Coating processes – Electrical product produced – Condenser or capacitor
Patent
1987-04-23
1988-06-07
Bueker, Richard R.
Coating processes
Electrical product produced
Condenser or capacitor
427250, 427286, 427424, 118718, 118315, 118325, B05D 512, C23C 1400
Patent
active
047495910
DESCRIPTION:
BRIEF SUMMARY
The subject of this invention is a device for making metallized plastic films with clearly defined non-metallized areas.
The metallizing of plastic films can be divided into two main branches: the metallizing of plastic films for electrical-electronic uses, mainly in condensers, and the metallizing of plastic films for flexible packaging.
In the first case, the metallized plastic film condenser is made up of two strips of film which form the condenser plates. These strips are obtained from a sheet 8, shown in FIG. 1, provided with a series of non-metallized parallel linear areas B, which extend along the whole length of the reel, and areas A where the metal is deposited.
The width of the non-metallized edges and the distance between them may vary according to the characteristics of the condenser. Normally the width 1 ranges from 0.7 mm to 10 mm, while the distance d between the strips B lies between 8.5 mm and 300 mm.
By suitably cutting said sheets at points corresponding to the areas B, the strips are obtained which are to be arranged separated from one another. This is achieved by leaving a non-metallized area, area B, on each of the plates, at corresponding zones thereof, along the entire length of the strip. An exemplary strip 9 is shown in FIG. 2.
In the case of metallized films for packaging non-metallized films are sometimes required so the content of the package can be seen. The non-metallized edges may be of any width. In this case the entire sheet in FIG. 1 is used.
In making strips for providing condenser plates, the metallized film must be produced with great care so as to obtain highly reliable electronic components.
According to a first technique, shown in FIG. 3, a masking with ring-welded tapes 16 of Kapton (registered trademark of Dupont) or Macrofol (registered trademark of Bayer), which adhere to the film and run in synchronicity therewith guided by rollers 17, is prearranged in a unit comprising a winding-off reel 10 and a winding-on reel 14 for the film 15, and a counteracting roller 12 whereon at least along a predetermined arc the film winds which is being subjected to the metal-evaporating source 18.
The advantage of non-metallized edges obtained using such an apparatus is that they always have a tollerance of about .+-.0.2 mm and a clear accurate borderline between the edge and the metal. Moreover, the film preserves its original colour and transparency. On the other hand, the tapes are subject to wear and breaking. Small aluminium particles come away therefrom and settle on the film, piercing and weakening the dielectric, which seriously damages the condenser.
In order to prevent the above-mentioned disadvantages, the use of a nozzle unit or oil evaporator is spreading, through which the heated and evaporated oil is delivered which deposits a small amount of fluid on the unmetallized film. Referring to FIG. 4, it can be seen that said oil-evaporator device 20 is positioned immediately before the evaporation source 18 for the metal to be deposited, in such a way that the film passes between the evaporator nozzle and the outer surface of the counteracting roller. Furthermore, according to the prior art, the nozzles on said oil-evaporator device are inserted into the body of the evaporator during assembly.
This method of obtaining said edge has the marked advantage that, as the tapes do not break, a greater production speed is achieved and the danger of aluminium vapours on the dielectric is completely eliminated. However, said method has some serious disadvantages: it is in fact difficult to accurately determine the size of the edge and, therefore, to calculate the condenser's effective capacitance. This is because, as can be seen in FIG. 5, the borderline between the edge B and the non-metallized area A has a transitional zone S which varies between 0.5 and 0.8 mm, as shown schematically in said FIG. 5. Moreover, under particular operating conditions of the condenser a phenomenon of metal destruction, generally aluminium, is triggered which causes said edge to be narrowed even by
REFERENCES:
patent: 4022928 (1977-05-01), Piwcyzk
Bueker Richard R.
Metalvuoto Films S.p.A.
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