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Minimum Solder Mask Sliver and PCB Design

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • A minimum solder mask sliver is the minimum distance between solder mask openings that expose the copper pads on a PCB.

  • Manufacturers often set minimum solder mask sliver widths to prevent problems such as solder bridging and wicking.

  • To mitigate problems caused by minimum solder mask sliver errors, consider using design rule checks and other strategies.

Minimum solder mask slivers help prevent solder bridging and wicking

Minimum solder mask slivers help prevent problems such as solder bridging and wicking

A solder mask does more than just protect your PCB; it contributes to the accuracy and reliability of PCB assembly. Typically, the solder mask layer has openings that expose the copper pads so that components can be soldered onto the PCB. A minimum gap, or sliver, should be maintained between these openings to ensure PCB functionality and reliability. Manufacturers often set minimum solder mask sliver widths to prevent problems such as solder bridging and wicking.

A minimum solder mask sliver is the minimum distance between solder mask openings that expose the copper pads on a PCB.

The minimum sliver width depends on manufacturing tolerances and PCB fabrication capabilities. The values range from a few mils (thousands of an inch) to tens of micrometers.

To make sure the PCB functions correctly, designers and manufacturers need to follow the recommended solder mask sliver width, known as the minimum solder mask sliver design rule. The rule defines the minimum width of solder mask slivers to avoid manufacturing problems.

You can ensure the solder mask layer doesn’t interfere with the exposed copper by adhering to the minimum solder mask sliver rules. You should consult the PCB’s fabrication specifications and guidelines to determine the minimum sliver width for your particular project.

Impact of Minimum Solder Mask Sliver Errors on PCB Design

Minimum solder mask sliver errors can have a significant effect on your PCB design. For example, there is a problem known as solder bridging. If the solder mask sliver between two adjacent pads is too small, there is a risk that the solder may flow across the sliver, creating a solder bridge on top of the solder mask. This could lead to a short circuit, a trace or component burning up, or general circuit malfunctioning.

In some cases, like through-hole or surface-mount components with exposed thermal pads, solder can wick along the copper between solder mask openings if the sliver width is too small. This can result in solder joints failing and electrical connections being compromised.

In addition, making PCBs with very small solder mask slivers poses challenges during manufacturing. Higher precision and tighter tolerances are needed to ensure proper solder mask application and alignment. 

Preventing Problems With Minimum Solder Mask Slivers

Mitigating Minimum Solder Mask Sliver Errors

Manufacturing Guidelines

Follow guidelines for minimum sliver widths

Prototyping and Testing

Prototype and test design before production

Component Placement

Check the placement of components carefully

Design Rule Check

Run a DRC on your PCB design

To mitigate problems caused by minimum solder mask sliver errors, you should consider employing the following strategies:

  • Manufacturers guidelines: Manufacturers usually provide guidelines specifying the minimum allowable dimensions of solder mask slivers based on their manufacturing capabilities. Ensure you adhere to these guidelines when designing your PCB to ensure the board can be manufactured without problems.

  • Prototyping and Testing: Consider prototyping and testing your design before moving to mass production. This way, you can verify the PCB’s performance and reliability in real-world scenarios. Ensure areas with very small solder mask slivers are not causing problems during testing.

  • Component Placement: Check the placement of components on the PCB layout carefully. Identify areas where solder mask slivers are not meeting width guidelines, and move components or change routing to fix the issue. 

  • Design rule checks: Most PCB design software tools have design rule checks (DRCs) that can detect minimum solder mask sliver violations. Run a DRC on your design to find where the solder mask slivers are not meeting the manufacturer’s rules. Modify the solder mask openings or adjust the design layout to fix these violations.

By implementing these mitigation strategies, you can minimize any problems associated with minimum solder mask sliver errors and increase the overall reliability of your PCB design.

You should consider the impact of minimum solder mask sliver rules on your designs. Conforming to the manufacturer’s rules limits the negative effects of solder mask sliver errors, accelerating time-to-market for your PCB. 

Perform DRCs Early in the Design Process With Cadence’s OrCAD

Cadence’s OrCAD allows you to perform DRCs early in the design process, enabling you to catch minimum solder mask sliver errors and other problems with the PCB design. The DRC will check other physical parameters, such as trace width and spacing, via size and spacing, drill-to-board aspect ratio, and outline-to-pin pads.

When you use DRC in your design process, you’ll save time and money during production. PCB design software like OrCAD takes you through all the checks you can run. Check out Cadence’s PCB Design and Analysis Software suite today.

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