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Questions relating to designing PCBs
By MCPorche
#178502
I'm trying to create a custom part in Eagle, and I've got a couple of questions regarding the footprint, as described on the datasheet.

The datasheet is located at http://www.jameco.com/Jameco/Products/ProdDS/961872.pdf

When I look at the pin layouts I can get the spacing done with no problem. However, I'm trying to figure out the size of the holes/pads, and that's where I'm running into problems.

It says that the smaller ones are 0.92 +/- 0.8 diameter (I assume that's in mm). Is that the size of the hole? If so, does it matter how much larger I make the pad? Also, directly under the 0.92.... there is a box with some numbers and symbols. What does that refer to?

Thanks in advance for any help you can provide.

Monte
By Valen
#178513
Yes, mm is correct. See the tiny mm's in the lower right corner table. Also, it's the hole in the PCB that should be 0.92 with tolerance +/- 0.08.

I don't know about what those symbols in those boxes mean.
By MCPorche
#178515
Thanks a lot. I was figuring on making my holes 1mm, but I wasn't sure if the info in those boxes was somehow relevant.

I'll go with that and print one out and see if it fits.
By Valen
#178517
0.92+0.08 is 1 mm. But if you specifiy a 1mm drill then the resulting hole might end up larger if the drill moves around.

Ok, I realized that I still had my old drafting book from college in my bookcase. It doesn't completely explain the symbols. But the circle crosshair means it is about the position accuracy of the hole centers. The 0.1 means it should fall within a circle of that diameter at the given dimensions. The M in a circle means Maximum Material Condition, which I haven't heard of myself. (I guess I was asleep in class at the time) But this should get you a bit further in understanding, or at least help search further:
http://www.emachineshop.com/machine-sho ... ge589.html

The A, B, Z and Y probably means the position accuracy is referenced to those sides (datums) of the PCB which have those labels. The meaning of S-within-circle is something I cannot deduce from my book. It is in dutch and talks about P (positie =position) and V (vorm =shape) deviations. It probably doesn't help, but that is all that I can offer now.
By InactiveUser001
#178581
Make them 1.0mm.
It will make them easy enough to fit and they should solder OK as long as you have enough copper land.
Also if the supplier is changed then an alternative will fit.