Power Integrity Analysis and Optimization in the Substrate Design

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Power Integrity Analysis and
Optimization in the Substrate Design
Harini M, Zakir H, Sukumar M
ABOUT CALIBER
Caliber is a fast growing technology services
company.
 Expertise is High speed PCB, IC package design.
 Highly proficient in Signal Integrity, Power
Integrity, EMI/EMC analysis.
 Specializes in Embedded design services, ATE
hardware & Thermal analysis.
 120+ highly skilled design engineers.
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cost.
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
SERVICES
Signal
Integrity
•Pre layout & Post layout
•Serial & parallel interface (DDR 2/3/4, gigabit-SERDES)
•Co-design (IC/package/board)
•IBIS/IBIS-AMI based system SI
•Crosstalk, channel loss, s-parameter, eye-diagram, timing analysis
Power
Integrity
•DC Analysis (IR drop, voltage/current distribution, density plots)
• AC Analysis ( PDN impedance analysis, target impedance optimization,
Transient noise estimation)
• Decoupling cap analysis & optimization
EMI/EMC
Simulation
Tools
•EMI Radiation
•EMI Susceptibility
•Compliances to various EMI standards during design phase
• Cadence Sigrity PowerDC, PowerSI, optimize PI
• Other EDA tools
NEED FOR
POWER INTEGRITY ANALYSIS?
Modern devices needs higher functionality at
lowers possible power => Lower supply voltage
 Silicon density doubles every year => increase in
core frequency => transient current requirement
is getting higher at lower power supply voltages
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DC analysis (Cadence Sigrity PowerDC)
AC analysis (Cadence Sigrity PowerSI)
Decoupling cap optimization (Optimize PI)
SUBSTRATE DESIGN

ATE TEST BOARD (silicon wafer testing)
It is a multi layer PCB mounted to the ATE (Automatic
Test Equipment) on which the device to be tested is placed.
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Probe Card
Probe cards are test boards used to test and measure
the IC before packing. It is a testing tool that delivers
electrical signals to chips on a wafer by contacting the
probes which is fixed on PCB with epoxy. It is an essential
inspection device that enables a wafer to be tested by
contacting each signal of the tester and pad on wafer with
chip unit at the same time.
Probe card types :
1. Epoxy Cantilever Probe Card
2. Cobra Vertical Probe Card
SUBSTRATE DESIGN

Substrate
A substrate is a base material that supports a
microelectronic device. It is used in Vertical probe cards as
interface between probe card and the wafer. Substrates are
called as Vertical space transformers.
A space transformer is a major component of a probe
card. It provides pitch reduction, high routing density and
localized mid-frequency decoupling.
Types of Substrate :
Depending on the type of material used, Design and
Manufacturing process, the substrates are differentiated as
1. MLO (Multi Layer Organic)
2. MLC (Multi Layer Ceramic)
MLC uses ceramic layers that exceed more than 20 layers
whereas MLO has organic buildup on both sides of a core.
DC ANALYSIS OPTIMIZATION
Systematic variation of various parameters and
show impact of each of them.
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Changing the plane layer material (copper -> silver)
Increasing trace width in the fanout layer to reduce DC
drop.
Increasing plane area (adding 1 or 2 extra power plane in
ceramic layer)
Increase via connectivity
Increasing the plane thickness
DESIGN#1
24 layer stackup 1-DUT
MLC substrate
Total die pin count 936 pin
Total thickness 2.8mm +/- 0.05mm
POWER DOMAINS
IR Drop target for S0_VDD < +/- 1%
IR DROP ANALYSIS
ORIGINAL CASE : with 1 power plane in ceramic layer, copper
conductor of 10 um thickness for power planes
CASE1 : ORIGINAL CASE + conductor material changed to silver
=> Change of material makes only 0.1% difference
CASE2 – CASE 1 + thin film layer fanout trace width is increased
from 30 um to 90/100 um
=> Fanout trace width increase made significant difference
Hotspot region shown in the thin film layer
CASE3 - CASE 2 + 2 power plane in ceramic layer of 10 um thickness
=> Adding additional plane didn’t help much
CASE3.1 - CASE 3 + improved via connectivity
=> Improving via connectivity made little difference
Improved via connectivity
=> Improving via connectivity make some difference
CASE4 – CASE3 + power plane in ceramic layer of 18 um thickness
=> Now we achieved the target
DESIGN#2
33 layer 3-DUT
1623 pins/site
Thickness 3.8mm +/- 0.05mm
Similar trends were observed during IR drop optimization process
RESULTS
Similar trends were observed during IR drop optimization process
Z11 ANALYSIS
Case#1: Original layout
Case#2: Adding 1 power plane
Case#3: Adding 2 power plane
Case#4: Adding extra decoupling capacitors
Original
Case#1
Case#2
Case#3
Case#4
Decap report for the best scheme
CONCLUSIONS
Each layout should be seen on case by case basis
for AC and DC analysis. Effectiveness of
universal rule does not apply.
 Systematic analysis was done for DC analysis
and AC analysis using Cadence Sigrity tool
 Bottleneck is to be found for each new layout for
improving IR drop and meeting the target Z.
 Increasing fanout trace width and plane layer
thickness was found to be most effective in these
cases for improving IR drop
 Cadence Sigrity tools are very significant tools
for doing such kind of analysis quick and
efficient.

THANK YOU
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Karnataka, India
Direct line: +91 82200 45099
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