224G and 448G Co-Packaged Copper Architecture

With the ongoing explosive growth of the AI and high-performance computing industries, the core bottleneck in data centers has shifted from computing power to ultra-high-speed interconnect transmission, making 224G/448G data rates the central focus of next-generation interconnect technology. Amid industry discussions on the “parallel development of optical and copper technologies,” the Co-Packaged Copper (CPC) architecture remains the mainstream solution for ultra-high-speed short-distance interconnects due to its low loss, high integration density, high reliability, low cost and power consumption advantages in short-distance scenarios. It is expected to coexist with fiber-optic solutions for the foreseeable future. Luxshare-Tech has deep expertise in the high-speed interconnect field. Its 224G/448G CPC technology has achieved key breakthroughs and entered the customer pre-research phase. This article provides a comprehensive analysis of the technology from the perspectives of technical architecture, core components, interconnect characteristics, reliability verification, and testing challenges.

Luxshare-Tech KOOLIO™ CPC

Overview

The 224G/448G CPC interconnect architecture is a key technology supporting high-end computing chips such as 102.4T/204.8T ASICs. Luxshare-Tech’s architecture is based on a 110x110mm substrate co-packaging design:

1.    Shortens signal paths via the OptaFLEX™ interlayer to achieve ultra-low-loss transmission at 224G & 448G

2.    A fully shielded connector structure delivers industry-leading crosstalk suppression

3.    Compatible with Optamax® 31AWG–32AWG cables

4.    3-4 signal layers support 64-pair signal fan-out

5.    Substrate integration eliminates the need for additional sockets or connector reflow processes, meeting the core requirements for high-density, short-distance interconnects in AI data centers

Luxshare-Tech 224G/448G KOOLIO™ CPC Interconnect Architecture

This architecture offers three core advantages: zero-stub design, 360° full shielding, and ultra-high density. Rigid contacts are crimped into an elastic interlayer within the PCB frame, eliminating the risk of bent pins, maximizing layout potential, and reducing PCB trace loss. Luxshare-Tech is simultaneously launching the Luxlink end-to-end interconnect solution, integrating Optamax® 224G & 448G dual-axis cables, Intrepid™ NEXUS 224G & 448G backplane connectors and backplane cables, and KOOLIO™ CPC connectors. With bandwidth exceeding 100GHz, this solution, when paired with OSFP 224G & 448G Airchannel™ pluggable modules, achieves full ecosystem compatibility for pluggable I/O and high-speed backplane architectures, providing end-to-end technical support for 224G & 448G ultra-high-speed transmission.

Dual-axis cables serve as the core medium for signal transmission in CPC architectures, and their design directly determines signal integrity at 224G & 448G speeds. Luxshare-Tech has achieved technical breakthroughs across multiple dimensions. In terms of design types, we have optimized traditional, tightly coupled, and single-extrusion structures to balance low loss, low mode transition, and low skew advantages while precisely controlling manufacturing tolerances. Material selection is tailored to high-frequency transmission characteristics: silver-plated copper is used for conductors, while the dielectric constant and tangent of the loss angle of the insulation layer are strictly controlled. Shielding options include aluminum or copper materials, as well as designs with or without drain wires. The jacket utilizes helical-wrapped tape to ensure consistent performance and reliability.

Driving Signal Transmission in CPC Architectures via Dual-Axis Cables

In terms of bandwidth optimization, by precisely designing the winding pitch and the dielectric constant of the insulation system, the loss resonance point of the 224G CPC coaxial cable is controlled at 80GHz+ (exceeding the target frequency), while that of the 448G cable is controlled at 120GHz, fully meeting transmission requirements. Testing of 32 actual samples shows that key metrics exhibit a tight, normal distribution, demonstrating excellent signal integrity consistency. Regarding mode transition and skew, effective suppression is achieved by enhancing pair-to-pair coupling and controlling common-mode and differential delays, resulting in extremely low skew values at the 53.12 GHz Nyquist frequency. Furthermore, the dual-axis cable has been validated through rigorous testing, demonstrating that bending and twisting have minimal impact on performance. Temperature affects insertion loss only linearly, with no significant changes in mode transition or skew.

The CPC connector is a core component of the architecture. Luxshare-Tech’s KOOLIO™ CPC is specifically optimized for 224G & 448G speeds through three key components: the OptaFLEX™ interface, connector termination, and dual-axis cables. The 224G version demonstrates linear differential insertion loss within 75 GHz and crosstalk isolation of -60 dB at 0–75 GHz, delivering industry-leading suppression performance; The 448G version underwent two-stage optimization: the first stage raised the attenuation cutoff frequency to 80GHz, while the second stage reduced the connector cavity size, pushing the cutoff frequency beyond 100GHz. A 400mm cable assembly was tested to show no significant resonance within 110GHz.

Example of ASIC Cluster

224G/448G KOOLIO™ CPC Design Layering

The CPC and backplane-side interconnects feature a 2.4×2.4mm pin pitch. The independent differential pair design, combined with shielded pins, prevents pin collapse and reduces crosstalk. It supports 224G PAM4 applications and is upgradeable to 100 GHz, with a density of 80 differential pairs per square inch. It is compatible with multiple cable specifications and Luxshare-Tech’s NPC/CPC solutions. The floating guide pin system enables offset compensation of ±3 mm in the XY directions and 4 mm in the Z direction. The new Intrepid™ NEXUS 448G backplane concept design achieves excellent insertion loss and crosstalk suppression within 90 GHz. CPC and OSFP interconnects utilize an OSFP-style plug/cage design, integrating suture-free elastomer technology. Insertion loss is excellently controlled within 90 GHz. When paired with a 16-pair, 31 AWG, groundless, dual-axis cable, insertion loss is only 1.94 dB at 86 GHz, providing a new solution for 448G pluggable interconnects.

Intrepid™ Backplane Connectors

The elastomer interlayer is the core of stable interconnection in CPC connectors. Luxshare-Tech’s OptaFLEX™ elastomer differs from conventional industry products in terms of structure, materials, and manufacturing processes, and has been validated through comprehensive reliability testing. Structurally, it employs a clustered arrangement of gold-plated nickel microspheres, combined with vacuum forming and magnetic aggregation processes, to increase material thickness and enhance available travel, thereby addressing the contact failure issues common in traditional single-pillar metal balls; In terms of materials, the main body is made of silicone rubber with a temperature resistance range of -60°C to 200°C and a permanent compression set of only 13%. The conductive pathways consist of gold-plated nickel balls, offering contact resistance < 100 mΩ, strong corrosion and oxidation resistance, and suitability for high-frequency transmission.

Luxshare-Tech OptaFLEX™ Elastomer Interposer: Advanced Material & Reliability Showcase

The manufacturing process utilizes a stainless steel frame. Through proprietary techniques, conductive materials are blended with silicone rubber and precisely molded using unique IP technology to ensure signal stability. Regarding reliability testing, the product has passed temperature tests ranging from 25°C to 150°C, 100-cycle and 600-cycle insertion/removal endurance tests, 45N four-axis tensile tests, bending and torsion tests, and the full suite of EIA 364 reliability tests, with all test items meeting standards, with no significant signal integrity degradation observed under extreme conditions, verifying that the product meets the long-term operational requirements for 224G & 448G transmission.

 Luxshare-Tech’s OptaFLEX™ Manufacturing Process

At ultra-high speeds of 224G & 448G, testing CPC channels presents multiple challenges, including high bandwidth requirements, complex components, and significant cabling effects.

The core difficulties are concentrated in three areas. First is the definition of test objectives. It is necessary to clearly specify whether the test targets the transmitter/receiver end, the CPC connector, the cable assembly, or the entire channel. Different test objects impose significantly varying requirements on fixture bandwidth and the number of differential pairs to be tested, all of which must meet the 100+ GHz bandwidth standard. Second is test fixture design. All fixtures must provide interconnections from CPC pads to coaxial or backplane sockets while ensuring signal integrity at high frequencies. Fixture precision directly impacts test results, and different interconnection schemes can lead to significant variations in metrics such as impedance and insertion loss. Third, cabling and fixture processes: Substrate signals must be routed to the front and rear ends of the tray, which can easily lead to excessive cable bending and stress. Furthermore, changes in the shape of high-speed cables can affect signal integrity, and testing under actual usage conditions places extremely high demands on the fixture’s ability to accurately simulate these conditions.

Full Channel 224G & 448G Solutions

To address these challenges, Luxshare-Tech has developed a solution based on the coordinated alignment of “test objectives – fixture design – routing processes.” By establishing dedicated assembly process specifications for cable routing and optimizing fixture design to enhance high-frequency interconnection performance, the company ensures accurate and valid test data, providing a reliable basis for product optimization and practical applications.

The iterative upgrades to Luxshare-Tech’s 224G & 448G CPC technology represent the culmination of its technical expertise in the high-speed interconnect field and align with the core requirements of today’s AI data centers for short-range, ultra-high-speed interconnects. As a global innovator and manufacturer of high-performance core component solutions, Luxshare-Tech has always placed technological innovation at the core of its operations. The company has deeply engaged in the R&D of high-speed interconnect technologies, building a comprehensive technical capability system that spans from core component design and end-to-end solution development to reliability verification and test system establishment. Currently, its 224G high-speed cable products have entered mass production, while 448G products are undergoing preliminary research with multiple customers, with mass delivery expected in the near future.

Moving forward, Luxshare-Tech will continue to focus on the interconnect needs of the AI and high-performance computing industries. By driving product innovation through breakthroughs in pre-research, deepening ecosystem partnerships, and continuously pushing the boundaries of high-speed interconnect technology, the company will leverage the cost and power efficiency advantages of CPC technology to complement fiber-optic solutions. This approach will provide core support for the upgrade of next-generation data center architectures and help the global high-end manufacturing industry evolve toward higher data rates, greater integration density, and enhanced reliability.