Using DOE to improve COB bonbability
In recent years, the Chip-on-Board (COB) package technology has become popular in semiconductor industries. The COB technology, in which the dies are directly mounted onto a printed circuit board (PCB) with bonding wires connecting the die and leads. Besides solder bumps, wire bonding is still the most popular interconnect method. With the development of wire bonding technology in the COB package, we can realize advanced processes with good performance by new wire bonding equipment and more powerful software. However, there are still many challenges to be overcome in the bonding process. In this paper, we did experiments to optimize the bonding parameter using 1.0mil Au wire on COB and successfully found the optimal range of bonding parameters through DOE (Design Of Experiment). By the optimal solution, we further improved the bondability; the second bonding quality was also improved by using BSOB (Bond Stitch On Ball) bonding.
Thermal analysis of a wirebond chip-on-board package
The thermal characteristics of a wire-bond COB package with a calibrated thermal chip was investigated by wind tunnel experiments and finite element analysis. Thermal measurements were carried out in a wind tunnel used to simulate steady state natural and forced convection heat transfer conditions. Finite element analysis of the steady state heat transfer condition was simulated using a two-dimensional model of the wire-bond COB package. The finite element model was also employed in a thermal stress analysis of the wire-bond COB package subjected to accelerated thermal cycling loading.
Heat transfer and nonlinear thermal stress analysis of a convective surface mount package
Most prior heat transfer and thermal stress analyses of convective surface mount packages have relied on either an isothermal (constant temperature) model or a constant heat transfer coefficient thermal model. This usually leads to a concern for the accurate estimation of the local temperature distributions and the induced stresses. To release this concern, this paper presents the use of the finite element method in conjunction with a local heat transfer coefficient model in predicting the local temperature and stress distributions of a ceramic ball grid array (CBGA) package. A thermal boundary condition of the local heat transfer coefficient model was obtained from a previous computational fluid dynamics (CFD) solution. The analysis results are compared with that predicted by the isothermal model and the constant heat transfer coefficient model. Instances where the temperature dependent and elastic-plastic behavior are significant in some components of the modeled package are also examined.