Make the intended interconnect conductive
Drilled dielectric surfaces are not automatically conductive. PCB metallization prepares those surfaces so that a continuous interconnect can be produced. Electroless copper is one route to depositing an initial conductive layer; direct-metallization systems use other approaches. The selected route must be qualified for the board materials and hole geometry.
Electrolytic copper deposition uses electrical current to build copper on conductive surfaces. Its role differs from the initial preparation step. Through-hole coverage, microvia filling and outer-layer buildup can impose different process demands even on the same board.
Specify the finished requirement
State the required copper in the finished hole or via and on relevant outer conductors, with the acceptance basis and measurement locations. Starting foil weight alone does not define plated thickness. Distinguish nominal, minimum and locally measured values when reviewing a quotation.
Hole size, board thickness, via topology and copper distribution affect the difficulty of obtaining the required result. Uneven distribution can complicate plating uniformity. Allow the fabricator to review panel construction and any proposed balancing copper while protecting functional clearances and impedance structures.
Ask about process control, not a machine label
Vertical conveyor, hoist and horizontal systems describe equipment arrangements. Their names do not prove that a particular board will meet its requirements. Ask for evidence relevant to the proposed construction, such as coverage, thickness distribution and qualification of difficult features.
Acid copper electroplating is a process family, not a transferable production recipe. Chemistry, circulation, current conditions, cleaning and monitoring belong to the qualified manufacturing process. Purchase requirements should define the result and evidence instead of prescribing an unvalidated bath formula.
Keep copper plating separate from final finish
Nickel, gold, silver, tin and other surface treatments can serve different protective, soldering or contact functions. An immersion finish is not a substitute for the structural copper required in a plated hole. Select each finish for the relevant function and assembly sequence.
Agree inspection, microsection sampling and electrical acceptance before manufacture. A passing continuity check cannot reveal every plating weakness, while a local section cannot represent every hole without a sampling rationale. Supply the stackup, finished holes, via spans, copper requirements and reliability expectations for review.