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Dack: From a design standpoint, can we expect to get answers for the application of these circuits and what to watch out for? As a designer, I’m very familiar with the rolled annealed copper that’s commonly used in flexible circuits. But I have a feeling that additive copper is not going to end up as rolled annealed and instead will be a crystalline structure. Are there mechanical ramifications to this? Will the conductive paths be more brittle and delicate?
Dunn: The keynote presentation by Rich Brooks, senior engineering manager at Jabil Circuit Inc., will include some of the additive applications that they have been involved with over the recent years.
Dack: At first, additive processing was often perceived as something mainly for HDI and the super high-tech end. But it sounds like it’s being used for all sorts of applications—not just for the cutting edge.
Dunn: It definitely has a role with HDI technology. It can help solve a couple of things, such as working with a 12-layered design with three lamination cycles; that’s expensive because each of those lamination cycles comes with yield loss at extra costs. And it also hurts the lead time when you need to expedite product, so that’s a challenge and a constraint. Instead, if you can bring in this additive process, or a semi-additive process, and replace specific layers in a stackup, it doesn’t have to be the entire circuit done that way; you can have some layers be with the additive process, with some being etched when they have larger features, and then you can integrate those together.
In one customer application, we went from 12 layers to eight layers, which cut the lamination cycles from three to one; that’s a significant change in the way that we look at designs and how we can process things. Beyond HDI, I also see single-sided or double-sided circuit applications benefiting from these very fine feature sizes. If you think of something like a neuro-probe application or something that’s going to be bonded to the tip of a catheter, you’ll realize that additive has new applications on its own and independent of HDI.
Dack: You mentioned semi-additive a couple of times. What’s the difference between additive and semi-additive? Is it combining a couple of processes? What do you mean by semi-additive?
Dunn: That’s a good question, and I probably use those interchangeably when I shouldn’t. In general, we’re looking at additive electronics: the additive, semi-additive process, and modified semi-additive processes all fall under that umbrella term. The additive process would be just fully additive in that you’re not starting with the seed layer of copper. You may start with a seed layer of a catalyst, image the catalyst, and then build the copper up from there; that can be a little limited in terms of how tall and wide your circuitry can be with that, but it certainly has its place. Down in the five-micron range is where we would see that technology come into play.
When we have slightly larger traces—such as 17, 25, or 50 microns—then either the semi-additive or modified semi-additive processes come into play, which both start with that seed layer of copper. Semi-additive tends to start with it as chemically applied, and modified semi-additive typically starts as copper-film based laminate, and it’s slightly thicker in the electroless seed layer.
Dack: It took me by surprise when you mentioned additive because I thought it required a seed layer of copper.
Dunn: There are a lot of options, which is exciting, and that’s one of the things that we’re looking forward to hearing about at the conference. We are going to kick off the conference with a keynote speaker from Jabil who we’re very excited to hear from, as I mentioned earlier. Then, we’re going to hear from different people who currently have a need for this technology, including NextFlex, Crane, and Lockheed Martin. They will explain the need that they see in the market. We’ll also have presenters who talk about different options that are going to be available to help fill the gap.
After we take a break, we’ll move on to some of the practical applications. How are these technologies being applied in low- to medium-volume production domestically right now? And what is planned for the future? One piece that is going to be very interesting for me is our very interactive panel discussion. All of our presenters and users of the technology will come up and sit on the panel, and we’re going to have case studies. Then, we’re going to take a bunch of questions from the audience. You will have a full range of technologies represented that, as an attendee, you can ask questions about.
Dack: That sounds really comprehensive. And since it’s in San Jose, it’s easy to fly in, fly out, and get all of the information one would need.
Dunn: And for those who are interested, it is being held in the same location as the International Wafer-Level Packaging Conference, which is taking place the three days before our event.
Dack: I see Lenora Clark from MacDermid Alpha Electronics Solutions is also involved with this conference. Tell me about that.
Dunn: I was talking with Tanya Martin from SMTA about new technologies out in the market. There was a lot of interest and questions being asked at the SMTA level, and I was being asked similar questions as someone working in the PCB industry. We both said, “I think there could be a need here for a conference and some new information for people to start looking at.” At that point, she introduced me to Lenora, who had been fielding similar questions and we’ve been working on the conference together ever since.
Dack: This is going to be interesting. I think the industry is really looking forward to hearing about the ideas discussed and the outcome of this event. Thank you for sharing.
Dunn: You’re welcome. This will be fun because I work with one part of the semi-additive process, but I’m excited to hear about all of the other options too.