These days you can't read anything about electronics without hearing about the dire consequences of omitting ESD protection from your designs.
It seems this wasn't always the case. If you look at most older designs (late 90s and earlier), you hardly ever see ESD protection components on I/O ports – even when CMOS ICs are involved. Why is this?
One might assume that modern ICs are more vulnerable than older processes. I don't think there's much truth to that though. Looking at the datasheet for a typical 74HC gate, they specify a maximum HBM of 2kV. This is the same as a modern MCU or FPGA.
I could understand designs using 74LS gates omitting protection, but I also see lack of protection when 74HC or CMOS LSIs are used in older designs. And having looked at more recent datasheets for 74LS parts, even those are specified only up to 2kV HBM.
Is it just that we have a better awareness of ESD now? Or could it be that you can actually still get away without ESD protection just as they did in the 90s? Is there a minimum level of ESD robustness required by law for consumer products, that wasn't enforced in the past?
Best Answer
I can only speak from my personal view...
In the 80's, there was a thorough awareness of the need for ESD protection and handling precautions. My then-employer modernised its factory in 1987, taking ESD precautions from only in the electronics assembly areas to every assembly area. The consensus was that we were very late in the day to do so. The understanding of ESD that I see is no more stringent or widespread than then.
What has changed considerably since then are the costs of electronic components and of PCB design, manufacture and assembly. I've seen these get dramatically cheaper.
So the costs of adding extra parts, such as transorbs, TVS or input filters are much cheaper. Back then, in the commercial industry I worked in, these protection parts would be an unacceptable increase in cost. It's not just the component cost, its the price of the inventory, assembly and testing that goes with having those parts there.