WO2011135195A1

WO2011135195A1 - Power supply support for electronic devices

Info

Publication number: WO2011135195A1
Application number: PCT/FR2010/000764
Authority: WO
Inventors: Fabrizio Maseri; Philippe Guaino; Ludovic Avril
Original assignee: Arcelormittal Investigación Y Desarrollo Sl
Priority date: 2010-11-16
Filing date: 2010-11-16
Publication date: 2011-11-03

Abstract

The invention relates to a metal power supply support that is especially suitable for electronic devices. Said metal power supply support comprises a metal substrate coated successively by: a dielectric smoothing coating that has a thickness of more than 500nm and a surface roughness Ra lower than, or equal to, 10nm, and comprises at least one inorganic layer deposited by a vacuum deposition technique, and at least one organic layer deposited by a technique other than the vacuum deposition technique; and a conductive layer.

Description

Power supply for electronic devices

The present invention relates to a power supply for electronic devices of the type comprising a coated metal substrate, particularly suitable for integration into organic devices, but also inorganic devices.

In the context of the present invention, an electronic device is understood to mean any device comprising components such as, for example, light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), transistors or sensors, but also any device comprising photovoltaic cells thin film or not, and any device including viewing screens such as TFT ("thin-film transistor"), for example.

The use of a metal substrate for this type of support has the advantage of having good thermal conductivity which allows the heat of the electronic device in operation to be more easily dissipated. However, the use of such a substrate requires the use of a dielectric smoothing coating whose role is on the one hand to isolate the conductive substrate from the rest of the electronic device and on the other hand to reduce the roughness of the substrate, source of electrical faults.

It is known from US Pat. No. 6,755,249 to use a combination of a smoothing layer formed of a glass applied in liquid form (so-called Spin-On-Glass or SOG technology) and a dielectric insulation layer formed of an oxide or a metal nitride such as SiO ₂ , SiN _x or SiON.

It is also known from EP 1 612 040 to use a dielectric smoothing coating formed of a plurality of layers of a hybrid organic-inorganic sol-gel, of composition close to SiO ₂ . However, the existing solutions do not offer sufficient electrical insulation, which can guarantee the absence of electrical faults on surfaces of several centimeters square. The manufacturing efficiency of electronic devices based on these existing solutions is greatly impacted, resulting in the disposal of many devices.

The object of the present invention is to overcome the drawbacks of the prior art and to provide an electronic device supply support which may be suitable for organic and inorganic devices and which makes it possible to improve the production yield of these electronic devices as well as their durability.

For this purpose, the first object of the invention is a metallic feed support for an electronic device comprising a metal substrate successively coated:

a dielectric smoothing coating with a thickness greater than 500 nm, having a surface roughness Ra of less than or equal to 10 nm and comprising at least one inorganic dielectric layer deposited by a vacuum deposition technique and at least one organic dielectric layer; deposited by a technique other than a vacuum deposition technique,

and a conductive layer.

The feed support according to the invention may further comprise the following optional features, taken alone or in combination:

the metal substrate comprises at least one sheet consisting of a metal or a metal alloy such as steel,

said metal substrate has a roughness Ra of between 2 nm and 0.2 μm,

the inorganic dielectric layer comprises a material selected from ceramics and non-conductive metal oxides, the organic dielectric layer comprises a material selected from polyimides, organo-inorganic hybrid lakes and epoxies,

the organic dielectric layer is deposited by a method selected from photolithography, screen printing, flexigraphy, ink jet printing, centrifugation, dipping, extrusion, roller application,

the conductive layer comprises a material selected from metals, conductive metal oxides, conductive metal nitrides and conductive metal carbides,

the conductive layer consists essentially of silver,

the conductive layer has a reflectivity of at least 90%,

the conductive layer has a thickness of between 10 and 300 nm,

the dielectric coating comprises a primary layer comprising a nonconductive metal oxide,

the primary layer has a thickness of between 10 and 500 nm,

the dielectric coating comprises a topcoat comprising a non-conductive metal oxide,

the topcoat has a thickness of between 10 and 500 nm. A second subject of the invention consists of an electronic device incorporating a support according to the invention.

Particular embodiments of the invention will now be described by way of non-limiting examples, with reference to FIGS. 1 and 2:

FIG. 1 is a sectional view of a support according to one embodiment of the invention,

- Figure 2 illustrates the measurement of manufacturing efficiency. It shows a plan view and a sectional view of a sample prepared for manufacturing yield measurement.

The same reference numbers represent the same elements in each of the figures. If we first consider Figure 1, we see a first embodiment of a feed support 10 according to the invention, consisting of a metal substrate 1 steel successively carrying a dielectric coating smoothing 2 and a conductive layer 3. The smoothing dielectric coating is formed of an inorganic dielectric layer 4 and an organic dielectric layer 5.

As will be understood, the feed support according to the invention is essentially composed of a metal substrate covered with a dielectric smoothing coating composed of at least one organic dielectric layer and at least one inorganic dielectric layer itself covered with a conductive coating composed of one or more layers as well.

Various types of metal substrates may be suitable for a device according to the invention. Preferably it is a solid body of flat shape, that is to say of small thickness compared to its other dimensions. The substrate may be in the form of a plate or sheet made of a single metallic material or a composite assembly. In the latter case, the substrate is a superposition of several layers of the same material or of different materials, at least one of which is a metallic material, this superposition being able to be realized, for example, by gluing, by welding, by galvanizing with hot, by electrogalvanization, by vacuum deposition.

Preferably the metallic material is a metal alloy such as steel. According to the application and the required performances, it will be possible to resort without this list being exhaustive with black iron, with galvanized steel, with steels covered with a zinc alloy comprising 5% by weight of Aluminum (Galfan®), to steels coated with a zinc alloy comprising 55% by weight of aluminum, about 1.5% by weight of silicon, the remainder consisting of zinc and unavoidable impurities due to elaboration (Aluzinc®, Galvalume®) to steels coated with an aluminum alloy comprising from 8 to 1% by weight of silicon and from 2 to 4% by weight of iron, the remainder being composed of aluminum and unavoidable impurities due to the preparation (Alusi®), steels covered with a layer of Aluminum (Alupur®), to stainless steels.

In a preferred embodiment, the surface portion of the substrate used in the invention has a relatively high roughness Ra and between 0.02 pm and 0.2 pm. This roughness may be that adjusted during the manufacture of the metal strip by mechanical and / or thermal methods known to those skilled in the art. Advantageously, it will not be necessary to add an additional step to the conventional processes for manufacturing these materials. This relatively large roughness can make it possible to simply ensure better adhesion of the dielectric smoothing coating which will naturally fill the numerous surface asperities, thus achieving a stronger bonding of these two essential elements of the invention. In addition, the use of such a substrate makes it possible not to have to rectify its surface by expensive mechanical methods.

In another preferred embodiment, a substrate having a rougher Ra roughness of between 2 nm and 20 nm, which can be obtained by a mechanical polishing process, for example, will be selected. Such roughness makes it possible to reduce the number of defects existing on the surface of the substrate and thus to minimize the risk of electrical faults of the device.

According to a variant of the invention, the coated substrate may be curved and retain, of itself, a curved shape.

Depending on the nature and thickness of the layers that can compose it, this substrate will be rigid or flexible.

The metal substrate thus carries a smoothing dielectric coating necessarily comprising an organic dielectric layer and an inorganic dielectric layer.

The main function of this dielectric smoothing coating is to enable the metal substrate to be electrically insulated to prevent current flowing between the conductive layer and the substrate. In particular, the present It has surprisingly been found by inventors that by combining dielectric layers of different types and deposited by different techniques, it was possible to obtain satisfactory electrical insulation at any point on the surface of the supply medium. Without wishing to be bound by any scientific theory, it seems that the addition, on a given layer of nature and presenting a defect, of a layer of different nature and deposited by a different technique makes it possible to plug the defect. In the case where the same deposited layer would be used in the same way, the surface energy at the level of the defect would cause the propagation of the defect in the second layer, maintaining in fact the electrical fault of the smoothing dielectric coating.

This dielectric smoothing coating also serves to compensate for the roughness of the metal substrate and to provide a regular surface for the deposition of the upper conductive layer. This regularity is quantified through the surface roughness Ra which must be less than or equal to 10 nm, preferably less than or equal to 8 nm and more preferably less than or equal to 2 nm.

In fact, it has been found that, in compliance with such a surface condition, the conductive layer subsequently deposited on the dielectric smoothing coating itself has a smooth surface, free of structural and morphological defects, improving on the one hand the contact with the parts of the electronic device to be powered and secondly the reflectivity of the conductive layer when it is metallic.

Furthermore, the dielectric smoothing coating also serves to constitute a protective barrier of the electronic device vis-à-vis particles and diffusing elements from the metal substrate and a protective barrier of the metal substrate vis-à-vis external contaminations, whether water vapor or oxygen that can oxidize or corrode the metal substrate. The inorganic dielectric layer comprises a material chosen from ceramics such as, for example, cordierite, forsterite or steatite or from non-conductive metal oxides such as, for example, ΤΊΟ ₂ , Al ₂ O ₃ , S1O2, optionally doped with boron or phosphorus. This inorganic dielectric layer is applied at least partially to the substrate, optionally coated, by means of any known method of depositing thin layers under vacuum, among which may be mentioned by way of example, the following techniques: Physical Vapor Sputtering Deposition magnetron, Ion Beam Assisted Deposition, Sputter Ion Plating, Jet Vapor Deposition, Plasma Assisted Chemical Vapor Deposition.

The organic dielectric layer comprises, in turn, a polymeric material chosen from thermoplastic polymers or thermosetting polymers, elastomers, polyimides, epoxies, polyolefins, polyamides, cellulosic materials, styrenic materials, polyacrylic materials, such as polymethyl methacrylate, polyethers, saturated polyesters, vinyl materials, such as polyvinyl acetate, poly-sulfonic materials, fluorinated polymers, organo-inorganic hybrid lakes based on sol-gel technology . This organic dielectric layer is applied at least partially to the substrate, optionally coated, by means of any known method of thin film deposition other than a vacuum deposition method. Examples that may be mentioned include photolithography, screen printing, flexigraphy, ink jet printing, centrifugation or spin-coating, dipping, extrusion, application by possibly etched rolls, by blade. .

The dielectric smoothing coating is formed by alternately depositing any number of organic dielectric layers and inorganic dielectric layers, it being understood that the first deposition may be indifferently that of an organic dielectric layer or that of an inorganic dielectric layer.

Depending on the number of dielectric layers, the dielectric smoothing coating may have a thickness ranging between 500 nm and 50 μητι. The chosen thickness will not be less than 500 nm to obtain the insulation and the required barrier function. According to a preferred embodiment, the alternation of the layers constituting the smoothing dielectric coating begins with an inorganic dielectric layer, called the primary layer, preferably formed of a non-conductive metal oxide. The function of this primary layer is to improve the adhesion of the dielectric coating while partially compensating for the roughness of the metal substrate. Preferably, this primary layer has a thickness between 10 and 500 nm.

According to another preferred embodiment, the alternation of the layers constituting the smoothing dielectric coating terminates in an inorganic dielectric layer, called a finishing layer, preferably formed of a non-conductive metal oxide. The function of this topcoat is to improve the wettability of the dielectric coating to ensure better adhesion of subsequently deposited layers such as the conductive layer or an encapsulation adhesive. Preferably, the topcoat has a thickness between 10 and 500 nm.

Advantageously, the surface of the metal substrate may be degreased and / or cleaned before the deposition of the dielectric coating, for example by pickling by means of a reactive plasma, or by UV-Oxygen-rich ozone treatment.

When necessary, an adhesion promoter may advantageously be present between the substrate and the dielectric coating, comprising, for example, HMDSO, a silane, a thiol or a chromate.

Finally, the feed support according to the invention comprises a conductive layer which constitutes its upper surface, above the smoothing dielectric coating.

The primary function of this layer is to allow the power supply of electronic devices that will be placed in contact with all or part of this layer. For this purpose, the conductive layer has a resistance per square of less than 10 Ω, preferably less than 5 or less than less than 1 Ω; more preferably it has a resistance per square of at most 0.1 Ω. Typically, resistance value per square means the value of the resistance between two opposite sides of an imaginary square formed on the surface of the layer whose resistance is measured.

This layer may comprise one or more metals or metal alloys and / or one or more oxides, nitrides or metal carbides naturally conductive or made conductive by additions of conductive elements such as graphite, for example. It may comprise, for example, an element selected from the group consisting of Ag, Al, Au, Mo and Cr. It may itself consist of several sub-layers. It can be applied by means of a method for depositing thin layers under vacuum, among which may be mentioned by way of example, the following techniques: Physical Vapor Sputtering-magnetron deposition, Ion Beam Assisted Deposition, Sputter Ion Plating, Jet Vapor Deposition, Plasma Assisted Chemical Vapor Deposition.

The thickness of the conductive layer is preferably in the range 10 - 300 nm to allow a sufficient electrical power to be conveyed according to the electronic device under consideration. In addition to providing high conductivity to the coated substrate, the conductive layer, when not transparent, can achieve high reflectivity values of at least 90%; preferably at least 92 or 95%, more preferably at least 96 or 97%. This property is particularly advantageous when the support according to the invention is used to power a device comprising a light source such as a light emitting diode, because it optimizes the energy efficiency of the electronic device.

In these various embodiments, the dielectric smoothing coating and the conductive layer substantially cover the entire surface of the metal substrate, but it is also possible to texture each of the concerned layers by adding or removing material in places, to meet the specific needs of the electronic device concerned.

Such texturing can be achieved, for example, by photolithography, dry etching, wet etching, laser, masking, inkjet printing, roller printing, screen printing.

In order to illustrate the invention, tests have been carried out and will be described by way of non-limiting examples of the invention.

Roughness

The surface roughness is defined by the Ra value (average arithmetic roughness) measured by AFM (Atomic Force Microscopy) or optical profilometry. Surface resistance

The surface electrical resistance is measured by means of a Quadpro 302 test bench, which consists of 4 electrodes aligned and separated by a constant distance of 1 mm interpointe. A constant current is applied on two electrodes and the potential on the other two electrodes is measured with a voltmeter. The surface electrical resistance, otherwise known as square resistance, is directly read on the device.

reflectivity

Reflectivity is measured by means of an integrating sphere. A beam of a given wavelength incident with an angle of 8 ° is reflected by the sample whose reflectivity is to be measured and then integrated by the sphere and measured via a spectrometric sensor. Wavelength scanning between 250nm and 2500nm makes it possible to establish a total average reflectivity, a diffuse average reflectivity and a specular average reflectivity.

Adhesion of the coating The adhesion of the coating to the metal substrate is determined in accordance with the "Quick Adherence Test" according to ASTM D 3359-02.

Manufacturing performance measurement

The measurement of manufacturing efficiency is illustrated in Figure 2.

In the context of a first test, a sample of metal substrate 1 whose surface is 100 × 100 mm is first prepared and which is covered with the dielectric smoothing coating 2, but not the conductive layer.

A series of nine rows of nine square studs 6 formed of the conductive layer having a 10 mm side and regularly distributed over this surface is produced by vacuum evaporation.

A voltage of 10 V is then applied between the substrate and each metal pad and the current flowing in the stack of dielectric layers, which is similar to a leakage current, is measured. The current value measured at the surface of the stud is then reported.

For a given block, the electrical insulation of the stud is considered satisfactory when the measured leakage current is less than 10 mA / cm ² .

The electrical insulation of all of the metal feed support tested is considered satisfactory when all the pads have a leakage current of less than 10 mA / cm ² . This is called a 100% manufacturing yield.

In the context of a second test, a sample of metal substrate 1 whose surface is 150 × 150 mm is first prepared and which is covered with the dielectric smoothing coating 2, but not the conductive layer.

Vacuum evaporation is carried out with 4 large blocks of 130 × 29 mm distributed uniformly over the sample.

The evaluation criteria of the manufacturing yield are identical to the case of the first test. Resistance to heat treatment

This test consists in measuring a second time the production yield after having subjected the substrate covered with the dielectric coating and the pads uniformly distributed metal, heat treated at different temperatures, per oven residence for 164 hours.

The coated substrate is said to have satisfactory heat treatment resistance, when after 164 hours at 150 ° C the manufacturing yield remains above 95%.

Breakdown voltage

The breakdown voltage corresponds to the voltage applied to the device causing the destruction of the device and thus the increase of the leakage current.

The metal substrate sample is prepared as in the case of measuring the production yield.

A voltage of 220V is then applied between the substrate and each metal pad and the leakage current is measured. If the value of the latter remains lower than 10 mA / cm ² , the breakdown voltage of the device is considered sufficiently high.

Example 1

A coated metal substrate particularly suitable for organic electronic devices is formed, in order:

an SS8ND stainless steel substrate marketed by ArcelorMittal, having a roughness Ra of approximately 5 nm obtained by electropolishing,

an inorganic dielectric layer of SiO 2 approximately of thickness, called the primary layer, deposited by PACVD,

an organic dielectric layer mainly formed of polyimides (reference PI2562 from Dupont Electronics), having a thickness of about 2 μm, a roughness Ra of 4 nm, and deposited by centrifugation,

a second inorganic dielectric layer of SiO 2 approximately 50 nm thick, called the finishing layer, deposited by PACVD and having a roughness of 4 nm, a continuous conductive layer of silver about 100 nm thick deposited by PVD.

Example 2

an organic dielectric layer mainly formed of polyimides (reference PI2562 of Dupont Electronics), having a thickness of approximately 2 μητι, a roughness Ra of 4 nm, and deposited by centrifugation,

an inorganic dielectric layer of Al ₂ O ₃ approximately 100 nm thick, called a finishing layer, deposited by PVD sputtering-magnetron and having a roughness of 4 nm and

a continuous conductive layer of silver about 100 nm thick deposited by PVD. Example 3

a 304 2R stainless steel substrate marketed by ArcelorMittal, having a roughness Ra of approximately 20 nm,

a primary layer of Si0 ₂ approximately 50 nm thick, deposited by PACVD,

an organic dielectric layer mainly formed of an organo-inorganic hybrid lacquer based on sol-gel technology (reference HS1.1 Nanoxid from Matrio), having a thickness of approximately 5 μιτι, a roughness Ra of 9; nm and deposited by centrifugation, a topcoat of Al ₂ O 3 approximately 100 nm thick, deposited by PVD sputtering-magnetron and having a roughness of 4 nm and,

a continuous conductive layer of silver approximately 100 nm thick, deposited by PVD sputtering-magnetron.

The various supports described in the examples according to the invention were subjected to a battery of tests whose results are collated in the following table:

As will be understood from the description of the description, the feed support according to the invention has many advantageous properties, among which may be mentioned in particular:

it may be suitable for a variety of electronic devices, it has a very low leakage current, which makes it possible to improve the efficiency of the electronic device,

it is not necessary to mechanically polish the substrate so that it is suitable as a substrate for electronic devices,

it can offer, thanks to the dielectric smoothing coating, a protection against the diffusion of elements migrating from the substrate towards the heart of the device, in particular when it comes to inorganic devices, the low roughness makes it possible to offer a good operation of the electronic device,

a high reflectivity makes it possible to offer a good performance to the electronic device.

Claims

claims

1. Metallic supply support (10) for an electronic device comprising a metal substrate (1) successively coated:

a dielectric smoothing coating (2) with a thickness greater than 500 nm, having a surface roughness Ra of less than or equal to 10 nm and comprising at least one inorganic dielectric layer (4) deposited by a vacuum deposition technique and at least one organic dielectric layer (5) deposited by a technique other than a vacuum deposition technique,

- and a conductive layer (3).

2. The metal support (10) of claim 1 wherein the metal substrate (1) comprises at least one sheet consisting of a metal or a metal alloy such as steel.

3. metal support power supply (10) according to any one of the preceding claims wherein said metal substrate (1) has a roughness Ra between 2nm and 0.2μιη.

The metal feed carrier (10) according to any one of the preceding claims wherein said inorganic dielectric layer (4) comprises a material selected from ceramics and non-conductive metal oxides.

The metal feed carrier (10) according to any one of the preceding claims wherein said organic dielectric layer (5) comprises a material selected from polyimides, organo-inorganic hybrid lakes and epoxies.

A metal feed carrier (10) according to any one of the preceding claims wherein said organic dielectric layer (5) is deposited by a method selected from photolithography, silkscreen, flexigraphy, inkjet printing, centrifugation, dipping, extrusion, roller application.

The metal power carrier (10) according to any one of the preceding claims wherein said conductive layer (3) comprises a material selected from metals, conductive metal oxides, conductive metal nitrides and conductive metal carbides.

The metallic power support (10) according to any one of the preceding claims wherein said conductive layer consists essentially of silver.

9. metal support (10) according to any one of the preceding claims wherein said conductive layer (3) has a reflectivity of at least 90%.

10. metal support power (10) according to any one of the preceding claims wherein said conductive layer (3) has a thickness between 10 and 300 nm.

The metal power support (10) according to any one of the preceding claims wherein said dielectric coating (2) comprises a primer layer comprising a nonconductive metal oxide.

12. The metal support (10) of claim 11 wherein said primary layer has a thickness between 10 and 500 nm.

The metal feed carrier (10) of any preceding claim wherein said dielectric coating (2) comprises a topcoat comprising a nonconductive metal oxide.

14. The metal support (10) of claim 13 wherein said topcoat has a thickness of between 10 and 500 nm.

An electronic device incorporating a metal power support (10) according to any one of the preceding claims.