WO2007017307A1

WO2007017307A1 - Uv-curable and thermosetting epoxy resin lacquer for electronic subassemblies in humid spaces

Info

Publication number: WO2007017307A1
Application number: PCT/EP2006/063476
Authority: WO
Inventors: Grit Stelle; Barbara Lehner; Wolfgang ÜBLER
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-08-08
Filing date: 2006-06-22
Publication date: 2007-02-15

Abstract

The invention relates to a UV-curable and thermosetting epoxy resin formulation comprising a) ≥ 65 to ≤ 95 percent by weight of an epoxy resin component, b) ≥ 0.5 to ≤ 10 percent by weight of a hydroxyl component, c) ≥ 0.1 to ≤ 3 percent by weight of a photoinitiator component, d) ≥ 0.5 to ≤ 3 percent by weight of a thermal initiator component, e) ≥ 2 to ≤ 30 percent by weight of a filler component, and f) ≥ 0.1 to ≤ 5 percent by weight of an additive component, the percentages being in relation to the total weight of the epoxy resin formulation.

Description

description

UV- and thermally curable epoxy paint for electronic assemblies in damp rooms

The invention relates to a UV and thermally curable epoxy resin formulation and its use for covering electronic and electrical components and assemblies.

Electrical or electronic components applied to a substrate such as a substrate are usually covered with cast resins or housings to protect them from dust, moisture or mechanical damage. These casting resins are usually reactive resins which are applied to the components and assemblies and cured.

Casting resins, for example one- and two-component epoxy resin formulations which are UV and thermally curable, are known in the prior art. Two-component epoxy resin formulations must either be mixed prior to processing or stored as a premix at low temperatures and processed within a few hours. Known UV and thermally curable one-component resin formulations sometimes require curing temperatures of up to 150 ^° C. for thermal post-curing.

A disadvantage of silicone coatings is, for example, that they may tend to form bubbles during processing, in particular during crosslinking. Furthermore, silicone-based covering compounds can only insufficiently protect components against moisture.

For example, the package design of circuits requires that the casting resin used completely cover higher devices, such as integrated circuits, and maintain the desired shape beyond the curing process. In addition, the cast resin columns of the arrangement well underflow and connecting pins, also called component legs, well behind. However, commercially available casting resins and paints often have too high or too low a viscosity. This can lead to insufficiently covering elevated components or, for example, flowing the resin into openings for the through-connection of later-to-mount components and closing them.

The object of the present invention is to provide a cast resin material which overcomes at least one of the aforementioned disadvantages of the prior art, in particular protects the components from moisture and satisfies the stated requirements for the application.

This object is achieved by a UV and thermally curable epoxy resin formulation, wherein the epoxy resin formulation based on the total weight of the epoxy resin formulation comprises the following components: a. > 65 wt .-% to <95 wt .-% epoxy resin component; b. > 0.5 wt .-% to <10 wt .-% hydorxyl component; c. > 0, 1 wt .-% to <3 wt .-% photoinitiator component; d. > 0.5 wt .-% to <3 wt .-% thermal initiator component; e. > 2% by weight to <30% by weight of filler component; f. > 0, l wt .-% to <5 wt .-% additive component.

Unless otherwise stated, the weight percentages of the respective components are chosen so that the total weight of the respective components does not exceed 100% by weight, based on the total formulation.

Another object of the present invention is the use of the epoxy resin formulation for covering electrical and electronic components and assemblies.

Further advantageous embodiments of the invention will become apparent from the dependent claims. Surprisingly, it has been found that the epoxy resin formulation according to the invention can effectively protect moisture-sensitive components such as capacitors, integrated circuits and processors from penetrating moisture or water. The advantages of the epoxy resin formulation according to the invention are realized in particular by the low water vapor permeability of the cured epoxy resin formulation film. Also advantageous is the good adhesion of the epoxy resin formulation to the substrate and to the component surfaces. This combination of the properties of the epoxy resin formulation according to the invention can advantageously reduce or even prevent penetration of water along the interfaces and thus provide improved protection of the components from moisture.

In preferred embodiments, the epoxy resin formulation, based on the total weight of the epoxy resin formulation, has the following components: a. > 70 wt .-% to <90 wt .-%, preferably> 75 wt .-% to <88 wt .-% epoxy resin component; b. > 1 wt .-% to <8 wt .-%, preferably> 3 wt .-% to ≤ 7.5 wt .-% hydroxyl component; c. > 1 wt .-% to <2.5 wt .-%, preferably ≥1.5 wt .-% to <2 wt .-% of photoinitiator component; d. > 0.7 wt .-% to <2 wt .-%, preferably> 1 wt .-% to <1.7 wt .-% thermal initiator component; e. > 3 wt .-% to <20 wt .-%, preferably> 5 wt .-% to <10 wt .-% filler component; and / or f. > 0.4 wt .-% to <3 wt .-%, preferably> 1 wt .-% to <1.4 wt .-% additive component.

Epoxy resin components based on aromatic and / or cycloaliphatic epoxy resins are preferably usable as the epoxy resin component. Particularly preferred epoxy resin based aromatic epoxides are, for example, selected from the group comprising epoxy resins based on bisphenols, di- or polyhydroxyaromatics, polyarylalkyls with phenolic OH groups, compounds of the glycidyl ether ester type, for example para-hydroxybenzoic acid glycidyl ether esters, glycidyl esters of polycarboxylic acids with an aromatic nucleus, such as hexahydrophthalic acid or phthalic acid. A preferred cycloaliphatic epoxy resin component is, for example

3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexanecarboxylate. Further preferred among the cycloaliphatic epoxy resins are pure cycloaliphatic epoxy resins which have a low ion content. Cationically curable and solvent-free epoxy resins are preferably usable.

The proportion of the epoxy resin component in the epoxy resin formulation according to the invention is preferably higher than is customary. For the purposes of the invention, the term "epoxy resin" is to be understood as meaning both uniform epoxy resins and mixtures of different epoxy resins. It is particularly preferable to use aromatic and / or cycloaliphatic epoxy resins, it also being possible to use mixtures of aromatic epoxy resins, cycloaliphatic epoxy resins and / or mixtures of both. In particularly preferred embodiments, the epoxy resin component comprises only aromatic and / or cycloaliphatic epoxy resins. In very particularly preferred embodiments, the epoxy resin component comprises> 70% by weight to <90% by weight, preferably> 75% by weight to <88% by weight, based on the total weight of the epoxy resin formulation, aromatic epoxy resins or cycloaliphatic epoxy resins.

The advantages of the epoxy resin formulation according to the invention are in particular caused by the epoxy resin component, which cause a low moisture absorption and a low permeability to water vapor of the cured epoxy resin formulation. Surprisingly, it has been found that, in particular, the use of epoxy resin components based on aromatic and / or cycloaliphatic epoxy resins can bring about improved protection of the components from moisture. Advantageously, in particular epoxy resin components comprising aromatic and / or cyclo-aliphatic Epoxy resins reduce the water vapor permeability of the cured epoxy formulation film and also protect moisture sensitive components.

In further preferred embodiments, the epoxy resin formulation comprises at least one polyol as the hydroxyl component, preferably a polyol selected from the group comprising aliphatic diols and / or aliphatic triols. Particularly preferred are low molecular weight polyols, very particularly preferably, for example, 1, 2-propanediol. Usable as the hydroxyl component is at least one aliphatic diol or at least one aliphatic triol, preferably usable are mixtures of aliphatic diols or mixtures of aliphatic diols and aliphatic triols. In particularly preferred embodiments, the hydroxyl component comprises only polyols selected from the group comprising aliphatic diols, aliphatic triols and / or mixtures thereof.

The usable hydroxyl-containing organic compounds can advantageously have a positive influence on the UV and thermal reactivities of the epoxy resin formulations. In particular, the aliphatic diols and triols which can preferably be used have a positive effect on the curing process, in particular the curing rate, of the epoxy resin formulation. This can lead to a marked improvement in the properties of the cured epoxy resin formulation coating, which can have improved adhesion of the epoxy resin formulation to the substrate and / or components, in particular when using mixtures of low molecular weight diols or mixtures of diols and triols. It is of particular advantage that the epoxy resin formulation has good adhesion both to the substrate, for example to solder resists, and to the device surfaces, which are formed, for example, from epoxy polymer molding compound and / or metallic surfaces such as brass, whereby the penetration of water along the interfaces reduced or even can be prevented. Thus, not only the Moisture-sensitive electrical and electronic components themselves are better protected against the ingress of water, but also the interfaces, which often allow the penetration of water with less good adhesion.

To initiate the curing of the epoxy resin formulation, an initiator mixture comprising a photoinitiator component and a thermal initiator component is preferably used. The epoxy resin formulation of the invention can thus be cured by UV radiation and / or thermally, wherein the UV and the thermal curing can optionally be carried out simultaneously or sequentially. Preferably, first curing by UV irradiation followed by thermal curing of shaded areas. This "dual cure" mechanism, which describes the combination of UV and thermal cure, allows UV curing at low temperatures, for example, by short UV irradiation, as well as a thermal curing step to cure shadowed areas, for example Gaps under components or behind connection pins or component legs that are poorly or not at all reached by UV radiation.

In particular, the UV curing allows rapid curing of the covering compound by UV irradiation. In preferred embodiments, cure may already be achieved by exposure times in the range of 10 seconds to 45 seconds. By UV curing at low temperatures, advantageously, an increase in viscosity can be achieved, so that the coverage of very irregular component topographies without flowing away of the formulation is made possible. The inaccessible to the irradiation areas, the so-called exposure shadows can be reacted by thermal curing reaction.

Preferably, both curing steps follow the cationic mechanism, resulting in homogeneous cure results can. Accordingly, the epoxy resin formulation preferably contains at least one cationic photoinitiator or at least one cationic photoinitiator system. Preferred photoinitiators are those based on organic onium salts, in particular based on aromatic sulfonium salts. For example, it is possible to use phenacylsulfonium salts, hydroxyphenylsulfonium salts and sulfoxonium salts, or onium salts which are excited by a sensitizer, and organic silicon compounds which release a silanol on UV irradiation in the presence of organoaluminum compounds.

Particularly preferred photoinitiators are triarylsulfonium salts and / or thiolanium salts.

As the anion of the sulfonium salts, hexafluoroantimonate has been found to be particularly advantageous. In preferred embodiments of the epoxy resin formulation according to the invention, the photoinitiator component accordingly comprises a triaryl sulfonium hexafluoroantimonate and / or a thiolanium hexafluoroantimonate. In particularly preferred embodiments, the photoinitiator component comprises only triarylsulfonium hexafluoroantimonate or only thiolanium hexafluoroantimonate, in very particularly preferred embodiments the photoinitiator component comprises triarylsulfonium hexafluoroantimonate and thiolanium hexafluoroantimonate.

At shaded areas, for example in columns under components or behind connection pins or component legs, hardening is achieved by a thermally activatable element

Initiator, preferably effected by a latent thermal initiator. Preferably, the thermal initiator component comprises a thiolanium salt. Hexafluoroantimonate has proved to be particularly advantageous as the anion of the thiolanium salts. Preferably, the thermal initiator component comprises a thiolanium hexafluoroantimonate. Especially preferred Benzylthiolanium hexafluoroantimonates are of the general structure (1) below:

in which :

R ¹ = hydrogen, alkyl, aryl, alkoxy, thiol ether, halogen, CN or NO ₂ ;

R ² = hydrogen, alkyl or aryl; R ³ = hydrogen, alkyl or aryl or an aromatic system fused to the thiolane ring.

Unsubstituted benzylthiolanium salts are preferably used, in particular benzylthiolanium hexafluoroantimonate.

A particularly preferred anion of the thiolanium salts is hexafluoroantimonate. In particularly preferred embodiments, the thermal initiator component comprises only thiolanium hexafluoroantimonate, preferably benzylthiolanium hexafluoroantimonate. It is advantageous that hexafluoroantimonate can provide a sufficient latency of the initiators, in particular of the thermal initiators. For the purposes of the invention, the term "latency" is to be understood as meaning the reduced stability of the initiator against UV radiation and temperature which makes initiation possible A particular advantage is achieved in that the thiolanium hexafluoroantimonate has both sufficient stability and excitation, as well as a sufficient latency, which makes an excitation possible, can provide.

Of particular advantage is that curing at temperatures can be achieved below 100 ⁰ C by the use of Thiolaniumhexafluoroantimonate. Such a small one Temperature of the thermal curing can advantageously lead to the adhesion of the epoxy resin formulation to the substrate is further improved and a high crosslinking density of the epoxy resin formulation can be achieved. These properties can further improve the

Moisture barrier effect of the cured epoxy resin formulation contribute.

A particular advantage of curing below 100 ^° C. is achieved by making it possible to use it in a large number of electrical and electronic components, which can only be coated poorly or not at higher temperatures, since many, above all, electronic components have temperatures above 100 ^° C. not tolerate. The use of thiolanium hexafluoroantimonate can also allow use of the epoxy formulation for such devices, and provide wider usability.

In most preferred embodiments of the epoxy resin formulation, the thermal initiator component and the photoinitiator component comprise a thiolanium hexafluoroantimonate. For example, the thermal initiator component and photoinitiator component may comprise only thiolanium hexafluoroantimonate. This may realize the advantage that UV and latent thermal initiator components may be based on a compound.

The epoxy resin formulation of the invention further comprises a filler component. This filler component may contain conventional fillers useful in the formulation of epoxy resin formulations wherein the surface of the filler particles may also be coated or otherwise chemically treated. Preference is given to inorganic filler materials, for example aluminum oxide, aluminum hydroxide,

Calcium carbonate, magnesium oxide, glass or quartz material. It has proven to be advantageous if the filler component fused silica and / or quartz flour. In particularly preferred embodiments, the filler component is fused silica and / or quartz flour.

An advantage of using fused silica and / or quartz powder is that it can provide a low coefficient of expansion of the formulations and, for example, cracks and fractures during thermal cycling of covered assemblies during operation can be avoided.

However, usable filler materials are not limited to inorganic materials, also preferred are organic materials, for example, based on other plastics or polymers usable.

It may also be advantageous to use mixtures of inorganic and organic fillers.

Filler particles of any shape can be used, but spherical particles are preferred for realizing the good flow properties of the epoxy resin formulation. Smaller filler particles can improve the flowability of the formulation, preferred particle size of the particles are <25 .mu.m, preferably <20 .mu.m, more preferably <15 .mu.m, more preferably <10 .mu.m and most preferably <5 .mu.m.

According to the invention, the epoxy resin formulation contains a comparatively small proportion of fillers. As a lower limit, a minimum proportion of 2% by weight of filler component has proved favorable. Furthermore, it was found in the investigations that a proportion of the filler component above 30 wt .-% causes an unfavorable change in the properties of the epoxy resin formulation. In contrast, the proportion of the epoxy resin component in the epoxy resin formulation according to the invention is higher than is customary. The ratio of the proportions of the epoxy resin component to the filler component is preferably at least 2: 1, preferably the ratio of epoxy resin component to filler component is in the range from 2: 1 to 30: 1, preferably in the range from 5: 1 to 20: 1, more preferably in Range from 12: 1 to 18: 1, and most preferably in the range of 13: 1 to 15: 1. In contrast, known casting resin or epoxy resin formulations frequently have a ratio of resin component to filler component of approximately 1: 2.

The inventively low content of filler component or the increased proportion of epoxy resin advantageously contributes to the fact that the cured epoxy resin formulation has a reduced moisture absorption and a reduced water vapor permeability. Of particular advantage is further that on the one hand a good underflow of gaps and backflow of terminal pins or component legs, on the other hand, the complete coverage of high and / or irregular components is made possible without the epoxy resin formulation flows into immediately adjacent openings, for example, for a later have to be preserved in successive via. In particularly preferred embodiments of the epoxy resin formulation, these requirements for applicability and improved protection of the electrical and electronic components from moisture are made available.

As a further component, an additive component is preferably contained in the epoxy resin formulation according to the invention. This additive component comprises further additives and / or additives which, for example, improve the applicability of the epoxy resin formulation. Usable additives and additives are, for example, dyes, pigments, wetting auxiliaries, leveling agents, adhesion promoters, thixotropic agents, defoamers, flow modifiers, stabilizers, Flame retardants, dyes, wetting agents, sensitizers, degassing aids, or other fillers. In preferred embodiments, the additive component comprises fumed or disperse silica.

In particular, it is advantageous that the additive component pyrogenic silica allows adjustment of the viscosity or thixotropy of the formulation. An addition of fumed silica may provide a targeted adjustment of the viscosity of the formulation. In preferred embodiments, the epoxy resin formulation comprises> 0.4 wt% to <3 wt%, preferably> 1 wt% to <1.4 wt% fumed silica, based on the total weight of the epoxy resin formulation.

Also advantageously usable is acrylate copolymer. This can advantageously favor a smooth surface of the covering. Also advantageously usable is epoxy silane. This can advantageously provide an improved connection of the covering compound to the surfaces of the components and the substrate. These properties may contribute to a further improvement in the moisture barrier effect of the cured epoxy resin formulation. In preferred embodiments, the epoxy resin formulation comprises> 0.1 wt% to <0.5 wt%, preferably> 0.2 wt% to <0.4 wt%, based on the total weight of the Epoxy resin formulation, epoxy silane.

Another aspect of the present invention relates to the use of an epoxy resin formulation according to the invention for covering electrical and electronic components and assemblies.

In particular, the epoxy resin formulation according to the invention is for covering electrical and electronic components and assemblies in places with high humidity, such as Bathroom or rooms with long-term high relative humidity suitable.

In particular, moisture-sensitive components such as capacitors and processors can be effectively protected by a cover with the epoxy resin formulation according to the invention against ingress of moisture, for example by condensing water vapor. Thus, the Epoxidharzformu- lation is also in particular for the protection of electrical or electronic components and assemblies under humid conditions, for example in wet rooms or wet rooms according to the definition in point. 3.31 DIN 18 195 - 1; 2000-08 usable.

Examples and schematic figures which serve to illustrate the present invention are given below.

FIG. 1 shows a schematic representation of an electrical component 1, for example an integrated one

Circuit (IC), with a height of about 4 mm, which is applied to a printed circuit board 2 and is surrounded by inventive epoxy resin 3. The component 1 has connection pins, also called IC legs, with a pitch of 50 μm to 30 μm, behind which the formulation has flowed.

This illustration makes it clear that both the component was covered and the gap 4 with a depth of 100 μm to 300 μm was underfilled with the covering compound. It can be seen from this figure that both the component 1 and the solder contact 6 is completely covered, and the IC legs of the component were underflowed.

2 shows a schematic representation of an electrical component 1, for example, an integrated circuit (IC) with solder contacts 6, which on a Lei terplatte 2 is applied and is surrounded by a Vergleichabdeckmasse 7. This illustration makes it clear that the component 1 is not completely covered and the comparison covering compound 7 has not got under the component 1.

With the epoxy resin formulation according to the invention, the columns of the component could be filled and at the same time the component could be covered completely with the epoxy resin formulation, while a comparison cover composition did not cover the component on the surface and did not flow under the component.

Two exemplary embodiments of advantageous compositions of the epoxy resin formulations are given below.

example 1

Epoxy resin formulation comprising: (1) 87.7% by weight of aromatic epoxide ^{* 1} ;

(2) 2.0% by weight of aliphatic diol ^{* 2} ;

(3) 1.0% by weight of aliphatic triol ^{* 3} ,

(4) 1.9% by weight of UV initiator ^{* 4} ,

(5) 1.0% by weight of thermal initiator ^{* 5} ; (6) 0.2% by weight of epoxysilane ^{* 6} ,

(7) 0.2% by weight of acrylate copolymer * 7 ';

(8) 5.0% by weight of spherical fused silica ^{* 8} ;

(9) 1.0% by weight of fumed silica ^{* 9} .

* 1 Available, for example, from Bakelite under the trade name Bakelite EPR169.

* 2 Available for example from Celanese under the trade name TCD-OH. * 3 Available, for example, from Aldrich under the tradename EO-TMP (4,6 / 1).

* 4 Available for example from the company UCC under the trade name UVI 6974. * 5 Available for example from Siemens under the trade name PI 59.

* 6 Available for example from the company UCC under the trade name Silan A187. * 7 For example, available from the company Monsanto under the trade name Modaflow.

* 8 For example, available from Denka under the trade name FB-3S (X).

* 9 For example, available from Degussa under the trade name Aerosil R972.

To prepare the epoxy resin formulation, components (1) to (7) were weighed and mixed at room temperature with a magnetic stirrer and homogenized. The components (8) and (9) were weighed and stirred in with a Labordis solver, type LM-37 (Pendraulik), at about 3000 rpm for 15 minutes until the constituents were completely dispersed in. The mixture was then degassed for 15 minutes at 10-20 mbar. With this formulation boards were covered. The curing was carried out by UV irradiation in the UV-A range with an iron-doped mercury radiator (type F, Dr. Hönle), for 20 to 90 seconds. Subsequently, the sample was heated at 85 ^° C. for 60 minutes.

Example 2

Epoxy resin formulation containing:

(1) 76.5% by weight of cycloaliphatic epoxide ^{* 1} ;

(2) 4.8% by weight of aliphatic diol ^{* 2} ; (3) 2.7% by weight of aliphatic diol ^{* 3} ;

(4) 6.1% by weight of polyvinyl butyral ^{* 4} ;

(5) 1.8% by weight of UV initiator ^{* 5} ;

(6) 0.7% by weight of thermal initiator ^{* 6} ;

(7) 1.0% by weight of thermal initiator ^{* 7} ; (8) 0.2% by weight of epoxysilane ^{* 8} ;

(9) 0.2% by weight of acrylate copolymer ^{* 9} ;

(10) 5.0% by weight of spherical fused silica ^{* 10} ; (11) 1.0% by weight of fumed silica ^{* 11} .

* 1 For example, from the company Vantico under the trade name CY 177 available. * 2 Available for example from Celanese under the trade name TCD-OH.

* 3 For example, 1,2-propanediol available from Aldrich. * 4 For example, available from Clariant under the trade name B20H.

* 5 Available for example from the company UCC under the trade name UVI 6974.

* 6 Available for example from Aldrich under the trade name PI 55. * 7 For example, from the company Siemens under the trade name PI 59 available.

* 8 For example, available from the company UCC under the trade name Silan A187. * 9 For example, available from Monsanto under the trade name Modaflow.

For example, available from Denka under the trade name FB-3S (X).

* 11 Available for example from the company Degussa under the trade name Aerosil R972.

To prepare the epoxy resin formulation, components (1) to (9) were weighed and mixed at room temperature with a magnetic stirrer and homogenized. Ingredients (10) and (11) were weighed and stirred with a Labordis solver type LM-37 (Pendraulik) at about 3000 rpm for 15 minutes until the ingredients were completely dispersed. The mixture was then degassed for 15 minutes at 10-20 mbar. Boards were covered with this epoxy resin formulation. The curing was carried out by UV irradiation in the UV-A range with an iron-doped mercury radiator (type F, Dr. Hönle), for 20 to 90 seconds. Subsequently, the sample was heated at 85 ^° C. for 60 minutes. On printed circuit boards covered with the thus prepared and cured epoxy resin formulations, printed circuit boards of heat cost allocators were constructed and subjected to the following temperature change and climate change tests:

a) Temperature change test based on IEC 68-2-14 Na: There were 20 cycles of a temperature change between

Tl = O ⁰ C and T2 = 90 ⁰ C carried out, wherein the holding time was 30 minutes each and the transfer time between the tempered to the temperatures Tl and T2 chambers was less than or equal to 10 seconds.

It was found that the boards were resistant to these temperature changes and even for a short time had a thermal capacity up to 200 ⁰ C, which is required for example for wave soldering.

b) Test for climatic resistance based on IEC 68-2-30 Db variant 1:

There were four cycles of a change between state 1 corresponding to 25 ⁰ C / 88% RH (relative humidity) and condition 2 was carried out according to 70 ⁰ C / 83% RH. The holding time per state was 9 hours. The intervening time was three hours each.

It was found that the boards coated with the epoxy resin formulations did not show any moisture absorption during the period of use. Furthermore, these 90 minutes were resistant to a humidity of up to 100%. In addition, the resin formulation showed excellent adhesion to the no-clean printed circuit boards used.

Furthermore, with the epoxy resin formulations according to Example 1 and Example 2, films were produced from the cured epoxy resin formulation compositions having a layer thickness of 100 μm. In these, the water vapor permeability was at 24 C and 85% RH (relative humidity). This was 1.8 g / (m ² day) for the formulation according to Example 1 and 1.7 g / m ² day for the formulation according to Example 2. In a comparative experiment, the water vapor permeability of silicone films of a layer thickness of 80 microns, prepared from under the trade name 3-1753 Conformal Coating (Dow Corning) available silicone formulation was determined under the appropriate measurement conditions. The water vapor permeability of these silicone films was about 40 g / (m ² day).

These results show that the components covered with the epoxy resin formulations according to the exemplary embodiments were significantly better protected against penetrating moisture such as water vapor than electrical components which were protected by the commercially available silicone resins according to the comparative experiments. In addition, the formulations according to Examples 1 and 2 had a very good adhesion to the no-clean printed circuit boards used.

Claims

claims

A UV- and thermally curable epoxy resin formulation, characterized in that the epoxy resin formulation, based on the total weight of the epoxy resin formulation, comprises the following components: a. > 65 wt .-% to <95 wt .-% epoxy resin component; b. > 0.5 wt .-% to <10 wt .-% hydorxyl component; c. > 0, 1 wt .-% to <3 wt .-% photoinitiator component; d. > 0.5 wt .-% to <3 wt .-% thermal initiator component; e. > 2% by weight to <30% by weight of filler component; f. > 0, l wt .-% to <5 wt .-% additive component.

2. Epoxy resin formulation according to claim 1, characterized in that the epoxy resin component comprises aromatic and / or cycloaliphatic epoxy resins.

3. Epoxy resin formulation according to claim 1 or 2, characterized in that the hydroxyl component comprises polyols selected from the group comprising aliphatic diols, aliphatic triols and / or mixtures thereof.

4. Epoxy resin formulation according to one of the preceding claims, characterized in that the photoinitiator component comprises a triarylsulfonium hexafluoroantimonate and / or thiolani- hexafluoroantimonate.

5. Epoxy resin formulation according to one of the preceding claims, characterized in that the thermal initiator component comprises a Thiolaniumhexafluoroantimonat, preferably Benzylthiolaniumhexafluoroantimonat.

6. Epoxy resin formulation according to one of the preceding claims, characterized in that the thermal initiator component and the photoinitiator component comprise a Thiolaniumhexafluoroantimonat.

7. Epoxy resin formulation according to one of the preceding claims, characterized in that the filler component comprises fused silica and / or quartz flour.

8. Epoxy resin formulation according to one of the preceding claims, characterized in that the additive component comprises pyrogenic silica.

9. Use of the epoxy resin formulation according to one of the preceding claims for covering electrical and electronic components and assemblies.