Epoxy resin is widely used in insulation packaging of electrical equipment and electronic devices. Its curing residual stress may cause matrix defects or even cracks

which is an important hidden danger threatening the insulation reliability of products. Based on the understanding of the packaging structural constraint on epoxy resin and its effect on stress

a thick-walled cylindrical structure for packaging stress testing was designed in this paper

which can freely control the restricted constraint degree of epoxy resin. Furthermore

a methodology for curing residual stress testing and curing process optimization was proposed by utilizing the thick-walled cylindrical structures with equivalent constraint characteristics to actual products. By using the equivalent thick-walled cylindrical structure of a high-frequency transformer product with strain gauge monitoring

the influences of various process parameters on curing residual stress and its mechanism were studied. By prolonging the gel temperature holding duration

reducing the heating rate

and increasing the curing temperature

the thermal expansion stress in heating stage is enhanced and the thermal contraction stress in cooling stage is weakened. As a result

the measured contraction strain induced by curing residual stress is significantly reduced from 1 610×10−6 to 690×10−6

effectively eliminating epoxy cracking and associated breakdown failure within the product. The proposed curing process design methodology and the elucidated curing residual stress evolution mechanisms facilitate the rapid and precise design of curing process for diverse epoxy packaging products.