Failure Probability Estimation of Anisotropic Conductive Film Packages With Asymmetric Upper-to-Lower Pad Size and Misalignment Offsets
Anisotropic conductive films (ACFs) are widely used in the packaging of flat panel displays and liquid crystal displays and for attaching bare chips to both flexible and rigid substrates. This paper utilizes the V-shaped curve method to analyze the failure probability of ACF packages with an asymmetric upper/lower pad size and misalignment offsets. In the proposed method, the probability of opening failures is modeled using a Poisson function, modified to take into account the effects of the pad-width difference and misalignment offset on the effective conductive area between opposing pads. Meanwhile, the probability of bridging failures is evaluated using an enhanced bridging model based on the distance between the neighboring pad pairs in the array. The failure probability of the pad array is evaluated as a function of both the difference in width of the upper and lower pads and the degree of misalignment between the opposing pads in the array. The results show that the V-shaped curve method provides the means to predict the ACF volume fraction which minimizes the failure probability of the ACF assembly given a knowledge of the pad-width difference and the misalignment offset. In addition, it is shown that when the misalignment offset is greater than the pad-width difference, the minimum failure probability reduces as the pad-width difference increases due to the corresponding increase in the effective conductive area between opposing pads. Conversely, when the misalignment offset is less than the pad-width difference, the minimum failure probability increases with an increasing pad-width difference due to the corresponding reduction in the effective conductive area between the pads.
Effects of Systematic and Stochastic Errors on Estimated Failure Probability of Anisotropic Conductive Film
This paper analyzes the effects of systematic and stochastic errors on the failure probability of anisotropic-conductive-film (ACF) assemblies estimated using the V-shaped-curve method. It is shown that the effect of systematic errors varies as a function of the volume fraction and the volume-fraction bias. The effects of stochastic errors are investigated by using an in-house software program to generate random conductive-particle distributions in the pad and inter pad regions of the ACF package for the given volume fractions and package geometries. The dependences of the coefficient of variation (CV), essentially the degree of uniformity of the particle distribution, and the failure probability on the volume fraction are examined, and the corresponding results are used to derive the correlation between the stochastic error and the CV for a given volume fraction. In general, the current results indicate that the effects of systematic errors on the accuracy of the estimated failure probability can be controlled by improving the accuracy with which the resin and conductive-particle components of the ACF-compound material are weighed during the ACF fabrication process. However, the effects of stochastic errors cannot be controlled and vary as a function of the volume fraction and the degree of nonuniformity of the particle distribution. Nevertheless, the results indicate that the effects of both systematic and stochastic errors can be suppressed by specifying the volume fraction as the value corresponding to the tip of the V-shaped curve when designing the ACF compound.
Fungal Biotransformations in Pharmaceutical Sciences
The regio- and stereoselective conversion of complex substrates represents one of the major advantage of microbial biotransformation. This chapter covers the biocatalytic capacities of fungi to derivatize bioactive small molecules, both from natural sources and from synthetic compounds. We focus particularly on sterol and taxane biotransformation. We also present examples at the interface of biotransformation and pathway engineering using recombinant organisms, with an emphasis on the production of lovastatin derivatives. Finally, we highlight selected studies on fungal xenometabolism which serves as a model to study the breakdown of drugs in mammals.