Tips for Designing in—and Escaping From—the Vacuum

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For decades, fabricators and PCB design instructors have preached a steady gospel: “Communicate with your manufacturer early and often.” But many designers find themselves working with no idea who will be fabricating or assembling the board, not to mention dealing with the usual missing data, such as impedance requirements. 

We asked Monsoon Solutions VP of Engineering Jen Kolar if she had any thoughts on “designing in a vacuum,” and her response was, “Absolutely!” In this wide-ranging discussion, Jen and Senior PCB Engineer and Director of Designer Development Cory Grunwald share some tips and techniques for designing PCBs in a vacuum, and a few methods for getting out of the Hoover’s dust bag. 

As Cory points out, “In the end, the communication is going to happen anyway. It’s just a matter of whether it happens at the end or in the beginning.”

Barry Matties: For years, we’ve heard fabricators and design instructors recommend that designers communicate with their manufacturers, and as early in the design process as possible. However, we are often told that the PCB designer does not know who the fabricator is going to be when they embark on the design. As a design service, how do you approach that?

Jen_Kolar.jpgJen Kolar: That can be one of the big tricks when we’re working with a lot of different customers. If we’re managing the fabrication, then that’s easy. Many of our customers, however, want to be that interface. They want to be the one who passes the data back and forth, and thus things get lost in translation, and that can add a lot of time. We’ve found that can be a real barrier if the designer isn’t able to directly talk to the manufacturer, even if we’re trying to. Our best practice is that our designers always verify information with the fab manager in advance.

Andy Shaughnessy: Everyone talks about DFM and the need for communication, but in the end, there’s almost no communication with the fabricator because they don’t know where the board will be built. So, instead of telling designers to talk to your manufacturer, maybe we should just embrace reality and call it “designing in a vacuum?”

Cory_Grunwald_250.jpgCory Grunwald: If I’m working with a customer and I don’t know which fab shop I’m going to, I must make a lot of assumptions. I must work over what I expect a minimum trace and space or minimum via sizes will be. I’ll start with a capability sheet from a known supplier that we’ll go through. But then I must add a little bit to what I expect for those tolerances, because I don’t know if they’re going to a shop that can do 3-mil trace and space, or if a shop has to go to 5 mils.

Matties: When you’re designing like that, what’s the downside?

Grunwald: The downside is you can’t be on the cutting edge. You can’t be working on the smallest parts and the thinnest traces and spaces because you don’t know who it’s going to and who can handle it.

Matties: But is the design that you’re allowing some tolerance for still a successful design?

Grunwald: Yes. It can be a successful design, but as you know, projects are getting smaller and faster, and those requirements usually require a top-end board shop. Without talking to your shop directly, you can’t assume that you’re going to a place that can do it.

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


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