ODA Pad Stack Naming Convention

Revision 2. Supersedes the 13 April 2026 issue. Reorganized, and incorporates the collision audit resolutions and the subtracted-land (ring) rule of 2 September 2026. Companion to the ODA Land Pattern Creation Guide.

1 Introduction and Scope

The pad stack name is a compact, complete description of the pad stack: letters and numbers that state the shape and dimensions of the lands, openings and holes on every layer that matters. Two physically different pad stacks never share a name, and one pad stack never has two valid names. This convention was created by Optimum Design Associates.

Name derivation

A pad stack name is a deterministic function of the pad stack geometry and the pad stack type (Section 3). It is not an attribute stored on the pad stack. The name shall be regenerated whenever the geometry changes, whenever the selected naming convention changes, and at the point where library or CAD output is produced - regardless of how the pad stack was originally created. A name may be overridden manually; an overridden name shall be flagged as such and is the only case in which a stored string survives regeneration.

Out of scope (defined at the design level, never encoded in the name)

• Via spans (blind/buried layer pairs) - the span is a design property, not pad stack identity.
• Plane clearances and thermal parameters at their drill-based defaults (see the Land Pattern Creation Guide tables); only deviations are encoded (Section 8).
• Pad stacks without any copper land. On a padless mounting hole, internal pads, mask openings and paste are never encoded (a diagnostic is raised); a keepout (_OBS) may still be stated.
• Solder mask tenting/capping applied board-wide by fabrication rules rather than by the pad stack.

2 Lexical Rules

• All alphabetical characters are UPPER CASE. This applies to pad stack names, individual pad names, and hole names alike.
• Illegal characters in pad stack names, pad names, hole names and footprint names: " space , ; : / \ [ ] ( ) . { } * & % # $ ! @ ^ = - footprint names obey the same character rules, so an SU_ name can never inherit an illegal character.
• There is no maximum name length. Any limit imposed by a target system is enforced at export with a diagnostic, never by truncation.

Units, digits and rounding
Every dimension is stated in micrometres, zero padded to a minimum of four digits; a value requiring more than four digits is written at its natural width. Dimensions are rounded to the nearest whole micrometre (halves away from zero) before naming, working from the decimal value as authored (never from a binary floating-point representation, which can carry 1.0005 mm to 1000 instead of 1001). Two pad stacks whose dimensions differ only below 1 um are, by design, the same pad stack for naming purposes. A pad stack that must be distinguished below that resolution is custom (SU_, Section 10).

1.500 mm -> 1500 0.860 mm -> 0860 0.90 mm -> 0900 0.050 mm -> 0050
4.00 mm -> 4000 12.00 mm -> 12000 (natural width beyond four digits)

3 Pad Stack Types

The pad stack type is part of the pad stack's identity, alongside its geometry. In Xpedition, THP/THN pad stacks occupy pin numbers in the footprint; MHP/MHN mounting holes and V vias do not, and vias are not footprint pins at all. Identical artwork used as a pin, a mounting hole, or a via is therefore three different pad stacks, and their names differ by prefix. This is intended and deterministic: type is an input to the name, not an inference from geometry.

A ring or donut is not a type of its own. Any land of a surface mount, fiducial, THN or MHN pad stack may carry a subtracted inner form (Section 6); the type prefix is unchanged.

4 Orientation Frame and Dimension Order

All layers are assumed co-oriented; any pad stack whose layers are not co-oriented is custom (SU_).

Every pad stack has one local frame: the copper land's long axis defines X. If the copper land is equiaxed (circle, square), the slot's long axis defines X; if there is neither, the pad stack is symmetric and the frame is immaterial. Every dimension pair in the name - copper, mask, paste, inner pads, slots, offsets - is stated in this frame, X extent first. For the copper land itself this reduces to the familiar rule: the longest edge is presented first. Every other layer is stated in the copper frame even when its own long axis lies along Y; it is never re-sorted. A slot lying across a non-equiaxed land is stated the same way: THP1000X3000R4000X2000 is a slot perpendicular to the land, and is a valid, distinct pad stack. Only when the copper is equiaxed does the slot define X, and the slot is then stated long-first.

5 Name Grammar (Normative)

Every generated name matches this grammar. Anything the grammar cannot express is custom (SU_).

NAME := SMD | HOLED | FIDUCIAL | CUSTOM
SMD := 'S' LAND
HOLED := ('THP'|'V') HOLE FORM | 'MHP' HOLE [ FORM ] | 'THN' HOLE LAND | 'MHN' HOLE [ LAND ]
FIDUCIAL := 'FID_' SMD
CUSTOM := 'SU_' FOOTPRINT-NAME [ '_' n ]
LAND := FORM [ 'ID' FORM ] (second FORM is subtracted - a ring; Section 6)
FORM := SHAPE DIM [ 'X' DIM ] | 'RCS' DIM 'X' RADIUS | 'RCR' DIM 'X' DIM 'X' RADIUS
SHAPE := 'C' | 'S' | 'R' | 'B' | 'F'
HOLE := DIM [ 'X' DIM ] (second DIM = slot, frame order)
DIM := digits, micrometres, >= 4 digits, zero padded
NAME := NAME MODIFIER* MODIFIER := '_' TOKEN [ VALUE ]
VALUE := [ SHAPE-LETTERS ] DIM [ 'X' DIM [ 'X' RADIUS ] ] [ 'ID' FORM ]
            (unless stated otherwise; a subtracted value always carries its shape letters)

Modifier order (Section 8): class 1 layer/size, class 2 paste, class 3 mask, class 4 thermal, class 5 miscellaneous; within a class, in the order listed in this document; top-side tokens before bottom-side tokens. _1TO1 stands alone in place of classes 1-3.

6 Land Shapes

The square rule
When a four-sided land's sides are equal, the square form is mandatory: S rather than R, and RCS rather than RCR. An equal-sided rectangle spelling is invalid. This applies everywhere a shape appears: the land, and every modifier callout. Likewise an oblong whose two extents are equal is a circle and shall be named C. A shape letter that contradicts its dimensions - a circle or square given two different extents, a rectangle given one - is not repaired; such input is unencodable (Section 10) and raises a diagnostic.

Chamfered corners and any corner treatment other than RCS/RCR are custom (SU_). Radius corners that form full obrounds are B; a land rounded on one end only is F.

Subtracted lands - rings, donuts and crush rings
Any land may be a ring. The outer form is named exactly as a full shape would be, and the inner form removed from it follows immediately after ID, in the same frame and with its own shape letters and radius. Nothing else about the pad stack changes: the type prefix, the modifiers and the standard test all apply to the outer form as usual. A subtraction is copper geometry, not a deviation, so it never affects standardness.

LAND := FORM [ 'ID' FORM ]
THN0700C3485IDC1200 crush ring: 0.70 non-plated hole, ring 3.485 outside / 1.200 inside
MHN3300C6000IDC4000 non-plated mounting hole with a copper ring
SRCR5000X4000X0200IDRCR4600X3600X0100 surface mount RF shield: 5.000 x 4.000 ring, 0.200 wall
SC2250IDC1850 surface mount circular ring

Where it applies: surface mount, fiducial, THN and MHN. On plated types (THP, MHP, V) a subtraction would separate the barrel from its ring; it is unencodable (Section 10).

Constraints: the inner form lies wholly inside the outer form and, on holed types, wholly outside the hole; anything else is contradictory input (Section 10). Both forms obey the square rule (IDS, IDRCS) and are stated in the frame set by the outer form; the inner form is never re-sorted.

Mask default depends on whether the ring encloses a hole. THN and MHN: the mask pad is the solid outer form at the standard 0.100 expansion - THN0700C3485IDC1200 opens C3585 top and bottom, regardless of the inner size. Surface mount and fiducial: the mask pad follows the subtraction, expanded 0.050 per side outward and inward - the shield above opens RCR5100X4100X0200IDRCR4500X3500X0100. Both are the standard state and carry no callout.

Paste default: surface mount paste is 1:1 with the copper including the subtraction (paste on the ring only); holed types carry none, as usual.

Internal pads: a THN or MHN with a subtracted outer land has no internal pads by default. A ring wanted on the inner layers is stated with _INP and a subtracted value: THN0700C3485IDC1200_INPC3485IDC1200.

Modifier values: a subtracted value always carries its shape letters (THN0700C3485IDC1200_SSMC3585IDC1100), never bare dimensions. Individual pad names carry the full form (Section 11).

7 Default Values and the Standard Pad Stack

The standard pad stack
A pad stack is standard when its internal pads, solder paste and solder mask all follow the defaults above. A standard pad stack carries no class 1, 2 or 3 modifier and no _1TO1; class 4 and 5 modifiers (thermal, offset, tolerance and the rest) do not affect standardness. Equivalently: the presence of any layer, paste or mask modifier - including _1TO1 - marks the pad stack non-standard, and any reported standard/non-standard status shall be derived from exactly this test, so the name and the status can never disagree.

8 Modifiers

A modifier is appended when, and only when, a layer deviates from its default. Values follow the modifier directly: an optional shape letter (mandatory when the shape differs from the land - the Shape Deviation rule), then dimensions in frame order, then a corner radius where the shape has one. A value may itself be a subtracted form (Section 6), in which case its shape letters are mandatory. Modifiers apply to every pad stack type.

Class 1 - layer and size

Class 2 - solder paste

Class 3 - solder mask (canonical spellings)

Each side's mask opening is in exactly one state: Default, None, or Specified. The canonical encoding for every combination is fixed - no state has two spellings:

Via caps are a distinct physical layer (cap artwork applied after fabrication) and compose with the states above: _CAPT[geom] / _CAPB[geom].

_1TO1
_1TO1 states that the pad stack's major layers are all the same size AND the same shape AND the same corner radius (and the same subtraction, if any) as the top copper land. The layer set depends on the type: for surface mount - top copper, top paste, top mask; for holed types - top copper, top paste, top mask, internal pads, bottom copper, bottom paste, bottom mask. When _1TO1 applies it appears alone, in place of classes 1-3; when any layer in the set deviates from the others, _1TO1 does not apply and each deviation is called out individually.

Class 4 - thermal and plane

Tie count and angle other than the default 4 at 45 degrees are not encoded; such pad stacks are custom (SU_). The thermal shape letters TC TS TB TR name the relief pads themselves in individual pad names (Section 11).

Class 5 - miscellaneous

Applicability by pad stack type
A modifier may only be applied to the types listed for it. A modifier applied to any other type, or a pair of mutually exclusive attributes both set (for example buried and relief together), is unencodable: the pad stack is custom (Section 10) and a diagnostic is raised. Nothing is silently dropped.

Modifier order - complete

1. _INP (layer and size)
2. _NSP | _SSP | _TSP then _BSP (paste)
3. _NSM | _SSM | _TSM | _BSM | _STM then _SBM, then _CAPT then _CAPB (mask)
( _1TO1 stands alone in place of classes 1-3 )
4. _BTH | _THRM, then _A, _G, _T (thermal)
5. _BOT, _OFF, _TOL, _VT, _OBS, _PCH, _PFIT, _UV, _BWT (miscellaneous)
Within a class: exactly the order listed above. Top before bottom, always.

9 Worked Examples by Type

Surface mount

Through hole (footprint pins)

Vias (not pins; span in the design)

Mounting holes (not pins)

Fiducials

A fiducial name is FID_ followed by a complete surface mount name. Fiducial defaults: mask +0.100 as usual, no solder paste. Deviations are called out exactly as for any surface mount pad stack; keepouts via _OBS.

Custom pad stacks (SU_)
The only custom format is SU_<FOOTPRINT NAME>. Footprint names are unique, so no collision is possible. When a footprint needs exactly one custom pad stack, the name carries no suffix. When it needs more than one, the first receives _1, the next distinct one _2, and so on - assigned in ascending pin order of first appearance, pins ordered natural-sort (A2 before A10). Two pins whose custom pad stacks are identical in geometry across every layer share a number; pad stacks that differ in any way receive different numbers. Rebuilding the same footprint always yields the same names.

10 The Custom Escape (Normative Catch-All)

Anything the grammar of Section 5 cannot express is custom and shall be named SU_ per Section 9 - notably: non-co-oriented layers; corner treatments other than RCS/RCR; asymmetric top/bottom lands; non-default thermal tie count or angle; sub-micrometre distinctions; per-inner-layer pad differences; a modifier applied to a type it does not apply to; contradictory or malformed input (a shape letter that contradicts its dimensions, mutually exclusive attributes both set, a tolerance without its plus value); a subtraction on a plated type (THP, MHP, V), or an inner form that does not lie wholly inside the outer form and outside the hole; and any construct added to the library that this document does not define. This rule is what makes the convention collision-free: no unencodable attribute is ever silently dropped.

11 Individual Pad and Hole Names

Individual pad and hole names follow the same lexical rules as pad stack names: upper case, no spaces, no periods, micrometre four-digit dimensions.

Pads
Surface mount: remove the leading S from the pad stack name; the result names the copper pad. The default mask pad reflects the expanded dimensions in the same format. Thermal relief pads use TC TS TB TR + dimensions. A subtracted land's pad names carry the full form, including the subtraction; the mask pad of a THN/MHN ring is the solid outer form.

SR0860X0250 -> copper pad R0860X0250, mask pad R0960X0350
SS3500 -> copper pad S3500, mask pad S3600
SRCS2500X0050 -> copper pad RCS2500X0050
SC2250IDC1850 -> copper pad C2250IDC1850, mask pad C2350IDC1750, paste pad
C2250IDC1850
THN0700C3485IDC1200 -> copper pad C3485IDC1200 (outer layers only), mask pad C3585, hole RND0700N

Holes
Hole names are RND (round) or SLT (slot) + dimensions + plating letter P/N, with _TOL appended for a non-default tolerance in the Section 8 format.

RND0900P 0.90 mm plated round hole, default tolerance
RND0400P_TOL0050 0.40 mm plated, +/-0.050 tolerance (single value = symmetric)
RND3200N 3.20 mm non-plated
SLT3000X1000P 3.000 x 1.000 plated slot, frame order

12 Footprint Naming

Footprint names follow IPC-7351 conventions where applicable, with the L / N / M material condition suffixes for IPC nominal land patterns, the Q suffix plus manufacturer prefix and case code where the manufacturer-recommended footprint replaces an IPC one, and manufacturer prefix plus case code directly for non-IPC and RF parts. Footprint names obey the same illegal-character rules as pad stack names (Section 2). This section is unchanged from Revision 1 and is restated in full in the Land Pattern Creation Guide.

SOT23-5P95_290X280X145L45X40N IPC nominal, N material condition
SOT23-5P95_290X280X145L45X40Q_TI_DBV0005A manufacturer-recommended, Q suffix
TI_RRX0029B non-IPC / RF: manufacturer + case code