Issue link: https://iconnect007.uberflip.com/i/1475604
66 DESIGN007 MAGAZINE I AUGUST 2022 PCB Design Claustrophobia Sometimes, when our front-end packaging stakeholders seem to be working for "Team Crazy," their PCB mechanical constraints can send me in an opposite direction. Over many decades we have been watching as electronic components shrink in size. Each new genera- tion of components seems to include a smaller packaging scale which is construed to be good for shrinking products and using less mate- rial. But from an actual product design stand- point, electronic products have gone through an identity crisis with regard to packaging size. For example, all that must happen for an elec- tronic product to be rendered obsolete and discontinued is for a competitor to come out with a smaller, more tightly packaged alterna- tive. Industrial designers are kept busy sketch- ing out increasingly smaller electronic prod- ucts from the outside-in and passing on their concepts to the mechanical engineering teams. Mechanical engineers seem to only re-design their molds and choose higher performance materials to meet the industrial designer's smaller constraints while electronics packag- ing engineers and PCB designers are oen le scratching their heads trying to select available components and circuitry which can be manu- factured to fit within a new, sleek, ergonomic, and attractively small product housing. ere is a classic, ongoing challenge for elec- tronics design stakeholders today. It is com- monly attributed to EEs residing at the end of the product design cycle. Creative, responsive, industrial design and mechanical engineering stakeholders are usually well on their way to offering their deliverables well before compo- nents can be found and the electronic assem- bly bill of materials is even finalized. Electron- ics packaging stakeholders are oen faced with pressure to cram their circuitry onto less-than- ideal PCB real estate, robbing process effi- ciency from every other electronics manufac- turing stakeholder involved. As a PCB design stakeholder, I can't tell you how many times I've created a PCB outline per mechanical specification only to discover there is not enough space for the component footprints to fit on the board. is condition is typically resolved, however, by a quick dis- cussion with the project team that will need to review its whole design process and either make the PCB larger or continue to find smaller parts. We usually won't see them back for an average of about two weeks, which frees us up to work on other, more practically dense PCB layouts. ere is a more difficult condi- tion, however, occurring from time-to-time when the parts within a design layout hap- pen to just barely fit within a specified PCB outline. is PCB design condition is on the hairy edge of "doable." e parts fit, but will most certainly result in an extremely dense layout with compromised design rules. While this condition is a welcome challenge to any emerging PCB design layout engineer, designs exhibiting extreme density cause me to self- diagnose as claustrophobic. It's not because I don't like a challenge. I'll work overnight as hard as any PCB designer to push and shove Figure 2: The "panel burner" consisted of a lot of material, very low design density, and was a very expensive-to-manufacture bare PCB.