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Maximum Height in Footprint Naming Convention

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sebgonzo View Drop Down
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    Posted: 21 May 2019 at 4:27am
Sorry if this has already been answered, but I couldn't find it.

Why in PCB footprint naming height dimension is specified as maximum, where others are nominal? 

I can not find any good reason for this exception.

In my opinion this creates many exactly the same footprints only with different name because of height tolerance differences.

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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2019 at 8:31am
For 2 main reasons - 
  1. We see millions of component datasheets and many of them only provide the Maximum height dimension. We cannot guess at what the Nominal dimension might be. However, they always provide the maximum height dimension even if they provide the Nominal + tolerance. So basically every component datasheet (and there are 100 million of them) always provide the Maximum height. 
  2. The 3D STEP model name is the same as the footprint name. In 3D modeling, Maximum height is really important for validation in the enclosure.
However, there are 3D Modeling controls in the CAD tool interface to select Nominal or Maximum density level. 

Also, most people do not think to consider the solder under the leads that lift the part up. So, by using the Maximum height you kind of compensate for the solder buildup. 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sebgonzo Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 2:27am
OK, thank you for quick answer. This makes sense now Smile
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