Metal working – Method of mechanical manufacture – Assembling or joining
Patent
1994-11-07
1997-04-01
Bryant, David P.
Metal working
Method of mechanical manufacture
Assembling or joining
1562739, 156216, 156267, 156288, B21D 3500
Patent
active
056154704
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns the processes for production of plastic laminates with metal laminae.
Generally plastic laminates consist of sheets formed of several layers of plastic materials, assembled together in a stable manner, usually by pressing, on a base of paper, fabric, fiber glass or other materials. The plastic materials may be of phenol, melamine, epoxy, polyester, silicon, fluoride or others.
In the production of printed circuits a metal lamina, usually of copper, is made to adhere to one or both sides of a plastic laminate during the pressing process.
A pile of packages, all virtually the same, is formed; each of these comprising a number of sheets, impregnated with plastic materials, and copper laminae one of which is placed on each side of each package.
A sheet of metal, stainless steel or some other kind, is placed between each package, and the pile so formed is put inside a multiple-plate press that provides heat and pressure simultaneously.
When each heat cycle, in which a temperature of 190.degree. C. may be reached at pressures of up to 100 kg/cm.sup.2, lasting over 100 minutes and including a cooling stage down to 70.degree.-80.degree. C., has been terminated, a compact and rigid product is obtained whose single components are closely associated.
Presses suited to this kind of production must necessarily be complex and have a low output because of their many heating plates and they produce heat and pressure at the same time in well-defined and accurate sequences, according to their needs to create, by conduction, uniform temperatures throughout the various packages in the pile of which obviously only those at the top and bottom will be in contact with the heating plates.
Particularly, the conduction of heat from the press's heating plates to the plied up packages, and vice versa during the cooling -stage, is greatly hindered because of intervening components made of fiber glass impregnated with plastic materials, or others equally insulating, which are known to be very poor conductors of heat, in the packages above and below such material in the pile.
In addition to complicating the structure of the press, the presence of many heating plates slows down loading and unloading of packages, while problems are created for short runs of production, these being relatively more costly.
SUMMARY OF THE INVENTION
It is an object of the present invention provide a process for production of plastic laminates with metal laminae, especially for printed circuits, which is improved and minimizes, reduces or eliminates one or more of the above-described disadvantages.
According to the invention the process for production of plastic laminates with metal laminae, especially for printed circuits, comprises formation of piles of packages, each package consisting of a stack of prepreg sheets, i.e. a number of support sheets, impregnated with plastic material, and metal laminae on one or both faces.
The metal laminae are made from or rolled off a continuous band. An initial portion of band is made to match and contact the lower face of the first group of prepreg sheets, starting from below. After making a bend of 180.degree., a second portion of the metal band is laid on the upper face of the first group and after placing there a rigid metal flattering sheet and making a second bend of 180.degree., in the opposite direction to that of the first, a third portion is placed on the lower face of the second group of sheets.
After making a third bend of 180.degree. in the direction opposite to that of the second bend, the band is placed onto the upper face of this next group of sheets, and so on until the upper face of the last group sheets is reached.
The two ends of the band are connected to a suitably powered generator of electricity.
An adequate pressure is applied to the pile of packages and the generator is turned on so that the various lengths of band matching with the faces of the packages, which act as electric resistances are heated so that close association is made among the va
REFERENCES:
patent: 1945560 (1934-02-01), Meyercord
patent: 3592993 (1971-07-01), Bennett
patent: 3969177 (1976-07-01), Doran et al.
Japanese Patent Abstract 60-166428(A), Aug. 1985, Matsuhita Denko K.K., "Laminate Molding Method Of Metal Lined Laminated Board".
Bryant David P.
Cedal S.r.l.
Striker Michael J.
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