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Some things are rare, good or bad, but they do happen from time to time. And, some happen so regularly, we often take them for granted if good or learn to live with them if bad. But should we? For example, you send out your design for fabrication and the CAM (computer-aided manufacturing) engineer runs a high-end design for manufacturability (DFM) analysis software. The CAM engineer sees DFM issues (almost always!). Now, there are three scenarios: the CAM engineer updates the design and informs you; the CAM engineer updates the design but forgets to inform you; or the worst case, the CAM engineer does not update the design at all thinking the issue was minor.
In the scenario that the CAM engineer informs you, you go ahead and make changes to your design and you are good, though it involves inconvenient rework. But in the scenario that the CAM engineer does not inform you, you are not good; the designs do not match, and your design has issues that you will never know. The scenario where the CAM engineer forgets to update the design needs no discussion, I suppose the loss of time and money is obvious enough.
In any case, you are either inundated with manufacturing issues in the middle of another project or your design is riddled with manufacturing issues and you are not aware; annular ring issues, copper spacing issues, differential pairs that neck down and shouldn’t, void around the via—the traces run right the edge of the cutout, plane issues—vias half in half out, and back drilling issues—spacing checks of drill hole to metal (annular ring metal remaining)—to name just a few.
So, the easiest and the most obvious thing to do is to run DFM analysis and correct any issues before sending the boards off to the fabricators. Well, you like this solution and create an internal signoff group to address any manufacturing issues (the conventional design for fabrication flow). But, are you then not spending time reworking the design late anyway? And add to that the fact that the designer is not running DFM but correcting identified problems? So, it seems this flow, which we shall call the Conventional Design for Fabrication Flow, is not the most ideal solution.
That’s why it is a good idea to perform DFM analysis early in the cycle and by the designer. It was a difficult proposition earlier, an easier said than done thing. But no more. The DesignTrue DFM feature of Allegro® PCB Editor has made it available in an easy-to-use format.
In PCB Editor, manufacturability checks are available from the software itself—you don’t need a separate software and wait till the end to identify and correct issues. The signoff phase still exists using tools such as Allegro®/OrCAD® Manufacturing Option, but with DesignTrue DFM, the iterations and the time required to produce fabrication data decreases multiple times. DesignTrue DFM identifies issues that might come up when boards are being manufactured, that is when boards are being fabricated and assembled. So, you have two main types of analyses, design for fabrication (DFF) and design for assembly (DFA). We will talk about them in detail in our upcoming posts.