An Improved VLSI Test Economics Analysis System - Laboratory for ...

An Improved VLSI Test Economics Analysis System - Laboratory for ... An Improved VLSI Test Economics Analysis System - Laboratory for ...

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12.07.2015 Views

Market Life Model receives both DFT and no DFT development time from Time Model,than, substrates them to nd development saving time for estimation of extra prot of DFTstrategy.As a result, we compare defect level and prot of DFT with no DFT design to judge ifwe get benet from this DFT strategies. The proposed models describe only a single teststrategy estimation, so optimal test strategy can be obtained by re-evaluating the modelsfor all available strategies. Next section discusses our Cost Model in detail.2.4 Cost ModelCost Model hierarchically analyzes various costs. Therefore, total cost is divided into threeparts: developmental cost, manufacturing cost, and testing cost according to their stages.Estimation equation is given byC = Cd + Cm + Ct + K; (2.9)where K denotes the unmodeled cost. The user can modify this equation using K. Forexample, he can assign K to ,Ct+120 if testing cost is xed to $120 in our model. Moreover,each stage consists of various detailed items, as shown in Figure 2.3.C(overall cost)Cd(development)Cm(manufacture)Ct(test)CdieCpackage CmaskCdmp(men power)Cdsgn(design)Cdequip(equipment)Cdmang(mangement)Cdspace(space)Cw(wafer test) Cp(pre-burn-in test)Cproto(prototyping)Cb(final test)Figure 2.3: Hierarchical structure of Cost Model.16

However, cost is greatly impacted by time and volume as we found in our analysis. Theway how time impacts cost is therefore performed in rst subsection. Second subsectionconsiders the relation between cost and volume. Finally, the later three subsections describedetailed item costs in each stage respectively.2.4.1 Impact of Timef 2bf 2bf 1C=f 2b -f 2af 2af 2a1t t 2Figure 2.4: How is cost impacted by time?We consider the capital cost rst. As shown in Figure 2.4 in time t 1 ,acapital of f 1 waspurchased. This capital depreciated to f 2a at time t 2 . If the same money was invested toother project, the estimated revenue is f 2b . The exact cost of this capital should beC f1 = f 2b , f 2a t 1 ,t 2: (2.10)For example, a cost of tester U tester was invested in time t 1 . We used this tester until time t 2in the project. Depreciative ratio per time interval of this tester is assumed R d . Then, thevalue of this tester in time t 2 isf 2a =(1, R d ) N t U tester ; (2.11)where N t is number of depreciation time intervals between t 1 with t 2 . Moreover, if thosemoney was deposed into bank instead of investing tester, nal revenue, including interest, isf 2b =(1+R int ) N t U tester ; (2.12)17

However, cost is greatly impacted by time and volume as we found in our analysis. Theway how time impacts cost is there<strong>for</strong>e per<strong>for</strong>med in rst subsection. Second subsectionconsiders the relation between cost and volume. Finally, the later three subsections describedetailed item costs in each stage respectively.2.4.1 Impact of Timef 2bf 2bf 1C=f 2b -f 2af 2af 2a1t t 2Figure 2.4: How is cost impacted by time?We consider the capital cost rst. As shown in Figure 2.4 in time t 1 ,acapital of f 1 waspurchased. This capital depreciated to f 2a at time t 2 . If the same money was invested toother project, the estimated revenue is f 2b . The exact cost of this capital should beC f1 = f 2b , f 2a t 1 ,t 2: (2.10)For example, a cost of tester U tester was invested in time t 1 . We used this tester until time t 2in the project. Depreciative ratio per time interval of this tester is assumed R d . Then, thevalue of this tester in time t 2 isf 2a =(1, R d ) N t U tester ; (2.11)where N t is number of depreciation time intervals between t 1 with t 2 . Moreover, if thosemoney was deposed into bank instead of investing tester, nal revenue, including interest, isf 2b =(1+R int ) N t U tester ; (2.12)17

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