Fixtureless in-circuit test
|This article does not cite any references or sources. (March 2008)|
Fixtureless in-circuit test (FICT) is a cost-effective alternative to a "bed of nails" tester for in-circuit testing of low to medium volumes of printed circuit board assemblies. It relies on a computerized optical inspection of the circuit assembly and positionable test probes. Traditional "bed of nails" testers require the manufacture of a complex mechanical fixture comprising pins inserted into holes in an acrylic plate connected to the measuring unit by wires. Some of the disadvantages of the bed of nails tester is the number of wires used will often increase the capacitance of the circuit so that values below 60 pF are difficult to measure accurately. Also, the holes in the plate do not allow pins to be placed close enough together to test fine pitch components with a lead pitch of 0.5 mm unless test pads or vias allow connection from another part of the circuit.
Typically, four to six weeks are required for the manufacture and programming of a bed of nails fixture. Fixtureless In-Circuit Test does not suffer from any of these drawbacks and, in combination with smart software, testing can be done within hours for a low complexity design and within a few days for the most complex designs.
Benefits of fixtureless in-circuit test
- Automatic optical inspection for presence of components, correct polarity, and letters or numbers on ICs.
- Value measurements on resistors, capacitors, Zener diodes and inductors.
- IC open circuit checker finds lifted legs and dry joints on ICs.
- Can test fine pitch printed circuit boards down to 0.3 mm with a repeatable accuracy of probe placement of ±0.05mm.
- Test program is rapidly prepared from printed circuit board CAD data.
- All major CAD platforms support FICT.