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Power
Gold
On-chip Inductors and Transformer
Applied Power Electronics Conference
SP1.4 Power Supply on a Chip - PwrSoC
Palm Springs, California
25 Feb 2010
James J. Wang
Founder
Power Gold LLC
3131 E. Muirwood Drive
Phoenix, Arizona 85048
[email protected]
APEC 2010
www.PowerGoldConsultant.com
1
RFIC’s Planar Spirals
Power
Gold
< 10 nH
Eddy currents
Not over actives
EMI
NEC Electronics
APEC 2010
www.PowerGoldConsultant.com
2
On-chip Inductors
Power
Gold
• 5nH to 2700nH
• Low Rdc, 9 µm thick gold
RF skin effect
• Magnetic cores >100 µm thick
Optimize to frequencies
• Low cost production processes
• Flexible design, trim-able
• Minimize EMI directly over active IC circuits
• Small; multiple inductors onto existing chips
APEC 2010
www.PowerGoldConsultant.com
3
Linear Gold Inductor
Power
Gold
Gold wires
< 250 µm
loop height
54 µm
wire pitch
Electroplated gold line
Form tiny gold coils
APEC 2010
www.PowerGoldConsultant.com
4
Gold Over Passivation Metals
Power
Gold
9 µm thick Power Gold
18 µm thick gold bumps
TAB for LCD Driver ICs
Wire bond pad & interconnect line
for microcontrollers
Publication:
“Power Gold for 175C Tj-max”, J. Wang and B. Baird at Pan Pacific Microelectronics Symposium, Feb. 2003, pp241
APEC 2010
www.PowerGoldConsultant.com
5
Gold on IC
Power
Gold
Aluminum or
copper layers
underneath gold
OPM
Gold
Gold
Power Gold
interconnects
APEC 2010
www.PowerGoldConsultant.com
6
Wire Bonds onto Gold Pads
Gold pads
Power
Gold
Wire bonds
over actives
Stronger
gold-bold
bonds
3x more gold
in 2 mils
wires than
electroplated
gold on-chip
APEC 2010
www.PowerGoldConsultant.com
7
Toroidal Gold Inductor
Power
Gold
700 µm diameter;
measures 8 nH
from 1-300 MHz
Q=7
APEC 2010
www.PowerGoldConsultant.com
8
Advantages of Gold Inductors
TM
Power
Gold
• Tiny: < 1 mm diameter x 0.25 mm height
Fits 1 mm thin QFN packages
• Integrate 2, 4, 16 or more on-chip inductors
Add onto existing ICs
• Gold ball bonds + electroplated thick gold
Production ready, low cost
Volume processes & tools
• Lower cost than discretes (0402 chip-inductors)
• Alter inductance by adjusting wire loop height
• Gold is ideal > GHz, RF frequencies
APEC 2010
www.PowerGoldConsultant.com
9
Inductor Physics
L = µ0
2
n l
Power
Gold
A
Area
L = inductance value
l
10-10
µ0 – 4π x
Henry/mm
n – number of turns/unit length
l – length of inductor coils
A – cross-sectional area of linear inductor
APEC 2010
www.PowerGoldConsultant.com
10
Larger Air Core Toroids
Power
Gold
Toroidal inductors; 1.0 mil Au wires; 10 mil loop
height
2.5E-07
Inductance (Henry)
2.0E-07
Practical
limit
Too large
1.5E-07
128 turns_1.0 mil
64 turns_1.0 mil
32 turns_1.0 mil
1.0E-07
16 turns_1.0 mil
5.0E-08
0.0E+00
0.00
10.00
20.00
30.00
40.00
50.00
Circular Area (mm2)
APEC 2010
www.PowerGoldConsultant.com
11
Ferrite Core Gold Inductor
Power
Gold
1 mm
9 Turns
1x2x0.2
mm
150 nH
Q=6
@ 2.4 MHz
APEC 2010
www.PowerGoldConsultant.com
12
11 Turns Gold Inductor
Power
Gold
2 mm
Ring oscillator,
transistors
test structures
underneath
inductor to
evaluate
interference.
APEC 2010
www.PowerGoldConsultant.com
13
Rdc & Inductances
Power
Gold
Ferrite Cores measured @ 5 MHz
2 ferrite materials
Parallel wires
500
800
450
700
400
350
500
L or Rdc
L (n H )
600
400
300
R (mOhm; 2 wires)
300
R (mOhm; 3 wires)
250
L (nH; 3 wires)
200
200
150
100
100
L (nH; 2 wires)
50
0
0
2
4
6
8
10
12
14
0
0
Number of Turns
5
10
15
Number of turns
Measurements: Marilyn Stuckey & Hanyu Sheng
APEC 2010
www.PowerGoldConsultant.com
14
Magnetic Field Lines
Power
Gold
Ferrite core
35 turns
coil
designed to
keep the
EM field
lines within
the core,
parallel to
IC surface
2 mm
APEC 2010
www.PowerGoldConsultant.com
>1500 nH
15
Isat > 1A
Power
Gold
Measured L @
5MHz decreased
less than 1%;
tested to 1 A
Ferrite core
APEC 2010
www.PowerGoldConsultant.com
16
Designing Transformer
primary/secondary coils
Power
Gold
Insulator between
two layers
minimizes eddies
1 mm
35 turns;
permalloy core
2.7 µH
APEC 2010
www.PowerGoldConsultant.com
17
Material Possibilities
Power
Gold
Inductor cores:
• Air (lowest cost)
• Ferrites (130 µm thick)
• High permeability permalloy (105 µm thick)
• Glob-top with magnetic filler particles
• Other materials not yet tried
• Round, rectangular, octagonal, etc.
Custom for frequency, L, Q
APEC 2010
www.PowerGoldConsultant.com
18
Ready for IC Evaluations
Power
Gold
• Layout inductors over existing ICs
Design & processes available
Prototype then evaluate
Characterize & optimize
• ESD, spike current protection
• Shrink hand-held devices
• Lowers cost
Publication:
“Flexible On-chip Inductors and Transformer”, J. Wang, IMAPS
Device Packaging Conf, Ft. McDowell, Arizona 10Mar10
APEC 2010
www.PowerGoldConsultant.com
19
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