EP1668078A1

EP1668078A1 - Potting compound, use thereof and components encapsulated in said potting compound

Info

Publication number: EP1668078A1
Application number: EP04766551A
Authority: EP
Inventors: Matthias Burkhardt; Arnulf Rupp; Barbara Lehner; Wolfgang ÜBLER; Caroline Cassignol
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2003-09-30
Filing date: 2004-08-20
Publication date: 2006-06-14
Also published as: WO2005033203A1

Abstract

The invention relates to a potting compound based on epoxy resins, which comprise mixtures of bisphenol-F and bisphenol-A diglycidyl ethers and highly functional epoxy-phenol novolaks. A blend of two hardener components, an amine and an imidazole component is added to the potting compound as a hardener, both hardener components having a solid form at ambient temperature. The potting compound contains a filler with a multi-modal particle size distribution, which has been optimised to produce the maximum fill degree possible with the minimum viscosity possible. Said potting compound remains stable during storage at ambient temperature for several months and can nevertheless be processed at a moderately increased temperature with a good pot life. After being subjected to stress, constant thermomechanical characteristics can be guaranteed for the potting compound over a wide temperature range.

Description

description

Potting compound, use thereof and components encased in the potting compound

The invention relates to a casting compound based on epoxy resins with good thermal, mechanical and electrical properties, which comprise mixtures of bisphenol-F or bisphenol-A diglycidyl ethers with more highly functional epoxy-phenol novolaks and which consist of good thermomechanical properties show a wide temperature cycle range.

Potting compounds or casting resins based on epoxy are known, in particular also those for use in electronics and electrical engineering.

These casting resins are widely used by companies such as Kulicke & Soffa (EASY FILL ™ series), Nagase (e.g. R3400EX-5), Loctite (Loctite and Dexter-Hysol series), Emerson & Cuming (Stycast series), Cookson (NUF series, MUF series, UF series), Delo (e.g. ACABOND), etc. These commercially available products are either two-component and must be mixed in an additional step before processing or so-called "frozen products", ie products premixed from two components and stable at -40 ° C.

The potting compounds tested by Rhenatech (e.g. 4007 FR), Wacker (Silgel 612, RT 741) or Höhne (e.g. PU 300) for the encapsulation of the electrical and electronic components did not have sufficient thermal shock resistance and caused delamination from the housing wall or blistering guided.

There is therefore a need to create better casting compounds which are one-component and are suitable for electrical casting. The object of the present invention is therefore to provide casting compounds which are temperature-stable up to 200 ° C., adhere well to thermoplastics, such as, for example, polyphenylene sulfide (PPS), polyetherimide (PEI) and polyamide (PA6.6), and in addition to good ones thermomechanical also show the required electrical properties, e.g. sufficient high voltage strength. In particular, it is an object of the invention to provide a casting compound for ignition transformers, for example in automotive lighting.

The invention relates to a resin formulation, at least comprising the following components: (A) a bisphenol F and / or bisphenol A diglycidyl ether, (B) a more highly functional epoxy-phenol novolak component, (C) a hardener component, the one comprises polyamine which is solid at room temperature and an imidazole which is also solid at room temperature, and (D) a filler mixture with optimized multimodal particle size distribution.

In addition, the use of a casting compound with at least the components (A) a bisphenol F and / or bisphenol A diglycidyl ether, (B) a more highly functional epoxy phenol novolak component, (C) a hardener component, which is a at room temperature solid polyamine and an imidazole solid at room temperature, ₍ (D) a filler mixture with optimized multimodal particle size distribution, for the encapsulation of electrical and / or electronic components.

The invention also relates to a molding material and / or a component which consists of a casting compound with at least the components (A) a bisphenol F and / or bisphenol A diglycidyl ether,

(B) a higher functional epoxy phenol novolak component,

(C) a hardener component which comprises a polyamine which is solid at room temperature and an imidazole which is also solid at room temperature,

(D) a filler mixture with optimized multimodal particle size distribution was produced, object of the invention.

Advantageously, a molded body made from the casting compound has a high voltage strength of 50 kV / mm.

Advantageously, a molded body made from the casting compound has a thermal stability of at least 4000 hours at 150 ° C. and 1000 hours at 200 ° C.

In the context of "stable" is meant that a resin formulation in the hardened state after a permanent temperature test of e.g. 1000h at 200 ° C shows mass losses of less than 10%.

The mixtures according to the invention of bisphenol-F or bisphenol-A diglycidyl ethers with higher functional epoxy-phenol novolaks, hardened with polyamines and imidazoles which are solid at room temperature, provide moldings which are temperature-stable up to 200 ° C. on thermoplastics such as e.g. Polyphenylene sulfide (PPS), polyetherimide (PEI) and polyamide (PA6.6) adhere well and show high voltage resistance, advantageously approx. 50 kV / mm.

Bifunctional bisphenol A diglycidyl ethers, bisphenol F diglycidyl ethers, but also hydrogenated bisphenol A and bisphenol F diglycidyl ethers and mixtures of these epoxy resins are used as component A. Other diglycidyl ethers that can be used include, for example, other aromatic and / or cycloaliphatic epoxy resins, as described in the "Handbook of Epoxy Resins" by Henry Lee and Kris Neville, McGraw-Hill Book Company 1967, and in the monograph by Henry Lee "Epoxy Resins", American Chemical Society 1970. The average molecular weight M _{n of} the diglycidyl ethers is generally 150 to 4000, preferably 300 to 1800.

As component B, the higher functional epoxy phenol novolak, a component is used which combines the thermal stability of a phenolic main chain with the reactivity and the versatility of an epoxy resin in one molecule. For example, a product from the "Epoxy Novolac Resins" series from DOW Chemical Company can be used and / or epoxy-dicyclopentadiene novolaks, such as those sold by Dainippon Inc.

Aromatic polyglycidyl ethers, such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether and bisphenol S diglycidyl ether, polyglycidyl ether of phenol / formaldehyde and cresol / formaldehyde resins, resorcinol diglycidyl ether, tetrakis (di) glycidyl ether, tetrakis (p) glycidyl ether or polyglycidyl esters of phthalic, isophthalic and terephthalic acid and of trimellitic acid, N-glycidyl compounds of aromatic amines and heterocyclic nitrogen bases, such as N, N-diglycidylaniline, N,, O-triglycidyl-p-aminophenol, triglycidyl isocyanurate and N, , NN ^x -tetraglycidyl-bis- (p-aminophenyl) methane, hydantoin epoxy resins and uracil epoxy resins as well as di- and polyglycidyl compounds of polyhydric aliphatic alcohols, such as 1,4-butanediol, trimethylolpropane and polyalkylene glycols become. Oxazolidinone-modified epoxy resins are also suitable. Such compounds are already known (see: "Angew. Makromol. Chem.", Vol. 44 (1975), pages 151 to 163, and US Pat. No. 3,334,110); the reaction product of bisphenol A diglycidyl ether with diphenylmethane diisocyanate (in the presence of a suitable accelerator) may be mentioned as an example. The polyepoxy resins can be present individually or as a mixture in the preparation of the blends. The following have proven to be particularly advantageous for the application according to the invention: as component A, a bisphenol F diglycidyl ether with low viscosity, such as Bakelite EPR 158, and as component B a phenol novolak epoxide, such as DEN 431 or DEN 438 der Dow Chemicals.

The mixture comprises 5 to 60 parts, preferably 10 to 50 parts of component (A) and 30 to 93, preferably 40 to 90, and particularly preferably 50 to 85 parts of component (B) and 3 to 20, preferably 4 to 17, particularly preferably 5 to 15 parts of a hardener which is solid at room temperature and / or a hardener mixture which is solid at room temperature.

The hardener component comprises a polyamine which is solid at room temperature and an imidazole which is also solid at room temperature. For example, a product from Ajinomoto Co. Inc., for example from the Ajicure PN-D series, can be used as the amine component. The product Ajicure PN-D, Ajicure PN-23 and / or Ajicure PN-40J from Ajinomoto Co can advantageously be used as an amine component.

An imidazole which is solid at room temperature is preferably used as the imidazole component. For example, they have

Products from Air Productsand Chemicals, Inc., which are sold under the trade name "CUREZOL", have proven themselves in the mixture. For example, imidazoles from this series, such as CUREZOL -2MZ; -2E4MZ; -C11Z; -C17Z; 2PZ; -2EZ; -2IZ; -2P4MZ; -2MZ-azines; 2E4MZ-Azine and CllZ-Azine as well as mixtures of these components are used according to the invention. The component "4-diamino-6 (2'-methylimidazoleyl- (l ') ethyl-S-triazines" "CUREZOL 2-MZ-AZINE-S" from this series is particularly preferably used.

Each of the hardener components described would initiate epoxy resin hardening on its own. By mi However, the reactivity of the formulation can be varied by combining the components with one another.

The mixing ratios of the two hardener components, the amine and the imidazole component, were set so that the reactivity is optimal for the desired application. For example, imidazole to amine can be from 0.3: 1 to 1: 5, preferably 0.7: 1 to 1: 4 and particularly preferably 0.4: 1.

Overall, the hardener in the mixture is present in a proportion of 3 to 30 parts, preferably 4 to 25 and particularly preferably in the range between 6 and 20 parts.

Despite the relatively high degree of crosslinking (for example Tg values> 150 ° C.), the molding materials according to the invention are notable for good thermomechanical properties (adjusted modulus of elasticity, fracture toughness, flexural strength). This prevents cracking and delamination after a temperature shock test.

The type and particle size distribution of the fillers used were optimized in the formulations according to the invention in such a way that the highest possible degree of filling with the lowest possible viscosity and thus a low expansion coefficient and a bubble-free casting could be achieved. The calculation of the most favorable grain size distribution for determining the optimal packing density was carried out with the aid of the simulation program, which is protected in the context of DE 10319308.1.

Design example:

The epoxy casting resin suitable for potting electrical and electronic components preferably consists of 10 to 50 parts of a bisphenol F or bisphenol A

Diglycidyl ether, 50 to 85 parts of a higher functional epoxy phenol novolak and 5 to 15 parts of a room temperature temperature solid polyamine, 1 to 5 parts of an imidazole solid at room temperature, 0 to 50 parts of filler and various additives.

The casting resin is processed at a moderately elevated temperature (e.g. 60 ° C) under vacuum. At temperatures of 50 to 70 ° C, the casting resins have long pot lives (e.g. 10h at 60 ° C), significantly reduced viscosities (e.g. at 25 ° C 200Pas, at 60 ° C 10 Pas) and no sedimentation tendency of the fillers.

To cast the ignition transformer of the D1 + lamp, a cast resin formulation filled with 35% by weight of splintery quartz was used. The potting was carried out at 100 mbar with a dosing rate of 0.2 ml / s and a resin temperature of

60 ° C and a component temperature of 100 ° C. It has been shown that this potting compound is suitable for the rational production of sophisticated components. The potted transformer complies with the customer-specific requirements described under 1.

The potting compounds that are produced according to the invention have a wide process window for the potting and thus offer a rational and reliable assembly technology for sophisticated electrotechnical and electronic products. Short curing times of <lh at 150 ° C can be achieved. The thermomechanical properties, which remain constant over a wide temperature range, ensure that the requirements placed on a potting resin for electrical and / or electronic components are met. For example, they show:

- good wetting of the components and the thermoplastic housing surface,

- an adjusted viscosity to ensure void-free filling,

- good adhesion to thermoplastic housing materials, ie no delamination - after exposure to temperature shock (4000 cycles - 40/150 ° C), - after climatic stress (25 ° C / 55 ° C-90% / 95% rel.humidity), - after vibration exposure at 13.5V every 20h in x, y and z axis at 12-1002HZ,

- a high voltage strength> 50kV / mm,

- Thermal stability in the range between 150 and 200 C over 4000 h. The invention relates to a casting compound based on epoxy resins, which comprise mixtures of bisphenol F or bisphenol A diglycidyl ethers with higher functional epoxy phenol novolaks. A mixture of two hardener components, an amine and an imidazole component, is added to the casting compound as hardener, both hardener components being present as solids at room temperature. It contains filler with a multimodal particle size distribution, which has been optimized in such a way that the highest possible degree of filling is achieved with the lowest possible viscosity. This potting compound has a shelf life of several months at room temperature and can still be processed at a moderately elevated temperature with good pot life. After loading, constant thermomechanical properties are guaranteed over a wide temperature range.

Claims

claims

1. Resin formulation comprising the following components:

(A) a bisphenol F and / or bisphenol A diglycidyl ether, (B) a higher functional epoxy phenol novolak component,

(C) a hardener component which comprises a polyamine which is solid at room temperature and / or an imidazole which is also solid at room temperature

(D) a filler mixture with optimized multimodal grain size distribution.

2. Resin formulation according to claim 1, wherein the multimodal particle size distribution of the filler mixture has been optimized such that the highest possible degree of filling is achieved with the lowest possible viscosity.

3. Resin formulation according to one of claims 1 or 2, which comprises at least components A, B and a hardener, component A in an amount of 5 to 60 parts, component B in an amount of 30 to 93 parts and a hardener component in an amount of 3 to 30 parts are included.

4. Resin formulation according to one of the preceding claims, in which the amine and the imidazole component of the hardener are in a mixing ratio of 0.5: 1 to 5: 1 to one another.

5. Resin formulation according to one of the preceding claims, which are stable for several months at room temperature and yet have pot lives of> 10 hours at a temperature of approx. 50 ° C.

6. Use of a resin formulation with components (A) a bisphenol F and / or bisphenol A diglycidyl ether,

(B) a higher functional epoxy phenol novolak component, (C) a hardener component comprising a room temperature solid polyamine and a room temperature solid imidazole and

(D) a filler mixture with a multimodal, optimized particle size distribution, the rheological properties of which are set in such a way that it is suitable for casting or painting electrical and / or electronic components / assemblies.

7. Component that with a potting compound with at least the components

(A) a bisphenol F and / or bisphenol A diglycidyl ether,

(B) a higher functional epoxy-phenol novolak component, (C) a hardener component which comprises a polyamine which is solid at room temperature and an imidazole which is also solid at room temperature, and (D) a filler with an optimized multimodal particle size distribution. was enveloped.

8. The component according to claim 7, which has at least one of the following properties: a high voltage strength of 50 kV / mm, a temperature shock resistance of 300 cycles -40/150 ° C, a permanent temperature resistance of 4000h 150 ° C or 1000h at 200 ° C, - has a moisture / heat resistance of 25/55 ° C and 90/95 rH, and / or - has a vibration resistance at 13.5V per 20h in x, y and z-axis at 12-1002Hz.