KR20130097755A - Method for encapsulating an electronic arrangement - Google Patents

Abstract

The present invention relates to a method for encapsulating an electronic device with respect to a transmissive material, wherein the method
Providing a sheet-like structure comprising at least one pressure-sensitive or hot melt adhesive that can be activated by heat;
Applying the sheet-like structure at least around the areas to be encapsulated of the electronic device on a substrate supporting / comprising the electronic device;
Providing a cover to the electronic device and to an adhesive at least surrounding the electronic device, in which adhesive is in contact with the cover; And
Then thermally activating the adhesive in at least one partial region of the cover surface, thereby forming at least a bond of the substrate and the cover, in which case the heat necessary for activation is actually at least surrounding the adhesive. Occurs within the sheet-like structure itself.

Description

Method for encapsulating electronics {METHOD FOR ENCAPSULATING AN ELECTRONIC ARRANGEMENT}

The present invention relates to a method for encapsulating an electronic device.

(Opto-) electronic devices are being used more and more frequently in commercial products or are just entering the market. Such devices include inorganic or organic electronic structures, for example organic, metal organic or polymer semiconductors or combinations thereof. The devices and products are rigidly or flexibly formed depending on the desired application, and there is a growing demand for flexible devices. The manufacture of such devices is for example by printing methods such as letter press printing, gravure printing, silk screen printing, flat printing or for example thermal transfer. By so-called "non impact printing" such as thermotransfer printing, ink jet printing or digital printing. For example, chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma growth chemical or physical vapor deposition (PECVD), sputtering, (plasma-) etching or vaporization and The same vacuum methods are used in various ways, in which case the structuring is generally done by a mask.

Examples for (photo-) electron applications that have already attracted attention commercially or in their market potential include electrophoretic or electrochromic structures or inorganic or polymers in displays, indicators and display-devices. Electroluminescent lamps, referred to as light emitting diodes (OLEDs or PLEDs) or lighting devices, Light-Emitting Electrochemical Cells (LEEC), organic solar cells, preferably dye- or polymer solar cells, inorganic Solar cells, preferably thin film solar cells based on silicon, germanium, copper, indium and selenium, organic field effect transistors, organic switching elements, organic optical amplifiers, organic laser diodes, organic or inorganic sensors, or organic or An RFID-transponder with an inorganic foundation is cited.

As a technical challenge in the field of inorganic and / or organic (opto-) electronic devices, particularly in the field of inorganic (opto-) electronic devices, the technical challenges for achieving sufficient lifetimes and functions of (opto-) electronic devices Mention may be made of techniques for protecting the elements contained within them from permeable materials. Permeable materials can be many low molecular organic or inorganic compounds, in particular water vapor and oxygen.

As such, there is a particular need for flexible adhesive solutions that function as a transmission barrier to block permeable materials such as oxygen and / or water vapor in inorganic and / or organic (photo-) electronic devices, particularly organic (photo-) electronic devices. do. In addition there are a number of additional requirements for such (opto-) electronic devices. The flexible adhesive solution should not only enable good bonding between two substrates, but also high shear strength and peel strength, chemical stability, stability against aging, high transparency, and simple processing. Possibilities, and properties such as high flexibility and warpability must also be met additionally.

As such, one approach according to the prior art is to place the electronic device between two substrates that are impermeable to water vapor and oxygen. Subsequently, sealing takes place in the edge region. For structures that are not flexible, glass or metal substrates are used that provide a high permeation barrier but are very resistant to mechanical loads. Such substrates also result in a relatively large thickness of the overall device. In the case of metal substrates there is also no transparency at all.

Alternatively for flexible devices, planar substrates are used, such as transparent or non-transparent thin films, which can also be implemented in multiple layers. In this case, inorganic or organic layers as well as combinations of various polymers can be used. The use of such planar substrates allows for a flexible yet extremely thin structure.

Basically different substrates are suitable for various applications, for example thin films, fabrics, nonwovens and paper or combinations of the materials described above.

In order to reach as good a seal as possible, special barrier adhesives are often used. Adhesives that are good for sealing (opto-) electronic devices have low permeability to oxygen and especially water vapor, have sufficient adhesion on the device, and can flow well over the device. Lack of adhesion on the device results in reduced barrier action at the interface, thereby allowing oxygen and water vapor to enter regardless of the properties of the adhesive. Only when there is continuous contact between the material and the substrate, the material properties become a factor in determining the barrier action of the adhesive.

To characterize the barrier action, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) are typically indicated. Each transmittance then dictates the flow rate of oxygen or water vapor flowing through the membrane over area and time under inherent conditions of temperature and partial pressure, and optionally under additional measurement conditions such as relative humidity. The lower the values, the better suited the individual materials are for encapsulation. The indication for the permeate material here is not only based on the values for WVTR or OTR, but also always includes an indication of the average flow path length of the permeation, such as the standardization or thickness of the material for a particular flow path length.

Permeability (P) is a measure of the likelihood of permeation of the body to gases and / or liquids. Low P-values characterize good barrier action. Permeability (P) is a high value for a defined material and for a defined permeable material when conditions are fixed at a particular permeate path length, partial pressure and temperature. Permeability (P) is the product of the diffusion-term (D) and the soluble-term (S): P = D * S.

Said soluble-term (S) in this case describes the affinity of the barrier adhesive for the permeable material. In the case of steam, for example, the value for S of hydrophobic materials is low. The diffusion-term (D) is a measure of the motility of the permeable material in the barrier material and directly depends on properties such as molecular motility or free volume. Often cross-linking is strong or in the case of highly crystalline materials, a relatively low value for D is reached. However, high-crystalline materials generally have low permeability and relatively stronger crosslinks result in relatively lower flexibility. The permeability (P) typically rises with increasing molecular motility, that is to say when the temperature rises or the glass transition point is exceeded.

Approaches to increase the barrier action of the adhesive must take into account the above two parameters (D and S), especially with regard to their effect on the permeability of water vapor and oxygen. In addition to these chemical properties, the effects of physical influences on the permeability, in particular average transmission path length and interface properties (flow properties of the adhesive, adhesion), must also be considered. Ideal barrier adhesives have low D- and S-values when the adhesion state on the substrate is very good.

The low solubility-term (S) is mostly insufficient to reach good barrier properties. One traditional example therefor is in particular a siloxane-elastic polymer. The materials are extremely hydrophobic (small soluble-terms) but have a relatively low barrier to water vapor and oxygen by their freely rotatable Si-O bonds (large diffusion-terms). In other words, a good balance between soluble-term (S) and diffusion-term (D) is essential for good barrier action.

Currently, liquid adhesives and adhesives based on epoxides, among others, are used as barrier adhesives (WO 98/21287 A1; US 4,051,195 A; US 4,552,604 A).

The materials have a low diffusion-term (D) by strong crosslinking. The main field of use of these materials is in the field of edge bonding of rigid devices, but is also used in suitably flexible devices. The curing process may be by heat or by UV-rays. Adhesion over the entire surface is only possible due to shrinkage phenomena caused by curing, since stresses are generated between the adhesive and the substrate during the curing process, which in turn can cause peeling.

The use of such liquid adhesives involves a series of disadvantages. Thus, low molecular weight components (VOC-Volatile Organic Compounds) can damage the sensitive electronic structures of the device and make processing difficult in manufacturing. In the case of such an adhesive, the process of applying the adhesive to each individual component of the device is inevitably complicated. To ensure accurate positioning, installation of expensive distributors and fixtures is essential. Such application methods also interfere with rapid and continuous processes, and also due to the low viscosity by the subsequent required lamination step, it may be difficult to reach the defined layer thickness and adhesion width within narrow limits. .

In addition, such high-cross bonding adhesives have only low flexibility after the curing process. The use of a heat-crossing coupling system is limited in the low temperature range or, in the case of a two-component system, by pot life, more specifically by the processing time until sealing is achieved. do. In the high temperature range and especially in the case of long reaction times, sensitive (opto-) electronic structures again limit the possibility of using such systems-the maximum applicable temperature in (opto) electronic structures is often 90 ° C. This is because preliminary damage can already occur from this temperature. In this case particularly flexible devices comprising organic electronic devices and encapsulated with a transparent polymer thin film or encapsulated with a combination of a polymer thin film and an inorganic layer set narrow limits. This also applies to the lamination step under high pressure. In order to achieve improved durability, in this case the step of applying a high temperature load has been omitted, and lamination is preferably done at lower pressures.

Preference is given to using a pressure-sensitive or hot melt adhesive for the purpose of sealing such (opto-) electronic structures. The use of pressure sensitive adhesives is known in the prior art (eg US 2006/0100299 A1, WO 2007/087281 A1, US 2005/0227082 A1, DE 10 2008 047 964 A, DE 10 2008 060 113 A). . In the prior art it is preferred to use a pressure sensitive adhesive which can be activated by energy provided after adhesion (eg actinic radiation or heat) (US 2006/0100299 A1, WO 2007/087281 A1), The reason is that the barrier action of such adhesives can be improved, in particular by cross-linking reactions caused by the provided energy.

The use of hot melt adhesives is also known in the prior art. In the prior art, copolymers of ethylene are frequently used, such as ethylene-ethylacetate (EEA), ethylene-acrylic acid-copolymer (EAA), ethylene-butylacrylate (EBA) or ethylene-methylacrylate (EMA). Particularly for solar cell modules based on silicon wafers, crosslinking ethylene-vinylacetate- (EVA) -copolymers are generally used. The crosslinking then takes place under pressure during the sealing process and at temperatures above approximately 120 ° C. The process is disadvantageous for many (opto-) electronic structures based on organic semiconductors or manufactured by thin film methods due to mechanical loads or high temperatures due to pressure. However, in JP 2002 260 847 A the process also appears for organic light emitting diodes.

Further hot melt adhesives based on block copolymers or functional polymers are disclosed in US Pat. No. 5,488,266 A, WO 2008/036707 A2, WO 2003/002684 A, JP 2008 004 561 A, JP 2005 298 703 A and It is described in US 2004/0216778 A1. It is known that even in such hot melt adhesives, the properties of such adhesives can be improved, for example by cross-linking reactions caused by energy provided in the form of actinic radiation or heat (eg WO 2008/036707 A, WO 2003/002684 A, JP 2005 298 703 A, US 2004/0216778 A1).

The disadvantage with the pressure-sensitive or hot melt adhesives used in the prior art is that the barrier action is lower than in the case of epoxide adhesives, in particular when the crosslinking is not done in advance, in particular the barrier action against oxygen is lower. And when the temperature is relatively higher, the cohesion of the adhesive is severely lowered. This also increases the risk of bubbles forming when the structure is stored in the presence of moisture and heat.

Typically, the physical effect that results in internal bonding of a substance or mixture of substances due to intermolecular and / or intramolecular interactions is termed "cohesion". Thus, the cohesive force determines the adhesion and flowability of the adhesive, which is determined approximately by viscosity and by shear durability. In order to increase the cohesion of the adhesive as intended, the adhesive is often subjected to an additional crosslinking process, in which the adhesive is added reactive (and thereby crosslinkable) components or other chemical crosslinkers. Or the adhesive is exposed to radiation which ionizes as a post treatment.

Typically, the physical effect of integrating the two states due to intermolecular interactions occurring at the interface of the two states in contact with each other is referred to as "adhesion". Thus, the adhesion determines the adhesion of the adhesive on the substrate surface, which can be determined as gripping adhesion potential (so-called "tack") and as adhesion. In order to affect the adhesion of the adhesive as intended, the adhesive is added with a softener and / or a resin that enhances adhesion (so-called "tackifier"). The adhesion technical properties of one adhesive are first determined by the ratio of cohesive and cohesive properties. Thus, for example, for some applications it is desirable for the adhesive used to have a high agglomeration property, more particularly to a particularly strong internal bonding state.

In contrast, when the adhesive is crosslinked by heat, heat must be transported through the structure to the glue joint. In this case, in general, temperatures inevitably present a risk of damage to the electronic structure. It is also difficult to provide limited heat only to the area to be bonded. For example, if heat is provided through a polymer thin film by a heat stamp, in order to keep the heating time as short as possible, the heat stamp must be much hotter than the temperature to be reached at the adhesive seam. Such a situation may not only damage the polymer thin film and the barrier layer of the polymer thin film which is often necessary for such an application, but may also damage the electronic structure by the horizontal heat flow. The difficulty of locally limiting the inflow of heat corresponds to one alternative method of introducing heat (e.g., by IR-radiation or by convection with hot gases), especially before joining the adhesive seam.

Pressure-sensitive or hot melt adhesives that are cross-linked by radiation present again the disadvantages of the possibility of damage that the electronic structure can be damaged by radiation and the necessity that one part of the structure must be able to transmit radiation. . In particular, many of the components of the organic electronics and the polymers used are sensitive to UV-loads, making it impossible to use them continuously for long periods of time without other additional protective measures such as additional cover films. Do. The cover thin film can only be provided after the UV-curing process in the case of a UV-curable adhesive system, which further increases the complexity of the manufacturing and the thickness of the device. The difficulty of limiting the energy supply locally also applies to cross-linking by radiation. The use of masks creates a solution, but in mass production it is technically complex.

US 6,706,316 B2 shows a process for ultrasonically sealing an organic light emitting diode by melting a low-melt metal alloy. For this purpose, a metal is inserted between the substrate and the cover as a wire, and pressurization is carried out with ultrasonic waves provided the pressure is very high, from 2,900 MPa to 14,500 MPa. Due to the metallic nature of the sealing material, very high temperatures can occur at the adhesive seam. In addition, due to the high pressures required, the method cannot be applied to polymer substrates. In the publication itself only glass, metal and ceramic are explicitly stated. Moreover, due to the electrical conductivity of the sealing material, an electrically insulating layer is essential in the structure.

US 6,195,142 B1 describes a similar sealing process using solder made of low-melt glass, metal or liquid-crystal-polymer (LCP). Such solders have similar drawbacks as those described above. For example, when working with glass substrates and glass covers, the exposure to sound waves can reach very long 20 to 30 seconds. PET is mentioned in this case as a possible flexible substrate and the cover is made of steel or glass. Epoxy resins, polyimide resins and other polymeric adhesives in this publication have apparently been found to be less suitable.

The unavoidable high temperatures in these two methods also imply the risk of damaging the electronic structure by the thermal conduction process required by the high thermal conductivity of the substrate- or cover material.

In US 6,803,245 B2, ultrasonic bonding for encapsulating electronic devices is mentioned as an alternative to adhesive bonding, but not for activating the adhesive.

DE 103 09 607 A1 proposes a method for encapsulating functional elements of an electrical component, in which a capsule disposed on the functional elements is hermetically coupled to the substrate by ultrasonic welding. In one preferred embodiment of the method, it is possible to place an ultrasonically weldable sealing material between the substrate and the capsule before ultrasonic welding. However, it is preferable that the thermoplastic plastics can be welded not only to the substrate but also to the capsule, and the thermoplastics themselves may be welded to each other by ultrasonic waves. The disadvantage of ultrasonic welding is that, in order to enable molecular penetration (interdiffusion) of materials common to melt bonding, as in all welding methods, two bonding partners must be converted to the molten liquid state at their interface. Is that. Where such molecular penetration is not possible due to the incompatibility of the material, welding aids are often used in terms of bonding. The welding aids are generally converted completely into a molten liquid state at the time of welding, and likewise can be interdiffused at two interfaces with a bonding partner interface in the form of a melt. In this respect, ultrasonic welding is indistinguishable from other welding methods. A disadvantage in ultrasonic welding is that in this method the coupling partner can be damaged at its own interface or, if the thin film is thin, even in the entire cross section of the coupling partner. This situation is particularly true when a polymer thin film with an inorganic barrier layer is used for encapsulation purposes, resulting in a leak hazard at the welding site.

The sealing material described in DE 103 09 607 A1 can be selected from glass solders and adhesives, in which case epoxy resins are explicitly mentioned as adhesives. Disadvantages of using an adhesive such as an epoxy resin are the necessity of dosing the correct amount of adhesive present in fluid or paste form and the necessity of avoiding the flow of adhesive during ultrasonic welding. In the case of ultrasonic welding, a high pressure must be provided to introduce negative energy into the structure, so that the situation where the liquid adhesive squeezes out from the weld seam can hardly be avoided.

The sealing material may also be selected from flexible organic polymer thin films or thermoplastics used as welding aids. The choice in this case, unlike the adhesives described above, can be made according to the compatibility of the two bonding partners and the sealing material to ensure interdiffusion. Thus, the selection has been severely limited. In addition, there is a risk of damage to the encapsulation material previously described in the method.

It is an object of the present invention to present an improved method for encapsulating electronic devices, in particular for permeable materials such as water vapor and oxygen, which can be carried out simply and quickly and attain a good encapsulation state. In addition, in the process according to the invention the life of the (opto-) electronic devices must be prolonged by using particularly flexible and suitable adhesives.

The problem is solved by the method described in the independent claims. Preferred embodiments of the method are subject of the dependent claims.

Accordingly, the present invention relates to a method for encapsulating an electronic device with respect to a transmissive material, wherein the method according to the invention

Providing a sheet-like structure comprising at least one pressure-sensitive or hot melt adhesive that can be activated by heat;

Applying the sheet-like structure at least around the areas to be encapsulated of the electronic device on a substrate supporting / comprising the electronic device;

Providing a cover to the electronic device and to an adhesive at least surrounding the electronic device, in which adhesive is in contact with the cover; And

Then thermally activating the adhesive in at least one partial region of the cover surface, thereby forming at least a bond of the substrate and the cover, in which case the heat necessary for activation is actually at least surrounding the adhesive. Either in the sheet-like structure itself or at the interface of the substrate and / or cover and the adhesive.

In one alternative method for encapsulating an electronic device with respect to a transmissive material, a cover is provided in the electronic device that supports at least an adhesive surrounding the electronic device, in which case the adhesive is at least in contact with the substrate.

Encapsulation in this case means not only wrapping the entire circumference with the sheet-like structure described above, but also locally applying the sheet-like structure to the area to be encapsulated of the (opto-) electronic device, for example one side of the electronic structure. It also means covering the structure or framing the electronic structure.

By transmissive material in the sense of the present specification are those chemicals (eg, atoms, ions, molecules, etc.) that can penetrate into the device or part, in particular into an electronic or optoelectronic device or a corresponding part and cause particularly functional disturbances here. Is mentioned. Such a penetration phenomenon may be made by, for example, the housing or the sheath itself, but in particular by the opening in the housing or the sheath or by a sewing place, a bonding place, a welding place, or the like. In this context, a housing or sheath is understood as parts which completely or partially enclose sensitive components so as to serve in addition to the mechanical function of the components, in particular for the purpose of protecting the components themselves.

Permeable materials in the sense of the present specification are especially low molecular organic or inorganic compounds such as hydrogen (H ₂ ), very particularly oxygen (O ₂ ) and water (H ₂ O). The permeable materials may in particular be present in gaseous form or in vapor form.

The present invention does not surprisingly recognize that measures for generating heat inside the adhesive, as described in detail below, have no disadvantageous effects on the electronic device, in particular not heating the electronic device itself to an extent that may be mentioned or It's based on the amazing perception that it's not damaging at all. In this case, in the method claimed herein, unlike the prior art described in publication DE 103 09 607 A1, even the entire volume of the adhesive is heated in order to form an adhesion or to strengthen the adhesion state. In addition, by the method proposed in the present invention, the quality of encapsulation can be remarkably improved compared to the conventional heating method.

In the process according to the invention, it is preferred that the heat is actually limited only to the adhesive surface. Since heat is generated in the sheet-like structure itself, heating only needs to be made to the activation temperature. In a method based on heat conduction, heat radiation or convection, the temperature gradient and, in addition to the excess temperature, which are absolutely necessary for uninterrupted heat transfer can be omitted entirely. Thus, the heating time can be kept short, and the heat flow in the transverse direction-above all else in the direction of the electronic element-can be strongly limited.

In addition, there is no need to take special measures to generate heat not only on the electronic structure and the substrate but also on the cover side, more specifically contacting measures for supplying current, rather than simply adding a sheet-like structure containing an adhesive. It is also desirable that the heat can be generated in cooperation with external technical measures for generating heat inside the adhesive.

In the prior art, by means of electrical resistive heating, by means of exothermic chemical reactions or physical phase transition (eg of crystallization) that can realize heat generation within the sheet-like structure itself, Different and suitable mechanisms are known in which heating takes place by absorption of actinic radiation, by magnetic induction or as a result of interaction with a high frequency electric field such as microwave radiation, for example.

In this case, chemical reactions and physical phase transitions generally result in inherent (volume-related) heat generation that is rarely sufficient for technically available adhesive activation. Electrical resistance heating requires defined electrically conductive materials (such as conductors or conductive adhesives embedded within the adhesive) and external contacts for supplying current as part of the sheet-like structure. High frequency heating and microwave heating are materials within a specially adapted sheet-like structure that are frequency matched and have a sufficiently high dielectric loss factor or correspondingly specially adapted adhesives (eg based on polyamide or polyvinylchloride). Need. This fact significantly limits material selection. In addition, in microwave heating, it is also difficult to limit the radiation to only the region to be heated. There is also a high risk of damage to electronic devices by microwaves.

As such, it is particularly desirable to generate heat by ultrasonic waves in a sheet-like structure containing at least an adhesive. Such a method is known for other applications described in WO 2009/021801 A1.

Ultrasonic welding is a method for joining plastics. In this way only thermoplastics can be welded basically without corresponding connecting elements. This method achieves permanent bonding only if the thermoplastics are sufficiently friendly with each other. Where non-friendly or non-thermoplastic materials have to be bonded to one another, it is known to place welding aids, such as polymer thin films, between the bonding partners, which realize the bonding of the material bonding mode. As in other welding methods, at the welding- or bonding site the material must be activated by energy supply, for example to be melted. In the case of ultrasonic welding, the necessary energy is generated by mechanical high frequency vibration. The main feature of this method is that the energy necessary for welding in the weld assembly is generated by molecular- and / or interface friction or by interface vibrations occurring within the part or in welding aids.

In the method proposed here, ultrasonic heating of the adhesive is carried out. In this method, unlike ultrasonic welding, heat is hardly generated at the interface, but is actually generated by hysteresis loss in the adhesive material itself, which is encouraged by a high mechanical damping coefficient tan δ.

The ultrasonic devices required for this purpose actually consist of the following groups of parts:

-Generator

Vibration formers (sonotrode)

Anvil

The ultrasonic frequency is generated by the generator. Generators convert line voltage to high voltage and high frequency. By means of the shielded cable the electrical energy is transmitted to the ultrasonic transducer, to the so-called converter. The converter generally operates in accordance with a piezoelectric effect, in which the properties of certain crystals that expand and contract when an alternating magnetic field is applied are used. Due to this characteristic, mechanical vibration is generated, which is transmitted to the sonotrode (so-called welding horn) through the amplitude converting member. The magnitude of the vibration amplitude can be influenced by the amplitude converting member. Vibration is generally transmitted to a workpiece inserted and fixed between the sonorod and the anvil used as a counterpart, under a pressure of 2 MPa to 5 MPa, in which the necessary heat is generated for activation.

The local temperature rise causes the adhesive to begin to soften, and the mechanical damping coefficient rises. Increasing the damping coefficient results in additional heat generation, which ensures an automatically accelerated reaction effect. According to the invention, the adhesive is activated very quickly in this way, which fact contributes to very short cycle times and thus often to high economic efficiency.

It is also preferred that the heating is structurally very clearly limited because heating occurs only in the area of the sonotrode surface in contact with the binder.

After cooling, the adhesive bonding state is firm. Since the sonotrode is permanently exposed to ultrasonic vibrations, the level of demand for the material is very high. Therefore, most of them are carbide coated titanium.

The method is often characterized by high economic efficiency because the time of exposure to sound waves is very short. As such, the preferred time for exposure to sound waves is in the range of 0.1 to 3 seconds.

In order to be able to shorten the time exposed to sound waves, it is preferable to set a power of at least 3 W / mm ² bonded surfaces.

Eventually, the sheet-like structure causes permanent bonding between the substrate and the cover, so that any materials different from each other can be joined to each other by the above method.

Surprisingly, even if the electronic device is present under the sono-rod, but not in contact with the sono-rod, it appears that no damage to the electronic device occurs. This situation arises, for example, in the form of a frame in which the sonotrode surface in contact with the assembly is formed in a frame shape, and a groove is engraved into the sonotrode surface in the center of the frame, resulting in the presence of the electronic device upon pressurization of the sonotrode rod. This occurs regularly when the engaging region becomes unable to contact the small note rod.

In order to protect the cover surface in contact with the sonotrode from mechanical damage, a protective thin film (sacrificial thin film) is preferably inserted between the cover and the sonotrode or the contact surface of the sonotrode itself is elastomeric or viscoelastic. Is coated with the material.

In order to keep the risk of surface damage as low as possible, it is desirable to set a power of less than 0.5 W / mm ² adhesive side.

0.5 W / mm ² , on the one hand, to keep the risk of surface damage as low as possible, and on the other hand, to keep the exposure time to sound waves as short as possible. It is preferable to set the power of the 3 W / mm ² adhesive surface.

Accordingly, the desired ultrasonic energy obtained from the product of the time of exposure to sound waves and the power provided is 0.05 J / mm ^2. To 9 J / mm ² adhesive side.

In one particularly preferred embodiment of the method, the ultrasonic energy is directed to a circulating process through a sonotrode that can be rolled up like a roll. Corresponding techniques for exposing to ultrasound are known in the art of ultrasonic welding.

It is also particularly desirable to generate heat by magnetic induction in at least the sheet-like structure containing the adhesive. This method is known for the other applications described in EP 1 453 360 A2.

Compared to the ultrasonic heating method, the induction heating method does not require direct heating of the sheet-shaped structure between the external heating device and the sheet-shaped structure or the cover or the substrate, and such heating can be performed even in a contactless manner. Has an advantage. In this respect the contact state according to the invention of the substrate and the cover and the sheet-like structure can also be achieved, for example, by loosely arranged layers up and down. Providing power (compression of the bond seam) to create a tighter and longer lasting bond can be made later in subsequent steps.

The incorporation of an inductor into at least one pressing tool is also a preferred variant of the method because it allows the induction field to be very close to the site of adhesion, This is also because the space can be limited to the bonding site.

Different effects can contribute to the heating made in the magnetic- alternating magnetic field: If the body inserted into the alternating magnetic field for heating has conductive regions, eddy currents are induced into the regions by the magnetic- alternating magnetic field. At this time, if the regions have an electrical resistance different from zero, the eddy current-power loss generated at this time causes the generation of Joule heat (Joule effect). However, in order for such eddy currents to be mainly formed, the conductive regions must have a minimum size; The larger the size of the conductive regions, the smaller the frequency of the magnetic alternating magnetic field applied from the outside.

However, if the body inserted into the alternating magnetic field for heating has ferromagnetic regions, the unit magnets of the regions are each aligned parallel to the external magnetic- alternating magnetic field. Hysteresis losses (polar reversal losses) that occur during fluctuations in external magnetic fields likewise result in heating of the body. Depending on the material of the body inserted into the magnetic alternating magnetic field, the two effects can together contribute to the heating of the body (in the case of ferromagnetic metals such as iron, nickel and cobalt or Mu-metal and alnico In the case of ferromagnetic alloys such as A (Alnico) or only one of the two effects, respectively, can contribute to heating (ie only non-ferromagnetic metals, such as aluminum, with eddy currents or iron oxide particles). Only hysteresis for materials with low electrical conductivity).

If a sheet-like structure that can be bonded in a thermally activated manner is thermally activated by an induction heating method, a sheet-like structure containing an adhesive, which is generally bonded in a thermally activated manner, is used, and this adhesive is used for the electrical conductive layer. On the side, it is arranged on the side of the sheet-like structure with a thin film made of metal or metal deposited polymer, perforated metal thin film, wire net, flat formed metal mesh, metal nonwoven or metal fiber. The latter, non-continuous sheet-like structures offer the advantage that the internal bonding of the sheet-like structure as a whole is improved by the adhesive being able to penetrate the openings in the individual sheet-like structure, but this advantage is later achieved in terms of heating efficiency. At the cost of downsizing.

In recent years, induction heating has attracted new attention in the case of adhesion. The reason is that from the available nano-particulate systems such as MagSilica® (Evonik AG), which can be inserted inside the material of the body to be heated, thereby heating the body over the entire volume of the body. It can be found that in this case the mechanical stability of the body is not damaged to the extent of mention by heating. As MagSilica® a small amount of iron oxide-particles surrounded by silicon dioxide is used.

Thus, for example, an adhesive band named Duplocoll RCD® can be purchased from Lohmann, which contains inductively heatable nanoparticles inside the adhesive. The key is the collaboration between the magnetic field and MagSilica®.

When an adhesive containing MagSilica® is exposed to a rapidly changing magnetic field, the iron oxide particles begin to vibrate, similar to a compass needle. Heat is then generated in the adhesive as intended, and the adhesive quickly cures later. Since the components no longer need to be heated, such a process saves valuable heating energy, and the manufacturing process is also significantly accelerated throughout.

Basically various heating devices for induction heating are known; The heating devices are distinguished from one another according to the frequency of the magnetic- alternating magnetic field generated by the individual heating devices, among others. Thus, induction heating uses a magnetic field having a frequency in the frequency range of about 100 Hz to about 200 kHz (so-called intermediate frequency; MF) or a frequency in the frequency range of about 300 kHz to about 100 MHz (so-called high frequency; HF). This can be done.

However, due to the small size of the nanoscopic systems, it is impossible to efficiently heat such products in a magnetic- alternating magnetic field having a frequency selected from the intermediate frequency range. Rather, new systems require frequencies in the high frequency range. At these frequencies, however, the risk of damage to electronic components in the magnetic alternating field is clearly evident. Moreover, the generation of magnetic- alternating magnetic fields with frequencies in the high frequency range adds to the device cost, thereby adversely affecting the economy.

Therefore, it is desirable to use a frequency that is in the middle frequency range. Surprisingly, it has been found above all else that organic electronic devices are not heated or otherwise damaged within the aforementioned frequency range.

In order to obtain the high processing speeds required for industrial manufacturing processes, the heating period of sheet-like structures that can be bonded in a thermally activated manner should be very short. Therefore, it is preferable to use a heating time of 0.1 second to 10 seconds.

In order to reach the required adhesion temperature, it is necessary to select a heating rate very high. However, if a sheet-like structure that can be bonded in a thermally activated manner is bonded between bonding partners with only low thermal conductivity, that is to say between bonding partners with thermal conductivity of up to 5 W / mK, the sheet Heat generated in an inductive manner in the form structure cannot be released quickly enough from the sheet form structure. Rather, heat is initially maintained within the adhesive surface for several hours, so that heat accumulation occurs within the adhesive surface. As a result, not only the sheet-like structure but also the coupling partners may be locally heated and damaged. This risk of overheating is further increased when the coupling partners have low effective thermal capacity in addition to low thermal conductivity, because these causes do not provide the possibility of temporary heat storage. Both causes arise, for example, in the case of binding partners with polymers on the adhesive surface.

As such, a pressure (compression force) of at least 1 MPa, in particular at least 3 MPa, is simultaneously provided to the substrate, sheet-like structure and cover by induction heating perpendicular to one side section of the sheet-like structure to which it can be bonded in a thermally activated manner. As a result, the method by which the adhesive is brought into contact with the adhesive substrate over the entire surface is preferred. In this case the direction indication “vertical to one side section of the sheet-shaped structure which can be bonded in a thermally activated manner” means that the sheet-shaped structure is flat (and therefore both sides of the sheet-shaped structure are also flat). Compressive force acts (at least also) perpendicularly to the main inflation of the sheet-like structure for flat adhesion, and conversely, compressive force for the three-dimensional bent adhesion This means that one of the main inflation portions acts in a vertical direction with respect to one inflation portion and thus acts perpendicularly to the side of the sheet-like structure in at least one partial region.

The process according to the invention can be carried out using induction heating means (derivatives) customary for induction heating. As induction heating means (derivatives), all conventional and suitable devices are mentioned, and more specifically, coils, conductor loops or the like, which generate a self- alternating magnetic field of suitable intensity due to the flowing current and are flowed by an alternating current. Conductors are mentioned. Thus, the magnetic field strength required for heating can be provided by a coil device having a corresponding number of windings and a coil length, that is to say by a coil device which is perforated by a corresponding current and formed, for example, as a point derivative. The coil device may be formed without a ferromagnetic core or may have a core made of, for example, iron or compressed ferrite powder. The conjugate may be directly exposed to the magnetic field generated as above. Alternatively, it is of course also possible to arrange the coil arrangement as a primary winding on the primary side of the magnetic field transformer so that the secondary winding on the secondary side of the magnetic field transformer can supply a correspondingly higher current. As a result, the original exciter coil placed directly near the assembly can have fewer windings due to the higher current, thereby reducing the magnetic field strength of the magnetic- alternating magnetic field.

Another particularly preferred embodiment of the induction heating method is that the risk of damaging the inorganic barrier layer previously present inside the substrate and / or the cover by a very short heat pulse generated from the inside of the adhesive is sustained for a relatively long time by the barrier thin film. Significantly less than in the case of conductive heating or in the case of mechanical ultrasonic heating.

As the substrate material for the electronic device, a metal thin film, a polymer thin film, a thin film binder or a thin film or a thin film binder provided with an organic and / or inorganic layer is preferably used. Such thin film / thin film combinations may consist of conventional metals and / or plastics used for the manufacture of thin films, for example, the following materials may be mentioned but are not limited to such materials: steel , Aluminum, copper, polyethylene, polypropylene-especially oriented polypropylene (OPP), cyclic olefin copolymers (COC; Cyclic Olefin Copolymer), polyvinyl chloride (PVC), polyester In particular polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbo Nate (PC), Polymethylmethacrylate (PMMA), Polyamide (PA), Polyethersulfone (PES) or Polyimide (PI).

The substrate material may also be combined with an organic or inorganic coating or layer. Such combinations can be made by conventional methods such as, for example, lacquer coating, printing, vaporization, sputtering, co-extrusion or lamination. Oxides or nitrides of silicon and aluminum, indium-tin-oxides (ITO) or sol-gel-coatings may also be mentioned by way of example but not by way of limitation.

Particularly preferably the thin film / thin film combination, in particular the polymer thin film, is provided with a permeable material barrier for oxygen and water vapor, in which case the permeable material barrier exceeds the requirements for packaging applications (WVTR <10 ⁻¹ g / (m ² d); OTR <10 ^-1 cm ³ / (m ² d bar), in particular WVTR <10 ^-2 g / (m ² d); OTR <10 ^-2 cm ³ / (m ² d bar)) .

Permeability to oxygen (OTR) and permeation to water vapor (WVTR) are determined according to DIN 53380 Part 3 (OTR) or ASTM F-1249 (WVTR). Oxygen permeability is measured at a temperature of 23 ° C. and a relative humidity of 50%. Water vapor permeability is determined at a temperature of 37.5 ° C. and a relative humidity of 90%. The results are normalized to a thin film thickness of 50 μm.

The method according to the invention provides, among other things, the advantage of minimizing the possibility of damaging the layer structure blocking the heat introduction and, in addition, the permeation material only for the thin films provided with the barrier layer as described above.

In addition, the thin film / thin film combination is preferably transparent in shape such that the entire structure of such an electronic structure can also be formed transparently or at least light can reach the interior of the electronic structure or can be emitted from the electronic structure. Can be formed. The expression “transparent” here means that the average transmission in the visible range of the light detected according to ASTM D 1003 at a wavelength of 400 to 800 nm is at least 75%, preferably at least 85%. The transparency or transmittance of an object depends on the extinction coefficient of the object, its reflection on the surface and the wavelength of light used for inspection. The extinction coefficient is specific to the material and depends on the absorption of the material used. In order to obtain a material with high transmittance, reflection as well as absorption must be prevented.

Reflection occurs at all surface and material boundaries. The reflection depends on the one hand on the surface roughness and on the other hand on the refractive index of the material used. On rough surfaces, additional scattered reflection occurs. The relationship between the reflection at the interface and the refractive index of adjacent layers is described by Fresnel-Equation. In the special case where transparent materials are used, light is incident vertically, and the influence of the wavelength can be neglected, the Fresnel-Equation is simplified as follows:

R = (n ₂ -n ₁ ) ² / (n ₂ + n ₁ ) ² Equation 1

In the above equation

R = reflection at the interface

n ₁ = refractive index of medium 1

n ₂ = refractive index of medium 2

1The refractive index of _air is n _air

One

Reflections occur at all boundaries, reducing the transmission coefficient of an object. Thus, considering the fact that the light follows the law of reflection according to Fresnel, not only when light enters the film, but also when it comes out of the film, a polyester film can reach maximum as long as the refractive index n ₂ = 1.6. The transmittance that can be exceeded may not exceed a value of 90%.

Preferably, not only the adhesive but also the support thin film is transparent, and the adhesive and support thin film preferably have a transmission greater than 60%, especially as the adhesive thin film is detected according to ASTM D 1003 at a wavelength of 400 to 800 nm. To be formed, in particular having a transmission greater than 85%.

So far, only 'transmission' is briefly described and generally expressed in% means the ratio of the optical power reaching the front of the body irradiated by the light to the front of the light. The transmission is subtracted by reflection and absorption.

More specifically, the following equation applies:

Transmittance = (1-reflectivity-absorbance).

As the cover, basically the same thin film or thin film combination as used in the substrate material can be used. In this case, the substrate and cover in the assembly containing the electronic structure may be different. For example, since both sides of the combination often do not need to be transparent, the capsule can be formed from one transparent substrate and one non-transparent cover.

As described above, since the substrate material and the cover are often made of a composite material that cannot be joined by a welding method (such as ultrasonic welding or induction welding), in the prior art, hot melt- or pressure-sensitive sheet-like structures have already been bonded. Often used for.

The present invention combines the advantages of heat generation within the sheet-shaped structure itself with the advantages of adhesive bonding, which surprisingly simplifies the process of material selection and processing compared to the use of liquid adhesives or weld auxiliary thin films, and encapsulates the capsule. Synergistic effects such as an excessively high quality increase occur. Particularly by the use of pressure sensitive adhesives, complex positioning- and fixing measures are omitted when joining the layer combination.

The method according to the invention which comprises a sheet-like structure / layer material comprising at least one activatable adhesive and subsequently in contact with the substrate or cover, wherein the activatable adhesive is for example coated, printed, sprayed or co-extruded It also includes a method provided to the substrate or cover by a method of forming a layer such as. A combination of an adhesive and a substrate or cover provided and actuable in this manner is known, for example, as a hot sealing thin film in the packaging field, and can also seal electronic structures such as, for example, thin film PECHM-1 from Peccel Technologies, Japan. Already used for this purpose.

In one preferred feature of the invention the sheet-like structure is provided in a pre-bond containing a substrate- or cover material. For example, the substrate and sheet-like structure may be pre-coupled before providing the electronic device to the substrate. Alternatively, cover and sheet-like structures may first be provided in the preliminary combination and then placed over the electronic device. Methods for preparing the preconjugates are known to those skilled in the art, for example lamination, coating, printing, spraying or co-extrusion methods can be used.

As sheet-like structures in the sense of the present application, in particular all conventional and suitable structures which are actually expanded in planar form are effective. Such structures enable flat adhesion and can be formed in a variety of ways, in particular flexibly formed as adhesive thin films, adhesive bands, adhesive labels or die molded bodies. The sheet-shaped structure may be formed as a sheet-shaped structure cut to size, and the shape of the sheet-shaped structure is adapted to the shape of the adhesive surface to reduce the risk of the electronic device being damaged by heat during the heating process.

In the sense of the present application the sheet-shaped structures each have two sides, one front side and one back side. The terms front and back are related to two surfaces of the sheet-shaped structure parallel to the direction of the main expansion (surface expansion, main expansion plane) of the sheet-shaped structure, and by the selection of such terms The absolute spatial placement of the surface is not determined but only used to distinguish the two surfaces disposed on opposite sides of the sheet-like structure; Thus, if the front side can be the side of the sheet-shaped structure that lies spatially behind, the rear side can correspondingly form the side of the sheet-shaped structure which lies spatially ahead.

The sheet-like structure that can be bonded in the heat activated manner adheres the adhesive substrate to the cover. To this end, the sheet-like structure has an adhesive which is thermally activated on at least one of its two sides, and preferably even with such adhesive on both sides. The thermally bonded adhesives are all adhesives that are bonded by elevated temperatures at elevated temperatures and provide a bond that can accommodate mechanical loads after cooling. Typically the adhesive is in the form of an adhesive layer. In other words, in the simplest case, the sheet-like structure consists of only one layer of heat-activated adhesive that adheres the substrate and the cover to its two sides.

As a layer, a device in the form of a plane is described, in particular a functional unit, in which the dimensions (thickness or height) in the spatial direction of the device are measured in two different directions (length and width) which define the main expansion. Much smaller than). Layers of this type may be formed in a compact or continuous manner and may consist of only one material or may be made of different materials, in particular when contributing to the uniform function of the layer. One layer may have a constant thickness over its entire surface expansion or may have a different thickness. Furthermore, one layer may naturally have more than one function.

A structure composed of one layer as above is particularly preferred for ultrasonic heating due to its simplicity. In order to form ultrasonic heating in particular efficiently, it is preferred if the activatable adhesive has a mechanical loss factor (tan δ) of at least 0.1 at a temperature of 23 ° C. and a frequency of 1 Hz.

The difference detected at a temperature of 23 ° C. and a frequency of 1 Hz, in order to avoid heating the substrate or cover intrinsically in the ultrasonic heating itself.

tan δ _adhesive —tan δ _{substrate or cover} is preferably at least one.

Loss factors for polymers, for example hot melt adhesives, are detected by a torsional vibration test according to DIN 53445 at a temperature of 23 ° C. and a frequency of 1 Hz.

The loss factor for the pressure sensitive adhesive is determined by an oscillatory shear test (Dynamic Mechanical Analysis, DMA) under torsional load at a temperature of 23 ° C. and a frequency of 1 Hz. This test is used to examine the fluid properties and is described in detail in the arms (Pahl et al. "Practical Rheology of Plastics and Elastomers", VDI-Publisher, 1995, pages 57-60 and pages 119-127). have. The test is carried out under torsional loads in Ares' shear rate controlled flowmeter, in which case a plate-plate-structure with a plate diameter of 25 mm is used.

The monolayer structure of the sheet-like structure can also be used for induction heating. For this purpose, the activatable adhesive preferably has an electrical conductivity of at least 20 MS / m at a temperature of 23 ° C., a situation which is hardly attainable by inherently conductive polymers, but by filling conductive fillers Can be reached. The electrical conductivity is detected according to ASTM D 2739-97 at a temperature of 23 ° C. and a relative humidity of 50%. Alternatively or additionally, the adhesive can be made ferromagnetic, anti-ferromagnetic or paramagnetic by adding particles, in particular the nanoparticles described above.

The sheet like structure according to the invention preferably comprises at least three different layers, ie at least one electrically conductive layer and at least one heat activated adhesive layer and one further adhesive layer for induction heating. The additional adhesive layer may be the same as or different from the at least one adhesive bonded in the heat activated manner. Thus, the further adhesive layer may comprise, for example, an adhesive which is bonded in a heat activated manner or may even comprise a pressure sensitive adhesive which cannot be activated by heat.

In principle, the at least one electrically conductive layer can be suitably formed, for example as a whole surface-compact or as a continuous thin layer (for example as a grating). It is preferred if the thickness of the electrically conductive layer is less than 50 μm, in particular less than 20 μm or even less than 10 μm. If the thickness of the electrically conductive layer is less than 10 μm, the heating rate can be limited in a relatively simple manner upwards.

The electrically conductive layer can be made of all conventional and suitable materials, for example aluminum, copper, gold, nickel, mu-metals, alnico, permalloy, ferrite, carbon-nanotubes, graphene ) And the like. The electrically conductive layer is then preferably formed further magnetically, in particular ferromagnetically or paramagnetic. The electrically conductive layer advantageously has an electrical conductivity of at least 20 MS / m (corresponding to a resistivity of less than 50 mΩ · mm ² / m), in particular 40 MS / m (corresponding to a resistivity of less than 25 mΩ · mm ² / m). it has an electrical conductivity of at least m, wherein the values were determined for 300 K each.

In addition to the at least one electrically conductive layer, the sheet-like structure may of course also have additional electrically conductive layers; The additional electrically conductive layers can be the same as the at least one electrically conductive layer or can be different from the at least one electrically conductive layer.

Overall, sheet-like structures that can be bonded in the thermally activated manner can be arbitrarily suited. Thus, the sheet-like structure may comprise further layers in addition to the layers described above, for example a permanent support or a temporary support.

In order to reach sufficient adhesive strength when the thickness is thin, the adhesive layers should preferably have a thickness of 5 μm to 20 μm. On the other hand, thicknesses of 100 to 500 μm are preferred for particularly strong adhesive bonds.

As adhesives adhered in at least one thermally activated manner, in principle all conventional adhesive systems adhered in a thermally activated manner can be used. Adhesives that are bonded by thermal activation are in principle divided into two categories: thermoplastic adhesives (melt adhesive) bonded by thermal activation and reactive adhesives (reactive adhesive) bonded by thermal activation. This classification also includes adhesives in both categories, ie reactive thermoplastic adhesives (reactive melt adhesives) that are bonded in a thermally activated manner.

Thermoplastic adhesives are based on a polymer that reversibly softens on heating and solidifies again during cooling. In contrast, reactive adhesives that are bonded in a thermally activated manner contain reactive components. The reaction components are also referred to as "reaction resins" in which the crosslinking process is initiated by heating, and the crosslinking process ensures a permanently stable bond even under pressure after the crosslinking reaction is finished. Such thermoplastic adhesives preferably also contain elastic components such as synthetic nitrile rubber. Such elastic components provide particularly high dimensional stability under pressure to adhesives bonded in the thermally activated manner due to their high flow viscosity.

In the following some typical systems of adhesives which are bonded in a thermally activated manner are described purely by way of example, which adhesives have been found to be particularly preferred in connection with the present invention.

Thermoplastic adhesives bonded in a heat activated manner contain a thermoplastic base polymer. The thermoplastic base polymer already has good flow properties even at low pressing forces, so that the final adhesive force associated with the durability of permanent bonds can be set within a short pressing time, so that rough or otherwise critical Fast adhesion is possible even on the ground. As the thermoplastic adhesive bonded in a heat activated manner, all thermoplastic adhesives known in the prior art can be used.

Adhesives that can be activated by heat as described, for example, in DE 10 2006 042 816 A1 are suitable, but it is not desired that the present invention be limited by this disclosure.

EP 1 475 424 A1 describes compositions as examples. Thus, the thermoplastic adhesives may contain, for example, one or more of the following components or may consist of such components: polyolefin, ethylene-vinylacetate-copolymer, ethylene-ethylacrylate- Copolymers, polyamides, polyesters, polyurethanes or butadiene-styrol-block copolymers. The thermoplastic adhesives described in paragraph [0027] of EP 1 475 424 A1 are preferably used. EP 1 956 063 A2 describes further thermoplastic adhesives which are particularly suitable for a particular field of use, such as the adhesion of adhesive substrates made of glass, for example. Thermoplastic adhesives are preferably used which have a melt viscosity which is elevated by fluid additives, for example the melt viscosity of such thermoplastic adhesives can be exothermic silicic acid, carbon black, carbon-nanotubes and / or additional polymers. It is raised by adding it as a mixed component.

The reactive adhesive, which is otherwise bonded in a thermally activated manner, preferably comprises an elastomeric base polymer and a modified resin, in which case the modified resin comprises an adhesive resin and / or a reactive resin. The use of elastomeric base polymers results in adhesive layers having excellent dimensional stability. As reactive adhesives bonded in a thermally activated manner, adhesives bonded in all thermally activated manners known in the art may be used corresponding to specific individual applications.

The reactive adhesive adhered in the thermally activated manner may be a derivative of the nitrile rubber such as for example a nitrile rubber or a mixture (blend) of the base polymer further containing a nitrile butadiene rubber or a reactive resin such as, for example, a phenol resin. Also included are reactive thin films that are bonded in a thermally activated manner as a basis; Such a product is commercially available under the name 'tesa 8401'. The nitrile rubber provides excellent dimensional stability to the thermally bonded thin film due to its high flow viscosity, thereby achieving high adhesion on the plastic surface after the crosslinking reaction is carried out.

Other reactive adhesives that are bonded in a thermally activated manner, such as adhesives containing polymers capable of bonding up to 50 to 95% by weight and containing up to 5 to 50% by weight of epoxy resins or mixtures of multiple epoxy resins, may also be used. Of course it can be used. Wherein the adhesive polymer preferably contains up to 40 to 94% by weight of an acrylic acid compound and / or a methacrylic acid compound having the general formula CH ₂ = C (R ¹ ) (COOR ² ) (wherein R ¹ is Residues selected from the group comprising H and CH ₃ , and R ² is a residue selected from the group comprising linear or branched alkyl chains having 1 to 30 carbon atoms and H), 5 to 30 weight Up to-% contains a first copolymerizable vinyl monomer having at least one acid group, in particular a carboxylic acid group and / or a sulfonic acid group and / or a phosphonic acid group, up to 1 to 10% by weight of at least one epoxide group Or a second copolymerizable vinyl monomer having an acid anhydride group, and from 0 to 20% by weight of the functional group of the first copolymerizable vinyl monomer and the second Claim for the polymerization a vinyl monomer different from the functional group having at least one functional group comprises a vinyl monomer capable of copolymerization 3. By enabling such adhesives to quickly activate adhesives that already reach their final adhesion in a short time, the result is a guarantee of a bond that can be excellently adhered to nonpolar ground as a whole.

Additional usable reactive adhesives that are bonded in a thermally activated manner that provide particular advantages contain up to 40 to 98 weight-% of block copolymers containing acrylate, up to 2 to 50 weight-% of resin components, And from 0 to 10 wt-% contains curing agent components. The resin components contain one or more resins selected from the group comprising epoxy resins (making adhesive), novolak resins and phenolic resins that increase adhesion. The curing agent components are used to crosslink a resin consisting of a resin component. Such formulations offer the unique advantage that due to the strong physical crosslinking inside the polymer, it is possible to obtain adhesive layers having a greater overall thickness without adversely affecting the load acceptability of the adhesive as a whole. As such, the adhesive layers are particularly suitable for compensating for the non-flatness of the ground. Moreover, such adhesives have good durability against aging and only low gas release properties, which are particularly desirable properties for many adhesions in the field of electronic devices.

However, as already mentioned above, in addition to the particularly preferred adhesives as described above, in principle all other adhesives which are bonded in a thermally activated manner corresponding to the respective required profile for adhesion can also be selected and used.

In order to encapsulate the (opto-) electronic structure, an adhesive system which is bonded in a heat activated manner having a low water vapor transmission rate or a low oxygen transmission rate is preferably used. Such activatable adhesives are for example EP 0 674 432 A1, US 2006/0100299 A1, WO 2007/087281 A1, DE 10 2009 036 970 A, JP 2005 298 703 A, EP 1 670 292 A and Known from US 2007135552 A. It is known to those skilled in the art that in such publications, for example, adhesive systems that can be activated by actinic radiation, for example by UV-rays, can easily be activated by heat with the addition of a corresponding initiator such as a peroxide.

WVTR is less than 100 g / m ² d, in particular less than 10 g / m ² d and / or OTR is less than 8,000 cm ³ / m ² d bar, especially less than 3,000 cm ³ / m ² d bar, and very particularly Adhesive systems that are less than 100 cm ³ / m ² d bar are preferred.

It is desirable to provide a collecting material for the permeable material (eg oxygen, water vapor) in the adhesive systems, since the time for the permeable material to pass through the adhesive seam by the collecting material can be significantly extended. Such materials are known to those skilled in the art, for example by names such as getters, scavengers or desiccants and are described, for example, in US Pat. No. 6,936,131 (B2).

Very particular preference is given to collecting materials having collection properties that can be activated thermally or mechanically. The expression 'thermally or mechanical activation' can then be understood as, for example, chemical or physical transformation, destruction of the coating material or the release and / or release reaction of previously collected permeates. Such measures have the advantage that such trapping materials can be treated in an atmosphere containing water vapor, in which case the capacity of the permeate to be captured in the final structure is not very limited. For example, microencapsulated collectors can be obtained.

If a compressive force is provided to the assembly during induction heating, a further crimping device is required for this operation. As a crimping device, any device suitable for exerting a crimping force may be used, for example, a crimping machine or a crimping roller that operates discontinuously, such as a pneumatic or hydraulic press, an eccentric press, a crank press, a toggle lever press, a spindle press, or the like. A crimping machine that operates continuously, such as may be used. The device may be provided as a separate unit or may be present in connection with a derivative. Preferably an apparatus is used which comprises at least one pressing die element as a first crimping tool, which also has induction heating means. In this way, the induction field can be very close to the bonding site to be formed, thereby allowing it to be spatially limited only to the surface of the bonding site.

Further details, objects, features and advantages of the invention are described in detail below with reference to preferred embodiments.
1 is a schematic diagram of a first (photo-) electronic device,
2 is a schematic diagram of a second (photo-) electronic device,
3 is a schematic representation of a third (photo-) electronic device.

1 shows a first shape of the (opto-) electronic device 1. The device 1 has a substrate 2 on which an electronic structure 3 is arranged. The substrate 2 itself was formed as a barrier for the transmissive material, thereby forming a part of the capsule of the electronic structure 3. In this case an additional cover 4 formed as a barrier over the electronic structure 3 is arranged spaced apart from the electronic structure.

At least one pressure-sensitive or hot melt that can be activated by heat to encapsulate the electronic structure 3 also to the side and at the same time to connect the cover 4 to the electronic device 1 as well A sheet like structure comprising an adhesive 5 is provided on the substrate 2 to enclose the periphery next to the electronic structure 3. The sheet-like structure 5 connects the cover 4 to the substrate 2. The sheet-like structure 5 can also separate the cover 4 from the electronic structure 3 by the shape of the corresponding thickness.

As the sheet-shaped structure 5, hot melt adhesives based on crosslinked vinyl aromatic compound copolymers are used, for example, as described in detail in the examples below. In this case the sheet-like structure 5 not only functions to connect the substrate 2 to the cover 4 but also to encapsulate the electronic structure 3 also against the permeable material such as water vapor and oxygen from the side as well. It is also responsible for forming a barrier layer for the permeable material.

In this case the sheet like structure 5 is provided in the form of a molded body perforated from a double-sided adhesive band. Such perforated shaped bodies allow particularly simple application. In addition, in the case of heating, the electronic device is not directly damaged.

2 shows one alternative shape of the (opto-) electronic device 1. The electronic structure 3 is again shown, which is arranged on the substrate 2 and encapsulated from below by the substrate 2. The sheet-like structure 5 is then arranged over the entire surface above and on the side of the electronic structure. Thus, the electronic structure 3 is encapsulated by the sheet like structure 5 in the places. A cover 4 was then provided on the sheet like structure 5. The cover 4 does not necessarily meet a high barrier demand level, unlike the previous shape, since the barrier is provided in advance by the sheet-like structure. The cover 4 may, for example, only perform a mechanical protective function, but may additionally also serve as a barrier material. The heating of the sheet-like structure 5 in this arrangement not only comprises a whole layer of adhesive, but also may alternatively comprise a part of the surface, for example an area not covering the electronic structure.

3 shows one further alternative shape of the (opto-) electronic device 1. Unlike the previous shapes, two sheet-like structures 5a and 5b are provided at this time, which in this case are identically formed but may be different. The first sheet-like structure 5a is arranged on the substrate 2 over the entire surface. An electronic structure 3 was then provided on the first sheet-like structure 5a, which is fixed by the sheet-like structure 5a. The combination of the sheet-like structure 5a and the electronic structure 3 is then covered over the entire surface by the further sheet-like structure 5b, as a result of which the electronic structure 3 is removed from all sides. Encapsulated by sheet-like structures 5a and 5b. Then a cover 4 was again provided on the second sheet like structure 5b. In this arrangement, the sheet-like structure 5a or 5b may alternatively be heated intrinsically, or two sheet-like structures may be inherently heated.

Therefore, in the above shape, the substrate 2 and the cover 4 do not necessarily have barrier properties. Nevertheless, the substrate and cover may be provided for the purpose of continuing to limit the situation in which the transmissive material is transmitted towards the electronic structure 3.

In particular in connection with FIGS. 2 and 3, the fact is that in the present case the figures are schematic. It is not known from the figures that in particular the sheet-like structure 5 is in this case and preferably each has a uniform layer thickness. Therefore, the sharp edges as shown in the drawing are not formed at the place to be converted into the electronic structure, but rather, the place to be converted is not defined at the boundary, and small areas which are not filled with gas or filled with gas are kept intact. Can be. In some cases, however, adaptation to the ground can also be made, in particular when the application is carried out in a vacuum. In addition, the sheet-shaped structures are compressed to locally different strengths, and as a result, the flow process can compensate for some of the height differences in the edge structures. The dimensions shown in the figures do not fit the scale, but rather are used only for the purpose of clarifying an overview of the figures. In particular, the electronic structure itself is generally formed relatively flat (often with a thickness of less than 1 μm).

Application of the sheet-like structure 5 takes place in the form of an adhesive band in all the embodiments shown in the figures. In this case, in principle, a double-sided adhesive band with a support, a thin film that can be activated by heat, or a transfer adhesive band can be used. One shape in this case was chosen as a thin film that can be activated by heat.

The thickness of the sheet-like structure, which is present as a thermally-activated thin film or coated on a flat structure, as a transfer adhesive band, is preferably from about 1 μm to about 150 μm, more preferably from about 5 μm to About 75 μm and particularly preferably about 12 μm to 50 μm. High layer thicknesses of 50 μm to 150 μm are used when the improved adhesion state must be reached on the substrate and / or the damping effect must be reached inside the (photo-) electronic structure. However, a disadvantage of this case is the increased transmission cross section. Low layer thicknesses of 1 μm to 12 μm reduce the transverse cross section, as well as the overall thickness of the transverse transmissive and (opto-) electronic structures. However, the adhesive state is released from the substrate. Within a particularly preferred thickness range there is a good compromise between low adhesive thickness and low permeation cross section which reduces the resulting permeation, and an adhesive thin film of sufficient thickness is provided to make a sufficient adhesive bond. The optimum thickness depends on the implementation of the (opto-) electronic structure, the end application, the sheet-like structure, and in some cases on a flat substrate.

Test Methods

Life test:

As the property value for the adhesion quality to be obtained, encapsulation sealing and different method parameters for different sheet-like structures that can be bonded in a thermally activated manner are determined. The encapsulation seal directly affects the lifetime of the (opto-) electronic structure.

The calcium test is used as a measure for determining the lifetime of a (photo-) electronic structure. For this purpose a thin layer of calcium of size 10 x 10 mm ² is deposited on a glass plate (substrate) under a nitrogen atmosphere. The thickness of the calcium layer is about 100 nm. To encapsulate the calcium layer as well, under a nitrogen atmosphere, a frame-shaped sheet structure having a 30 mm x 30 mm edge length of the adhesive which can be activated by heat and a web width of 2 mm is placed around the calcium mirror. And a thin glass plate (200 μm, Schott) is provided as a cover. The adhesive is then activated by heat, in which case the surface of the capsule is compressed by a pressure which varies with the chosen adhesive. After the activation time is over, the combination is further compressed for 30 seconds, after which the compression device is pulled out. Only transmission through the adhesive surface is detected because of the opaque glass substrate and the glass cover of the adhesive band.

The test is for example A.G. Erlat et al. "47th Annual Technical Conference Proceedings-Society of Vacuum Coaters", 2004, pages 654-659, and M.E. It is based on the reaction of water vapor with oxygen and calcium as described by Gross et al., "46th Annual Technical Conference Proceedings-Society of Vacuum Coaters", 2003, pages 89-92. In this case, increasing light transmission of the calcium layer is observed by conversion to calcium hydroxide and calcium oxide. The time until reaching half the transmission of the corresponding test structure without the calcium mirror is indicated as the lifetime. As measurement conditions, a temperature of 60 ° C. and a relative humidity of 90% are selected.

Visual and passive judgment

Particularly flexible (opto-) electronic structures are encapsulated between modified polyester thin films, so for further testing a 100 μm thick polyester thin film, for example, the Melinex 506 thin film from Teijin-DuPont-Films This was used. Since the thin film itself does not have a transmission barrier layer, a life test cannot be performed by the thin film. As such, adhesion is judged only visually and the state of the binder is only tested manually.

Activatable Adhesives Used

Glue 1 (Pressure Glue):

50 parts Kraton FG 1924 Kraton maleic anhydride modified SEBS with 13 weight-% block polystyrol content, 36 weight-% 2 blocks and 1 weight-% maleic acid

Kraton maleic anhydride modified SEBS with 50 parts Kraton FG 1901 30 weight-% block polystyrol content, 2-block free and 1.7 weight-% maleic acid

70 Partial Escorez 5615 Hydrogenated KW-resin from Exxon with softening point of 115 ° C

25 part White oil from Shell, consisting of Ondina 917 paraffin and naphthene

1 part aluminum-acetylacetonate

The adhesive was prepared from solution. For this purpose, the individual components are dissolved in toluol (40% solids), coated on a separation paper siliconized to 1.5 g / m ² and dried at 120 ° C. for 15 minutes, resulting in 25 g / An adhesive layer was produced with a weight per unit area of m ² . The transfer adhesive was covered with additional separator paper during storage. Activation is achieved by dissolution of the coordinating bond of the aluminum chelate complex, whereby the viscosity drops severely and the activation temperature reaches about 120 ° C.

Glue 2 (High Temperature Melt Glue):

Triblock-SiBS from Kaneka with a block polystyrol content of 100 parts SiBStar 103 T 30 weight-%

20 parts SiBStar 042 D Diblock-SiB from Kaneka with a block polystyrol content of 15% by weight

The hot melt adhesive was prepared from solution. For this purpose, the individual components are dissolved in toluol (40% solids), coated on a separation paper siliconized to 1.5 g / m ² and dried at 120 ° C. for 15 minutes, resulting in 25 g / An adhesive layer was produced having a weight per unit area of m ² or 13 g / m ² . Thus, after removing the separation paper, one film could be obtained from the pure hot melt adhesive. The activation temperature reaches about 95 ° C.

Adhesive 3 to 7:

As additional adhesives that can be activated by heat, thin films of adhesive that can be activated by heat with different chemical bases were used (see table). For this purpose, commercially available and thermally activated thin films (tesa SE, Hamburg oder Peccell Technoligies Inc., Japan) could be used in part.

Table 1 below shows the additional adhesives used:

Abbreviation:

N / P: Nitrile Rubber / Phenolic Resin

PA: copolyamide

PET: Copolyester

SR / EP: synthetic rubber / epoxy resin

MI: Modified Ionomer

tesa 8471 is a high temperature crosslinking system based on nitrile rubber / phenolic resins (“thermosetting”).

tesa 8440 is a pure hot melt adhesive (ie thermoplastic) based on copolyamides.

tesa 8464 is a pure hot melt adhesive (ie thermoplastic) based on copolyester.

tesa 8865 is a high temperature crosslinking system based on nitrile rubber / epoxy resins (“thermosetting”).

Glue 8 (pressure sensitive adhesive)

25 part Oppanol B15 Polyisobutylene from BASF, M _w = 75,000 g / mol

5-part Oppanol B100 Polyisobutylene from BASF,

M _w = 1,100,000 g / mol

50-part Escorez 5615 Hydrogenated KW-resin from Exxon with softening point of 115 ° C

20 parts DCP Sigma-Aldrich's dicyclodecane-dimethanol dimethacrylate,

Dimethacrylate Monomer

1-part DLP dilauuroyl-peroxide

The adhesive was prepared from solution. For this purpose, the individual components are dissolved in heptane (45% solids), coated on a separation paper siliconized to 1.5 g / m ² and dried at 100 ° C. for 15 minutes, resulting in 25 g / m ^An adhesive layer was produced with a weight per unit area of ^two . The transfer adhesive was covered with additional separator paper during storage. The activation temperature reaches about 120 ° C.

Manufacture of sheet-like structures

In order to reach a thickness thinner than the commercially available adhesive thin film thickness, thicker products were optionally dissolved in 2-butanone or toluol and the adhesive layer of the required thickness from the solution by coating out and drying. Were prepared. The thicknesses selected for the manufacture of the sheet like structure are listed in the table above.

For induction heating, one thin film each having a thickness of 13 μm was laminated on each side of the conductive sheet-like structure. As the conductive sheet-like structure for induction heating, an aluminum thin film having a thickness of 36 μm was used. The metal thin film was laminated with adhesive layers at a temperature of about 90 ° C to 110 ° C. The thermoplastic thin films did not yet have sufficient adhesion, did not initiate chemical crosslinking reactions, but rather caused only sticking states.

Used substrates and covers

For the life test, float glass was used as the substrate and cover as 3 mm thick and 50 × 50 mm ² dimensions.

In addition, a Melinex 506 polyester thin film manufactured by Teijin-DuPont-Films was used at a thickness of 100 μm.

Implementation and results of the method according to the invention:

Ultrasound Activation:

This bonding was performed using the ultrasonic device PS MPC (+) digital control from Hermann Ultraschalltechnik. The device operates at 35 kHz and with a welding power of up to 1,000 W. A special titanium carbide-sonot rod was used in the form of an adhesive surface for the calcium test. The sonotrode was used to provide the indicated pressure (relative to the adhesion surface) and ultrasound. The sample body was mechanically fixed on the anvil before ultrasonic activation. After blocking the ultrasonic waves, the compressive force was further maintained for 30 seconds to enable curing of the adhesive.

Table 2 gives an overview of the test and its results:

The test shows that capsules whose sealing force is determined only by the permeation properties (particularly against water vapor) of the activatable adhesive system used can be produced by the method according to the invention. In contrast, test bodies that were not completely sealed macroscopically by the encapsulation method generally exhibited less than one hour of life.

Induction heating

This bonding method was carried out using a modified induction device of type EW5F from IFF GmbH of Ismaning. In this case, a coil provided with a ferrite core is used as a derivative for locally providing a magnetic alternating magnetic field. 4 shows a schematic side view (not to scale) of the device.

In FIG. 4, reference numeral 11 shows the layer structure for the calcium test, and 12 shows the ferrite core wound by the coil 13. The ferrite core 12 has been adapted to the dimensions of the adhesive band element in its dimensions.

The derivative was embedded in a matrix of polyetheretherketone (PEEK), and the device thus obtained is used as the lower pressing stamp element of the pressing apparatus, which also includes the upper pressing stamp element. Due to the power F, the compressive forces provided on the layered structure between the lower compacted stamp element and the upper compacted stamp element perpendicular to the side of the sheet-like structure that can be bonded in a thermally activated manner are described in Table 3, respectively. have. The spacing of the adhesive seams to the derivatives amounted to about 3 mm each. In the case of polyester thin films a corresponding PTFE-plate was provided at the bottom.

Using this modified induction device, a self- alternating magnetic field of 10 kHz frequency was generated for the tests when the pulse width was 10%. The pulse width is a percentage of the percentage of the pulse period (pulse length) of the magnetic- alternating magnetic field in the total period of the magnetic alternating magnetic field (total of the pause period and the pulse period between two consecutive pulses). Instruct.

The time that the sheet-like structure, which can be bonded in a thermally activated manner, to the pulsed magnetic- alternating magnetic field (ie the period of induction heating) was in the range of 0.5 to 2 seconds. After blocking the magnetic field, the compressive force was further maintained for 30 seconds to enable curing of the adhesive.

Table 3 gives an overview of the test and its results:

The test shows that capsules whose sealing force is determined only by the permeation properties (particularly against water vapor) of the activatable adhesive system used can be produced by the method according to the invention. In contrast, test bodies that were not completely sealed macroscopically by the encapsulation method generally exhibited less than one hour of life.

Temperatures corresponding to Test 6 in the sheet-like structure were detected using an infrared camera of type Ti20 from Fluke. By omitting the cover in the layer combination described above for this purpose and not closing the compression device during the induction time, one side of the sheet-like structure which is subsequently bonded in the heat activated manner is visible to the camera. The induction time was changed. The results are shown in Table 4:

The detected temperatures also indicate other adhesion embodiments, since the susceptors for the magnetic field are the same in material and dimensions, respectively.

Implementation and results of the comparison method:

For comparison, heating was performed using a conventional heat press of Muehlbauer. An upper hot press tool (facing the cover side) made of aluminum and in the form of an adhesive surface for the calcium test was used. As the lower tool, an aluminum plate having room temperature was used. The upper press tool was used to provide the indicated pressure (relative to the adhesive surface) and provide heat by thermal conduction. The sample body was mechanically fixed on the lower tool prior to heat compression. After the heat compression time had ended the heated upper tool was opened for a short time and the aluminum plate at room temperature was placed in the middle, and then the compressive force was restored for an additional 30 seconds to enable curing of the adhesive.

Sheet-like structures were used that corresponded to the thickness (25 μm) for ultrasonic bonding and were bonded in a thermally activated manner.

Table 4 gives an overview of the test and its results:

The comparative tests show that capsules are produced on a polymer substrate by the method according to the prior art only when the activation temperature lies below a temperature of about 170 ° C., ie when the polymer thin film is clearly damaged by the heat stamp. It can be shown or capsules with a polymer cover can be made. In this case too much time is required to make the bond than is necessary in the process according to the invention. In addition, the method according to the invention permits overheating for a short time which is limited only to the adhesive which is actually active due to the short process time and does not damage the PET-thin film inside the adhesive seam to the extent that it is mentioned (Example 26).

Claims (15)

A method for encapsulating an electronic device with respect to a transmissive material, the method comprising
Providing a sheet-like structure comprising at least one pressure-sensitive or hot melt adhesive that can be activated by heat;
Applying the sheet-like structure at least around the areas to be encapsulated of the electronic device on a substrate supporting / comprising the electronic device;
Providing a cover to the electronic device and to an adhesive at least surrounding the electronic device, wherein the adhesive is in contact with the cover; And
Then thermally activating the adhesive in at least a partial region of the cover surface, thereby forming at least a bond of the substrate and the cover, wherein the heat necessary for activation is actually the sheet which at least surrounds the adhesive. A method for encapsulating an electronic device with respect to a transmissive material, occurring within the shape structure itself. A method for encapsulating an electronic device with respect to a transmissive material, the method comprising
Providing a sheet-like structure comprising at least one pressure-sensitive or hot melt adhesive that can be activated by heat;
Applying the sheet-like structure around at least the areas to be encapsulated of the electronic device on a substrate supporting / comprising the electronic device or on a cover provided for encapsulating the electronic device;
Providing the electronic device with a cover for supporting an adhesive at least surrounding the electronic device, wherein the adhesive is in contact with at least the substrate; And
Then thermally activating the adhesive in at least a partial region of the cover surface, thereby forming at least a bond of the substrate and the cover, wherein the heat necessary for activation is actually the sheet which at least surrounds the adhesive. A method for encapsulating an electronic device with respect to a transmissive material, which occurs within the shape structure itself. 3. The method of claim 1, wherein the heat is generated by ultrasound in a sheet-like structure comprising at least the adhesive. 4. 4. The method of any one of the preceding claims, wherein the heat is generated by magnetic induction in a sheet-like structure comprising at least the adhesive. The method of claim 4, wherein the derivative is integrated within the at least one crimping tool. The method of claim 1, wherein the induction heating is made using a magnetic field, the frequency of the magnetic field lies in the intermediate frequency range of 100 Hz to 200 kHz, and / or the induction heating. Using a heating time of 0.1 to 10 seconds to encapsulate the electronic device against the permeable material. 7. The method of any of claims 1-6, wherein the activatable adhesive is an activatable pressure sensitive adhesive. 8. Encapsulating an electronic device with respect to a permeable material according to any one of claims 1 to 7, wherein iron oxide-particles surrounded by silicon dioxide are present inside the sheet-like structure, in particular within the adhesive of the sheet-like structure. How to. 9. A permeation barrier according to any one of the preceding claims, wherein the substrate material and / or the cover is provided with a permeation barrier for oxygen and water vapor, wherein the permeation barrier is 10 ^-1 g / (m ² for WVTR). d) and / or less than 10 ⁻¹ cm ³ / (m ² d bar) for OTR and in particular less than 10 ⁻² g / (m ² d) for WVTR A method for encapsulating an electronic device with respect to a transmissive material having a value of less than 10 ⁻² cm ³ / (m ² d bar) for OTR. 10. An electronic device as claimed in claim 1, wherein the substrate material and / or the cover has an average transmission of at least 75%, preferably higher than 85%, in the visible light range. Method for encapsulation for permeable material. The method according to any one of the preceding claims, wherein the activatable adhesive has a mechanical loss factor (tan δ) of at least 0.1, preferably at least one and / or the difference tan δ _adhesive —tan δ _{substrate or The cover} is preferably at least one, the method for encapsulating the electronic device with respect to the transmissive material. The method of claim 1, wherein the activatable adhesive has an electrical conductivity of at least 20 MS / m at a temperature of 23 ° C. 13. 13. The activatable adhesive according to claim 1, wherein the activatable adhesive has a WVTR of less than 100 g / m ² d, in particular less than 10 g / m ² d, and / or 8,000 cm ³ / m ^2. A method for encapsulating an electronic device with respect to a transmissive material, having an OTR of less than d bar, in particular less than 3,000 cm ³ / m ² d bar and very particularly less than 100 cm ³ / m ² d bar. The method of any of claims 1 to 13, wherein the activatable adhesive is provided with a collecting material for the transmissive material. The adhesive layer according to claim 1, wherein the sheet-like structure for induction heating is bonded to at least three different layers, ie at least one electrically conductive layer and at least one thermally activated manner. A method for encapsulating an electronic device with respect to a transmissive material comprising one additional adhesive layer.

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