Resumo

SEQUEIROS, Elsa Wellenkamp de. Empenos em substratos durante o processo de encapsulamento de memórias. C.Tecn. Mat. [online]. 2009, vol.21, n.1-2, pp.45-60. ISSN 0870-8312.

Warpage of electronic memories during manufacture may be caused by differences in the coefficient of thermal expansion of the materials used: die, substrate, adhesive, gold wire, epoxy mold compound (EMC) and solder balls. However, warpage is greatly affected by package design, dimensions of materials used in the assembly, process assembly steps, equipments, etc. Taking into consideration the Assembly process at Qimonda PT, several experiences were done, in order to reach the goals proposed in this study. Warpage of substrates was measured by profilometry 3D Nanofocus. After measuring substrates during the Assembly process flow, the results revealed that the critical steps, i.e., steps of the assembly process that have a larger impact on warpage and influence more manufacturing, were: Mold, Mold Cure and Solder Ball Attach (SBA). This was the first part of the study as well as the longest one. In all other experiences related with the identification of factors that might affect warpage, measurements were limited to these critical steps. It was concluded that time and conditions of storage (clean room conditions and compartments under nitrogene flow), anti-warpage system and modifications on formulations of EMC were some of the factors that may affect warpage. This increased with time between the critical steps (in clean room conditions). Storage of the lots in compartments under nitrogene flow decreases warpage. Failure of anti-warpage can induce an increment of 200µm in warpage. Modifications in EMC shrinkage (by varying fillers cut dimensions) change the level of warpage. For 3 packages of different Silicon Ocupation Ratio (%SOR), the use of EMC formulation with minor shrinkage improved warpage in the critical steps. Other factors tested have not showed any impact on warpage: different providers of substrates and forced cooling after Mold Cure. But, on the other hand, the use of forced cooling decreased the cycle time and may increase productivity.

Palavras-chave : Warpage; Assembly process; EMC.

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