Method for encapsulating an electronic arrangement

Abstract

The present invention relates to a method for encapsulating an electronic arrangement against permeants, in which a pressure-sensitive adhesive composition based on vinylaromatic block copolymers is provided, and in which the pressure-sensitive adhesive composition is applied onto and/or around the regions of the electronic arrangement which are to be encapsulated.

Claims

1. Method for encapsulating an electronic arrangement against permeants, the method comprising: providing a pressure-sensitive adhesive composition comprised of vinylaromatic block copolymers and at least one resin having a softening point of 100 C. or more, wherein the pressure-sensitive adhesive composition exhibits a combination of adhesive and cohesive properties such that the pressure-sensitive adhesive composition constantly exhibits permanent tack and flexibility, wherein the block copolymers contain polymer blocks formed by vinylaromatics, wherein the block copolymers contain polymer blocks formed by polymerization of 1,3-dienes that are partially, selectively or fully hydrogenated polymer blocks, wherein the at least one resin is a hydrogenated hydrocarbon resin having a degree of hydrogenation of at least 90%, a DACP value of more than 30 C. and a MMAP value of more than 50 C., and further wherein the pressure-sensitive adhesive composition has a WVTR of less than 100 g/m.sup.2.Math.d; and applying the pressure-sensitive adhesive composition onto and/or around regions of the electronic arrangement that are to be encapsulated.

2. Method according to claim 1, wherein the pressure-sensitive adhesive composition is provided in the form of an adhesive tape.

3. Method according to claim 1 wherein the pressure-sensitive adhesive composition is crosslinked after application on the electronic arrangement.

4. Method according to claim 1, wherein the application of the pressure-sensitive adhesive composition is effected without a subsequent thermal process step or irradiation.

5. Method of claim 1, wherein the pressure-sensitive adhesive composition contains polymer blocks formed by polymerization of butadiene and/or isoprene.

6. Method according to claim 5, wherein the block copolymers have a polyvinylaromatic fraction of 10% by weight to 35% by weight.

7. Method according to claim 5, wherein the pressure-sensitive adhesive composition has a fraction of the vinylaromatic block copolymers of at least 35% by weight, and the pressure-sensitive adhesive composition has a fraction of the vinylaromatic block copolymers of at most 80% by weight.

8. Method according to claim 1, wherein the hydrogenated hydrocarbon resin is based on hydrogenated polymers of dicyclopentadiene and has a degree of hydrogenation of at least 95%, a DACP value of more than 37 C. and a MMAP value of more than 60 C.

9. Method according to claim 1, wherein the at least one resin is selected from the group consisting of non-hydrogenated, partially hydrogenated or fully hydrogenated resins based on rosin and rosin derivatives, hydrogenated polymers of dicyclopentadiene, non-hydrogenated or partially, selectively or fully hydrogenated hydrocarbon resins based on C5, C5-C9 or C9 monomer streams, polyterpene resins based on -pinene and/or -pinene and/or -limonene, and hydrogenated polymers of pure C8 and C9 aromatics.

10. Method according to claim 5, wherein the pressure-sensitive adhesive composition contains one or more additives selected from the group consisting of plasticizers, primary antioxidants, secondary antioxidants, process stabilizers, light stabilizers, processing assistants, end block reinforcer resins and polymers.

11. Method according to claim 5, wherein the pressure-sensitive adhesive composition contains one or more nanoscale fillers, transparent fillers and/or getter and/or scavenger fillers.

12. Method according to claim 11, wherein the fillers are embodied in nanoscale fashion in at least one dimension.

13. Method according to claim 11 the pressure-sensitive adhesive composition has a fraction of the fillers of at least 5% by weight and/or has a fraction of the fillers of at most 95% by weight.

14. Method according to claim 5, wherein the pressure-sensitive adhesive composition has an average transmittance of at least 75% in the wavelength range of 400 nm to 800 nm.

15. Method according to claim 5, wherein the pressure-sensitive adhesive composition is embodied in UV-blocking fashion in the wavelength range of 190 nm to 400 nm, where an average transmittance of at most 20% is designated as UV-blocking.

16. Method according to claim 5, wherein the pressure-sensitive adhesive composition, after crosslinking, has an elongation at break of at least 20%.

17. Method according to claim 5, wherein the pressure-sensitive adhesive composition has an OTR of less than 10 000 g/m.sup.2.Math.d.Math.bar.

18. Method according to claim 5, wherein the pressure-sensitive adhesive composition is embodied as a carrier-free adhesive tape.

19. Method according to claim 2, wherein the layer thickness of the pressure-sensitive adhesive composition in the adhesive tape is at least 1 mand/or the layer thickness of the pressure-sensitive adhesive composition in the adhesive tape is at most 150 m.

20. Method according to claim 1, wherein epoxidized vinylaromatic block copolymers are excluded from the vinylaromatic block copolymers of the pressure-sensitive adhesive composition.

21. Method for encapsulating an electronic arrangement against permeants, the method comprising: providing a pressure-sensitive adhesive composition comprised of vinylaromatic block copolymers, wherein the pressure-sensitive adhesive composition contains a resin or a resin mixture, wherein the pressure-sensitive adhesive composition contains at least one resin, having a softening point of 100 C. or more, that provides a permeation barrier against oxygen, wherein the block copolymers contain polymer blocks formed by vinylaromatics, wherein the block copolymers contain polymer blocks formed by polymerization of 1,3-dienes that are partially, selectively or fully hydrogenated polymer blocks, wherein the at least one resin is a hydrogenated hydrocarbon resin having a degree of hydrogenation of at least 90%, a DACP value of more than 30 C. and a MMAP value of more than 50 C., and further wherein the pressure-sensitive adhesive composition has a WVTR of less than 100 g/m.sup.2.Math.d; and applying the pressure-sensitive adhesive composition onto and/or around regions of the electronic arrangement that are to be encapsulated.

22. Method for encapsulating an electronic arrangement against permeants, the method comprising: providing a pressure-sensitive adhesive composition comprised of vinylaromatic block copolymers and at least one resin having a DACP value of more than 30 C. and a MMAP value of more than 50 C., wherein the pressure-sensitive adhesive composition exhibits a combination of adhesive and cohesive properties such that the pressure-sensitive adhesive composition constantly exhibits permanent tack and flexibility, wherein the block copolymers contain polymer blocks formed by vinylaromatics, wherein the block copolymers contain polymer blocks formed by polymerization of 1,3-dienes that are partially, selectively or fully hydrogenated polymer blocks, wherein the at least one resin is a hydrogenated hydrocarbon resin having a degree of hydrogenation of at least 90%, and further wherein the pressure-sensitive adhesive composition has a WVTR of less than 100 g/m.sup.2.Math.d; and applying the pressure-sensitive adhesive composition onto and/or around regions of the electronic arrangement that are to be encapsulated.

Description

(1) Further details, aims, features and advantages of the present invention are explained more comprehensively below on the basis of preferred exemplary embodiments. In the drawing:

(2) FIG. 1 shows a first (opto)electronic arrangement in schematic illustration,

(3) FIG. 2 shows a second (opto)electronic arrangement in schematic illustration,

(4) FIG. 3 shows a third (opto)electronic arrangement in schematic illustration.

(5) FIG. 1 shows a first configuration of an (opto)electronic arrangement 1. This arrangement 1 has a substrate 2, on which an electronic structure 3 is arranged. The substrate 2 itself is embodied as a barrier to permeants and thus forms part of the encapsulation of the electronic structure 3. A further covering 4, embodied as a barrier, is arranged above the electronic structure 3, and in the present case also spatially at a distance therefrom.

(6) In order also to encapsulate the electronic structure 3 towards the side and moreover at the same time to connect a covering 4 to the electronic arrangement 1, a pressure-sensitive adhesive composition 5 is provided circumferentially alongside the electronic structure 3 on the substrate 2. The pressure-sensitive adhesive composition 5 connects the covering 4 to the substrate 2. By means of an appropriately thick configuration, the pressure-sensitive adhesive composition 5 additionally enables the covering 4 to be spaced apart from the electronic structure 3.

(7) The pressure-sensitive adhesive composition 5 is one based on vinylaromatic block copolymers such as was described in general form above and is set out in greater detail in exemplary embodiments below. In the present case, the pressure-sensitive adhesive composition 5 not only performs the function of connecting the substrate 2 to the covering 4 but also additionally forms a barrier layer for permeants, in order thus to encapsulate the electronic structure 2 against permeants such as water vapour and oxygen from the side as well.

(8) In the present case, the pressure-sensitive adhesive composition 5 is additionally provided in the form of a die cut from a double-sided adhesive tape. Such a die cut enables particularly simple application.

(9) FIG. 2 shows an alternative configuration of an (opto)electronic arrangement 1. Once again an electronic structure 3 is shown which is arranged on a substrate 2 and is encapsulated from below by the substrate 2. The pressure-sensitive adhesive composition 5 is now arranged over the whole area above and to the sides of the electronic structure. The electronic structure 3 is thus encapsulated by the pressure-sensitive adhesive composition 5 at these locations. A covering 4 is then applied to the pressure-sensitive adhesive composition 5. In contrast to the previous configuration, said covering 4 does not necessarily have to meet the stringent barrier requirements, since the barrier is already provided by the pressure-sensitive adhesive composition. The covering 4 can for example just perform a mechanical protective function; however, it can also additionally be provided as a permeation barrier.

(10) FIG. 3 shows a further alternative configuration of an (opto)electronic arrangement 1. In contrast to the previous configurations, two pressure-sensitive adhesive compositions 5a, b are now provided, which are embodied identically in the present case. The first pressure-sensitive adhesive composition 5a is arranged over the whole area on the substrate 2. The electronic structure 3 is then provided on the pressure-sensitive adhesive composition 5a, said electronic structure being fixed by the pressure-sensitive adhesive composition 5a. The composite comprising pressure-sensitive adhesive composition 5a and electronic structure 3 is then covered over the whole area by the further pressure-sensitive adhesive composition 5b, with the result that the electronic structure 3 is encapsulated from all sides by the pressure-sensitive adhesive compositions 5a, b. The covering 4 is then once again provided above the pressure-sensitive adhesive composition 5b.

(11) In this configuration, therefore, neither the substrate 2 nor the covering 4 necessarily has to have barrier properties. However, they can nevertheless be provided, in order to further restrict the permeation of permeants to the electronic structure 3.

(12) With regard to FIGS. 2, 3, in particular, it is pointed out that the illustrations are schematic illustrations in the present case. It is not evident from the illustrations that the pressure-sensitive adhesive composition 5 is in each case applied with a homogenous layer thickness. At the transition to the electronic structure, therefore, a sharp edge such as there appears to be in the illustration is not formed, rather the transition is fluid and it is possible, rather, for small unfilled or gas-filled regions to remain. If appropriate, however, adaptation to the substrate can also be effected, particularly when the application is carried out under vacuum. Moreover, the pressure-sensitive adhesive composition is compressed to different extents locally, with the result that a certain compensation of the height difference at the edge structures can be effected as a result of flow processes. Moreover, the dimensions shown are not to scale, but rather serve only for better illustration. In particular the electronic structure itself is generally embodied in relatively flat fashion (often less than 1 m thick).

(13) In all the exemplary embodiments shown, the pressure-sensitive adhesive composition 5 is applied in the form of a pressure-sensitive adhesive tape. This can be, in principle, a double-sided pressure-sensitive adhesive tape with a carrier, or a transfer adhesive tape. A configuration of a transfer adhesive tape is chosen in the present case.

(14) The thickness of the pressure-sensitive adhesive composition, which is present either as a transfer adhesive tape or in a manner coated on a planar structure, is preferably between approximately 1 m and approximately 150 m, more preferably between approximately 5 m and approximately 75 m, and particularly preferably between approximately 12 m and 50 m. In the preferred thickness ranges there is a good compromise between a small composition thickness and the resultant small permeation cross section, which reduces the permeation, and a sufficiently thick composition film for producing a sufficiently adhesive connection. The optimum thickness depends on the (opto)electronic construction, the final application, the type of embodiment of the pressure-sensitive adhesive composition and, if appropriate, the planar substrate.

EXAMPLES

(15) Unless indicated otherwise, all quantitative indications in the examples below are percentages by weight or parts by weight relative to the overall formulation.

(16) Test Methods

(17) Bond Strength

(18) The determination of the bond strength was carried out as follows: a steel surface, a polyethylene terephthalate (PET) plate and a polyethylene (PE) plate were used as the defined substrate. The bondable planar element under investigation was cut to a width of 20 mm and a length of approximately 25 cm, provided with a handling section, and immediately thereafter pressed onto the respectively selected substrate five times by means of a 4 kg steel roller at a speed of 10 m/min. Immediately after that, the previously bonded planar element was stripped from the substrate by means of a tensile testing instrument (Zwick) at an angle of 180 at room temperature and 300 mm/min, and the force required to achieve this was measured. The measurement value (in N/cm) resulted as the average value from three individual measurements.

(19) Shear Adhesion Failure Temperature (SAFT)

(20) The determination of the SAFT was carried out as follows: a polished steel surface was used as the defined substrate. The bondable planar element under investigation was cut to a width of 10 mm and a length of approximately 5 cm, and immediately thereafter pressed onto the respectively selected substrate having an area of 1013 mm three times by means of 2 kg steel roller at a speed of 10 m/min. Immediately after that, the previously bonded planar element was loaded with 0.5 N at an angle of 180 and a temperature ramp of 9 C./min was implemented. The temperature at which the sample covered a slip distance of 1 mm was measured in this case. The measurement value (in C.) results as the average value from two individual measurements.

(21) Transmission

(22) The transmission of the adhesive composition was determined over the VIS spectrum. The recordings of the VIS spectrum were carried on a UVIKON 923 from Kontron. The wavelength range of the measured spectrum encompasses all frequencies between 800 nm and 400 nm at a resolution of 1 nm. For this purpose, the adhesive composition was applied to a PET carrier and the measurement was preceded by an idle channel measurement of the carrier as a reference over the entire wavelength range. The result was specified by averaging the transmission measurements in the specified range.

(23) Permeation

(24) The permeability for oxygen (OTR) and water vapour (WVTR) was determined according to DIN 53380 part 3 and ASTM F-1249, respectively. For this purpose, the pressure-sensitive adhesive composition was applied with a layer thickness of 50 m to a permeable membrane. For the oxygen permeability, measurement was effected at 23 C. and a relative humidity of 50%. The water vapour permeability was determined at 37.5 C. and a relative humidity of 90%.

(25) Bending Test

(26) For determining the flexibility, the adhesive composition was coated in a layer thickness of 50 m between two 23 m PET carriers and tested to a bending radius of 1 mm during bending of 180. The test is passed if the layer does not break or become detached.

(27) Lifetime Test

(28) A calcium test was used as a measure of the determination of the lifetime of an (opto)electronic construction. For this purpose, under a nitrogen atmosphere a thin calcium layer with a size of 2020 mm.sup.2 is deposited onto a glass plate. The thickness of the calcium layer is approximately 100 nm. The calcium layer is encapsulated using an adhesive tape with a PET barrier film as carrier material (WVTR=810.sup.2 g/m.sup.2*d and OTR=610.sup.2 cm.sup.3/m.sup.2.Math.d.Math.bar, in accordance with conditions mentioned according to ASTM F-1249 and DIN 53380 part 3 and above). The adhesive tape is applied with an all-round edge of 5 mm above the calcium level at which it adheres directly on the glass plate.

(29) The test is based on the reaction of calcium with water vapour and oxygen as described for example by A. G. Erlat et. al. in 47th Annual Technical Conference ProceedingsSociety of Vacuum Coaters, 2004, pages 654-659, and by M. E. Gross et al. in 46th Annual Technical Conference ProceedingsSociety of Vacuum Coaters, 2003, pages 89-92. In this case, the light transmission of the calcium layer is monitored, which increases as a result of the conversion into calcium hydroxide and calcium oxide. The attainment of 90% of the transmission of the construction without a calcium layer is designated as the end of the lifetime. 23 C. and 50% relative air humidity are chosen as measurement conditions. The specimens were adhesively bonded over the whole area and without any bubbles with a layer thickness of the pressure-sensitive adhesive composition of 25 m.

(30) Production of the Specimens

(31) The pressure-sensitive adhesive compositions in examples 1 to 4 were prepared from solution. This was done by dissolving the individual constituents in toluene (solids fraction 40%) and coating out the solution onto an untreated PET film, with drying at 120 C. for 15 minutes, in such a way as to produce a layer of adhesive composition having a weight per unit area of 50 g/m.sup.2. For the permeation test, specimens were produced in the same way, but the solution was coated out not onto a PET film but rather onto a release paper siliconized with 1.5 g/m.sup.2, with the result that after transfer to the permeable membrane, it was possible to perform a measurement on the pure pressure-sensitive adhesive composition.

Example 1

(32) TABLE-US-00001 100 parts Vector 4113 SIS with 15% block polystyrene content from Dexco. The SIS contained approximately 20% diblock content. 100 parts Escorez 5600 Hydrogenated HC resin (hydrocarbon resin) with a softening point of 100 C., from Exxon 25 parts Ondina G 17 White oil comprising 66% paraffinic and 34% naphthenic fractions, from Shell

Example 2

(33) TABLE-US-00002 100 parts Kraton G 1657 SEBS with 13% block polystyrene content from Kraton. The SEBS contained approximately 36% diblock content. 100 parts Escorez 5600 Hydrogenated HC resin with a softening point of 100 C., from Exxon. 25 parts Ondina G 17 White oil comprising paraffinic and naphthenic fractions, from Shell

Example 3

(34) TABLE-US-00003 100 parts Tuftec P 1500 SEBS with 30% block polystyrene content from Asahi. The SEBS contained approximately 68% diblock content. 100 parts Escorez 5600 Hydrogenated HC resin with a softening point of 100 C., from Exxon. 25 parts Ondina G 17 White oil comprising paraffinic and naphthenic fractions, from Shell

Example 4

(35) TABLE-US-00004 70 parts Tuftec P 1500 SBBS with 30% block polystyrene content from Asahi. The SBBS contained approximately 68% diblock content. 30 parts Kraton G 1657 SEBS with 13% block polystyrene content from Kraton. The SEBS contained approximately 36% diblock content. 100 parts Escorez 5600 Hydrogenated HC resin with a softening point of 100 C., from Exxon 25 parts Ondina G 17 White oil comprising paraffinic and naphthenic fractions, from Shell

Comparative Example C1

(36) An acrylate having the formulation 78% EHA, 19% stearyl acrylate and 3% acrylic acid was polymerized in acetone and petroleum spirit and coated from the solution onto an untreated PET carrier (or onto a release paper siliconized with 1.5 g/m.sup.2 for the permeation measurements), dried at 120 C. for 15 min and crosslinked with 0.2% aluminium chelate relative to the acrylate fraction. The thickness of the adhesive layer is 50 m.

Comparative Example C2

(37) A mixture of 60% levamelt 456 (ethylene vinylacetate) and 40% foral 85 are dissolved in acetone and coated from the solution onto an untreated PET carrier (or onto a release paper siliconized with 1.5 g/m.sup.2 for the permeation measurements) and dried at 120 C. for 15 min. The thickness of the adhesive layer is 50 m.

Comparative Example C3

(38) The commercially available silicone pressure-sensitive adhesive composition Silgrip PSA 529 from GE Bayer Silikons is mixed with benzoyl peroxide and coated from the solution onto an untreated PET carrier (or onto a release paper siliconized with 1.5 g/m.sup.2 for the permeation measurements) and dried at 120 C. for 15 min and crosslinked. The thickness of the adhesive layer is 50 m.

Comparative Example C4

(39) A commercially available UV-curing epoxide from Epo-Tek OG142 was spread onto a PET film in a thickness of 50 m and cured at 160 W/cm by means of a medium-pressure mercury vapour lamp at a path speed of 10 m/min. For the determination of permeation, the specimen was coated onto siliconized release paper and detached.

(40) Results:

(41) For the bonding-technological assessment of the examples mentioned above, firstly the bond strength, the SAFT test, tack and the test for flexibility were carried out.

(42) TABLE-US-00005 TABLE 1 Bond strength [N/cm] Steel/PET/PE SAFT [ C.] Bending test Example 1 10.7/9.5/7.4 120 passed Example 2 4.2/3.9/3.6 110 passed Example 3 7.3/6.2/5.7 98 passed Example 4 6.5/6.3/5.7 105 passed C1 9.5/5.5/4.2 145 passed C2 5.5/3.5/0.9 75 passed C3 5.5/5.7/3.9 87 passed C4 failed

(43) As can be discerned, in examples 1 to 4 it was possible to achieve high bond strengths similar on all substrates and good resistances at elevated temperatures which are at least comparable with or better than pressure-sensitive adhesive compositions based on a different chemical structure (C1 to C3). The comparison with C4 reveals the high flexibility of the pressure-sensitive adhesive compositions with respect to highly crosslinking epoxides.

(44) The results of the permeation and transmission measurements can be found in table 2.

(45) TABLE-US-00006 TABLE 2 WVTR OTR Transmission g/(m.sup.2*day) g/(m.sup.2*day*bar) [%] Example 1 42 4230 89 Example 2 89 7280 88 Example 3 33 8500 91 Example 4 53 6900 87 C1 320 40250 90 C2 >1000 62000 92 C3 >1000 75000 93 C4 27 35 93

(46) As can be discerned, the permeability of the pressure-sensitive adhesive compositions from example 1 to example 4 in comparison with C1 to C3 is very much lower and the transmission in the visible light range is similar. The water vapour permeability of the crosslinked epoxide and of the block copolymers is similar, and the oxygen permeability is higher in the case of the block copolymers. The transmission lies in a similar range for all the examples.

(47) Results of the Lifetime Test:

(48) TABLE-US-00007 TABLE 3 Lifetime [h] Example 3 320 C2 22 C3 12

(49) The lifetime tests clearly show, in comparison with other pressure-sensitive adhesive compositions, the very much better barrier effect and the resultant lengthening of the lifetime of the measurement construction.