Double Sided Plated Through Hole (D/S PTH) is a phrase that was coined at a time when PTH Printed Circuit Boards (PCBs) were in their infancy and D/S conventional were the norm. Initially, many were suspicious of the new technology and had to be convinced that PTH was at least as reliable as pinning through and soldering to pads either side of vias on the D/S conventional. Problems with PTH were common. Open circuits due to lack of continuity of plating through vias was not unusual, plus barrel cracking when using pyrophosphate copper out of balance added fuel to the debate concerning the reliability of PTH.
Nowadays, of course, barrel cracking is hardly ever encountered. Acid coppers are very resistant to such faults, but too much of the wrong additive (with or without contamination) has certainly been known to replicate the problem. Voids, partial voids, and hairline connections have yet to be completely eliminated to ensure reliable continuity through PTH vias. Bare Board Test (BBT) doesn’t guarantee quality plated through hole, because the test does not eliminate partial voids and hairline connections. Both of these faults can and do cause failures in the field.
At Elite Circuits Ltd, the Company retains panel plating following the initial process of creating through hole conductivity to permit a visual inspection to confirm the absence of voids and/or partial voids before continuing through the rest of the processing sequences. This isn’t the entire answer, of course, but it certainly lays the best foundation to the production of quality circuits.