Plating Specification
Electrodeposited metal migration refers to the extension of copper foil into the barrel of a drilled hole during the electrolytic deposition process. This wrap copper ensures a continuous metallic transition from the internal planes to the surface pads through the hole wall. Geometric standards dictate a minimum thickness for this feature to maintain electrical integrity under thermal stress.
The requirement prevents structural weakness at the junction of the outer layer and the hole wall where expansion forces concentrate during soldering.
Manufacturing Control
Drill entry and exit conditions affect how uniform the subsequent plating appears on the laminate surface. Proper adjustment of plating bath chemistry prevents excessive growth that might bridge adjacent conductors. Secondary inspections verify that the thickness meets minimum values after the outer layer etching completes.
Operators verify the integrity of the metallic bond by examining cross sections of the board under high magnification. This assessment confirms that the transition area remains free of cracks or gaps after the completion of thermal cycling tests.
Structural Performance
Reliability in high current applications depends upon the consistent geometry of this interconnect feature. Uniformity across the board prevents localized resistance heating when the assembly operates under heavy load. A stable transition facilitates robust solder fillet formation during the assembly phase.
Failure to achieve the specified geometry results in intermittent signal loss when thermal expansion stresses the connection points. High reliability standards require strict adherence to these dimensions to preserve the signal path throughout the lifetime of the electronic assembly.
