Methodology for accurate junction temperature estimation of SIP(System in Package)

As the mobile products have been developed, lots of devices of various functions should be packaged into the limited space. Therefore, as many as possible packaging multi-dies are needed in a small package. Compared with discrete packages, System in Package (SIP) can provide better solutions for power saving, EMI reduction, max frequency upgrade in spite of its higher cost, low test yield, poor quality assurance, and more complicated manufacturing process. But, having many chips in one package has raised concerns related to heat dissipation, which has become one of the most serious problems in the design of SIP. Accordingly, a method to obtain T_j for each chip from the power inputs is needed. This is quite significant at the SIP promotion and design stage, though the temperature value would be changed by system environment. In this paper, a new approach to determine the junction temperatures of the SIP is proposed. The average temperature of the chips was calculated by RSM, and the temperature difference from the average temperature was calculated by linear superposition. The "hot spot factor", which can reflects the effect of chip size and hot spot on the chip was newly proposed. Using this approach, one can calculate device junction temperatures simply and accurately.