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You can practically achieve it either way, but I think using keep-out region in the footprint is better. That way you always have the required clearance automatically, when you place a fiducial in the board. Otherwise you have to set up a rule for each board you work on and sometimes you might forget.
Yes, I do it the same way, but you need to specify a clearance, for example when you draw a polygon or a plane. How do you do it? Clearance rule? Keepout?
Thanks!!
For the keepout region you need it to be a filled circle which covers the fiducials and solder mask expansion. However, in Altium you can't draw a filled circle so you have to cheat it. You can draw an arc, which is a part of a circle with parameters angle, radius and width of the line. To make a full filled circle, you need to make the arc 360 degrees, give it a radius of D/4 (D is the diameter of the filled circle you need) and give it a line width of D/2. Arc is one of the standard drawing elements available from the Place menu. Here is an example of a keep-out region used for the fiducial (the diameter in the example is 10mm because it is just an example, with the actual fiducial I am using 3mm):
Play around with drawing arcs and you will get what I mean.
You can do it in different ways.
I have my fiducials as components in my libraries. The fiducial itself is a top layer only pad, with diameter of 1mm and specified solder mask expansion value of 1mm (so that we have 3mm mask opening). For the clearance, I have a copper circle (made by 360 degrees thick arc) with external diameter of 3mm, which in the properties is marked as keep-out.
Ok, thank you. I have one more question. How do you do to left an opening region around the fiducial (the mask opening)? I have been looking for the best way to do it and I have found one way, but I do not know if it is the best one. I have defined a CLEARANCE RULE for the fiducial I am using. I have set the clearance to 1mm (this is what I need) so, when I put a fiducial with a 2mm diameter, I have 1mm around the pad free of copper or anything else. Is this a good way to do it?
What this statement means is that if you connect the 3 fiducials with imaginary lines (yes the fiducials might be in the corners as they often are), you will get a right angle between two of the lines.
And just for the topic - I normally use 1mm fiducials with 3mm solder mask opening placed in the corners of the board. I could have fiducials either on the board, on the panel, or on both depending on if I have space or not.
You also need fiducials on the bottom side of the board if you have components on that side.
So, I should include fiducials in the board itself. One on each corner. I should also include fiducials on the panel. Again, one on each panel corner. I do not understand "3 fiducials should lie on two lines that intersect at a right angle". Don´t you say they has to go on each panel corner? Thank you!!
In our designs, fiducials are simple components. In SCH Library, there is no PIN and Type is set to "Standard (No BOM)". Footprint is a simple PAD. We normally use three kind of fiducials:
- board fiducials, standard: 40mil pad / 120mil mask opening
- board fiducials, small: 30mil pad / 52mil mask opening
- panel fiducials: 40-60mil + mask opening at least 40mil greater than fiducials
We place them into board corners and we also include following note on Manufacturing notes layer:
PANELIZE THE BOARD (2PCS PER PANEL). PLACE FIDUCIALS ON THE PANEL STRIPS AS FOLLOWS:
- FIDUCIAL DIAMTER 1-1.5MM, SOLDER MASK OPENING AT LEAST 1MM GREATER THAN FIDUCIAL
- MINIMUM 4MM DISTANCE FROM THE PANEL EDGE
- 3 FIDUCIALS SHOULD LIE ON TWO LINES THAT INTERSECT AT A RIGHT ANGLE
- PLACE ONE FIDUCIAL INTO EACH PANEL CORNER (FOUR ON THE TOP AND FOUR ON THE BOTTOM LAYER)
I want to ask a question about FIDUCIALS. Is there a specific way to create them in Altium? Any recommendation about how to create them and the best way to position them in the board?
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