PROCESS FOR PRODUCING PLASTIC LAMINATES FROM CONTINUOUSLY FED BANDS

Abstract: Process for producing plastic laminates with metal laminae especially for printed circuits, by formation of one or more packages (51-54) arranged in piles, obtained from a multicomponent band (45) continuously fed in and, simultaneously, both from bands (30-32) of supporting material impregnated with plastic material and from one or two copper bands (33, 34)

Description: Process for producing plastic laminates from continuously fed bands The invention concerns the processes for producing plastic laminates using metal laminae. Plastic laminates usually consist of sheets formed of a number of layers of plastic materials stably associated, generally by pressing, on supports of paper, fabrics, fi- breglass or other materials. Theplastic materials used may be of phenol, melamine, epo- xy, polyester, silicon, fluoride or others. To make printed circuits a metal lamina, especially one of copper, is glued onto one or both of their sides during the pressing process. A pile is formed of packages all virtually the same, each one comprising a certain number of sheets impregnated with plastic materials and copper laminae placed one on each side of the package . A metal sheet, of stainless steel or some other type, is placed between each package, and the pile so formed is put in a mult iple- plate press which simultaneously provides heat and pressure. At the end of each heat cycle, in which a temperature of 2 190°C may be reached at pressures of up to 100 kg/cm last- ing over 100 minutes including a cooling stage to 70-80°C, a compact and rigid product is obtained the single compo¬ nents of which are closely associated together. Bearing in mind the many components needed, their nature and dimensions, formation of packages is a somewhat lengthy and complex process; this raises their cost considerably especially in production of laminates for printed circuits. Clearly the presses needed for this process are complex and of low output because of the many heating plates in them, because of the need to produce simultaneously both heat and pressure, with exact timing of these stages, and the need to create, by conduction, uniform temperatures in the various packages making up the pile of which, ob¬ viously, only those at each end of it are in contact with the heating platen The presence of many plates in the press not only compli¬ cates it structure but lengthens the time required for loading and unloading packages while preparation of short runs is made problematic because relatively more costly. Subject of the invention is a process for production of plastic laminates, aimed at simplifying and speeding up formation of packages, to enable use to be made of more compact and simpler presses and to facilitate transmission of calories during the heating stage and of refrigera ing units during cooling. The package or packages in the pile are made from a multi- component band fed in continuously and simultaneously with bands of supporting material impregnated with plastic ma ¬ terial and with one, or two, external metal bands of copper or some other suitable material. One end of the multicomponent band is laid on a flat sur- face of the machine and, after a metal sheet has been put on top of it, said band is folded at 180° and matched onto the second face of said sheet then, after another metal sheet has been placed on said band, a second fold at 180° is made in the direction opposite to the first fold and matched up with the second face of the second sheet, then after a third metal sheet has been placed, yet another fold is made at 180° in the direction opposite to the se¬ cond fold, and so on according to the number of packages it is desired to form. Each length of said multicomponent band lying between one sheet of metal and another therefore forms a package with all the components of said package in their usual order. At the end of the process the laminates obtained can of course be separated by cutting the multicomponent band between one package and another. Advantageously the heat is supplied by connecting two ends of the metal bands at the beginning and end of the package or pile of packages to a suitably high-powered generator of electricity. In this way said bands act as electric resistances. Said heating system can naturally be associated to the usual method of heating packages by means of heating plates or in some other way. In this case the packages are heated more quickly and thermal efficiency is improved. The components in the multicomponent band, the support bands impregnated with plastic material and the metal bands, can be fed in off reels or off other continuous feed methods. This invention clearly offers many advantages. Formation of packages to produce laminates is much qui¬ cker and more accurate, it being possible to mechanize the whole operation with consequent saving of time, la- bour and costs . Utilizing cold machines, presses or autoclaves is much more simple and such equipment may be of the most varied kind . Heating is applied to each single package and a uniform temperature can be quickly obtained. Continuity among the copper laminae comprised in each package by such laminae being in band form also leads to a considerable reduction in cooling times. Both heating and cooling are therefore more speedy as the spread of calories and of refrigeration units in each package is not hindered by the presence of fibreglass or other supporting materials impregnated with plastic ma¬ terial, well known to be poor conductors of heat, in the packages above and below such materialj as happens with the processes now in general use. While present methods imply adoption of large multiple-plate presses to contain running costs, with the process here described even very small machines can be used for short runs and this applies both to direct heating, package by package, and to formation of packages by a multicomponen band already prepared both with the support components and with copper laminae. In the case of combined types of heating - the convention¬ al kind through the plates at the ends of the pile of pack- ages and the direct kind through copper laminae - heating times are of course still further reduced and output there¬ by increased. Characteristics and purposes of the invention will be made even clearerby the following examples of its execution illustrated by diagrammaticaLly drawn figures. Fig. 1 Present operation of a multi-plate press for simul- taneous generation of heat and pressure with pack¬ ages to make printed circuits using present processes. Fig. 2 Packages of laminates, made by the process subject of the invention, arranged in a press. Fig. 3 Detail of the illustration in Fig. 2. Fig. 4 Packages of laminates, made by the process subject of the invention, arranged inside an autoclave. Fig. 5 How heat and cooling spread through packages of laminates made by the process subject of the in¬ vention, associated to processes in use at present. The press 10 contains heating plates 11 between which the piles 16 of packages 12 are placed. Components of said packages 12 are the sheets 13 of fibre- glass fabrics impregnated with expoxy resins and the copper laminae 14 at the ends. Steel sheets 15 are placed between one package and the next . As shown by the zigzag line 20, the calories in the heat¬ ing stage and refrigeration units in the subsequent cool¬ ing stage have to pass through the sheets 13 of fibreglass fabric which are known to be very poor heat conductors, or through other supporting materials of equal insulating properties . Efficiency is therefore very low. Fig. 2 gives a diagrammatic view of the process subject of the invention. Components of the packages to make laminates are obtained from the bands 30, 31, 32 of fibreglass fabric and from copper bands 33, 34 fed in continuously off the respec¬ tive reels 40, 41, 42 and 43 * , 44. Said bands "compacted" by the pair of rollers 25 26 form the mul i-component band 45. The end 46 of said band 45 is placed on the plate 61 of the press 60 and after laying a steel sheet 65 over it, said band 45 makes a fold 47 at 180° matching up with the second face of said sheet 65. After a second sheet 66 has been laid over it, said band makes a second fold 48 at 180° in the opposite direction to the first and then matches up with the second face of the last sheet 66. A third fold 49 is then made at 180° in the direction op ¬ posite to the the second fold, and so on until the second end 50 reaches up against the second plate 62 of the press. In this way a series of packages like51 , 52, 53, 54 is formed joined by the various folds made at 180° like 47-49. Then the lower end pairs 35, 36 of the copper bands 33,34 and the pairs at their upper ends 37, 38 are respectively connected to conductors 70, 71 of a generator 75 of electricity. On closing the electric circuit all sections of said bands comprised within said ends 35,36,37,38 act as electric resistances thus becoming heated themselves and heating the lengths of band 30-32 of fibreglass fabric placed between said copper bands 33, 34. The effect of the heat given off by said copper bands, as indicated by the short arrows 21 in Fig. 3, and of simul¬ taneous pressure generated by the press, brings about the pressing process and desired production of plastic laminates The folds at p oints 47-49 and others between the various lengths of multicomponent band 45 folded one way and the other, like a serpentine, are then cut through for quick and easy production of laminates for printed circuits. Fig. 4 shows an autoclave 80. inside which may be seen, in diagrammatic form, a complex 60 similar to that in the press 60 already illustrated in Fig. 2. In this figure, and in the next one 5, the various parts are marked with the same numbers as those used for simi¬ lar ones in Figs. 2 and 3. Here too the compound band 45 is used to produce packages like 51-53. Fig. 5 shows a process, like that described in Figs. 2 . and 3, associated to processes in use at present. The plates 85 and 86 in fact give off heat as indicated by the zigzag lines 20. The various packages, such as 51-53, are therefore sub¬ jected to two sources of heat, one from said plates 85 and 86 and one generated by the lengths of copper band 33 34 between the ends 35-36, 37-38, combining the two effects to achieve greater efficiency.

Claims: Cl a i ms 1. Process for producing plastic laminates with metal laminae, especially for printed circuits, by formation of one or more pack¬ ages (51-54) arranged in piles, each package composed of a few sheets of supporting material impregnated with plastic material and of metal laminae of copper or other suitable material, on one or both faces, the packages (51,53) having between them metal sheets (65,66) of steel or other suitable material, and by applica¬ tion, in suitable machines, such as presses (60), autoclaves (80) or some other, of pressure and heat sufficient to ensure close association among the various components, characterized in that the packages (51-54 ) in the pile are. obtained from a continuously fed multicomponent band (45) si¬ multaneously with bands (30-32) of supporting materials, im¬ pregnated with plastic material, and with one or two metal bands (33, 34) of copper or other suitable material. 2. Process as in claim 1, characterized in that one end (46) of the multicomponent band (45) is placed on a flat surface (61) of the machine (60, 80) and after a metal sheet (65) has been placed on said end, said band is folded at 180° and is matched with the second face of said sheet (65) and then, after a second metal sheet (66) has been placed upon the band (45) said band is once more folded at 180°, but in the direction opposite to that of the first fold, and is matched with the second face of the second sheet (66) then, after a third metal sheet has been laid on, it is once again folded at 180° in the direction op¬ posite to that of the second fold, and so on in accordance with the number of packages (51-54) required, since each length of said multicomponent band (45), lying serpentine-wise between one sheet and another sheet (65, 66) and consequently between one fold and another (47 - 49) , constitutes a package complete all the component parts in packages as usually made, and in their proper order, it being obviously possible, when the process has been terminated, to separate the laminates so obtained one from another by cutting the multicomponent band (45) at the point where the folds (47-49) are made. 3. Process as in claim 2, characterized in that the necessary heat is entirely or partly supplied by connecting the ends (35-36,37-38) of the metal bands (33, 34.) at the beginning and end of a pack- age or pile of packages (51-54) Co a suitably powered ge¬ nerator (75) of electricity, in which case the metal bands in the length between said ends will act as electric re¬ sistances . 4. Process as in claim 1, characterized in that the various components of the mul¬ ticomponent band (45), both the bands (30, 32) of support¬ ing material impregnated with plastic material and also the metal bands (33, 34 ), are fed in off reels (40, 44) or off other suitable continuous feeding means.

Inventors: CERASO BRUNO, CERASO, BRUNO
Applicants: CEDAL SRL, CERASO BRUNO, CEDAL S.R.L., CERASO, BRUNO
Application year: 1992
Main classification: B29C35
IPC codes: B29C43, B29C65, B29C70, B29K105, B29L31, B30B7, B32B15, B32B37, B32B38, H05K3