calc.engineer

pcb via current

pcb_via_current

Calculate PCB via current-carrying capacity using the IPC-2221 standard. A plated via is a hollow copper cylinder whose cross-sectional area is the annular ring of plating: A = pi * (D - t) * t, where D is the drill diameter and t is plating thickness. The IPC-2221 empirical formula I = k * dT^0.44 * A^0.725 (k=0.048) then gives the maximum current for a given temperature rise. Also computes via barrel resistance from copper resistivity (1.724e-6 ohm-cm) and barrel length (board thickness). When a target current is specified, returns how many parallel vias are needed. Essential for power planes, high-current paths, and thermal via arrays. Chain with trace_width to verify both trace and via can handle the same current.

Input Schema

TableJSON Schema

Name	Required	Description
`temp_rise_c`	No	Allowable temperature rise above ambient in degrees Celsius. IPC-2221 standard uses 10, 20, or 30 C.
`target_current_a`	No	Optional target current in amperes. When provided, calculates how many parallel vias are needed to carry this current safely.
`drill_diameter_mm`	No	Via drill hole diameter in millimeters. Common values: 0.2 (microvia), 0.3 (standard), 0.4, 0.6, 0.8, 1.0.
`board_thickness_mm`	No	Total PCB board thickness in millimeters. Standard 2-layer is 1.6 mm. Common values: 0.8, 1.0, 1.6, 2.0, 2.4.
`plating_thickness_um`	No	Copper plating thickness on the via barrel wall in micrometers. Standard is 25 um (IPC Class 2). Heavy plating is 50 um (IPC Class 3).

Output Schema

TableJSON Schema

Name	Required	Description
`vias_needed`	Yes	Number of parallel vias needed for the target current. Null if no target_current_a was provided.
`max_current_a`	Yes	Maximum current capacity of a single via at the specified temperature rise, in amperes.
`resistance_mohm`	Yes	DC resistance of the via barrel in milliohms, calculated from copper resistivity and barrel length.
`voltage_drop_mv`	Yes	Voltage drop across the via at maximum rated current in millivolts.
`cross_section_mm2`	Yes	Copper cross-sectional area of the via barrel annulus in square millimeters.
`cross_section_mil2`	Yes	Copper cross-sectional area of the via barrel annulus in square mils.
`power_dissipation_mw`	Yes	Power dissipated in the via at maximum rated current in milliwatts.

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description fully carries the burden. It explains the mathematical formulas, how parameters are used, and additional outputs like barrel resistance and parallel via count. No contradictions or missing behavioral traits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is moderately long but well-structured with front-loaded purpose. Every sentence adds value, though some technical details could be slightly condensed. No waste.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With all parameters described in schema, an output schema present, and the description covering outputs (current, resistance, parallel vias) and chaining with trace_width, the tool definition is complete for its complexity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so baseline is 3. The description adds value by explaining the formulas and relationships between parameters (e.g., cross-sectional area formula). This provides context beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states it calculates PCB via current-carrying capacity using the IPC-2221 standard, specifying the formula and outputs. It distinguishes itself from sibling tools like trace_width by mentioning chainability.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides context on when to use (power planes, high-current paths, thermal via arrays) and suggests chaining with trace_width. It does not explicitly state when not to use, but the purpose is clear enough.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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TDQS

A3.9/5.0

Disambiguation4/5

Despite 89 tools, each has a clearly distinct purpose with detailed descriptions that often reference related tools. Overlap exists (e.g., multiple LoRa/RF tools), but the descriptions are sufficient to distinguish them. Some confusion possible among similar-sounding tools like attenuator_pi and attenuator_tee, but the descriptions explicitly compare them.

Naming Consistency4/5

Consistent underscore-separated lowercase naming. Most tools follow a verb_noun pattern (e.g., capacitor_charge, wire_gauge) or noun_noun (power_cost). Minor inconsistencies such as 'bmi_calculator' vs 'solar_sizing' but overall predictable.

Tool Count2/5

89 tools is far too many for a single MCP server. This scope is more appropriate for multiple specialized servers. The sheer number will slow agent selection and increase cognitive load, reducing coherence.

Completeness3/5

Covers many domains (RF, solar, PCB, networking, math, etc.) but lacks depth in some areas (e.g., no three-phase power, no airflow calculations). Some domains have comprehensive coverage (LoRa/Meshtastic), but others feel incomplete for the tool count.

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