U.S. patent application number 09/373083 was filed with the patent office on 2002-05-23 for segment connections for multiple elevation transducers.
Invention is credited to GURRIE, FRANCIS E., SUDOL, WOJTEK.
Application Number | 20020060508 09/373083 |
Document ID | / |
Family ID | 25467585 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020060508 |
Kind Code |
A1 |
SUDOL, WOJTEK ; et
al. |
May 23, 2002 |
SEGMENT CONNECTIONS FOR MULTIPLE ELEVATION TRANSDUCERS
Abstract
A connection assembly for use in a multiple aperture ultrasonic
transducer including an array of elements for transmitting and
receiving wherein each element includes a plurality of segments and
the connection assembly interconnects the segments of the elements
and the segments to transmit/receive circuits to form the apertures
of the array. The connection assembly includes an isolating layer
superimposed on the segments with at least one via opening located
within the area of each segment and a conductive layer superimposed
on the isolating layer with conductive paths interconnecting the
segments and the segments to the transmit/receive circuits to form
the apertures of the array. The conductive layer forms a continuous
layer covering the isolating layer, the interior surfaces of the
via openings and the areas of the segments exposed through the via
openings and is scribed to divide the conductive layer into the
conductive paths. The conductive paths associated with each element
are separated from the conductive paths associated with neighboring
elements by the dicing cuts that divide the elements and segments
from one another. A flex circuit is assembled coplanar with the
segments and the isolating and conductive layers are superimposed
on the elements and flex circuit so that the connections between
the segments and flex leads are accomplished by the same
processes.
Inventors: |
SUDOL, WOJTEK; (BURLINGTON,
MA) ; GURRIE, FRANCIS E.; (NORTH ANDOVER,
MA) |
Correspondence
Address: |
PHILIPS ELECTRONICS NORTH AMERICAN
580 WHITE PLAINS ROAD
TARRYTOWN
NY
10591
US
|
Family ID: |
25467585 |
Appl. No.: |
09/373083 |
Filed: |
August 12, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09373083 |
Aug 12, 1999 |
|
|
|
08935744 |
Sep 23, 1997 |
|
|
|
Current U.S.
Class: |
310/334 ;
29/25.35; 29/852; 310/331 |
Current CPC
Class: |
Y10T 29/49126 20150115;
Y10T 29/42 20150115; B06B 1/0629 20130101; Y10T 29/49165
20150115 |
Class at
Publication: |
310/334 ;
310/331; 29/25.35; 29/852 |
International
Class: |
H02N 002/00; H01L
041/04; H01K 003/10 |
Claims
What is claimed is:
1. A multiple aperture ultrasonic transducer including an array of
elements for transmitting or receiving signals, wherein each
element is comprised of a plurality of segments, and a connection
assembly for interconnecting the segments of each element and for
connecting the segments to transmit/receive circuits to form the
apertures of the array, the connection assembly comprising: an
isolating layer superimposed on the segments of the array, the
isolating layer having at least one via opening corresponding to
and located within the area of each segment of the array, each via
opening exposing a corresponding area of the corresponding segment,
and a conductive layer superimposed on the isolating layer and
having conductive paths interconnecting the segments and connecting
the segments to the transmit/receive circuits to form the apertures
of the array.
2. The connection assembly of claim 1, wherein: the conductive
layer is superimposed on and continuously covers the isolating
layer, the interior surfaces of the via openings and the areas of
the segments exposed through the via openings, and is scribed to
divide the conductive layer into the conductive paths
interconnecting the segments and connecting the segments to the
transmit/receive circuits to form the apertures of the array.
3. The connection assembly of claim 1 wherein the conductive paths
associated with the segments of each element are separated from the
conductive paths associated with the segments of each adjacent
element by a dicing cut that separates the portion of the isolating
layer and the conductive layer superimposed on the segments of each
element from the portion of the isolating layer and the conductive
layer superimposed on the segments of each adjacent element.
4. The connection assembly of claim 1 wherein the conductive layer
is a deposited conductive layer.
5. The connection assembly of claim 4 wherein the conductive layer
is deposited by a sputtering process.
6. The connection assembly of claim 1 wherein the isolating layer
and the conductive layer are superimposed upon a flex circuit
coplanar with the segments and with via openings through the
isolating layer in the area of the flex circuit and wherein the
conductive layer is scribed to provide connections between the
segments and flex leads formed on the flex circuit.
7. A method for constructing a connection assembly for use in a
multiple aperture ultrasonic transducer including an array of
elements for transmitting or receiving signals, wherein each
element is comprised of a plurality of segments, and the connection
assembly for interconnecting the segments of each element and for
connecting the segments to transmit/receive circuits to form the
apertures of the array, comprising the steps of: superimposing an
isolating layer on the segments of the array, forming a plurality
of via openings through the isolating layer, the isolating layer
having at least one via opening therethrough for and located within
the area of each segment of the array and each via opening exposing
a corresponding area of a segment, superimposing a conductive layer
on the isolating layer, the conductive layer having conductive
paths interconnecting the segments and connecting the segments to
the transmit/receive circuits to form the apertures of the
array.
8. The method of claim 7 for constructing a transducer connection
assembly wherein the step of superimposing a conductive layer on
the isolating layer to provide conductive paths further comprises
the steps of: superimposing a continuous conductive layer on the
isolating layer, the conductive layer covering the interior
surfaces of the via openings and the areas of the segments exposed
through the via openings in a continuous layer, and scribing the
conductive layer to divide the conductive layer into conductive
paths interconnecting the segments and connecting the segments to
the transmit/receive circuits to form the apertures of the
array.
9. The method of claim 7 for constructing a transducer connection
assembly, further comprising the steps of: for each element,
separating the conductive paths of the element from the conductive
paths of an adjacent element by performing a dicing cut separating
the segments of the element from the segments of the adjacent
element, the dicing cut dividing the portion of the isolating layer
and the conductive layer superimposed on the segments of the
element from the portion of the isolating layer and the conductive
layer superimposed on the segments of the adjacent element.
10. The method of claim 7 wherein the conductive layer is a
deposited conductive layer.
11. The method of claim 10 wherein the conductive layer is
deposited by a sputtering process.
12. The method of claim 7, further comprising the steps of:
assembling a flex circuit having flex leads to be coplanar with the
segments of the array, superimposing and scribing the isolating
layer and the conductive layer upon the flex circuit in the same
steps as the superimposing and scribing of the isolating layer and
conductive layer and with via openings through the isolating layer
in areas of the flex leads whereby the conductive layer is scribed
to provide connections between the segments and flex leads formed
on the flex circuit.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a design and the method of
constructing ultrasonic transducers and, in particular, a design
and method for interconnecting elements in multiple elevation
transducers.
BACKGROUND OF THE INVENTION
[0002] Ultrasonic transducers are used in many medical applications
and, in particular, for the non-invasive acquisition of images of
organs and conditions within a patient, typical examples being the
ultrasound imaging of fetuses and the heart. The ultrasonic
transducers used in such applications are generally hand held, and
must meet stringent dimensional constraints in order to acquire the
desired images. For example, it is frequently necessary that the
transducer be able to obtain high resolution images of significant
portions of a patient's chest cavity through the gap between two
ribs when used for cardiac diagnostic purposes, thereby severely
limiting the physical dimensions of the transducer.
[0003] As a consequence, and because of the relatively small
aperture between human ribs and similar constraints upon transducer
positioning when attempting to gain images of other parts of the
human body, there has been significant development of linear or
phased array transducers comprising multiple transmitting and
receiving elements, with the associated electronics and switching
circuits, to provide relatively narrowly focused and "steerable"
transmitting and receiving "beams". The most common of such
transducers comprises a one element wide by multiple element long
linear array of transmitting and receiving elements arranged in
line along a flat plane or, preferably, along a concave or convex
arc, thereby providing a greater scanning arc.
[0004] The transmitting and receiving beams of such transducers are
formed and steered by selecting individual transducers elements or
groups of transducer elements to transmit or receive ultrasonic
energy, wherein each such individual transducer element or group of
transducers elements forms an "aperture" of the transducer array.
Such an array is thereby formed of a single row of apertures
extending along the face of the array and such transducers are
consequently referred to as "single aperture" transducers.
[0005] While such azimuth scanning single aperture arrays are
advantageous for many applications, single aperture transducers
have the disadvantage that they can scan only along the single
plane of the transducer elements. As a consequence, there have been
many attempts to construct transducers that are also capable of
steering or focusing in elevation as well as azimuth, that is,
along the axis at right angles to the azimuth plane along which the
elements are arrayed as well as along the azimuth plane.
[0006] As is well understood, the formation and steering and/or
focusing of the transmitting and receiving beams of a transducer
are controlled by selection and use of the various separate
physical divisions or areas of transducer material comprising the
transducer array, which, as described above, are referred to as
"apertures". In contrast to "single aperture" transducers, however,
in which each aperture is formed by an element or group of elements
extending across the face of the array as a single unitary area or
division or the array, each corresponding element in a transducer
capable of scanning in elevation is divided into multiple
sub-elements, or segments. For this reason, and because each
element position along such an array can form multiple apertures,
that is, using different combinations of the sub-elements or
segments of each of the transducer elements, such transducers are
consequently referred to as "multiple aperture" transducers.
[0007] The shape, focus and direction of the transmitting and
receiving beams of a multiple aperture transducer are again
controlled by selection of the apertures of the array. In a
multiple aperture array, however, each aperture is formed by one or
more of the sub-elements, or segments, of the transducer elements,
so that the apertures of a multiple aperture array can be used to
steer and focus the transducer scan beam along the elevation axis
as well as along the azimuth axis and can define multiple azimuthal
scan planes, each being at a different angle of elevation.
[0008] It should be noted that in both single aperture transducers
and in multiple aperture transducers the apertures may be either
driven actively, or simply deactivated to reduce the size of the
acoustic aperture, thereby controlling the shape, direction and
focus of the transmitting and receiving beams formed by the
transducer array.
[0009] The transducer elements of both single aperture and multiple
aperture transducers are generally made of a piezoelectric material
and the array of elements or sub-elements is generally mounted onto
a body made of a backing material. Connections between the
individual transducer elements and the associated electronics and
switching elements are usually provided through various
arrangements and combinations of thick and thin film circuits,
flexible printed circuits and wires, which are generally located on
the back of the array, between the array and the body, with leads
running along the body to the transducer electronics. One or more
layers of impedance matching material, generally considered to be a
part of the elements themselves, is often superimposed upon the
transducer elements to match the acoustic impedance of the
transducer to the body or material being scanned, and a lens
comprised of a suitable material may be additionally superimposed
upon the impedance matching material to shape or focus the beams
generated by the transducer elements. In some implementations, the
impedance matching layers may have suitable acoustic
characteristics and may be shaped to operate as an acoustic
lens.
[0010] Single aperture transducers are generally constructed from a
single piece of transducer material having a width equal to the
length of one element and a length equal to the widths of the total
number of elements plus spaces between the elements. One or more
thin or thick film circuits or flexible printed circuits having
connections and paths for the individual elements, or the like
implemented in any of several other ways, are bonded to one side of
the piece of transducer material and a layer or layers of matching
material may be bonded to the radiating and receiving side of the
transducer material to form a "stack" of the transducer material,
circuits and matching layers. A temporary or permanent layer of
backing material of some form, such as a flexible material, may
also be bonded to the back of the stack to aid in handling the
stack during manufacture.
[0011] Successive cuts are then made across the width of the
transducer stack on the radiating/receiving side of the stack and
at intervals corresponding to the widths of the elements and the
spacing between the elements to divide the single piece of material
into the individual elements. This operation is generally referred
to as "dicing" and is usually done with a device referred to as a
dicing saw, but may be done with other techniques, such as lasers.
These cuts may extend only through the transducer and matching
material layers, or partly or completely through the circuit layer,
or through the circuit layer and at least a part of any backing
layers, depending upon the detailed design and implementation of
the circuit layers.
[0012] The assembly of individual transducer elements with the
circuit and matching layers are then bonded to the backing body,
which may have a flat, concave or convex face, as described above,
with any temporary backing layers being removed as necessary. It
should be noted that in certain instances the dicing may be done
after the assembly of transducer elements, matching materials, and
circuits is bonded to the backing material and that the dicing cuts
may extend into the layers of backing material or even into the
backing body.
[0013] Connections between the thin or thick film circuits
connecting to the transducer elements and wires or printed
circuits, such as flexible circuits, which in turn connect to the
electronics and switching elements may made before or after the
transducer assembly is bonded to the backing body, again depending
on the detailed design and implementation of these connections.
[0014] While methods for the construction of multiple aperture
transducer are well known, and similar to those used in
construction of single aperture arrays, multiple aperture arrays
present greater difficulties than do single aperture arrays. For
example, a particular application may require that each element be
comprised of three segments, or apertures, that is, two outer
segments and a middle segment. This may be achieved, for example,
by constructing the transducer elements from three elongated pieces
of transducer material, that is, two outer pieces and a middle
piece, and then dicing the pieces across the face of the array as
was described with regard to single aperture arrays, or by
additional cuts along the transducer stack in the longitudinal
direction to divide the two outer segments from the middle
segment.
[0015] A primary problem in constructing transducers, however, is
in achieving the electrical connections to the elements and
sub-elements, or segments, as the number of elements or sub-element
segments increases. That is, the physical dimensions of an array,
especially for medical use, is generally constrained, for example,
by the need to scan the cardiac structures through the space
between patient's ribs to avoid interference by the ribs. At the
same time, there is a need and trend to increase the number of
elements or sub-elements to achieve every finer scan resolution to
achieve increasingly detailed images of the cardiac structures.
[0016] While this problem exists even with single aperture
transducers, the problem is particularly severe with multiple
aperture transducers because the number of electrical connections
to each element, each of which may be comprised of three or more
segments, or sub-elements, is greatly increased while the space in
which to make the connections does not increase. For example, in a
single aperture array each element is made of a single segment
while in a three aperture array each element is divided into three
segments. As a result, while each element of a single aperture
array requires a single connection to the single segment that
comprises the element, a three aperture array requires, for each
element, two separate connections to the two outer segments and a
third connection to the middle segment, thereby tripling the number
of connections per element, and possibly requiring additional
connections to each possible pair of segments. In addition, each
middle segment is bounded on both ends by the outer segments of the
element and on either side by the two adjacent elements, so that
the middle segments are not readily accessible for connections. It
is therefore apparent that the space available to make connections
to the segments of a multiple aperture array and to run the leads
from the segments to the points of connection to the transducer
electronics is extremely constrained and that the problem compounds
very rapidly as the number of elements in the transducer or the
number of segments in each element increases.
[0017] Considering a specific example, the Hewlett-Packard Model
21215 transducer provides two sizes of elevation apertures and is
constructed generally as described above, that is, of a linear
array of separate or separated elements wherein each element is
comprised of three separate segments, two outer segments and a
middle segment. In this design, the elements are arranged in a
straight plane, rather than a concave or convex arc, and the middle
segment of each element is connected to a transmit/receive circuit
while the two outer segments of the element are connected together
and then to a second transmit/receive circuit or through a switch
to the same transmit/receive circuit as the middle segment.
[0018] Connections to the segments are made through flex circuits,
that is, circuits etched onto thin, flexible circuit boards,
wherein an individual flex circuit is used for each set of
elevation segment connections and wherein each flex circuit
contains all of the connections for the corresponding segments of
each of the elements along the array. The transducer therefore
requires three flex circuits, one for each out row of segments and
one for the middle row of segments. The two flex circuits
connecting to the outer segments of each element of the outer
segments and are then connected by a flex circuit having jumper
connections, or by a circuit board. The third flex circuit connects
to the middle segments of the elements, and thus must make
connection at the middle of the back side of the piezoelectric
array.
[0019] It is therefore apparent that a three aperture array like
the Hewlett-Packard Model 21215 requires three times as many
connections to the piezoelectric segments themselves and twice as
many flex circuits as in a single aperture array, and two
additional flex circuit to flex circuit connections through flex
jumper connections or through a printed circuit board for each
element. These connections result in higher cost and lower
manufacturing yield. In addition, assembly is more complex in that
the flex circuit to the middle segments must be carefully aligned
with the flex circuits to the outer segments. This factor alone
makes it difficult, if not impossible, to manufacture a curved
array and the presence of the middle segment flex circuit requires
the use of either a poured backing body material or complex molding
or machining to manufacture the backing body.
[0020] To further compound the problem of achieving a large number
of connections and leads to the transducer elements and segments in
a small area, the connections to the segments must be made in such
a manner as not to interfere with the acoustic characteristics of
the transducer. That is, it has been described above that the
connections to the transducer elements and segments are generally
made through thin or thick film circuits or flex circuits bonded to
the back side of the transducer elements. The number of leads and
connections, however, generally results in a connection and lead
layer or layers having significant thickness and effect, in terms
of the acoustic characteristics of the array, thereby distorting or
interfering with the acoustic characteristics of the array. In
addition, the lead and connection layer or layers and other layers
interposed between, such as insulating layers, do not provide
smooth surfaces, or planes, because of the raised or depressed
areas of the layers forming the leads and connections. As such, it
is difficult to reliably bond the layers together without
significant additional layers of bonding materials and the
unevenness of the surfaces tend to trap bonding material and air
between the layers, thereby providing an acoustically
non-homogenous "body" bonded to the "back" face of the transducer
elements that further interferes with the acoustic characteristics
of the transducer array.
[0021] The methods used in the prior art to construct multiple
aperture arrays include the use of multiple flex circuits, as
described just above, connections embedded in the backing body, the
use very thin film or deposited circuits to form the connections
and leads to the transducer elements and segments, and even the use
of electrostrictive rather than piezoelectric materials for the
transducer elements.
[0022] Each of these methods, however, provides its own
difficulties and problems. For example, the disadvantages of
multiple flex circuits have been discussed above, and the
disadvantages of connections embedded in the backing body are
comparable.
[0023] An alternative is the use of a multi-layer thick film
ceramic hybrid circuit which also serves as the backing body. The
laminated layers with embedded connection circuits results in leads
which run vertically, that is, perpendicularly, between the
segments and an interface circuit to which the connections are
made, but also results in leads with very small cross sections that
are attached at both ends by butt joints, which lack reliability.
The use of a multi-layer thick film circuit, in turn, can provide
much stronger and more reliable connections, but the acoustic
characteristics of the ceramic material may degrade the acoustic
performance of the transducer. Both approaches, moreover, may have
the disadvantage of requiring multiple steps to make the
connections to the piezoelectric elements and may result in added
cost from not using standard printed or hybrid circuit
manufacturing techniques.
[0024] Yet other approaches use thin film or very thin film
circuits for the connections and leads, thereby providing
connection and lead layers that are acoustically thin and thereby
cause less interference with the acoustic characteristics of the
transducer. Thin film circuits, however, are difficult to work with
in manufacture, often being relatively fragile, and generally
require "wet" manufacturing processes that result in potentially
undesirable materials to be disposed of.
[0025] In addition, thin film circuits, like thick film circuits
and flexible circuits, require connections between layers, for
example, between the layer forming contacts to the elements and
segments and the layer providing the interconnecting leads, and
these interlayer connections, commonly called "vias" are difficult
to form in the thicknesses typical of thin film circuits. Certain
of the prior art approaches to thin film circuits, for example,
while recognizing the advantages of thin film circuits for the
actual contacts to the transducer elements and segments and for the
interconnecting leads, have required the use of additional,
vertically oriented circuit boards or very thin, free standing
wires to accomplish the necessary connections.
[0026] The present invention provides a solution to these and other
problems of the prior art.
SUMMARY OF THE INVENTION
[0027] The present invention is directed to a connection assembly
for use in a multiple aperture ultrasonic transducer including an
array of elements for transmitting or receiving signals that is
capable of steering and/or focusing in elevation as well as azimuth
and wherein each element is comprised of a plurality of segments
and wherein the connection assembly interconnects the segments of
each element and connects the segments to transmit/receive circuits
to form the apertures of the array, and to a method for
constructing such a connection assembly.
[0028] According to the present invention, the connection assembly
includes an isolating layer and a conductive layer. The isolating
layer is superimposed on the segments of the array and has at least
one via opening corresponding to and located within the area of
each segment of the array. Each via opening exposes a corresponding
area of a segment. The conductive layer is superimposed on the
isolating layer and has conductive paths interconnecting the
segments and connecting the segments to the transmit/receive
circuits to form the apertures of the array.
[0029] In a presently preferred embodiment, the conductive layer
forms a continuous layer covering the isolating layer, the interior
surfaces of the via openings and the areas of the segments exposed
through the via openings and is scribed to divide the conductive
layer into conductive paths interconnecting the segments and
connecting the segments to the transmit/receive circuits to form
the apertures of the array.
[0030] Further according to the present invention, the conductive
paths associated with each element are separated from the
conductive paths associated with neighboring elements by dicing
cuts that divide the portion of the isolating layer and the
conductive layer superimposed on the element from the portions of
the isolating layer and the conductive layer superimposed on the
neighboring elements.
[0031] Further according to the present invention, the conductive
layer is a deposited conductive layer, and is deposited by a
sputtering process.
[0032] In a further aspect of the present invention, the
connections between the segments and flex leads connecting to the
circuitry driving the segments are accomplished at the same time
and in the same processes as the connection to and between the
segments, rather than in a separate process. According to the
present invention, a flex circuit having flex leads is assembled to
be coplanar with the segments of the array at the time the
isolating and conductive layers are superimposed on the elements of
the array, so that the isolating layer and the conductive layer are
superimposed upon the flex circuit and scribed in the same steps as
the superimposing and scribing of the isolating layer and
conductive layer on the elements, with via openings provided
through the isolating layer in areas of the flex leads to provide
connections between the conductive layer and the flex leads. The
conductive layer in the area of the flex leads is then scribed to
provide connections between the segments and flex leads formed on
the flex circuit, and diced to separate the connections to
individual segments in the same step in which the elements are
diced into segments.
[0033] Other features, objects and advantages of the present
invention will be understood by those of ordinary skill in the art
after reading the following descriptions of a present
implementation of the present invention, and after examining the
drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1A is an illustration of the segments and connections
of a typical two aperture transducer;
[0035] FIG. 1B is an illustration of the segments and connections
of a typical four aperture transducer;
[0036] FIG. 2 is a cross sectional representation of a typical two
aperture transducer;
[0037] FIGS. 3A, 3B and 3C are representations of the electrode
layer, insulating layer and connector layer or a typical three
aperture transducer;
[0038] FIG. 4 is a cross sectional illustration of a typical
via;
[0039] FIG. 5A is a cross sectional illustration of a connection
assembly of the present invention;
[0040] FIGS. 5B is a diagrammatic cross section view of the
connection assembly of the present invention illustrating the
manufacture of the connection of flex leads to the segments of a
transducer;
[0041] FIG. 6 is a diagrammatic view of a connection assembly of
the present invention with scribing lines and dicing lines and
conductor paths; and,
[0042] FIGS. 7A, 7B, 7C and 7D are diagrammatic representations of
the elements, isolating layer, scribed conductive layer and
assembled connection assembly of the present invention.
DETAILED DESCRIPTION
[0043] The following will first describe the general construction
of multi-aperture transducers, and in particular a typical
construction of the circuitry layers bonded to the back, or
non-radiating and receiving side, of the transducer elements to
provide connections between the transducer element segments and the
transmit/receive circuitry associated with the transducer. The
present invention will then be described in detail, thereby clearly
illustrating the differences between the connection circuitry of
the present invention and the connection circuitry generally used
in transducers.
[0044] A. General Description of a Multi-aperture Transducer with
Multi-layer Backplane Interconnections (FIGS. 1A, 1B, 2 and 3A-3C
and 4)
[0045] Referring to FIG. 1A, therein is shown a diagrammatic
representation of a single piezoelectric Element 10 of an exemplary
two aperture Transducer 12 and, in outline form, two adjacent
Elements 10 of the array of Elements 10 comprising the
transmit/receive array of the transducer. As indicated therein, the
construction of the transducer as a two aperture transducer
requires that each piezoelectric Element 10 be divided into three
piezoelectric segments comprised of a single Middle Segment (MS) 14
and two Outer Segments (OSs) 16. As represented, Middle Segment
(MS) 14 is connected through a Circuit Lead 18 to a First
Transmit/Receive Circuit (TRC) 20 to form the transmit/receive
element of a first aperture and Outer Segments (OSs) 16 are
interconnected by an Interconnect Lead 22 to form a single unit to
together form the transmit/receive element of the second aperture,
and are thereafter connected through a Circuit Lead 24 to a Second
Transmit/Receive Circuit (TRC) 26. In alternate embodiments, Second
Transmit/Receive Circuit (TRC) 26 may be replaced by a switch which
selectively connects either Middle Segment (MS) 14 or the two Outer
Segments (OSs) 16 to the single First Transmit/Receive Circuit
(TRC) 20. It will be noted, as is well understood in the art, that
all Elements 10 of the transducer are constructed and
interconnected in the same manner as illustrated for the single
Element 10 in FIG. 1A and that the Elements 10 will each have a
connection to signal and power ground as indicated in FIG. 1A,
usually as a common connection shared by all Elements 10.
[0046] It will be recognized by those of ordinary skill in the arts
that the element construction and segment connections and
interconnections illustrated in FIG. 1A may be extended at will to
transducers having larger numbers of apertures. For example, FIG.
1B illustrates a piezoelectric Element 10 of a four aperture
transducer. In this transducer, Middle Segment (MS) 14 comprises
the transmitting/receiving element for a first aperture, first
Outer Segments (OSs) 16A are interconnected to form the
transmit/receive element of a second aperture, second Outer
Segments (OSs) 16B are interconnected to form the transmit/receive
element of a third aperture, and third Outer Segments (OSs) 16C are
interconnected to form the transmit/receive element of a fourth
aperture. This construction may be expanded indefinitely, adding
successive pairs of Outer Segments (OSs) 16 with the Middle Segment
(MS) 14 forming one aperture and each successive pair of Outer
Segments (OSs) 16 located symmetrically outwards from Middle
Segment (MS) 14 forming additional apertures. Again, Middle Segment
(MS) 14 and Outer Segments (OSs) 16 will further have a connection
to ground.
[0047] As represented in the cross section of Transducer 12
illustrated in FIG. 2, the segment interconnections and connections
of the exemplary transducer shown therein are typically formed in a
multi-layered Connection Assembly 28 that is comprised of an
Electrode Layer 30, an Insulating Layer 32 and a Connector Layer 34
wherein Electrode Layer 30 and Connector Layer 34 may typically be
formed of thick or thin film circuits or of flexible circuits. It
will be recognized by those of skill in the arts that, although
Insulating Layer 32 and Connector Layer 34 are represented in FIG.
2 as single layers for simplicity and clarity of representation and
discussion, Insulating Layer 32 and Connector Layer 34 may each or
both be comprised of multiple layers and that the layers of
Insulating Layer 32 and Connector Layer 34 may be interleaved as
necessary to isolate Connection Layers 34 from one another and from
Electrode Layer 30.
[0048] Electrode Layer 30 is a conductive layer typically comprised
of gold with underlying layers of one or more other metals to
promote adhesion and defines the electrode areas for the apertures,
that is, the connections to the piezoelectric Segments 16 and 14 to
form the transmit/receive elements of Transducer 12. Insulating
Layer 32, in turn, may typically be comprised of such materials as
polymide, silica, and a variety of other oxides, nitrides and
polymers and insulates Electrode Layer 30 from Connector Layer 34.
Connector Layer 34, in turn, is typically comprised of another
layer of conductive metal or metals similar to Electrode Layer 30
and provides the necessary conductive paths between the electrodes
of Electrode Layer 30 to selectively interconnect the piezoelectric
segments to form the transmit/receive elements of the apertures,
such as between two Outer Segments (OSs) 14A, and between the
Middle Segment-MS) 12 and Outer Segments (OSs) 14. Connector Layer
34 also provides the conductive paths necessary to connected the
piezoelectric segments of each of the apertures to the Flex
Circuits 56b connecting to the Transmit/Receive Circuit (TRC)s 20,
26. Connection Assembly 28 typically has a total acoustic thickness
of approximately 5 to 10 microns, and thereby does not adversely
affect the acoustic characteristics of the transducer assembly. As
will be described further below, the electrode areas of Electrode
Layer 30 are selectively connected to the connection paths of
Connector Layer 34 through conductive paths, referred to as "vias"
running between Electrode Layer 30 and Connector Layer 34 through
Insulating Layer 32.
[0049] Lastly, it will be noted that, as described above, Middle
Segment (MS) 14 and Outer Segments (OSs) 16 will have connections
to ground, often implemented as a common connection that is shared
by all Segments 14,16 and that is connected to the faces of
Segments 14,16 opposite the faces connecting to Electrode Layer 30.
A common method for implementing this ground connection is through
a ground plane that may be implemented, for example, as a layer on
the faces of Segments 14,16 opposite Connection Assembly 28 with
the ground layer extending to the edges of Elements 10 for
connection to ground. It will be noted that these ground
connections are not explicitly illustrated or shown in the
following descriptions or the figures referred to therein, for
purposes of clarity of presentation and discussion, but are present
and, as well understood by those of ordinary skill in the relevant
arts, may be implemented using the methods just discussed and other
analogous methods.
[0050] The construction of a Connection Assembly 28 with the three
layers thereof is further illustrated in FIGS. 3A through 3C with
the Electrode Layer 30, Insulating Layer 32 and Connector Layer 34
of the Connection Assembly 28 viewed from the "bottom" or "back"
side, that is, as viewed from the side of the piezoelectric
transducer elements to which the Connection Assembly 28 is bonded.
FIGS. 3A through 3C illustrate a three aperture Transducer 12
having five segments, the exemplary transducer shown in FIGS. 3A
through 3C having been expanded from the two aperture transducer of
FIG. 2 to more thoroughly illustrate the connections and conductive
paths of Electrode Layer 30, Insulating Layer 32 and Connector
Layer. It will be understood that the components of Construction
Assembly 28 as illustrated in FIGS. 3A through 3C and in the
following text illustrate the structure and construction of each
component thereof in the area of and under a single Element 10 of
the exemplary three aperture Transducer 12 and that this structure
and construction will be repeated as a single continuous structure
extending under each Element 10 of the Transducer 12 and for the
entire length of the array comprised of the Elements 10.
[0051] The segments of the three aperture Transducer 12 shown in
FIGS. 3A through 3C are designated as Segments 36A through 36E
wherein Segments 36A and 36E correspond generally to Outer Segments
16 of FIG. 1A and Segment 36C corresponds generally to Middle
Segment 14 while Segments 36B and 36D are located between Outer
Segments 16 and Middle Segment 14 and to either side of Middle
Segment 14. It will be understood that a first aperture is formed
by Segment 36C, a second aperture by Segments 36B and D and the
third aperture by Segments 36A and 16E. It will also thereby be
understood that the second aperture is formed by connecting
together Segments 36B and 36D into a first electrical unit and the
third aperture by connecting together Segments 36A and 36E into a
second electrical unit.
[0052] FIG. 3A illustrates the Electrode Layer 30 of the Connection
Assembly 28 and it is shown therein that Electrode Layer 30
includes conductive electrode area under and corresponding to each
of Segments 36A through 36E. These electrode areas are respectively
designated as Electrode Areas 38A through 38E and each electrically
connect or bond to the corresponding ones of Segments 36A through
36E, thereby establishing separate electrical connections to the
segments of the Element 10. Insulating Layer 32, in turn, is shown
in FIG. 3B and it will be seen therein that Insulating Layer 32
generally covers Electrode Areas 38A through 38E, thereby
insulating Electrode Areas 38A through 38E from the conductive
paths of Connector Layer 34.
[0053] As shown in FIG. 3C, Connector Layer 34, in turn, is
comprised of conductive Via Areas 40A through 40E, each of which
corresponds to one of Electrode Areas 38A through 38E, a first
Aperture Path 42A running from Via Area 40A, and thus from Segment
36A, to the edge of Element 10, a second Aperture Path 42B
connecting to Via Areas 40B and 40D, and thus to Segments 36B and
36D, and running to the edge of Element 10, and a third Aperture
Path 42C is connected to Via Area 40C and thus to Segments 36C and
runs to the edge of Element 10. Finally, a fourth Aperture Path 42D
is connecting to Via Area 40E and thus to Segment 36E and runs to
the edge of Element 10, with Aperture Paths 42A and 42D being
connected together through the flex wiring external to the
transducer to form the aperture comprised of Segments 36A and
38E.
[0054] Finally, each of Electrode Areas 38A through 38E is
connected to the corresponding one of Via Areas 40A through 40E,
thereby interconnecting Segments 36 into the three apertures and to
the flex leads to the transmit/receive electronics, by
corresponding Vias 44A through 44E wherein each Via 44 is a
conductive path running between Electrode Layer 30 and Connector
Layer 34.
[0055] As is well known in the art, and as is generically
illustrated in FIG. 4, a Via 44 formed in a three layer connection
assembly that includes an Electrode Layer 30, an Insulating Layer
32 and a Connector Layer 34 is generally constructed by drilling an
opening or Hole 46A between the two conductive layers of the
Connection Assembly 28, that is, between the Electrode Layer 30 and
the Connector Layer 34, wherein the Hole 46A forms a conductive
path between the two conductive layers by means of a layer of
Conductive Material 46B deposited on the inner surface of the Hole
46A by any of a variety of commonly employed techniques.
[0056] It will be appreciated by those of ordinary skill in the
relevant arts that the reliable manufacture of three layer
Connection Assemblies 28 comprised of an Electrode Layer 30, an
Insulating Layer 32 and a Connector Layer 34 with such vias can be
difficult. It will also be apparent to those of ordinary skill in
the relevant arts that the reliable manufacture of connection
assemblies with vias is significantly easier using the methods of
the present invention as described below.
[0057] B. Detailed Description of a Preferred Embodiment (FIGS. 5,
6 and 7)
[0058] Having described the general construction of a typical
Connection Assembly 28, the following will now describe a
Connection Assembly 28 according to the present invention.
[0059] Referring to FIG. 5A, therein is illustrated a side
sectional view of a Connection Assembly 48 of the present
invention. As illustrated therein, and according to the present
invention, all three layers of the Connection Assembly 28 described
above, that is, Electrode Layer 30, Insulating Layer 32 and
Connector Layer 34, are replaced with a single Isolating Layer 50
and a single Conductive Layer 54 wherein Isolating Layer 50 is
provided with Via Openings 52 therethrough in locations
corresponding, for example, to the Vias 44 illustrated in FIGS. 3A
through 3C. Conductive Layer 54 is deposited on the lower surface
of Isolating Layer 50, that is, on the side of Isolating Layer 50
opposite Segments 36 of the Elements 10, and completely covers the
lower surface of Isolating Layer 50, the inner surfaces of Via
Openings 54 and the portions of the lower surfaces of Segments 36
of Elements 10 that are exposed through Via Openings 54.
[0060] It may therefore be seen that the single Conductive Layer 54
thereby provides both the conductive paths formerly provided by
Connector Layer 34 and the connections between the conductive paths
and the Elements 10 formerly provided by the Vias 44 of the three
layer Connection Assembly 28 illustrated in FIGS. 1 through 4,
while the material of Elements 10 itself provided the connections
formerly provided by Electrode Layer 30. It may also be seen that
the single Isolating Layer 50 performs all of the functions
previously performed by Insulating Layer 32 of the three layer
Connection Assembly 28 illustrated in FIGS. 1 through 4.
[0061] As will be described further below, the area of Conductive
Layer 54 on the lower surface of Isolating Layer 50 is then
scribed, for example, by a scribing laser, to separate areas of the
area of Conductive Layer 54 on the lower surface of Isolating Layer
50 into conductive paths interconnecting the Segments 36 into
apertures.
[0062] In addition to replacing the Electrode Layer 30, Insulating
Layer 32 and Connector Layer 34 of the Connection Assembly 28
discussed above, the single Isolating Layer 50 and Conductive Layer
54 also provides the connections between the apertures, that is,
Segments 36, and Flex Leads 56 that were previously made through
extensions to the Connector Layer 34, referred to as "tab areas",
which were used to provide areas outside of the segments wherein
the Flex Leads 56 could be connected to the Connector Layer 34 in
the three layer Connection Assembly 28 comprised of an Electrode
Layer 30, Insulating Layer 50 and Conductive Layer 54.
[0063] According to the present invention, and as illustrated in
FIG. 5B, Flex Leads 56a are assembled so that the surface of the
Flex Circuit 56b having Flex Leads 56a is coplanar with the lower
surface of Elements 10. Isolating Layer 50 and Conductive Layer 54
are then deposited upon the Flex Circuit 56b having Flex Leads 56a
in the same process in which Isolating Layer 50 and Conductive
Layer 54 are deposited on Elements 10 and as continuous layers with
the areas of Isolating Layer 50 and Conductive Layer 54 residing on
Elements 10. The areas of Isolating Layer 50 and Conductive Layer
54 deposited on the Flex Circuit 56b, identified as Flex Connect
Areas 58. include Via Openings 52, in the manner described above,
for connecting Conductive Layer 54 to Flex Leads 56a. The Flex
Connect Areas 58 of Conductive Layer 54 are scribed in the same
process in which the portion of Conductive Layer 54 on the lower
surface of Elements 10 is scribed to form the conductive leads
between Segments 36 and Flex Leads 56a. As described further below,
the Flex Circuits 56b having Flex Leads 56a and the associated
areas of Isolating Layer 50 and Conductive Layer 54, including Flex
Connect Areas 58, are subsequently diced in the same process in
which Elements 10 are diced into Segments 36. Then, and as
illustrated in FIG. 5C, the Flex Circuits 56b having Flex Leads 56a
are bent "downwards" to connect to the circuitry driving Segments
36. As a consequence, the connections between Segments 36 and Flex
Leads 56a are accomplished at the same time and in the same
processes as the connections to and between Segments 36, thereby
further reducing the complexity and costs of manufacturing the
transducer.
[0064] According to the present invention, therefore, Isolating
Layer 50 performs the general functions performed by Insulating
Layer 32 as illustrated in FIGS. 2 and 3A through 3C, but
Conductive Layer 54 now performs all of the functions previously
performed by Electrode Areas 38, Vias 44, Via Areas 40, Aperture
Paths 42 and Tab Areas 58. In particular, it will be noted that the
"bottoms" of Via Openings 52 are, in fact, areas of the lower
surfaces of the Segments 36 of the Elements 10 so that the areas of
Conductive Layer 54 that are plated or deposited thereupon make
electrical contact and connection with Segments 36 and serve the
function previously served by Electrode Areas 38. Conductive Layer
54 further extends from the "bottoms" of Via Openings 52 and "up"
the inner surfaces of Via Openings 52 to continue on the lower
surface of Isolating Layer 50, thereby serving the function
previously served by Vias 44. Finally, and as described, the
conductive paths cut or etched into the area of Conductive Layer 54
on the lower surface of Isolating Layer 50 serve the functions
previously served by Via Areas 40 and Aperture Paths 42.
[0065] Referring now to FIG. 6, therein is illustrated a bottom
view of a section of an Isolating Layer 50 with Conductive Layer
54, that is, a view from the side having Conductive Layer 50, for a
three aperture transducer and showing four Elements 10 wherein each
Element 10 is comprised of five Segments 36. The view presented
therein is represented as if Isolating Layer 50 and Conductive
Layer 54 were transparent, so as to clearly illustrated the
relationships between the elements to be described in the
following. It will be understood, however, that Isolating Layer 50
and Conductive Layer 54 are to be understood to be present in FIG.
6.
[0066] Assembly of the transducer begins with the bonding of
Isolating Layer 50 to the lower surface of the block or blocks of
piezoelectric material that will form Elements 10 and Segments 36.
It will be understood that, at this time, there may be a separate
block of piezoelectric material for each row of Segments 36, or
that a single block of piezoelectric material may be cut
longitudinally into separate blocks corresponding to the rows of
Segments 36.
[0067] At this point in the process, Isolating layer 50 will be a
single, smooth, continuous sheet of dielectric or insulating
material, such as polymide, having a thickness in the range of
range of 0.5 microns to 20 microns and having a width and length
corresponding to the length and width of the Elements 10 of the
transducer with the areas for establishing connections to Flex
Leads 56a. In the present example, the transducer has 128 Elements
10, each being comprised of 5 segments, and a total length and
width of 12 mm (millimeter) by 0.17 mm; each Segment 36 is
approximately 2.4 mm by 0.17 mm and each Element 10 is separated
from the adjacent Elements 10 by 0.035 mm while the Segments 36 in
each Element 10 are separated by approximately 0.035 mm and the
areas for connection to Flex Leads 56a are approximately 0.050 mm
wide.
[0068] An opening will then be drilled through Isolating Layer 50,
for example, by use of a laser, at the location of each Via Opening
52, thereby forming Via Openings 52, wherein Via Openings 52 may
have a diameter in the range of 25 microns, approximately 0.001
inch, with the piezoelectric material of the Segments 36 exposed in
the bottoms of the Via Openings 52 serving in replacement of
Electrode Areas 38 of the three layer Connection Assembly 28
illustrated in FIGS. 1 through 4.
[0069] Conductive Layer 54 will then be deposited onto Isolating
Layer 50, and into Via Openings 53, preferably by a sputtering
technique. Conductive layer 54 may, for example, be comprised of
gold, will have a thickness in the range of 100 Angstroms to 20,000
Angstroms, and will generally cover the entire surface of Isolating
Layer 50, including the interior surfaces and bottoms of Via
Openings 52.
[0070] It will be appreciated from the above description of the
present invention that, at this time and before scribing, Conducive
Layer 54 will present an smooth, flat, continuous plane of
conductive material bonded to Isolating Layer 50, the only surface
feature being possible slight depressions at Via Openings 52.
[0071] The material of Conductive Layer 54 is then scribed or cut
away, again for example using a laser scribing tool, along Scribing
Lines 60 as illustrated in FIG. 6 to divide Conductive Layer 54
within the area of each Element 10, that is, within the area of the
Segments 36 of each Element 10, into conductive paths
interconnecting the Segments 36 of each Element 10 and connecting
the Segments 36 to Flex Leads 56a. In the present implementation of
the invention, the width of Scribing Lines 60 is in the range of 12
microns, that is, 0.0005 inch.
[0072] The piezoelectric material, Isolating Layer 50 and
Conductive Layer 54 are then sliced, or "diced", along the Dicing
Line 62 between each column of Segments 36 forming an Element 10,
that is, between Elements 10, to divide the piezoelectric material
into Elements 10 and, at the same time, separating the conductive
paths formed in Conductive Layer 54 for the Segments 36 of each
Element 10 from the conductive paths formed for the Segments 36 of
the adjacent Elements 10. It will be noted that Scribing Lines 60
and Via Openings 52 are set inwards from the edges of Segments 36,
that is, from Dicing Lines 62, by approximately 35 microns, that
is, 0.0014 inch, in the present implementation, to avoid
interference between Scribing Lines 60 and Via Openings 52 and the
dicing cuts.
[0073] A study of FIG. 6 will show that the conductive paths formed
by scribed and diced Conductive Layer 54 at this point forms the
connections described above to construct a three aperture
transducer array wherein each Element 10 is comprised of five
Segments 36. That is, and as described previously, in each Element
10 a first aperture is formed by Segment 36C, which has a
Conductive Layer 54 path to a connection to a Flex Lead 56a, a
second aperture is formed by Segments 36B and 36D, which are
connected together and to a Flex Lead 56a by another Conductive
Layer 54 path, and the third aperture is formed by Segments 36A and
16E, which are connected together and to a Flex Lead 56a by another
Conductive Layer 54 path.
[0074] Referring finally to FIGS. 7A, 7B, 7C and 7D, therein is
represented the Segments 36 with Isolating Layer 50 and Conductive
Layer 54 after cutting of Scribing Lines 60 and Dicing Lines 62 for
an 128 element, 3 aperture transducer. FIG. 7A shows the array of
Elements 10 comprised of Segments 36 while FIG. 7B shows Isolating
Layer 50 with Via Openings 52 and FIG. 7C shows Conductive Layer 54
with Scribing Lines 60. Finally, FIG. 7D shows the complete
assembly of Segments 36, Isolating Layer 50 and Conductive Layer 54
after Conductive Layer 54 has been scribed and the assembly has
been diced.
[0075] It therefore apparent from the above that Isolating Layer 50
and the scribed Conductive Layer 54 together comprise an
acoustically thin layer forming an essentially flat surface having
few or no acoustically significant voids or discontinuities. As a
result, the Connection Assembly 48 comprised of Isolating Layer 50
and the scribed Conductive Layer 54 does not interfere with or
degrade the acoustic characteristics of the transducer. In
addition, it is apparent that a Connection Assembly 48 comprised of
an Isolating Layer 50 and a scribed Conductive Layer 54 may be
constructed through significantly simpler processes than the
multiple layer connection assemblies of the prior art, and at
significantly decreased manufacturing costs. In addition, a
transducer utilizing the Connection Assembly 48 of the present
invention may be manufactured entirely with "dry" processes,
thereby eliminating or avoiding the use of "wet" processes and
potentially hazardous materials.
[0076] Lastly, while the invention has been particularly shown and
described with reference to preferred embodiments of the apparatus
and methods thereof, it will be also understood by those of
ordinary skill in the art that various changes, variations and
modifications in form, details and implementation may be made
therein, as has been discussed herein above, without departing from
the spirit and scope of the invention as defined by the appended
claims. For example, the number, proportions, dimensions,
arrangement and spacing of segments and elements in a transducer
may vary widely, as may the number and arrangement of the apertures
of the transducer, and the segments and elements need not be of
uniform dimensions. Likewise, the materials and dimensions of the
isolating and conductive layers and the vias and paths scribed into
the conductive layer may vary, and there may be multiple isolating
and conductive layers, depending, for example, on the connections
to be made to and between the segments. Further, the conductive
paths of each element may be separated from the conductive paths of
the other elements by scribing, instead of by the dicing cut. In
addition, the isolating layer as well as the conductive layer may
be deposited, and formed from materials suitable to the functions
of the layers, such as polymide, polyester, copper, gold, graphite,
and so on, or the isolating layer or the conductive layer, or both,
may be plated layers using "wet" processes, if necessary or, in
certain circumstances, desirable. Further, electrostrictive
materials may be used in place of piezoelectric materials, with
corresponding changes in the connections provided through the vias
and conductive layer. Therefore, it is the object of the appended
claims to cover all such variation and modifications of the
invention as come within the true spirit and scope of the
invention.
* * * * *