Issue link: https://iconnect007.uberflip.com/i/1369942
60 DESIGN007 MAGAZINE I MAY 2021 our findings in a team meeting and discussed how we could improve further. Each week we received a copy of the DFM review data from our PCB assembly group. We compared these scorecards and could see that collecting data and tracking it had instituted a cadence of accountability within our two groups. Our two groups were compelled to work together to become one. We were able to almost eliminate the DFM issues in just a short time, but it took data, com- munication, and buy-in from everyone involved. We worked for a captive shop, with every pro- cess (more or less) under our control. How would my enlightened DFM perspective serve me in a commercial manufacturing situation? A DFM Complication: Offshore Suppliers As I mentioned, I started working for an EMS company in 2015, and over the next five years my eyes were opened to new DFM challenges from PCB design customers. But this time the DFM challenges involved boards being built offshore in quantities of a million per year. I was awakened to the fact that offshore PCB suppliers have an entirely different set of DFM values, and their access to materials and pro- cesses is limited. Our offshore partners were experiencing daily frustration due to an alter- nate form of disregard for DFM. If I could establish close contact with our off- shore suppliers, as well as tour and audit their facilities, I knew I could implement my DFM plans. At these volumes, if I could convince one customer to make one DFM change to save a dollar on a PCB design, I could begin saving millions of dollars each year. All I needed was that positioning and some empowerment. A large EMS company runs much differently than a captive OEM. ere are many customers and various PCB designs. Designs are quoted and assigned to myriad PCB suppliers by a large quote team. Once a customer design is quoted and is assigned to a particular supplier, a steady list of requests to change the design or substitute materials begins to arrive from the supplier (EQs). Sometimes, to shave cost, the EQs request a simple change to an item, like changing solder mask material from matte fin- ish to glossy. is can be an easy concession. But many times, even though quoted as such, the supplier will balk at providing a full amount of finished copper per the fabrication drawing spec. Sometimes it becomes apparent that the design would be un-manufacturable anywhere in the world using standard processing. We occasionally receive a design com- posed of 3-mil lines and spacing on an outer layer with a specified base copper thickness of 1 ounce and plating requirement of a full 1 ounce. e current-carrying capacity of the outer layer power lines are calculated to carry a specified amount of current at 2 ounces with no room to modify the widths. ere are some serious DFM issues going on here. e PCB was quoted three weeks before for a certain price, which then was passed on to the cus- tomer. Who is going to tell them that we lost three weeks, the board must be re-quoted, and the price will likely increase? Sadly, at the scale and pace a large EMS com- pany moves, putting a PCB designer in close Figure 3: Example of an engineering query from an offshore supplier.