PCB Manufacturing

12-Layer PCB Stack-up: Maximizing Power Integrity and Signal Performance

12-layer Stack-up PCB

Key contents of this article

  • Getting Started: 12-layer Stack-up of PCB
  • Major Concepts in PCB Stack-up Design
  • Various Configurations of 12-layer PCB Stack-up Design
  • Fabrication In Real-world 
  • Conclusion 

Getting Started: 12-layer Stack-up of PCB

Definition & Application:

A 12-layer stack-up of PCB is a structure just like a sandwich in an electronics circuit system consist three different materials: Copper, Substrate, and Prepreg. It contains conducting layers of printed circuit boards (PCB) that are placed one by one with the separation of prepreg, after this process all layers are pressed at high temperatures for binding together to the firm PCB structure.

For Short Note, a 12-layer stack-up defines the size of the PCB, weight, and thickness.

There are three materials used for the 12-layer PCB stack-up are given below:

  • Copper: The conducting material in a 12-layer stack-up PCB to trace the signal.
  • Prepreg: A material used for isolating the sandwich between the copper layer and core. The fundamental function of prepreg is to bind an ore core or two cores with a conducting copper layer.
  • Base Material/Substrate/Core: A material contains the property of dielectric used for isolation and provides mechanical support. The physical property of the core is laminated pre-coated with copper on both sides.

Applications of 12-layer PCB in different fields of engineering, sciences, and the world are given below:

Autonomous Systems, Advanced Vehicles, Defence Electronics, Telecom Related Infrastructure, Network Switches and Hubs, Complex Digital circuits (CPU, GPU, TPU, FPGA, ASIC, etc), Data Centre Electronics and Advanced Computing Items, etc.

Major Concepts in PCB Stack-up Design

Power Integrity:

When we supply components in PCB, the problem of power transients arises so cater this problem to ensure the quality and stability of power supply in the electronics system. Fundamentally Power Integrity solves the problem and maintains voltage levels within standard acceptable limits, reduces and minimizes noise and power signal interference, and ensures that electronics components and systems become more reliable and maintain system performance.

The significance of Power integrity ensures that the system works under reliable conditions and plays a critical role in the system parameters like the success and failure of electronic products.

Major issues affecting power integrity are given below:

  • Collapse (ripple, transient response) in large power rail and bounce in the ground.
  • Radiated emissions because of weak decoupling and ripples in the electronics system.
  • Noise coupling between different regions of electronics PCB.
  • Product heat-up due to excessive power dissipation.

Signal Integrity:

Signal integrity is measuring the unit of quality of an electrical signal as; it travels from a target source to its intended destination. It also refers to the signal maintaining its intended shape and characteristics like timing, despite various types of electrical disturbances.

 It plays a critical role and crucial importance in ensuring the efficient operation of PCB.

 Factors that cause and solution of signal integrity are given below:

PROBLEM  SOLUTION
CrosstalkTransmission line optimization
EMIStop signal degradation
Interconnects effectsCrosstalk analysis 
AttenuationLink optimization
Propagation delayAnalyze the vector network
Ground BounceGeometrical optimization
ReflectionsImpedance measurement 
Fluctuations in power supplyDe-embedding
Signal characteristics SERDES simulation
ImpedanceImpedance matching

PCB Stack-up Design

Various Configurations of 12-layer PCB Stack-up Design

LAYERSClass:1Class:2Class:3Class:4Class:5
1(Top)SignalSignal SignalSignalSignal
2GroundGroundGroundGroundGround
3SignalSignalSignal SignalSignal
4PowerGroundPowerGroundPower
5SignalPowerGround PowerGround 
6GroundSignalSignalSignalSignal
7GroundSignalSignalSignalPower
8SignalPower GroundPower Ground
9PowerGroundPowerGroundSignal
10SignalSignalSignal SignalPower
11GroundGroundGroundGround Ground
12(Bottom)SignalSignalSignalSignalSignal

Note:  In this Table, I make various classes to define the best configurations of 12-layer PCB stack-ups that are not standardized by any regulatory authority like IPC or any other organization. The only purpose of making this table is to simplify the 12-layer PCB stack-ups so, I choose “class:” as a variable format, and the definition of class is given below:

Class:1Low Power Distortion & High-speed Signal
Class:2EMC Performance & Signal Integrity 
Class:3Mixed Signal & Power Integrity
Class:4Dense Routing & Power Integrity
Class:5High Power & Signal Integrity 

The typical image of a 12-layer PCB design is given below for reference:

12-layer PCB design

Here is another useful table given below:             

Practices to Boost Power IntegrityPractice to Boost Signal Integrity
Power Integration solutionLow-jitter clock sources
Use Fast Transient response voltage regulatorsHigh-Quality connectors
Heat spreaders and sinksEnvironmental shielding
Thermal analysisThermal management
Differential pair routingEMI shielding
Controlled Impedance trace designEMI suppression components
Noise components separationGrounding
Place critical components firstlyClock trace routing
Ground Loops avoidingGrounding
Ground Via stitchingSkew management
Load transient analysisDecoupling capacitor
Solid Ground planesAvoiding 90-degree angles
Impedance controlLayer management
Simulation analysisFerrite beads and filters
Use of low ESR capacitorVia management
Diversification of capacitanceProper Termination
Placement of capacitorPair matching
Thick power and ground planesAc termination
Loop area minimizationUse Differential pairs
Via placement optimizationShort and direct routes
Segment of Power planesControlled impedance trace design
Adequate filtering and DecouplingCrosstalk minimization
Pre- Layout simulationContinuous ground plane design
Post -Layout validationPre-layout simulation
Continuous MonitoringPost-layout Validation
Eye diagram

Pre-layout simulation and Post- layout Validation tools and techniques used for the simulation of power and signal integrity are given below:

ToolsNameDescriptionUsage
IC design toolsVirtuoso, Custom compilerProvide comprehensive IDESimulation of IC behavior
Electromagnetic field solversCST studio suite, Ansys HFSS EMI/EMC simulationHigh-frequency designs 
Power integrity (PI) toolsAnsys Redhawk, cadence VoltusPower Distribution Analysis (PDN) AnalysisDesign robust PDN and analysis
Signal integrity (SI) toolsHyperlynx, SIwaveAnalysis signal integritySolve ringing and timing problems
SPICE SimulationHSPICE, LTspiceSimulate Analog CircuitsSignal propagation 
Post Layout and verificationSPICE, SI/PI co-simulation toolsDesign and layout of extracted parasitics Layout parasitics and components design 
Thermal analysisAnsys icepack, FlothermSimulate the behavior of PCB and components Provide a reliable cooling solution
Design rule check (DRC)Allegro, AltiumLayout of standardized designReduce layout-related errors
Post-layout simulates and verifySPICE, SI/PI co Validate the performances Design and layout of parasitics & component 
Pre-layout simulation and post-layout validation tools:
TechniquesDescriptionUsage
Transmission line modelingAnalysis of signal and transmission and crosstalkBehavior of signal through interconnects
EMI analysisSimulate EM emissions and ensure complianceDesign shielding and filtering
Crosstalk analysisAnalysis and mitigate crosstalkDesign layout strategies and define error coupling
PDN AnalysisDesign power delivery network and noiseAnalysis of power and voltage drops of the circuit
Capacitor optimizationDesign decoupling capacitorImprove power integrity and reduce EMI
Pre-layout simulation and their techniques

Pre-layout simulation and their techniques

Fabrication of 12-Layer PCB In Real-world:

12-Layer PCBs

Fabrication of 12-Layer PCB

12-Layer PCB In Real-world

Stack-up PCB

Conclusion

  • Most useful electronics for future high-performance electronics.
  • Diversified application in different domains but at the same time poses many complexities to fabrication.
  • A huge quantity of certifications (CE, UL, RoHS, ISO, IATF, IEEE, IEC, etc.) required to maintain the quality of PCB. 
  • A critical aspect is to maintain signal and power integrity and make more reliable our electronics products.

    Request for Quote