Analytical investigation on thermal-induced warpage behavior of ultrathin chip-on-flex(UTCOF) assembly

作     者：CHEN JianKui XU ZhouLong HUANG YongAn DUAN YongQing YIN ZhouPing 

作者机构：State Key Laboratory of Digital Manufacturing Equipment and Technology Flexible Electronics Research Center Huazhong University of Science and Technology 

出 版 物：《Science China(Technological Sciences)》 (中国科学（技术科学英文版）)

年 卷 期：2016年第59卷第11期

页      面：1646-1655页

核心收录：

学科分类：080903[工学-微电子学与固体电子学] 0809[工学-电子科学与技术（可授工学、理学学位）] 08[工学] 

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 51475195, 51322507 & 91323303) National Science and Technology Support Program (Gant No. 2015BAF11B02) 

主　　题：microelectronic packaging warpage layerwise theory ultrathin chip 

摘      要：The serious warpage issues of ultrathin chip-on-flex(UTCOF) assembly induced by mismatched thermal stresses have greatly affected the mechanical stability and reliability of emerging ultrathin chip packaging technology. Currently, a theoretical prediction as a convenient and straightforward approach is still lacked for describing effectively the thermal-mechanical behavior of UTCOF during the adhesive curing and cooling process. In consideration of the adhesive thickness approximating to ultrathin chip and flexible substrate thickness, we develop a layerwise-model of ultrathin chip-adhesive-flex structure under plain strain condition, where the behavior of thick adhesive bonding can be described precisely through increasing the subdivided mathematical plies. Further, the analytical results show that the concave and convex forms of ultrathin chip warpage yield at the end of the curing and cooling process respectively. Meanwhile, the effects of its structure dimensions and material properties are also revealed for discussing a way to relieve the extent of ultrathin chip warpage. Additionally, in order to verify the validity of the theoretical prediction, we also introduce the corresponding numerical technique and experimental method. These results suggest that a kind of rigid and ultrathin flexible substrate such as metal foil should be adopted for small warpage of ultrathin assembly.