION
There is a continuing interest in printed circuitry miniaturization. In most printed circuit boards in use, circuitry traces are printed by conventional methods, particularly photoresist techniques. Accessory components such as capacitors and resistors are frequently provided as discrete components and soldered onto the printed circuitry, either manually or robotically. These components occupy “real estate” on the printed circuit board and may be difficult or expensive to apply to the board.
Accordingly, structures have been proposed in which components such as capacitors and/or resistors are provided along with circuitry traces by circuitization procedures. Examples of such structures are found in U.S. Pat. Nos. 5,079,069, 5,155,655, 5,161,086, 5,261,153, 5,347,258, and 5,466,892, the teachings of each of which are incorporated herein by reference. Typically, a plurality of such structures are laminated together with dielectric material to form multi-layer printed circuit boards.
Embedded circuitry components including conductive traces, resistors, capacitors, and inductors, and components containing all of the above may be produced by chemically processing thin films. The term “thin film material” is meant herein to encompass single layer films, such as metal foils, as well as thin film laminates such as a laminate of two or more layers having specific electrical properties or a laminate of a support film and one or more layers of material having specific electrical properties.
Because such thin film materials have very little mechanical stability and would not by themselves survive conveyorized chemical processing, they must be supported on a rigid carrier. The thin film material may be held to the carrier by a rigid frame or by tape along its edges. Mechanical frames are labor-intensive to apply and remove. Tape has been known to come off during processing, resulting in damage to the thin film material being processed.
SUMMARY OF THE INVENTION
The invention provides a method of securing a thin film material for conveyorized processing. A rigid carrier is provided which has surface dimensions greater than that of the thin film material such that the thin film may be placed on the surface of the carrier leaving a perimeter area exposed. An adhesive is applied on the surface of the carrier in a pattern designed to adhere at least a peripheral portion of the thin film. This pattern may be along only a portion that secures the periphery of the thin film or over the entire carrier. The adhesive is selected to have greater adherence to the surface of the carrier than to the thin film and to have sufficiently low adhesion to the thin film such that the thin film may later be pealed from the adhesive pattern without damage to the thin film. The thin film is adhered to the adhesive pattern. A photoresist layer is applied over the thin film such that the photoresist layer extends over the exposed perimeter area of the carrier. The photoresist layer is exposed to patterned actinic radiation, the pattern of the actinic radiation being such that in subsequent development of the photoresist layer, a perimeter region of the photoresist remains over the perimeter region of the carrier surface and extends inward over a peripheral portion of the thin film sufficiently to secure the thin film during subsequent processing. The thin film is then chemically processed, typically as it is carried along on a conveyor. After processing, the resist remaining on the film is stripped, thereby releasing the thin film from the peripheral portion of the residual resist. The thin film is then peeled from the adhesive pattern.
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U.S. application No. 09/198,954, issue date May 1976, filing date Nov. 24, 1998.
Baxter Janet
Clarke Yvette M.
Morton International Inc.
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