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New materials, design, and production technology have been introduced into laterally diffused metal oxide semiconductor (LDMOS) radio frequency power amplifier (RF-PA) transistors to provide advanced thermal features and increased thermal conductivity (Kth). Recently, Kth of WCu flanges has been increased by nearly 25% from near 160W/mK to near 200W/mK. Further improvements in the latest generation of the RF-PA utilize novel flange materials such as Cu-laminate with even higher Kth, by more than 25% compared to WCu. The development of Cu-laminate flange structures, involved optimization between achieving higher Kth and preserving desired mechanical properties for low stress and long-term reliability. Such optimization provided desired flatness for the RF-PA; yielding in lower interfacial thermal resistance between the RF-PA transistor flange and the next level heat sink. Furthermore, well characterized, highly thermally conductive, and very robust AuSi die attach was employed for efficient and reliable thermal coupling. Constellation of such materials and production technology improved overall quality of the RF-PA, enabling successful implementation in base-stations.
Components and Packaging Technologies, IEEE Transactions on (Volume:28 , Issue: 4 )
Date of Publication: Dec. 2005