I am new to the PCB assembly world, having worked in bare PCBs for a while, but can help a bit.
Some of the items below seem obvious, but too many customers forget things and don’t get what they want as a result.
The best print notes give all the essential details without leaving important details out. Remember even though your company always does something a particular way, the assembly shop has other customers who use a different method and need more details than someone at your company would.
For your board, state finished assembled boards shall comply with “IPC-A-610 class 3” (“IPC-A-610” is the proper document name). You should also reference a drawing preparation and interpretation spec. ANSI Y14.5 2009 is the most common in the United States, but I have seen older versions or different documents referenced. I have seen bare PCB drawings where the difference between versions was significant.
Reference any other general or top level specs, such as your company specific specification document, if any. I am amazed how often suppliers customers fail to inform the supplier and then complain about an unusual requirement that was “missed.” IPC specs reference other required IPC specs, so there is no need to reference other IPC specs unless they are not referenced as a requirement by the higher level specs.
Cleanliness requirements vary quite a bit. You will need to decide what the correct level is for the type of medical device. The flux used impacts the cleanliness of finished boards. No clean flux leaves more residue behind than properly washed cleanable flux.
Many assembly shops prefer to create their own panelization drawing so they can optimize the panel to their equipment. If you feel you must create a panelization drawing, follow the IPC guidelines.(I don’t have the number handy.) Otherwise assembly shops may have problems assembling your boards.
While not directly related to print notes, when you send the data to potential suppliers, be aware some PCB assembly service providers now prefer data in IPC-2581 format. My company charges more for submissions in other formats because IPC-2581 is more efficient for us. My best guess is in a few more years, many to most assembly shops will prefer IPC-2581 due to the greater efficiency.