Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
1999-10-27
2001-05-29
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Composite
Of metal
C428S461000, C428S463000, C428S901000, C174S250000, C361S748000, C156S288000, C156S308400
Reexamination Certificate
active
06238802
ABSTRACT:
TECHNICAL FIELD
The present invention relates to protection of delicate electric equipment, in particular to a laminate suitable for capsules for such equipment, and also to a method for manufacturing such laminates.
BACKGROUND OF THE INVENTION
Mechanical and electrical equipment, which is to be used in a difficult environment must often be protected thereagainst in order not to be damaged or interrupted in the its function.
In many cases enclosures are used which are type plastics. For more demanding applications laminates are used, for instance composed by several plastic materials, or by plastics and other materials such as metal sheets, in the established art. Laminates of plastics and metal have the advantage of being both non-permeable to diffusion of water vapour and of being electrically shielding. Depending on the metal layer and in particular the thickness thereof both flexible and stiff laminates can be obtained. The latter ones can also for certain material compositions be deep drawn, that provides a simple manufacturing method of boxes and lids for sealing and encapsulation.
The manufacture of plastic/metal laminates are usually performed in one of the two following manners:
1. One of the surfaces, which are to be joined, is coated with a polyurethane glue having a sticky consistency, whereafter the surfaces are pressed together in heat. The glue contains solvent, which must be removed by drying the glued materials in large, space-consuming drying machines. Moreover, an afterhardening of the glue must be made by storing the laminate for a couple of months in order for the water to diffuse into the glue for hardening it. The glue joints have a bad humidity resistance.
2. The plastics layer is extruded in the shape of a thin layer on a metal sheet path. High requirements are put on the wide slit nozzle used. Furthermore, commercially used extruders and their screws are large, which results in that a readjustment for extrusion of different materials is difficult, circumstantial and very time-consuming to perform. This is unsuitable for manufacturing laminated materials to be used in small series, when a flexible manufacturing method is required, such as is the case in making different types of capsules for example for delicate electronic circuits.
Also, plastic/metal laminates can be manufactured where the bonding to the metal layer is provided by a layer of ionomer plastics, where the bonding layer also can be the entire plastic component of the laminate, see e.g. the European patent application EP-A2 0 057 994, U.S. Pat. Nos. 5,376,446, 4,439,810, 3,725,169 and the German published patent application DE 2 233 958.
SUMMARY
The object of the present invention is to solve the above mentioned problems, which are associated with the established art.
In particular, an object of the invention is to provide a laminate suitable for protecting mechanically and shielding electrically electric and electronic components.
Another object is to provide laminates for protecting electrical components which can be manufactured at a lower cost in small series.
Another object is to provide a method for manufacturing such laminates, that can be used at a reasonable cost for electrical components used in small series.
Another object is to provide a method of protecting in a secure way delicate electrical components.
For sealing and shielding a laminate is used comprising a layer of ionomer plastics bonded to metal sheets and/or plates. The bonding is thus accomplished without addition of any adhesive agents between the plastics layer and the metal surface, and is obtained by pressing the plastics layer against a well cleaned metal surface in heat. The metals used shall be such that their surfaces are oxidized when stored in air. Thus a multi-layer laminate is provided, where one metal layer provides a good electrical shielding and an outermost metal layer provides a good mechanical strength and/or chemical resistance to corrosion. The plastics layer at the inside of a laminate bonds in the same manner directly at margins of electrical connectors made of metal.
Generally, a laminate for diffusion tight storing of objects comprises a metal layer and a polymer layer, in particular comprising a first layer of a metal, which is oxidized in air on its surface, and a second layer of an ionomer plastics material. These layers are directly bonded to each other, in particular by means of heating during compression. The temperature during the compression shall be such, that the material of the ionomer plastics layer is only half-melted or very viscous. After the compression in heat, a heat treatment at a higher temperature is advantageously conducted, at which the ionomer plastics layer is significantly more mobile than during the compression, which considerably increases the adherence between the layers of metal and of polymer. The second layer can be a surface material layer on a thermoplastics layer, in particular polythene or polypropene, which surface layer has been obtained by means of a suitable treatment of the layer of thermoplastics.
The laminate further has a third layer of a metal, which is also oxidized on its surface in air. This third layer is directly bonded to a layer of an ionomer plastics material, which can be the second layer or a surface material layer on the other side of the thermoplastics layer.
Furthermore, a fourth layer of an ionomer plastics material can be present, which is joined to the third layer, in particular so that this fourth layer is an inner layer of the laminate or so that it is a surface material layer on a base layer of thermoplastics.
The laminate is intended for sealing and encapsulation of electronic components, in particular for an electronic circuit board having electronic components mounted thereon, and then the first, outer metal layer is a mechanically strong and/or corrosion resistant metal material, such as a layer of a foil or a sheet of Ni or of steel plate. The third layer is then a metal layer having a good electrical conductivity, in particular Al or Cu. Further, the metal material layers are advantageously the kind, that are suitable for deep-drawing, so that for instance stiff capsules can be formed.
The different layers can have substantially the same thickness and for instance the different layers can have a thickness of about 50 &mgr;m.
When an extra good electrical shielding of a joint between such laminates is required, the joint can be short-circuited, for instance by means of a method that is described in the International patent application PCT/SE94/00255, which is incorporated herein by reference.
REFERENCES:
patent: 3725169 (1973-04-01), Allen et al.
patent: 4351864 (1982-09-01), Giannakidis
patent: 4439810 (1984-03-01), Shimada et al.
patent: 4629640 (1986-12-01), Akao
patent: 4788099 (1988-11-01), Fukushima
patent: 4894264 (1990-01-01), Akao
patent: 5017429 (1991-05-01), Akao
patent: 5376446 (1994-12-01), Huang
patent: 2233958 (1973-02-01), None
patent: 0 057 994 (1982-08-01), None
patent: WO94/22181 (1994-09-01), None
Burns Doane Swecker & Mathis L.L.P.
Telefonaktiebolaget LM Ericsson (publ)
Zirker Daniel
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