Issue link: https://iconnect007.uberflip.com/i/1114420
MAY 2019 I DESIGN007 MAGAZINE 13 McCurdy: The manufacturer can output at the start of the job what their capabilities matrix are. When any designer approaches a part, they're going to look at the densest BGA on the board first, the highest pin-count device, and what the pitch and feature size is. That tells them what they need to use for mini - mum features to pin escape and sets up a whole chain reaction of design rules for the solvability. Carbone: To your point of the designer's tri- angle, I would look at the technology and my highest speed first. Is back-drilling allowed? How many layers am I going to need to exit that BGA? In the end, my dielectric may be so thin that I have 3.25-mil lines because I have a 28-layer card and I can only have .102" to do it in. Now, I have to go back to the manufac- turer and customer and say, "This is the box you put me in. Can this be fabricated? What are the yields on this, and what can we do to mitigate loss?" Barry Matties: Do designers typically know who's going to be manufacturing the board when they set out to design the board, or does that happens post-design? Creeden: That's a great question, and it gives as many answers as there are designers out there. But as someone who has done some public speaking on this subject, the design - er should know to seek that information right upfront. And if you do not have it, you're just doing a small run or a debug board, for exam- ple. Or your procurement people don't want to tell you who they're building with, so you have to design for the solvability portion of the triangle, such as what do you need to pin escape. Matties: We were talking to some suppliers yes- terday about materials and how it affects the design of PCB boards and base material lami- nate, and they indicated that a designer will come to a fabricator, and the fabricator will say, "This is the material that we use." Then, the designer is pretty much locked into that. Creeden: That's very true, and I work a lot with Insulectro who try to bring all of the materials to the fabricators out there. Material science is becoming much more integrated into high- speed design. It has to because the material is where the electromagnetic field exists. You must involve them at the beginning, and if the fabricator is making those decisions, you have to ask the electrical engineer or understand the performance requirements. Shaughnessy: Rich, you come from a manu- facturing background. What are some of the things when you are setting up design rules that you look for? Rich Kluever: We're unique in the sense that we listen to ques- tions about their suppli- er base and who their fabricator is going to be. We're in the middle where we take require - ments from a lot of dif- ferent customers and engineers and funnel them through to various suppliers. We don't have a single path of where we always use the same suppliers or rules. I have my rules set to point me to things and let me make deci- sions. Again, we don't always know where ev- erything's going, so we try to use the indus- try standard. We're constantly updating our knowledge base with the feedback we receive from some suppliers on things that are good and things that aren't. Matties: What you're describing comes down to designer knowledge and expertise. What ad- vice would you give to a new designer? Kluever: Ask a lot of questions and work with us; a lot of our designers develop this experi- ence. In the Valor group, we act as gatekeep- ers. We're not going to let you send some- thing out that isn't manufacturable. It's a mat- ter of building that knowledge base by receiv- ing feedback and understanding where you Rich Kluever