FAQ
What Causes Insertion Loss in High-Speed PCBA & Cable Assembly?
What Causes Insertion Loss in High-Speed PCBA & Cable Assembly?
Quick Answer
Insertion loss in high-speed PCBA and cable assembly is the reduction of signal power as a signal travels through PCB traces, vias, connectors, solder joints, cable assemblies and other interconnect structures.
In AI server, IPC and industrial high-speed applications, insertion loss may be caused by PCB material loss, copper roughness, long trace or cable length, via stubs, connector transitions, impedance discontinuity, cable construction and assembly workmanship.
The customer’s engineering team usually defines the signal architecture, stack-up, materials and validation requirements. DMAX manufactures according to customer-approved designs and specifications and can support PCB fabrication, PCBA assembly, applicable inspection and cable assembly projects within the agreed project scope.
Key Takeaways
- Insertion loss focuses on signal attenuation, which means how much signal energy is lost as the signal travels forward through the channel.
- Loss can come from the PCB, connector, solder joint or cable assembly, so buyers should review the complete interconnect path, not only one component.
- EMS manufacturing cannot replace signal integrity validation, but it can help preserve the customer-approved design intent through process control, inspection and documentation.
This article focuses specifically on signal attenuation and loss sources. For a broader overview of AI server PCBA and cable assembly risks, refer to: AI Server PCBA & Cable Assembly: High-Speed Manufacturing Challenges.
When This Topic Matters Most
Insertion loss matters most when a high-speed signal path must preserve enough signal strength from transmitter to receiver. It is especially important when the system includes longer routing, multiple interconnect transitions, dense PCB structures or high-speed cable assemblies.
- AI server hardware
- High-speed IPC systems
- Long PCB trace or cable transmission paths
- Board-to-board or cable-to-board connectors
- HDI or multilayer PCB structures
- Controlled impedance requirements
- Low-Dk / low-Df material requirements
- High-speed cable assemblies
- USB, AOC or active extension cable applications
- Products moving from prototype to mass production
Application Note: This topic may be less critical for low-speed, short-distance or non-impedance-sensitive circuits. In those cases, standard PCBA assembly and cable assembly controls may be sufficient, depending on product requirements.
What Is Insertion Loss?
Insertion loss describes how much signal energy is lost as a signal travels through an interconnect path. In a high-speed PCBA or cable assembly, this path may include PCB traces, vias, solder joints, connectors, cables and transitions between them.
Ideally, the signal should reach the receiver with enough strength and clarity. In reality, every material and structure in the path introduces some level of attenuation. As operating frequency increases, conductor loss, dielectric loss and discontinuity effects generally become more significant.
In high-speed systems, even small differences in material, routing or assembly quality can reduce signal margin. Depending on the channel design, connector termination, soldering quality, mechanical assembly variation and cable construction may influence overall channel consistency and contribute to insertion loss.
Key Insertion Loss Drivers and EMS Manufacturing Control Points
The following table summarizes common insertion loss drivers and how manufacturing control can help reduce production-related risk.
| Key Loss Driver | Primary Root Cause | EMS Manufacturing Control Point |
|---|---|---|
| PCB dielectric loss | Signal energy may be absorbed by PCB laminate materials, especially at higher frequencies. | Confirm the customer-specified laminate, stack-up and impedance requirements before production. |
| Copper roughness | At high frequencies, current tends to concentrate near the copper surface, making copper profile more important. | Review stack-up and material notes during DFM. If special copper profile requirements are specified, availability should be confirmed before production. |
| Long trace or cable length | Longer signal paths usually create more conductor and dielectric loss. | Review routing length, cable length and interconnect requirements when provided by the customer. |
| Via stub effects | Unused via stubs may create resonance, reflection or additional attenuation in high-speed channels. | Confirm back-drilling or via control requirements in production files when specified. |
| Connector transition loss | Connector geometry, seating, soldering, press-fit or mating tolerance may affect signal transition quality. | Control connector handling, alignment, soldering and seating consistency according to approved component and assembly specifications. |
| Cable assembly variation | Cable construction, length, shielding, bend radius or termination consistency may affect signal loss. | Maintain cable assembly workmanship, length control, shield termination and inspection records. |
| Assembly process variation | Rework, connector damage, solder variation or uncontrolled handling may change the physical signal path. | Use controlled work instructions, inspection criteria, process quality management and traceability records. |
Important note: This table does not replace signal integrity simulation or validation. It helps buyers understand how EMS manufacturing execution can support the customer’s high-speed design intent.
PCB Material, Copper Roughness and Stack-Up Factors
PCB material is one of the main factors affecting insertion loss. In high-speed applications, the dielectric properties of the PCB material influence how much signal energy is lost as the signal travels through the board.
Two common material-related considerations are Dk and Df. Dk, or dielectric constant, affects signal propagation speed and impedance behavior. Df, or dissipation factor, is related to dielectric loss. For high-speed designs, low-Dk and low-Df materials may be considered to reduce loss and improve signal transmission.
Copper roughness is another important factor. At higher frequencies, current tends to flow closer to the conductor surface, often described as skin effect. If the copper surface is rougher, the signal path may experience more loss. For this reason, some high-speed PCB designs may specify low-profile copper options depending on the application and design requirements.
DMAX PCB Manufacturing Capability Notes
DMAX may support multilayer PCB production, blind and buried microvias, controlled impedance requirements and selected PCB material options according to customer-approved specifications.
Available material options may include FR-4, high-Tg FR-4 and other project-specific PCB materials, subject to approved project requirements, material availability and customer specifications. Specific capabilities such as maximum layer count, minimum drill size, impedance tolerance and material availability should be confirmed during quotation and NPI.
From an EMS perspective, the key responsibility is not to redesign the customer’s stack-up. Instead, the EMS partner should review whether material requirements, impedance notes, copper requirements, stack-up documents and assembly requirements are clearly documented before production.
For dense routing, compact component placement or controlled high-speed breakout areas, HDI (High Density Interconnect) PCBs and Multilayer Rigid PCBs may be relevant product categories to review depending on the customer’s design requirements.
Trace Length, Routing and Via Effects
Longer signal paths usually create more loss. As a high-speed signal travels through a longer trace or cable, more energy is absorbed by conductor and dielectric materials.
Routing geometry also matters. Sharp transitions, discontinuities, poor reference plane control or inconsistent trace geometry may contribute to signal degradation. In some high-speed PCB designs, via stubs can also become a concern because they may create unwanted resonance, reflection or additional attenuation.
Back-drilling may be used in certain high-speed PCB designs to reduce via stub effects. However, this is normally defined by the customer’s design and PCB fabrication requirements. The EMS partner can support the project by checking whether back-drilling, impedance control, stack-up notes and assembly requirements are properly documented in the production files.
Insertion loss focuses on forward signal attenuation. If the same channel also has impedance discontinuities that cause reflected energy, buyers should also review: Why Return Loss Matters in AI Server PCBA & Cable Assembly.
Connector and Cable Assembly Factors
Insertion loss is not limited to the PCB. In AI server, high-speed IPC and industrial computing applications, connectors and cable assemblies may also form part of the complete signal channel.
Connector-related factors may include contact geometry, mating stability, alignment, seating, soldering quality and mechanical tolerance. Connector design is normally defined by the customer or component supplier, while assembly should follow the approved component and workmanship requirements.
Connector and Cable Manufacturing Risks
- Connector misalignment or damaged contacts
- Inconsistent soldering, crimping or cable preparation
- Poor shield termination
- Uncontrolled cable bending
- Inadequate strain relief
- Rework or handling that changes the signal path
Cable-related factors may include cable length, construction, shielding, bend radius, termination quality and strain relief. Depending on the interface design, variation in these areas may contribute to insertion loss, impedance discontinuity, skew, return loss or EMI-related issues.
DMAX’s current cable product references include a 15-meter USB 3.2 Active Extension Cable with active signal boosting and USB Active Optical Cable solutions supporting transmission distances of up to 30 meters. The applicable USB generation, data rate, connector configuration and validation requirements should be confirmed for each project.
For cable pair timing-related risks, refer to: What Is Signal Skew in High-Speed PCBA & Cable Assembly?
DMAX Manufacturing and Quality Support
DMAX supports EMS manufacturing, PCBA assembly, cable assembly, process control and quality management based on customer-approved specifications. Depending on project requirements, DMAX may assist with NPI documentation review, manufacturing feasibility review, inspection planning and production traceability.
For high-speed or reliability-sensitive projects, DMAX can coordinate with customer engineering teams to support sample build, production planning, inspection records and manufacturing consistency. Advanced signal integrity validation, EMI certification, VNA testing or TDR validation should be confirmed by project scope and is typically performed by the customer engineering team or qualified third-party laboratories unless otherwise agreed.
Manufacturing Information DMAX May Confirm During NPI
Depending on the project scope and customer-provided documentation, DMAX may confirm whether the information required for quotation, PCB fabrication, assembly planning and applicable inspection is clearly specified. This review does not replace customer design verification or signal integrity validation.
NPI Review Items for Insertion-Loss-Sensitive Projects
- PCB material requirements
- Stack-up documents
- Controlled impedance notes
- Low-Dk / low-Df material requirements
- Low-profile copper requirements when specified
- Back-drilling or via control notes when specified
- Connector specifications
- Cable assembly drawings
- Cable length and bend radius requirements
- Shielding and termination requirements
- SMT, press-fit or cable assembly process requirements
- Inspection and testing criteria
- Customer-defined validation responsibilities
Depending on the project scope, DMAX may support inline SPI, inline AOI and X-ray inspection for PCBA manufacturing quality control. These methods help identify solder paste, placement, soldering and hidden-joint defects, but they do not directly measure insertion loss or complete high-speed channel performance.
Testing and Validation Considerations
Insertion loss is usually evaluated during design validation or high-speed channel validation, often by the customer’s engineering team, design partner or qualified laboratory. Advanced methods such as TDR, VNA or S-parameter analysis may be used depending on the application and project requirements.
Manufacturing Inspection and Test Planning
- SPI for solder paste inspection
- AOI for SMT inspection
- X-ray or AXI for BGA, QFN or hidden solder joints
- ICT for electrical connectivity
- FCT for product-level functional testing
- Cable continuity testing
- Hi-pot or insulation testing when required
- Press-fit insertion force or force-displacement monitoring when applicable
- Traceability records for critical lots or materials
Important note: Manufacturing inspections help maintain production consistency, but they do not directly validate insertion loss. The validation method, acceptance criteria, sample requirements and responsible party should be agreed before production.
Buyer Checklist for Insertion Loss Risk
Before starting a high-speed PCBA or cable assembly project, buyers should confirm whether the project files, material requirements, connector specifications and validation responsibilities are clear.
- Are the PCB material, stack-up and impedance requirements clearly defined?
- Are low-Dk / low-Df material requirements specified if needed?
- Are high-speed connectors and cable assemblies correctly documented?
- Are cable length, bend radius, pair control and shielding requirements clear?
- Are back-drilling or via stub requirements defined by the design team?
- Are DFM and DFA reviews completed before production?
- Are AOI, X-ray, ICT or FCT requirements defined?
- Are IPC-A-610 or IPC/WHMA-A-620 requirements specified?
- Are critical components, connectors and cable assemblies traceable?
- Is there a clear process for customer validation and engineering feedback?
Recommended DMAX Product / Service Pages
For readers evaluating insertion-loss-sensitive PCBA, high-speed interconnects or cable assembly requirements, the following DMAX product categories may be relevant depending on the project scope.
High-Density PCBA Solutions
High-Speed Cable Assembly Solutions
Conclusion
Insertion loss is a key concern in high-speed PCBA and cable assembly because it affects how much signal energy remains after the signal travels through PCB traces, connectors, cables and other interconnect structures.
In AI server, IPC and industrial high-speed applications, insertion loss may be influenced by materials, trace length, copper roughness, impedance control, via stubs, connector transitions, cable construction and assembly workmanship.
DMAX supports customers with EMS manufacturing, PCBA assembly, cable assembly, process control and quality management for industrial, IPC, AI server and high-speed computing applications. If your project involves insertion-loss-sensitive PCBA, AI server hardware, high-speed interconnects or complex cable assembly requirements, contact DMAX to discuss your production needs, BOM status and manufacturing challenges.
Related High-Speed PCBA & Cable Assembly Topics
After reading this article, you may also be interested in the following related topics:
Frequently Asked Questions
What is insertion loss in high-speed PCBA?
Insertion loss is the amount of signal energy lost as a signal travels through PCB traces, vias, connectors, cable assemblies and other interconnect structures. In high-speed applications, excessive insertion loss may reduce signal quality and system stability.
What causes insertion loss in cable assembly?
Cable assembly insertion loss may be caused by cable length, cable construction, shielding, connector termination, crimping quality, soldering precision, bend radius and impedance discontinuity.
How does PCB material affect insertion loss?
PCB material affects insertion loss through its dielectric properties. Low-Dk and low-Df materials are often considered for high-speed applications because they can help reduce signal loss when used with proper stack-up and impedance control.
Can EMS manufacturing affect insertion loss?
Yes. While insertion loss is strongly influenced by design and material choices, EMS manufacturing can affect the final signal path through soldering quality, connector placement, press-fit control, cable termination, process consistency, inspection standards and handling control.
What should DMAX review during NPI for insertion-loss-sensitive projects?
Depending on project requirements, DMAX can review PCB material notes, stack-up documents, impedance requirements, connector specifications, cable assembly drawings, cable length requirements, shielding requirements, inspection criteria and traceability needs before production.
Does DMAX provide signal integrity simulation or VNA testing?
DMAX focuses on EMS manufacturing, PCBA assembly, cable assembly and process quality control. Signal integrity simulation, VNA testing and TDR validation are typically conducted by the customer’s engineering team or qualified third-party laboratories unless otherwise agreed.
Discuss Your Insertion-Loss-Sensitive PCBA or Cable Assembly Project
If your project involves AI server hardware, high-speed IPC systems, controlled-impedance PCBs, USB AOC, active extension cables or complex cable assembly requirements, contact DMAX to discuss your BOM status, manufacturing documentation, NPI requirements and production challenges.
