Datum Points

[shortckt]

Problem Description :

When I transfer the schematic from multisim to ultiboard, three datums were

created automatically outside of the board layout. Following are my

questions:

1. How to create each of the datums( x & y coordinates) manually in Ultiboard or to find the coordinates of these automatically created datums (they should be inside the board to begin with)?

2. Which one is the primary, secondary and so on?

3. Once I refer the primary datum, does all the pads on the PCB reference to

that datum?

4. How does all the pads location transferred to the gerber file?

5. I am using fudicial's as local datums on the PCB and using global fudicial's on the PCB panel. How can I refer the global fudicial in respect to the local fudicial via ultiboard?

6. In Ultiboard can I create a array of PCB's to mimic a 4X4 PCB panel?

Thanks

Faisal Rahman

[lacy]

You will have tio forgive my lack of understanding of your terminolgy. What are your refering to a datums and fudicials? If I know this I may know how to help. I may refer to these by differnt names.

[shortckt]

Thanks Lacy....

Datums: Refernce point that you would set to place components on the baord. You can also dimension your board from this point. The defination would be datum used in Geometric Dimensioning and Tolerancing is a feature on an object used to create a reference system for measurement.

Fudicial : A kind of datum.

You'll notice that when you transfer a schematic from Multisim to Ultiboard on the board layout the datum points already exists. According to NI (yesterday got an email from them) that these point are reference to x=0 & y=0 and all the pads traces  board  GD&T  should be off from this point. If thats the case, then does the gerber file contains all these information so during manufacturing the machine can read off the gerber to place the componets route the trace on the various layers? Can the datum points be manually created rather than automatically created by the software and how?

[lacy]

If I am correct then you are refering to the board reference point that is usually in the lower left corner of the board outline.I can't be certain as to exactly how the gerbers do thier job since they are in a machine code, but I would assume that it would have to use your reference point as its starting point otherwise the parts would be placed where you didn't want them in the final product. This, in my opinion, is the reason we have this refernce point. If they used a different method for placing parts and holes then we wouldn't need to place a reference point. I could be wrong, but this is the way I see it. Anyway, what I do know is that if you lay a board out in Ultiboard, unless there is some major malfunction, then you should get a board that looks like your layout back from the board manufacturer.

As far as creating and manually creating reference points, I do not know of a way to do this. The only thing I see is that you can adjust the current one as far as postion or delete it, and manipulate its size on the screen.

I hope I have helped some. This is about all I know on this subject. Maybe one of the users who have a little more understanding of the actual contents of the gerbers can address this a little further.