Metal deforming – By shot-blasting
Reexamination Certificate
2000-09-21
2003-07-01
Jones, David (Department: 3725)
Metal deforming
By shot-blasting
C451S038000, C451S075000
Reexamination Certificate
active
06584820
ABSTRACT:
FIELD OF THE INVENTION
The invention provides a method for producing a roughened matte surface on a metal press plate used in the manufacture of laminates and multi layer materials used to fabricate circuit boards and electronic assemblies. The invention also provides a metal press plate produced according to the method of the invention.
BACKGROUND OF THE INVENTION
Materials used to fabricate circuit boards include flat laminate and multilayer stock materials, which typically include several sheets of material, such as, for instance, fiberglass cloth that is impregnated with an epoxy and sandwiched between sheets of metal foil, typically copper foil. During pressing phases of laminate manufacture, metal foil is bonded by heat and pressure to a predetermined number of layers of stock material referred to as a prepreg. One or both sides of the prepreg receive metal foil by pressing the prepeg and metal foil between a pair of metal press plates in a vacuum press. A metal foiled pressed unit is produced which is subsequently etched with a polymeric photosensitive photo resist material to form electrically conductive lines in the metal foiled unit. Such conductive lines are used to create electrical circuits in surfaces of laminate materials. Small flaws and imperfections in and on surfaces of metal foils can interfere with the formation of such conductive lines and, therefore, are highly undesirable and critical to the quality and yield of laminate production.
Contaminants adhered to surfaces of metal press plates are a prime source of flaws and imperfections in metal foiled laminate surfaces, as well as small and fine scratches and burrs inherent in metal press plate surfaces. Metal press plate surface contamination and inherent imperfections impart unwanted anomalies to surfaces of metal foiled laminates, such as impressions, dents, pits and other blemishes, which interfere with circuit formation and detract from the quality of laminates produced. A single pair of metal press plates is typically used to press metal foil to several prepregs in one production run. Any contaminants and inherent surface imperfections present on the metal press plate surfaces will be transferred from one foiled laminate to another, reproducing flaws and imperfections in each subsequently pressed prepreg and essentially reducing the quality of laminates and overall manufacturing yield of a production run.
Methods to control the contamination of metal press plate surfaces include operator and clean room protocols and techniques to reduce the level of epoxy resin particles, epoxy resin dust, fibers and other contaminants produced during and as a consequence of laminate production. Airborne epoxy resin dust and hardened epoxy particles are particularly difficult to eliminate or substantially reduce from surfaces of metal press plates. Various cleaning methods involve mechanical scrubbing, rinsing and drying of metal plates using mechanical scrubbing equipment such as that manufactured by Curtin-Hebert Co., Inc. of New York and Wesero Gmbh of Germany. However, such prior art cleaning methods are ineffective in substantially removing or reducing the level of surface contaminants and have no ability to remove scratches, burrs and other surface flaws and imperfections such that the effects of metal press plate contamination on manufacturing yield are substantially mitigated. In addition, cleaning methods require considerable production downtime for preventive maintenance and cleaning, which further reduces the productivity of laminate manufacture.
Prior art metal press plates supplied to laminate manufacturers include stainless steel or aluminum press plates with surface finishes of a relatively high polish to achieve a shiny and smooth press plate surface. The logic of the electronics industries, and particularly of manufacturers of circuit boards and other electronic assemblers, is that highly polished metal press plates are necessary for production of metal foiled laminates, since surface contaminates are less likely to adhere to highly polished metal press plate surfaces, and, thus, achieve flawless metal foil surfaces. In addition, the presumption that highly polished metal press plate surfaces are easily cleaned to remove surface contaminants is also widely held throughout the electronics industries. In fact, highly polished metal press plates have been found to produce a significant level of surface anomalies in metal foiled laminate surfaces that result in reduced manufacturing yields due to lower laminate quality and significant production downtime required for metal press plate cleaning.
Therefore, it is desirable to provide a metal press plate for use in the production of laminates and multilayer materials used to fabricate circuit boards and other electronic assemblies that has a substantially reduced level of surface contamination and inherent surface imperfections and is easily cleaned such that an acceptable quality and yield in production is achieved. In addition, it is also desirable to provide a method of producing such metal press plate and reprocessing the metal press plate after use to substantially reduce the presence of surface contamination and imperfections.
SUMMARY OF THE INVENTION
The invention provides a method for producing a metal plate with a roughened matte surface, comprising steps of providing a metal plate constructed of a suitable material, such as stainless steel or aluminum, with a first planar surface, conveying the metal plate to a treatment area, conveying the metal plate at a predetermined speed and at a predetermined distance below a first delivery mechanism at the treatment area for projecting glass beads in at least one pressurized stream, projecting the pressurized stream of glass beads against the first surface as the metal plate is conveyed below the delivery mechanism, and oscillating the first delivery mechanism above the first surface at a predetermined speed for a predetermined number of oscillations to allow the pressurized stream of glass beads to substantially impinge the entire first surface of the metal plate as a first treatment.
In one version of this embodiment of the method, a second delivery system is provided for projecting glass beads in at least one pressurized stream against a second planar surface of the metal plate as the metal plate is conveyed above the second delivery mechanism at a predetermined speed and at a predetermined distance from the second delivery mechanism. The second delivery mechanism similarly oscillates below the second surface at a predetermined speed for a predetermined number of oscillations to allow the pressurized stream of glass beads to substantially impinge the entire second surface as a first treatment. In another version of this embodiment, the first and second surfaces of the metal plate may simultaneously receive the first treatment with the first and second delivery mechanisms simultaneously projecting at least one stream of pressurized glass beads against the first and second surfaces of the metal plate, respectively.
The first and second delivery mechanisms are each an array of blast nozzles or guns, well known to those skilled in the art and suitable for projecting media, which are either positioned above or below the metal plate in a linear arrangement or as a cluster of individual nozzles. The pressurized stream of glass beads is projected from individual nozzles against the first and second surfaces at a predetermined pressure and at a predetermined angle, such as, for instance, at a substantially perpendicular angle to the first and second surfaces of the metal press plate.
The method of the invention also provides a method for cleaning and reprocessing a roughened matte surface of the metal plate, similar to the method for producing the roughened matte surface, comprising steps of providing a metal plate, conveying the metal plate to a treatment area, providing a first delivery mechanism to project glass beads in at least one pressurized stream, projecting the pressurized stream of glass beads against
Benedict Scott M.
Carignan Edward
Ferman Mark
Lampron Matthew
Jones David
Mintz Levin Cohn Ferris Glovsky and Popeo P.C.
Polyclad Laminates, Inc.
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