US20120279865A1

US20120279865A1 - Touch Fingerprint Sensor Using 1-3 Piezo Composites and Acoustic Impediography Principle

Info

Publication number: US20120279865A1
Application number: US13/289,391
Authority: US
Inventors: Louis Regniere; Yakub Aliyu; Rainer M. Schmitt; Theodore M. Johnson; Ronald A. Kropp; Christian Liautaud; Deda Diatezua; Isaac R. Abothu; De Liufu; Richard Irving; Patrick D. Brown; Walter C. Mick; William H. Tanubrata; Omid S. Jahromi; John BOUDREAUX; David B. Clarke; Jack S. Chorpenning; Bryce M. Barbato; Honorio R. Ulep; William R. Robinson, Jr.
Original assignee: Sonavation Inc
Current assignee: Sonavation Inc
Priority date: 2010-11-04
Filing date: 2011-11-04
Publication date: 2012-11-08
Also published as: WO2012061740A3; WO2012061740A2

Abstract

Provided herein is a method of making an integrated circuit device using copper metallization on 1-3 PZT composite. The method includes providing an overlay of electroplated immersion of gold (Au) to cover copper metal traces, the overlay preventing oxidation on 1:3 PZT composite with material. Also included is the formation of immersion Au nickel electrodes on the 1-3 PZT composite to achieve pad metallization for external connections.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/410,236, filed Nov. 4, 2010, entitled “Touch Fingerprint Sensor Using 1-3 Piezo Composites and Acoustic Impediography Principle,” which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention is generally directed to 1-3 PZT composite sensors.
2. Background Art
Improved concepts are needed for fingerprint touch sensors based on the use of 1-3 piezo-composite and the principle of ultrasonic impediography.

BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention are made with respect to principle sensor performance, sensor design and manufacturing as well as packaging. Additional hardware and software implementations are described addressing MTF performance. An improved concept for a fingerprint touch sensor based on the use of 1-3 piezo-composite and the principle of ultrasonic impediography is presented. Improvements are made with respect to principle sensor performance, sensor design and manufacturing as well as packaging. Additional hard and software implementations are described addressing MTF performance. The existing ASIC hardware is described separately in the respective ASIC development description. The software package for sensor control, data analysis and fingerprint presentations is implemented and contained in USB software stick already distributed to customers.
An exemplary sensor can have an area of up to 1.5″ by 1.6″ and an element pitch of 500 dpi. More specific features are provided below that address improving the touch sensor by packaging, sensor design, sensor construction, software/hardware concepts for MTF control, and various sensing principles.
Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention.

FIG. 1 is an STS 3050 assembly overview;

FIG. 2 is a diagram of flex circuit sensor connections;

FIG. 3 is a diagram of an exemplary sensor footprint;

FIG. 4 is an exploded (CAD) view;

FIG. 5 is an exemplary assembly step 1 mount;

FIG. 6 is an exemplary assembly step 2 mount;

FIG. 7 is an illustration of a bonding platform;

FIG. 8 is an exemplary step 3;

FIG. 9 is an exemplary step 4;

FIG. 10 is an exemplary step 5;

FIG. 11 is an exemplary step 6;

FIG. 12 is an exemplary step 7;

FIG. 13 is an exemplary step 8;

FIG. 14 is an exemplary completion step;

FIG. 15 is an exemplary step by step overview;

FIG. 16 is an exemplary sensor array;

FIG. 17 is an exemplary flex use for creating a package;

FIG. 18 is an exemplary molded base and touch sensor;

FIG. 19 is an exemplary 1-3 composite sensor using fine pitch high density;

FIG. 20 is an exemplary flex with stiffener as backer;

FIG. 21 is an exemplary flex with plastic polymer with molded base as backer;

FIG. 22 is an exemplary flex with plastic polymer with molded base and bezel;

FIG. 23 is an exemplary flex with plastic polymer with molded base and bezel (with the stakes pulled over);

FIG. 24 is an exemplary 3050 sensor structure diagram;

FIG. 25 is representative of exemplary sensor products;

FIG. 26 is representative of a first set of exemplary sensor manufacturing processes;

FIG. 27 is representative of a second set of exemplary manufacturing processes;

FIG. 28 is representative of assembly suggestions;

FIG. 29 is representative of 3050 sensor ultrasonic experimental results;

FIG. 30 is an illustration of exemplary sensor bonding test results;

FIG. 31 is an illustration of sensor side bonding test results;

FIG. 32 is illustration of exemplary thermo compression bonding;

FIG. 33 is an illustration of an ultrasonic bonding experiment;

FIG. 34 is an illustration of simultaneous bezel and sensor attachment;

FIG. 35 is an exemplary illustration of ACP use instead of ACF;

FIG. 36 is an exemplary illustration of rigid and flex use packaging;

FIG. 37 is an exemplary illustration bezel pre- attachment to a sensor;

FIG. 38 is an illustration of experimental equipment;

FIG. 39 is an illustration of an experimental material sample;

FIG. 40 illustration of experimental targets;

FIG. 41 is an illustration of a second set of experiments targets;

FIG. 42 is an illustration of a test the layout on a substrate;

FIG. 43 is an illustration of gold coated composite drilling test results;

FIG. 44 is an illustration of a second set of gold coated composite drilling test results;

FIG. 45 includes exemplary comments regarding gold coated composites;

FIG. 46 is a first exemplary illustration of Ohashi ACF-10- test equipment;

FIG. 47 is a second illustration of exemplary test equipment;

FIG. 48 is a third illustration of exemplary test equipment;

FIG. 49 is a fourth illustration of exemplary test equipment;

FIG. 50 is a fifth illustration of exemplary test equipment; and

FIG. 51 is an exemplary Sensor FEM Model evaluating sensor performance properties for fingerprinting using impediography.

The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention provide methods and systems related to integrated circuit (IC) fabrication on 1-3 PZT composite material. In the detailed description that follows, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
Packaging. Exemplary packaging are illustrated in items 1 to 40 shown below.
1.—Sensor on FLEX using ACF attach; existing technology, as shown in FIGS. 1-15.
2.—In line and/or staggered pads (patent pending). Folded FLEX package for double sided sensors (STS3000 first package)—method previously developed for tiger referenced as an alternative concept creating a one sided ASIC attachment scheme.
3.—FLEX with stiffener as backer (eliminates backer assembly step).
4.—FLEX with plastic/polymer molded base (eliminates backer assembly step).
5.—FLEX with plastic/polymer molded base & Bezel (eliminates backer & simplifies bezel assembly).
6.—FLEX with plastic/polymer molded base & Bezel+heat staking
7.—ACF used to seal sensor /bezel interstitial gap, as illustrated in FIGS. 20-23, for steps 3-7.
8.—Conductive layer for ESD protection (For the touch sensors we will need a conductive coating. ideally something we can spin on not much thicker than what we do with SU8).
9.—Vias in composite material (see, for example FIGS. 38-45) vias are connecting electrodes from one side of the sensor to the other side facilitating bonding. Feasibility with drilled and subsequently filled vias have been demonstrated previously; three more via technologies have been evaluated: vias created in green tiles and vias created within the dice and fill process as well as vias created by laser drilling.
10.—Thermal Compression ACF attach: a device for thermal bonding developed and approved for mfg.—(FIGS. 46-50).
11.—Ultra Sonic ACF. Ultrasonic bonding is proposed to replace thermal ACF bonding reducing the heat risk.
See, for example, FIGS. 24-33 demonstrating thermal bonding.
Provided are calculations for a manual operation using both Thermal-Compression and Ultrasonic bonding methods with dual bonding heads. No backer assembly is considered in this calculation.


Sensor only	Sensor only	Sensor +	Sensor +
By US	By TC	Bezel By	Bezel By
bonding	bonding	US bonding	TC bonding

Bonding Tact

	15	15	20	20
time
For loading and
alignment (sec)
Bonding	5	15	5	15
time (sec)
Total bonding	20	30	20	30
time (sec)
Unit/min	6	4	4.8	3.5
(dual heads)
Unit/month	90K	60K	72K	52K
(unit)
Unit/year	1	0.7	0.87	0.63
(Million unit)

The major advantages of the US bonding are:

1) Low temperature fast bonding time
2) Less thermal damage to sensor
3) Higher throughput

For bonding the 3050 sensor and bezel as well as the proposed touch sensor the use of the MicroPack's 130 Dual Head US bonder is of advantage, whether the US bonding can be successfully done on the 3050 sensor plus bezel prototype assembly. If the test results come out good, Sonavation can consider MicroPack as not only an US bonding equipment manufacturer but also one of the Sonavation's sensor assembly houses as the STARS in Thailand.
12—Attach Bezel at same time as Sensor to create absolute flat surface.
13—ACP used for sensor to flex bonding (dispense/spray/screen print): See, for example, ACP technique FIG. 35.
14—Rigid+Flex substrate.
15—Pre-attach Bezel to Sensor (create a single pick & place part). See for example, FIGS. 34-37 and 46-50.
16—Low temp ACF Bonding to FLEX or PCB.
17—ACF Placement and flow control.
18—Sensor Support (mechanical support for air gap).
19—Pressure control Activation and release (HW team).
20—Vacuum placement on bonder.
21—Alignment of Bonder.
22—Alignment Sensor to Bonder. See FIGS. 1-15. Ref/8/.
23 ASIC /Mux for touch: ASICs mounted via sockets.
Sensor Design
24 Support Pillars proof via FEM study. See FIG. 51.
Optimized sensor design balancing pillar length and width and kerf, pzt and matrix material to maximize dynamic range separating ridge and valley while providing adequate electrical conditions (resistance at, resonance and resonance frequency). Parameters are evaluated using a model developed for Falcon geometry by selecting the appropriate parameters for Touch sensor geometry. validated in

Touch Sensor

24—Stitching 4 parts to make a bigger one—concept. See, for example, FIG. 16 and FIGS. 38-45.
25—Using 2 sides for connections to make above possible—same as above).
26—Folded FLEX packaging (similar to our first STS3000). See FIGS. 17 and 18
27—Touch interconnect using silver epoxy:
28—Touch interconnect using very low temperature solder:
29—Packaging using an Interposer;
30—SENSOR to PCB using FLEX as interposer:
31—Sensor mounted on PCB subassembly
32—ASIC mounted on PCB subassembly : Interposer drawing requested from Y
Ref/12/
33—Sensor mounted on PCB subassembly interconnect to ASICs mounted on
PCB subassembly.
34—Double sided PCB, sensor on one side and ASICs on the other side—similar to interposer.
35—In-line or staggered sensor pads.
36—ASIC perimeter or staggered bond pad.
37—Wire bonding ASIC & SENSOR TO PCB using highly staggered PCB connections Ref/12/ more supporting material for features 27-37 in progress

Touch Sensor Proof of Concept

38 Main & Interposer boards
39 Sensor to PCB attach process
40 Separate Rx & Tx ASIC arrangement
41 Clock & Reset synchronization of the surface prior to surface activation using immersion in palladium (Pd) based solution.
Current 1-3 composite of falcon geometry pitch 72 um, width 50 um and pillar height 150 um is approx 50 percent as measured with laser vibrometry and predicted by FEM modeling. Crosstalk is reduced, if the interstitional material exhibits a large difference (preferably a lower) to the PZT, e.g. air. However air will not keep the pillar in place. Currently Epotek 301-2 is deployed providing sufficient bonding strength to keep the pillars in place during grinding the process step exerting the largest force to the pillar during manufacturing. However, material with much lower acoustic impedance could be employed as for example epoxy fill with hollow glass spheres having a diameter of <1 um.
Another possibility are nano porous polymers currently under development, but with no known source of commercial production.
Note on Air like Backing of Transducers/Fingerprint touch sensor
Problem: Air backing is of advantage for ultrasound transducers as it increases the output amplitude by 30% according to the Redwood Transient Model. For the fingerprint sensor air backing is vital, as energy shall be transmitted in the front medium only. In both cases the sensors front propagation material is soft tissue a suitable backing must have much lower acoustic impedance approximately 0.1 MRayl as estimated from earlier calculations.¹ ¹Hard backing would be a solution too. However the hardest material, pure tungsten, has an ac. Impedance of 100 MRay leaving us with reflection coefficient of ˜0.74.
Particularly for the fingerprint touch sensor the backing is required for stability.
Proposed solution: Rough surface. The surface roughness of most material provides an interface to the fingerprint sensor, which is only partial in contact with the active sensor. Typically no acoustic contact is achieved without high static pressure. The reduced contact area of a rough surface is equivalent to an air like backing and can support the sensor.
Backing is provided by a layer sprinkled randomly with bumps having diameter less than a pillars width. These bumps provide the support for the sensor. Due to their round shape and small total area the transmission into the backing is kept low. The average distance between bumps will be chosen according the bending strength of the 1-3 piezo composite. For fingerprinting each bump may create a pillar failing reflecting the front loads. However, if the fingerprint is over sampled, filtering out those locations will not degrade the final result of the fingerprint matching schemes. The random scheme is used to destroy phase coherence for any transmission and wave propagation in the backing

Generating the Bump Feature

Bumps will be produced by a mold created from a random pattern. The random pattern is generated by first calculating a sub matrix with side length of half the stability distance of two supporting points. Bump locations are then created randomly within each sub-matrix, where the matrix length is much larger than the bump diameter.
Non linear contacts at the bottom interface is modified to the advantage of acoustic impediography for the acoustic load to be estimated placed on the top and pressed down by a static pressure. For example spherical random contacts are made at the interface, which under no static load provide a certain contact area. If the static load is increased, the contact area increase if a suitable contact point material is employed, e.g. RTV. If the contact area increases the damping is increase on locations where the acoustic top load is in acoustic contact with the sensor. For a sufficient resolution of this improved method a very flexible 1-3 composite substrate is required.
Software (contained in the development kit sent to customers: e.g. MAT
Libraries
SonicLib
Sparrow ASIC control and I/O
Mapping Tables
Dynamic Optimization
Bad Pixel detection and correction
Multiple ASIC capability
SonicPal—Platform abstraction layer (per platform)
Provides abstraction of hardware specific details and certain operating system functions, such as debug I/O and memory allocation.
SonicNav—Mouse and touch screen like navigation
PHAT based, or
Correlation based, or
Centroid based.
Inertial/Accelerator algorithm.
“Double Click” GUI algorithms.
Composer—Convert slices into fingerprint, non correlation based.
Innovatrics—We own rights to E&M code.
Sensor Image-processing Algorithms
Bad Pixel Processing
Sensor Resonance Detection
Dynamic Optimization
Enrollment Min-Max algorithm
Navigation
Pulse Rate (experimental)
Roll Stitching
PIV-like image calibration
SNR, MTF, Geometric correction, gray scale linearity.
Moving finger method of sensor loading for two point (loaded, unloaded) gain and offset calibration.
Applications
FEDS—Falcon Engineering Development System: basic engineering tool for testing all STS-xxxx products.
STARS—Diagnostic tool for STARS production.
Sonagnose—Diagnostic tool for sensor evaluation.
GIGO—SPI to USB converter.
MAPS—Matcher performance testing (EER).
Customer Demo Codes—used by marketing.
SonicLib and demo codes have been ported to:
Windows XP, Vista, 7
Windows CE (mobile)
Qualcomm
Symbian
Linux
Android
Non-OS ports to various ARM chips (NXP, Samsung, ST, Atmel, TI) and 8051)
MTF Enhancement and Noise-Reduction features—(software algorithms and state-machine logic) to be Implemented into the ASIC
41 Real-time Programmable Look-up table (SLUT)
42 Several preprogrammed SLUTS with the ability to use a predefined sequence of SLUTS to capture several images and combine.
43 Real-time adaptable look-up tables (SLUT) based on fingerprint grayscale (z-axis) and frequency-domain analysis (with finger on the sensor).
44 Real-time Programmable Tx amplitude envelope over time. (Used to normalize pixel excitation for individual Tx lines or Tx groups.)
45 Real-time programmable Rx Tx time-delay templates—they can be programmed to change as 1 image is captured, or for several image sequences, which would then be combined during post-processing.
46 Real-time programmable “differential” templates—any grouping of SLUTS, programmable Tx amplitude, and register-settings creates a template. Several templates are sequenced to produce several temporary images which are then “differentiated” to extract the high-quality final image.
47 Programmable PLL templates (might include SLUTS and register settings). May require several PLL templates, slightly varying off-resonance. Used to analyze the sensor before the finger touches the sensor. The individual pixel response to varying PLL frequency is used to predict/calibrate each pixel's sensitivity. (An off-resonance PLL was used successfully to enhance our original Tiger sensor's MTF.)
48 Any combinations of the above that may normalize pixel excitation across the sensor image to improve MTF.
49 Any combinations of the above that may positively affect standing-wave characteristics of the sensor image to improve MTF.
50 Any of the above that can be used to resolve the sensor's static and temporal noise signature, so that noise reduction can be applied.
51 Any combinations of the above, performed both before and after the finger touches the sensor, to reduce noise, and enhance MTF.
ASIC (defined by ASIC specs already sold to customer see also specs for Maverick, Sidewinder, Goldfinger, Lotus)
Digital architecture
Processor
Memory (ROM, SRAM, 1T-SRAM, OTP RAM)
Bus architecture
DMA controller
Encryption cores (AES, ECC, SHA, HMAC)
OTP RAM usage for security keys storage
Standard host interfaces
SPI/USB/UART/EBI/SDIO/7816
High security interface (challenge, encryption, key protocol)
Random number generator
External devices interface
Flash memory
ROM
SPI/UART/GPIO
BOOT timer
Sensor Controller
Special sequencing one TX at a time, some RX to minimize peak power consumption
Sensor LUT/Scan_Enable_LUT/Pixel Cache location mapping LUT (MAP_LUT)
Pattern Generator (test & debug)
Data-In-Cache Counter
Analog pipeline programmable delays
Rx start and end (ROI control)
Cache Controller
On board Image Histogram with adjustable levels
Navigation & Finger-detect LUT
Time Stamp (tick counter)
Hardware Assisted pixel/image averaging
Data Sum and Integer Mean (Hardware assisted)
Timer based image capture triggers
Rx/Tx Trigger
Analog interface to sensor
TX (amplitude control, filtering etc . . . )
RX (C2V, filter, Gain & Offset programmable amplifier, ADC)
Dynamic Gain/Offset adjustment per pixel/line/region (CAL_SELECT_LUT).
Initial Calibration, Static Calibration
Multiplexing of Rx inputs to share components in the pipeline
Multiplexing the Tx outputs
Adjustable Calibration Capacitor
Adjustable Impedance Sensor Support Line
Special blocks list
Brown out circuit (Power on Reset)
Temperature monitoring (OTEMP)
Current monitoring
ESD metastability and lock-up detection “alive monitor pin”
Latchup detection “alive monitor pin” & OTEMP
RCOSC
Watchdog, RTOS, General purpose, wake-up timers
Multiple ASIC support (for larger sensors)

- master/slaves—VULCAN type
- inter-processor communication (multi cores in one ASIC)
- inter-processor communication (multi chips on one PCB)
- inter-processor communication (multi chips across PCBs)

Power Management (sleep, standby, active, etc . . . )
New items (will be added to Lotus specification)
10 or 12 bits A/D
Automatic averaging for noise reduction (super sampling)
Independent gains & offsets per pixel (out of n possibilities)
Decoupled gain & offset control
Redefined RX pipeline architecture
Pure multiplexing of I/O? (reduced circuitry per I/O)
Reconfiguring I/Os (TX versus RX)
Pattern recognition accelerator (matching)
Matcher algorithm accelerator
FFT accelerator
Compression/decimation
NAV correlation engine
de-ghosting HW
Automatic thermal compensation
Sensor compensation
Temperature detection
Fingerprint sensor operation improvements
59 Multifrequency Impediography. Use of 2 frequencies, fs and fp (serial and parallel resonance of the pillar) increases the dynamic range substantially (e.g. it squares the dynamic range between ridge and valley). This two frequency method is expanded into even higher sensitivities if more measurements at several frequencies between fs and fp as well as above fp and below fs are utilized predicting the load.
60 Wavelet impediography. The frequency dependent electrical impedance around the pillars resonance frequency has typical shape, which can be described as a wavelet. If a dampening load is applied to the pillar the wavelet will change its shape. Using mathematical relation of wavelet analysis will greatly enhance the dynamic range of acoustic impediography and hence fingerprinting
61 Coded excitation will help detecting current change at an element measured in case the signal level is corrupted by acoustic noise resulting from crosstalk and wave propagation. The coding is detected by cross correlation
There are multiple patterns available for being employed for correlation which must be evaluated separately. But those will follow the same regime and are hereby claimed.
62 Frequency shift method. A smaller or larger shift to the lower frequency of fs is observed when pillars are dampened by outer loads. This shift is detectable and can be used alone or in combination with the current response for increased SNR and dynamic range of acoustic impediography.
63 Improving mechanical Q
Mechanical Q is substantially improved and hence dynamic range and sensitivity of the impediography method if mechanical crosstalk between elements is reduced. This can be performed in the following ways:
a. via material properties and lamb wave propagation
b. by means of anisotropic interstitional material
64 Touch sensor backing
a) random bonds
b) surface roughness
c) structural nonlinearity
d) low acoustic impedance (0.5 MRayl) material (e.g. airgel, hollow glass spheres composites)
65 Pressure related transmission into the backing location where ridges touch the sensor transmission into backing is increased=>improves damping, higher contrast
66. Top sensor matching layer=>improves contrast
67 Vital parameter extraction from the finger tip: blood flow, bone structure, tissue speckle, tissue elasticity (tissue pressure estimator), heart rate from blood flow
68 Various scanning schemes for producing pulse-echo image information and flow estimates including tissue strain.
Concepts: Ultrasound finger measurements (bone & vein structure, pulse rate, etc . . . )
Proof of Life. Scan multiple fingers at the same time with multiple sensors/ASICs.
Harvest electrical energy using the piezoelectric properties of the sensor.
69. Detecting finger tip temperature via change of resonance frequency
70. Avoiding unwanted wave propagation across the fingerprint sensor.
During operation several transmit lines will be used to speed up data acquisition. If the location of the lines are chosen in a way that emitted waves from the transmit lines propagating across the sensor do not interfere positively on locations currently measured interference noise is minimized increasing SNR. This condition is realized if the distance from locations currently measured to the drive lines are not multiple of the wavelength of the travelling waves i.e. surface waves, shear and bending waves.
Current 1-3 composite of falcon geometry pitch 72 um, width 50 um and pillar height 150 um is approx 50 percent as measured with laser vibrometry and predicted by FEM modeling. Crosstalk is reduced, if the interstitional material exhibits a large difference (preferably a lower) to the pzt, e.g. air. However air will not keep the pillar in place. Currently Epotek 301-2 is deployed providing sufficient bonding strength to keep the pillars in place during grinding the process step exerting the largest force to the pillar during manufacturing. However, material with much lower acoustic impedance could be employed as for example epoxy fill with hollow glass spheres having a diameter of <1 um.
Another possibility are nano porous polymers currently under development, but with no known source of commercial production.
Problem. Air backing is of advantage for ultrasound transducers as it increases the output amplitude by 30% according to the Redwood Transient Model. For the fingerprint sensor air backing is vital, as energy shall be transmitted in the front medium only. In both cases the sensors front propagation material is soft tissue a suitable backing must have much lower acoustic impedance approximately 0.1 MRayl as estimated from earlier calculations.² ²Hard backing would be a solution too. However the hardest material, pure tungsten, has an ac. Impedance of 100 MRay leaving us with reflection coefficient of ˜0.74.
Particularly for the fingerprint touch sensor the backing is required for stability.
Proposed solution. the surface roughness of most material provides an interface to the fingerprint sensor, which is only partial in contact with the active sensor. Typically no acoustic contact is achieved without high static pressure. The reduced contact area of a rough surface is equivalent to an air like backing and can support the sensor.
Backing is provided by a layer sprinkled randomly with bumps having diameter less than a pillars width. These bumps provide the support for the sensor. Due to their round shape and small total area the transmission into the backing is kept low. The average distance between bumps will be chosen according the bending strength of the 1-3 piezo composite. For fingerprinting each bump may create a pillar failing reflecting the front loads. However, if the fingerprint is over sampled, filtering out those locations will not degrade the final result of the fingerprint matching schemes. The random scheme is used to destroy phase coherence for any transmission and wave propagation in the backing
A prototype assembly manufacturing plan should be prepared before a full manufacturing stage. Basically I believe that major equipment investment can be done after one secure the certain amount of POs from customers. Meantime, having the prototyping capability to meet marketing needs is needed with minimum amount of investment.
Again, it is preferred that the test-bonding the 3050 sensor and bezel using the
MicroPack's 130 Dual Head US bonder be used, whether the US bonding can be successfully done on the 3050 sensor plus bezel prototype assembly.
Sensor FEM Model evaluating sensor performance properties for fingerprinting using impediography: The model is parametric, i.e. all geometries can be varied accommodating different pitches and in turn sensor resolution.

CONCLUSION

It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.

Claims

1. A method of making an integrated circuit (IC) device using copper metallization on 1-3 PZT composite, comprising:

providing an overlay of electroplated immersion gold (Au) to cover copper metal traces, the providing preventing oxidation on the 1:3 PZT composite with material; and

forming an immersion of Au nickel electrodes on the 1-3 PZT composite to provide pad metallization for external connections of the IC.