Sometimes its not about who is the creator, but, more who is the owner.
The word creator is the spinner in the question.
@Peter Simpson is using the UK legal interpretation.
@AHilton tends to be more the rule.
In this country we have law based in the Roman-Dutch form (but applicable law flavours are fairly universal). Whatever that means in this context.
If memory serves, from my days as a journalist here, copyright is vested in the person who paid for the work to be done. Which is not to say anything about the question of who is the creator. All of that is subject to contract law, here, one can write a contract which retains the copyright, but, makes the person who paid the owner. But, one of the interesting things in all of this is that (again if memory serves) the person who translates a book is owner of the copyright in the translation. Which would beg the question in your case - did B simply translate the drawing into the "language" of PCB - which patently looks completely different from the concept drawing.
If I go
paparazzi and start taking photos of Taylor Swift and selling them - its a big technical whether I need to have her permission to do that. I own the photo but she created the image.
Mostly, one ends up with a plagiarism claim, which is what
@emexes is getting at. That's just that A created the drawing (concept/intellectual property) prior to B [provided of course that A dated the drawing]. And, then, naturally, B profits (illegally).
So, its back to the creator-owner conundrum.
A created the concept; B implemented the design. What was the contract between them?
There again, one cannot patent or copyright an idea - where does that put A?
Now if one has worked in the academic world as long as some of us have ....... well lets not go into that darkness.