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

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• 作者：JianKui Chen ; ZhouLong Xu ; YongAn Huang…
• 关键词：microelectronic packaging ; warpage ; layerwise theory ; ultrathin chip
• 刊名：SCIENCE CHINA Technological Sciences
• 出版年：2016
• 出版时间：November 2016
• 年：2016
• 卷：59
• 期：11
• 页码：1646-1655
• 全文大小：1,596 KB
• 刊物类别：Engineering
• 刊物主题：Chinese Library of Science
  Engineering, general
  
• 出版者：Science China Press, co-published with Springer
• ISSN：1869-1900
• 卷排序：59

文摘

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.