Design-For-Test is becoming crucial to ensure complex board performances. In the traditional Design flow, DfT is a specific step after the layout phase as addressed by tools provided by Siemens, Mentor, Demille and Vayo. The CAD file is loaded and a mechanical analysis is performed in order to identify the physical access for In-Circuit or Flying probe test.
With the staggering board density we are now facing, we need to consider the DfT as part of the complete workflow (not just for probe placement), verifying the testability at different stages in order to ensure the highest level of test quality for the minimum test cost.
twExpress has been developed to meet this vision for a software tool that will allow users to analyze each stage of the design to production workflow within a single tool.
This is achieved by the following stages:
- From Schematic, verify that electrical DfT requirements are adhered to in order to maximize test coverage, optimize test probe placement according to test strategy definition, estimate test coverage, estimate cost modeling, production yield and TL9000 – initial return rates.
- From layout, verify mechanical rules, allocate test probes, estimate test coverage based on the real physical access, and generate test programs including input list and test models for the most popular test platforms.
twExpress includes CAD importers supporting schematic netlist, layout, schematic graphics and design or test models for all the design tools used within the industry. This is a key differentiator as other commercial DfT tools work only from the layout stage. twExpress operates from native CAD formats and insures the full interoperability between all stages across the design/manufacturing flow.
In the past, test engineers had to use a variety of software tools to (a) verify that a board had been designed with adequate testability in order to maximize test coverage, and (b) verify that the board layout engineer had placed test points where requested. However, once the test points had been validated it was still necessary to develop the ICT or flying probe test program files, which required another process stage. With twExpress, all stages are managed within a single tool through an integrated methodology.
Test coverage is estimated using theoretical models for a wide range of test and inspection strategies such as APM, AOI, AXI, BST, FPT, ICT etc, and Functional Test, that can be tuned to reflect the test and measurement capabilities of the target tester. Once the test/inspection programs have been completed, TestWay Express can read the debugged test program or test report and compare the coverage between the estimated and measured analysis using industry standard metrics, and identify any misalignment.
Numerous coverage importers are available for a wide range of the test/inspection machines used within the industry such as Acculogic (BS, Scorpion, SPRINT); Aeroflex (4200, 5800); Agilent Technologies (i1000, i3070, 5DX, SJ10, SJ50); ASSET; CHECKSUM; CORELIS; Cyberoptics, DrEschke; Europlacer; GOEPEL (CASCON, OPTICON); JTAG Technologies; Mirtec; MYDATA, OMRON; Orbotech; SAKI; SEICA; SPEA (3030, 4040); TAKAYA (APT8000, APT9000); Teradyne (Z1800, Spectrum, GR228x, TS124); TRI (TR7500, TR8001); VI Technology; VISCOM; XJTAG etc.