Reliability Monitoring in Drilling Electronic Circuit Boards

The purpose of the current study is to provide a monitoring scheme for evaluating the reliability of drilling of electronic circuit board (ECB) made of FR4 composite materials. The ECB is a laminated mechanical structure. Delamination often occurs at the hole exit during drilling. The resulted delamination deteriorates the long-term performance of the ECB when subject to mechanical and/or thermal loading. Acoustic emission can monitor the extent of this damage. A linear relationship exists between the size of delamination and the energy level of emitted signal when the proposed signal processing technique is used. The results contribute to higher quality ECB’s and can be applied in the manufacturing stage in an automated manner.

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Thermal cycling: impact on bentonite permeability

Mineralogical Magazine ◽

10.1180/minmag.2015.079.6.29 ◽

2015 ◽

Vol 79 (6) ◽

pp. 1543-1550 ◽

Cited By ~ 2

Author(s):

S. G. Zihms ◽

J. F. Harrington

Keyword(s):

Boundary Condition ◽

Thermal Loading ◽

Mechanical Responses ◽

Swelling Capacity ◽

Water Viscosity ◽

Set Up ◽

Long Term Performance ◽

Host Rocks ◽

Term Performance

AbstractDue to its favourable properties, in particular, low permeability and swelling capacity, bentonite has been favoured as an engineered-barrier and backfill material for the geological storage of radioactive waste. To ensure its safe long-term performance it is important to understand any changes in these properties when the material is subject to heat-emitting waste. As such, this study investigates the hydraulic response of bentonite under multi-step thermal loading subject to a constant-volume boundary condition, to represent a barrier system used in a crystalline or other hard-rock host rock. The experimental set up allows continuous measurement of the hydraulic and mechanical responses during each phase of the thermal cycle. After the initial hydration of the bentonite, the temperature was raised in 20°C increments from 20 to 80°C followed by a final step to reach 120°C. Each temperature was held constant for at least 7–10 days to allow the hydraulic transients to equilibrate. The data suggest that the permeability of bentonite appears to be sensitive to changes in temperature which may extend beyond those explained by simple changes in water viscosity. However, permeability may be boundary-condition dependent and this should be considered when designing experiments or applying these results to other repository host rocks. Either way, the magnitude of the change in permeability observed in this study is minor and its impact on the hydraulic performance of the barrier is negligible.

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