EP1668698A1

EP1668698A1 - Plastically deformable cooling body for electric and/or electronic components

Info

Publication number: EP1668698A1
Application number: EP04766823A
Authority: EP
Inventors: Wolfgang Von Gentzkow; Dieter Heinl
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2003-09-29
Filing date: 2004-09-17
Publication date: 2006-06-14
Also published as: WO2005034236A1

Abstract

The invention relates to a cooling body for electric and/or electronic components, in particular printed circuit boards. The cooling body consists of a chemically uniform material, whose exterior is cross-linked and which is thus poorly or non-adhesive and whose interior can be plastically deformed and thus adapted to the contours of the components or printed circuit boards. The cooling body can be cured by thermal post-cross-linking.

Description

description

PLASTICLY DEFORMABLE HEAT SINK FOR ELECTRICAL AND / OR ELECTRONIC COMPONENTS

5 The invention relates to a heat sink for electrical and / or electronic components, in particular printed circuit boards, which is deformable.

Due to increasing miniaturization and integration of electronic components and assemblies, the power density in electrical and / or electronic components has been steadily increasing. This results in a higher power loss per component, which mainly arises in the form of thermal power and must be dissipated by cooling5 so that it does not lead to undesired heating of the electrical and / or electronic component or even to its thermal destruction.

There are several heat sinks known which are attached to the circuit board or individual components for cooling 0 printed circuit boards and which generally comprise aluminum as a light and very thermally conductive material. These elements are known internationally under the name "heat sinks for thermal management in electronics" .5 The problem with these heat sinks is that they are mainly mounted on the circuit board and the heat released in the components must be dissipated via the poorly heat-conductive circuit board. They are normally not suitable for mounting on the components, since they are stiff and cannot adapt to the respective arrangement of the individual parts (ie the "skyline") of the electrical and / or electronic components and therefore either for each individual part of an electrical and / or electronic component must be individually shaped and fixed and / or in some cases do not connect directly to the part of the electrical and / or electronic component to be cooled. In order to prevent these disadvantages, deformable heat sinks are now known from documents DE 197 04 549 AI and DE 196 24 475 AI. Although these heat sinks offer considerable advantages over the known rigid heat sinks, they also have a considerable disadvantage that they are constructed in several pieces, that is to say they have at least two materials, an outer material and a filling. This multiple structure of the materials on the one hand creates a barrier in the heat dissipation of the heat sink and on the other hand a higher manufacturing effort.

It is therefore an object of the invention to overcome these disadvantages and to provide a heat sink of the deformable type mentioned at the outset, which is essentially made of a material, adapted to the topography of the components mounted on the printed circuit board, then stabilized by hardening and - if necessary - can be removed without leaving any residue.

This object is achieved by the subject matter of main claim 1 and / or the subclaims.

The invention relates to a heat sink for electrical and / or electronic components, which is deformable, characterized in that it can be produced using only one material, the material being present in several modifications in the finished heat sink.

Such a heat sink is solid but plastically deformable. It consists of a UV-curable reaction resin that contains thermally conductive fillers. The surface of this heat sink is hardened or hardened by UV radiation. This creates a skin that, depending on the curing conditions, can be low-tack to non-tacky and enables problem-free handling of the heat sink. Such a heat sink is technically uniform, although it is grip-resistant on the outside and plastically and / or elastically deformable on the inside.

In this connection, for example, a heat sink with a stable outer skin can be produced, which is in the form of an attenuator and which, on the inside, comprises non-crosslinked heat-conducting material.

According to one embodiment, the heat sink in its partially cross-linked form is sticky on the surface and can therefore be applied to the component in a self-adhesive and deformable manner.

The invention is implemented by a reaction resin which is highly filled with thermally conductive fillers and which comprises a mixture of photoinitiators and thermally excitable cationic polymerization initiators. After shaping, this is crosslinked externally by radiation, so that it is stable on the outside but deformable on the inside. Although it is known from the literature that UV radiation penetrates through some fillers and can also harden through highly filled materials, it was found that the radiation only causes external crosslinking because it does not penetrate due to the high filler content of the reactive resin the inside of the body penetrates. The grip-resistant and deformable, possibly also self-adhesive, multi-layer structure (cross-linked, non-cross-linked, cross-linked) is therefore made of one material, but includes different states or modifications of this material.

Various resins are used as the reaction resin, for example epoxy resins and / or acrylate resins or mixtures of these resins can be used.

The resin system is advantageously based on cationically hardenable epoxy resin systems. UV and thermally hardenable one-component 200314931

Epoxy resin systems for use. In addition to the epoxy components, the epoxy resin systems can contain vinyl ethers and / or polyols, which in particular promote their thermal curing. The epoxy resin systems also contain thermally conductive fillers as well as initiators and catalysts for UV and thermally initiated cationic polymerisation and possibly common additives such as e.g. Dyes, pigments, stabilizers, thixotropic agents, flexibilizers, wetting agents, adhesion promoters and processing aids.

Linear aliphatic epoxides with cycloalkylene structure such as epoxidized olefins, diolefins and / or polyolefins, aromatic, aliphatic and cycloaliphatic di- or polyglycidyl ethers are suitable as epoxy compounds.

Examples of epoxy resins with cycloalkylene oxide structures are bis (2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, 1,2-bis (2,3-epoxycyclopentyl) ethane, vinylcyclohexene dioxide, 3,4- epoxycyclohexylmethyl-3 ^λ, ^λ 4 -epoxycyclo- hexan-carboxylate, 3, ^{4-epoxy-6-methylcyclohexylmethyl-3,} 4 '- epoxy-6-methyl-cyclohexane carboxylate, bis (3, 4-epoxycyclo- hexylmethyl) adipate, and Bis (3,4-epoxy-β-methylcyclohexylmethyl) adipate.

Examples of aromatic di- or polyglycidyl ethers used are bisphenol F diglycidyl ether and bisphenol A diglycidyl ether. Cycloaliphatic glycidyl compounds and β-methylglycidyl compounds are used as aliphatic di- or polyglycidyl ethers. These are glycidyl esters and β-methyl glycidyl esters of cycloaliphatic polycarboxylic acids such as tetrahydrophthalic acid, 4-methyl-tetrahydrophthalic acid, hexahydrophthalic acid, 3-methyl-hexahydrophthalic acid and 4-methylhexahydrophthalic acid. Other suitable cycloaliphatic epoxy resins are the diglycidyl ether and β-methyl-glycidyl ether of cycloaliphatic alcohols, such as 1,2-diglycidyl ether of 1,3-dihydroxycyclo-hexane and 1,4-dihydroxycyclohexane, 1,4-cyclohexanedimethanol, 1,1- Bis (hydroxy-methyl) cyclohex-3-ene, bis (4-hydroxycyclo-hexyl) methane, 2,2-bis (4-hydroxycyclohexyl) propane and bis (4-hydroxy-cyclohexyl) sulfone.

Preferred cycloaliphatic epoxy resins are bis (4-hydroxycyclohexyl) methane diglycidyl ether, 2, 2-bis (4-hydroxycyclohexyl) propane diglycidyl ether, tetrahydrophthalic acid diglycidyl ester, 4-methyltetrahydrophthalic acid diglycidyl ester, 4-methyl-hexoxy-methylahydylcidyl ester, 4-methyl-hexoxy-methyl-hexahydyl-3-methyl-hexahydroxyl 3 ^Λ- epoxycyclohexane carboxylate and especially hexahydrophthalic acid diglycidyl ester.

The cycloaliphatic epoxy resins can also be used in combination with aliphatic epoxy resins. Epoxidation products of unsaturated fatty acid esters can be used as "aliphatic epoxy resins". Preference is given to using epoxy-containing compounds which are derived from mono- and polyfatty acids having 12 to 22 carbon atoms and an iodine number between 30 and 400, such as, for example, oleic acid, gadolinic acid, erucic acid, ricinoleic acid, linoleic acid, linolenic acid, elaidic acid , Liqueur acid, arachidonic acid and clupanodonic acid. For example, the epoxidation products of soybean oil, linseed oil, poppy seed oil, hemp oil, cottonseed oil, sunflower oil, rapeseed oil, polyunsaturated triglycerides, triglycerides from Euphorbia waxes, peanut oil, olive oil, olive kernel oil, almond oil, kapokol, hazelnut oil, apricot oil, book oil eckernol, lupinenol, corn oil, sesamol, grape seed oil, castor oil, herring oil, sardine oil, menhadenol oil, walol oil, tallol oil and derivatives derived therefrom.

Highly unsaturated derivatives which are obtained by subsequent dehydrogenation reactions of these oils are also suitable.

In principle, all vinyl ether-functionalized hydroxyl compounds are suitable as vinyl ether-functional compounds. Suitable compounds are in particular cyclohexanedi- methyldivinyl ether, triethylene glycol dininyl ether, butanediol divinyl ether, bis (4-vinyloxybutyl) isophthalate, bis (4-vinyloxybutyl) succinate, bis (4-vinyloxymethylcyclohexylmethyl) glutarate, and hydroxybutylmonovinyl ether or vinyl ether-functionalized hydroxypurylated aliphatic polyether. Vinyl ethers with> 2 vinyl ether groups per molecule are preferred.

Compounds which are obtained by reaction of epoxy compounds with alcohols or phenols are preferably used as the polyol component. Furthermore, polyvalent aliphatic or cycloaliphatic alcohols such as e.g. Glycols, trifunctional or tetrafunctional alcohols such as e.g. Trimethylolpropane or ethers of glycols with phenols or bisphenols as well as polymer polyols are used.

A mixture of UV-reactive and thermally reactive components, as described in EP 504 569, is preferably used to initiate the cationic curing. A cationic photoinitiator or a cationic photoinitiator system is used to initiate cationic curing. Its share in the total epoxy resin system can be 0.1 to 5%, advantageously 1 to 3%. When UV irradiated, these photoinitiators release reactive cations, eg protons, which initiate the cationic curing process of the epoxy resin. The photoinitiators are derived from stable organic onium salts, in particular with nitrogen, phosphorus, oxygen, sulfur, selenium or iodine as the central atom of the cation. Aromatic sulfonium and iodonium salts with complex anions have proven to be particularly advantageous. A photoinitiator releasing a Lewis acid is also possible. Phenacylsulfonium salts, hydroxylphenylsulfonium salts and sulfonium salts are also to be mentioned. Onium salts can also be used, which are not stimulated directly but via a sensitizer to form acids. Organic silicon compounds that are exposed to UV radiation in the presence of organoaluminum compounds bonds release a silanol can be used.

Thiolanium salts such as those described in DE 197 50 147 are used as latent thermal initiators for cationic polymerisation. Unsubstituted benzylthiolanium salts are preferably used, in particular benzylthiolanium hexafluoroantimonate.

So-called dual-cure catalysts can also be used. These initiate the curing of epoxy resins both when irradiated with UV light and thermally. When irradiated at room temperature, no hardening takes place in shaded areas. However, curing can take place in a subsequent process by increasing the temperature. The curing temperatures are generally between 80 and 150 ° C.

In principle, all conventional UV sources, such as xenon, tungsten, mercury and metal halide emitters, can be used for UV radiation. The use of UV lasers is also possible.

Metal oxides such as silicon oxide, aluminum oxide, boron nitride, tungsten oxide, titanium oxide, metal nitrides such as aluminum nitride or metals are suitable as heat-conductive fillers. The fillers can be in the form of multimodal mixtures of finely divided powders of spherical, splintery, flaky and / or needle-shaped powder particles. The heat-conductive fillers come in concentrations of 40 to 80 vol.%, Advantageously in concentrations of 60 to 70 vol. - % for use.

The following example is intended to explain the invention. For example:

An epoxy resin filled with thermally conductive material and photoinitiator is rolled on a roller mill between 2 waxed carrier foils to form an approx. 3 mm thick layer. Mats or pillows adapted to the area to be cooled are largely cut or punched out of this layer and surface-crosslinked at room temperature by UV radiation. This creates a grip-resistant, not or only "self-adhesive" sticky multi-layer structure. Since there is no crosslinking due to the high proportion of filler inside the mat, the mat is plastically and / or elastically deformable thanks to the material that is still not crosslinked on the inside, but is uniform in terms of material technology.

The material can be adjusted so that when the mat is used for heat removal, it is slowly cross-linked and / or that additional heating of the mat through thermal cross-linking results in a stable, contour-conforming shape after the cooling body has been applied. This is an advantage with regard to maintenance and repair work because the cross-linked heat sink then stabilizes the topography of the components and if necessary, e.g. can be removed without residue for repair purposes.

The decisive advantage of the heat sink according to the invention over the classic known "heat sinks" is that the attachment is not tied to an electrical and / or electronic component. Rather, complete flat assemblies can be applied by applying the

Dewarm the heat sink, i.e. cool it, leaving the designer of the lay-out of the electrical and / or electronic component more design freedom. The use of only one material additionally improves the overall thermal conductivity, since the crosslinked outer layer or outer skin of the heat sink is a good thermal conductive material and there are no additional thermal resistances at the interfaces between the sleeve and the heat medium.

Furthermore, the possibility of transferring the material into a solid and stable molded body offers additional advantages.

Finally, by avoiding different material components, logistically and procedurally, a much more cost-effective production is possible than is offered according to the prior art.

The invention relates to a heat sink for electrical and / or electronic components and printed circuit boards, characterized in that it is produced using a chemically uniform material which is highly filled with thermally conductive fillers and is based on UV and thermally curable reactive resins UV curing maintains a low-tack to tack-free surface and is therefore easy and easy to handle, the inside consists of uncrosslinked, thermally curable material and is therefore flexible and deformable, and can be adapted to different topographies and - can also be thermally hardened on the inside if heat is applied.

The invention discloses a heat sink for electrical and / or electronic components, in particular flat assemblies. The heat sink consists of a chemically uniform material that is cross-linked on the outside and is therefore low-tack or tack-free and plastically deformable on the inside and can therefore be adapted to the contour of the structural elements or printed circuit boards to be cooled. The heat sink can be hardened through thermal post-crosslinking.

Claims

1. Heat sink for electrical and / or electronic components, which is deformable, characterized in that it can be produced using only one material, the material being present in several modifications in the finished heat sink.

2. Heat sink according to claim 1, characterized in that it is produced using a chemically uniform material which is highly filled with thermally conductive fillers and is based on UV and thermally hardenable reactive resins.

3. Heat sink according to one of claims 1 or 2, characterized in that it receives a surface that is low-tack to non-tacky by UV curing.

4. Heat sink according to one of the preceding claims, d characterized in that it consists of uncrosslinked, thermally hardenable material and is therefore flexible and deformable and can be adapted to different topographies.

5. Heat sink according to one of the preceding claims, characterized in that it can also be thermally hardened inside when heat is supplied.

6. Heat sink according to one of the preceding claims, characterized in that the reaction resin used consists of an epoxy resin or a mixture of different epoxy resins.

7. Heat sink according to one of the preceding claims, characterized in that the epoxy resin polyols and / or vinyl ether.

8. Heat sink according to one of the preceding claims, characterized in that the reaction resin used comprises acrylate groups and / or methacrylate groups.

9. Heat sink according to one of the preceding claims, characterized in that the reaction resin used comprises both photoinitiators and thermal initiators.

10. Cow body according to one of the preceding claims, characterized in that the photoinitiators used also act as thermal initiators at the same time.

11. Heat sink according to one of the preceding claims, characterized in that the reaction resin comprises heat-conductive spherical, splintered, leaf-shaped and / or needle-shaped fillers or filler mixtures based on metals and / or metal oxides and / or metal nitrides.

12. Use of a heat sink according to one of claims 1 to 11 in an electrical and / or electronic component and / or in a printed circuit board.