Through-Hole Reflow (THR) Technology in RJ45 Connector Design

Introduction: What is THR (Through-Hole Reflow)?

Through-Hole Reflow (THR), sometimes called Pin-in-Paste, is a hybrid PCB mounting technology that combines the mechanical strength of traditional Through-Hole Technology (THT) with the automation benefits of Surface-Mount Technology (SMT). It allows components with through-hole leads—like RJ45 connectors—to be mounted using standard SMT reflow soldering processes, eliminating the need for separate wave soldering steps.

This technique is increasingly used in high-reliability applications where signal integrity, mechanical stability, and production efficiency are critical.

How THR Works

In the THR assembly:

• Components with specially designed through-hole pins are inserted into plated-through holes filled with solder paste.
• During reflow soldering, the paste melts and solidifies, anchoring the leads firmly into the PCB.
• No wave soldering is required, enabling full SMT-compatible production lines.

This approach bridges the gap between high mechanical stress requirements and efficient automated production.

Key Advantages of THR in RJ45 Connectors

1. Enhanced Mechanical Strength

RJ45 connectors often endure cable insertion/extraction forces. THR provides superior anchoring compared to SMT-only solutions.

2. SMT Line Compatibility

THR parts can go through reflow soldering, allowing RJ45 connectors and SMT components to be assembled in a single pass.

3. Improved Reliability in Harsh Environments

Ideal for industrial, telecom, or automotive Ethernet applications where vibration or shock may dislodge weaker joints.

4. Reduced Process Complexity

By removing the wave soldering stage, THR simplifies the manufacturing process, especially for mixed-technology boards.

Design Guidelines for THR-Compatible RJ45 Connectors

To maximize THR benefits, engineers should consider:

• Solder Paste Volume Control: Ensure the correct solder volume is deposited into the PTH (Plated Through Holes).
• Thermal Profile Optimization: Adjust reflow profiles to ensure complete solder joint formation without voids.
• Pin Design: Use connectors with long, narrow, solderable leads designed to retain solder paste (e.g., eye-of-the-needle pins).
• PCB Pad Layout: Maintain proper annular ring dimensions and paste mask openings following IPC standards.

LINK-PP THR RJ45 Example: LPJG0926HENLS4R

One exemplary THR solution is the LPJG0926HENLS4R by LINK-PP. This integrated RJ45 connector is specifically designed for Through-Hole Reflow processes and offers:

• Integrated magnetics for 10/100/1000Base-T Ethernet
• Robust plastic housing with reinforced THR leads
• Minimum 350μH OCL at 8mA, ensuring signal integrity
• RoHS-compliant and halogen-free
• Fully compatible with SMT reflow ovens
• LPJG0926HENLS4R.pdf

This product is ideal for high-volume, mechanically demanding Ethernet applications, such as managed switches, routers, PoE devices, and embedded network modules.

THR vs SMT vs THT: Quick Comparison

• Industrial Ethernet Controllers
• Automotive Infotainment Systems
• Smart Grid & Energy Metering
• Medical Device Networks
• 5G Baseband and Radio Units

Final Thoughts

As PCB designs become denser while performance and durability demands rise, THR technology stands out as a modern, reliable, and efficient solution. For engineers designing with Ethernet connectivity in mind, using THR-compatible RJ45 connectors like LINK-PP’s LPJG0926HENLS4R offers a way to meet both mechanical and manufacturing goals without compromise.

To explore LINK-PP’s full range of RJ45 solutions, including THT, SMT, and THR options, visit www.rj45-modularjack.com.