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IPC-7351 Padstack Naming Convention |
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PLTcbv 
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Joined: 21 Aug 2012 Location: the Netherlands Status: Offline Points: 134 |
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 Posted: 21 Aug 2013 at 7:06am |
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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: 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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Tom H
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Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 6033 |
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Posted: 26 Jun 2013 at 7:10am |
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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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PLTcbv
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Posted: 26 Jun 2013 at 7:03am |
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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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Tom H
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Posted: 26 Jun 2013 at 6:51am |
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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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PLTcbv
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Posted: 26 Jun 2013 at 1:30am |
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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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Tom H
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Posted: 25 Jun 2013 at 7:24am |
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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 blr – bottom left &
right ubl – upper and bottom
left ubr – upper and bottom
right |
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PLTcbv
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Posted: 25 Jun 2013 at 12:12am |
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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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matthelm
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Joined: 06 Jul 2012 Location: Chicago, IL Status: Offline Points: 21 |
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Posted: 21 Jun 2013 at 12:25pm |
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Tom,
A few suggestion for the NEXT spec for padstack naming convention. (Tom, you've done a great job, these are ONLY suggestions) 1. Use um for the base unit. This way the spec can go smaller when needed, and you don't need to worry where the decimal point goes, as there isn't any. 2. Support leading zeros. This is mainly so the names sort correctly for human interaction. I'm really getting tired of seeing list in 3 different orders, depending on what tool/system is viewing them. You will hit a few exceptions (I currently use 4 in um and 3 in mils, and I have a few inch based pads (maybe 10) over 3 digits , but I'd rather have that, than all my 10 mil and 100 mil and 11 and 100 mil, etc. pads near each other. A software converter could handle both of these easy, as all you would be doing is adding a Leading/trailing zero, or this could easily be a switch only used when creating the pad, not in storage. BTW, for dimensions in part names, I use the same system, but add 1 digit (5 & 4) on each unit. It works very well for me. I don't think I've had any parts fall out of the standard names. |
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Tom H
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Posted: 19 Jun 2013 at 6:50am |
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IPC-7351B introduced the padstack naming convention.
There was no consideration to add the "hole tolerance" to the padstack name. You would have to append the padstack name at the end and since there is no standard for how to represent this, you can invent your own. My recommendation would be a double character modifier like "ht" (hole tolerance) and then the range. You don't have to include the units as everything is considered metric (millimeters). |
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PLTcbv
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Posted: 19 Jun 2013 at 1:26am |
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Hi,
How do we create a correct padstack name for a " Pad 2.7 mm with a Hole Rnd 2.0 +Tol 0.1 -Tol 0 mm" So how do we define hole tolerances in padstack names? Regards, Wim
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