KiCad DRU generation¶
The assembly rules are authored once, in config/rule_params.json, and
evaluated by the KLayout deck on the finished assembly GDS. That is late
feedback: you learn that two chiplets sit too close only after the interposer
has been routed and converted. The KiCad DRU generator moves the one rule that
has a faithful KiCad equivalent forward into the placement editor, so the
common mistake is caught while you are still dragging footprints.
The generator is kicad/dru/generate_assembly_dru.py. It reads the same
parameter registry the KLayout deck reads, optionally merges the numeric
overrides an interposer adapter declares, and renders a block of KiCad design
rules to stdout or to a file.
Warning
The KiCad side is a partial mirror of the ADK deck, by construction. Of the 4 assembly rules exactly one is emitted, and none of the 7 interconnect rules are. A clean KiCad DRC therefore does not imply a clean assembly DRC. The KLayout deck (Running the assembly DRC) remains the check that decides.
What the generator produces¶
One self-describing section, ready to be pasted into a project’s
.kicad_dru file or appended by a larger generator. With the defaults and
no adapter:
# ============================================================================
# ADK assembly DRC rules (auto-generated)
# ============================================================================
#
# Source: adk/config/rule_params.json
#
# Coverage:
# * ASM.a (chiplet boundary overlap) -- enforced by KiCad's native
# courtyard collision check; no rule emitted here.
# * ASM.b (chiplet-to-chiplet spacing) -- emitted below.
# * ASM.e (chiplet minimum area) and ASM.f (attachment geometry inside
# chiplet) have no clean KiCad DRU equivalent and are enforced
# post-layout only by the ADK KLayout deck (adk/klayout/drc).
(rule "ASM.b - Chiplet min spacing"
(constraint courtyard_clearance (min 50um))
(condition "A.Type == 'Footprint' && B.Type == 'Footprint'"))
The coverage comment is part of the rendered output on purpose. A .kicad_dru
file travels with the project and is read by people who never see this page, so
the block states in place what it does and does not cover.
The banner line # ADK assembly DRC rules (auto-generated) opens every
render and is the marker a downstream generator can look for when it needs to
locate or replace a previously appended ADK section.
Note
The 50um in the emitted constraint is the ASM_b default. It is an
engineering default with no recorded foundry provenance, not a fab rule.
See Assembly placement rules (ASM) for what the value means and
Adapter contract for how an interposer adapter replaces it.
Coverage matrix¶
Rule |
KiCad treatment |
Why |
|---|---|---|
|
KiCad native courtyard collision check |
Overlapping chiplet boundaries are exactly what KiCad’s built-in courtyard overlap check already reports for footprints. Emitting a second rule for it would double-report the same violation, so the ADK emits none and relies on the native check being enabled. |
|
|
Chiplet-to-chiplet edge spacing maps cleanly onto a courtyard clearance between two footprints. This is the only rule with a faithful KiCad expression, and the only one the generator writes. |
|
Not mirrored, post-layout only |
Minimum chiplet area is a property of the boundary polygon recorded in the boundary manifest. KiCad has no area constraint over a courtyard, so the rule is evaluated by the KLayout deck against the manifest. |
|
Not mirrored, post-layout only |
Chiplet-attachment geometry containment is a relation between drawn interposer artwork and a chiplet boundary. The artwork does not exist in the KiCad board at all, so there is nothing to constrain there. |
|
Not mirrored, KLayout only |
The interconnect axis constrains attachment points inside a footprint, against each other and across methods. KiCad’s courtyard vocabulary has no equivalent, and the pads only acquire their as-drawn positions when the interposer is generated. See Interconnect rules (IXN). |
Passing --interconnect-adapter does not add a constraint. It appends a
provenance comment naming the adapter and restating that IXN.b and
IXN.e are enforced post-layout by 8_2_interconnect.drc:
#
# Interconnect axis: ihp_cupillar
# * IXN.b (attachment-point spacing) and IXN.e (attachment-point pitch) are
# intra-footprint bump rules with no KiCad courtyard equivalent; they are
# enforced post-layout only by the ADK KLayout deck (8_2_interconnect.drc).
With no interconnect adapter the interconnect block is skipped entirely and the output is byte-identical to what the generator produced before the interconnect axis existed.
Running the generator¶
# Defaults from config/rule_params.json, to stdout
python kicad/dru/generate_assembly_dru.py
# Merge the interposer adapter's overrides and write a file
python kicad/dru/generate_assembly_dru.py \
--interposer-adapter intm4tm2 \
--out assembly.kicad_dru
# Add the interconnect-axis provenance comment
python kicad/dru/generate_assembly_dru.py \
--interposer-adapter intm4tm2 \
--interconnect-adapter ihp_cupillar \
--out assembly.kicad_dru
Both adapter flags accept either a shortname, resolved against
pdk_adapters/interposer/ or pdk_adapters/interconnect/, or a literal
path to a .drc file. An unresolvable name fails with the two locations
that were probed.
usage: generate_assembly_dru.py [-h] [--interposer-adapter INTERPOSER_ADAPTER]
[--interconnect-adapter INTERCONNECT_ADAPTER]
[--out OUT] [--rule-params RULE_PARAMS]
Generate the ADK KiCad assembly DRU section.
options:
-h, --help show this help message and exit
--interposer-adapter INTERPOSER_ADAPTER
Interposer adapter shortname or .drc path. Numeric
drc_rules[] overrides in the adapter are merged on top
of config/rule_params.json defaults.
--interconnect-adapter INTERCONNECT_ADAPTER
Optional interconnect adapter shortname or .drc path.
Adds a provenance comment for the bump pitch/spacing
axis (IXN rules, post-layout only). Omit for
interposer-only output (identical to before this axis
existed).
--out OUT Output path. If omitted, write to stdout.
--rule-params RULE_PARAMS
Alternate rule_params.json path (default:
adk/config/rule_params.json).
Examples:
generate_assembly_dru.py # defaults, stdout
generate_assembly_dru.py --interposer-adapter intm4tm2 # adapter overrides
generate_assembly_dru.py --out assembly.kicad_dru # write to file
Append the rendered section to the project’s .kicad_dru. KiCad reads that
file per project, so the rules apply to the board you are placing chiplets on
and to nothing else.
How adapter overrides are merged¶
An interposer adapter is Ruby, read by the KLayout deck. The generator does not execute it. It scans the file line by line for complete numeric assignments of the form:
drc_rules['ASM_b'] = 75.0 # interconnect adapters use interconnect_rules[...]
and merges those on top of the JSON defaults. The narrow grammar is deliberate:
Only a complete numeric literal matches. Scientific notation (
30.0e3), Ruby underscore grouping (1_000), a unit suffix (30um) and computed expressions (30.0 + margin) do not match and are ignored, rather than being truncated to a misleading partial number.An override key that is not already a known rule is a hard error. A lowercased
asm_bwould otherwise be silently dropped and the template would emit the default, which looks like a working override and is not.A negative value is a hard error. A spacing or area constraint cannot be negative.
Comment lines are skipped.
Values are rendered as fixed-point decimals with trailing zeros stripped:
50.0 becomes 50, 30.5 stays 30.5. Scientific notation is never
emitted, because KiCad’s DRU length-literal parser cannot read it.
Tip
If an adapter expresses a rule value as a computed Ruby expression, the KLayout deck will honour it and the KiCad output will not. Keep the values an adapter intends to expose to KiCad as plain literals.
Importing the renderer¶
A per-project DRU generator should reuse the ADK renderer rather than
duplicate the rule logic. There is no installed adk package (the
directories carry no __init__.py), so put the generator’s directory on
sys.path and import the bare module, the same way the ADK’s own tests do:
import sys
sys.path.insert(0, "/path/to/adk/kicad/dru")
from generate_assembly_dru import load_defaults, render_assembly_rules
section = render_assembly_rules(load_defaults(), adapter_name="intm4tm2")
render_assembly_rules returns a string ready to append to a
.kicad_dru. Its signature is append-only:
render_assembly_rules(
rules, # dict of ASM_* values (required)
adapter_name=None, # interposer provenance label
template_dir=None, # override the template search dir
interconnect_rules=None, # IXN_* values
interconnect_adapter_name=None, # interconnect provenance label
) -> str
New options arrive as trailing keyword arguments with defaults, so an importer written against an older ADK keeps working across releases and its output does not change until it opts in.
The supporting entry points are importable too: load_defaults(path) and
load_interconnect_defaults(path) read the registries,
resolve_adapter_path(name_or_path) and
resolve_interconnect_adapter_path(name_or_path) do the shortname
resolution, and parse_adapter_overrides(path) /
parse_interconnect_overrides(path) extract the numeric overrides without
applying them.
Files¶
Path |
Role |
|---|---|
|
The generator and the importable renderer. |
|
Jinja2 template for the rendered section. Rendered with
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