Dissimilar micro-friction stir welding (dissimilar μFSW) can be a preferred choice for joining dissimilar materials having thickness ≤ 1000 μm. The technique's potential applications are in miniaturized components, where the inherent benefits of the process, such as low temperature, low distortion, and clean joining, are advantageous compared to fusion welding. However, the challenges associated with dissimilar μFSW hinder its full potential applications in the relevant industries. The challenges are particularly a combination of two different characteristics of the process (i) the complexities of simultaneously fulfilling the dissimilar materials' demands due to the vast differences in the two materials' mechanical and thermal properties and (ii) the problems due to reduced sheet thickness. In this regard, the present work is a comprehensive and timely review of the research works done on dissimilar μFSW targeted at easily acquainting the research community about the know-how and the state of the art of the process. The review is broadly divided into three crucial parts: the process inputs/requisites, process mechanics, and process performance. The details about the μFSW tool, process parameters, and relative sheet positioning are discussed under the heading process inputs/requisites. Concerning the process mechanics, the intermetallic compound formation, defect generation, and material mixing are discussed. The joints' resulting performance is shown by detailing the essential properties such as formability, residual stresses, fatigue, hardness, and tensile strength. Additionally, several future research directions are presented at the end of this critical review to motivate further improvements in this joining technique and instigate its utility in relevant industries.

异种微摩擦搅拌焊接（异种 μFSW）是连接厚度 ≤ 1000 μm 异种材料的首选。该技术的潜在应用是在小型化部件中，与熔焊相比，该工艺的固有优势，如低温、低变形和清洁连接，具有优势。然而，与不同 μFSW 相关的挑战阻碍了其在相关行业中的全部潜在应用。挑战尤其是该工艺的两种不同特性的结合 (i) 由于两种材料的机械和热性能差异巨大而同时满足不同材料需求的复杂性以及 (ii) 由于减少的片材而导致的问题厚度。在这方面，目前的工作是对不同 μFSW 研究工作的全面及时回顾，旨在让研究界轻松了解该过程的专有技术和最新技术。审查大致分为三个关键部分：过程输入/必要条件、过程机制和过程性能。有关 μFSW 工具、工艺参数和相对片材定位的详细信息在标题工艺输入/必要条件下进行了讨论。关于工艺力学，讨论了金属间化合物的形成、缺陷的产生和材料混合。接头的最终性能通过详细说明基本特性来显示，例如可成型性、残余应力、疲劳、硬度和拉伸强度。此外，