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IPC-7351 Padstack Naming Convention

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PLTcbv View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PLTcbv Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2013 at 12:12am
Tom,

When do we use the"u" for a padstack?
Looking at the document I see: u = User Defined Contour (Irregular Shape)

Some examples in the document:
s300p190r25cul50 = square 3.00 land, square paste 1.90, corner radius 0.25, upper-left chamfer 0.50
u480p4s152cul50 = 4.80mm Square Land with 4 Paste Mask Squares 1.52mm each with 0.50mm Chamfer in Upper Left corner

They are both squares with a upper-left chamfer, so an Irregular Shape.
Why is the first a "s" and the second a "u"?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jun 2013 at 7:24am
The letter "u" is used twice.
 
If you see the letter "u" as the very 1st character it represents "user defined pad shape".
 

c = Circular   

s = Square

r = Rectangle

b = Oblong

u = User Defined Contour (Irregular Shape)

d = D Shape (Square on one end and Circular on the other end)

 
If you see "u" in the middle of the padstack name it represents "Upper" when chamfered or radius corners are used.
 

bl – bottom left
br – bottom right
ul – upper left
ur – upper right
ulr – upper left & right

blr – bottom left & right

ubl – upper and bottom left

ubr – upper and bottom right

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Post Options Post Options   Thanks (0) Thanks(0)   Quote PLTcbv Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2013 at 1:30am
I understand that the letter "u" is used twice.

I was just wondering when to use a "s" and when a "u".
If you look at s300p190r25cul50 and u480p4s152cul50 in the document these are both a Square land with 0.5 mm Chamfer in Upper Left Corner, but sometimes the padstack starts with "s" and sometimes it starts with "u".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2013 at 6:51am
To use "u" for a square pad with a corner chamfer is the wrong application of the IPC padstack naming convention.
 
If the first character is "u" the pad shape is irregular (free form) and not square.
 
Are you telling me that the FP Designer produces a padstack name of u480p4s152cul50?
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PLTcbv Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2013 at 7:03am
No, I was looking at the begin off this post.
Look at:
Examples of a square land with 3 rounded and 1 chamfered corner (for Thermal Pad)
and
Example of Thermal Pads for QFN, SON, QFP and SOP

Both square pad different notation.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jun 2013 at 7:10am
Well then thanks for pointing that out so we can get the record straight.
 
"u" should not be used for the primary letter for square pads with chamfers.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PLTcbv Quote  Post ReplyReply Direct Link To This Post Posted: 21 Aug 2013 at 7:06am
Padstack Naming Convention: 
Chamfered & Rounded corner modifiers are used to indicate which corner(s) are modified.

Order of precedence has been given to the first 4 modifiers.

 

Modifiers:
bl – bottom left
br – bottom right
ul – upper left
ur – upper right


If you use the Padstack Designer in PCB LE Lite the modifiers are:

ll - Lower left

lr - Lower right

ul - Upper left

ur - Upper right



Which is correct bl or ll / br or lr?


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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 Aug 2013 at 7:46am
Once Jeff gets back from vacation in a week, we'll fix this padstack naming convention to match IPC-7351.
 
Thanks for reporting this!
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick B Quote  Post ReplyReply Direct Link To This Post Posted: 01 Sep 2013 at 4:31am
This was fixed in 2013.11, to be released within the next couple days.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PLTcbv Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2013 at 2:06am
I'm looking at 2013.12 and it looks like it was't fixed.

Still "Lower Left" and "Lower Right". Should be according IPC "Bottom Left" and "Bottom Right".
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