Solar power is inexhaustible and has become one of the most appreciated alternative energy choices. In the development stage, solar modules are subjected to relevant reliability tests to ensure a long lifetime and optimal power generation efficiency. After the lamination process, the performance of solar modules is closely related to the degree of crosslinking of ethylene vinyl acetate (EVA) sheets. Traditionally, the degree of crosslinking on EVA sheets is obtained using the chemical extraction method to measure the gel content of these sheets. Motivated by lamination data, this study first constructed a statistical model to describe the relationship between the degree of crosslinking on EVA sheets and lamination time. Next, under the specification limits of the gel content of EVA sheets, the optimal lamination time of solar modules was derived, and the optimal allocation for measuring EVA sheets was addressed. The chemical extraction method is time consuming and leads to high pollution. The latest method is differential scanning calorimetric (DSC), which measures the curing degree of EVA sheets as the degree of crosslinking on these sheets. This study determined the specification limits of the curing degree under the DSC method. An example is presented to elucidate the proposed procedure.