I am attempting to create a footprint for a Surface Mount Component and I am using the manufacturer's datasheet for reference. They include PCB dimensions but the notation used is a bit confusing. It has a P and I am unsure what to make of it, another is almost an order of magnitude greater than what it should be, and again I suspect it is a notation.

The datasheet states the unit to be mm, which is helpful. But some of the dimensions do not make much sense, and I am certain this is because I lack understanding. I have looked extensively and I cannot find any source about this, to the point that I decided to ask here. If anyone could provide some insight I would greatly appreciate it.

(The images are drawn to scale, and I have circled the confusing parts)

Straight to the point: What do the notations in these red circles (on the images provided, both the P notation and the 10-0.7) represent? The units are in millimeters and one of the P-notated dimensions is nice enough to have an = sign to represent what the actual value is (P1.27 x 4 = 5.08mm) while the other: I have deduced that 10-0.7 = 0.7mm.

Thank you for taking the time to read this! Please even if you do not know the answer feel free to share your thoughts!

P notation and another 10-0.7 notation

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    \$\begingroup\$ Haven't seen that before but it probably stands for "pitch". When the center-to-center distance between the pads is 1.27 mm, we say they are on "1.27 mm pitch". \$\endgroup\$ – The Photon Feb 14 '15 at 2:32
  • \$\begingroup\$ Thank you so much! This makes absolute sense! When looked at it that way, since there are markers in the centerpieces, it adds up to be the right distance! \$\endgroup\$ – Kilogic Feb 14 '15 at 2:43
  • \$\begingroup\$ @Kilogic For future reference. You don't need to manually edit the heading just to say that the question has been answered. StackExchange UI take care if this automatically when you accept the answer. Your question will have a green rectangle around it, so it will stand out in the list of questions, because it has been answered. \$\endgroup\$ – Nick Alexeev Feb 14 '15 at 6:38
  • \$\begingroup\$ Thank you for that information! As you can probably tell I am new to this web-based community as a contributor and I really appreciate the information! \$\endgroup\$ – Kilogic Feb 15 '15 at 3:00

P is the nominal pitch of 1.27mm (0.05"). There are 4 spaces for 5 pads so the total distance between centers of the outer pads in the group is 5.08mm (0.2").

The other notation indicates that there are 10 pads, each 0.7mm wide and 4 pads, each 0.8mm wide. It is obvious in this case which are which, but in general when you see this kind of notation with a quantity in a mechanical drawing look for symmetry.

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    \$\begingroup\$ Thank you very much! I had absolutely no clue as to what make of the '10' and the '4' (indicating the number of pads that would carry that dimension). You have answered both parts of my question and I am really grateful. I hope others can see this question and the answers provided and learn from it as I have! Again, Thank you for taking the time to answer this question and share your knowledge with me and the world! \$\endgroup\$ – Kilogic Feb 14 '15 at 3:10

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