Hardest part of electronic design

What is the hardest part of designing a board?

No question about it, it is selecting the connectors.

Over the years I've picked few favorite MCU types I like to use. For applications needing a bit more power (as in processing power with loads of peripherals) I'd go for STM32 ARMs these days. For lesser needs, possibly some PIC24 series chip. For really low power, MSP430. I'm familiar with all of these (and few others, too) and can design a circuitry around them pretty quickly.

Familiarity is a bonus, too; I recently even had a customer calling me a bullshitter when I told him that his board was pretty much done (that is, schematics and layout) in less than 20 hours - and this included design meetings with said customer, studying some dozen exotic parts they needed and making library parts for them. But since I could base the "usual" difficult parts (MCU with parts around it, and DC/DC converters) on things I had done previously, rest was fairly straightforward, especially since board wasn't lacking space (so routing was fairly easy to do).

Whenever I have to use some unfamiliar but complex MCU, I usually have to spend maybe hour or two just reading manual and datasheets before I can even get started with it. You know, minimum necessary components, how peripherals work, or clocks and so on. More complex the part is, more time is spent just studying it. So I prefer to stay with ones I more or less know. This means that less of my and customers' time wasted there. But sometimes there is a special need that calls for some special and/or exotic MCU. Well, then I just have to quietly sigh and start reading.

I got a bit sidetracked there, but continuing. Same goes for DC/DC converters. Most of the low-power (speaking of current, less than 1 amp or so) is relatively easy. If I want really good one, I go for a Linear's devices - although they tend to be a bit more expensive. Others make nice chips too, but often quiescent current consumption is a killer - if my board will typically be using some 1mA or less on standby (which is 95% of the time - remaining time would be some 20mA on running, with occasional 300mA peak), it's out of the question for buck converter to use another 3 to 5 mA on top of that, especially in a battery-based product! .. and way too often I have to actually go and read the datasheet to find that value, since they don't really advertise it. With that kind of wasted current, no surprise, really... But still, relatively simple stuff.

Most of the remaining stuff is then either common as dirt (like chip resistors and capacitor) or something less common, but with good datasheets they're simple to use. Although there are nasty surprises there too sometimes.

But those connectors. Yeah, I know, there are literally hundreds of thousands of them, but that kinda is part of the problem. Even if you have figured basic parameters - like pin count, through hole/SMD, single wires/ribbon/other - out, there's still massive amount of options. And then you need to start picking them out by price and availability. That nice cheap connector you picked for this one-time 50-board product? Sure it's nice, available in rolls of 5000 pieces only, thank you. Hope you noticed this before ordering the boards...

In some cases it's easy, either surroundings (like existing devices) forces some type of connector or customer has his favorite already, but remaining time...

I've wasted way too many hours just browsing connector catalogs already. Really.