The rapid growth of high-speed computing is changing the way connector manufacturers think about welding.
In the past, copper interconnects inside servers and switches were expected to carry relatively modest data loads. Today, that same infrastructure must support 400G, 800G, and even higher transmission rates for cloud computing, large-scale AI clusters, storage networks, and next-generation communication systems. Under these conditions, even a small variation in the welding process can affect contact resistance, signal integrity, and long-term reliability.
For manufacturers of DAC cable assemblies and high-speed connectors, the challenge is no longer simply joining two pieces of metal together. The real challenge is producing a precise, low-resistance connection between copper conductors and connector terminals without damaging the surrounding insulation or reducing transmission performance.
Han’s Laser developed the red-blue composite laser welding solution specifically for this type of application.
Why DAC Cable Welding Has Become More Difficult
DAC, or Direct Attach Cable, is widely used for short-distance links between servers, switches, and storage equipment in data centers. Compared with optical modules, DAC copper cables offer lower power consumption, lower latency, and a lower overall system cost. For this reason, they remain one of the most important interconnect technologies in modern data centers.
However, the move toward higher transmission speed has also made connector structures smaller and more complex. The conductor, terminal, and shielding components are now packed into a tighter space, while electrical performance requirements continue to increase.
A weld that once met the mechanical requirement may no longer be good enough. The welded joint must now satisfy several conditions at the same time:
- Low and stable contact resistance
- Consistent tensile strength
- Minimal thermal damage to nearby plastic parts
- Stable weld geometry from one part to the next
- No effect on signal transmission quality
These requirements expose the limitations of conventional welding processes.
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Poor Weld Spot Consistency | Incomplete Weld |
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Burn-Through | Plastic Burning |
The Problem with Traditional YAG and QCW Welding
Most DAC cable assemblies have traditionally been welded using YAG lasers or QCW fiber lasers.
These processes rely mainly on infrared energy to melt the copper conductor and terminal together. The problem is that copper reflects most infrared light. As a result, the laser energy is not absorbed efficiently at the beginning of the process.
To achieve a usable weld, manufacturers often increase the laser power or extend the pulse time. This can create a series of familiar problems:
- Unstable weld formation
- Large variation in pull-test results
- Excessive heat entering nearby plastic housings
- Burning or deformation of insulation materials
- Spatter and inconsistent weld appearance
- Poor conductivity caused by incomplete fusion
In high-density connectors, reflected infrared energy can even damage the surrounding plastic and create a risk of short circuit or poor electrical testing results.
The issue becomes even more obvious when welding silver-plated copper conductors to nickel-plated copper terminals, a common material combination in DAC cable production.
How the Red-Blue Composite Process Works
The Han’s Laser solution combines a blue diode laser with a red fiber laser in a single optical path.
Blue Light Absorption Rate on Copper and Gold
Red-Blue Composite Laser Beam Diagram
Comparison of Infrared and Red-Blue Composite Laser Weld Spots on Highly Reflective Pure Copper
Instead of relying on one wavelength alone, the process uses the different characteristics of the two beams to improve the way energy enters the material.
Blue light is absorbed much more effectively by copper than infrared light. At the beginning of the welding process, the blue laser quickly creates a small, stable molten pool on the surface of the conductor and terminal.
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Irregular Part Welding Result
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Pure Copper Wire Welding Result
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Brass Lap Welding Result
Once this molten pool is formed, the material becomes much more receptive to the red laser. The red laser then delivers the deeper penetration and higher power needed to complete the weld.
This two-step interaction changes the entire welding process:
- The blue laser initiates absorption on the highly reflective copper surface.
- The initial molten pool reduces reflectivity and stabilizes the process.
- The red laser enters more efficiently and forms a controlled weld seam.
- Heat is concentrated inside the joint instead of spreading into nearby plastic material.
Because the process starts with better absorption, the total energy requirement is lower and the weld becomes far more stable.
A More Stable Weld on Copper and Copper Alloys
One of the most significant advantages of the red-blue composite process is its ability to weld highly reflective materials consistently.
In DAC cable assemblies, this includes:
- Bare copper
- Silver-plated copper
- Nickel-plated copper
- Copper alloy shielding structures
With traditional infrared welding, these materials often produce inconsistent welds from one part to another. The red-blue process greatly improves repeatability.
The finished weld is more uniform in size and shape, with almost no spatter and very little variation between parts. Because the molten pool is easier to control, the weld can also be placed more precisely in narrow or irregular areas.
This is especially useful when welding:
- Fine-pitch connector terminals
- Shield plates
- Multi-core cable structures
- Irregular conductor layouts
The welding path can be programmed either as a spot weld or as a custom geometric trajectory, allowing the same system to support different connector designs.
Lower Heat Input Means Better Protection for Plastic Components
For high-speed connectors, the metal joint is only part of the challenge. The surrounding plastic housing is often located extremely close to the weld area.
Traditional welding methods can easily overheat this region, causing melted plastic, deformation, or hidden damage that later affects assembly quality or electrical performance.
Because the Han’s Laser red-blue process transfers energy more efficiently into the copper itself, the amount of unnecessary heat is significantly reduced. The heat-affected zone becomes smaller, and nearby insulation materials remain intact.
In actual DAC cable production, this means manufacturers can achieve a full and stable weld without the burned plastic that is commonly seen with conventional QCW or YAG welding.
Dedicated Welding System for High-Speed Connectors and Cables
Han’s Laser integrated this process into a dedicated welding platform designed specifically for high-speed connectors and DAC cable assemblies.
The system combines:
- A blue diode laser and fiber laser in a dual-beam configuration
- QCW and CW operating modes
- Editable waveform control for different material combinations
- Automatic or semi-automatic production options
- Multi-step processing within a single machine
Energy output remains stable within ±1%, which is particularly important for maintaining consistent weld quality during large-volume production.
The laser welder can be configured for conductor welding, shielding component welding, or both within the same process flow. It creates a low-resistance metal connection that improves electrical continuity while reducing signal loss and electromagnetic interference.
Actual Welding Results
A typical DAC cable application involves welding a silver-plated copper conductor to a nickel-plated copper connector terminal.
The process must satisfy three requirements at the same time:
- The weld must appear smooth and fully formed
- The dual-core pull force must exceed 20 N
- The nearby plastic housing must remain undamaged
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| Front-Side Welding Result | Back-Side Welding Result | Side Welding Result |
When conventional QCW fiber lasers or YAG lasers are used, manufacturers often see unstable welding and wide variation in pull-test results. In many cases, the surrounding plastic shows visible signs of burning.
With the Han’s Laser red-blue composite system, the process becomes much more predictable. The weld shape remains consistent, the surrounding plastic stays intact, and pull strength is stable at more than 30 N.
The final joint also shows significantly better tensile and shear strength than joints produced by traditional welding methods.
Built for Modern Connector Manufacturing
Han’s Laser has already delivered this technology for volume production in connector applications across consumer electronics, communication equipment, medical devices, automotive electronics, aerospace, industrial automation, and board-to-board connector manufacturing.
As connector structures continue to become smaller and transmission requirements continue to rise, welding technology must evolve as well.
Red-blue composite laser welding offers a more practical way to join highly reflective copper materials without sacrificing signal quality, process stability, or production efficiency. For manufacturers building the next generation of DAC cable assemblies and high-speed connectors, Han’s Laser provides a new process route that is both technically reliable and ready for mass production.
