As the demand for flexible hybrid electronics has increased extensively e.g. for the internet of things (IoT), electronic skin and wearables applications, the implementation of devices based on low-cost materials such as PET, paper, and unpackaged bare dies have become crucial for economical mass production. To facilitate flexibility for instance in wearables, the rigid silicon-based components are also deemed to become ultra-thin, which raises major challenges in terms of handling and reliable integration. In this paper, the hybrid integration of ultra-thin dies on PET and paper-based printed substrates is investigated. Silicon dies with different thicknesses from 10 to 50 μm with an internal daisy-chain structure were made and flip-chip bonded to screen-printed substrates. The bonding was conducted by using two types of anisotropic conductive adhesives, i.e. aniso-tropic conductive films (ACF) and anisotropic conductive paste (ACP). The effect of die encapsulation on the reliability of the assembly was also assessed by employing a protective foil. For reliability analysis, a cyclic bending test was carried out to identify the failure cycle. The successful integration of ultra-thin chip on the low-cost printed flexible substrate was obtained by optimizing the bonding parameters with both ACF and ACP. It was revealed that in flexible hybrid electronics; the thinner the die, the higher is the reliability, as the thinner dies promise superior flexibility, and can withstand higher bending stresses. Moreover, it was found that encapsu-lation of the thin die in a foil dramatically increases the long-term reliability of the bonded chip.