## 1 Introduction
### Relevance and Aim  
Smart and individualized products have become very popular and are in high demand for various industries [1; 2; 3]. Micro-mechantronic systems (MMS) are key enabling technologies for the development of smart products, such as intelligent telephones, intelligent sensors for machines and plants or micro robots. Yet, these only represent a very small selection of such applications [4]. The European Commission expressed the importance in a strategy excerpt that MMS are not only essential to digital products and services, but they also underpin innovation and competitiveness for all major economic sectors [5; 6]. However, the increasing demand for individualization poses great challenges to the engineering of MMS, as the entire MMS manufacturing process is based on the concept of large-scale production [7]. The reason for a large-scale production strategy is that MMS are often components of standardized mass products such as smartphones, automobiles or computers [4; 8]. Now, with the increasing demand for individualization, a growing demand can be assumed for the embedding of MMS into individualized products or individual assembly spaces to make these products smarter or give them additional functionality. Some examples of individualized MMS (iMMS) can already be shown in areas of mechanical engineering and medical technology, in which individual components of MMS are used and needed [9; 10; 11]. A typical fabrication technology for iMMS are molded interconnect devices (MID), also named mechatronic integrated devices, due to their high potential for functional integration, miniaturization and especially design flexibility [12]. MID are often applied in size-critical applications [13]. To ensure cost-efficient and individualized MID production, one approach is to redesign established process chains and use digital process chains such as additive manufacturing technologies [14]. A digital process chain can be defined as a manufacturing chain that includes digital manufacturing technologies (DMT). DMT are characterized by the fact that conventional manufacturing technologies are combined with digital techniques [15]. However, there are few cases that emphasize the challenges of developing and producing iMMS with a digital process chain. So, there is a lack of knowledge about the engineering design process (EDP) within the context of iMMS. To meet the requirements such as time, cost and quality, development methods and adapted development processes can help achieve the requirements.  
The general relevance of using methods and tools within the development and planning stage is well known [16]. This could play a greater role for iMMS, as these products are highly dependent on technologies and need to fulfill various requirements such as time, cost and quality. [PERSON] et al. [17] also describe the need for new approaches in product development, in particular for intelligent technical systems, which are always based on MMS. There is a gap between complexity in product and production on the one hand and performance of the product development in industrial practice on the other hand. This gap seems to be widening.  
The aim of this study is to develop a case-based methodology that supports the creation of an EDP for iMMS by identifying needs for product development methods within the EDP. The research objectives are reached through empirical studies such as expert interviews and case studies.