Reading time ( words)
I’ve been thinking over what 2015 might look like, from my point of view at a PCB fabrication company. Let me first start out with some broad overviews of trends from 2014 that I see continuing.
1. More RF work. Whether it’s phased arrays or waveguides, ID tags or implants, it’s not just cell phones and tablets that require this technology; we’re seeing more young people gravitating towards careers in RF design and applications. From a fabrication standpoint, I see a lot more people are asking the right questions:
- How do I ensure the highest degree of positional accuracy for a given feature?
- How do I make sure a fabricator will not trim back any RF launches I may need in an effort to avoid rout burring?
By its very nature, RF is different in many ways at the fabrication level. For instance, as fabricators we may be more concerned with space or air-gap issues based on etching, but in an RF world, geometry is everything, in both metal and non-metal areas. All calculations and estimates are based on very specific metal and anti-metal geometries, and they need to be as perfect as they can be. Material substitutions can require an entire rethink of an RF design. Small variations like surface topography post-via fill /planarization can create unwanted variations as well.
This applies all the way down to little things that everyone is starting to embrace, like specifying a starting or finished copper weight on drawings and “read-me” notes. Typically, the word “weight” means a STARTING copper weight prior to final plate-up for through-hole continuity. The use of the word “finished” means copper foil AND the associated electroplated final plate-up. This needs to be clearly understood. Many times customers will run simulations and calculations based on 1 oz finish after plate. Please note: Whereas many offshore fabricators have no problem doing this, remember that IPC dictates a minimum of .8 to 1 mil in the barrels of plated copper for continuity. So, here in the U.S., even starting on quarter-ounce outers will result in 1.5 oz. finish after plate typically. If you have numerous impedances on the surface, having to redo them all because this was not considered will result in having to redo all the calculations, which takes more time. The old adage, “Time is money” is certainly true in the PCB fabrication business, especially with RF parts...
To read this column in its entirety in the January 2015 issue of The PCB Design Magazine, click here.
