Novel Material for Improved Quality of RF-PA in Base-Station Applications

New materials and production technology have been introduced into LDMOS 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 160 W/mK to near 200 W/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.