Selection Guidance by Material, Diameter, and Load Capacity

Standoffs are essential mechanical components in electronics assembly. Whether in device construction, control boards, or industrial electronic enclosures, they ensure defined spacing between printed circuit boards, housing parts, or heat sinks while providing mechanical stability and electrical safety.

The selection of the right standoff depends on several factors: mechanical load, material requirements, design, mounting method, and dimensional accuracy. Especially in series production or safety-critical applications such as control cabinet construction or power electronics, the right choice determines functionality and reliability.

This article provides you with technical guidance for selecting suitable standoffs - tailored to the requirements of modern PCB applications.

Functions and Areas of Application of Standoffs

Standoffs perform several technical functions at once: they mechanically stabilize the PCB assembly, create thermal spacing from hot components or housing surfaces, and, when required, ensure electrical insulation through non-conductive materials. At the same time, they enable precise fixing and positioning during manufacturing and maintenance.

Depending on the application, they must withstand vibrations, compensate for thermal expansion, or provide precise guidance. In many cases, they also serve as a permanent mounting solution - for example when press-fitted into housings or screwed onto carrier plates. In EMC-critical applications, metallic standoffs additionally contribute to shielding by establishing a defined ground connection between the PCB and the housing.

The 4 Most Important Selection Criteria for Standoffs

1. Material: Electrically, Mechanically, and Thermally Decisive

The choice of material affects not only mechanical strength but also electrical and thermal properties. Depending on environmental conditions - such as humidity, chemical exposure, or temperature - a targeted selection is recommended.

Electrical Insulation Properties of Common Plastics

• PA6/PA66: Dielectric strength approx. 20–25 kV/mm
• POM: approx. 18–20 kV/mm
• PPS: approx. 22–25 kV/mm (continuous use up to 200°C)
• PEEK: approx. 20 kV/mm (continuous use up to 240°C, for high-temperature applications)

For PCBs in sensitive environments, PA or POM standoffs with high insulation performance are often the first choice. For outdoor applications or aggressive media, stainless steel A4 (V4A) is recommended for maximum corrosion resistance.

2. Diameter, Thread Size, and Load Capacity

Mechanical stability largely depends on diameter and thread size. Typical combinations in practice are:

Important: For dynamic loads (vibration, shock), a safety factor of at least 2.5 should be applied. For applications according to DIN EN 60068-2-6 (vibration testing), we recommend metal standoffs with mechanical locking.

Rule of thumb for dimensioning: The higher the mechanical load or the larger the PCB, the larger the standoff diameter should be. For PCBs larger than 200 × 200 mm, we recommend at least M4 fasteners at the corners.

For particularly fine applications, snap-in standoffs or unthreaded spacers are also suitable - for example in confined spaces or where only passive spacing is required. These are especially suitable for prototyping and frequent disassembly.

3. Length of the Standoff (Spacing Height)

The length determines the vertical distance between PCBs or to the mounting surface. Standard lengths range from 3 mm to 50 mm; special lengths up to 100 mm are available.

Calculation formula for the required length:
Standoff length = PCB thickness + tallest component + safety clearance (min. 2–3 mm) + optional thickness of a second PCB

Important considerations:

• Component heights on the PCB (e.g., electrolytic capacitors, inductors, connectors)
• Air space for heat dissipation or air circulation in actively cooled systems
• Minimum clearance to avoid arcing in high-voltage applications according to IEC 61010-1
• Creepage distances on the PCB according to IPC-2221

For double-deck PCBs, planning with coordinated lengths and an even support pattern is recommended to avoid bending loads. As a rule of thumb: one mounting point every 100–150 mm for standard PCBs (FR4, 1.6 mm).

Practical example: A control board (1.6 mm thick) with 25 mm tall electrolytic capacitors requires standoffs of at least 30 mm length (1.6 + 25 + 3 mm safety = 29.6 mm → standard length 30 mm).

4. Mounting Method: Thread Type and Assembly Technique

Standoffs are available in various designs that differ in mounting technique and application area:

Thread variants:

• Internal thread on both sides (e.g., M3/M3): universally applicable, ideal for service applications
• External/internal thread combination: one side fixed, the other as a receptacle
• External thread on both sides: for direct fastening, particularly space-saving
• Snap-in connections: tool-free mounting in plastic housings or pre-drilled carrier plates
• Press-fit standoffs: for automated assembly, process-safe from medium volumes onward

Relevant standards for standoffs:

• DIN 7964: Standoffs with internal threads (both sides)
• DIN 7965: Standoffs with external and internal threads
• IPC-2221: Minimum clearances and mounting points on PCBs
• IEC 61010-1: Clearance and creepage distances in safety-relevant applications

For series production, selection should also consider assembly technique: press-fit or snap-in systems reduce screw fastening effort and are suitable for high volumes, while screw-mounted variants are preferred for service or laboratory systems.

Cost efficiency in series: For small batches (< 100 units), standard off-the-shelf standoffs are usually the most economical solution. From medium volumes (> 500 units), custom variants or press-fit systems can reduce assembly costs by up to 30% by eliminating screw operations and increasing process reliability.

Practical Application Examples

Embedded System in an Industrial PC

In a project for a machine builder, we used M3 brass standoffs (length 12 mm, outer Ø 6 mm, nickel-plated, internal threads on both sides) to mount the main board on an aluminum carrier. The thermal spacing allowed heat dissipation of approx. 15 W via the heat sink without additional insulation. The good electrical conductivity also ensured a continuous ground connection.

Device Construction with Display Module

PA6 snap-in standoffs (Ø 6 mm, length 8 mm) were used for insulated spacing of a capacitive touch module. The low-vibration snap-in mounting enabled tool-free assembly and reduced assembly time by 40% compared to screw connections. At the same time, electrical insulation prevented interference with the capacitive sensing.

Power Electronics Module in a Control Cabinet

Stainless steel A2 standoffs with M4 × 20 mm were used for secure mounting on a DIN rail - designed for high thermal loads (up to 120°C continuous temperature) and mechanical requirements (vibration class according to DIN EN 60068-2-6). The corrosion resistance ensures a service life of over 15 years even in humid industrial environments.

Multi-Layer Sensor Platform

A combination of standoffs and spacers in various lengths (6 mm, 12 mm, 18 mm) was used to build defined levels with different signal processing modules. Using POM standoffs ensured complete galvanic isolation between levels - important for avoiding ground loops in analog signal processing.

Common Assembly Errors and How to Avoid Them

• Standoffs too short: Component heights are underestimated, leading to mechanical stress or short circuits. Solution: Plan at least 2–3 mm safety clearance above the tallest component.
• Over-tightening: Plastic standoffs may crack or the PCB may be damaged. Solution: Observe tightening torque (typical for M3/PA6: max. 0.5 Nm; for M3/brass: max. 1.2 Nm).
• Missing washers: Soft PCBs or large holes can lead to pressure marks or board breakage. Solution: Use washers, especially for single fastenings and FR4 boards under 1.6 mm thickness.
• Too few mounting points: Large boards may bend, causing solder joint cracks or component damage. Solution: Rule of thumb: one support point every 100–150 mm; add extra fixation for heavy components.
• Insufficient EMC grounding: Metal standoffs without adequate contact pressure to ground. Solution: Use spring or serrated washers for defined contact; consider conductive gaskets.

EMC Considerations in Selection

In EMC-critical applications, metallic standoffs (brass, stainless steel, aluminum) can contribute to shielding by establishing a defined ground connection between the PCB and the housing. Good electrical contact is essential - using serrated washers or conductive gaskets significantly improves HF coupling.

For applications according to EN 55011 or EN 55032 (EMC standards for industrial equipment), at least four ground points evenly distributed across the PCB are recommended. The contact resistance between PCB and housing should be below 10 mΩ - this can be achieved with gold-plated contact areas or EMC gaskets.

For high-frequency applications (> 1 GHz), short standoffs (< 10 mm) are recommended to minimize inductive effects. Combined with via stitching on the PCB, this creates an effective HF ground connection.

When Is a Custom Solution Sensible?

In special cases - such as confined installation spaces, extreme temperatures (< -40°C or > 150°C), or special mounting situations - a customized solution may be necessary. Material selection, dimensional tolerances, hole diameters, or specific insulation requirements are key factors.

Typical special cases include:

• Standoffs with integrated functions (e.g., built-in thread for grounding connection)
• Hybrid solutions combining metal and plastic for partial insulation
• Special lengths or diameters for PCBs with unusual hole patterns
• Materials for vacuum applications or cleanroom environments (e.g., PEEK, PTFE)
• Color coding or markings for identification in complex assemblies

For such applications, Quick-Ohm offers not only a broad stock range of over 250 standard variants but also technical consulting for selecting or developing special standoffs - including standards comparison, drawing creation, and sampling.

Direct to the Products

You can find the complete range of standoffs in various materials (brass, stainless steel, PA6, POM, PPS, aluminum), lengths (3–100 mm), and designs (internal thread, external thread, snap-in, press-fit) in our online shop:

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Need Help with Selection?

We are happy to support you with the technical design of your standoffs - whether for a new development, optimization of existing mounting structures, or conversion to automated manufacturing processes.

Our applications engineering team provides manufacturer-independent, solution-oriented, and practical advice on:

• Material selection considering thermal and electrical requirements
• Dimensioning based on mechanical loads
• Compliance with standards (DIN, IEC, IPC)
• Cost optimization in series production
• Development of customer-specific special solutions

Talk to our application engineers - we support you from the initial concept phase through to series production.

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