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Design of fixtures for test and manufacturing
 
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Our fixtures are generally built from a part locating base of machined delrin or baltic birch plywood, depending on the application and what will be attached to them. Other materials can be used as necessary. In cases where exceptional durability and/or significant amounts of concealed wiring are required, aluminum plate, channel and square/rectangular tubing may be used. Test fixtures are preferably mounted on a steel chassis box with electrical connector access or connector-specific openings machined into the box. Clamping and pre-tensioning is accomplished with components including spring steel fingers, spring pins and toggle clamps.

If pogo (miniature spring-loaded) pins are being used for contact points on test fixtures, they are held in dedicated receptacles made by the same manufacturer and we strongly recommend designing a pc board to mate with the pogo receptacles (CAD information is provided) and to hold any I/O connectors. Loose point-to-point wiring can be used but such a fixture will be much less durable and probe replacement is more difficult. If at all possible, center spacing for probe points should not be less than .039" (1mm).

Fixture cost and lead time are a function of fixture complexity and durability requirements; fixtures intended for lab use need less durability features than fixtures intended for use by skilled workers on the production floor, which in turn require less durability than fixtures intended to be used with overseas manufacturing. For overseas use we recommend easily replaced probe subassemblies designed for service by semi-skilled personnel.

 
Image of test FixtureImage of probe and locating block for test fixture
CAD Images Of A Typical Test Fixture - The left image shows a typical test fixture with the chassis box, clamping block and midplate shown transparent. The right image shows the probe and locating block for the test fixture, with the midplate shown transparent for easier viewing of the probes. The midplate protects the probes and serves as a resting surface for the device under test. The corner pins engage corner holes in the device under test (other methods are used for boards or assemblies without suitable holes) and serve as primary locating features.
 
 
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