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88 DESIGN007 MAGAZINE I NOVEMBER 2021 processes, screen printing, wet and dry film imaging, developing and stripping, chemi- cal etching, and several others. To me, it has always been one of the most attractive aspects of PCB manufacture and what makes PCB manufacturing tirelessly interesting. What Has Changed Today, many of those same processes are still used, though they have been greatly improved in terms of machines, materials, and processes available. Still, they remain fundamentally unchanged except that the circuit features are now approaching or in some cases equal to those produced on semiconductor integrated circuits of that same era. One big difference is that back then, the substrates for early semi- conductors were 50- and 75-mm silicon wafers and today those near-same-size features are being produced on 450 x 600 mm FR-4 pan- els to make printed circuits. is has been a remarkable achievement. Much has also changed in the realm of PCB design. PCB designers of the early days were largely mechanical drasmen charged with "connecting the dots" on the schematic pro- vided by the circuit designer. Artwork was oen created by taping circuit traces and pads at one to four or more times the size of the final circuit and using a large format (near room size) cameras to "shoot down" the artwork to the size needed for contact printing the circuit image with working film. During that era, Ger- ber vector photoplotters were coming into use and light pens were mechanically driven using pre-programmed vector-driven information to create the artwork. In that early era, dou- ble sided printed circuits were most common and four-layer multilayer circuits were essen- tially state of the art, and the term "controlled impedance" was basically unheard of. Today's PCB designers smile at such simplicity. One unfortunate thing that has happened over the years is that, while semiconductors have grown in respect, appreciation, and even adulation, the PCB has too oen remained under-appreciated and undervalued. I have, over the few decades of teaching PCB seminars and workshops, likened the semiconductor to a magician or illusionist and the PCB as the stage upon which the magician/illusionist works. My simple evaluation and statement of fact in this regard is that, without a suitable stage, the potential of magic or illusion simply will not happen. e PCB and the semiconductor must work together for the show to be a success. Looking Ahead In more recent years, I have personally become ever more appreciative of the impor- tance of PCB designers and their work. ey are clearly more knowledgeable than their pre- decessors. Today, the choices they make are of the utmost importance to the end-product in terms of its functionality, performance, manu- facturability, and ultimate reliability. Today, designers must become increasingly knowl- edgeable of many different design attributes to make their designs suitable for the applica- tions intended: DFR (design for reliability), DFT (design for test), DFE (design for envi- ronment), and DFA (design for assembly) are checklists alongside perhaps the most impor- tant, which is DFM (design for manufactur- ing). Several months ago, I suggested in this column, that a better approach might be to design with manufacturing or DWM. is was arguably common practice in the early days of PCB designers of the early days were largely mechanical draftsmen charged with "connecting the dots" on the schematic provided by the circuit designer.