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Universal Synaptics Intermittence
INTERMITTENCE AND IT'S LABELS
| Throughout the electronics industry,
commercial aviation
and the Department Defense, intermittent defects are a major cause of
failure
in electronics and mechanical systems. They are often labeled using
various
acronyms that erroneously describe the problem. These labels imply that
no fault or defect exists, that a mistake was made, or it somehow
magically
fixed itself. Applying these labels often becomes the repair, while
tracking
the number of times these labels have been applied has become the
solution.
If the problem is labeled correctly as "Intermittent" the existence of a problem is acknowledged. An "intermittent", label explains why the test equipment can not identify the problem and enables the technician to focus on the real solution. |
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| Commercial airlines and military repair depots are reporting a 40% - 60% No-Fault Found or intermittent defect rate in their avionics systems. In addition, a large number of reported engine and mechanical failures are due to intermittent electrical connections in circuits which sense and control other operation. The cost of these defects is enormous when maintenance, spares, system replacements and operational readiness is considered. |
| Although this problem is not new, what is bringing this issue to the forefront is a change in the ratio between hard and intermittent failures. Component reliability has improved resulting in fewer hard failures, while the number of circuit interconnections prone to intermittence has increased. This change is also affected by the widespread use of complex digital avionics which is more susceptible to intermittence. |
| Testing philosophies, equipment and procedures have focused on hard failures and defective components while neglecting the more difficult to detect, randomly occurring intermittent failures. |
| Connection intermittents as short as a few nanoseconds can cause problems. They are a result of temporary changes in continuity, caused by worn or oxidized connector pins, loose crimps, broken or shorting wires, damaged circuit board traces, loose(cold) solder joints and noisy components. Connection Intermittents increase over a product's life, based on the amount of wear encountered, and are often triggered by stress factors such as vibration and heat in the system's operating environment. They are nearly impossible to detect using continuity testers, ATE or TDR. |  |
INTERMITTENTS CHANGE OVER TIME
| In different stages of a systems life, the
ratio and
magnitude of the three primary types of intermittent faults change;
Engineering
and Test Void problems are resolved when a product is new, while
Connection
faults increase over time due to wear, stress, and corrosion.
Most test equipment and procedures developed for new systems overlook or are unable to detect and isolate intermittent connection faults. As unrepaired, intermittent units remain and accumulate in a system, the repair and testing process disintegrates. "Shotgun Maintenance" replaces good or suspect units with intermittent units. Testing can find few problems, yet Mean Time Between Failures(MTBF), and Operational Readiness(OR) continue to fall. When these vital indicators reach critical levels, whole system or entire aircraft may have to be replaced. |
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Us
E-Mail:
info@usynaptics.com
or
Universal Synaptics Corporation
1801 West 21st Street
Ogden, Utah 84401
Tel. (801) 731-8508
Fax (801) 731-8509