Issue link: https://iconnect007.uberflip.com/i/1533085
20 DESIGN007 MAGAZINE I MARCH 2025 How Thick is Half- ounce Copper? Or 1-ounce or 2-ounce copper, for that matter? Ask your typical PCB designer, "How thick is 1-ounce copper?" More than likely, the answer will be 0.0014". If I turn around and ask a fabri- cator the same question, you'd probably hear 0.0012". is has to do with starting copper weight vs. finished copper weight, not unlike the drill size vs. hole size snafu. Remember: Copper weight is defined as the weight (in ounces) of copper present in one square foot of area. is parameter indicates the overall thickness of copper on that layer. It's the resulting thickness when 1 ounce of copper is pressed flat and spread evenly over an area of one square foot. So, with that information, we should be able to come up with a conversion factor. e prob- lem is that no one agrees on a measurable thick- ness for 1 ounce of copper. I searched online for a measurable thickness for 1 ounce of copper, and I found one site that states that 1 ounce of copper equals 0.00137" thickness. I know for a fact that two of the major CAD design systems use a different number when converting ounces to a measurable thickness. So, when specifying copper weight, make sure to specify a finished weight for the plated layers. Print notes should be clear when discussing copper weight as to the finished requirements. What Exactly Is a Panel? If I ask a contract manufacturer this ques- tion, he will respond with what we would call an assembly panel. On the le side of Figure 2 is a 6-up assembly panel with tooling holes, web routes, and fiducials. But if I ask a fabricator, they would indicate an assembly panel stepped up as many times as possible in a fabrication panel. On the right side of Figure 2, you have four assembly panels stepped into a fabrication panel. Last but not least, if I ask a designer, I must be very clear which panel I'm talking about. Pricing is decided by how many assembly pan- els you can fit in a fabrication panel. So, any change in the assembly panel size can affect the fabrication panel and, therefore, the pricing. It's All Relative Many times, a term's definition is relative to where you are in the production process. What do all these terms mean to you? • Plug • Cap • Tent • Encroach I have a colleague who just sends a picture like Figure 3 and says, "Circle what you want." at certainly takes the guesswork out. As the saying goes, "A picture is worth a thousand words." And it might save you from having your job put on hold. Impedance: Controlled or Designed? When specifying impedance requirements, you have a couple of choices: 1. Controlled impedance: Impedance val- ues are dialed into the design, and line widths and dielectrics are modified to achieve the impedance goals. Impedance is measured at the fab shop to verify the requirements are met. Figure 2: An assembly panel (left), and a fab panel (right). HyperLynx). Ray Fugitt