Statistical Reliability
Statistical reliability measures the percentage of successfully formed and electrically conductive laser-drilled connections within a production lot. Calculating the copper microvia yield allows a fabrication facility to assess the stability of its plating and drilling operations. High volume production requires a consistent success rate to maintain cost efficiency and prevent excessive scrap.
Failure Mode
Discontinuities in the circuit path often stem from debris or plating voids at the base of the hole. Tracking copper microvia yield identifies when the chemistries in the electrolytic bath are losing their efficacy or when laser parameters require recalibration. Reliability engineers monitor these failures through daisy chain test coupons that represent the entire board population.
Acceptance Standard
Industrial specifications define the minimum percentage of functional vias required for a batch to move to the next stage of assembly. A stable copper microvia yield ensures that thermal stress during subsequent reflow cycles will not cause latent opens in the interconnect structure. Quality inspectors use automated optical testing and electrical resistance measurements to verify the integrity of every blind and buried connection.
Systematic data collection helps the manufacturer distinguish between random defects and process-induced systematic failures. Process improvements targeted at the desmear and seed layers typically result in a measurable rise in the final success rate.
