# Component Orientation and Polarity Rules for Assembly

**URL:** <https://community.aisler.net/t/component-orientation-and-polarity-rules-for-assembly/45>\
**Category:** 🔎 Design Rules\
**Created:** [August 10, 2023, 10:00pm UTC](https://community.aisler.net/t/component-orientation-and-polarity-rules-for-assembly/45 "2023-08-10T22:00:00Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Thea](https://community-cdn.aisler.net/user_avatar/community.aisler.net/thea/32/1177_2.png) [@Thea](https://community.aisler.net/u/Thea)\
**Post date:** [August 10, 2023, 10:00pm UTC](https://community.aisler.net/t/component-orientation-and-polarity-rules-for-assembly/45/1 "2023-08-10T22:00:00Z")

</div>

# Polarity Detection for Assembly

This article explains how we interpret and display part polarities and what you can do to comply with our polarity rules.

> **Important:** This article is **mainly relevant if you’re planning to use our assembly service**.  
> If you’re only ordering PCBs or stencils, you can proceed with your order without considering this information.

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# Quick Summary

- **Before ordering** : Please ensure that the polarity marker of each polarized component points to the correct pad.
- **For components with 3 or more pads** : The polarity marker must point to **Pad 1** or **A1**.
- **For components with 2 pads** : Orientation and polarity are based on the **designator prefix** (e.g., C, D, LED), **pad names** , and your **EDA tool**.
  - For **diodes** , the marker points to the **cathode**.
  - For **capacitors** (including tantalum), it points to the **negative pole**.
  - See **Table 1** below for more details.

- Components not covered by these rules are not auto-detected.
- Symmetric components **without a marker** will be placed without a specific orientation.
- If you’re using polarized components but no polarity marker is shown, **please contact us**.

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# Why This Matters

The correct orientation of polarized components is critical for your board to function. A reversed **resistor** may still work, but a reversed **diode** or **IC** will not.

Unfortunately, footprint libraries often do not strictly follow standards like **IPC-7351B**. Pad names and rotation values can be misleading, and silkscreen indicators are not reliable.

That’s why we’ve defined **clear polarity rules** — so that you can communicate the correct orientation of each component directly in your design data, and we can place them accordingly during assembly.

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# The Polarity Rules

This section describes the cases in which we determine a polarity and display it in the assembly view.

> ⚠ **Note:** If the polarity marker of a polarized component does not point to the correct pad (cathode / negative pole / Pin 1), please adapt the footprint accordingly — either by renaming pads or choosing a compatible footprint.

### Orientation of components with 3 or more pads

Polarity is determined **only** by the position of pad **“1”** or **“A1”**.  
The component’s reference designator is **not** evaluated.

## ![Detection of pin "1" and "A1"](https://community.aisler.net/uploads/default/original/2X/0/04ec288c803fb5e51cdef27e481b8d51b50b770d.png)

### Polarity (2 pad components)

We detect the component’s type (capacitor / diode) by evaluating the reference designator:

- Capacitors: `C#`, e.g. C1, C2, C15, …
- Diodes: `D#`, `LED#`, e.g. D1, LED5, …

Based on the component’s type, the polarity (cathode / negative pole) is determind by the **pad naming** and the used **EDA-tool**.

We follow **IPC-7351B** , with an exception for **Target3001!**.

**Table 1** : Pad naming conventions for 2-pin capacitors and diodes

| Component Type | Capacitors (`C#`) | Diodes (`D#`, `LED#`) |
| --- | --- | --- |
| | Negative pole (−) | Cathode (−) |
| **Default** | 2, - | 1 , C, K |
| **Target3001!** | 2 | 2 |

 ![Footprint polarities for 2-pin components](https://community.aisler.net/uploads/default/original/2X/7/77a25b55203484a5852a3f35f0249237dac77d2a.png)

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# Limitations and Final Check

- The system **only recognizes** the cases described above. Example: If you use a designator for a 2-pin diode like `"DIO2"` instead of `"D2"`, polarity won’t be detected.
- If a component can **only be placed in one orientation** (e.g. SOT323), a marker is not needed.
- You must ensure that **all polarized components** have a polarity marker pointing to the correct pad (cathode / negative pole / Pin 1).
- **By submitting your order, you confirm that all placements are correct.**  
See also our [Rendering Guarantee for Amazing Assembly](https://community.aisler.net/t/rendering-guarantee-for-amazing-assembly/2427).
- If your footprints **don’t comply** with our polarity rules, please get in touch — we may be able to set up a **custom detection logic**.