Getter composition and dispensable paste comprising the getter composition

Abstract

An getter composition for controlling the amount of moisture and organic gases in a hermetically sealed electronic or optoelectronic device, the composition comprising a blend of a first getter powder and a second getter powder in a weight ratio of 0.1 to 5.0, wherein the first getter is polyphenylene oxide (PPO) or poly(2,6-diphenyl-p-phenylene oxide) (PPPO), and the second getter is faujasite (FAU) zeolite or a mixture of faujasite (FAU) zeolite and Linde type A (LTA) zeolite in a ratio of 0.1 to 5.0. The present invention also relates to a dispensable paste comprising a resin and the getter composition.

Description

[0001] The present invention relates to a dispersible getter composition for controlling the amount of moisture and organic gases in a sealed electronic or optoelectronic device, and to a dispensable paste comprising said getter composition.

[0002] It is generally known that electronic devices (especially some of their components) are sensitive to undesired contaminants and exhibit degraded performance when exposed to undesired contaminants, which include moisture and other contaminating gases such as oxygen, hydrogen, and volatile organic compounds (VOCs).

[0003] In the prior art, the main techniques for protecting organic electronic devices (i.e., electronic devices having organic components) from degradation include applying a barrier coating or sealant along the border of the organic electronic device to prevent contaminants from entering, in combination with placing an absorbent or absorptive getter material inside the sealed device to remove contaminants within its internal sealed volume.

[0004] The main desiccants for water removal generally include metal oxides (such as CaO, BaO, MgO); metal hydrides; metal salts; powdered zeolites (such as 4A molecular sieve and 3A molecular sieve); metal perchlorates; superabsorbent polymers; and metals that react with water such as calcium.

[0005] For example, EP1874885 discloses a radiation-curable desiccant-filled adhesive or sealant provided on the outer periphery of an electronic and optoelectronic device, where the desiccant filler serves as a moisture scavenging or barrier feature. In addition, WO2013165637 provides a radiation-curable or thermally curable encapsulant suitable for sealing and adhering a substrate and a cover of an organic electronic device to protect active organic components in the device from moisture and oxygen using one of the desiccant fillers reported above.

[0006] US20060283546 relates to a method for encapsulating an electronic device and thus sealing the electronic device, which includes a mixed getter material prepared using a zeolite getter powder combined with a polyimide resin.

[0007] In addition to the water barrier purpose, some applications have reported solutions aimed at ensuring the absorption of volatile organic compounds (VOCs), such as WO2008033647 and WO2010093237, which disclose optoelectronic devices having an electrically insulating material impermeable to VOCs, the VOCs being selected from substituted or unsubstituted carbon compounds, including alkanes, cycloalkanes, aromatic compounds, alcohols, ethers, esters, ketones, halogenated hydrocarbons, amines, organic acids, cyanates, nitrates and nitriles. In both cases, the desiccant effect is achieved by using various absorbent media, such as activated carbon, alumina and other metal oxides, zeolites, and organic absorbents containing hypercrosslinked systems.

[0008] One of the main goals in this field is to effectively reduce and at the same time control the amounts of water and organic gases, but as a drawback, for some substances competing with others, most of the typical getter materials and fillers used may reduce their effectiveness.

[0009] The inventors have unexpectedly found that when octahedral (FAU) zeolite or a mixture of FAU and Linde type A (LTA) zeolite is combined with a polyphenylene oxide (PPO) or poly(2,6-diphenyl-p-phenylene oxide) (PPPO) material in a specific ratio, the negative impact of VOCs on zeolite water absorption is significantly reduced, and the water absorption capacity remains substantially unchanged (i.e., within the measurement error range) despite the presence of VOC substances. In addition, at the same time, no negative impact of water on the VOC absorption capacity has been reported, and the compositions disclosed herein do not show a reduction in VOC absorption despite the presence of water.

[0010] Accordingly, an object of the present invention is a dispersible getter composition comprising a blend of a first getter and a second getter, wherein the first getter is PPO or PPPO, and the second getter is octahedral (FAU) zeolite or a mixture of FAU and Linde type A (LTA) zeolite. Specifically, the composition is characterized in that the ratio of the first getter to the second getter is from 0.1 to 5.0, preferably from 0.1 to 2.5. Compositions characterized by higher ratios do not provide significant water absorption, which results in undetectability by conventional measurement techniques.

[0011] In addition, the getter composition is in the form of a powder having a controlled particle size distribution, the particle size distribution being characterized by an 90 X value of from 1.0 μm to 50.0 μm (calculated according to volume distribution). In another preferred embodiment, the particle size distribution is characterized by an 90 X value of from 1.0 μm to 20.0 μm.

[0012] Another advantage associated with the present invention relates to the possibility of introducing the composition into a device and thereby removing both moisture and organic compounds that may be present as residues of the manufacturing process or generated during the operation of the device from inside the device. In this regard, to enhance the possibility of introducing the getter into the interior of the device, the composition should be dispersed in a matrix, i.e., it can be combined with a resin to prepare a dispensable paste.

[0013] Specifically, the getter blends disclosed herein can be dispersed in an epoxy resin or a phenolic resin or a mixture thereof, and are used in the dispensable paste in an amount of 10 wt% to 50 wt% relative to the total amount of the paste, including the resin curing agent. To obtain a dispensable paste, the composition is characterized in that the ratio of the first getter to the second getter is from 0.1 to 5.0, preferably from 0.1 to 2.5.

[0014] Since one of the goals of VOC absorption is to obtain a solvent-free formulation, the resin is substantially based on an epoxy resin selected from bisphenol F or bisphenol A, or a phenolic resin such as poly[(phenyl glycidyl ether)-co-formaldehyde], or a mixture thereof, in an amount of 50 wt% to 90 wt% of the total amount of the resin (including the curing agent).

[0015] To improve the viscosity of the paste and thus its dispensability, FAU zeolite can be mixed with Linde type A (LTA) zeolite, where the ratio of FAU zeolite to LTA zeolite is from 0.1 to 5.0.

[0016] In addition, to improve the visibility of the paste when applied to a surface, additional compounds can be added to the paste, such as colorant molecules selected from rare earth pigments and organic heterocyclic compounds, in an amount of 0.1 wt% to 10 wt% of the total amount of the paste.

[0017] The dispensable paste according to the present invention is suitable for being dispensed by methods commonly used in manufacturing and laboratory processes, such as a pneumatic syringe dispensing system.

[0018] In addition, another object of the present invention is a component for an electronic device, which includes at least one surface on which the paste has been dispensed.

[0019] In a preferred embodiment, the component of the electronic device having a surface at least partially covered with the paste according to the present invention is a cover for hermetically packaging the electronic device.

[0020] Hereinafter, the present invention will be described in more detail with reference to the following non-limiting examples. Modifications or variations that are obvious to those skilled in the art in the exemplified embodiments are covered by the appended claims. Examples

[0021] The getter powder blends of Samples S1 to S3 and Comparative Examples C1 to C4 reported in Table 1 were prepared by manually mixing neat getter powders. The absorption capacity (H2O and VOC loss) was measured using a state-of-the-art system - mass spectrometer.

[0022] To produce the dispensable pastes of Samples S4 to S10 and Comparative Examples C5 to C8 shown in Table 2, the resin plus curing agent (45 wt% to 65 wt%) and the getter powder blend (35 wt% to 55 wt%) were manually mixed in 10 g batches in the amounts listed in the table, and then refined using a suitable device such as a laboratory three-roll mill for 5 minutes.

[0023] Since the equivalent behavior of poly(2,6-diphenyl-p-phenylene oxide) (PPPO) is generally known (see, for example, “Monolithic Aerogels Based on Poly(2,6-diphenyl-1,4-phenylene oxide)andSyndiotactic Polystyrene”, ACS Appl. Mater. Interfaces 2013, 5, 12, 5493–5499), both the samples and the comparative examples were prepared using polyphenylene oxide (PPO) as the first getter.

[0024] The particle size distribution of the dry powder was measured using a laser diffraction instrument. The dispensability test was carried out using a pneumatic dispensing system connected to a standard pneumatic line with a cylindrical needle with a diameter of 300 μm to 800 μm.

[0025] The dispensability was visually determined and labeled / marked as:

[0026] “Optimal” if the flow from the syringe is continuous and the paste deposition is uniform.

[0027] “Good” if the maximum pressure (5 bar to 6 bar) from the standard pneumatic line is required.

[0028] “Poor” if the paste is too viscous and thus uneven after refinement: it cannot be dispensed.

[0029] Table 1.

[0030]

[0031] Table 2.

[0032]

[0033] The results reported clearly show the technical effects of the present invention; in fact, as reported in Comparative Example C3, it was possible to determine the negative impact of VOCs on the water absorption capacity of FAU zeolite, with a 10% decrease in the water absorption capacity of FAU zeolite when the getter composition was exposed to both toluene and water. In contrast, when testing Samples S1 to S3 prepared according to the present invention, although VOCs were present, there was no significant change in relative water absorption with respect to the expected capacity calculated based on the amounts of the different substances (PPO, FAU, and LTA) and their relative intrinsic capacities, with a maximum change of approximately 2.8% for S3.

[0034] As determined from the results reported in Table 1, it is known that when testing simple FAU zeolite as a getter, a good absorption capacity can be obtained; however, simple zeolites are not suitable for being dispersed in the target application in a sufficiently effective amount. As shown by Samples S2 and S3, a second zeolite (LTA) can be added while maintaining a positive effect on water absorption; in contrast, as reported in Comparative Example C4, when using only LTA zeolite in combination with PPO, the toluene absorption capacity decreased with respect to the value that could be obtained when using FAU zeolite as the second getter.

[0035] In Table 2, the quality evaluation of pastes S4 to S10 (in particular, S4 is the paste containing Composition S3) containing the getter composition prepared according to the present invention can be seen. The results reported also demonstrate the possibility of using different resins; in fact, both Samples S4 to S8 prepared using bisphenol F resin and S9 to S10 prepared using bisphenol A and poly[(phenyl glycidyl ether)-co-polyformaldehyde] resin, respectively, showed good dispensability. At the same time, considering the comparative examples, it is clear that it is not possible to obtain a dispensable paste when the amount of filler is higher than 50% (C5), or the ratio of FAU to LTA zeolite is too high (indicatively higher than 5.0 (C6)), or the second zeolite LTA is absent in the composition (C7), or the ratio of the first getter to the second getter is higher than 5.0 (C8).

Claims

1. A dispersible getter composition comprising a blend of a first getter powder and a second getter powder, wherein: - the first getter is polyphenylene oxide PPO or poly(2,6-diphenyl-p-phenylene oxide) PPPO, - the second getter is faujasite FAU or a mixture of faujasite FAU and Linde type A LTA zeolite in a weight ratio of 0.1 to 5.0, - the weight ratio of the first getter to the second getter is 0.1 to 5.0, and - The getter powder is characterized by an X 90 particle size distribution with values from 1.0 μm to 50.0 μm.

2. The getter composition according to claim 1, wherein the weight ratio of the first getter to the second getter is 0.1 to 2.

5.

3. The getter composition according to claim 1 or 2, wherein the getter powder is characterized by an X 90 particle size distribution with a value of 1.0 μm to 20.0 μm.

4. A dispensable paste comprising an epoxy resin or a phenolic resin or a mixture thereof, and the getter composition according to any one of claims 1 to 3, wherein the amount of the resin including the curing agent is 50 wt% to 90 wt% relative to the total amount of the paste, and the amount of the getter composition is 10 wt% to 550 wt% relative to the total amount of the paste.

5. The dispensable paste according to claim 4, wherein an additional coloring agent compound is added in an amount of 0.1 wt% to 10 wt% relative to the total amount of the paste.

6. The dispensable paste according to claim 5, wherein the coloring agent compound is a rare earth pigment or an organic heterocyclic compound.

7. The dispensable paste according to any one of claims 4 to 6, wherein the epoxy resin is selected from bisphenol F resin or bisphenol A resin, and the phenolic resin is poly[(phenyl glycidyl ether)-co-formaldehyde] resin.

8. The dispensable paste according to any one of claims 4 to 6, wherein the weight ratio of the first getter to the second getter is 0.1 to 2.

5.

9. A component for an electronic device, comprising at least one surface to which the paste according to any one of claims 4 to 8 has been dispensed.

10. The component according to claim 9, wherein the component is a cover for a hermetic package of the electronic device.

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