T 0598/16 () of 25.6.2019

European Case Law Identifier: ECLI:EP:BA:2019:T059816.20190625
Date of decision: 25 June 2019
Case number: T 0598/16
Application number: 10180160.3
IPC class: H01L 23/373
Language of proceedings: EN
Distribution: D
Download and more information:
Decision text in EN (PDF, 358.565K)
Documentation of the appeal procedure can be found in the Register
Bibliographic information is available in: EN
Versions: Unpublished
Title of application: Thermal management system
Applicant name: NeoGraf Solutions, LLC
Opponent name: SGL Carbon SE
Board: 3.4.03
Headnote: -
Relevant legal provisions:
European Patent Convention 1973 Art 54
European Patent Convention 1973 Art 56
European Patent Convention 1973 Art 76(1)
European Patent Convention 1973 Art 100(a)
European Patent Convention Art 123(2)
Keywords: Amendments - added subject-matter (no)
Inventive step - (yes)
Late-filed ground of opposition - admitted (no)
Catchwords:

-

Cited decisions:
G 0010/91
G 0007/95
Citing decisions:
-

Summary of Facts and Submissions

I. The appeal of the opponent concerns the interlocutory decision of the opposition division maintaining the European patent EP-B-2 296 454 as amended during the opposition proceedings (Article 101(3)(a) EPC).

II. The opposition had been filed against the patent as a whole. Grounds of opposition were added subject-matter, insufficiency of the disclosure and lack of inventive step.

III. Reference is made to the following documents:

E1: US 5,991,155 A,

E2: US 3,404,061 A,

E3: JP 6-134917 A,

E4: JP 8-23183 A,

E4a: EP 691 803 A (parallel application of E4).

IV. At the oral proceedings before the board the appellant (opponent) requested that the decision under appeal be set aside and that the contested patent be revoked.

The respondent (patent proprietor) requested that the appeal be dismissed and the patent thus be maintained as upheld by the opposition division.

V. The wording of claims 1, 4, 9, and 10 is as follows (board's labelling "(a)", "(b)", "(c)", "(d)", and "(e)"):

"1. A thermal management system (10) comprising a heat source having an external surface (100a) and a thermal interface (20) comprising

(a) an anisotropic flexible graphite sheet formed of compressed particles of exfoliated natural graphite and

(b) having a planar area greater than the area of the external surface of the heat source,

the flexible graphite sheet

(c) having first and second major planar surfaces and

(d) having axes of higher thermal conductivity parallel to said major planar surfaces,

characterized by

(e) a first one of said major planar surfaces being in direct operative contact with the heat source."

"4. A thermal management system (10) according to any one of claims 1 to 3 wherein the ratio of thermal conductivity of the anisotropic graphite sheet parallel to one to the major surfaces as compared to transverse to the major surface is at least about 20."

"9. A thermal management system (10) according to any one of claims 1 to 7 further comprising a heat sink (30) which comprises a graphite article shaped so as to provide a heat collection surface and at least one heat dissipation surface, the heat collection surface of the heat sink being in operative contact with a second one of the said major planar surfaces of the flexible graphite sheet."

"10. A thermal management system (10) according to claim 9 wherein the graphite article comprises anisotropic flexible sheets of compressed particles of exfoliated graphite laminated into a unitary article."

VI. The parties argued essentially as follows:

(i) Amendments

The appellant argued that the subject-matter of claims 1, 4, 9, and 10 extended beyond the application and the parent application as filed.

The respondent was of the opinion that the subject-matter of these claims had a basis in the application as filed as well as the parent application as filed.

(ii) Novelty

The appellant requested to be allowed to discuss lack of novelty of the claimed subject-matter.

The respondent objected to this request.

(iii) Inventive step

According to the appellant the claimed subject-matter lacked inventive step over document E1 as the closest state of the art, especially in view of document E2.

The respondent argued that the claimed subject-matter involved an inventive step over document E1, having regard to documents E2 and E3.

Reasons for the Decision

1. Amendments

1.1 In the contested decision the opposition division held that the subject-matter of claims 1, 2, 4, and 7-10 did not extend beyond the application as filed or the par­ent application as filed (see point 11).

1.2 The appellant argued that the following features had not been disclosed in the original application and par­ent application:

- claim 1, feature (d): the graphite sheet had "axes of higher thermal conductivity parallel to said major planar surfaces"; it had only been disclosed that the thermal conductivity par­allel to the upper and lower surfaces of the graphite sheet was sig­nif­icantly greater than in the direction transverse to these surfaces;

- claim 1, feature (e): a major planar surface of the graphite sheet was "in direct operative contact" with the heat source; it had been disclosed that an adhesive could be used to attach the sheet to the heat source; moreover, the claimed expression was open to new undisclosed possibilities;

- claim 4: the ratio of thermal conduc­tiv­i­ties was at least "about" 20; there was no basis for this vague term;

- claim 9: a heat sink comprising "a graphite arti­cle" and having a heat collection surface "in oper­ative contact with a second one of the said major planar surfaces of the flexible graphite sheet"; on page 18, lines 21-28 of the description merely a heat source, a heat collection surface and a heat sink was described;

- claim 10: the graphite article comprising "an­isotropic flexible sheets of compressed parti­cles of exfoliated graphite laminated into a unitary article"; this was not disclosed in the descrip­tion.

1.3 The board notes that it emerges from the de­scrip­tion of the application as filed (see for example the respec­tive paragraphs bridging pages 4 and 5 and pages 8 and 9 and page 6, paragraph 2), which is iden­ti­cal to the description of the parent application, that the flex­ible graphite sheet of the claimed thermal management system possesses an an­isotropic structure due to the compressed particles of exfoliated natural graphite forming the graphite sheet. The graphite particles are aligned with the opposed major surfaces of the graphite sheet. This anisotropic structure implies that many physical properties of the graphite sheet, e. g. the thermal conductivity, are directional, in particular that they have different values parallel and perpen­dicular to the major surfaces of the graphite sheet.

The board agrees with the appellant in that the graphite sheet is described as having preferably a high degree of anisotropy implying a highly directional ther­­­­mal conductivity, which may for example be 20 times greater in the direction parallel to the major surfaces of the graphite sheet than in a direction perpendicular to them (see the description of the (parent) applica­tion, page 3, third to last para­graph; paragraph bridg­ing pages 4 and 5; page 6, penul­ti­mate paragraph). How­ever, throughout the description of the (parent) appli­cation (see page 4, paragraph 2; page 8, last para­graph; page 11, second paragraph) and in the original independent claims of the application as filed (claim 1) and of the parent applica­tion as filed (claims 1 and 15), the graphite sheet is specified in general terms as being merely "anisotropic" without any indication concerning the degree of anisotropy. In relation to the physical properties this implies a general disclosure of the thermal con­ductivity having a higher value par­al­lel to the major surfaces of the graphite sheet than perpendicular to them.

Feature (d) of claim 1 is therefore considered to be directly and unambiguously derivable from the applica­tion as filed as well as from the parent application as filed.

1.4 As pointed out in the contested decision (see point 11.1.3) it has been disclosed in orig­inal claim 1 of the application as filed that one of the major planar surfaces of the graphite sheet was "in operative contact" with the heat source. A similar disclosure is also contained in original claims 1 and 15 of the parent application.

Hence, it only remains to be considered whether the indi­ca­tion in feature (e) that the surface of the graphite sheet is in "direct" operative contact with the heat source has a basis in the application and the parent application as filed.

In relation to the connection of the heat sink 30, which constitutes a specific embodiment of the inven­tion, and the electronic component 100 the follow­ing is stated in the description of the (parent) application as filed (see page 18, last paragraph):

"Heat sink 30 can be mounted to electronic compo­nent 100 by conventional means, such as by mounting directly to electronic component 100 using an ad­he­sive, such as a pressure sensitive or thermally ac­ti­vated adhesive (something which the relatively low weight of graphite permits); mounting to ther­mal interface 20, if present, such as by an adhe­sive; or mounting to the board or other object on which electronic circuit 100 is mounted, provided heat collection surface 30a of heat sink 30 is operatively connected to external surface 100a of electronic component 100 (directly or through thermal interface 20)."

The heat sink 30 is thus considered "directly" mounted on the electronic component 100 when it is mounted by means of an adhesive to the electronic component 100. This is presented as an alternative to the heat sink 30 being operatively connected to the electric component 100 through the thermal interface 20. In a similar fash­­ion the surface of the graphite sheet is understood to be in "direct" operative contact with the heat source (as indicated in feature (e) of claim 1) if it is mounted, e. g. by means of an adhesive, to the heat source with­out any intervening layer.

As pointed out by the re­spon­dent, it is described in the description of the (par­ent) application that the surface of the ther­mal interface 20 (constituted by the graphite sheet) "sits against" the external surface of the electronic com­ponent 100, i. e. the heat source, and that the in­ter­face 20 is "adhered or mounted to" the external sur­face of the component 100, e. g. by means of a ther­mally activated adhesive (see page 11, last full sen­tence; page 12, paragraph 2). It is therefore con­sid­ered to be directly and unambiguously derivable from the (par­ent) application as filed that the surface of the graphite sheet is - within the above meaning - in "direct" operative contact with the heat source.

Hence, feature (e) of claim 1 does not contain subject-matter ex­tending beyond the content of the application or the parent application as filed.

1.5 Concerning the additional feature of dependent claim 4 that the ratio of thermal conduc­tiv­i­ties is at least "about" 20 the board notes that an identical wording is used in original claim 6 of the application as filed. There is thus no doubt that this additional feature has a proper basis in the original application documents.

Moreover, in the description of the parent application it is disclosed that the claimed ratio "can approach 20 to one or higher" (see page 6, paragraph 3) implying that the stated value of 20 is merely approximate. This is considered an appropriate basis for the term "about" in claim 4.

Hence, the additional feature of claim 4 is considered to be directly and unambiguously derivable from the applica­tion and the parent appli­cation as filed.

1.6 The additional features of dependent claim 9 are based on claim 12 of the application as filed and on claim 15 (in particular feature (c)) of the parent appli­cation as filed. Moreover, the additional features of depen­dent claim 10 are based on claim 12 of the application as filed and on claim 19 of the parent appli­cation as filed. Essen­tial­ly the same wording is used in present claims 9 and 10 as in the corresponding originally filed claims of the application / parent application mentioned above.

Hence, claims 9 and 10 do not contain subject-matter ex­tending beyond the con­tent of the ap­pli­ca­tion or the parent application as filed.

1.7 Consequently, the board is satisfied that the amend­ments effected in relation to claims 1, 4, 9, and 10 comply with the requirements of Article 76(1) EPC 1973 and Article 123(2) EPC.

2. Novelty

2.1 During the oral proceedings before the board the ap­pellant requested for the first time during the appeal proceedings to be allowed to discuss lack of novelty of the claimed subject-matter with respect to the example illustrated in Figure 11 of document E1.

2.2 The ground of opposition under Article 100(a) EPC 1973 in combination with Article 54 EPC 1973 (lack of nov­elty) was raised by the opponent - present appellant - for the first time after the expiry of the time limit laid down in Article 99(1) EPC (namely with letter dated 30 October 2015), thus constituting a late-filed ground of opposition.

However, this objec­tion was dropped during the oral pro­ceedings before the opposition division (see point 4 of the minutes of these proceedings and point 13.1 of the con­tested decision). Consequently, the opposition di­vi­sion did not discuss with the parties the admission into the pro­ceedings of this ground of opposition and did not exercise its dis­cretionary power under Article 114(1) and (2) EPC 1973 (decision G 10/91 of the En­larged Board of Appeal, point 16 of the Reasons) to decide whether or not to admit this ground of opposi­tion into the pro­ceed­ings for being prima facie rele­vant. The fact that novelty over document E1 is dis­cussed in the con­tested de­cision "for complete­ness" (see point 13.2) is not considered relevant in this respect, as this is merely part of the assessment of inventive step.

2.3 Since the ground of opposition under Article 100(a) EPC 1973 in combination with Article 54 EPC 1973 (lack of nov­elty) was neither raised and substantiated in the notice of opposition nor introduced into the pro­ceed­ings by the opposition division in application of Article 114(1) EPC 1973, this ground of opposition is a fresh ground within the meaning of the term intended in the decision G 10/91 (see decision G 7/95, point 5.3 of the Reasons).

The Enlarged Board held in the decision G 10/91 men­tioned above that a fresh ground of opposition may in principle not be introduced at the appeal stage and that an exception to this principle is justified only in case the patentee agrees that the fresh ground may be considered: volenti non fit injuria (see point 18 of the Reasons).

In the present case the respondent explicitly objected to the introduction of the new ground of opposition into the appeal proceedings. Moreover, the exception provided for in the decision G 7/95 (see headnote, last sentence) does not apply, since the objection of lack of novelty was not based on the closest prior art, which is considered to be the embodiment of Figure 1(a) of document E1 (see point 3 below). Therefore, the board has no power to introduce this ground of opposition into the proceedings for the first time at the appeal stage.

In view of the above, the ground of opposition under Article 100(a) EPC 1973 in combination with Article 54 EPC 1973 (lack of nov­elty) is not admitted into the appeal proceedings.

3. Inventive step

3.1 Closest state of the art

In the decision under appeal the opposition division considered document E1 the closest state of the art (see point 14.1). Both parties also argued inventive step taking this document as the star­ting point.

Indeed, document E1 discloses - as detailed below - sub­ject-matter that is conceived for the same purpose as the claimed inven­tion, namely for providing a ther­mal management system, and has the most relevant tech­nical features in common with it. This document is there­fore regarded as the closest state of the art, in particular the embodiment of Figure 1(a).

3.2 Distinguishing features

3.2.1 Document E1 discloses (see column 1, lines 6-9; column 2, lines 16-23) a heat sink for cooling an exothermic device, such as a microprocessor, utilizing a heat spreader sheet, which is made of a flexible material having high thermal con­ductivity, such as graphite or graphite composite.

With respect to a reference example shown in Figure 11 document E1 discloses (see column 1, line 29 - column 2, line 13) a heat spread­er sheet 4 fixed to an in­side wall surface of cas­ing 3 of a portable elec­tron­ic appa­ratus and an exo­thermic device 1, such as a micro­pro­ces­sor, mounted on a circuit board 2.

The first em­bod­i­ment shown in Figure 1(a) comprises (see column 5, lines 16-37) furthermore an abutting member 6 on the inside wall sur­face of casing 3 whereby the heat spreader sheet 4 is made to con­tact a surface of exothermic device 1. By this structure ­trans­mis­sion of heat from exo­ther­mic device 1 to heat spread­er sheet 4 is efficient be­cause the surface of exothermic device 1 contacts the surface of heat spread­er sheet 4.

3.2.2 There is consensus between the parties that document E1 discloses - using the wording of claim 1 - in relation to the first embodiment shown in Figure 1(a) a thermal management system comprising a heat source (exothermic device 1) having an external surface and a thermal in­ter­face (heat spreader sheet 4) comprising a­­ flexible graphite sheet (heat spreader sheet 4 is made of a flex­­ible material, ­e. g. graphite or graphite compos­ite) having first and second major planar surfaces (front and back sides of heat spreader sheet 4), a first one of the major planar surfaces of the flexible graphite sheet being in direct operative con­tact with the heat source (heat spreader sheet 4 is made to contact a surface of exothermic device 1 by means of abutting member 6). The board agrees with this assess­ment.

3.2.3 The respondent argued that document E1 did not disclose feature (b) of claim 1 that the planar area of the ther­­­mal interface was greater than the area of the ex­ternal surface of the heat source.

However, only the part of the heat spread­er sheet 4 that covers the abutting member 6 is in a position to contact the exo­thermic device 1, but not the part which is fixed to the inside wall surface of the casing 3. Hence, the pla­nar area of the heat spreader sheet 4 is necessarily greater than the area of the external surface of the exothermic device 1. This can also be seen in Figure 1(a) of document E1. Feature (b) is therefore disclosed in this document.

3.2.4 The subject-matter of claim 1 thus differs from the thermal management system of the embodiment of Figure 1(a) in that the flexible graphite sheet

- is anisotropic and formed of compressed particles of exfoliated natural graphite (feature (a)), and

- has axes of higher thermal conductivity parallel to said major planar surfaces (feature (d)).

3.3 Objective technical problem

The appellant argued that it was the objective techni­cal problem of the in­vention to merely provide an al­ter­native thermal man­age­­ment system.

However, the board agrees with the respondent in that the aniso­tropy of the thermal interface has the tech­nical effect of reducing the height of peaks in the tem­perature dis­tribution across the thermal interface, thereby improv­ing the efficiency of the thermal manage­ment system.

It is therefore considered to be the objective tech­nical problem of the invention to achieve this effect.

3.4 Obviousness

3.4.1 The appellant argued that document E2, which disclosed compressed particles of exfoliated natural graphite, would lead the skilled person to the claimed subject-matter.

3.4.2 Document E2 discloses (see column 1, lines 11-28) a new form of graphite, in particular a flexible sheet material which consists essentially of graphite and is free of any binding or bonding material. The flexible graphite sheet material possesses anisotropic or highly directional properties. The flexible graphite sheet material is formed from graphite particles which have been first appreciably expanded or intumesced and then compressed or compacted together.

However, there is no mention in document E2 that the flexible graphite sheet had the advantage of reducing the height of peaks in the tem­perature dis­tribution across the sheet. Moreover, only in the context of using the flexible graphite sheet of E2 as a heat barrier - i. e. the opposite use compared to that of the invention - the anisotropy of the thermal conduc­tiv­ity of the graphite sheet is mentioned in document E2 (see column 14, lines 70-73):

"In view of the very low thermal conductivity in the c direction of each of the graphite layers, and the use of a highly reflective metal coating, the layers 114 serve as very effective radiant heat barriers."

The skilled person would therefore not consider using the flexible graphite sheet of document E2 in order to solve the posed problem.

3.4.3 In relation to the flexible graphite sheet document E1 contains references to documents E3 and E4. However, these documents do not disclose flexible graphite sheets formed of compressed particles of exfoliated nat­ural graphite. Hence, in the board's view, these documents would not lead the skilled person to the claimed subject-matter, either.

3.4.4 In view of the above the subject-matter of claim 1 involves an inventive step.

Claims 2 to 10 are dependent on claims 1. Accordingly, the subject-matter of claims 1 to 10 involves an in­ven­tive step (Article 52(1) EPC and Article 56 EPC 1973).

4. Conclusion

Since the board is - as indicated above - of the opin­ion that the patent as upheld by the opposition divi­sion and the invention to which it relates meet the requirements of the EPC, the opponent's appeal is to be dismissed (Article 101(3)(a) EPC and Article 111(1) EPC 1973).

Order

For these reasons it is decided that:

The appeal is dismissed.

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