IPC International Community magazine an association member publication
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108 I-CONNECT007 MAGAZINE I MAY 2026 Benefits of Non-conductive Via Fill Primarily used to prevent solder wicking into vias, NCVF is the process of filling drilled holes with a specialized, non-con- ductive, low-shrinkage epoxy. Boards can have a higher component density because manufacturers use a technique called via- in-pad, plated over (VIPPO). This involves placing a via used to conduct signals between layers into the same real estate as a surface mount pad. VIPPO eliminates the need to route a trace from the compo- nent lead to a via nearby, provides a nice flat pad for assembly, and prevents solder from wicking through the via and weaken- ing the solder joint. The epoxy inside the holes makes the vias more reliable by limiting expansion during heat exposure. It enhances me- chanical strength, prevents solder wicking into vias, and enables via-in-pad technol- ogy. By filling voids with epoxy, vias are sealed and protected from contaminants. NCVF creates superior structural integrity against stress fractures compared to con- ductive fills and offers a better coefficient of thermal expansion (CTE) match with the surrounding laminate. Submitting a Quote: Manufacturer Capability and Process What do designers need to know? First, can the manufacturer accommodate your needs if you call out NCVF for a design with smaller pitch components? Manu- facturers often publish specs that inform designers of their capabilities, making it easier to assess them before submitting a quote. If a manufacturer does not make it clear, contact them directly to confirm they have experience with NCVF. Manufacturers unable to meet design requirements in- house may still provide a quote, either to engineer NCVF capability on the fly or to farm out production to a subcontractor. Breaking down the NCVF process If you've had a chance to read my columns or my book about designing for the reality of PCB manufacturing, you know I think it's important for designers to have a good working knowledge of each stage of the manufacturing process. This knowledge can be quite useful both during design and when it is time to create a quote request for your manufacturer. Following is a high-level breakdown of the NCVF process: 1. Drill the holes that require via filling. 2. Clean the holes to remove any debris present from the drilling. 3. Plate electroless copper across the entire panel and inside the holes to provide connectivity within the holes for electroplating. 4. Electroplate ~0.5 mils of copper across the panel and into the holes. 5. Laminate photoresist and image for button plating. This exposes just the holes and a little more of a pad on the surface. 6. Button plate. Plate another ~0.5 mils of copper into the holes. Remove the resist. 7. Planarize the buttons off the surface of the panels. 8. Using vacuum filling or screen printing, force non-conductive epoxy into the via holes. 9. Thermal cure the epoxy. 10. Sand the surface of the panels to remove any via fill epoxy and copper buttons on the surface. This surface planarization restores a flat copper surface. 11. Parts from here are returned to drill to have the rest of the holes drilled and panels follow standard manufacturing process. C O N N ECT T H E D OTS