T 0229/85 (Etching process) 27-10-1986
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Inventive step
Simplicity of the solution
Return to a concept regarded as superseded
I. European patent application No. 81 109 230.3 was filed on 29 October 1981 claiming a German priority of 10 December 1980 and published as No. 0 053 719 on 16 June 1982. It was refused by decision of the Examining Division of the European Patent Office on 23 May 1985 on the basis of the five claims originally filed, Claim 1 of which reads as follows: "A process for etching metal surfaces, particularly in the production of printed circuits, in which a metal such as copper is removed from the circuit board by means of a solution containing sulphuric or phosphoric acid and hydrogen peroxide, the said solution being recirculated and used again for etching purposes, characterised in that a quantity of hydrogen peroxide just sufficient for a single etching operation is added to the solution immediately before or at the moment that the solution is applied to the circuit board it is desired to etch and that when the etching process is completed practically no hydrogen peroxide remains in the solution".
II. The Examining Division refused the application on the grounds of lack of inventive step, stating that US-A 3 756 957 (1) disclosed a method of etching metal surfaces using a solution containing sulphuric acid and hydrogen peroxide in which the undesired decomposition of the hydrogen peroxide was inhibited by the addition of a negative catalyst. The characterising feature of Claim 1 was obvious to a person skilled in the art who had set himself the task of preventing decomposition of the hydrogen peroxide by copper ions after the etching process even without the use of negative catalysts, since he would be aware that the only advantage of an excess of hydrogen peroxide was to increase the etching speed and that the presence of hydrogen peroxide was only essential during the actual etching process. The process of the invention intentionally forewent the greater etching speed and therefore involved the addition of a quantity of hydrogen peroxide only sufficient for a single etching operation. A skilled person would have no difficulty in translating this idea into practice since the only matter to be ascertained was the actual amount of hydrogen peroxide that was sufficient and this could be done by routine tests.
III. The applicants appealed against the decision on 3 July 1985, duly paying the appeal fee, and submitted grounds in support of their appeal on 27 August 1985. These were essentially as follows: The present state of the art did not permit an etching process using hydrogen peroxide in an acid solution to be carried out economically without the addition of stabilisers. Compared with the state of the art the process of the invention did involve an inventive step, since in all the literature dealing with the use of hydrogen peroxide for etching purposes there was no mention that the problem of the catalytic decomposition of hydrogen peroxide could be solved using the means proposed by the invention. On the contrary, it was stated that this was only possible using elementary metal would be substantially reduced. The appellants request that a patent be granted on the basis of the application as originally filed.
1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is therefore admissible.
2. The application states in the preamble to the specification (page 2) that processes for etching metal surfaces, particularly those of printed circuit boards, are known in the art in which a metal such as copper is etched using a solution containing sulphuric or phosphoric acid and hydrogen peroxide and the solution is recirculated and used again for etching purposes. Such processes were not adopted in practice because of the serious disadvantage represented by the fact that the metal ions released during the etching process acted as catalysts in the decomposition of the hydrogen peroxide, boosting its consumption to an economically impracticable level (see (1) column 2, line 68; column 3, line 5 and column 3 lines 40 - 46).
3. The method used in US-A-3 756 957 (1) attempts to solve the problem of the decomposition of hydrogen peroxide in etching solutions containing sulphuric acid by adding certain amines, amides and imines to act as stabilisers (see column 1, lines 10 - 18; column 2, lines 15 - 20, column 2, line 67; column 3, line 53 and Claim 1). By inhibiting the decomposition of hydrogen peroxide it is possible to render the etching process economically viable and even to make it possible for the etching solution to be treated as is practically and ecologically necessary for recycling by ensuring that the residual concentration of hydrogen peroxide in the solution before treatment is less than 5 g/l and if possible is 2 g/l (see column 7, lines 27 -33).
4. In contrast to the state of the art the problem the present application sets out to solve is to devise an etching process similarly involving as low a consumption of hydrogen peroxide as possible and which permits the spent etching solution to be regenerated without difficulty, thereby ensuring optimum use of electric power. The solution proposed is that an amount of hydrogen peroxide just sufficient for a single etching operation is added to the etching solution either directly before or actually when it is applied to the circuit board to be etched, and that when the etching process has been completed a minimum amount of hydrogen peroxide remains in the solution. This procedure makes it possible to operate without a stabiliser and with a low concentration of hydrogen peroxide. The Board considers mention in the claim of the fact that no stabiliser is used to be superfluous because the claim is clear and the facts generally emerge unambiguously from the description as a whole. The advantages of this process are so obvious that the Board sees the invention as genuinely solving the problem posed.
5. Since no process of this kind is disclosed in the literature reflecting the state of the art available to the Board, it must be regarded as novel. This makes it necessary to consider whether the process involves an inventive step. The Board here agrees with the Examining Division in basing itself on (1). As already mentioned this patent describes a process for etching metal surfaces in which the catalytic decomposition of hydrogen peroxide is markedly reduced by the addition of certain stabilisers. The disputed decision states that because of the problem set the solution proposed in the application would have been obvious by simple reasoning to a person skilled in the art having knowledge of (1). The problem is seen as to prevent the decomposition of hydrogen peroxide without using negative catalysts (stabilisers). This definition of the problem, possibly influenced by the information contained in the present application (page 2, last paragraph), inadmissibly incorporates part of the solution offered by the invention. The idea of doing away with stabilisers is an essential part of the teaching of the invention as reflected in the solution given above and ultimately consisting in regulating the amount of hydrogen peroxide added to the solution and its timing. However, the technical problem addressed by an invention must be so formulated as not to contain pointers to the solution, since including part of a solution offered by an invention in the statement of the problem must, when the state of the art is assessed in terms of that problem, necessarily result in an ex post facto view being taken of inventive activity. For this reason alone the decision of the Examining Division cannot stand.
6. If, on the other, hand the rather unambitious technical problem is formulated as in paragraph 4 of this decision, citation (1) does not give any pointer to the solution offered by the application since it does not disclose any alternative to using as little hydrogen peroxide as possible - another aim of the invention - combined with easy regeneration of the etching solution. On the contrary, the approach adopted in (1) is entirely different in recommending the use of stabilisers and high concentrations of hydrogen peroxide in the etching solution (see especially examples 2 - 5 which involve up to 50 g/l hydrogen peroxide). The contrary solution of the present application, which after all seeks to avoid the use of stabilisers and high concentrations of hydrogen peroxide in the etching solution, cannot be obvious from this proposal.
7. The need to include a stabilising agent in etching solutions containing hydrogen peroxide emerges not only from (1) but from a number of other patent documents - namely (2) GB-A-1 176 892 (see page 2, lines 19 - 22) and (3) FR-A-2 392 100 (see page 2, lines 17 - 20 and lines 24 - 29). Since all these patents are based on etching solutions containing stabilisers, they are not designed to lead a person skilled in the art to abandon the concept. The application's departure from the stabilisation of the hydrogen peroxide in the etching solution that had become customary and return to the use of an unstabilised hydrogen peroxide solution - considered superseded - must be regarded as a typical indication of inventive step. A further such indication is the notable simplicity of the solution proposed, which despite the considerable amount of activity in this field had escaped those concerned. The process as claimed in Claim 1 of the application therefore involves inventive step, as do Claims 2 to 5 which refer back to Claim 1 and derive their inventiveness from it.
ORDER
For these reasons, it is decided that:
1. The decision of the Examining Division of the European Patent Office is set aside.
2. The matter is referred back to the Examiming Division for a patent to be granted on the basis of the application as originally filed.