PROCESS FOR PRODUCING PLASTIC LAMINATES WITH METAL LAMINAE, ESPECIALLY FOR PRINTED CIRCUITS

Abstract: Process for the production of plastic laminates with copper laminae on their external faces, especially for printed circuits, said laminae being obtained from a continuous band (30) passing from one face to another, by bends (32) made in one direction and the opposite one alternatively, of the various packages placed one above the other, which band (30) being connected at its two ends (36, 37) to a generator (72) of electricity acts as a set of electric resistances generating the necessary heat for producing, when adequate pressure is exerted on the packages by a cold press (60), close association among the various component parts and so forming plastic laminates.

Description: Process for producing plastic laminates with metal laminae, especially for printed circuits The invention concerns the processes for production of plastic laminates with metal laminae. Generally speaking plastic laminates consist of sheets formed of several layers of plastic materials, associa¬ ted together in a stable manner,usual1y by pressing, on a base of paper, fabrics, fibreglass or other materials. The plastic materials may be of phenol, elami ' ne, 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 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 the 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-pla e press that provides heat and pressure simultaneously. When each heat cycle, in which a temperature of I90°C 2 may be reached at pressures of up to 100 kg/cm , lasting over 100 minutes and including a cooling stage down to 70-80°C, has been, terminated, a compact and rigid product is obtained whose single components are closely associa- ted. Presses suited to this kind of production must necessa¬ rily be complex and will give a low output due to having many heating plates, to having to produce heat and pres¬ sure at the same time in well-defined and accurate sequen- ces, to their needing to create, hy 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 propagation of calories from the press's heating plates to the piled up packages, and of units of refrigeration during the cooling stage, is greatly hin¬ dered by having to pass- through components made of fibre- glass impregnated with plastic materials,or others equal¬ ly 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. Subject of the invention is a process for production of plastic laminates with metal laminae, especially for prin¬ ted circuits, which comprises formation of piles of pack¬ ages each one having a number of support sheets , impregnated with plastic material,and metal laminae on one or both faces . Said metal laminae are rolled off a continuous band. An initial length of band is made to match up with the lower face of the first set of sheets, starting from be¬ low. After a fold at 180° has been made a second length of band is laid on the upper face of said set and after placing there a metal sheet and making a second fold at 180°, in the opposite direction to that of the first, a third ' length is matched up with the lower face of the second set of sheets. After making a third fold at 180° in the direction op¬ posite to that of the second fold, the band is passed onto the upper face of this last set of sheets, and so on until the upper face of the last set of sheets is reached . The two ends of the band are connected to a suitably powered generator of electricity. Therefore by creating adequate pressure on the pile of packages and closing the electric circuit of the gene¬ rator, the various lengths of band matching with the faces of the packages, act as electric resistances so that close association is made among the various com¬ ponent parts of the package and plastic laminates are duly formed. The metal band is preferably a copper band. The required pressure on the pile of packages can be ob¬ tained by putting the pile inside a cold press or else in an autoclave. In accordance with a preferred method each pile of pack¬ ages is placed inside a die which has an upper and a lower plate connected by guiding and supporting pins. In this way the pressure needed can be applied in said ' die. Pressure on the die can be determined by putting it in¬ side a cold press or in an autoclave. The invention offers many advantages. As the presses do not have to provide heat and pressure simultaneously, they can be simpler, and various kinds of presses can be used able to generate ad quare pressure. Heating is generated at each single package and an even temperature can be reached within a short time. Runs of products can be either long or short. As the various copper laminae in each package can be furnished in the form of a continuous band, cooling times are also considerably reduced. Both heating and cooling are therefore more quickly done since propagation of calories or of refrigeration units is not impeded in each package by components of fibreglass or other supporting material impregnated with plastic ma¬ terials which are well known to be very poor heat conduc¬ tors, in the packages above and below as happens with processes at present in use. In the event of combined forms of heating being used- the con¬ ventional kind by heating plates at each end of the pile of packages and the direct kind through the copper bands - heating times will of course be still further reduced and productivity increased. Work cycles will be speeded up and simplified so that costs will be lowered. Characteristics and purposes of the invention will be made still clearer by the following example of its execution illustrated by diagrammatically drawn figures. Fig. 1 A present type of multi-plate press for simultaneous production of heat and pressure containing packages wherewith to make laminates for printed circuits by means of methods in use at present. Fig.2 A pile of packages formed using the process subject of the present invention. Fig.3 A pile of packages, as in Fig. 2, put in a die. Fig.4 The die in Fig. 3 placed inside a cold press. Fig.5 A pile of packages placed inside an open autoclave. Fig.6 The same as Fig. 5 but in a closed autoclave. Fig.7 Heat propagation in the pile of packages in Fig.1. Fig.8 Heat propagation in the pile of packages in Fig.2. The multi-plate press 10 has heating plates 11 between which the piles 16 of packages 12 are placed. Said packages 12 are composed of sheets 13 of fibreglass fabric impregnated with epoxy resins and the copper lami- nae 1 . Steel sheets 15 are placed between one package and another. In the pile 20 in Fig. 2 the packages 21 are composed of groups 22-24 of fibreglass sheets 25 impregnated with epoxy resin. The continuous copper band 30 winds S-wise between one group and another. Steel sheets 40-43 are inserted between packages. As illustrated, the first length 31 of band 30 is laid above the first steel sheet 40. When the group 22 of sheets 25 of fibreglass fabric has been deposited, the band makes a 180° bend 32 in order to deposit the length 33 on the upper face of the last sheet of group 22. Having placed the second steel sheet 41 on the band, said band makes another bend 34 in the direction opposite to the first one so as to match with the upper face of said steel sheet 41, and so on until the top length 35 is placed and the steel sheet 43 put over it. The initial and final ends 36 and 37 are allowed to pro¬ ject outwards . The pile 20 so formed is put into a die 50 between the plates 51 and 52 connected by the two pins 53 and 54 as seen in Fig. 3 where the ends 35 and 36 are shown as pro¬ jecting further out. In Fig. 4 there is a diagram of a cold hydraulic press 60 with top and bottom plates 61 and 62 connected and guided by four columns, 63-65 at the four corners. This press is useful only to compress piled up packages. The above die 50 is placed between plates 61 and 62. The ends 36 and 37 of the band 30 are joined toconductors 70 and 71 connected to a generator 72 of electricity. On closing the electric circuit the whole band acts like an electric resistance and all its lengths, such as 31, 33, 35, give off direct heat to goups 22-24 of sheets 25 and this, added to simultaneous pressure from the press, gives rise to the pressing process. Cuts are then made at bends 32, 34 and the others between the various lengths of band 31, 33, 35 providing laminates for printed circuits simply and quickly. Fig. 5 shows a pile 80 of packages similar to the pile 20 already seen in Figs. 2-4, put inside an autoclave 90. On the bottom 82 of the autoclave there is a plate 83 co¬ vered with a conducting lamina 84. To the cover 91 of said autoclave a second plate 86 is fixed by means of elastic devices 85,and to it is fixed a plate 87 covered with a conducting lamina 88. The laminae 84 and 88 are joined to a generator 94 of electricity of suitable power by means of elastic con¬ ductors, a lower one 92 and an upper one 93. As will be seen in Fig. 6, when the lid is closed, the lamina 88 coincides with the end 96 of the metal band 95. As the other end 97 of said band matches with the lamina 84, closure of said lid determines closure of the circuit between the generator and the band, and therefore the be¬ ginning of the pressing process as previously described. Fig. 7 illustrates of one of the present presses drawn in Fig. 1 and marked 10, the lines marked 100 indicating propagation of heat,emitted by the heating plates 11, or of refrigera ion units. Fig. 8 shows the pile of packages seen in Fig. 2, and gives the lines of propagation of heat emitted by the various lengths 31, 33, 35 of the metal band 30.

Claims: C laims 1. Process for producing plastic laminates with metal la¬ minae, especially for printed circuits, by formation of piles (20,80) of packages (21 ,81) each comprising a group (22-24) of supporting sheets (25) impregnated with plastic material and with metal laminae on one or both faces, characterized in that the metal lamine are obtained from a continuous metal band(30,95) laid at the lower face of the (25) first group (22) of sheets starting from the bottom, and then,on making a bend (32) at 180°, it is laid on the up ¬ per face of said group (22) and, after a metal sheet (41). has been placed and after the band has made a second bend (34) at 180° in the direction opposite to the first, said band is placed at the lower face of the second group (23) of sheets and then, having made a third bend at 180° in • the direction opposite to the second bend, said band is laid on the upper face of this second group (23) of sheets(25) and so on until the upper face of the last group (24) of sheets has been reached, the two ends (36,37-96,97)of the.ban.--. (95) being connected to a generator (72,91)of electricity of adequate power so that by generating adequate pressure on the pile (20,80) of packages (21 ,81)and the electric circuit of the generator (72,91) having been closed, the various lengths (31) (33) (35) of the band (30,95) matching with the faces of the packages (21,P>1) act as electric resistan¬ ces creating close association among the various parts and formation of plastic laminates. 2. Process as in claim 1, characterized in that pressure on the pile (20) of packa- ges (21) is obtained by inserting said pile (20) inside a cold press (60) . 3. Process as in claim 1, characterized in that pressure on the pile (80) of pack¬ ages is determined by placing said pile (80) inside an _- autoclave (90) . 4. Process as in claim 1, characterized in that each pile (20) of packages (21) is placed first inside a die (50) with its upper (51) and lower (52) plates connected by pins (53) (54) for support and guidance, it being thus possible to apply the pressure needed for the process onto said die (50). 5. Process as in claim 1, characterized in that the pressure on the die (50) is ob¬ tained by placing it inside a cold press (60). 6. Process as in claim 4, characterized in that pressure on the die (50) is obtained by placing it inside an autoclave. 7. Process as in claim 1, characterized in that the band (30) is made of copper. 8. Process as in claims 1 * characterized in that pressure on the pile (80) of pack¬ ages is determined by placing said pile (80) inside an auto clave (90) , the pile (8.0) of packages put inside it being comprised between a plate (83) fixed to the bottom of the autoclave and a plate (87) fixed to the inside of a lid (91), there being placed on said plates (83, 87) conducting laminae (84, 88) in a position to contact the (80) lower and upper sides of the pile of packages and thus to come in contact with the two ends (96, 97) of the ser- (95)' (80) pentine-wise metal band with which the pile of packages is formed, said laminae (84, 88) being connected with a generator (94) of electricity, the plate (87) being held to the inside of the lid (91) by elastic means ( 85) so that by closing the lid (91), closure is automatically secured of the circuit between the generator (94) and the metal band (95) and therefore the start of the pres- sing process already described.

Inventors: CERASO BRUNO, CERASO, BRUNO
Applicants: CEDAL SRL, CERASO BRUNO, CEDAL, S.R.L.
Application year: 1992
Main classification: B32B31
IPC codes: B29C35, B29C43, B29C65, B29K105, B29L9, B29L31, B30B7, B30B15, B32B15, B32B37, H05K3