MOISTURE DIFFUSION AND HEAT-TRANSFER IN PLASTIC IC PACKAGES

This paper deals with finite-element (FE) simulations of moisture diff usion during preconditioning of plastic integrated circuit (IC) packag es as well as the simultaneous diffusion of heat and moisture during v apor phase reflow (VPR) soldering, More realistic 2-D analyses are des cribed. The results show good agreement with experimental data. The li mitations of hitherto one-dimensional (1-D) analyses are also examined , The transient build-up of water vapor pressure in the delaminated pa d-resin interface during vapor phase reflow soldering is also obtained , It is found that, irrespective of the manner of moisture preconditio ning (moisture absorption or desorption), the same critical water vapo r pressure level of about 1 MPa is obtained for the plastic IC package under study, It is also shown that the water vapor in the delaminated interface never reached saturation during the short period when solde r is reflowed and re-solidified.