1. Introduction

A recent EPO Board of Appeal decision concerning a hearing-aid assembly provides a particularly detailed illustration of how the requirement for a “credible technical effect” may influence the assessment of inventive step.

The case is particularly interesting because the Board did not deny that the distinguishing features were technical in nature. Instead, the Board considered that the alleged technical effects were not credibly achieved over the whole breadth of claim 1. As a result, the distinguishing features were treated as an “arbitrary modification of the prior art” and therefore incapable of supporting inventive step under Article 56 EPC.

The decision also touches on several broader issues currently relevant in EPO practice, including claim interpretation after G 1/24, the relationship between technical effect and technical contribution, and the RPBA’s strict front-loading approach.

2. Background of the case

The patent concerned an electrical assembly for a hearing aid. The assembly included a rigid printed circuit board (PCB) and a flexible printed circuit board (FPCB) carrying an antenna. The claimed structure required the antenna terminal on the FPCB to be electrically connected to a pad on the PCB, with the terminal arranged at an angle relative to the PCB surface. In addition, the PCB included an indentation at its edge configured to accommodate at least part of the antenna terminal.

According to the patent specification, this arrangement allegedly provided increased design flexibility, simpler PCB routing, reduced PCB size, reduced mechanical stress on the flexible carrier, and a lower risk of production errors. The core distinguishing feature of claim 1 was therefore essentially the requirement that:

“the first indentation accommodating at least a part of the first terminal”.

The opposition division initially rejected the opposition and maintained the patent as granted. On appeal, however, the Board revoked the patent for lack of inventive step.

3. Claim Interpretation After G 1/24

Referring to G 1/24, the Board reiterated that the claims are the “starting point” and the “basis” for assessing patentability. The Board also acknowledged that the description and drawings must always be “consulted” when interpreting the claims.

However, the Board emphasised that this did not mean that features set out only in embodiments could be used to give the claim a meaning narrower than its wording as understood by the skilled person. In the Board’s words:

“the specific sizes, designs and structures as reflected in the embodiments and in the figures of the patent specification as mere examples cannot be used to further limit the claimed subject-matter”.

This point was central to the proprietor’s case. The proprietor sought to rely on the description to argue that the expression “accommodating at least a part” should be understood as implying an indentation dimensionally commensurate with the first terminal, thereby ensuring correct placement, alignment, compactness and reduced assembly size.

The Board rejected that approach. It considered that the proprietor’s argument was not based on the interpretation of terms actually present in claim 1, but instead:

“effectively seeks to read unwritten limitations into the claim”.

This is an important distinction. G 1/24 requires the description and drawings to be consulted; it does not, however, mean that every structural detail disclosed in an embodiment automatically narrows otherwise broad claim language.

In that respect, the present decision can usefully be contrasted with the post-referral decision in T 439/22. There, the Board gave considerable weight to an express definition in the description when interpreting the term “gathered sheet”. In the present case, by contrast, the proprietor was not relying on a comparable lexicon-style definition of “accommodating at least a part”, but rather on embodiments, drawings and alleged technical effects to import additional structural limitations into the claim.

According to the Board, the claim language still covered embodiments in which the indentation was substantially larger than the terminal, such that the terminal could effectively “float” within the indentation without being laterally constrained. The Board also noted that the claim covered arrangements in which the terminal could be positioned at a significant skew angle, or where the indentation might even be located on a raised portion of the PCB.

In such embodiments, the alleged technical effects relating to alignment, compactness or reduced size would not necessarily be achieved. The Board therefore concluded that the broad wording of the claim remained decisive for the subsequent inventive-step analysis.

4. “Credible Technical Effect” and Technical Contribution

The central issue in the decision was not whether the distinguishing features were technical. The Board expressly accepted that they were technical in nature. Instead, the issue was whether those features credibly achieved the alleged technical effects across the entire scope of the claim.

The Board concluded that they did not. As a result, it considered that the distinguishing features did not credibly contribute to solving a technical problem. This led to one of the key statements of the decision:

“if there is no technical effect, there is no technical contribution to the solution of a technical problem.”

The Board relied on a substantial body of earlier case law holding that features which do not credibly contribute to a technical effect may be treated as “arbitrary features”, “arbitrary modifications”, or “non-functional features”. Such features, according to the Board, cannot support inventive step under Article 56 EPC.

Importantly, the Board did not suggest that the claimed structure was non-technical or meaningless. Rather, the Board considered that the alleged advantages were not credibly obtained over the whole breadth of the claim.

5. The RPBA and the Front-Loading Principle

The decision also contains an extensive procedural discussion concerning late-filed submissions under the RPBA.

During the appeal proceedings, the proprietor attempted to introduce additional arguments that D2 allegedly failed to disclose further claim features beyond those originally disputed. The proprietor also filed several auxiliary requests at a relatively late stage of the proceedings. These requests attempted to narrow the claim by introducing limitations relating to indentation dimensions, raised PCB portions, and the use of solder as the electrically conductive material.

The Board refused to admit these submissions. In doing so, it emphasized that:

“parties must submit their full case as early as possible”

and rejected the proprietor’s argument that the new submissions merely represented an “elaboration” of its earlier case.

The decision therefore provides another illustration of the RPBA’s strict front-loading approach, particularly under Article 13(2) RPBA.

6. Concluding Remarks

The importance of the decision lies less in the specific hearing-aid technology than in the broader principles it illustrates.

First, the decision shows that even clearly technical distinguishing features may fail to support inventive step if the alleged technical effects are not credibly achieved over the whole breadth of the claim.

Second, the case provides a useful illustration of claim interpretation after G 1/24. The description must always be consulted, but this does not mean that limitations from embodiments will automatically narrow otherwise broad claim language. The contrast with T 439/22 is instructive: an express, technically coherent definition in the description may carry considerable weight, whereas embodiment-based attempts to read additional structural limitations into a broad claim may fail.

Finally, the decision also highlights the demanding procedural expectations placed on parties in EPO appeal proceedings. Attempts to reshape the inventive-step case, or to introduce new factual and argumentative lines at a late stage of the proceedings, are likely to face significant resistance under the RPBA framework.