Recommended PCB Layout (Footprint generation)

Thread Starter

odm4286

Joined Sep 20, 2009
252
Hello everyone. I have a feeling I'm missing something. Is it just me or are some datasheets pretty bad at giving good dimensions for PCB footprints. Take a look a this snip from a USB B connector. Center to center, how am I supposed to know the distance, in the x axis, between the mechcanical hole on the far left corner and the pins in the center. Am I missing something obvious here?

1577065721841.png
 

ronsimpson

Joined Oct 7, 2019
1,311
There is a dotted/dashed line vertically in the center. (center line)
The small pin holes are 2.50 apart with center in the middle. So these holes are 1.25 from center line.
Same story, to center line, 12.02 apart or 6.01 to center line.
6.01-1.25= your distance
I have seen mechanical drawings with V and H center lines.
1577067994133.png
 

cmartinez

Joined Jan 17, 2007
7,360
Hello everyone. I have a feeling I'm missing something. Is it just me or are some datasheets pretty bad at giving good dimensions for PCB footprints. Take a look a this snip from a USB B connector. Center to center, how am I supposed to know the distance, in the x axis, between the mechcanical hole on the far left corner and the pins in the center. Am I missing something obvious here?

View attachment 195138
The dashed vertical line represents the part's axis of symmetry. The horizontal dimensions are given using that line as a reference.
 

SLK001

Joined Nov 29, 2011
1,548
Hello everyone. I have a feeling I'm missing something. Is it just me or are some datasheets pretty bad at giving good dimensions for PCB footprints. Take a look a this snip from a USB B connector. Center to center, how am I supposed to know the distance, in the x axis, between the mechcanical hole on the far left corner and the pins in the center. Am I missing something obvious here?

The hole on the lower right seems to be the reference point for the hole locations. Now granted there isn't any information for the external shell (which is needed to complete the footprint, but not the hole locations), it might be elsewhere in the datasheet.
 

jpanhalt

Joined Jan 18, 2008
11,088
Some datasheets are better than others. This one seems complete: https://www.mouser.com/datasheet/2/670/uj2-bv-1-th-1313201.pdf

Also, be aware that distributors' links to datasheets may just be to product releases. Actual datasheets may be from the manufacturers. That seems to be particularly common with connectors, but also happens with electronic components. For example, a link to the "datasheet" for a newer PIC MCU may just be to a product page. Then you need to click on "Documents" and choose what you want there.
 
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