Issue link: https://iconnect007.uberflip.com/i/1276973
70 DESIGN007 MAGAZINE I AUGUST 2020 form. We screen the design to make sure that it will be acceptable to our bare board manufacturer so that the line widths and spacings are amenable and relative to the copper thickness. We look for stackup issues and cop- per topology on each layer. Then, the land patterns will be audited against the component BOM for feasibility. Each component on the BOM is specified in the X and Y dimensions from the datasheet, as well as the Z direction, so that component footprint topology on the bare board can be audited for solder joint perfection. Johnson: This sounds like an intensely manual process. Dack: If done manually, it would be an inten- sive process. But today's collaborative layout and DFM review software solutions include links to component data. We link to the component databases through component sourcing from the large supply chains like Arrow, Digi-Key, Mouser, and others. They are directly linked so that the layouts are designed with instant component datasheet access and 3D step data, simultaneously, within the DFM review process. This concur- rent process allows data to be fed into the auditing portion of the software to check for any showstoppers. Johnson: You're suggesting that these checks can be done at two different stages. One, as a final check by the designer before the design is released to manufacturing and the other by the manufacturing engineers before the mate- rials are ordered and sent to the manufactur- ing floors for volume processing. Dack: These are checks that should be done by the designer before the design ever leaves the originator—our customer—and then again done as an incoming inspection review or design or DFM audit by the EMS provider. Designers also need to learn from some of the important steps taken by the manufactur- ers to ensure quality. Tour a bare board manu- facturing shop or an EMS provider's assembly shop, and designers would see that every step is measured for compliance after completion. Data is collected, and adjustments are made. The design community continues to need to realize this and implement a design process that checks for acceptability after every step of their design process. This includes check- ing in with other process stakeholders and setting up a database of design constraints to match those of the manufacturers. It's very important that this myriad of design rules be set up to match the capability of the supplier doing the work. Johnson: Ultimately, the source information comes from the designer and is then made available to you. Your check on incoming designs should deliver a clean result with zero issues regarding footprint sizing and Z-axis for the component. Dack: This only happens when there is out- standing communication between the designer and manufacturer before design release. Ide- ally, the designer is in communication with the manufacturing stakeholder well before the design is released to set up the design con- straints in the layout. Often, we receive designs that have passed with flying colors all of the DRC checks in the layout database, which were set up for manufacturing at a prototype shop that has extremely accurate processes and machinery and access to specialized materials. However, when this board is sent to an EMS provider to be built in volume, this is where we see the designs fall out because our offshore manufac- turing stakeholders use different machinery. Or they don't have access to the same materi- als that the prototype supplier has. As an EMS provider, we use a different set of design rule check criteria than the designer did unless we were given the opportunity to communicate throughout the design cycle. Kelly Dack