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4 Pins Crystal SMD Footprint

barakg , 11-04-2018, 12:30 AM

I'm designing PCB that includes 24MHz SMD 4 pins crystal https://abracon.com/AIGcrystals/ABM10AIG.pdf
According to my understanding, the crystal package marking is for Pin number 4. it looks like pin 4 pad has a 'corner'.

I wonder, how should I indicate in the PCB this pin? Should I put a circle near this pinas I do to any SMD to indicate Pin #1?
actually, I did it but I'm not sure about it.

Is there any standard or marking for this situation?

Thank you very much.
mohsin_qau , 11-05-2018, 12:57 AM
For SMD Crystals, there is bit confusion always. For these crystals, the reference is the Crystal connections, not the Pin#1. The standard rule for these type of crystal is Pin#4 as the reference.
barakg , 11-05-2018, 01:08 AM
But the manufacture will understand that the mark is for pin #4? I'm not sure about it..
Paul van Avesaath , 11-06-2018, 05:32 AM
just some examples.. i have never heard of any problem in the way you preform the outline.. its all done through your pick and placement file or ODB++.
main reason for doing it is so you can visually check yourself (or with automated visual inspection AOI) that the component is placed correctly.

pin markings are alway ALWAYS for Pin 1 so mark pin 1 and pin 4 should be correct..

edit: as an after thought, check with the abracon vendor if the datasheet is correct in this case.
Paul van Avesaath , 11-07-2018, 12:50 AM
I just rememberd I have used abracon before, and just to be clear my datasheet is different than yours with regards to the footprint.. I find it strange they would indicate pin 4 like in your datasheet...
i would double check it. just to be sure.
mohsin_qau , 11-07-2018, 11:41 AM
Yes there is difference, But as i said earlier that the main reference is the Crystal Pins connections, i.e. between Pin#1 and Pin#3.
robertferanec , 11-08-2018, 01:15 AM
I remember this one Once we exactly had problem with this situation. The best is to use clear number 1 or circle on silkscreen (and mark number 1 position clearly in assembly drawing). Good Assembly house is careful enough to check pin position of specific component in datasheet. PS: I may be wrong, but I think, Abracon may also have same crystal in "correct" footprint (with a little bit different part number), so maybe cutting corner on silkscreen may be confusing.
Paul van Avesaath , 11-08-2018, 01:23 AM
it could be that in some cases a pcb design has been made and it is cheaper to get the manufacturer change the pins than doing a redesign on a board... because if you mirror the footprint you or designed it the from the bottom side instead of top down. I would bet that if intel would ask to change it they would change it
robertferanec , 11-08-2018, 01:48 AM
@Paul van Avesaath I was thinking the same when I saw it the first time or .... also I thought, that maybe by mistake they manufactured millions of crystals wrong way and it was cheaper to change datasheet
Paul van Avesaath , 11-08-2018, 01:55 AM
aaahhhh don't we all have that one monday morning after a very pleasant weekend were we are still a bit drunk of the day before.... when we think I will let auto-pilot do the works this morning.. and don't see the stupid mistake you just made.. and production pops out wrong... hahaha ... well would make sence they would change the datasheet and sell it as a "feature" LOL
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