Page 293 - Fundamentals of The Finite Element Method for Heat and Fluid Flow

SOME EXAMPLES OF FLUID FLOW AND HEAT TRANSFER PROBLEMS

Figure 9.26 Element model of PBGA 285

51.679 52.419 53.16 53.9 54.641 55.382 56.122 56.863 57.603 58.344

Figure 9.27 Temperature distribution of quarter PBGA model

The analysis was carried out for a free convection environment. The temperature distri-
bution of the package can be obtained by plotting nodal solution contours. The results are
shown in Figures 9.27 and 9.28 for a quarter model and an expanded full model and indi-
cate that the maximum temperature occurs in the chip itself. Since the board temperature
has been specified, the thermal resistance between the chip and the board R jb is given by

58.344 − 53
T j − T b
◦
R jb = = = 7.125 C/W (9.2)
P 0.75
where T j = 58.334 C was obtained from the analysis.
◦