Designing Additive and Semi-Additive PCBs

Estimated reading time: 1 minute

With components getting smaller and electronic devices becoming more compact, we are reaching the physical limits of the typical etched fabrication processes. To address these limits, new additive and semi-additive processes are being developed to fit into the current fabricators’ production lines without too much disruption or extra cost.

That leaves the design engineer with a few questions: Will additive and semi-additive processes really reduce layer count and sizes? Are there signal integrity and impedance advantages and disadvantages? When does it makes sense to switch to additive or semi-additive? Are my DFMs going to be any different?

Answers to these questions and many more are still being developed. However, I’ve found a few answers that I’m happy to share with you. 

First, let’s look at liquid metal ink. LMI is ultra-thin and ultra-dense, conforms to any 3D surface, works with different pure metals and their alloys (copper, gold, silver, palladium, platinum, etc.), and is non-aqueous, which enables low-cost manufacturing.

Here are some fundamentals for these very small features. Figure 1 depicts some examples of the additive processes used to create fine copper traces on a printed circuit board. One of the first things you’ll notice are the shapes of the traces: They are not trapezoidal. 

To read this entire article, which appeared in the April 2022 issue of Design007 Magazine, click here.