In this study, a universal modular test setup for a variety of high density package concepts with ball pitches smaller than 0.4 mm is presented. It enables bias loading and online monitoring of multiple test specimens during accelerated environment stress testing according to AEC grade 1 conditions. Humidity is a critical factor when reducing ball pitch and introducing innovative casting compounds (e. g. epoxy resins) for electronic packaging. Therefore, its influence has to be investigated and a reliable test setup is required. The focus of this study is on the overall performance of the test setup under test conditions for storage at temperature and humidity. Experiments during board development were performed, including tests on material behaviour and surface effects due to narrow spacing between neighbouring traces, pads, or grid dimensions. The functionality of the developed test setup is demonstrated by electrical measurements at specimen level and setup system level before, during, and after temperature humidity storage. Potential failure modes at die, package, and board level can be investigated with the presented test setup.