Test Method ICT - In-Circuit-Test

Passive - Analog ICT

With this test method a large part of manufacturing error can be found.

Inspection process:

• Contact test between test probe and test points
• Short circuit test - every node against every other node
• Test of all passive components

Therby passive components can be tested for correct placement. For active components an orientation tests can be done, if possible, for example for diode paths or internal pullup-resistors of components. Solder joints of active components sometimes can be tested that way.

A special form of passive ICT is ICT are vectorless test methods (Chip-Scan-method and the like,inductive and capacitive methods). These are used with the aim to find manufacturing errors without complex function tests or In-Circuit-libraries of complex components.

Automatic test systems that exclusively use passive test methods are called "Prescreener", with them a major part of typical manufacturing errors can cost-effectively be found.

Active ICT

The active ICT includes the test steps of the passive ICT. Subsequently the UUT is supplied with power and functions of specific circuits and clusters can be tested.
The program creation of modern ICT systems is done by program generators, which generate test programs and wire-lists from the CAD-data, as far as standard sequences are concern and all components are included in the test library.

Inspection process:

• Contact test between test probe and test points
• Short circuit test - every node against every other node
• Test of all passive components without power
• Test of all active components with power

optional / additional

• Cluster test
• Funczional test
• Boundary Scan
• On Board Programming

Especially with highly complex PCBs the necessity of economic testability is most important, however esecially with those PCBs the access to the test points is most difficult due to high packing density. The requirements concerning the testability of PCBs devide into requirments on the functionality, construction, design and economics.

Some requirements on the testability contradict other requirements, in such cases development and production have to find compromises to achieve the optimal solution for the final product.

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