Soft SMD Contacts: Comparing 5 Internal Structures for EMI Grounding

f you've already read our guide, What Is an SMT EMI Shielding Gasket?, you know that Soft SMD Contacts are reflow-solderable EMI grounding components designed for automated SMT assembly.

What many engineers don't realize is that Soft SMD Contacts are not a single product category. They encompass five distinct internal structures, each with different manufacturing methods, compression characteristics, temperature resistance, and long-term reliability.

Selecting the wrong structure can lead to assembly issues, cracking after reflow soldering, insufficient grounding performance, or premature mechanical failure.

This guide provides a detailed comparison of all five Soft SMD Grounding Contacts structures and explains how to choose the right solution for your application.

Quick Comparison of the 5 Soft SMD Contact Structures

Why Soft SMD Contacts Are Different from Traditional EMI Gaskets

Unlike conventional adhesive-backed EMI gaskets, Soft SMD Contact Pads are designed to be mounted directly onto PCB assemblies through reflow soldering.

The silicone-based internal structure enables them to withstand temperatures exceeding 260°C while maintaining elasticity and stable electrical contact.

For engineers comparing traditional fabric-over-foam solutions with SMT grounding technology, our article Fabric Over Foam Gaskets: Why FOF Remains the Best Value EMI Solution provides a detailed overview.

Type 1: Extruded Silicone Core Wrapped Structure

Construction

This design consists of an extruded silicone strip (solid or hollow) wrapped with conductive PI film or conductive metal foil.

It is the earliest and most widely used Soft SMD Grounding Contact structure in the industry.

Advantages

• Custom D-shape, P-shape, rectangular, and other profiles
• Excellent dimensional accuracy
• Tolerance can reach ±0.15 mm
• Miniaturized designs as small as 1.2 mm × 1.2 mm
• Excellent balance of cost and performance

Limitations

• Conductive layer may crack under excessive lateral force
• Hollow structures require careful wall-thickness design
• Wrapping process is relatively complex

Best Applications

• Consumer electronics
• Communication modules
• PCB grounding
• General EMI shielding designs

For a broader understanding of conductive foam technologies, see: What Is EMI Foam? A Complete Guide to EMI Foam

Type 2: Open-Cell Silicone Foam Wrapped Structure

Construction

This structure uses specially processed open-cell silicone foam wrapped with conductive PI film.

The porous internal structure significantly reduces compression force while maintaining grounding performance.

Advantages

• High compression capability
• Low actuation force
• Multiple density options
• Easier manufacturing than Type 1

Limitations

• Only rectangular cross-sections
• Minimum thickness typically around 3 mm
• Potential tilting under high compression

Best Applications

• Thin consumer electronics
• Displays
• Lightweight devices sensitive to compression force

Type 3: Standard Silicone Foam Wrapped Structure

Construction

Conductive PI film is wrapped around conventional silicone foam without open-cell modification.

Advantages

• Lowest manufacturing cost
• Extremely thin designs (<0.3 mm)
• High compression with low force

Limitations

• Rectangular profiles only
• Significant thickness variation
• Thermal expansion may cause seam cracking
• Not suitable for reflow soldering

Best Applications

• Adhesive-mounted EMI gaskets
• Cost-sensitive projects
• Non-SMT assemblies

Type 4: Extruded Foamed Silicone Sponge Wrapped Structure

Construction

Foamed silicone sponge is produced through extrusion and then wrapped with conductive PI film.

A unique feature is the ability to create "waist-shaped" anti-tilt geometries.

Advantages

• Improved resistance to side collapse
• Better structural stability under compression
• Some profile customization capability

Limitations

• Thermal expansion can still cause seam cracking
• Relatively large dimensional tolerances
• Less commonly used in the market

Best Applications

• Vertical grounding structures
• Applications requiring anti-tilt performance

Type 5: Extruded Conductive Silicone Structure

Construction

Instead of wrapping conductive film around the silicone core, conductivity is integrated directly into the silicone surface through coating or co-extrusion processes.

A conductive metal base is added for soldering.

Advantages

• Highest resistance to compression damage
• Excellent fatigue performance
• Long-term durability
• Fully customizable shapes
• Suitable for repeated opening and closing cycles

Limitations

• Slightly higher contact resistance
• Higher manufacturing cost
• Surface conductivity layer may wear over time

Best Applications

• Frequently compressed devices
• Sealing plus grounding requirements
• Industrial and automotive electronics

For engineers evaluating grounding reliability, our article on PCB grounding solutions provides additional insights: SMT EMI Gasket vs Conductive Foam for PCB Grounding

Selection Guide for Soft SMD Contact Pads

Step 1: Will the part go through reflow soldering?

Yes
→ Choose Type 1, 2, 4, or 5

No
→ Type 3 becomes a cost-effective option

Step 2: Is a custom cross-section required?

Yes
→ Choose Type 1 or Type 5

No
→ All structures remain viable

Step 3: Is frequent compression expected?

Yes
→ Type 5 is recommended

No
→ Continue evaluation

Step 4: Is low compression force critical?

Yes
→ Type 2 is preferred

No
→ Type 1 offers the best overall balance

Performance Comparison

Frequently Asked Questions

What is the biggest difference between Soft SMD Contacts and fabric over foam gaskets?

The key difference lies in both materials and mounting methods.

Soft SMD Contacts use silicone-based cores that can survive reflow soldering temperatures up to 260°C and are soldered directly onto PCB assemblies.

Fabric over foam gaskets typically use PU foam or PORON cores and are attached using pressure-sensitive adhesive tapes.

For a deeper comparison of conductive foam technologies, see: Conductive Foam Gasket vs Conductive Fabric: Key Differences Explained

Can Soft SMD Grounding Contacts replace beryllium copper spring contacts?

In many applications, yes.

They offer:

• Better elasticity
• Improved shock absorption
• Lower risk of mechanical fracture
• Easier automated assembly

However, final selection should still consider operating frequency, contact resistance requirements, and available installation space.

How are Soft SMD Contact Pads manufactured?

The production process typically includes:

1. Silicone extrusion or foaming
2. Conductive PI film wrapping
3. Terminal fabrication
4. Automated inspection
5. Carrier tape packaging

Advanced production lines integrate these processes into a highly automated workflow to ensure consistent quality and dimensional accuracy.

About Konlida

Founded in 2006, Suzhou Konlida Precision Electronics is one of the earliest manufacturers to mass-produce Soft SMD Contacts in China.

Our capabilities include conductive PI film development, silicone extrusion, automated wrapping, SMT terminal fabrication, and carrier tape packaging. We supply all five Soft SMD Grounding Contacts structures and provide engineering recommendations based on compression force, operating temperature, durability requirements, and anti-tilt performance.

Certified to IATF 16949 and ISO 13485 standards, Konlida supports demanding automotive, medical, industrial, and consumer electronics applications worldwide.