WO2010076422A1

WO2010076422A1 - Method for assembling two substrates in a vacuum at a negative temperature, and machine for implementing said method

Info

Publication number: WO2010076422A1
Application number: PCT/FR2009/001438
Authority: WO
Inventors: Daniel Perrin
Original assignee: Carewave Shielding Technologies (Sas)
Priority date: 2008-12-19
Filing date: 2009-12-17
Publication date: 2010-07-08
Also published as: FR2940320B1; FR2940320A1

Abstract

The invention relates to a method for assembling a first substrate (1) to a second substrate (2), characterised in that it comprises the following steps in a vacuum and at a negative temperature: depositing a thin film (5) of an assembling material onto a first surface (3) of the first substrate (1); depositing a thin film (6) of the same material onto a second surface (4) of the second substrate (2) having a shape complementary to that of the first surface (3); contacting said first surface (3) with said second surface (4); pressing said first surface (3) against said second surface (4). The invention also relates to a machine for implementing said method.

Description

METHOD FOR ASSEMBLING TWO SUBSTRATES IN VACUUM AT NEGATIVE TEMPERATURE AND MACHINE FOR CARRYING OUT SAID METHOD

The present invention relates to a method for assembling two substrates under vacuum and a machine 5 for implementing such a method.

In the field of assembly there was no method that can be implemented under vacuum.

The invention relates to a method of assembling a first substrate with a second substrate, comprising the following steps carried out under vacuum and at a negative temperature:

depositing a thin layer of assembly material, on a first surface of the first substrate, depositing a thin layer of the same material on a second surface of the second substrate of complementary shape to said first surface;

contacting said first surface and said second surface, pressing said first surface against said second surface.

According to another characteristic of the invention, the connecting material is chosen from: bismuth, antimony, lead, thallium, cadmium or indium.

According to a preferred feature of the invention, the joining material is indium.

According to another characteristic of the invention, the thickness of the two thin layers is identical.

According to another feature of the invention, the thickness of each of the thin layers is at least 200 nm +/- 5%. _v

According to another characteristic of the invention, the thickness of each of the thin layers is equal to 800 nm +/- 5%.

According to another characteristic of the invention, the material of the thin layers has a purity of at least 99.95%.

According to another characteristic of the invention, the materials of each of the substrates are chosen from: organic, rigid carbonaceous material, flexible carbonaceous material, or thermoformed organic material.

According to another characteristic of the invention, the process is carried out at a temperature below -150 ^° C. According to another characteristic of the invention, the pressing pressure is at least 45 pascal +/- 3%.

According to another characteristic of the invention, the vacuum pressure is less than 10 ^{~ 6} mbar.

The invention also relates to a machine for assembling a first substrate with a second substrate comprising:

a sub-cavity, a module for depositing a thin layer of assembly material, on a first surface of the first substrate,

a module for depositing a thin layer of the same material on a second surface of the second substrate,

means for bringing said first surface and said second surface into contact,

- A means for pressing said first surface against said second surface - a cryogenic plant to reach and maintain in the chamber a negative temperature.

According to another characteristic of the invention, said deposition modules are able to deposit thin layers of identical thicknesses. According to another characteristic of the invention, the machine further comprises a cryogenic plant for reaching and maintaining in the chamber a temperature below -150 ^° C. ^~ - -

According to another characteristic of the invention, the pressing means is capable of applying a pressure at least equal to 45 pascal +/- 3%.

According to another characteristic of the invention, the machine also comprises at least one vacuum pump capable of producing in the chamber a vacuum pressure of less than 10 ^{~ 6} mbar.

According to another characteristic of the invention, the machine comprises at least one pair of pressure rollers capable of pressing two substrates of flexible sheet material. According to another characteristic of the invention, the machine comprises a first pair of guide rollers, at least one pair of pressure rollers and a cryogenic module able to regulate the temperature of the guide rolls at -150 ^° C +/- ⁰ C and the temperature of the pressure rollers at -150 ° C +/- 2 ° C.

Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below as an indication in relation to drawings in which:

FIGS. 1-3 illustrate the different steps of the assembly method according to the invention,

- Figure 4 shows a diagram of an embodiment of an assembly machine. In FIG. 1 are diagrammatically a first substrate 1 and a second substrate 2. These two substrates are intended to be assembled by welding / bonding the first substrate 1 by its surface 3 with the second substrate 2 by its surface 4. A condition of the process is that these two surfaces 3, 4 are complementary. This means that the surfaces 3, 4 are shaped to fit perfectly one on the other. In the case of rigid substrates 1 2, the surfaces 3, 4 have shapes which adapt perfectly. This condition is still achieved when at least one of the substrates 1, 2 is flexible or deformable and that its surface is deformed to fit the surface of the other substrate when the two substrates 1, 2 are pressed against one another. 1- 'otherT

At the start of the process, the two substrates 1 and 2 are separated as illustrated in FIG. 1. Depending on the process used for depositing, one or more prior steps, known to those skilled in the art, may be advantageous or necessary. in order to prepare the substrate 1, 2 to better receive said deposit. Thus sputter deposition is advantageously preceded by ionic etching.

Similarly, the substrate 1, 2, considered at the start of the process according to the invention may be blank or have already undergone one or more preliminary thin layer deposits.

According to a first step illustrated in FIG. 2, each of the respective surfaces 3, 4 of the substrates 1, 2, to be assembled, receives a thin layer deposition of an assembly material. A first means 7 deposits on the first surface 3 a deposit 5. A second means 8 deposits on the second surface 4 a deposit 6. According to one embodiment the first depositing means 7 may be merged with the second depositing means 8. As illustrated in FIG. 3, the first surface 3 of the first substrate 1 and the second surface 4 of the second substrate 2 are brought into contact in order to make the complementary shapes coincide and to present the joining material 5, 6. A pressing force 9, 10, of the two substrates 1, 2, against each other is then applied. This pressing carries out the assembly between them of the two layers, which thus fix the two substrates.

The assembly can then be put back into a vacuum and temperature condition. It retains its welding / adhesion properties and produces a particularly strong assembly.

The mechanical performance of such an assembly is extremely good. Thus, an assembly using indium as an assembly material has a peel strength of 20 to 22 N / mm ² .

The basic principle of the assembly is the realization of two pure layers 5, 6, respectively filed Fitting material on each substrate ï ^~ 2 ^~~ Tra- ^{^'*} setting into pressure contact of two pure layers 5, 6, and having complementary shapes allows interpenetration at the atomic level of the two layers. This results in a molecular diffusion bonding of the two layers. A necessary condition for the mutual molecular diffusion of the layers 5, 6 is that both are made with the same joining material.

The deposition, the contacting and the pressing are carried out under vacuum, and the layers 5, 6, of assembly material are not altered, for example by oxidation, between the deposit and pressing. Once assembled, the layers of assembly material are isolated from the environment and this isolation gives the assembly a very good durability.

The assembly material thus deposited in a thin layer is a metal advantageously chosen from: bismuth, antimony, lead, thallium, cadmium or indium. All the materials that are candidates for assembly material have not been identified so far. Likewise, the characteristic or characteristics of the material that makes it suitable for performing the welding / bonding are not precisely determined. It is certain that the six materials mentioned previously work. Given their relative dispersion in Mendeleev's table, other materials might be candidates.

The eligibility criteria for an assembly material are, inter alia: its ease of implementation for supplying a deposition module, its electrical conductivity, its capacity to be deposited in a thin layer, its physicochemical stability at low application temperatures. process, its cost, its dangerousness, ... Among these six materials, bismuth, antimony, lead, thallium, and cadmium are polluting components and dangerous for the environment and for the man, which makes delicate the Handling, maintenance and reprocessing operations at end of life. Also it is best to avoid them. Also bismuth, antimony, thallium, cadmium are very expensive materials. The cheaper lead a priori, becomes also as soon as we consider the purity necessary for the implementation-of-the-process. Moreover, their conditions of deposit are complex: instability during the deposit, deposit in the form of islands. These materials are less easily physicochemically compatible with the substrates materials or ¹ of the previous deposited layers, and there may be phenomena of rejection, ie deposits do not adhere to each other because of Inter layer creation. The temperatures necessary to obtain the creep conditions necessary for welding / bonding are even lower.

Indium does not have these two disadvantages and is as a candidate "particularly advantageous. Indium has good conductivity and good adhesion ^1.

Indium is simple and easy to deposit and allows uniform deposits. Indium has a physicochemical compatibility with metals such as Cu, Cu / Ni, Cu / Ag, Aisi

(stainless steel), Au, Cu / Ag, Al, Al / Ag and all possible alloys with these materials. Indium has a mechanical compatibility with the materials (previously deposited substrate or layer materials) without modifying the electrical performance of previously deposited layers. Indium is perfectly isotropic, ie its spatial physical properties do not change, whatever the molecular dynamic direction.

In order for the welding / bonding to work optimally, the thicknesses of each of the two thin layers 5, 6 respectively deposited on each of the surfaces 3, 4 should be identical.

So that the welding / bonding operates optimally, it is appropriate for the interpenetration molecular diffusion can be realized that said thickness of each of the thin layers is at least equal to 200 nm +/- 5%.

Advantageously, a thickness of 800 nm +/- 5%, especially in the case of indium, is preferred. Similarly, a purity of at least 99.95% of the constituent material of the thin layers is a good quality condition of the welding / bonding obtained.

^{^} The materials of each of the substrates 1 ^~ ^~, ^~ 2y can be selected from numerous materials. Thus it is possible to apply the assembly process to materials such as glass, metals or crystals. It should be possible to deposit a thin layer of connecting material. However, it is also possible to deposit intermediate bonding layers, if necessary, if the connecting material proves incompatible with the substrate 1, 2. Preferably for the intended applications, the substrate 1, 2 consists of a material chosen from: organic fabric, carbonaceous material rigid, flexible carbonaceous material, or thermoformed organic material.

A particularly interesting application uses flexible materials in sheet or thin film. In order to make possible the molecular diffusion which allows the assembly, it is appropriate that during the contacting and pressing of the two deposited thin films 5, 6, the assembly material reaches creep performance placing it under favorable conditions. to molecular adhesion, allowing fusion at the molecular level of the two deposited layers 5, 6.

Said creep performance is obtained as soon as the temperature of completion of these steps becomes negative.

However, a net improvement effect of the quality of the assembly is particularly observable when these steps are carried out at a temperature below -15O ⁰ C.

An optimum temperature achieving these conditions, especially in the case of indium and under the conditions of vacuum pressure and pressing pressure considered, is equal to -150 ⁰ C +/- 2 ° C.

The molecular inter-diffusion of the two layers 5, 6 is favored by a pressing pressure of the two substrates 1, 2, at least equal to 45 pascal +/- 3%.

A minimum vacuum pressure makes it possible to avoid the risk of surface oxidation of the deposited layers 5, 6, which is always possible with the high purities of assembly material used. The vacuum pressure is advantageously less than -10 ^-6 mbar, or even -10- ^~ -mbar-

In order to implement said assembly method, a machine 11 comprises a vacuum chamber 12. In the continuity of this chamber 12, the machine 11 comprises a first module 7 capable of depositing a thin layer 5 of assembly material, on a first surface 3 of a first substrate 1 and a second module 8, which can be confused with the first module 7, able to deposit a thin film 6 of the same material on a second surface 4 of a second substrate 2.

The deposit can be made by any device capable of deposit a thin layer of material under vacuum. Thus it is possible to deposit by electrolytic deposition, vacuum evaporation, sputtering or any other device / process known to those skilled in the art. In the context of the process according to the invention, in view of the assembly materials envisaged, the deposition is preferably carried out by sputtering.

The machine further comprises means for contacting said first surface 3 and said second surface 4, and means for pressing said first surface 3 against said second surface 4 by applying a pressure force.

The machine is advantageously capable of depositing thin layers of identical thickness. Similarly, it is advantageous to deposit the two layers of material, assembly on the two substrates at the same time, in order to obtain two diffusion surfaces in the same physicochemical state.

In order to place the layers 5, 6 of assembly material at the temperature permitting the molecular diffusion and therefore the welding, the machine 11 also comprises at least one cryogenic unit making it possible to reach and maintain in the chamber 12 a temperature lower adapted. In the case in particular of indium, this temperature is at least equal to -150 ^° C.

For each material, an ideal temperature where the creep characteristics are achieved can be determined. ^" The cryogenic plant is ^" advantageously ^" capable of achieving this temperature in the enclosure 12, or at least at the level of the substrates 1, 2, and under vacuum conditions, and then regulate it with an accuracy of the order of +/- 20 ^° C. In the case of indium, this temperature is -150 ^° C. ± 20 ^° C.

The machine is still such that the pressing means is able to apply a configurable pressure and advantageously controlled with an accuracy of the order of +/- 3%. Under the conditions of implementation of the process, this pressure is at least 45 pascal +/- 3%. The machine also has at least one vacuum pump capable of producing in the chamber a vacuum pressure of less than 10 ^{~ 6} mbar.

A particularly interesting embodiment relates to substrates 1, 2, of small thickness, a few tenths of mm, flexible, sheets or continuous films.

In order to treat such substrates 1, 2, an embodiment of the machine 11 is shown schematically in FIG. 4. The machine 11 comprises, in an enclosure 12, at least one pair of pressure rollers 13 able to press two substrates 1, .2, flexible sheet material. In the figure, the substrates 1, 2 come from the bottom, where they have undergone a deposition 5, 6, of assembly material within a deposition module (not shown) placed in said enclosure 12. The substrates 1 , 2 pass over a first pair of guide rollers 14, then between two pressure rollers 13. A cryogenic module is able to regulate the temperature of the guide rollers 14 to -150 ⁰ C +/- 10 ⁰ C and the temperature of the rollers 13 to -150 ⁰ C +/- 2 ° C, in order to communicate these temperatures to the substrates 1, 2, during their passage over or between said rollers 13, 14. The substrates 1, 2 assembled by pressing form a single assembly 15 who leaves the machine 11 from below.

According to one embodiment, the chamber 12 consists entirely of a double wall forming a cavity with a thickness of 50 mm.

Inside this cavity flows cycled water at 300 ^~ ± itres- / second, - resulting from a -cooling-cooling system, whose temperature does not exceed the limit of the dew point.

The . Specific cryogenic equipment built into this chamber include:

a first "Polycold" system making it possible to obtain negative temperatures of less than: -15 ^° C. to +/- 10 ^° C., the threshold for adjusting the temperature is: -110 ^° C.,

a first brazed pipe network on the internal faces of the enclosure 12, a second network of pipes brazed on thermal radiators.

The two networks are connected between the first polycold and the thermal radiators.

The heat radiators are placed near the substrates 1, 2, when the latter enter the chamber 12 for pressing, thus creating a first volume of low temperature.

The vacuum is a bad heat exchanger, the knowledge of the actual temperature is imperative and requires to set up measurement means to know the different temperatures depending on the location.

Five cryogenic thermocouples are positioned:

- two cryogenic thermocouples in contact with the thermal radiators,

a cryogenic thermocouple positioned in a vacuum,

two cryogenic thermocouples in contact with the walls of the enclosure 12.

A second system "Polycold" refrigerant performance identical to the first and provided with a finer temperature control accuracy: - 150 ⁰ C +/- 2 ° C, is connected directly to the guide rollers 14 and pressing

13.

Four cryogenic thermocouples are positioned: two cryogenic thermocouples placed inside each of the two pressing rollers 13,

two cryogenic thermocouples positioned on the outer side of the rollers.

The rollers 13, 14 are made of stainless steel AISI 420. The contact surfaces with the substrates 1, 2 are advantageously coated with a non-stick deposit such as molybdenum sulphide pulverized in the mass and polished.

The guide rollers 14 are responsible for directing the substrates 1, 2 towards the pressure rollers 14 by lowering the temperature of the substrates ^" 1, 2.

The pressure rollers 13 are automatically adjusted in pressure according to the physicochemical nature of the substrates 1, 2, and deposits 5, 6. The assembly machine requires a precise calibration and calibration phase, in particular as regards the cryogenic parameters, all the parameters thus determined being integrated into a machine control automaton in order to guarantee the reproducibility of the process. realized.

Claims

1. A method of assembling a first substrate (1) with a second substrate (2), characterized in that it comprises the following steps carried out under vacuum and at a negative temperature:

- Deposition of a thin layer (5) of assembly material, on a first surface (3) of the first substrate (1), - Deposition of a thin layer (6) of the same material on a second surface (4) second substrate (2) of complementary shape to said first surface (3),

contacting said first surface (3) and said second surface (4), pressing said first surface (3) against said second surface (4).

2. The method of claim 1, wherein said joining material is selected from: bismuth, antimony, lead, thallium, cadmium or indium.

3. The method of claim 1 or 2, wherein said joining material is indium.

4. Method according to any one of claims 1 to 3, wherein the thickness of the two layers (5, 6) thin is identical.

5. The method ^{~ "1} ^a" one ^~ ^{^"claims"} 1 ^~ k ^~~ A ^~, wherein the thickness of each of the layers (5, 6) thin is at least equal to 200 nm +/- 5% .

6. The method of claim 5, wherein the thickness of each of the thin layers (5, 6) is equal to 800 nm +/- 5%.

The method of any one of claims 1 to 6, wherein the material of the thin layers (5, 6) has a purity of at least 99.95%.

8. Method according to any one of claims 1 to 7, wherein the materials of each of the substrates (1, 2) are selected from: organic fabric, rigid carbon material, flexible carbon material, or thermoformed organic material.

5

9. Process according to any one of claims 1 to 8, carried out at a temperature below -150 ^° C.

The process according to any one of claims 1 to 9, wherein the pressing pressure is at least 45 pascal +/- 3%.

11. A process according to any one of claims 1 to 10, wherein the vacuum pressure is less than 10 ^{~ 6} mbar.

12. Machine for assembling a first substrate (1) with a second substrate (2) characterized in that it comprises:

- a vacuum chamber (12), 0 - a deposit module (7) of a layer ^"(5) a thin bonding material, on a first surface (3) of the first substrate (1),

a deposition module (8) of a thin layer (6) of the same material on a second surface (4) of the second substrate (2),

means (13) for bringing said first surface (3) and said second surface (4) into contact,

^~ - a ^'means (13) of ^pre' ng ^"" said first surface ^~ ^(~ 3) against said second surface (4) 0 - a cryogenic plant to achieve and maintain in the enclosure (12) a negative temperature.

13. Machine according to claim 12, wherein said deposit modules (7, 8) are capable of depositing thin layers (5, 6).

Of identical thicknesses.

14. Machine according to claim 12 or 13, further comprising a cryogenic plant for reaching and maintain in the enclosure (12) a temperature below - 150 ⁰ C.

15. Machine according to any one of claims 12 to 14, wherein the means (13) for pressing is capable of applying a pressure at least equal to 45 pascal +/- 3%.

16. Machine according to any one of claims 12 to

15, further comprising at least one vacuum pump capable of producing in the chamber a vacuum pressure less than

1 (T ⁶ mbar.

17. Machine according to any one of claims 12 to

16, comprising at least one pair of pressure rollers (13) capable of pressing two substrates (1, 2) of flexible sheet material.

18. Machine according to claim 17, comprising a first pair of guide rollers (14), at least one pair of pressure rollers (13) and a cryogenic module adapted to regulate the temperature of the guide rollers (14) to -150 ⁰ C +/- 10 ⁰ C and the temperature of the pressure rollers (13) at -150 ° C +/- 2 ^° C.