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Advanced Bode Plot Techniques for Ultrasonic Transducers
Available online at www.sciencedirect.com
ScienceDirect Physics Procedia 63 (2015) 2 – 10
43rd Annual Symposium of the Ultrasonic Industry Association, UIA Symposium 2014
Advanced bode plot techniques for ultrasonic transducers D. A. DeAngelis and G. W. Schulze Mechanical Engineering, Ultrasonics Group, Kulicke & Soffa Industries, 1005 Virginia Drive, Fort Washington, PA 19034, USA
Abstract The Bode plot, displayed as either impedance or admittance versus frequency, is the most basic test used by ultrasonic transducer designers. With simplicity and ease-of-use, Bode plots are ideal for baseline comparisons such as spacing of parasitic modes or impedance, but quite often the subtleties that manifest as poor process control are hard to interpret or are nonexistence. Inprocess testing of transducers is time consuming for quantifying statistical aberrations, and assessments made indirectly via the workpiece are difficult. This research investigates the use of advanced Bode plot techniques to compare ultrasonic transducers with known “good” and known “bad” process performance, with the goal of a-priori process assessment. These advanced techniques expand from the basic constant voltage versus frequency sweep to include constant current and constant velocity interrogated locally on transducer or tool; they also include up and down directional frequency sweeps to quantify hysteresis effects like jumping and dropping phenomena. The investigation focuses solely on the common PZT8 piezoelectric material used with welding transducers for semiconductor wire bonding. Several metrics are investigated such as impedance, displacement/current gain, velocity/current gain, displacement/voltage gain and velocity/voltage gain. The experimental and theoretical research methods include Bode plots, admittance loops, laser vibrometry and coupled-field finite element analysis. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-reviewunder under responsibility of Ultrasonic the Ultrasonic Industry Association. Peer-review responsibility of the Industry Association
Keywords: Ultrasonic transducer; Wire bonding; Bode plots; Piezoelectric; PZT8; Vibrometer; Coupled-field FEA; ANSYS 1. Introduction The Bode plot, displayed as impedance or admittance versus frequency, is the most basic test used by ultrasonic transducer designers. With simplicity and ease-of-use, Bode plots are ideal for baseline comparisons such as spacing of parasitic modes and impedance. But, quite often the subtleties that manifest as poor process control are hard to interpret or are nonexistent from standard Bode plots. In-process testing of transducers is time consuming for quantifying statistical aberrations, and assessments made indirectly via the workpiece are difficult for identifying
1875-3892 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Ultrasonic Industry Association doi:10.1016/j.phpro.2015.03.002
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cause and effect relationships. Transducer modal surveys require an expensive scanning laser vibrometer and interpretation is esoteric. Advanced bode plot techniques are needed for a-priori process assessment of ultrasonic transducers. 2. Specific transducer application Kulicke & Soffa Industries is the leading manufacturer of semiconductor wire bonding equipment. This “backend” type of equipment provides ultrasonically welded interconnect wires between the wafer level semiconductor circuitry (die) and the mounting package (frame) as shown in Fig. 1. The ultrasonic transducer delivers energy to a capillary tool for welding tiny gold or copper wires, typically on the order of .001 inches in diameter. Fig. 2 shows the primary steps of the wire bond cycle used to produce the interconnect wires, and how the ultrasonic energy from the transducer is delivered in a “scrubbing motion” to make the welded bonds. Fig. 1(d) shows the on-machine configuration. The single-piece construction “Unibody” transducer uses four diced, rectangular PZT8 piezoceramics, and is ideal for research studies (DeAngelis et al., 2006, 2009, 2010). Portability across 100’s of machines is required for the same customer device in production operations. (a)
Piezo Stack
(b)
Transducer Body
(c)
(d)
On IConn Machine Transducer
1¢ US
New IConn Transducer
Device Die
Capillary Tool
Capillary EFO (Spark)
Fig. 1. (a) K&S “Unibody” ultrasonic transducer, (b) Ceramic capillary tool tip with fine gold wire compared to sewing needle, (c) Actual wire bonds from multi-tier package, (d) On-machine configuration of “Unibody” transducer during device wire bonding.
c
e
d Fig 2. Primary steps 1, 2 and 3 of the wire bond cycle
3. Assessment methodology What aspects of transducer performance are important for ideal process control (Stansfield, 1991, Wilson, 1991, Sherman et al., 2007, Uchino et al., 2003)? The mechanical interfaces must behave linearly in vicinity of the operating mode, such that there is no separation or “gapping” with drive level or frequency change (DeAngelis et al., 2009, 2010); the critical interfaces are tool-to-clamp and the piezoceramic stack. The displacement gain of all surfaces must behave linearly in vicinity of the operating mode and proportional to drive level: the displacement/current gain should be linear in vicinity of resonance, and the displacement/voltage gain should be linear in vicinity of antiresonance (DeAngelis et al., 2006). The tool motions must be consistent in all directions above and below the operating mode: in-plane motions remain in-plane, and linear motions remain linear and in same direction. No local parasitic resonances should be competing with the operating mode; parasitic coupling has a 180° phase change when driven through the operating mode. The usual suspects are shim electrodes, tool clamps, screws and tools. Shim electrode resonances are hard to detect since their manifestation can vary wildly with slight
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change of operating frequency. There should be no hysteresis in frequency or displacement gain with sweep direction; the phase lock loop (PLL) can approach arbitrarily from either side, and thus hysteresis can cause phase/amplitude oscillation or failure of PLL to lock at resonance. Interface gapping can change with phase of parasitic coupling above and below operating mode, causing hysteresis in gain and frequency. Internal self-heating effects from impedance are different above and below operating mode due to antiresonance and sweep start direction. 4. Research summary Advanced Bode plot techniques were developed from the basic constant voltage versus frequency sweep; this included constant current and constant velocity interrogated locally on transducer (Uchino et al., 2003, Ural et al., 2009), with added up and down directional frequency sweeps to quantify hysteresis effects (Umeda et al., 2000). Selected transducers with known “good” and known “bad” process control were studied, and a linear coupled-field FEA model was correlated to the “good” transducer. The advanced Bode plot methodology for a-priori process assessment was established based on these comparisons. 5. Experimental methods and metrics Fig. 3 shows the hardware setup for the advanced Bode plot technique. Fig. 4 shows the methodology for velocity interrogation. The tool is the “business end” of the transducer and should be a starting point. The tool clamp is a close second for interrogation, since it may exhibit more non-linearities than tool with free-air assessment (i.e., off work). As shown in Fig. 5, the piezoceramic stack should also be another target area, and especially for Langevin or sandwich transducers which are prone to uneven preload stress. High power piezo stacks can rely on adhesives in tension which can fail, and shims and preload bolts are dynamic components that are prone to resonate. Amp 10:1
Transducer
Laser Vibrometer Polytec OFV 056
Laser Beam V-ref
LV
Laser Dot
100Ω Resistor
V-out
I-in
V-Probe
Network Analyzer HP E5100A
Oscilloscope Tektronics DPO7054
Ultrasonics Power Amp 4:1
Attenuator
Vel-in
Vel
NA
I-Probe OS GPIB I/O
VB OS
GPIB I/O Function Generator HP 33120A NA
LV GPIB I/O
USB I/O
USB/GPIB Interface Agilent 82357B
PC Command Center (Visual Basic Program)
Four LCD Monitors
Fig. 3. Advanced Bode plot technique hardware setup. Top or Tip of Tool in -Y Direction (Operating Mode Direction)
Top or Tip of Tool in X Direction
Tip of Tool in Z Direction Laser Dot (Z-Tip)
Laser Dot (X-Top)
Laser Dot (Y-Top)
Y
Z
Z Laser Dot (X-Tip) Y
Laser Dot (Y-Tip)
X
X Shim Electrode in -Y Direction
Piezo Stack in Z Direction
Tool Clamp in -X Direction
Laser Dot (Y-Shim)
Z
Y
Laser Dot (X-Clamp)
Y X
Z Laser Dot (Z-Stack)
X
Fig. 4. Methodology for velocity interrogation.
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
K&S Orthodyne Large Wire Wedge Bond Transducer (Langevin Style with Bolted Piezo Stack Driver) K&S Maxum Ultra Transducer (Previous Model Transducer for Ball Bonding) Preload Bolt
Shim Electrodes
Tool Clamp (Set Screw)
Piezo Stack Tool Clamp (Split)
Piezo Stack Driver (Thru Bolted) Wedge Tool (Long and Heavy WC)
Screw Preload Wedge (3Pc.)
Ceramic Tool
Fig 5. Velocity interrogation target areas for typical transducers.
6. Finite element modeling Fig. 6 shows the piezoelectric coupled-field finite element model from the ANSYS software with coupling via “stiffness” matrix which includes the piezoelectric properties for PZT8 material. The nodes have structural (X, Y, Z displacements) and electric (volt) degrees of freedom. The linear model was created without interface gapping (i.e., no gap elements) to correlate to the “good” transducer, and a constant damping ratio of 0.2% was used for all materials. The forced response was generated using a sine-sweep voltage input to the piezoceramic stack. Fig. 7 shows the FEA derived Bode results for clamp and top of capillary tool in the X-Clamp, X-Top and Y-Top directions as shown in Fig. 4; there is no hysteresis with the linear model, so results are independent of sweep direction. Fig. 8 shows the FEA derived gain ratio results for these same directions. The current and velocity gains are the same with a FEA linear model.
Orange: Electrode
Piezo Ceramics
Yellow: +Y Poled Green: -Y Poled
Fig. 6. Piezoelectric coupled-field finite element model in ANSYS software.
X-Clamp
X-Top
Y-Top Capillary Tool
Fig. 7. FEA derived Bode results for clamp and top of capillary.
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X-Clamp
Y-Top
X-Top
Capillary Tool
Fig. 8. FEA derived gain ratio results for clamp and top of capillary.
7. Experimental results Figs. 9-12 show the advanced Bode technique results for the “good” transducer with the expected or “good” process response. As shown in Fig. 4, the velocity interrogation locations are X-Clamp, X-Top and Y-Top. The gain ratio results presented in Fig. 12 are for comparison to the linear FEA model, to demonstrate that a “good” process response is inherently a linear response. Figs. 13-17 show the advanced Bode technique results for the “bad” transducer with poor process response (i.e., inconsistent shears). The velocity interrogation locations are the same as the “good” transducer. - Hysteresis Gets Worse for
100
1.65
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Tool Clamp in -X Direction
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Slope Change
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Laser Dot
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0.45 -60
Hysteresis
0.30
Increasing Current (Normal Due to Heating)
- Fairly Constant Current Gain with Sweep Direction and Drive Level - Some Degradation in Tool Clamping for Higher Current (Typical)
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0.15 0.00 121700
Admittance Phase (Deg)
Displacement/Current (um/A)
Constant Current Feedback SF5505-13 IConn 1.80
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Frequency (Hz)
Fig. 9. Constant current Bode for “good” transducer with X-Clamp velocity.
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90
Admittance Mag (S)
Constant Current Feedback SF5505-13 IConn 105
0.065
Admittance Phase (Deg)
Displacement/Voltage (um/V)
Constant Current Feedback SF5505-13 IConn 0.070
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D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
0.050
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~Same Gain as Clamp
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Frequency (Hz)
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Feedback Voltage 7V 5V 8V
Legend Red Green Blue
- Fairly Constant Gain With Current/Velocity - X-Clamp/X-Top Current Gain Nearly 1:1
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
Vibrometer Range 5 mm/s/V 25 mm/s/V 25 mm/s/V
Constant Velocity Feedback SF5505-14 IConn 75
1.0
60
0.9
45
Tool Top in -X Direction
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Laser Dot
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Constant Velocity Feedback SF5505-14 IConn
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0.0 121700
Displacement/Current (um/A)
Admittance Phase (Deg)
Constant Current Feedback SF5505-14 IConn 105
1.2
Displacement/Voltage (um/V)
Displacement/Current (um/A)
Constant Current Feedback SF5505-14 IConn 1.3
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0.005
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Frequency (Hz)
Frequency (Hz)
Fig. 10. Constant current/velocity Bode for “good” transducer with X-Top velocity.
75
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Legend Red Green Blue
Feedback Vibrometer Voltage Range 8V 25 mm/s/V 5V 125 mm/s/V 8V 125 mm/s/V
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
- Very Consistent Gain With Current/Velocity - Overall Great Performance Constant Velocity Feedback SF5505-16 IConn
Constant C t tV Velocity l it F Feedback db k SF5 SF5505-16 IConn 6.50
105
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Tool Top in -Y Direction
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90
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Constant Current Feedback SF5505-16 IConn 105
6.0
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Constant Current Feedback SF5505-16 IConn 6.5
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Frequency (Hz)
Fig. 11. Constant current/velocity Bode for “good” transducer with Y-Top velocity.
60
19%
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18%
30
17%
14% 13% 12% 11%
15
FEA Predicted 20%
X-Top Y-Top Gain Ratio
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28% 27% 26% 25% 24%
50 40 30 20 10
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X-Clamp Y-Top Gain Ratio 121900
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100 90 80 70 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 122700
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36%
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33% 30% 27% 24% 21% 18% 15% 12% 9% 6% 3% 0% 121700
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Constant Current Feedback SF5505-13-14 IConn
122100 122200 122300 Frequency (Hz)
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Constant Current Feedback SF5505-13-14 IConn 90
300%
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155%
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FEA Predicted 130%
X-Clamp X-Top Gain Ratio
100% 121700
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Frequency (Hz)
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Admittance Phase (Deg)
160%
Voltage Gain Ratio X-Clamp/X-Top
Current Gain Ratio X-Clamp/X-Top
122300
39%
Admittance Phase (Deg)
31% 30% 29%
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Constant Current Feedback SF5505-13-16 IConn
Voltage Gain Ratio X-Clamp/Y-Top
Current Gain Ratio X-Clamp/Y-Top
Constant Current Feedback SF5505-13-16 IConn
19% 18% 17% 16% 15% 121700
122100
Frequency (Hz)
Frequency (Hz)
Admittance Phase (Deg)
15%
80 70 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 -80 122700
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Fig. 12. Gain ratios with X and Y velocities for “good” transducer.
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16%
32% 30% 28% 26% 24% 22% 20% 18% 16% 14% 12% 10% 8% 6% 4% 2% 0% 121700
Admittance Phase (Deg)
75
20%
Admittance Phase (Deg)
Constant Current Feedback SF5505-14-16 IConn 90
21%
Voltage Gain Ratio X-Top/Y-Top
Current Gain Ratio X-Top/Y-Top
Constant Current Feedback SF5505-14-16 IConn 22%
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D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
Current/Voltage 083006-1 Maxum
Tool Clamp in -X Direction
120
55
100
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60
Mag
40
40
Normal Bode Response
35 30 25
Mag Down
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Laser Dot
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Admittance Mag (mS)
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Mag Down
Phase
Phase Down
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Unit Velocity/Volts (dB)
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Frequency (kHz)
Fig. 13. Standard Bode for “bad” transducer with X-Clamp velocity. 100
2.00
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1.50
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Tool Clamp in -X Direction Laser Dot
0.75
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123800
- Hysteresis Gets Worse for Increasing Current (Normal Due to Heating)
123900
124000
124100
124200
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124400
124500
- Fairly Constant Current Gain with Sweep
Admittance Phase (Deg)
Displacement/Current (um/A)
Constant Current Feedback 083006-4 Maxum Ultra 2.25
Direction and Drive Level
- Some Degradation in Tool Clamping for Higher Current (Normal)
-80 124600
Frequency (Hz)
90
0.055
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0.060
80 Admittance Phase (Deg)
Displacement/Voltage (um/V)
100
0.09
-80
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0.000 123600
Admittance Phase (Deg)
Constant Current Feedback 083006-4 Maxum Ultra
Constant Current Feedback 083006-4 Maxum Ultra 0.10
-75 123700
123800
123900
Frequency (Hz)
124000
124100
124200
124300
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124500
-90 124600
Frequency (Hz)
Fig. 14. Constant current Bode for “bad” transducer with X-Clamp velocity. 90
2.0
75
1.8
60 45
Tool Clamp in -X Direction
1.4
30
Laser Dot
1.2
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1.0
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- Little Hysteresis with Sweep Direction - No Serious Issues at Interface from Parasitic Modes Legend Red Green Blue
Vibrometer Range 5 mm/s/V 25 mm/s/V 25 mm/s/V
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
Constant Velocity Feedback 083006-4 Maxum Ultra 100
0.060
90
0.09
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0.055
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Admittance Mag (S)
0.10
Admittance Phase (Deg)
Displacement/Voltage (um/V)
Constant Velocity Feedback 083006-4 Maxum Ultra
Feedback Voltage 12V 8V 14V
0.005 0.000 123600
-75 123700
123800
123900
124000
124100
124200
124300
Frequency (Hz)
Fig. 15. Constant velocity Bode for “bad” transducer with X-Clamp velocity.
124400
124500
-90 124600
Admittance Phase (Deg)
1.6
- Fairly Consistent Gain with Sweep Direction and Velocity Level Admittance Phase (Deg)
Displacement/Current (um/A)
Constant Velocity Feedback 083006-4 Maxum Ultra 2.2
9
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
80 60
0.150
40
0.125
20
0.100
0
0.075
-20
0.009
100
0.008
80
0.007
60
0.006
40
0.005
20
0.004
0
0.003
-20
0.002
-40
0.001 0.050
Admittance Phase (Deg)
100
Displacement/Voltage (um/V)
0.175
Displacement/Current (um/A)
Constant Current Feedback 083006-2 Maxum Ultra
Phase Changes Seen
0.200
Admittance Phase (Deg)
Constant Current Feedback 083006-2 Maxum Ultra 0.225
-60
-40
0.025
0.000 123600
-60
123700
123800
123900
124000
124100
124200
124300
124400
124500
-80 124600
Frequency (Hz) 0.000 123600
123700
123800
123900
124000
124100
124200
124300
124400
124500
- Displacement Stability Issues with Current &
-80 124600
Frequency q (Hz)
Legend Red Green Blue
Feedback Voltage .5V 1V 2V
Velocity Feedback - Velocity Feedback Unstable Above 2V Due to Oscillation (Non-Sinusoidal Velocity Waveform) - X-Clamp/X-Top Current Gain >10 (Gapping)
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
Vibrometer Range 5 mm/s/V 5 mm/s/V 5 mm/s/V
Constant Velocity Feedback 083006-5 Maxum Ultra 0.10
100
0.09
80
0.08
60
0.07
40
0.06
20 0
0.04
-20
0.03
-40
0.02
-60
Laser Dot
0.01 0.00 123700
-80
123800
123900
124000
124100
124200
124300
80
0.004
60
0.003
40
0.003
20
0.002
0
0.002
-20
0.001
-40
0.001
-100 124500
124400
100
0.004
0.000 123700
Admittance Phase (Deg)
0.05
Admittance Phase (Deg)
Tool Top in –X Direction
Displacement/Voltage (um/V)
Displacement/Current (um/A)
Constant Velocity Feedback 083006-5 Maxum Ultra 0.005
-60
123800
123900
124000
124100
Frequency (Hz)
124200
124300
124400
-80 124500
Frequency (Hz)
Fig. 16. Constant current/velocity Bode for “bad” transducer with X-Top velocity. 105
0.30
90
0.28
75
0.25
60
0.23
45
4.5 4.0 3.5 3.0
30 15 0 -15
0.20
30
0.18
15
0.15
0
0.13
-15
0.10
-30
0.08
-45
10% Increase
0.5 0.0 123600
123700
123800
-30 -45 -60 -75
123900
124000
124100
124200
124300
124400
124500
0.05
-60
0.03
-90 -105 124600
0.00 123600
-75 123700
123800
123900
124100
124200
124300
124400
124500
-90 124600
Frequency (Hz)
Frequency (Hz) Frequenc
Legend Red Green Blue
Feedback Voltage 8V 5V 8V
Vibrometer Range 25 mm/s/V 125 mm/s/V 125 mm/s/V
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
- Inconsistent Gain With Current/Velocity (∆10%) - Overall Fair Performance - Root Cause: Found MFG Error in Tool Hole - Difficult to Detect with Incoming Inspection
Constant Velocity Feedback 083006-2 Maxum Ultra
Constant Velocity Feedback 083006-2 Maxum Ultra 105
0.325
105
6.5
90
0.300
90
6.0
75
0.275
75
5.5
60
0.250
60
5.0
45
0.225
45
4.5
30
0.200
30
0.175
15
0.150
0
0.125
-15
0.100
-30
0.075
-45
-75
0.050
-60
-90
0.025
4.0
Tool Top -Y Direction
15
3.5
0
3.0
-15
2.5
-30
2.0
-45
1.5
-60
1.0
Laser Dot
0.5 0.0 123600
123700
123800
123900
124000
124100 Frequency (Hz)
124200
124300
124400
124500
-105 124600
Admittance Phase (Deg)
7.0
Displacement/Voltage (um/V)
Displacement/Current (um/A)
124000
0.000 123600
Admittance Phase (Deg)
2.5 2.0 1.5 1.0
Admittance Phase (Deg)
0.33
90 75 60 45
Displacement/Voltage (um/V)
Displacement/Current (um/A)
120 105
6.5 6.0 5.5 5.0
Admittance Phase (Deg)
Constant Current Feedback 083006-2 Maxum Ultra
Constant Current Feedback 083006-2 Maxum Ultra 7.5 7.0
-75 123700
123800
123900
124000
124100
124200
124300
124400
124500
-90 124600
Frequency (Hz)
Fig. 17. Constant current/velocity Bodes for “bad” transducer with Y-Top velocity.
8. Conclusions The transducer with “good” process performance conforms to behavior as predicted by the ideal linear FEA model with glued interfaces (i.e., no gap elements). Non-linear behavior in the tool was shown to be the root cause of poor process (i.e., low shear force): manufacturing error exacerbated inherent design problem in the tool clamp. Phase changes from closely spaced parasitic modes can lead to hysteresis effects due to interface gapping as seen from the non-sinusoidal velocity profile; heating effects can also cause hysteresis. Velocity based Bode plots can pick-up subtleties typically overlooked without a full laser vibrometer modal survey. A unique set of interrogation locations and assessment criteria is required for each specific transducer design and process application; wire bonding is inordinately sensitive to tool motions due to delicate balance of forces exerted on tiny ball and micro bond pad structure; inconsistent energy delivery to the tool is a root cause of poor process.
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D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
References C. H. Sherman and J. L. Butler, Transducers and Arrays for Underwater Sound. New York, NY: Springer Science, 2007. D. A. DeAngelis and D. C. Schalcosky, “The Effect of PZT8 Piezoelectric Crystal Aging on Mechanical and Electrical Resonances in Ultrasonic Transducers,” 2006 IEEE Ultrasonics Symposium, Session P2O-10. D. A. DeAngelis, G. W. Schulze, “Optimizing Piezoelectric Ceramic Thickness in Ultrasonic Transducers,” 2010 UIA Symposium Proceedings, IEEE XPlore. D. A. DeAngelis, G. W. Schulze, “Optimizing Piezoelectric Crystal Preload in Ultrasonic Transducers,” 2009 UIA Symposium Proceedings, IEEE XPlore. D. Stansfield, Underwater Electroacoustic Transducers. Los Altos, CA: Peninsula Publishing, 1991. K. Uchino and J. R. Giniewicz, Micromechatronics. New York, NY: Marcel Dekker, 2003. M. Umeda, K. Nakamura, S. Takahashi, S. Ueha, “An Analysis of Jumping and Dropping Phenomena of Piezoelectric Transducers using the Electrical Equivalent Circuit Constants at High Vibration Amplitude Levels,” Japanese Journal of Applied Physics Vol. 39 (2000) pp. 56235628. O. B. Wilson, Introduction to Theory and Design of Sonar Transducers. Los Altos, CA: Peninsula Publishing, 1991. S. O. Ural, S. Tuncdemir, Y. Zhuang, K. Uchino, “Development of a High Power Piezoelectric Characterization System and Its Application for Resonance/Antiresonance Mode Characterization,” Japanese Journal of Applied Physics 48 (2009) 056509.
ScienceDirect Physics Procedia 63 (2015) 2 – 10
43rd Annual Symposium of the Ultrasonic Industry Association, UIA Symposium 2014
Advanced bode plot techniques for ultrasonic transducers D. A. DeAngelis and G. W. Schulze Mechanical Engineering, Ultrasonics Group, Kulicke & Soffa Industries, 1005 Virginia Drive, Fort Washington, PA 19034, USA
Abstract The Bode plot, displayed as either impedance or admittance versus frequency, is the most basic test used by ultrasonic transducer designers. With simplicity and ease-of-use, Bode plots are ideal for baseline comparisons such as spacing of parasitic modes or impedance, but quite often the subtleties that manifest as poor process control are hard to interpret or are nonexistence. Inprocess testing of transducers is time consuming for quantifying statistical aberrations, and assessments made indirectly via the workpiece are difficult. This research investigates the use of advanced Bode plot techniques to compare ultrasonic transducers with known “good” and known “bad” process performance, with the goal of a-priori process assessment. These advanced techniques expand from the basic constant voltage versus frequency sweep to include constant current and constant velocity interrogated locally on transducer or tool; they also include up and down directional frequency sweeps to quantify hysteresis effects like jumping and dropping phenomena. The investigation focuses solely on the common PZT8 piezoelectric material used with welding transducers for semiconductor wire bonding. Several metrics are investigated such as impedance, displacement/current gain, velocity/current gain, displacement/voltage gain and velocity/voltage gain. The experimental and theoretical research methods include Bode plots, admittance loops, laser vibrometry and coupled-field finite element analysis. © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2014 The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-reviewunder under responsibility of Ultrasonic the Ultrasonic Industry Association. Peer-review responsibility of the Industry Association
Keywords: Ultrasonic transducer; Wire bonding; Bode plots; Piezoelectric; PZT8; Vibrometer; Coupled-field FEA; ANSYS 1. Introduction The Bode plot, displayed as impedance or admittance versus frequency, is the most basic test used by ultrasonic transducer designers. With simplicity and ease-of-use, Bode plots are ideal for baseline comparisons such as spacing of parasitic modes and impedance. But, quite often the subtleties that manifest as poor process control are hard to interpret or are nonexistent from standard Bode plots. In-process testing of transducers is time consuming for quantifying statistical aberrations, and assessments made indirectly via the workpiece are difficult for identifying
1875-3892 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Ultrasonic Industry Association doi:10.1016/j.phpro.2015.03.002
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D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
cause and effect relationships. Transducer modal surveys require an expensive scanning laser vibrometer and interpretation is esoteric. Advanced bode plot techniques are needed for a-priori process assessment of ultrasonic transducers. 2. Specific transducer application Kulicke & Soffa Industries is the leading manufacturer of semiconductor wire bonding equipment. This “backend” type of equipment provides ultrasonically welded interconnect wires between the wafer level semiconductor circuitry (die) and the mounting package (frame) as shown in Fig. 1. The ultrasonic transducer delivers energy to a capillary tool for welding tiny gold or copper wires, typically on the order of .001 inches in diameter. Fig. 2 shows the primary steps of the wire bond cycle used to produce the interconnect wires, and how the ultrasonic energy from the transducer is delivered in a “scrubbing motion” to make the welded bonds. Fig. 1(d) shows the on-machine configuration. The single-piece construction “Unibody” transducer uses four diced, rectangular PZT8 piezoceramics, and is ideal for research studies (DeAngelis et al., 2006, 2009, 2010). Portability across 100’s of machines is required for the same customer device in production operations. (a)
Piezo Stack
(b)
Transducer Body
(c)
(d)
On IConn Machine Transducer
1¢ US
New IConn Transducer
Device Die
Capillary Tool
Capillary EFO (Spark)
Fig. 1. (a) K&S “Unibody” ultrasonic transducer, (b) Ceramic capillary tool tip with fine gold wire compared to sewing needle, (c) Actual wire bonds from multi-tier package, (d) On-machine configuration of “Unibody” transducer during device wire bonding.
c
e
d Fig 2. Primary steps 1, 2 and 3 of the wire bond cycle
3. Assessment methodology What aspects of transducer performance are important for ideal process control (Stansfield, 1991, Wilson, 1991, Sherman et al., 2007, Uchino et al., 2003)? The mechanical interfaces must behave linearly in vicinity of the operating mode, such that there is no separation or “gapping” with drive level or frequency change (DeAngelis et al., 2009, 2010); the critical interfaces are tool-to-clamp and the piezoceramic stack. The displacement gain of all surfaces must behave linearly in vicinity of the operating mode and proportional to drive level: the displacement/current gain should be linear in vicinity of resonance, and the displacement/voltage gain should be linear in vicinity of antiresonance (DeAngelis et al., 2006). The tool motions must be consistent in all directions above and below the operating mode: in-plane motions remain in-plane, and linear motions remain linear and in same direction. No local parasitic resonances should be competing with the operating mode; parasitic coupling has a 180° phase change when driven through the operating mode. The usual suspects are shim electrodes, tool clamps, screws and tools. Shim electrode resonances are hard to detect since their manifestation can vary wildly with slight
4
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
change of operating frequency. There should be no hysteresis in frequency or displacement gain with sweep direction; the phase lock loop (PLL) can approach arbitrarily from either side, and thus hysteresis can cause phase/amplitude oscillation or failure of PLL to lock at resonance. Interface gapping can change with phase of parasitic coupling above and below operating mode, causing hysteresis in gain and frequency. Internal self-heating effects from impedance are different above and below operating mode due to antiresonance and sweep start direction. 4. Research summary Advanced Bode plot techniques were developed from the basic constant voltage versus frequency sweep; this included constant current and constant velocity interrogated locally on transducer (Uchino et al., 2003, Ural et al., 2009), with added up and down directional frequency sweeps to quantify hysteresis effects (Umeda et al., 2000). Selected transducers with known “good” and known “bad” process control were studied, and a linear coupled-field FEA model was correlated to the “good” transducer. The advanced Bode plot methodology for a-priori process assessment was established based on these comparisons. 5. Experimental methods and metrics Fig. 3 shows the hardware setup for the advanced Bode plot technique. Fig. 4 shows the methodology for velocity interrogation. The tool is the “business end” of the transducer and should be a starting point. The tool clamp is a close second for interrogation, since it may exhibit more non-linearities than tool with free-air assessment (i.e., off work). As shown in Fig. 5, the piezoceramic stack should also be another target area, and especially for Langevin or sandwich transducers which are prone to uneven preload stress. High power piezo stacks can rely on adhesives in tension which can fail, and shims and preload bolts are dynamic components that are prone to resonate. Amp 10:1
Transducer
Laser Vibrometer Polytec OFV 056
Laser Beam V-ref
LV
Laser Dot
100Ω Resistor
V-out
I-in
V-Probe
Network Analyzer HP E5100A
Oscilloscope Tektronics DPO7054
Ultrasonics Power Amp 4:1
Attenuator
Vel-in
Vel
NA
I-Probe OS GPIB I/O
VB OS
GPIB I/O Function Generator HP 33120A NA
LV GPIB I/O
USB I/O
USB/GPIB Interface Agilent 82357B
PC Command Center (Visual Basic Program)
Four LCD Monitors
Fig. 3. Advanced Bode plot technique hardware setup. Top or Tip of Tool in -Y Direction (Operating Mode Direction)
Top or Tip of Tool in X Direction
Tip of Tool in Z Direction Laser Dot (Z-Tip)
Laser Dot (X-Top)
Laser Dot (Y-Top)
Y
Z
Z Laser Dot (X-Tip) Y
Laser Dot (Y-Tip)
X
X Shim Electrode in -Y Direction
Piezo Stack in Z Direction
Tool Clamp in -X Direction
Laser Dot (Y-Shim)
Z
Y
Laser Dot (X-Clamp)
Y X
Z Laser Dot (Z-Stack)
X
Fig. 4. Methodology for velocity interrogation.
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
K&S Orthodyne Large Wire Wedge Bond Transducer (Langevin Style with Bolted Piezo Stack Driver) K&S Maxum Ultra Transducer (Previous Model Transducer for Ball Bonding) Preload Bolt
Shim Electrodes
Tool Clamp (Set Screw)
Piezo Stack Tool Clamp (Split)
Piezo Stack Driver (Thru Bolted) Wedge Tool (Long and Heavy WC)
Screw Preload Wedge (3Pc.)
Ceramic Tool
Fig 5. Velocity interrogation target areas for typical transducers.
6. Finite element modeling Fig. 6 shows the piezoelectric coupled-field finite element model from the ANSYS software with coupling via “stiffness” matrix which includes the piezoelectric properties for PZT8 material. The nodes have structural (X, Y, Z displacements) and electric (volt) degrees of freedom. The linear model was created without interface gapping (i.e., no gap elements) to correlate to the “good” transducer, and a constant damping ratio of 0.2% was used for all materials. The forced response was generated using a sine-sweep voltage input to the piezoceramic stack. Fig. 7 shows the FEA derived Bode results for clamp and top of capillary tool in the X-Clamp, X-Top and Y-Top directions as shown in Fig. 4; there is no hysteresis with the linear model, so results are independent of sweep direction. Fig. 8 shows the FEA derived gain ratio results for these same directions. The current and velocity gains are the same with a FEA linear model.
Orange: Electrode
Piezo Ceramics
Yellow: +Y Poled Green: -Y Poled
Fig. 6. Piezoelectric coupled-field finite element model in ANSYS software.
X-Clamp
X-Top
Y-Top Capillary Tool
Fig. 7. FEA derived Bode results for clamp and top of capillary.
5
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D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
X-Clamp
Y-Top
X-Top
Capillary Tool
Fig. 8. FEA derived gain ratio results for clamp and top of capillary.
7. Experimental results Figs. 9-12 show the advanced Bode technique results for the “good” transducer with the expected or “good” process response. As shown in Fig. 4, the velocity interrogation locations are X-Clamp, X-Top and Y-Top. The gain ratio results presented in Fig. 12 are for comparison to the linear FEA model, to demonstrate that a “good” process response is inherently a linear response. Figs. 13-17 show the advanced Bode technique results for the “bad” transducer with poor process response (i.e., inconsistent shears). The velocity interrogation locations are the same as the “good” transducer. - Hysteresis Gets Worse for
100
1.65
80
1.50
60
1.35
Tool Clamp in -X Direction
1.20
0.90 0.75
40 20
1.05
Slope Change
0
Laser Dot
0.60
-20 -40
0.45 -60
Hysteresis
0.30
Increasing Current (Normal Due to Heating)
- Fairly Constant Current Gain with Sweep Direction and Drive Level - Some Degradation in Tool Clamping for Higher Current (Typical)
-80
0.15 0.00 121700
Admittance Phase (Deg)
Displacement/Current (um/A)
Constant Current Feedback SF5505-13 IConn 1.80
121800
121900
122000
122100
122200
122300
122400
122500
122600
-100 122700
Frequency (Hz)
0.060
75
0.055
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45
0.045
30
0.040
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0.035
0
0.030
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0.025
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0.020
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0.015
-60
0.010
-75
0.005
-90
0.000 121700
121800
121900
122000
122100
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122300
Frequency (Hz)
122400
122500
122600
-105 122700
0.055
100
0.050
80
0.045
60
0.040
40
0.035
20
0.030 0 0.025 -20
0.020
-40
0.015
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0.010
-80
0.005 0.000 121700
121800
121900
122000
122100
122200
122300
122400
122500
Frequency (Hz)
Fig. 9. Constant current Bode for “good” transducer with X-Clamp velocity.
122600
-100 122700
Admittance Phase (Deg)
90
Admittance Mag (S)
Constant Current Feedback SF5505-13 IConn 105
0.065
Admittance Phase (Deg)
Displacement/Voltage (um/V)
Constant Current Feedback SF5505-13 IConn 0.070
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D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
0.050
100
90
0.045
80
1.1
75
1.0
60
0.040
60
0.9
45
0.035
40
0.8
30
0.030
20
0.7
15
0.025
0
0.020
-20
0.015
-40
0.010
-60
0.5 0.4 0.3
Admittance Phase (Deg)
~Same Gain as Clamp
0.6
0 -15 -30 -45
0.2
-60
0.1
0.005
-75 121800
121900
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122100
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122500
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-100 122700
Frequency (Hz)
Frequency (Hz)
Feedback Voltage 7V 5V 8V
Legend Red Green Blue
- Fairly Constant Gain With Current/Velocity - X-Clamp/X-Top Current Gain Nearly 1:1
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
Vibrometer Range 5 mm/s/V 25 mm/s/V 25 mm/s/V
Constant Velocity Feedback SF5505-14 IConn 75
1.0
60
0.9
45
Tool Top in -X Direction
0.8
30
0.7
15
0.6
0
0.5
-15
Laser Dot
0.4 0.3
Admittance Phase (Deg)
90
1.1
-30 -45
0.2
Displacement/Voltage (um/V)
Constant Velocity Feedback SF5505-14 IConn
1.2
0.045
100
0.040
80
0.035
60
0.030
40
0.025
20
0.020
0
0.015
-20
0.010
-40
Admittance Phase (Deg)
0.0 121700
Displacement/Current (um/A)
Admittance Phase (Deg)
Constant Current Feedback SF5505-14 IConn 105
1.2
Displacement/Voltage (um/V)
Displacement/Current (um/A)
Constant Current Feedback SF5505-14 IConn 1.3
-60
0.1
0.005
-75
0.0 121700
121800
121900
122000
122100
122200
122300
122400
122500
122600
-60
0.000 121700
-90 122700
121800
121900
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122100
122200
122300
122400
122500
122600
-80 122700
Frequency (Hz)
Frequency (Hz)
Fig. 10. Constant current/velocity Bode for “good” transducer with X-Top velocity.
75
5.0
60
4.5
45
4.0
30
3.5
15
3.0
0
2.5
-15
2.0
-30
1.5
-45
1.0
-60
0.5
-75 121800
121900
122000
122100 122200 122300 Frequency (Hz)
122400
122500
100
0.225
80
0.200
60
0.175
40
0.150
20
0.125
0
0.100
-20
0.075
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0.050
-60
0.025
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0.000 121700
-90 122700
122600
0.250
121800
121900
122100
122200
122300
122400
122500
122600
-100 122700
Frequency (Hz)
Legend Red Green Blue
Feedback Vibrometer Voltage Range 8V 25 mm/s/V 5V 125 mm/s/V 8V 125 mm/s/V
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
- Very Consistent Gain With Current/Velocity - Overall Great Performance Constant Velocity Feedback SF5505-16 IConn
Constant C t tV Velocity l it F Feedback db k SF5 SF5505-16 IConn 6.50
105
0.275
80
6.00
90
0.250
65
5.50
75
0.225
50
5.00
60
0.200
35
0.175
20
0.150
5
0.125
-10
0.100
-25
0.075
-40
45
4.00
30
3.50
15
3.00
0
Laser Dot
2.50
-15
2.00
-30
1.50
-45
1.00
-60
0.50
-75
0.00 121700
121800
121900
122000
122100
122200
122300
122400
122500
Admittance Phase (Deg)
Tool Top in -Y Direction
4.50
Displacement/Voltage (um/V)
Displacement/Current (um/A)
122000
-55
0.025
-90 122700
122600
0.050
0.000 121700
Admittance Phase (Deg)
0.0 121700
Admittance Phase (Deg)
90
5.5
Admittance Phase
Constant Current Feedback SF5505-16 IConn 105
6.0
Displacement/Voltage (um/V)
Displacement/Current (um/A)
Constant Current Feedback SF5505-16 IConn 6.5
-70 121800
121900
122000
122100
122200
122300
122400
122500
122600
-85 122700
Frequency (Hz)
Frequency (Hz)
Fig. 11. Constant current/velocity Bode for “good” transducer with Y-Top velocity.
60
19%
45
18%
30
17%
14% 13% 12% 11%
15
FEA Predicted 20%
X-Top Y-Top Gain Ratio
10% 121700
121800
121900
122000
122100
122200
122300
122400
122500
122600
0 -15 -30 -45 -60 -75
-90 122700
121800
121900
122000
80 70 60
28% 27% 26% 25% 24%
50 40 30 20 10
23% 22% 21% 20%
0 -10 -20 -30
FEA Predicted 25%
X-Clamp Y-Top Gain Ratio 121900
122000
122100
122200
122400
122500
122600
122600
100 90 80 70 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 122700
122300
122400
122500
122600
36%
-40 -50 -60 -70 -80 122700
33% 30% 27% 24% 21% 18% 15% 12% 9% 6% 3% 0% 121700
121800
121900
122000
Frequency (Hz)
Constant Current Feedback SF5505-13-14 IConn
122100 122200 122300 Frequency (Hz)
122400
122500
Constant Current Feedback SF5505-13-14 IConn 90
300%
90
155%
75
275%
75
150%
60
250%
60
145%
45
225%
45
140%
30
200%
30
135%
15
175%
15
130%
0
150%
0
125%
-15
100%
-30
125% 120% 115% 110% 105%
FEA Predicted 130%
X-Clamp X-Top Gain Ratio
100% 121700
121800
121900
122000
122100
122200
122300
Frequency (Hz)
122400
122500
122600
-15 -30 -45 -60 -75
-90 122700
Admittance Phase (Deg)
160%
Voltage Gain Ratio X-Clamp/X-Top
Current Gain Ratio X-Clamp/X-Top
122300
39%
Admittance Phase (Deg)
31% 30% 29%
121800
122200
Constant Current Feedback SF5505-13-16 IConn
Voltage Gain Ratio X-Clamp/Y-Top
Current Gain Ratio X-Clamp/Y-Top
Constant Current Feedback SF5505-13-16 IConn
19% 18% 17% 16% 15% 121700
122100
Frequency (Hz)
Frequency (Hz)
Admittance Phase (Deg)
15%
80 70 60 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 -80 122700
75%
-45
50%
-60
25% 0% 121700
-75
121800
121900
122000
122100
122200
122300
Frequency (Hz)
Fig. 12. Gain ratios with X and Y velocities for “good” transducer.
122400
122500
122600
-90 122700
Admittance Phase (Deg)
16%
32% 30% 28% 26% 24% 22% 20% 18% 16% 14% 12% 10% 8% 6% 4% 2% 0% 121700
Admittance Phase (Deg)
75
20%
Admittance Phase (Deg)
Constant Current Feedback SF5505-14-16 IConn 90
21%
Voltage Gain Ratio X-Top/Y-Top
Current Gain Ratio X-Top/Y-Top
Constant Current Feedback SF5505-14-16 IConn 22%
8
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
Current/Voltage 083006-1 Maxum
Tool Clamp in -X Direction
120
55
100
50
80
45
60
Mag
40
40
Normal Bode Response
35 30 25
Mag Down
20
Phase
0
Phase Down
-20
20
-40
15
-60
10
Laser Dot
Admittance Phase (Deg)
Admittance Mag (mS)
60
-80
5
-100
0 100
102
104
106
108
110
112
114
116
118
120
122
124
126
128
130
132
134
136
-120 140
138
Frequency (kHz)
Velocity/Voltage 083006-1 Maxum 1200
20 10
Mag
Mag Down
Phase
Phase Down
1000 800
-10 -20
600
-30
400
-40
200
-50
Phase (Deg)
Unit Velocity/Volts (dB)
0
Current/Voltage Admittance Loop 40
0
-60
30 -200
-70 -80 102
104
106
108
110
112
114
116
118 120 122 Frequency (kHz)
124
126
128
130
132
60 50 Unit Velocity/Amps (dB)
40
Mag Down
Phase
Phase Down
136
-400 140
138
Suspect -25dB Down
Velocity/Current 083006-1 Maxum
Mag
134
20 10 B (mS)
100
1200 1000
0 -10
0
10
20
30
40
50
60
800
30 600
10
400
0
200
-10
Phase (Deg)
20
-20
-10 0
-20
-30
-200
-30 -40 100
102
104
106
108
110
112
114
116
118
120
122
124
126
128
130
132
134
136
-400 140
138
-40 G (mS)
Frequency (kHz)
Fig. 13. Standard Bode for “bad” transducer with X-Clamp velocity. 100
2.00
80
1.75
60
1.50
40
1.25
20
1.00
0
Tool Clamp in -X Direction Laser Dot
0.75
-20
0.50
-40
0.25
-60
0.00 123600
123700
123800
- Hysteresis Gets Worse for Increasing Current (Normal Due to Heating)
123900
124000
124100
124200
124300
124400
124500
- Fairly Constant Current Gain with Sweep
Admittance Phase (Deg)
Displacement/Current (um/A)
Constant Current Feedback 083006-4 Maxum Ultra 2.25
Direction and Drive Level
- Some Degradation in Tool Clamping for Higher Current (Normal)
-80 124600
Frequency (Hz)
90
0.055
75
0.08
60
0.050
60
0.045
45
0.040
30
0.035
15
0.030
0
0.025
-15
0.020
-30
0.015
-45
0.010
-60
0.07
40
0.06
20
0.05
0
0.04
-20
0.03
-40
0.02
-60
0.01 0.00 123600
Admittance Mag (mS)
0.060
80 Admittance Phase (Deg)
Displacement/Voltage (um/V)
100
0.09
-80
123700
123800
123900
124000
124100
124200
124300
124400
124500
0.005
-100 124600
0.000 123600
Admittance Phase (Deg)
Constant Current Feedback 083006-4 Maxum Ultra
Constant Current Feedback 083006-4 Maxum Ultra 0.10
-75 123700
123800
123900
Frequency (Hz)
124000
124100
124200
124300
124400
124500
-90 124600
Frequency (Hz)
Fig. 14. Constant current Bode for “bad” transducer with X-Clamp velocity. 90
2.0
75
1.8
60 45
Tool Clamp in -X Direction
1.4
30
Laser Dot
1.2
15
1.0
0
0.8
-15
0.6
-30
0.4
-45
0.2
-60
0.0 123600
123700
123800
123900
124000
124100
124200
124300
124400
124500
-75 124600
Frequency (Hz)
- Little Hysteresis with Sweep Direction - No Serious Issues at Interface from Parasitic Modes Legend Red Green Blue
Vibrometer Range 5 mm/s/V 25 mm/s/V 25 mm/s/V
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
Constant Velocity Feedback 083006-4 Maxum Ultra 100
0.060
90
0.09
80
0.055
75
0.08
60
0.050
60
0.045
45
0.040
30
0.035
15
0.030
0
0.025
-15
0.020
-30
0.015
-45
0.010
-60
0.07
40
0.06
20
0.05
0
0.04
-20
0.03
-40
0.02
-60
0.01
-80
0.00 123600
123700
123800
123900
124000
124100
124200
Frequency (Hz)
124300
124400
124500
-100 124600
Admittance Mag (S)
0.10
Admittance Phase (Deg)
Displacement/Voltage (um/V)
Constant Velocity Feedback 083006-4 Maxum Ultra
Feedback Voltage 12V 8V 14V
0.005 0.000 123600
-75 123700
123800
123900
124000
124100
124200
124300
Frequency (Hz)
Fig. 15. Constant velocity Bode for “bad” transducer with X-Clamp velocity.
124400
124500
-90 124600
Admittance Phase (Deg)
1.6
- Fairly Consistent Gain with Sweep Direction and Velocity Level Admittance Phase (Deg)
Displacement/Current (um/A)
Constant Velocity Feedback 083006-4 Maxum Ultra 2.2
9
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
80 60
0.150
40
0.125
20
0.100
0
0.075
-20
0.009
100
0.008
80
0.007
60
0.006
40
0.005
20
0.004
0
0.003
-20
0.002
-40
0.001 0.050
Admittance Phase (Deg)
100
Displacement/Voltage (um/V)
0.175
Displacement/Current (um/A)
Constant Current Feedback 083006-2 Maxum Ultra
Phase Changes Seen
0.200
Admittance Phase (Deg)
Constant Current Feedback 083006-2 Maxum Ultra 0.225
-60
-40
0.025
0.000 123600
-60
123700
123800
123900
124000
124100
124200
124300
124400
124500
-80 124600
Frequency (Hz) 0.000 123600
123700
123800
123900
124000
124100
124200
124300
124400
124500
- Displacement Stability Issues with Current &
-80 124600
Frequency q (Hz)
Legend Red Green Blue
Feedback Voltage .5V 1V 2V
Velocity Feedback - Velocity Feedback Unstable Above 2V Due to Oscillation (Non-Sinusoidal Velocity Waveform) - X-Clamp/X-Top Current Gain >10 (Gapping)
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
Vibrometer Range 5 mm/s/V 5 mm/s/V 5 mm/s/V
Constant Velocity Feedback 083006-5 Maxum Ultra 0.10
100
0.09
80
0.08
60
0.07
40
0.06
20 0
0.04
-20
0.03
-40
0.02
-60
Laser Dot
0.01 0.00 123700
-80
123800
123900
124000
124100
124200
124300
80
0.004
60
0.003
40
0.003
20
0.002
0
0.002
-20
0.001
-40
0.001
-100 124500
124400
100
0.004
0.000 123700
Admittance Phase (Deg)
0.05
Admittance Phase (Deg)
Tool Top in –X Direction
Displacement/Voltage (um/V)
Displacement/Current (um/A)
Constant Velocity Feedback 083006-5 Maxum Ultra 0.005
-60
123800
123900
124000
124100
Frequency (Hz)
124200
124300
124400
-80 124500
Frequency (Hz)
Fig. 16. Constant current/velocity Bode for “bad” transducer with X-Top velocity. 105
0.30
90
0.28
75
0.25
60
0.23
45
4.5 4.0 3.5 3.0
30 15 0 -15
0.20
30
0.18
15
0.15
0
0.13
-15
0.10
-30
0.08
-45
10% Increase
0.5 0.0 123600
123700
123800
-30 -45 -60 -75
123900
124000
124100
124200
124300
124400
124500
0.05
-60
0.03
-90 -105 124600
0.00 123600
-75 123700
123800
123900
124100
124200
124300
124400
124500
-90 124600
Frequency (Hz)
Frequency (Hz) Frequenc
Legend Red Green Blue
Feedback Voltage 8V 5V 8V
Vibrometer Range 25 mm/s/V 125 mm/s/V 125 mm/s/V
Sweep Up Down Solid Dashed Solid Dashed Solid Dashed
- Inconsistent Gain With Current/Velocity (∆10%) - Overall Fair Performance - Root Cause: Found MFG Error in Tool Hole - Difficult to Detect with Incoming Inspection
Constant Velocity Feedback 083006-2 Maxum Ultra
Constant Velocity Feedback 083006-2 Maxum Ultra 105
0.325
105
6.5
90
0.300
90
6.0
75
0.275
75
5.5
60
0.250
60
5.0
45
0.225
45
4.5
30
0.200
30
0.175
15
0.150
0
0.125
-15
0.100
-30
0.075
-45
-75
0.050
-60
-90
0.025
4.0
Tool Top -Y Direction
15
3.5
0
3.0
-15
2.5
-30
2.0
-45
1.5
-60
1.0
Laser Dot
0.5 0.0 123600
123700
123800
123900
124000
124100 Frequency (Hz)
124200
124300
124400
124500
-105 124600
Admittance Phase (Deg)
7.0
Displacement/Voltage (um/V)
Displacement/Current (um/A)
124000
0.000 123600
Admittance Phase (Deg)
2.5 2.0 1.5 1.0
Admittance Phase (Deg)
0.33
90 75 60 45
Displacement/Voltage (um/V)
Displacement/Current (um/A)
120 105
6.5 6.0 5.5 5.0
Admittance Phase (Deg)
Constant Current Feedback 083006-2 Maxum Ultra
Constant Current Feedback 083006-2 Maxum Ultra 7.5 7.0
-75 123700
123800
123900
124000
124100
124200
124300
124400
124500
-90 124600
Frequency (Hz)
Fig. 17. Constant current/velocity Bodes for “bad” transducer with Y-Top velocity.
8. Conclusions The transducer with “good” process performance conforms to behavior as predicted by the ideal linear FEA model with glued interfaces (i.e., no gap elements). Non-linear behavior in the tool was shown to be the root cause of poor process (i.e., low shear force): manufacturing error exacerbated inherent design problem in the tool clamp. Phase changes from closely spaced parasitic modes can lead to hysteresis effects due to interface gapping as seen from the non-sinusoidal velocity profile; heating effects can also cause hysteresis. Velocity based Bode plots can pick-up subtleties typically overlooked without a full laser vibrometer modal survey. A unique set of interrogation locations and assessment criteria is required for each specific transducer design and process application; wire bonding is inordinately sensitive to tool motions due to delicate balance of forces exerted on tiny ball and micro bond pad structure; inconsistent energy delivery to the tool is a root cause of poor process.
10
D.A. DeAngelis and G.W. Schulze / Physics Procedia 63 (2015) 2 – 10
References C. H. Sherman and J. L. Butler, Transducers and Arrays for Underwater Sound. New York, NY: Springer Science, 2007. D. A. DeAngelis and D. C. Schalcosky, “The Effect of PZT8 Piezoelectric Crystal Aging on Mechanical and Electrical Resonances in Ultrasonic Transducers,” 2006 IEEE Ultrasonics Symposium, Session P2O-10. D. A. DeAngelis, G. W. Schulze, “Optimizing Piezoelectric Ceramic Thickness in Ultrasonic Transducers,” 2010 UIA Symposium Proceedings, IEEE XPlore. D. A. DeAngelis, G. W. Schulze, “Optimizing Piezoelectric Crystal Preload in Ultrasonic Transducers,” 2009 UIA Symposium Proceedings, IEEE XPlore. D. Stansfield, Underwater Electroacoustic Transducers. Los Altos, CA: Peninsula Publishing, 1991. K. Uchino and J. R. Giniewicz, Micromechatronics. New York, NY: Marcel Dekker, 2003. M. Umeda, K. Nakamura, S. Takahashi, S. Ueha, “An Analysis of Jumping and Dropping Phenomena of Piezoelectric Transducers using the Electrical Equivalent Circuit Constants at High Vibration Amplitude Levels,” Japanese Journal of Applied Physics Vol. 39 (2000) pp. 56235628. O. B. Wilson, Introduction to Theory and Design of Sonar Transducers. Los Altos, CA: Peninsula Publishing, 1991. S. O. Ural, S. Tuncdemir, Y. Zhuang, K. Uchino, “Development of a High Power Piezoelectric Characterization System and Its Application for Resonance/Antiresonance Mode Characterization,” Japanese Journal of Applied Physics 48 (2009) 056509.