manufacturingpcbpcb-assemblypcb-fabricationstencil
While making PCB, I added 8 fiducials (fids) marks so that pick and place machines use these marks as referent points on the PCB to position the surface mount components (Packages) during assembly.
But when I sent same Gerber file to stencil manufacturer, they asked me "do you require fiducials half etched or through cut".
I don't have any idea about half-etched fids. Could someone explain the difference between these two?
All I can found a web link but it does not serve the purpose.
This depends on the technology you're using for soldering the through-hole parts. If you're hand-soldering them then no, you do not need a stencil. However, if you are using paste-in-hole technology (aka "intrusive soldering") then you might. There are a number of different ways to apply paste for intrusive soldering and if you do it by hand (use a syringe to apply the paste in and around the hole) then no stencil is required. Otherwise if the application of paste is automated, you probably will need a stencil. Note you may need a separate, thicker stencil for applying paste for intrusive soldering due to the larger amount of paste required for through-hole soldering versus surface mount.
According to this application note from norcott, three global fiducials are used to determine the correct orientation of the board (or panel).
Relevant quote:
It is important that only three fiducials are used. This ensures that if a panel is accidently inserted into the placement equipment rotated through 180°, the equipment can detect it and halt assembly.
And for a single board without a panel, those fiducials are placed on the board, and will show up in the end:
(images taken from the application note)
There is no specific mention of routing the board outline in that document, but I can imagine that they use this also in the routing machine to make sure that the board has the right orientation.
Best Answer
According to Seeed Studio, there are three options for fiducials on SMT stencils. Note what they say about half etched fiducials below:
No fiducial ---- No positioning holes required on the stencil
Etched Though --- Positioning holes that go all the way through the stencil. Useful for manually holding the stencil in a fixture for manual/semi-manual paste application. These should be specified in the files by the customer since exact requirements depend on the customers' own preferences.
Half Etched --- Holes that go half-way through the stencil. These are needed for some fully automated paste applicators. The diameter is typically 1mm and are added to the corners of the stencil by our engineers if not already designed in the files.
SOURCE: http://support.seeedstudio.com/knowledgebase/articles/1156336-what-are-smt-stencil-fiducial-marks