IPC International Community magazine an association member publication
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12 I-CONNECT007 MAGAZINE I MAY 2026 T his month, I'm taking another look at addi- tive manufacturing. What does mSAP, SAP, and additive metallizing (plating) look like in today's advanced PCB fabrication? I must confess I don't have a lot of insight, as my whole career has been devoted to removing copper from panel sur- faces in even and controlled ways, and not to put- ting copper back on the panel. However, at some point in the additive process, especially in additive plating, copper must be removed from between the conducting surfaces to complete the circuits. Here, I can address some of the consequences of additive metallizing on subsequent etching steps. Traditional additive metallization, or pattern plat- ing, has been the primary way to get taller conduc- tor heights for higher current capacities and less heat generation than is possible with just subtrac- tive etching. The traditional process starts with a thin laminated foil (one-quarter or one-eighth ounce), then laminate and develop a plating resist with the desired circuit layout. The panel is put in an electroplating bath, and copper is plated until the desired circuit height is reached, followed by a solder or tin coating to serve as an etch resist. The base foil is etched with an alkaline etchant, leaving behind the desired circuit design. A more recent technique is to sputter or flash plate an even thinner base copper, usually 2 to 4 microns, and electroplate the circuit lines to the desired thickness, but with no tin or solder. Then the panel goes through a flash etch in an acid etchant (usually cupric) at such a speed that etches away the base copper while having a minimal ef- fect on the plated circuit lines. Obviously, before the base copper can be etched away, the plating resist must be removed, and this is where problems can arise. Getting even plating over a large format panel, with several of these large format panels on a vertical flight bar, is difficult at best. It is not uncommon for areas of the BY D O N BA L L , C H E M C U T The Consequences of Additive Metallizing on Etching Steps T H E C H E M I CA L C O N N ECT I O N