Issue link: https://iconnect007.uberflip.com/i/1518649
62 DESIGN007 MAGAZINE I APRIL 2024 e copper density in this design would be closer to 45%. Even Bruce would have a hard time drilling through this with a 0.012" drill bit. While peck-drilling and flip-drilling could help combat this, the design solution is the best method to resolve the issue; therefore, increase via size to at least 0.016" to 0.018" on 3+ ounce copper multilayer designs. Design/Manufacturing Methods ree of the most common design and man- ufacturing methods are etch-down, hybrid (buried heavy Cu), and plate-up. Etch-Down With its lower cost and simplified process flow, etch-down is part of the standard pro- cess used for fabricating your run-of-the-shop board. is is fine for most boards—but heavy copper PCBs are not most boards. In most boards, that trapezoid shape resulting from the uneven sidewalls will not affect current car- rying capacity; however, this is a major issue for heavy copper boards where mechanical strength and subsequent field life depend on thick, powerful traces to conduct power and transfer heat. Table 9. Figure 10: The best way to reduce drill breakage is to increase drill size.