U.S. patent application number 09/750991 was filed with the patent office on 2002-07-04 for piezoelectric device having increased mechanical compliance.
Invention is credited to Vaughn, Gary.
Application Number | 20020084722 09/750991 |
Document ID | / |
Family ID | 25019989 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020084722 |
Kind Code |
A1 |
Vaughn, Gary |
July 4, 2002 |
Piezoelectric device having increased mechanical compliance
Abstract
The present invention provides a method of mounting a
piezoelectric device having a plurality of mounting pads directly
to a printed circuit board comprising the steps of providing a
piezoelectric device, miniature conductive springs and a printed
circuit board, attaching the springs to mounting pads of the
piezoelectric transformer, and attaching the springs to the printed
circuit board. Also disclosed is an apparatus made according to the
method.
Inventors: |
Vaughn, Gary; (Albuquerque,
NM) |
Correspondence
Address: |
CTS WIRELESS COMPONENTS/ CTS CORPORATION
PATENT LAW DEPARTMENT
171 COVINGTON DRIVE
BLOOMINGDALE
IL
60108
US
|
Family ID: |
25019989 |
Appl. No.: |
09/750991 |
Filed: |
December 28, 2000 |
Current U.S.
Class: |
310/348 ;
310/351 |
Current CPC
Class: |
H05K 3/325 20130101;
H01L 41/053 20130101 |
Class at
Publication: |
310/348 ;
310/351 |
International
Class: |
H01L 041/04 |
Claims
I claim:
1. A method of mounting a piezoelectric device having a plurality
of mounting pads directly to a printed circuit board, the method
comprising the steps of: providing a piezoelectric device,
miniature conductive springs and a printed circuit board; attaching
the springs to mounting pads of the piezoelectric transformer; and
attaching the springs to the printed circuit board.
2. The method of claim 1 wherein the springs are attached to the
piezoelectric device and the printed circuit board with solder.
3. The method of claim 1 wherein the springs are attached to the
piezoelectric device and the printed circuit board with a
conductive epoxy.
4. A method of mounting a piezoelectric device having a plurality
of mounting pads directly to a printed circuit board, the method
comprising the steps of: providing a piezoelectric device,
miniature conductive springs and a printed circuit board; attaching
the springs to the printed circuit board; and attaching the springs
to mounting pads of the piezoelectric transformer.
5. The method of claim 4 wherein the springs are attached to the
piezoelectric device and the printed circuit board with solder.
6. The method of claim 4 wherein the springs are attached to the
piezoelectric device and the printed circuit board with a
conductive epoxy.
7. A device capable of being attached to a printed circuit board
comprising: a piezoelectric device having a plurality of mounting
pads; and a plurality of miniature, conductive, coil springs having
one end attached to the piezoelectric device and the other end
attached to the printed circuit board.
8. The method of claim 7 wherein the springs are attached to the
piezoelectric device and the printed circuit board with solder.
9. The method of claim 7 wherein the springs are attached to the
piezoelectric device and the printed circuit board with a
conductive epoxy.
Description
TECHNICAL FIELD
[0001] The present invention relates to mounting piezoelectric
devices. More particularly the present invention relates to
mounting a piezoelectric transformer to a printed circuit board
with a coil spring in order to increase mechanical compliance.
BACKGROUND OF THE INVENTION
[0002] The miniaturization of circuits and components remains a top
priority in most electronic industries. The miniaturization of
solid-state components and combination-type circuitry chips, such
as central processor units, digital signal processors, memory,
etc., has been so successful that the packaging and electrical
connections for access to such small devices has become one of the
major roadblocks for further miniaturization. One of the packaging
problems for some types of miniaturization circuits, such as for
piezoelectric devices, is how to both support the piezoelectric
device and make electrical connections without adversely affecting
the operation and performance.
[0003] A piezoelectric transformer transfers energy through
acoustic vibration. At the resonance frequency of the piezoelectric
transformer a vibrational standing wave exists in the device which
defines nodes and anti-nodes of the standing wave. Efficient
piezoelectric transformers resonate with a very high mechanical Q.
Any mechanical dampening of the vibration of the piezoelectric
transformer reduces the Q and decreases the efficiency of the
transformer. Practical application of the piezoelectric transformer
normally requires that the device be attached to a printed circuit
board and that three or four electrical connections be made to the
printed circuit board. Therefore, it is necessary to mounting the
piezoelectric transformer in a manner that minimizes mechanical
stress on the piezoelectric transformer in order to maximize
efficiency.
[0004] Prior art mounting techniques often included the use of
silicon-type adhesives or double-sided tapes for mounting the
piezoelectric device to a printed circuit board. Such techniques
offer some stability against g-forces, rotational and torsional
forces, but dampen the vibrational force of the piezoelectric
transformer. In many instances these prior art mounting techniques
are unacceptable because the mechanical and electrical attachments
of the piezoelectric transformer to the printed circuit board
become fractured as a result of the fact that vibrational stresses
are concentrated at these portions. Additionally, these prior art
mounting methods reduce the efficiency of the piezoelectric
transformer by 3-5%.
[0005] The present invention solves the problem of the prior art by
providing controlled mechanical compliance in all directions. The
compliance may be adjusted by varying the spring height, material,
coil and wire diameter and coil spacing. Springs with approximately
the same coil diameter as the transformer pads can
[0006] Therefore, it would be advantageous to provide a simple and
inexpensive method for flexibly mounting a piezoelectric device on
a printed circuit board in order to minimize mechanical dampening
of the vibration of the piezoelectric device.
SUMMARY OF THE INVENTION
[0007] The present invention provides a method of mounting a
piezoelectric device having a plurality of mounting pads directly
to a printed circuit board comprising the steps of providing a
piezoelectric device, miniature conductive springs and a printed
circuit board, attaching the springs to mounting pads of the
piezoelectric transformer, and attaching the springs to the printed
circuit board. Also disclosed is an apparatus made according to the
method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of a piezoelectric transformer
having springs attached thereto according to a preferred embodiment
of the present invention; and
[0009] FIG. 2 is a side view of a piezoelectric transformer
attached to a printed circuit board according to a preferred
embodiment of the present invention and a graph of vibrational
displacement of the piezoelectric transformer versus position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0010] Referring to FIGS. 1 and 2, there is shown a piezoelectric
transformer 10. The piezoelectric transformer 10 is a Rosen or
modified Rosen style operating in a one-lambda length resonance
mode. As a result, the transformer 10 will have first and second
minimum displacement nodes 12, 14 located at approximately 25% and
75% of the transformer's length. Two electrical connections and a
mechanical connection are normally made at the first minimum
displacement node 12. A second mechanical mounting and an optional
feedback electrical connection are normally made at the second
minimum displacement node 14. An output electrical connection must
be made on the end of the device, which is a displacement maximum
and is extremely sensitive to mechanical dampening. The present
Rosen style piezoelectric transformer is shown by way of example
and not intended as a limitation. Other transformer styles and
other piezoelectric devices may have different geometries and may
operate in different modes without departing from the scope of the
present invention.
[0011] Referring to FIG. 2, the present invention uses electrically
conductive, miniature metal compression springs 16 to realize both
electrical connection and mechanical mount. The dimensions and
compliance of the springs 16 are selected to match the requirements
of the transformer 10. Spring characteristics vary with the size of
the piezoelectric transformer 10, such that larger piezoelectric
transformers 10 require larger springs 16, larger pads can
accommodate larger spring diameters, different vibrational
frequencies require springs with different spring constants.
Additionally the pitch and number of coils of the spring 16
determine a distance A that the piezoelectric transformer 10 is
spaced away from a printed circuit board 18 to which the
piezoelectric transformer 10 is mounted.
[0012] When the piezoelectric transformer 10 has four electrical
connections, as described above, at least four springs 16 would be
used. The springs 16 are attached to metallized pads 18 of the
piezoelectric device 10 by solder. Preferably, the springs 16 are
attached to mounting pads 17 of the piezoelectric device 10 before
the springs are attached to the printed circuit board. Next, the
springs 16 are attached to the printed circuit board by soldering.
In some cases the solder connection will be facilitated by the use
of a feedthrough via in the printed circuit board. In this manner
the springs 16 act as a compliant mechanical connection and
electrical connection of the piezoelectric transformer to the
printed circuit board 18. It is also contemplated that a conductive
epoxy could be used to attached the springs to the piezoelectric
device and the printed circuit board in place of solder.
[0013] While the specific embodiment has been illustrated and
described, numerous modifications come to mind without departing
from the spirit of the invention. The scope of protection is only
limited by the scope of the accompanying claims not the specific
embodiment of those claims described above.
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