Go Down

Topic: Question about pad size (Read 1 time) previous topic - next topic

liudr

I just finished a design with a part , A1202UA (A12*?), from the allegro library in EAGLE. Here is what it looks like inside the library, normal:


Here is what it looks like on my design. Notice that the pads have swollen, too big and thus too close.


Is there some settings in EAGLE that overrides the pad sizes of library items? Thanks.

liudr

Later I made a package in my own library using smaller pads but after I saved the package and was trying to build a device then the pads grew big in the device view. Weird.

westfw

Yes, this is controlled by the "restRing" DRC parameter.  typically it will ensure that the amount of copper surrounding a hole is some minimum width, either by absolute width or as a percentage of the hole size.

This is usually a good thing...

liudr

Thank you westfw! In this case, the pads are 0.05" apart, for a Hall switch so maybe I should use 0.1" pitch pin headers on the board and slightly bend the pins to fit?

westfw

0.05 inch space pins are a pain.  If it's something like a TO92 with long bendable leads, just move the pins apart (see the assorted TO92 transistor layouts.)  If it's some sort of rigid connector ... using tiny holes, let the pads get as close as you dare, and hope.

liudr

westfw, thank you for your suggestion. The package is supposed to be SIP and the pins seem soft enough to bend. I'll use 0.1" pitch 3-pinheader footprint for it.

davekw7x

#6
Jan 13, 2011, 05:35 pm Last Edit: Jan 13, 2011, 08:12 pm by davekw7x Reason: 1
Open the library and the footprint of the component.

Right-click on one of the pads, and select "properties."  If it says that the diameter is "auto" then when you use it in your circuit the pads may expand or shrink according to design rules.  Enter a diameter setting to something that looks right to you.  The pad sizes will not change from the size that you give them.  You will have to do this with all pads on any given footprint.

If what "looks right" to you violates design rules, then you may have to change the drill size or change the design rules or some such thing.  Check with the board fab house to see about drill sizes, minimum trace size, minimum clearance and other design rules that you may want to change.



Regards,

Dave

Footnote:
If the diameter was not set to "auto," then, never mind...

liudr

Dave, thanks. It was not. I opened the part and it had a number there. I also created a new footprint with a numerical size, not auto but still doesn't work. I later just used 0.1" headers as suggested by westfw, bend the pins. I'll try this again once I have time.

Go Up