Hi, have created a few footprints for hand soldering, but now progressing to getting boards made that use the footprints I’ve created.
In the learning process for creating position files it occurred to me that I might not have created my footprints with pick n place in mind.
My searches yielded nothing useful on the topic.
When drawing a footprint from a data sheet is there a clue on a data sheet that might show me where to reference the center or pickup point of the physical component that i might have been missing?
Is there a way to know how to center a component?
Once i do know the center do i just center it in the footprint editor on the blue cross or is there a location i need to mark?
Other than these questions pretty happy comfy with the footprint editor i think.
Any assistance appreciated.
Basically yes. The center of the footprint in the footprint editor should be the physical center (at least for SMT) and is usually also used for pick an place by most export scripts for manufacturers.
Possibly? the easiest way to set the centre is to (in this case):
Place cursor at top RH corner of pad 1,
Press space bar,
Move cursor to bottom LH corner of pad 5.
Read “dx & dy” (in cyan box) and take note of half of each reading,
Click “Anchor Point” icon (green arrow).
Move mouse 'till dx & dy show the half reading you have previously noted,
Left click mouse and the footprint will now be centred.
Note: the finer the grid you use to set the centre, the more accurate the result.
Maybe a temporary L x W outline according to the manufacturers data sheet, on a user drawing layer, may be better in some instances, or maybe …
Still the same procedure as above for the easiest way to center the component.
Much more precise than trying to move the footprint to the cross-hairs.
Many component datasheets have that information, but not necessarily in the footprint (land pattern) suggestion or in the package dimensions. It may be in the reel packaging information.
For guidance on location of the anchor of the footprint, you can refer to KLC section 6.2 " Footprint anchor should be placed in the middle of the component body"
As to the orientation you can refer to KLC section 4.2 " Pin 1 should be located at the top left"
Not all pick-and-place houses use the same conventions, but if you use these then you will be using the same convention as the provided “official KiCad” libraries. I’m not sure of section 6.2 follows any industry standard (other than the general knowledge that most of KLC does try to follow one of the many, often conflicting, industry standards, but section 4.2 specifically mentions that it is intended to follow IPC-7351. This may be valuable information to the pick-and-place house so they know how your POS file may differ (or match) their in-house convention.
If you are interested in knowing more about what IPC-7351 says, your favorite internet search engine should help you. Legally getting a copy of IPC-7351 would require you to purchase it from IPC, but there are several articles discussing different parts of the standard. I’ve also found full PDF copies out there on the interwebs. Because of the copyright infringing status of the freely available copies, I don’t feel right posting direct links to them here. I don’t want to subject this forum to potential legal jeopardy by posting links to copyright violating sources.
