Help with positional measurement of microprocessor leads
Help with positional measurement of microprocessor leads
(OP)
I'm a lowly measurement technician. They sent me to GD&T training, but it was mostly about theory and applying the principles when drafting up a design drawing. None that helps much when trying to actually measure things using GD&T. There's no one around for me to ask for help, so I'm coming to this forum.
This is a microprocessor drawing with lots of GD&T on it. The questions I have are about the two positional ones. My problem is, the only way I know to do position is an x y coordinate deal with maybe the Pythagorean equation. In this image, I don't have but the one basic dimension in the whole drawing. I'm at a loss as to how they expect this positional measurement to get done. Am I just measuring the distance between a pin middle and the adjacent one, and then taking the absolute difference from the basic dimension? If that were the case, I could only measure 13 instances and not 14 like it asks.
I have a suspicion that GD&T was just plain used incorrectly on this drawing.
Thanks to those that help

This is a microprocessor drawing with lots of GD&T on it. The questions I have are about the two positional ones. My problem is, the only way I know to do position is an x y coordinate deal with maybe the Pythagorean equation. In this image, I don't have but the one basic dimension in the whole drawing. I'm at a loss as to how they expect this positional measurement to get done. Am I just measuring the distance between a pin middle and the adjacent one, and then taking the absolute difference from the basic dimension? If that were the case, I could only measure 13 instances and not 14 like it asks.
I have a suspicion that GD&T was just plain used incorrectly on this drawing.
Thanks to those that help






RE: Help with positional measurement of microprocessor leads
(Actually, they could be more than 0.1 to either side since they each show the "M" symbol -- you should remember the stuff about MMC and bonus tolerance from your training...)
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Help with positional measurement of microprocessor leads
I have one question... Why does your company have you measuring chip components like this? Do you guys manufacture these IC's? Or are you buying them from someone else and using them in your designs? Just curious.
Please, please, please, use the correct terms!They're Datum Features NOT DATUMS!!! AAAAAHAHAHAHHAHAHAHHAAAAA" -- Don Day
RE: Help with positional measurement of microprocessor leads
The part is supplied, not manufactured by the company I work for.
RE: Help with positional measurement of microprocessor leads
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II
RE: Help with positional measurement of microprocessor leads
For example, C|A-B by iteself immobilizes the part; there's no need to refer to D in the 14X position FCF.
There's an EE standards group, JEDEC, that has examples for all the packages and the ones I saw are inconclusive like this one.
RE: Help with positional measurement of microprocessor leads
RE: Help with positional measurement of microprocessor leads
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II