T 1009/12 – No Effect At All

This is an examination appeal.

Claim 1 of the auxiliary request read:

1. A process for plating silver onto a surface, wherein the silver is immersion plated from a composition comprises:

a) a soluble source of silver ions;

b) an acid;

c) an imidazole of the following formula:

wherein R1, R2, R3 and R4 are independently selected from the group consisting of substituted or unsubstituted alkyl groups, substituted or unsubstituted aryl groups, halogen, nitro groups and hydrogen; and

d) an oxidant selected from nitro aromatic compounds.

In what follows the Board discusses whether this claim involves an inventive step:

[2.1] The Board comes to the conclusion that process claim 1 of the […] auxiliary request lacks inventive step over the teaching of the uncontested closest prior art D1 for the reasons that follow.

[2.2] The English abstract of the Japanese application D1 discloses a process for forming a silver plating on the surface of copper or copper alloy by contacting the surface with an aqueous immersion plating solution. This solution according to D1 has a pH of 3.0 to 4.5 and contains 0.01 to 1.0 %, more preferably 0.05 to 0.5 % silver nitrate (this percentage “%” is interpreted as meaning “wt.%” so that these ranges correspond to 0.1-10 g/l and preferably 0.5-5.0 g/l silver nitrate; thus corresponding to 0.06-6.3 g/l or preferably 0.32-3.2 g/l Ag**(+)-ions), 2-alkylimidazole (see below) as an alkyl imidazole compound in combination with an organic acid, e.g. acetic acid (preferably in the form of the salt). The treating liquid is usually kept at 20-60°C and is brought into contact with the copper or copper alloy for 30 seconds to 5 minutes to form the silver film (see English abstract of D1).

[2.2.1] The aqueous immersion plating silver solution of D1 is thus a simple aqueous composition containing silver nitrate, an organic acid (or salt thereof) and e.g. a 2-alkylimidazole.

Taking account of the structural formula of the imidazole given in D1, which comprises the two substituents R**(2) and R**(4), and the imidazole description in the English abstract it is clear that the imidazole can be substituted by alkyl groups in the imidazole positions 2 and 4, i.e. R**(4) or R**(2) can be hydrogen:

[2.2.2] The composition described in the English abstract of D1 does not contain any surfactant or chelating agent.

[2.3] The process for plating silver onto a surface according to claim 1 of the first auxiliary request - wherein the silver is immersion plated from a composition which comprises a soluble source of silver ions, an acid, an imidazole of the given formula with either R1, R2 and R4 being selected from hydrogen and R3 being selected from substituted or unsubstituted alkyl groups, or R1, R3 and R4 being selected from hydrogen and R2 being selected from substituted or unsubstituted alkyl groups, or with R1 and R4 being selected from hydrogen and R2 and R3 being selected from substituted or unsubstituted alkyl groups (see points VII and 2.2.1 above) - is thus distinguished from the process according to D1 only by an oxidant being selected from nitro aromatic compounds.

[2.3.1] The divisional application as originally filed is silent with respect to any effect of this distinguishing feature […], and in the parent application it is presented only as an optional feature of the composition […], also without any effect.

[2.3.2] According to the examples I to III of the divisional application the silver plating solution consisted of the four components silver nitrate (1 g/l), methane sulfonic acid (20 ml (70%)/l), 3,5-dinitrohydroxy benzoic acid (1 g/l), l-histidine (1 g/l) and water and copper was plated with it at 100°F (= 37.8°C) for 5 minutes (see examples I-III).

This imidazole compound “L-histidine” (IUPAC name) used in the examples I-III can also be designated “2-Amino-3-(1H-imidazol-4-yl) propanoic acid”, and thus represents an imidazole of the claimed specific formula wherein R1, R2 and R4 are hydrogen and R3 is a substituted alkyl group, i.e. -CH2-CH(NH2)-COOH.

[2.3.3] On the other hand, process claim 1 defines a process for plating silver onto a surface which uses a composition which “comprises” the four specified components in unspecified amounts.

According to this open definition the presence of a very small amount of e.g. 5 ppm of said oxidant is sufficient to meet the condition of claim 1 of the first auxiliary request. However, the Board considers that such a low concentration will not cause any effect in view of the common general knowledge of a chemist and the intended purpose of an oxidant. Particularly in the light of the most general range of the oxidant of from 0.1-25 g/l (corresponding to 100-25000 ppm) disclosed in the present application […] it is not reasonable to expect any effect of the nitro aromatic compound in such a low concentration.

Therefore claim 1, which does not specify any concentration ranges of the four components at all, is considered to cover embodiments where the mere presence of the nitro aromatic oxidant compound will not produce any effect at all.

The appellant’s arguments to the contrary cannot hold for the following reasons.

[2.4] First of all, the appellant argued that the skilled person would comprehend the claims as encompassing only effective amounts of the specified components to achieve the technical effects including immersion silver plating as disclosed in the application; he would construe the claims by “building up” and not by “tearing down”, to arrive at an interpretation of the claims which is technically sensible and takes account of A 69 (T 190/99 [2.4]).

However, taking account of A 69 cannot be accepted since that decision relates to an opposition case where an interpretation of the claim which is technically sensible takes into account the whole disclosure of the patent (A 69) and therefore does not apply to the present examination case. In such a case, like the present one, the claims have to make sense as they stand. Since none of the independent claims of both requests defines “an effective amount of the oxidant” it is evident that the scope of these claims is not restricted to effective amounts but, to the contrary, encompasses ineffective amounts of said nitro aromatic oxidant.

In this context it is further considered that the immersion silver plating composition per se used according to process claim 1 – as described on page 6, second and third paragraphs of the parent application as originally filed (the oxidant was an optional component of the immersion silver plating composition of the parent application; see point [2.3.1] above) – even without the nitro aromatic oxidant provides brighter, smoother and more cohesive silver deposits than baths not containing imidazoles. The same conclusion would be valid for a bath according to process claim 1 which comprises an ineffective amount of e.g. 5 ppm of the nitro aromatic oxidant. Therefore also the appellant’s argument that an effective amount of the oxidant is necessary to obtain a bright silver deposit cannot hold.

[2.5] The appellant’s arguments that the experiments of D2 would represent acceptable comparative examples with respect to D1 and would prove an effect of the nitro aromatic oxidant – i.e. to decrease the plating rate and to brighten and improve the silver deposit – cannot hold either.

[2.5.1] Regarding the declaration D2 of Ms Toscano, the Board considers unusual that it is neither dated nor that it states that the described experiments have been made in agreement with the present application and/or in agreement with the closest state of the art D1. In substance, D2 discloses the examples A, B and C.

Example B repeats example A with the difference that no imidazole was present in the plating composition. Example C repeats example A with the difference that no dinitrosalicylic acid (i.e. the nitro aromatic oxidant) was present (see D2, paragraph 3).

The immersion silver plating bath of example A does not specify the silver ion concentration nor that it is aqueous. It comprises besides 10 g/l imidazole (since not further specified it has to be interpreted that all substituents R1, R2, R3 and R4 are hydrogen), 11.3 g/l of hydroxyethylenediaminetetraacetic acid (HEDTA), 5 g/l Chemeen T-15, 5 g/l Igepal Co-730, 0.75 g/l of 3,5-dinitrosalicylic acid (which is the trivial name for the compound “3,5-dinitrohydroxy benzoic acid” disclosed in the present application as the preferred oxidant) and said bath has a pH of 2 adjusted with nitric acid. The copper parts are plated in the bath for 6 minutes at 35°C (see D2, page 1, point 3A).

D2 does not contain any explanation of Ms Toscano why said chelating agent HEDTA and said two surfactants (Chemeen and Igepal) have been added to the immersion silver plating solution. They clearly do not figure in the plating solution of D1.

[2.5.2] Although the definition “comprising” of claim 1 does not exclude such additional components the present application is absolutely silent with respect to an optional addition of such a chelating agent like HEDTA, or of surfactants such as said Chemeen T-15 or Igepal Co-730 (compare point 2.3.1 above), let alone that such components should be added in such considerable amounts.

From a comparison with the components of the composition, temperature and treatment time of example A and the composition and corresponding parameters of examples I-III of the present application (see point [2.3.2] above) it is evident that more than 7 parameters (additional components HEDTA and surfactants, different imidazole in a 10-times higher concentration, lower concentration of nitro aromatic oxidant, longer treatment time and somewhat higher temperature) are modified.

[2.5.3] D1 is likewise silent with respect to the addition of the chelating agent HEDTA and surfactants (compare points [2.2.2] and [2.2.3] above) as admitted by the appellant at the oral proceedings. From a comparison between the components of the composition, temperature and treatment time of example A and the composition and corresponding parameters of the abstract of D1 it is evident that at least 3 parameters (additional components HEDTA and surfactants, different imidazole and longer treatment time) are modified.

[2.5.4] Taking account of these modifications, both in comparison with the parent application and the closest prior art D1, it is evident that the experiments A, B and C according to D2 do not represent comparative tests as required by the established jurisprudence to demonstrate an alleged effect.

According to this established jurisprudence, if comparative tests are chosen to demonstrate an inventive step on the basis of an improved (or surprising) effect, the nature of the comparison with the closest state of the art must be such that the alleged advantage or effect is convincingly shown to have its origin in the distinguishing feature of the invention compared with the closest state of the art (see Case Law, 6^th edition 2010, section I.D.9.9; see T 197/86 [6]; T 234/03; T 378/03).

The appellant argued by reference to T 35/85, mentioned in the same section of the “Case Law of the Boards of Appeal”, that it should benefit from the qualification that decision applied to this “established jurisprudence”. Its variants lay close to the invention so that the advantageous effect attributable to the distinguishing feature was more clearly demonstrated. This cannot be accepted since the comparison remains executed with more than one parameter different from either the examples of the present application or the comparison of the abstract of D1. The decisions cited in that part all have in common that it is only the distinguishing feature which is different in the “closest variant” as allowed by the cited decisions. Having, 7 respectively, 3 parameters different can hardly qualify as a “closer variant”.

[2.5.5] Since D2 cannot be accepted as a comparative test the alleged effect of the nitro aromatic oxidant vis-à-vis the closest prior art D1 has not been proven and all the appellant’s arguments based thereon, including the problem to be solved, need not be considered.

[2.6] Furthermore, even if these experiments A, B and C according to the declaration D2 would be considered, they do not prove that a technical effect may be achieved “across the breadth of the claim” as alleged by the appellant.

[2.6.1] D2 discloses a single example, i.e. example A which composition comprises all four components specified in claim 1, made with a concentration of 0.75 g/l (corresponding to 750 ppm) of the preferred oxidant, i.e. 3,5-dinitrosalicylic acid (which is the trivial name for the compound “3,5-dinitrohydroxybenzoic acid” disclosed in the present application). This concentration is thus within the preferred range of from 0.5-2 g/l (corresponding to 500-2000 ppm) specified in the first paragraph at page 7 of present application as originally filed.

An example containing 750 ppm of the nitro aromatic oxidant represents, however, no proof at all that a non-de minimis concentration of 5 ppm thereof would be effective.

[2.6.2] The declaration D2 of Ms Toscano is totally silent with respect to a minimum threshold concentration of the nitro aromatic oxidant.

The appellant’s argument that Ms Toscano does not see a minimum threshold as necessary cannot hold since one of her conclusions based on the three experiments A, B and C as drawn in the fourth bullet point of paragraph 4, quoted by the appellant in support, merely and non-specifically states

“In optimizing an immersion silver plating bath, the presence and concentration of these additives can be manipulated in various ways to achieve good results”.

This non-statement with respect to a minimum threshold concentration, however, does not allow to conclusively derive that such a minimum threshold does not exist, particularly when considering her conclusions in the first and second bullet points of paragraph 4 that neither imidazole nor organic nitro compounds are necessary to achieve an acceptable silver plate.

[2.7] According to the established case law, features which do not contribute to the solution of the problem set in the description are not considered in assessing the inventive step of a combination of features (see Case Law, 6^th edition 2010, section I.D.8.4, in particular T 206/91 [5.5]).

Since process claim 1 includes silver plating compositions including unspecified, therefore also ineffective concentrations of the nitro aromatic oxidant (see points [2.3.3] and [2.4] above) this feature can only be considered as an arbitrary feature, because it is not credible that it contributes to the solution of the underlying technical problem. The Board therefore does not further consider it. Moreover, in a case like the present one it considers that for the same reason the formulation of a less ambitious problem, i.e. to provide an alternative solution with the same effect, based on this alleged distinguishing feature cannot hold either.

Since there are no further distinguishing features it is not feasible to identify the technical problem to be solved.

Therefore, since no technical problem can be identified which is solved by the subject-matter of process claim 1, the Board considers that claim 1 of the first auxiliary request lacks inventive step (A 56). The first auxiliary request is therefore not allowable.

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NB: This decision has also been presented on Le blog du droit européen des brevets.