WO1990000632A1

WO1990000632A1 - Metallizations and substrates obtained by vacuum evaporation of a plurality of metals from a source

Info

Publication number: WO1990000632A1
Application number: PCT/FR1989/000369
Authority: WO
Inventors: Georges Jean Clausse
Original assignee: Georges Jean Clausse
Priority date: 1988-07-12
Filing date: 1989-07-12
Publication date: 1990-01-25
Also published as: AU3871289A

Abstract

The present invention relates to a multilayer or homogeneous alloy deposition from an intimate mixture of a plurality of pulverulent metals in each source of evaporation of a vacuum installation by Joule effect. It also relates to a specific alloy deposition obtained as a function of the vaporized mixture which forms an armour against electromagnetic fields, and it also relates to substrates thus treated for the protection of living or inert materials and also relates to the device allowing to obtain by consecutive evaporations during the same vacuum cycle a predetermined thickness of the metal mixture deposition with additions of intermediary evaporated products. To this effect, the evaporation sources (4) are supplied by the pourers (13) of cups (11) filled with products to be evaporated and going and coming on rails (10) according to the selected sequence.

Description

s Metallizations and substrates obtained by vacuum evaporation of several metals from a source.

Ia present invention relates to a multilayer deposition process or homogeneous alloy from the intimate mixture of several powdered metals in each source of evaporation of a vacuum installation by Joule effect, relates to a specific deposit obtained depending on the vaporized elements which form a shield against electromagnetic fields, relates to substrates thus treated for the protection of living or inert matter and relates to the device making it possible to obtain, by consecutive evaporations during the same vacuum cycle, a determined thickness of the deposit of the metallic mixture with additions of evaporation of intermediate products.

the state of the art can be summarized by the following patents:

1200437 C23c Rhône-Poulenc 23.06.58 France

1263198 C23c Elektroschmelzwerk 26.07.60 France

1281255 C23c C22c H01c IBM 25.08.60 France

1285029 C23c G06k Thomson-Houston 28.03.61 France

1391859 C23c C03c H03k Telegr & Telephone lines 24.01.64 France

147618a C23c C03c Philips 15.04.66 France

1589125 C23c S.E.V. Marchai 04.09.68 France

1456665 C23c G11b IBM 04.08.65 France

1593416 C23c G21c EURATOM 26.11.68 France

2024258 C23c AIR Reduction Co 28.11.60 France

2024315 C23c C22c Robert Bosch 27.10.69 France

2123091 C23c C22c U.K & Northern Ireland 13.07.73 France

2383241 C23c HO11 Hitachi 08.03.78 France

0134722 C23c G03g XFROX Corp. 09.09.83 Europe

The “multilayer by joule effect” training technique is in fact already used, but using several sources of vapor in various fields for the manufacture, for example, of integrated circuits and the like.

the deposition of layers of alloys by vacuum evaporation by the Joule effect has also already been used and a specific case specifies the use of a crucible in a vacuum enclosure filled with a molten alloy, the two components of which have different evaporation temperatures. To overcome this drawback, an inert liquid retarding on the surface of the alloy plasma causes the element at the lowest vapor pressure point to join the element at the highest vapor pressure point in the most simultaneous evaporation. possible.

Other cases show the use of multiple crucibles, one per element of the alloy to be obtained, heated differently sequentially and in temperature, with directional plates to obtain the required concentrations. All this makes the operation very expensive, especially in view of the time required to have acceptable results because otherwise they are disappointing in view of the very random concentrations obtained. The above has been used in the case of photoconductive alloys with evaporation temperatures around only 300 Cº.

For alloys where the vapor pressures of the components are at much higher temperatures, sequential evaporations of separate metals have been made. This produces stratified deposits which, to form an alloy must then be annealed at temperatures varying according to the case, but which greatly exceed that which can be supported by certain substrates defined below.

Tests by various laboratories to form vacuum alloys, mostly binary, have been carried out in the past from separate evaporation sources for each deposition material. This system, by the Joule effect, has given results, but the control of each separate crucible is complicated and the different densities of metal vapor emitted mean that the cover of the substrate is not equal because of the random movements of the vaporized elements. the lightest one per t, and the distance between the sources of evaporation on the other. It is also necessary in certain cases to control the evaporation with a quartz oscillator. Starting directly from the Nickel-Iron alloy, which can be evaporated, in some cases, quite easily from a crucible, a substrate temperature of around 200º C is necessary, a temperature totally inadequate for polymer substrates or others do not support these temperatures.

An arrangement of multiple sources for depositing an alloy in constant production by the Joule effect under these conditions does not seem to exist at this time nor, a fortiori, from a single source.

In addition to the tests described above which were carried out in a vacuum chamber, by the evaporation of the deposition materials by the Joule effect, other tests carried out by different institutions by means of vacuum evaporation systems other than by Joule effect (electron beam devices, ion bombardment, ion implantation, etc.) have been achieved with some success. Most of the time it was undertaken to obtain binary alloys, but it should especially be remembered that certain tests have specific results based on theoretical models. However, layers of quaternary composition forming a protective alloy are used for a known application which is the electron beam deposition of the alloy M -Cr-Al-Y on the blades of jet engine rotors used in the marine environment (M is either Cobalt, Nickel or ter). This technology is applied in production especially in the USA and UKSS

Other deposits of various allies are used in microelectronics and for magnetic tapes where significant coercivity and memorization are necessary. These deposits are made by evaporation and condensation of uitrafins products on cold surfaces in the presence of a high pressure gas. Of all these methods, (experimental or not), none is validly applicable to the surfaces described below, whether due to technical, physical or even economic factors, these factors being moreover often concomitant .

A destination of the invention is, among other things, to obtain a layer of thickness chosen in the event of metallization for a specific purpose such as for example shielding against electromaometic fields.

To obtain this bimdage, two solutions can be adopted, the first of which is a metallization with a multilayer deposition and the second a metallization with an alloy deposition.

For the first solution, the substrates to be treated are therefore treated with metals with adequate magnetic reactions. In the band from 10KHz to 15KHz of electromagnetic field emissions, a solution for protection can be the evaporation under vacuum of pure nickel to form a deposit on the substrate. Against emissions from 15KHz to 27KHz a solution for protection can evaporation of pure copper to form this deposit on the substrate. In order to provide more complete protection against electromagnetic emissions ranging, for example, from 10KHz to 27KHz at most, the preferred solution is to do in one passage under vacuum a binary evaporation by source of evaporation by the Copper followed by the Nickel, Which allows thus covering the Copper by the Nickel to prevent oxidation of the surface of the copper deposit. This process also makes it possible to maintain a non-oxidizable and shiny surface as a last deposit as required for certain finished products. The copper-nickel deposit is obtained by the Δ of the vapor pressures of copper and nickel in their powder mixture and by other physical parameters used. such as the specific vacuum, the distance from the crucible to the substrate, the induction current, the type of crucible, this list not being limiting.

Other metals with an adequate magnetic character can be used in a binary, ternary or more manner, according to the above principle and according to the electromagnetic frequencies present. In addition, a preferred solution even for this vacuum metalization is to treat only one side of the substrate if necessary. This transparent or woven substrate mounted around or in front of a device emitting parasitic electromagnetic fields such as for example a cathode ray tube station in fact forms a shield against these fields which are deemed to be harmful to living cells.

For the second solution which is the preferred one and which could provoke a more aggressive treatment, it is understood that the metallization of fraqiles structures can only be done in a delicate manner if one wants to obtain the desired parameters. Trials of metalization by evaporation under vacuum (Joule effect) as described below have been supported by a research program and have led to a method and results defined below.

The method itself has a new direction for the definition of vacuum metallization of substrates, in this case delicate surfaces with several metals in a single operation, and in this case, in order to add to the substrate the ability to be the desired shielding against electromagnetic fields.

The shields against electromagnetic disturbing fields are known and are part of a choice of Fer-Nickel alloys with high magnetic permeability. These shields made from pure iron and nickel must necessarily undergo after machining and shaping a thermal cycle either under cracked ammonia, or under pure and dry hydrogen to avoid oxidation of these and to remove impurities. This treatment followed by controlled cooling is done at 1200ºC. It is also necessary to avoid, after this heat treatment, any physical deformation of the shielding which would risk greatly reducing its efficiency. Evaporation of a Fer-Nickel alloy on a substrate under vacuum has been tried but the results obtained have not been sufficiently conclusive, especially since the costly treatments undergone by this alloy in foundries for obtaining the desired crystal structure, are lost during evaporation. The search for an efficient and economical method to obtain high performance shielding results without starting from an already formed alloy was undertaken.

To this end, evaporation under vacuum should therefore allow a metallic deposit in a single operation from the different metals chosen and mixed in each source of evaporation. At constant vacuum (10 ^-5 Torr), the surface vapor pressure temperatures of the chosen metals are only close for some of them. By condensing the scale of evaporation temperatures it was necessary to obtain the following result; under well-defined conditions as to the specificity of the vacuum to be obtained, at the evaporation temperature, that of the substrate, the particle size of the covering materials, the mixture of these, and other parameters, the metals had to be deposited not in stratified layers but to form an alloy of the μ type. For this, it was also necessary that the conditions required for adhesion to the substrate be fulfilled. It is known that surfaces made of organic polymers (especially flat surfaces) pose problems due to their intrinsic physicochemical complexity.

In addition, the adhesion between metals and organic materials is not well defined because it is not known whether it is due to surface energies, dispersion forces or charge transfers. These surfaces can in some places suffer from micro-crevices. In this case, they must be treated beforehand to modify these defects and obtain good adhesion of the thin metallization layer.

For this purpose, the treatment of delicate substrates is done in a simple way by cold soaking in an adequate solution because all the other usual methods such as by heating at high temperature to separate them from their volatile impurities thus gue by other methods including acid soaking or exposure to ultraviolet light in the presence of Oxygen (03) which volatilizes the contaminant (for example Co or CO2) irreparably damages fragile substrates.

In cases where it is sought to form an alloy layer on a substrate, in order to form a shield against electromagnetic fields, it is necessary to create the magnetically permeable metallization possible. The vacuum evaporation metallization tests carried out to prove the invention according to the method described below were carried out with metals forming an alloy with high magnetic permeability applied to a substrate defined as a network of woven polymer monotilaments.

The solution chosen for the test program on this pretreated network as described above was therefore vacuum evaporation by the Joule effect, in a conventional vacuum installation which was defined as the most suitable for the project (Figure 1). The profile of the theoretical model was based on several parameters of which the following are the most important:

1) Formation of one or more metallized layers each comprising several metals to be deposited with the aim of forming at the time of deposition on a substrate an alloy, preferably for this case, with high magnetic permeability (minimum 2kAº of thickness of total skin)

2) Choice of premixed metals to vaporize allowing the most adequate crystalline orientation to obtain this permeability.

3) Use of permanent magnet trains to maintain the substrates during the evaporation process and to help this crystalline orientation of the elements.

4) Choice of metals whose alloy offers a surface with high index of reflection.

5) Simultaneous evaporation of all the elements of the premix to obtain the preceding points without scaling, stain and cracking of fatigue, and calculation of the time of rise in temperature and the time of maintenance of the defined maximum temperature.

6) Choice of the particle size of each of the metals to obtain this simultaneous evaporation. 7) Choice of physical parameters, such as the weight of the mixture, the intensity of the vacuum, the distance between the crucibles and that of the crucibles to the substrates, the planetary speed of rotation relative to the evaporation cones according to point 6 below. above to get points 1 and 5 above.

8) Cancellation of anisotropy and magnetostriction to make the walls of Bloch very mobile.

9) Elimination of obstacles to the movements of the walls, which are formed mainly by impurities.

10) Benefit from vacuum heat treatment by the very process of simultaneous evaporation of the required elements.

11) The absence of magnetic aging at low inductions.

12) Good adhesion to the substrate of the resulting thin layer and of the successive layers with one another in the event of similar or different repeated layers.

13) Imperative maintenance of the dimensional stability of the substrate and its initial stiffness rate by controlling its temperature during the evaporation process.

14) Hourly production adequate for the economic viability of the product.

15) Obtaining the simultaneous evaporation required from one or more sources of evaporation, each loaded with pre-mixed deposition materials and recharging the sources by multiple cups during the same vacuuming cycle of the chamber evaporation.

16) Choice of refractory sources or metal leagues or other suitable to avoid that the elements to be vaporized do not combine with the source.

17) Adaptation of the application of the process to all substrates such as woven networks in plastics or textiles, flexible films of various plastic materials, paper, glass plates, calendered or non-calendered metals of various films, objects made of these materials, this list not being exhaustive.

Evaporation sources of all sizes and thicknesses have been tested and the tunqstene has withstood the operations the best, most of the other sources combining with the elements of the alloy to be obtained.

Various deposition substances liable to result in maqnetically permeable deposits were used in pre-established proportions and various binary, ternary or quaternary alloys were produced. A quaternary alloy was finally selected for the test program, the components of which are pre-mixed in the following percentages: Nickel (+/- 75%) Copper (+/- 5%), Iron (+/- 18%) and Chrome (+/- 2%). All of them have a crystalline form either with centered face cubic crystals or with centered crystals (Table 9). This choice makes it possible to avoid undesirable anisotrepic fluctuations and makes it possible to create a film close to zero of magnetostriction, the two main components of which, after evaporation, are found in the alloy obtained at the rate of aux for Nickel and 15% for Iron for a layer thick enough for defined shielding.

An economically valid evaporation time has been calculated, which gives a thin layer made of a single evaporation of the mixture or of several evaporations of it (adequate skin thickness) for the frequencies involved.

A low temperature of the substrate was maintained without damage to it, which retains its dimensional stability and its initial strength. This low temperature also helps to get good crystalline orientation.

The substrate was held in place on a cylindrical iron substrate holder of the planetary system in the horizontal vacuum chamber of the deposition installation by two flexible strips of magnetized ferrite which, in addition to holding the substrate in place, were chosen to help a little the crystalline orientation of the elements during their deposition.

The evaporation took place under a vacuum approaching 10 ^-5 Torr in order to shrink the absolute scale of the deltas of vapor pressure temperatures of each of the deposition materials according to a diagram of chain alloys (table 9).

The four metals were used in the form of ultra-fine powders and mixed in the proportions given above.

A very thin layer of the melanqe was spread over the evaporation source (crucible) to obtain the determined coverage.

The visualization during the operation showed, at their evaporation temperature verified with the optical pyrometer, an evaporation of the elements without "drizzle", clear and continuous.

The examination of the substrates after different metallization times did not indicate a coverage of these preferably by one of the metals rather than by the others.

At the first examinations, the results indicated that a homogeneous magnetically permeable alloy was obtained and that it represents the desired V-alloy (Table 10).

the method and the results which result therefrom as described in the preceding paragraphs and which relate to metallization by evaporation under vacuum of a substrate by several powdered metals premixed in a single source of evaporation are adaptable to many other substrates for other applications. Confirmation of the interaction of the variable data listed from 1) to 17) on pages 8, 9 and 10 without this list being limiting, and of the vapor pressure points of the pre-mixture metals which are constant data, has been demonstrated , because any modification of one or more of the variable data changes the results and it is thus possible to choose either a multilayer deposit or a homogeneous alloy.

The metallized vacuum networks according to this process during the test program were subjected to rigorous tests at the National School of Mines of Paris - Department of Surface and Tribology - Sophia Antipolis. (CEMEF).

The equipment used: A JEOL JSM 35 CF scanning microscope combined with. a TRACOR 5500 X-ray dispersive energy analysis spectrometer.

The edition of the tests follows (Tables 1 to 7).

Object of the test:

1) Analysis of the metallized side of the network and of the composition of the alloy obtained.

2) Analysis of the opposite side of the network to determine the components of the filaments and the primer.

3) Verification of the sample holder to define residual impurities on it.

4) Analysis of the residual mixture of the 4 basic elements in the crucibles (sources of evaporation).

5) Evaluation of the differentials obtained and the results.

The abovementioned analyzes, in addition to the four elements of the alloy, made it possible to detect in particular titanium, zinc, a surplus of copper, calcium, chlorine, phosphorus, and some other background elements. They were eliminated by the established differential analyzes. Indeed these elements come from either from the pretreatment layer of the filter network, or from the composition of its filaments (titanium), or from the sample holder and also from the enclosure (chlorine and zinc) and are found in identical proportions, as the source of evaporation (crucible) is either molybdenum or tungsten.

The alloy itself is well composed of the four basic elements used during the vacuum evaporation process. The quantitative values are as follows for the overall surface of the sample of the filter network subjected to the tests:

% weight Test% weight in the pre-vaporization mixture

Cr 1.02% 2%

Fe 16.71% 18%

Ni 78.81% 76%

Cu 3.47% 4%

The quantitative analysis is subject to variations of the order of +/- 3% for the percentages of high weight. These variations are inversely proportional to the weights of the components.

It should be noted that neither the tungsten nor the molybdenum forming the sources of evaporation used, are found on the substrate and that Ni and Fe are not found either in these sources whereas these are the two elements which usually try to associate with them. This would seem to prove that the formation of vapor of the four elements present in the source is at the start of a surface tension which prevents such an association with the source.

During the overall surface test during the scanning of the substrate by the bombardment of particles on the non-metallized side of the network under analysis, significant deformations and flow of material could be visually noticed. the microscope screen. (figure 2).

On the other hand, the metallized side under analysis did not suffer from any deformation on any part of its surface. This seems to induce a perfect evacuation of the electromagnetic charges to which this surface was subjected and a total protection of the underlying material. Even during the point analysis, when the electron bombardment was focused on the equivalent of a diameter of less than a micron, only a notch of this size appeared on the metallized surface without any deformation of the underlying material (Figure 3) .

To complete the analyzes obtained with the TRACOR 5500, an analysis by ESCA erosion spectrometry (XPS), still within the confines of the Ecole des Mines, was implemented.

The results read as follows:

The deposits consist of Ni, Fe, Cu, Cr. The substrate is polyester, polyamide and carbon polyamide. The peaks analyzed are as follows (the bond energies are indicated for information in parentheses):

Ni 2P1 / 2 - 2P3 / 2 (873-855 eV)

Fe 2P1 / 2 - 2P3 / 2 (723-710 eV)

Cu 2P1 / 2 - 2P3 / 2 (954-934 eV)

Cr 2P1 / 2 - 2P3 / 2 (536-577 eV)

O 1S (531 eV)

C 1S (287 eV)

The network surface used for the analysis is part of the same sample as that used for the TRACOR analysis.

5500. The analyzes were carried out with the K α line of aluminum. As in this case, the Nickel Auger peaks are superimposed on the 2P3 / 2 iron peaks, a second series of analyzes was therefore carried out with the Kα line of magnesium. In that case, the iron peaks are no longer disturbed and it was possible to evaluate the sensitivity factor corresponding to Fe 2P1 / 2, the only iron peak measurable with the Aluminum source.

Each sample is eroded using a beam of Argon ions (4 KeV, 3μA). Scanning on a square of 8 mm side for approximately 90 minutes. This erosion is stopped at regular intervals to allow the acquisition of spectra

(acquisition takes place over an area of approximately 8 mm2). The area under the peaks, after removing the background noise, is then measured and used for the calculation of the atomic concentrations. These concentrations are calculated from the sensitivity coefficients given in the XPS manual (X-ray

Photoelectronic Spectrometry).

The results read as follows: The thickness of the analyzed metallic monolayer, evaluated from 30 to 50 nanometers, is determined from the concentration profiles of the

Nickel and Carbon, by comparison with profiles obtained for layers of the same thickness of NiCr / SiO2.

For this first layer which can remain unique as needed, the Nickel-Iron concentration is homogeneous over the entire thickness of the deposit, then that of Chrome is less so that of Copper which tends towards a maximum at the metal layer interface. -substrate.

The atomic concentrations of the 6 elements (Ni, Fe, Cu, Cr, U, C) are reported in Table 11. In Table 12, these concentrations are reported without taking carbon or oxygen into account. An integration of these values over the total thickness of the layer gives the following percentages which are much more precise than those obtained with the Tracor 5500.

Cr: 2% Fe: 18%

Ni: 76%.

Cu: 4%

C: (so-called "pollution" disappear during

O: the first 5 minutes of erosion).

These percentages are those of the elements from the pre-spray mixture. However, for a greater layer thickness of the alloy thus formed, by successive evaporations for example, a decrease in the percentage of Nickel in favor of that of Iron will appear, as will be seen below, the Copper and the Chromium not undergoing only small decreases. We are heading towards a desired alloy with a composition of 80% Ni / 15% Fe / + Cu + Cr.

Samples for additional tests treated by additive successive evaporations on substrates made of network in all points identical to that used for all the previous tests were created according to the following mode:

- constant vacuum 10 ^-5 Torr

- constant weight of 0.15 qrs of pre-metallization mixture in the crucible calibrated in tungsten.

- constant amperage of 14A.

- constant evaporation time of 120 seconds.

Three samples were retained from these preparations, one metallized twice successively, the other three times successively and the last four times successively.

The samples were analyzed by the Spectrometer

TRACOR 5500 at the Ecole des Mines. The layout is clear and perfectly defines the peaks of the various elements. The weight percentages obtained for the sample subjected to four successive evaporations read: 3.52% Cr

4.24% Fe

77.92% Ni

4.33% Cu

This quantitative analysis (Table 8) subject to the tolerances of TRACOR 5500 indicates a greater Δ% between Ni and Fe for this layer with a thickness significantly greater than that analyzed previously (Tables 1 to 7).

These samples also studied by ESCA erosion give the following results:

The little Cu-Cr heterogeneity visible for the first thin layer evaporated directly on the substrate (Tables 11 and 12) disappears to show perfect homogeneity for the following successive layers. We can see that the parameters of the crystal meshes from one layer to the other create an optimal epitaxy given their identity and the constant crystal orientation thus created. The "vapor atoms" resulting from multi-element evaporation receive from the substrate a "bonding bond" and which smooth along the receiving surface until a finite moment when they unite with one another in totally adsorbed islands among the atoms of this surface. At this finished moment, they become solid by a process of exothermic condensation and the multiple islets join together, even as they form, to create a layer of homogeneous thickness.

The initial "bonding" of the "vapor atoms" is probably initiated by their kinetic energy whatever the temperature of the substrate. Adsorption penetration effectively creates an atomic weld at the interface point of layers made of identical alloys, ie an epitaxy of "continuity".

The weight percentages defined by integration on the thicknesses for 3 and 4 successive evaporations of 120 seconds each are Ni 80/81%. Fe 14/15%, Cu 3%, Cr 2%. These results confirm those obtained with TRACOR 5500, namely an increase in the weight percentage of Nickel compared to that of iron which tends towards the desired percentages for the deposit of alloy (80% Ni / 15% Fe) + others.

The thicknesses obtained show an increase in increment thereof by evaporation layer of the order of 80% of the thickness of the previous layer (Tables 13 and 14).

Additional tests were undertaken which aimed to define curves representative of the volume increments and metallization thicknesses.

For this purpose, 3 cm 2 of each of the 3 samples were coated with a two-component resin of hardness equal to that of the substrate.

Two of the three samples referenced under numbers 22 and 23 and representing respectively the parts subjected to three and four successive evaporations were finally selected.

Slides formed by Cryo-ultramicrotomy and ultramicrotomy were observed with an electron microscope type CM12 Philips at 100 KeV at the joint center of Applied Microscopy of the Faculty of Sciences of the University of Nice. To compensate for the crushing and tearing which can occur during the cutting of the blades, each sample was cut in a number n of times three blades with different cutting directions A) from bottom to top B) from top to bottom and C) laterally ( Figure 4 and Table 15).

An then establishes an average according to:

The layer thicknesses obtained by this method read as follows: 1) layer thickness of sample 22 = 225 nm, 2) layer thickness of sample 23 = 405 nm.

By joining the thicknesses evaluated during the preceding analyzes for a single evaporation and for two successive evaporations to those obtained above, the curve of table 15 is obtained.

One can notice that with each additional thickness an increment almost equal to the thickness of the previous layer is obtained. This has been verified up to four successive evaporations.

All of the studies and their results made it possible to undertake the manufacture of the prototype of a tensioning system for crucibles alternately, with dosing and automatic filling thereof to maintain continuous metallization in the vacuum chamber constant. This "continuous" evaporation composed in fact of successive evaporations without stopping time, makes it possible to obtain on the same substrate (s) by continuous back-and-forth or planetary winding systems, the thicknesses required for defined shields, for example in the event of protection against electromagnetic fields (figure 1)

The layers formed by successive evaporations in the same enclosure under constant or variable vacuum according to the case by the method which is one of the subjects of the invention allow, by the metering and filling system of the crucible (s) at each power-up successive close together, alternating or creating different layers of alloy at each of the evaporations, one or more of these layers being able to be starting from a single metal or from other materials in order to create a multi-layer stratification of thicknesses chosen on the substrate for required properties. We can also alternate 2 or 3 evaporated layers of the same alloy with several components, this resulting as we have seen, in a homogeneous thickness of alloy, and follow this with an evaporation of insulating, refractory or other material and so on with the desired varlances. this can also be carried out differently for each crucible in order to create several longitudinal strips of dissimilar deposits on the same substrate.

In the method chosen for carrying out the implementation of the principles of the invention (FIG. 1) the Joule evaporation system comprises an evaporation chamber (1) provided with a door (14) by which a planetary assembly is an epicyclic system made of a cradle (7) which holds two planet carrier rings (2) whose planets (3) are the substrate carriers, the cradle being provided with friction rollers (6) whose one is rotated by a motor (8), the planetary system being provided by the chain (15) and its tensioner (16).

In the center of the planetary assembly a plate (9) serves as a platform for the sources of evaporation or crucibles (4) each supplied with current by the nickel-plated copper electrodes (5) which include a common neutral to the crucibles and a phase arrival separated by crucible to allow precise adjustment of each of them. Series of buckets (11) with their pouring spouts (13) move forward or backward by manual or automatic control along rails (10) provided with lugs (12) which regulate the filling of the crucibles (4) before each energization d evaporation of these depending on the choice of alloy or other material to deposit and the sequence to follow. This takes place as described during a vacuuming cycle, the qodets being pre-dosed before the door (14) is closed. The number of cups per crucible allows an equal number of successive evaporations for this crucible and the method allows the use of a large number of crucibles.

The pouring spouts (13) have the desired length and are at a sufficient distance from the crucibles (4) during evaporation so as not to disturb the cones of evaporation (17). It is clear that a substrate formed from wound material such as polymer sheet can be treated in the same way, the substrate unwinding from a coil on one side of the vacuum chamber (1) to wind on the other side, after having passed over two thin and parallel rollers between which the surface to be treated takes place which scrolls slowly over the crucible systems (4) and their measuring cups (11). The unwind-wind system for roll or reel substrates is not shown in Figure 1.

To prove the effectiveness of metallized substrates by the method of the invention for creating shielding against electromagnetic fields, tests of attenuation of these fields by these substrates were undertaken. It was necessary to prove the degree of protection obtained for living materials between others, the human being which can be subjected to the fields emitted by the display screens and which are considered as harmful. It was also necessary to prove the degree of protection offered to inert materials, among other finished products such as electronic and computer products, in their daily use or for example during their transport. The substrates treated according to a model of the described method were subjected to rigorous tests to define the quality of the shieldings obtained.

These usual tests in this area have been established to calculate the attenuation of an electric field E and a magnetic field H by substrates metallized with the H type alloy, ie the modification of the propagation of the magnetic radiation H in outside of its primitive direction. This is obtained by its diffusion through a homogeneous and permeable medium such as the skin thickness of the metallization of the treated substrate. The shielding efficiency against harmful fields is expressed in dB attenuation.

The substrates chosen were a woven network metallized by the Fe-Ni-Cr-Cu mixture forming an alloy and a 0.3 mm thick PVC film covered with the same alloy. Samples of these measuring 200 mm x 200 mm were glued to 4 mm thick glass plates. These assemblies were then placed in an aerial analyzer (generator and receiver), (Figure 5).

The aerials are loop antennas (or frames), low impedance, diameter 30 cm. They consist of one or more turns of copper wire.

The "generator-aerial transmission" and "receiver-aerial reception" connection cables are coaxial cables having a shielding efficiency compatible with the performance of the shielding to be measured.

The shielding efficiency of the receiver and the coaxial connection cable must be such that, When these are placed in the reference electric field after replacing the receiving aerial with a shielded charge of equivalent impedance, no signal is detected by the receiver.

The measurement procedures are established for three levels of wave impedance:

- low impedance magnetic field

- high impedance magnetic field

- plane wave (W / O = 377Ω)

In the case of substrates under test, the most important measurements were those defined for a low impedance maqnetic wave level. The measurement principles are as follows:

One uses on the one hand an emitter assembly (generator and loop) which produces in steady state a magnetic field, on the other hand a receiver assembly consisting of a loop similar to the previous one and a field meter.

Initially the two loops are positioned in the same plane, perpendicular to the wall to be tested but oriented in any way at a distance "d" from one another without any obstacle between them. One reads the level A (in dB) indicated by the field strength meter.

In a second step, the two loops are placed on either side of the wall to be tested, in the same relative positions and at the same distance "d" from each other. Without modifying the generator setting, the level B (in dB) indicated by the field meter is noted.

The difference A - B represents the attenuation (in dB) of the wall, ie of the substrates under test for the magnetic field, at the frequencies considered.

The tests were carried out in accordance with MIL-SID.285 and GAM.1.20 and according to the process listed above. The results obtained read as follows:

FREQUENCIES Attenuation in dB by metallized substrates of the fields by 4 consecutive evaporations of E - M Fe-Ni-Cr-Cu mixture during the same vacuum cycle 10 KHz 14 dB

20 KHz 17 dB

50 KHz 20 dB

100 KHz 22 dB

1 MHz 41 dB

10 MHz 54 dB

Tests were also done to prove the attenuation of the E fields which turned out to be around 99.99%.

Grounding of these shielded substrates is necessary when static electricity buildup is to be removed.

Claims

RESELL ICAT IONS

1) Method of evaporation of metals on substrates characterized in that several powdered metals are intimately mixed and that this mixture placed in each of the evaporation sources of a vacuum installation is vaporized by Joule effect without drizzle protection for optionally forming a multilayer deposit by consecutive evaporations of the metals in the mixture, or a homogeneous alloy by simultaneous evaporation of the mixture depending on how the interaction of the constant physical parameters is modified, which are the vapor pressure temperatures of the metals of the mixture and of the physical parameters which one chooses to vary and which are the composition and the weight of the mixture placed in each source of evaporation or crucible, the granulometry of each metal of the mixture, the dimensions and the material of the crucible which should not be combined to none of the metals in the mixture, the distance between the crucibles and that between each crucible and the bstrates, the speed of passage of the substrates opposite each cone of evaporation of the mixture, the internal temperature of the vacuum chamber and the temperature of the substrates, the intensity of the vacuum, the duration of the rise in temperature of the crucible to at a maximum, the definition of this maximum temperature, the duration of the maintenance of this maximum temperature of the crucible.

2) metallization according to claim 1) characterized in that the mixture of metals is composed of iron, nickel and one or more other auxiliary metals such as copper and chromium in predetermined proportions and that the deposit on the substrate is in all cases of claim 1) a form of shielding against electromagnetic fields and in the specific case of an alloy, a shielding with high magnetic permeability against these same electromagnetic fields to effectively protect living materials and inert against them.

3) metallization process according to claims 1) and 2) characterized in that one uses flexible magnetic strips to maintain the substrates to the iron cylinders of the planetary system of the enclosure under vacuum and to assist the crystalline orientation of the alloy deposit.

4) Metallization according to claim 1) characterized in that it is the only one that can be used on fragile substrates such as woven networks of textile or plastic, thin films of plastic, or any other substrate, which must keep a perfect dimensional stability, and this because of the low temperature at which these substrates can be maintained and that it forms a protection for the substrate.

5) metallization process according to claims 1) and 2), characterized in that during the same vacuum cycle of the evaporation chamber, several identical evaporations are carried out successively to increase the thickness of the deposit and obtain a layer of which the thickness can be defined in advance and that this layer forms a homogeneous alloy deposit on all substrates including those with calenders of insulating film.

6) A method of vacuum evaporation on any substrate according to claims 1) and 2), characterized in that during the same vacuum cycle of the evaporation chamber, several non-identical or partially identical evaporations are made successively to form layers of variable thicknesses separated as desired by layers of other materials and even to form completely different layers from each other, the whole thus forming a final layer stratified according to the desired variances.

7) Vacuum evaporation device according to claims 1), 2), 5), and 6) characterized in that qodets provided with a pouring spout, which are moved back and forth on rails along the crucibles according to a pre-established sequence, are dosed beforehand with contents to be evaporated which must be poured according to the sequence into the crucibles before they are put under evaporation tension and this during the same vacuuming cycle.

8) Metallized substrates according to all of the preceding claims, characterized in that they are made from weavings or films of plastic materials made electrically conductive, which can be earthed, and that they are covered of a deposit of shielding against electromagnetic fields which protects living materials against the latter including those from display screens and considered harmful to humans and that these substrates having only one side metallized by the high index shielding of reflection, are placed in front of or around the display screens.

9) Metallic substrates according to all the preceding claims, characterized in that they protect the inert materials that are the finished products of the electronic and computer sector against electromagnetic fields during their daily use and transport.