Electronic – Why are there no easy-to-solder SMD diodes in 0603 packages

Some cap vendors make their own parts. Some buy caps from a smaller manufacture with the reels re-branded at the fab. Watch out. I got into a mlcc failure investigation in 2002 and started inspecting caps on a reel under a microscope. 3/10 came off the reel cracked. A crack will sooner or later lead to a short. Cracks are not obvious even under a microscope. They may present as a subtle colour shift if the crack is below the surface layer. Some cracks may be sufficient to present a short immediately. Not all. The vendor's manufacturer in this case eventually identified a hopper where the caps were getting cracked.

MLCC are very sensitive to mechanical stress. Especially bigger than 1210 sizes. I found a big power bypass cap adjacent to a heavy mechanical connector once. The nearest mounting hole was 2" away! They were cracking at a rate of 5/10 during install of the unit. A fraction of those were catching fire. The fire would continue to burn until it melted the copper, breaking the power connection.

Another effect of a crack is a reduction of the max working voltage of the cap. It might be spec'd for 200 V. But once cracked it may break down at 40 V. Cracked caps burst into flames in my lab when tested - even below their rated voltage.

Another way to warm up caps is exceeding their max ac current. It's easy to think of caps as zero power dissipation devices. Especially the higher Q mlcc. But they're not. Calculate the power dissipated in caps and do not exceed power/ac current limits. Shows up in power circuits and converters commonly.

C: definitely the assembly shop, if you have the wallet for it. That's for you to decide. Ask some quotes, and decide if doing it yourself is worth the effort. Since this is a hobby project you may think your time is free, but then it has to stay fun as well, hasn't it?

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Just got this in a mailing from DesignSpark: fundraising may get you started to have it done by a shop. Erik raised 313 218 dollar for a 5 000 dollar target.
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Alternatively, B: Again, get a quote for a stencil. Yet, even applying the solder paste manually will take less time than hand soldering, which I would not recommend: the resistors and capacitors are not much of a problem, but the ICs may take quite some time if you want to do it proper, i.e. all pins soldered and no short-circuits.

Not A: it takes too long and it's messy. I would only do it myself if I could use the oven.

Remember that Jobs and the Woz also hand-assembled their first batch of Apple computers :-)