Hydraulic inorganic seminant composition

Abstract

A hydraulic inorganic cement composition comprising at least one compound having a water solubility of >10 g / L (at 20° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms, and at least one water-dispersible EVA copolymer.

Description

Summary of the Invention [Problem to be solved by the invention]

[0001] The present invention relates to a hydraulic inorganic cement composition which can be mixed with water to produce an aqueous hydraulic inorganic cement preparation which can be used to produce a hydraulically set inorganic cement composition, in particular in the form of an encapsulant for electronic components.

[0002] As used herein, the term "hydraulic" includes solidifying in the presence of water or after the addition of water.

[0003] In this specification, a distinction is made between hydraulically curable inorganic cement compositions, aqueous hydraulically curable inorganic cement preparations and hydraulically cured inorganic cement compositions. Aqueous hydraulically curable inorganic cement preparations, in particular in the form of a viscoelastic, for example pasty or flowable mass (also called "cement paste" or "cement glue"), can be produced from the hydraulic inorganic cement composition by mixing the latter with water. The aqueous hydraulic inorganic cement preparation can then be hardened and dried after its application to form a hydraulically cured inorganic cement composition in the form of a hard solid. Such a hard solid is also called "cement stone". This type of hydraulically cured inorganic cement composition is practically insoluble in water, i.e. substantially or completely insoluble in water.

[0004] The term "electronic components" as used herein encompasses passive electronic components as well as semiconductor modules, particularly those of electronic assemblies.

[0005] In the present specification, a semiconductor module is understood to mean an electronic assembly comprising at least one substrate (in the form of a circuit carrier), at least one semiconductor unit (semiconductor) and, if applicable, at least one passive electronic component. The at least one semiconductor unit itself may be partially or completely pre-encapsulated, for example with an epoxy resin-based sheath.

[0006] The term "electronic assembly" is used herein. An electronic assembly in the sense of the present invention comprises at least one substrate and at least one electronic component mechanically and electrically connected thereto. The mechanical and electrical connection may be a conductive soldering, sintering and / or adhesive connection. Furthermore, this type of electronic assembly may comprise elements providing an electrical connection such as bonding strips, bonding wires, clips, spacers and / or foils. Examples of electronic assemblies with or without frames include discrete components such as power discretes, power modules, voltage converters and certain sensors.

[0007] Examples of substrates include IMS substrates (insulated metal substrates), metal ceramic substrates such as AMB substrates (active metal brazed substrates) and DCB substrates (direct copper bonded substrates), ceramic substrates, PCBs (printed circuit boards), and lead frames.

[0008] Electronic components can be divided into active electronic components and passive electronic components.

[0009] Examples of active electronic components include diodes, LEDs (light emitting diodes), dies (semiconductor chips), IGBTs (insulated gate bipolar transistors), ICs (integrated circuits), and MOSFETs (metal oxide semiconductor field effect transistors).

[0010] Examples of passive electronic components include base plates, heat sinks, connectors, resistors, capacitors, inductors, antennas, transformers, chokes, coils, and sensors that do not form part of an electronic assembly.

[0011] The present invention has been made with the aim of providing a hydraulic inorganic cement composition from which an aqueous cement sealing compound can be produced for the manufacture of encapsulations of electronic components. The finished encapsulation should be characterized by good adhesion to the surfaces of a wide variety of materials, such as those that may be present on electronic components, especially on single electronic components. For example, surfaces made of ceramics, plastics, semiconductors such as silicon, silicon carbide, gallium nitride, metals such as copper, silver, nickel, gold, palladium, aluminum, etc.

[0012] Hydraulic inorganic cement compositions are disclosed, for example, in WO 2015 / 067441 (A1), WO 2015 / 193035 (A1), and WO 2019 / 025033 (A1).

[0013] It has now been found that this object can be achieved by providing a hydraulic inorganic cement composition comprising at least one water-soluble compound selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms, and at least one water-dispersible EVA copolymer (ethylene-vinyl acetate copolymer).

[0014] The present invention specifically relates to a hydraulic inorganic cement composition comprising 0.1-10% by weight, preferably 0.5-3% by weight, of at least one compound having a water solubility >10 g / L (at 20°C) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms, and 0.1-10% by weight, preferably 0.5-3% by weight, of at least one water-dispersible EVA copolymer.

[0015] For the sake of brevity, "a compound having a water solubility >10 g / L (at 20° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms" is also referred to as "compound A" hereinafter.

[0016] Preferably, the at least one compound A is present in a weight ratio of 0.8 to 3 relative to the at least one water-dispersible EVA copolymer.

[0017] The hydraulic inorganic cement composition according to the invention, which is present as a powder (in powder form), can be converted into an aqueous hydraulic preparation that can be used as a sealing compound by mixing with water. The aqueous sealing compound can be used to produce a water-hardened sealant for electronic components.

[0018] The hydraulic inorganic cement composition according to the invention comprises, in addition to the at least one compound A as described above and the at least one water-dispersible EVA copolymer as described above, a possible particulate filler and a possible further component, a hydraulic inorganic cement. The cement is a powder. The particles of the cement powder can have an absolute particle size, for example, in the range of up to 1 mm. The hydraulic inorganic cement can be, for example, a Portland cement, an alumina cement, a magnesium oxide cement or a phosphate cement known to the person skilled in the art. Phosphate cements, such as zinc phosphate cements or especially magnesium phosphate cements, are preferred. The hydraulic inorganic cement can, for example, constitute 2 to 95% by weight, preferably 3 to 40% by weight, of the hydraulic inorganic cement composition according to the invention.

[0019] At least one compound A preferably has at least one polar group, such as an ionic group or an amphoteric group. The 5- or 6-membered aromatic nitrogen heterocyclic ring system without other ring heteroatoms can be, for example, pyrrole, pyrazole, imidazole, triazole, tetrazole, pyridine, pyrimidine, pyridazine, pyrazine, or triazine. It can also be a condensed ring system. Thus, at least one compound A can be selected from the group consisting of the corresponding derivatives of pyrrole, pyrazole, imidazole, triazole, tetrazole, pyridine, pyrimidine, pyridazine, pyrazine, or triazine. Imidazole derivatives are preferred. The imidazole derivative particularly preferably used in the hydraulic inorganic cement composition according to the invention is the amino acid histidine.

[0020] It is speculated that the aromatic nitrogen heterocycle of at least one compound A has an adhesion-promoting effect, especially on metal surfaces. A complexation mechanism for metals such as copper, silver and aluminum is speculated here. At least one polar group, which is preferably present, can contribute to water solubility in aqueous hydraulic inorganic cement preparations. It is further speculated that at least one polar group, which is preferably present in the hydraulically set inorganic cement composition, can orient itself towards the cement matrix, which is likely to be more polar, while the nitrogen heterocycle structure can orient itself towards the metal surface, possibly in a complexation manner.

[0021] Said water-dispersible EVA copolymers can be produced by emulsion polymerization in an aqueous environment without the addition of organic solvents, followed by spray drying. In particular, water-redispersible EVA copolymer dispersion powders can be obtained in this way. Preference is given to water-redispersible EVA copolymer dispersion powders of this kind having a minimum film-forming temperature in the range of, for example, 0-4°C. Water-redispersible EVA copolymer dispersion powders are commercially available, which are sold, inter alia, as additives for dry mortars, for example by Wacker under the name VINNAPAS®.

[0022] The hydraulic inorganic cement composition according to the invention may in particular consist of the following components: (a) 2 to 95% by weight, preferably 3 to 40% by weight, of a cement selected from the group consisting of portland cement, alumina cement, magnesium oxide cement and phosphate cement; (b) 0.1 to 10% by weight, preferably 0.5 to 3% by weight, of at least one compound A, (c) 0.1 to 10% by weight, preferably 0.5 to 3% by weight, of at least one water-dispersible EVA copolymer; (d) 0 to 90% by weight, preferably 40 to 80% by weight, of at least one particulate filler, and (e) 0-30% by weight, preferably 2-15% by weight, of at least one component other than components (a)-(d). Components (a)-(e) total 100% by weight of the hydraulic inorganic cement composition according to the invention. In other words, the hydraulic inorganic cement composition according to the invention can consist of components (a), (b) and (c), or of components (a), (b), (c) and (d), or of components (a), (b), (c) and (e), or of components (a), (b), (c), (d) and (e).

[0023] Component (a) is a hydraulic inorganic cement. It is a powder. The cement powder particles can have an absolute particle size ranging, for example, up to 1 mm. The hydraulic inorganic cement is selected from the group consisting of Portland cement, alumina cement, magnesium oxide cement, and phosphate cement. Component (a) is preferably a phosphate cement, for example a zinc phosphate cement, or in particular a magnesium phosphate cement.

[0024] Phosphate cements particularly preferred as component (a) may consist of: (a1) 10 to 90% by weight, preferably 30 to 60% by weight, of at least one hydrogen phosphate selected from the group consisting of monohydrogen phosphates and dihydrogen phosphates of magnesium, calcium, and aluminum, and (a2) 90-10% by weight, preferably 70-40% by weight, of at least one compound selected from the group consisting of oxides, hydroxides and oxide hydrates of magnesium, calcium, iron, zinc, zirconium, lanthanum and copper. The sum of the weight percentages of components (a1) and (a2) is 100% by weight of component (a).

[0025] Component (a1) is at least one substance selected from the group consisting of magnesium monohydrogen phosphate, calcium monohydrogen phosphate, aluminum monohydrogen phosphate, magnesium dihydrogen phosphate, calcium dihydrogen phosphate and aluminum dihydrogen phosphate. In other words, it is at least one hydrogen phosphate selected from the group consisting of monohydrogen phosphate and dihydrogen phosphate of magnesium, calcium and aluminum. In particular, it is at least one hydrogen phosphate selected from the group consisting of monohydrogen phosphate and dihydrogen phosphate of magnesium and aluminum.

[0026] Component (a1) is for example a powder having an absolute particle size in the range up to 1 mm.

[0027] Component (a2) is at least one compound selected from the group consisting of oxides, hydroxides and oxide hydrates of magnesium, calcium, iron, zinc, zirconium, lanthanum and copper, in particular at least one compound selected from the group consisting of magnesium oxide, magnesium hydroxide, zirconium oxide, zirconium oxide hydrate and zirconium hydroxide, with magnesium oxide being particularly preferred.

[0028] Component (a2) is for example a powder having an absolute particle size in the range up to 1 mm.

[0029] For the sake of brevity, with regard to components (b) and (c), reference is made to the foregoing.

[0030] Optionally, but preferably, the component (d) present is at least one particulate filler which may be selected from the group consisting of mono-, oligo- and polyphosphates, in particular of magnesium, calcium, barium and aluminium, calcium sulfate; barium sulfate; silicates, mono- and double salts containing calcium, aluminium, magnesium, iron and / or zirconium; aluminates, mono- and double salts containing calcium, magnesium and / or zirconium; titanates, mono- and double salts containing calcium, aluminium, magnesium, barium and / or zirconium; zirconates, mono- and double salts containing calcium, aluminium and / or magnesium; zirconium dioxide; titanium dioxide; aluminium oxide; silicon dioxide, in particular in the form of silica and quartz; silicon carbide; aluminium nitride; boron nitride and silicon nitride. In this specification, a distinction is made between mono- and double salts of silicates, aluminates, titanates and zirconates. Representative of double salts are, for example, silicates, aluminates, titanates, and zirconates having two or more cations, rather than complex compounds, such as calcium aluminum silicate, lead zirconium titanate, etc.

[0031] Component (d) is for example a powder having an absolute particle size in the range up to 1 mm.

[0032] Optional component (e) is one or more components each different from components (a)-(d), such as flow improvers, set retarders (pot life extenders), defoamers, hydrophobizing agents, additives that affect surface tension, wetting agents, adhesion promoters, and fibers. Examples of fibers include glass fibers, basalt fibers, boron fibers, and ceramic fibers such as silicon carbide fibers and aluminum oxide fibers, rock wool fibers, wollastonite fibers, and aramid fibers.

[0033] The hydraulic inorganic cement composition according to the invention, in particular consisting of components (a), (b), (c), preferably further (d) and optionally (e), may be in the form of a one-component powder composition or in the form of two or more powder components, i.e. different separate components (separately stored or separately stored). In the case of a two-component or multi-component composition, the components comprise all components together, i.e. in particular components (a), (b) and (c), or (a) to (d), (a) to (e), or (a), (b), (c) and (e). The two or more components are stored separately from one another until they are used to produce the aqueous hydraulic inorganic cement preparation. In this case, it may be particularly preferred to store components (a1) and (a2) at least substantially separated from one another.

[0034] The aqueous hydraulic inorganic cement preparation can be produced from the hydraulic inorganic cement composition according to the invention, which may be in one-component, two-component or multi-component powder form, by mixing it with water. In the case of a two-component or multi-component system, the components can be mixed first to form a one-component hydraulic inorganic cement composition and then mixed with water. However, it is also possible to mix only one, some or all of the components first with water, for example to form a paste, and then further mixing can be carried out to form the aqueous hydraulic inorganic cement preparation. This kind of aqueous hydraulic inorganic cement preparation can be used to produce a hydraulically set inorganic cement composition, in particular in the form of an encapsulant for electronic components, which after its application can be hydraulically set and dried to form a hydraulically set inorganic cement composition in the form of a hard solid. The hard solid can in particular be the encapsulant for electronic components.

[0035] The aqueous hydraulic inorganic cement preparations according to the invention obtained by mixing with water can have a water content of, for example, 6 to 25% by weight.

[0036] The viscosity of a freshly produced (within 5 min of completion) aqueous hydraulic inorganic cement preparation can be, for example, in the range of 0.5-20 Pa·s (when measured with a rotational viscometer, interplate measurement principle, plate diameter 25 mm, measurement gap 1 mm, sample temperature 20 °C).

[0037] As mentioned above, the aqueous hydraulic inorganic cement formulation can be used as an aqueous sealing compound for electronic components. For the sake of brevity, the term "aqueous sealing compound" is also used below instead of "aqueous hydraulic inorganic cement formulation".

[0038] The aqueous sealing compound can be used to produce a water-cured encapsulant for an electronic component. Such a method includes the steps of: (1) providing an electronic component to be encapsulated; (2) providing an aqueous sealing compound prepared by mixing a hydraulic inorganic cement composition according to the present invention with water; (3) encapsulating the electronic component provided in step (1) with the aqueous encapsulating compound provided in step (2); (4) after completion of step (3), water curing the aqueous sealing compound that encapsulates the electronic components.

[0039] In step (1), an encapsulated electronic component is provided. With regard to the term "electronic component", reference is made to the above.

[0040] Regarding step (2), see above.

[0041] Preferably, step (3) is carried out immediately, for example within 60 minutes, preferably within 10 minutes, after completion of step (2), or after completion of preparation of the aqueous sealing compound.

[0042] In step (3), the electronic components provided in step (1) are encapsulated with the aqueous sealing compound provided according to step (2). Preferred application methods are casting, dipping and injection molding. Casting can be carried out using conventional methods known to those skilled in the art, for example by gravity-assisted, vacuum-assisted or pressure-assisted casting (compression molding). In this case, it may be preferred to encapsulate the electronic components to be encapsulated in half-shell molds and then fill them with the aqueous sealing compound. The encapsulant may be a partial or complete encapsulant. For example, when encapsulating a semiconductor module, the encapsulant may partially or completely encapsulate the electrical contact elements connected to the semiconductor unit, such as the bonding wires, strips and / or substrates. A partial encapsulant means that one or more of the contact elements are encapsulated in an incomplete manner and / or that one or more of the contact elements are not encapsulated, and a complete encapsulant means that all contact elements are completely encapsulated. However, casting can also be carried out, for example, such that the encapsulant is formed as a "glob top" known to those skilled in the art.

[0043] In step (4), which follows step (3), the aqueous sealing compound that encapsulates the electronic components is water cured. Of course, water curing begins as soon as the aqueous sealing compound is prepared, i.e., during or after completion of step (2).

[0044] Water curing can be carried out under ambient conditions, for example at an ambient temperature in the range of 20-25° C., and can take, for example, 1 minute to 6 hours. If the time is reduced, the operation can be carried out at a higher temperature, for example water curing is completed within a few seconds to 2 hours after the object temperature is less than 30° C. to 100° C.

[0045] It is preferred to dry the sealed body after water curing in order to remove chemically unbound water from the water-cured inorganic cement composition. This can be done later, but water curing can also be followed by forced drying for dehydration, for example at an object temperature of 80°C to 200°C for 0.5 to 6 hours. It may be preferred to go through several temperature stages. This drying can be done with vacuum assistance.

[0046] Comparative Examples V1 to V3 and Examples 1 to 4 according to the invention: 7 parts by weight of magnesium oxide powder, 2 parts by weight of magnesium dihydrogen phosphate powder, and 76 parts by weight of zirconium silicate powder with a maximum particle size of 100 μm were premixed to form a hydraulic inorganic magnesium phosphate cement composition. The premix was then mixed with histidine, water-redispersible EVA copolymer dispersion powder (VINNAPAS® 5044N from Wacker) and water according to the parts by weight in Table 1 to form an aqueous hydraulic magnesium phosphate cement preparation.

[0047] [Table 1]

[0048] The adhesion of the aqueous hydraulic magnesium phosphate cement formulations after application to copper and aluminum oxide surfaces and hydraulic hardening was measured as follows: A silicone mask with six square cutouts, each 5x5 cm, was placed on a flat copper or aluminum oxide ceramic plate. The aqueous hydraulic magnesium phosphate cement formulation in question was introduced into the cutouts using a syringe to a fill level of 3 mm. The cement formulation was then water cured at 20°C for 2 hours. The silicone mask was then removed and the copper or aluminum oxide ceramic plate with the water cured square cement samples was treated in a laboratory furnace by increasing the furnace temperature from 20°C to 90°C at a heating rate of 1°C / min and maintaining at 90°C for 1 hour. The furnace temperature was increased to 160°C at a rate of 1°C / min and held at 160°C for 1 hour. The plate was then cooled to 20°C at a rate of 1°C / min. The shear strength was then measured in sixfold using a DAGE 2000 measuring device from the company Dage (Germany). The cement samples were sheared using a shear chisel with an edge length of 6 mm at a shear height of 2 / 3 of the sample height while maintaining a shear rate of 300 μm / s. To improve the measurement accuracy, the shear force of the 100 kg load cell was reduced to 20 kg. The obtained measurement results are shown in Table 2.

[0049] [Table 2]

Claims

1. A hydraulic inorganic cement composition comprising at least one water-soluble compound selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms, and at least one water-dispersible EVA copolymer.

2. 2. The hydraulic inorganic cement composition according to claim 1, comprising 0.1-10% by weight of at least one compound having a water solubility >10 g / L (at 20° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms, and 0.1-10% by weight of at least one water-dispersible EVA copolymer.

3. 3. The hydraulic inorganic cement composition of claim 2, wherein said at least one compound having a water solubility >10 g / L (at 20° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms is present in a weight ratio of 0.8 to 3 with respect to said at least one water-dispersible EVA copolymer.

4. 4. Hydraulic inorganic cement composition according to claim 2 or 3, comprising hydraulic inorganic cement, said at least one water-dispersible EVA copolymer, possible particulate fillers and possible further components in addition to said at least one compound having a water solubility > 10 g / L (at 20 ° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms.

5. 5. The hydraulic inorganic cement composition according to claim 4, wherein the hydraulic inorganic cement is a Portland cement, an alumina cement, a magnesium oxide cement, or a phosphate cement.

6. 6. The hydraulic inorganic cement composition of claim 4 or 5, wherein the hydraulic inorganic cement comprises 2 to 95% by weight of the hydraulic inorganic cement composition.

7. A hydraulic inorganic cement composition comprising: (a) 2 to 95 wt. % of a cement selected from the group consisting of portland cement, alumina cement, magnesium oxide cement, and phosphate cement; (b) 0.1-10% by weight of at least one compound selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system containing no other ring heteroatoms, the compound having a water solubility of >10 g / L (at 20° C.); (c) 0.1 to 10 wt. % of at least one water-dispersible EVA copolymer; (d) 0 to 90 weight percent of at least one particulate filler; (e) 0 to 30% by weight of at least one component other than components (a) to (d); A hydraulic inorganic cement composition, wherein components (a)-(e) total 100% by weight.

8. Component (a) is (a1) 10 to 90% by weight of at least one hydrogen phosphate selected from the group consisting of monohydrogen phosphates and dihydrogen phosphates of magnesium, calcium, and aluminum; (a2) 90 to 10% by weight of at least one compound selected from the group consisting of oxides, hydroxides, and oxide hydrates of magnesium, calcium, iron, zinc, zirconium, lanthanum, and copper; 8. The hydraulic inorganic cement composition according to claim 7, wherein the sum of the weight percentages of components (a1) and (a2) is 100% by weight.

9. 9. The hydraulic inorganic cement composition according to any one of claims 2 to 8, wherein the at least one compound having a water solubility > 10 g / L (at 20 ° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms is selected from the group consisting of derivatives of pyrrole, pyrazole, imidazole, triazole, tetrazole, pyridine, pyrimidine, pyridazine, pyrazine or triazine.

10. 10. The hydraulic inorganic cement composition of claim 9, wherein the at least one compound having a water solubility >10 g / L (at 20° C.) selected from the group consisting of 5-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms and 6-membered compounds having an aromatic nitrogen heterocyclic ring system without other ring heteroatoms is an imidazole derivative.

11. A hydraulic inorganic cement composition according to any one of claims 1 to 10, in the form of a one-component powder composition or in the form of two or more different separate powder components.

12. An aqueous hydraulic inorganic cement preparation produced by mixing the hydraulic inorganic cement composition according to any one of claims 1 to 11 with water.

13. 13. Use of the aqueous hydraulic mineral cement preparation according to claim 12 for producing a hydraulic mineral cement composition in the form of an encapsulant for electronic components.

14. 1. A method for producing a water-cured encapsulant for an electronic component, comprising the steps of: (1) providing an electronic component to be encapsulated; (2) providing an aqueous sealing compound prepared by mixing the hydraulic inorganic cement composition according to any one of claims 1 to 11 with water; (3) sealing the electronic component provided in step (1) with the aqueous sealing compound provided in step (2); (4) after completion of step (3), water curing the aqueous sealing compound that encapsulates the electronic component.

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