Packaging, Chiplets, SI/PI and Board Integration
Co-design die, package and board connectivity for power delivery, signal integrity, thermal performance, test and manufacturability.
Overview
The package is an electrical, mechanical and thermal system. Bumps, RDL, substrates, interposers, traces, vias, decoupling and connectors affect timing, noise, current delivery and temperature.
Chiplet systems add die-to-die interfaces, known-good-die strategy, assembly yield, clocking, coherency, security and cross-die test. Co-design is required because late package constraints can invalidate die IO and power plans.
Learning objectives
Choose package and bump strategy
Model transmission lines and return paths
Plan die-to-die interfaces and chiplet test
Coordinate thermal and power-delivery constraints
Core concepts
RDL
Redistribution layer connecting fine-pitch die pads or bumps to package geometry.
S-parameter
Frequency-domain network representation of reflection and transmission.
Return path
Current path completing a signal loop; discontinuities create noise and radiation.
Impedance
Frequency-dependent voltage/current relationship controlled by geometry and materials.
Known good die
Die screened before multi-die assembly to protect package yield and cost.
Chiplet
Die designed to operate as a component in a multi-die package.
Engineering workflow
Select integration technology
Compare wirebond, flip-chip, fan-out, interposer and 3D options.
• IO count
• Power
• Cost
• Package architecture
Co-design connectivity
Assign bumps, RDL, escape routing and board interfaces.
• Die IO
• Package stack
• Bump map
• Net topology
Analyze SI/PI/thermal
Simulate channels, PDN impedance and heat flow.
• Models
• Workloads
• Margins
• Design fixes
Plan assembly and test
Define known-good-die, boundary test and failure isolation.
• Supply chain
• DFT
• Test flow
• Yield model
Metrics and interpretation
Insertion loss
Signal attenuation through a channel versus frequency.
Return loss
Reflected energy caused by impedance mismatch.
PDN impedance
Frequency-dependent supply response compared with target impedance.
Assembly yield
Probability that all dies, interconnects and package operations produce a good unit.
Signoff checklist and pitfalls
Evidence checklist
- Die/package/board netlists agree
- Bump current and escape routing are feasible
- Channel eye and jitter budgets close
- PDN impedance and decoupling meet targets
- Thermal and mechanical limits pass
- Test covers die-to-die links and assembly faults
Common pitfalls
•
Assigning bumps after floorplan freeze•
Simulating signals without return-path discontinuities•
Ignoring simultaneous-switching noise•
Multiplying die yields without assembly/test economics