Design and Manufacturing Perspectives from DISH Technology’s Les Beller

Estimated reading time: 23 minutes

Matties: For designers, having to be responsible for signal integrity is fairly new to them, right?

Beller: Yes and no. It is just more important than ever before. Integration has resolved the volume of the issues, but now there are more sub-systems integrated within one board, making for more critical items to track. In years past, you might have one or two boards to focus on at one time, before moving to the next critical pair of layouts in the rack. The engineer took on all of the SI functions during the layout and after. Now, multiple subsystems are included on one mainboard so, in effect, we actually complicated the overall integrity of the system. Noise and lower signal levels have just killed what overhead I thought my system had. Now the designer experience just climbed two notches at least. At least the tools have improved parallel of the design complexity, so we can track it a bit easier.

One challenge we have from time to time is that we may have three or four different 100-ohm pairs on the board. All need to be differential 100 ohms, but the different circuit engineers will insist on not standardizing their structures with other engineers in the interest of time. The average engineer, if there is such a beast, may think this is a “don’t-care” issue, but we have just tripled the amount of IPQC (in-process quality control) impedance inspections for the supplier—don’t forget all of the impedance modeling and tuning error opportunities. First thing they will ditch if they get a chance are these extra checks! This is what I believe is the responsibility of the designer today: realizing opportunities to improve the manufacturability and therefor the quality and yield of the product, and just simply raising your hand.

Matties: I keep hearing that there's not a lot of communication between designers and fabricators. How important is it for designers to really understand the manufacturing process?

Beller: Let me state it this way. I would always recommend that a PCB designer spend some time in a board shop on the front end and some time on the floor. It's important that the person who’s purchasing the boards and the people that checking the quality of the boards know the capability of the supplier, but also know the struggles that the suppliers have meeting the requirements (i.e., using more standardized materials, using the laminate capability data back into modeling, and knowing the difference between first, second and third-order challenges). I’ve personally learned that it's amazing to go in and see the challenges the board shop has trying to meet your specs. Understanding that is always going to make somebody's quality-of-job much better. It’s equally as critical with the engineering side as it is with the supplier side, back to the person who is purchasing the board!

Matties: When somebody is purchasing a board or hiring a designer, what sort of questions should they be asking?

Beller: If I was hiring designers right now, that would be one of my first things I'd be picking at them about. Explain to me some of these terms. What do you know about this component? What do you know about that laminate? What kind of problems am I going to have if I don't specify a low-loss material when I'm trying to control my traces in a factory and what are the variabilities? What's going to happen if the supplier goes with high resin and changes the laminate or changes the prepreg on me in the middle of the game to save cost? What are the challenges if I specify too many impedances on too many different layers? I would really want my designer to have that experience because the way our industry is going, we’re going to have such higher frequencies. Back in the day, a stubbing via was no problem. Now people are back-drilling to reduce the number of stubs. Five gigahertz? Not a problem, but in the next couple years, people are commonly going to be getting up to 25 gigahertz and even higher for some applications. That requires designers at the top of their game.

As far as purchasing a board: Audit the factory and utilize surprise audits when convenient. Use references or some experience basis as well as cost to select the supplier. Get references from current customers and ask about the quality. Be careful about just buying boards from whom your contract manufacturer selects. The CM is not closely tied to the performance of the supplier as much as cost benefits. Make sure your CM is re-auditing suppliers at some reasonable frequency. Stay involved with quality reports and don’t be afraid to throw in some of you own requirements for monitoring ongoing PCB quality data. Keep two suppliers if you can, so they can bid against each other.

Matties: One of the things that we see in North America is an aging design community. My understanding is that electrical engineers will be doing circuit design as well. It's not just going to be a guy who buys a tool and starts designing, for the very reasons you've just described.

Beller: I think that's the aging population we talked about this a few years ago too. We’re part of the aging population now. It's going to be an issue if the new younger designers coming in don't have good direction, or don’t accept the training by the experienced designers. The high-speed experts, the impedance guys, the RF gals, the materials and process people as well as many other tremendously talented individuals who have a lot of experience...we need to find a better way to get those experiences down to the younger designers. Through shows, online training, or in the classroom? These days, there are some specific training rules that work with the younger professionals. We need to focus there as an industry.

Matties: If we go with that tribal knowledge, are we just passing on the old when what we really need to be thinking about is the new?

Beller: I think you need to know how to grow a rose before you can start plucking the petals to make it look beautiful, right? I think that there needs to be an availability of information. I don't know if “joint venture” is the right word between old and new, but I think it's a merging that will do both. To support your concern, there does tend to still be the mature part of the workforce, and I've caught myself saying this as well. It's like, “Well, we've never done it that way before.” Well, that's not always the right answer; in fact, rarely is it the right answer. I believe it's a mixture of old and new because there is a lot of information that we've learned over the last 20 years that's critical. How do you get that information downloaded to a millennial generation of quick-to-move, quick-to-learn, download-me-something, e-taught designers these days? I really think that products like the designer's guides that are coming out, short reads, are very good on-the-move training info and just good information. I personally print out or forward articles to my phone for when I have free time or for when I feel my attention is better to read and learn.

Matties: What about the tools themselves? Are they evolving to the point where you think that there's lessons learned just from the tools? For example, all the automation features coming in and design rule checks.

Page 2 of 4

• < Previous Page
• Next Page >