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TechWaTch
Improving ICT Modification Times with CAD/CAM Software
By Olaf Rohrbacher, Product Manager — CAD/CAM Software, Digitaltest GmbH I
f a product is redesigned or obso- lete components must be re- placed, these changes affect every
subsequent process in electronics manufacturing. From solder paste printing to assembly, inspection and testing, every step is impacted. In-circuit testing (ICT) is often
a major challenge for redesigns. While the bed-of-nails tester delivers unbeatable cycle times, its fixture technology makes it inflexible. The performance of a test system in a production line depends not only on the cycle time, but also on the time it takes to make setup changes. Solder paste printing, compo-
nent placement and soldering are easy to adapt to a new design. A new stencil, for example, can usually be produced within a day. Component placement systems also do not create bottlenecks, because the feeders can be set up apart from the machine. ICT involves considerably more
work for two reasons. First is the possibility that mechanical changes
must be made to the fixture, and sec- ond is the updating of the test pro- gram. One idea would be to switch to flying probe testing, which does not require a fixture, but this method cannot compete with the cycle times offered by ICT.
Effective Planning In production planning, know-
ing how long the ICT changeover process will take is crucial. For test engineers to estimate the extent of the modifications on the assembly and their impact on the fixture and the test program, they need detailed information. In most cases, the assembly
comes with a lot of paperwork. These change reports fill entire folders. It can easily becoming time-consuming to filter out the relevant information for the test in addition to reports on screws, cables and plates. The test engineer finds the rele-
vant information in the BOMs, schematics and CAD data. A suitable
software solution would be able to compare the data at different develop- ment stages and provide meaningful evaluations. C-LINK is a CAD/CAM software from Digitaltest that pro- duces all of the necessary data for the assembly and testing of PCBs. All revisions are entered into the CAD data. If this data is imported in-
The performance of a
test system in a production line depends not only on the cycle time, but also on the time it takes to make setup changes.
to C-LINK, the software recognizes the differences in the layout status. The “Compare Boards” function then delivers a detailed report. The differ- ences are listed in tabular form and displayed in the layout. Differences in the component values and in the netlist are found, as well as missing and added components. With this overview, the test engineer can make a realistic statement about necessary changes in the test program.
Comprehensive Reporting The report created with the
“Compare Boards” function in C- LINK allows quick navigation using hyperlinks. These can be used to cre- ate a list of what needs to change in the test program. If the assembly has changed, measured values must be adjusted in the test program. If com- ponents have been added, they must be recorded. Also, if components have been re-
moved, the test steps are commented out or deleted. If components are con-
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nected to other networks on the new module version, they will be tested through other channels in the future. C-LINK also helps with assem-
bly variants. Using the “Version Dif- ferences” function, a report clearly dis- plays the differences in the placement. The component properties to be com- pared can be set manually. The com- parison is stored as an HTML file in the board directory and the compo- nents are linked with hyperlinks to the graphical display. If the test pro- gram development is advanced or al- ready finished, the automatic program generator (APG) in the system soft- ware CITE can extend the existing test program by one or more new vari- ants in an update mode. In addition to the test program,
the design modifications also have decisive consequences for the exist- ing test fixture. In addition to needle positions, channel numbers, diame- ter, and head type, the fixture design in C-LINK can also include all me- chanical components (e.g. catch pins, hold-down pins, spacers, transfer pins, OpensCheck plates, etc.). The software can also produce a table that lists which pins can no longer be used, because the test pad has been moved in CAD. This is a standard function in
many CAD/CAM solutions, but C- LINK offers more. All of the mechan- ical components of the old fixture are checked and, if possible, transferred to the automatically generated TestJob. If, for example, a component is moved so that a collision with a hold-down occurs, this is reported. This report can help the CAD
developer to make the assembly testable with the existing fixture. This not only saves time, but also money, since the fixture no longer needs to be converted. In addition, several revisions can be tested with a single fixture, meaning less storage and conversion costs. The new CAD data is compared
with the released BOM via a freely configurable BOM import module. In just a few processing steps, probes are placed on the nets that are no longer or not yet contacted, taking into account the existing adaptation. The drilling data output only writes the newly added tester pins to the CNC files. These delta files contain all of the necessary information to re- drill and wire the existing fixture. If the changes are too extensive and a new fixture is necessary, C-LINK will provide the complete drilling and wiring data. Contact: Digitaltest, Inc., 5046
Commercial Circle, Suite C, Concord, CA 94520 % 925-603-8650 Fax: 925-603-8651 E-mail:
dt-sales@digitaltest.net Web:
www.digitaltest.com r
See at IPC APEX, Booth 3533 See at APEC, Booth 229
February, 2019
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