LIFE TESTS
To prove out the integrity of the system throughout its required life of 3,000 mating cycles, a series of mechanical, environmental, and electrical tests were devised.
The phosphor bronze contact spring was tested for fatigue by mating the connector 5,000 times, as a safety factor. Contact force was periodically measured at the minimum design deflection distance of .020 inches. (See Figure 9). The results show that 60 grams minimum is obtained, assuring adequate contact force.
Microscopic examination of the wear track on the p.c. board after 1,000 cycles showed that the wiping distance is only .030 to .040 inches. (See Figure 10). Standard edge connectors, by contrast, have wear distances which usually range from .125 to .250 inches. In addition, the short wipe distance of the rotating connector, in combination with the low normal forces and a hard gold alloy surface, permitted the contact surface to exhibit excellent durability. In Figure 11, we see that life cycling does not cause wear through the gold inlay.
As a design requirement, the average life of a cartridge was set at 300 to 500 cycles. However, to increase the severity of the testing, as a safety factor, and realizing that unequal cartridge usage would occur in actual practice, the following test sequence was performed:
ENVIRONMENTAL AND ELECTRICAL LIFE TEST SEQUENCE
a. Contact Resistance (20 Mv. at 10 Ma.)
b. 1,000 Mating Cycles
c. Contact Resistance
d. 48 Hrs. Heat and Humidity Cycling, Unmated (65°C, 95%RH)
e. Contact Resistance
f. Replace Cartridge Every 1,000 Cycles and Repeat a. thru e. Four Times for a Total of 5,000 Connector Cycles
g. Contact Resistance
Heat and humidity cycling was incorporated as an accelerated aging process to simulate consumer use and long time storage before reuse.
The results of this testing appears in Figure 12. We see that contact resistances are essentially unaffected at dry circuit levels, attesting to the acceptability of the system.
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