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- # IPC-7251 & 7351 Padstack Naming Convention
- Hereafter follow some copy/paste snipptes I found regarding padstacks and a naming convention.
- ## INTRODUCTION
- The padstack consists of combinations of letters and numbers that represent
- shape, or dimensions of lands on different layers of printed boards or documentation.
- The name of the padstack needs to represent all the various combinations.
- These are used in combination with the land pattern conventions defined herein
- according to the rules established in the IPC-2220 Design standards.
- The first part of the padstack convention consists of a land shape.
- There are six basic land shape identifiers.
- Note: All alphabetical characters are “lower case”.
- This helps discriminate numeric values.
- Illegal characters that cannot be used (Microsoft requirement) include “ ” , ; : / \ [ ] ( ) . { } * & % # $ ! @ ^ =
- Basic Land Shape Letters
- c = Circular
- s = Square
- r = Rectangle
- b = Oblong
- u = Contour (Irregular Shape)
- d = D Shape (Square on one end and Circular on the other end)
- h = Hole
- Examples utilizing the padstack naming convention (all values are in metric units)
- Note: Every number goes two places to the right and as many as needed to the left of the decimal
- Examples: 1150 = 11.50 mm or 11500 μm, 150 = 1.50 mm or 1500 μm, 15 = 0.15 mm or 150 μm.
- **This leads to one unit being 1/100th of a mm, or a centi-milimeter ... a [cmm] ;-)**
- c150h90 where “c” denotes a Circular land with a 1.50 diameter and H denotes a hole size of 0.90
- v50h25 where a “v” denotes a via with a 0.50 land (default Circular land) and H denotes a 0.25 hole
- s150h90 where “s” denotes a 1.50 Square land and H denotes a hole size of 0.90
- s350 where ‘s” denotes a square SMT land size of 3.50
- r200_100 where “r” denotes a Rectangular SMT land 2.00 land length X 1.00 land width
- b300_150 where “b” denotes a SMT Oblong land size of 3.00 X 1.50
- b400_200h100 where “b” denotes an Oblong land size of 4.00 length X 2.00 width and 1.00 hole
- d300_150 where “d” denotes land with one circular end and one square end (looks like a D) 3.00 X 1.50
- v30h15l1-3 where “v” denotes a 0.30 blind via with 0.15 Hole; 1 is the starting layer, 3 is the end layer
- r200_100r5 = Rounded Rectangular 2mm X 1mm X 0.05mm radius corners
- r200_100c10 = Chamfered Rectangular 2mm X 1mm X 0.1mm chamfered corners
- v30h15l3-6 where “v” denotes a 0.30 buried via with 0.15 Hole; 3 is the starting layer, 6 is the end layer
- ## Modifiers that are used when padstack features are different than the defaults
- These are the “Variants” or “Modifiers” that go after the basic padstack naming convention.
- These are used when the User needs to change the padstack default values either by a different dimension or a different shape. In instances where shapes are different this becomes a two letter code with the modifier first followed by the land shape letter.
- n = Non-plated Hole
- z = Inner Layer land dimension if different than the land on primary layer
- x = Special modifier used alone or following other modifiers for lands on opposite side to primary layer land dimension
- t = Thermal Relief; if different than IPC standard padstack – tid_od_sw for 4 spoke default
- m = Solder Mask if different than default 1:1 scale of land
- p = Solder Paste if different than default 1:1 scale of land
- a = Assembly surface land if different than default 1:1 scale of land
- y = Plane Clearance (Anti-pad) if the value is different than the Thermal OD
- o = Offset Land Origin
- k = Keep-out
- r = Radius for Rounded Rectangular Land Shape
- c = Chamfer for Chamfered Rectangular Land Shape
- Shape change is the last letter in the string prior to the dimension.
- ## Other usage of the padstack naming convention
- USE of letter v: Vias can be named using the pad stack naming convention.
- Because most vias use lands that are circular in shape, the letter V will be
- used in place of the letter C in the padstack naming convention.
- If this is not true the modifiers can be added after the letter V to signify
- shape or dimensional changes to this default.
- USE of letter w: In addition to Vias the padstack naming convention can also be
- used for defining mounting holes.
- The letter W shall be used to define the mounting hole characteristics and any
- associated lands used for the surface lands (either plated or un-plated).
- Examples of double character modifiers:
- ts = Thermal Square; if different than the top side land shape and dimensions
- sw = Thermal spoke width
- zs = Inner Layer Land Shape is Square (Note: The default is circular)
- m0 = No Solder Mask
- mxc = Solder Mask Opposite Side Circular
- mx0 = Solder Mask Opposite Side No Solder Mask
- xc = Opposite Side Circular
- vs = Via with Square land
- hn = Non-plated Hole
- ### Modifier Example for Through-hole:
- s150h90zs150 = where “s” is Square 1.50 land with 0.90 Hole with 1.50 inner (Z) Layer Square land
- c150h90zc150 = where “c” is Circular 1.50 land with 0.90 Hole with 1.50 inner (Z) Layer Circular land
- ### Modifier Examples for Vias:
- vs50h25 where “vs” denotes a 0.50 Square Via with a 0.25 Hole
- v50h25xs70 where “v” is 0.50 Circular Via with 0.25 Hole and 0.70 Square land on opposite side
- ## 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
- ulr – upper left & right
- blr – bottom left & right
- ubl – upper and bottom left
- ubr – upper and bottom right
- ### Rounded and Chamfered lands in “one corner” Modifier Examples:
- r100_200rbl50 = rectangular land 1.00 x 2.00 with 0.50 radius for rounded corner in bottom left corner
- r100_200rbr50 = rectangular land 1.00 x 2.00 with 0.50 radius for rounded corner in bottom right corner
- r100_200rul50 = rectangular land 1.00 x 2.00 with 0.50 radius for rounded corner in upper left corner
- r100_200rur50 = rectangular land 1.00 x 2.00 with 0.50 radius for rounded corner in upper right corner
- r100_200cbl50 = rectangular land 1.00 x 2.00 with 0.50 chamfer for chamfer corner in bottom left corner
- r100_200cbr50 = rectangular land 1.00 x 2.00 with 0.50 chamfer for chamfer corner in bottom right corne
- r100_200cul50 = rectangular land 1.00 x 2.00 with 0.50 chamfer for chamfer corner in upper left corner
- r100_200cur50 = rectangular land 1.00 x 2.00 with 0.50 chamfer for chamfer corner in upper right corner
- Chamfered and Rounded Rectangular with all four corners chamfered does not need a corner modifier.
- ### Modifier Examples with Rounded Rectangle Land Shape:
- r200_100r50 = rectangular land 2.00 x 1.00 with 0.50 radius for rounded corners in all 4 corners
- r200_100c50 = rectangular land 2.00 x 1.00 with 0.50 chamfer for chamfered corners in all 4 corners
- ## Examples of a padstack with Circular land with hole using various modifiers
- c150h90 = Default padstack with a 1.50 circular land with a 0.90 hole (no modifiers used)
- c150hn90 = Default padstack with a 1.50 circular land with a 0.90 non-plated hole
- (no modifiers used)
- c150h90z140 = Inner layer land is smaller than external lands 1.40 or 0.10 smaller
- c150h90z140x170 = Opposite side land is larger than top side land 1.70 or 0.20 larger
- c150h90z140x170m165mx185 = Solder mask opening for top and bottom lands 0.15 larger for each
- c150h90z140x170m165mX185a200 = Assembly drawing land in 0.50 larger than 1.50 primary land
- c150h90z140x170m165mx185a200y300 = Plane clearance anti-pad diameter is 3.00
- c150h90z140x170m165mx85 = Solder mask encroachment on opposite land by 0.65 smaller
- c150h90m165 = adding a solder mask opening of 1.65 diameter or 0.15 larger than land
- c150h90t150_180_40 = Thermal ID 1.50, OD 1.80, Spoke Width 0.40, Anti-pad 1.80
- c150h90t150_180_40y200 = Anti-pad 2.00 (because the size is different than the Thermal OD)
- c150h90t150_180_80_2 = Spoke Width 0.80 with 2 Spokes
- c150h90m165t150_180_40 = Solder Mask 1.65
- ## Examples of a padstack with Oblong land with Slotted Hole
- Sample – b = Oblong Land Shape then “X” dimension (length) then Underscore _ “Y” dimension (width)
- b400_200h300_100 = Oblong land 4mm length X 2mm width with slotted hole size 3mm X 1mm
- b400_200hn300_100 = Oblong land 4mm X 2mm with non-plated slotted hole size 3mm X 1mm
- ## Examples of a SMT padstack land using various modifiers
- b300_150 = Default padstack with a 3.00 length and 1.50 width land (no modifiers used)
- b300_150m330_180 = Solder Mask is 0.30 larger than the land
- b300_150m330_180p240_140 = Solder Paste is smaller by 0.10 width and 0.60 length
- b300_150b-50 = Oblong Land 3.0mm X 1.5mm w/Offset Origin negative 0.5mm
- r400_200po430_230 = Rectangle SMT land 4.00 X 2.00 with a Oblong Solder
- Paste size of 4.30 X 2.30
- ## Example of a Mounting Hole
- w700h400z520m720 = This is a Plated Through Mounting hole for a #6-32 screw
- using a 4.00 diameter hole and having a circular 7.00 land on the primary and
- secondary side of the board, with a solder mask clearance that is 0.20 larger
- than the 7.20 land.
- The internal lands are smaller that the external and are also circular 5.20 in
- diameter.
- w700hn400z520m720 = Non-plated version
- ## Example of a Local Fiducial for Fine Pitch SMT Components
- c100m200k200 = Circular Land 1.00 with Solder Mask 2.00 with Keep-out 2.00
- s100m200k200 = Square Land 1.00 with Solder Mask 2.00 with Keep-out 2.00
- ## Example of Proportional Plated Through-hole padstack
- c150h100 = 1.5mm circular pad with 1mm hole with 1.5mm solder mask with 1.5mm
- plane clearance with 1.5mm assembly outline with Thermal Relief w/4 spokes
- 0.4mm width with ID 1.5mm and OD 1.8mm
- ## Example of Proportional Non-plated Through-hole padstack
- c100h150 = 1mm circular pad with 1.5mm hole with 1.5mm solder mask with
- 2.35mm plane clearance with 2.1mm keep-out
- # Possible implementation
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