U.S. patent application number 11/382876 was filed with the patent office on 2007-10-11 for adhesive compositions, micro-fluid ejection devices, and methods for attaching micro-fluid ejection heads.
Invention is credited to David Christopher Graham, Gary Anthony JR. Holt, Jonathan Harold Laurer, Johnny Dale II Massie, Melissa Marie Waldeck, Sean Terrence Weaver, Rich Wells.
Application Number | 20070236542 11/382876 |
Document ID | / |
Family ID | 38574771 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070236542 |
Kind Code |
A1 |
Graham; David Christopher ;
et al. |
October 11, 2007 |
Adhesive Compositions, Micro-Fluid Ejection Devices, and Methods
for Attaching Micro-Fluid Ejection Heads
Abstract
Adhesive compositions, micro-fluid ejection devices, and methods
for attaching micro-fluid ejection heads to devices. One such
adhesive composition is provided for use in attaching a micro-fluid
ejection head to a device, such as to reduce chip bowing and/or to
decrease chip fragility upon curing of the adhesive. Such an
exemplary composition may include one having from about 50.0 to
about 95.0 percent by weight of at least one cross-linkable resin
selected from the group consisting of epoxy resins, siloxane
resins, urethane resins, and functionalized olefin resins; from
about 0.1 to about 25.0 percent by weight of at least one thermal
curative agent; and from about 0.0 to about 30.0 percent by weight
filler, and exhibit a relatively low shear modulus upon curing
(e.g., less than about 10.0 MPa at 25.degree. C.).
Inventors: |
Graham; David Christopher;
(Lexington, KY) ; Holt; Gary Anthony JR.;
(Lexington, KY) ; Laurer; Jonathan Harold; (Boone,
NC) ; Massie; Johnny Dale II; (Lexington, KY)
; Waldeck; Melissa Marie; (Lexington, KY) ;
Weaver; Sean Terrence; (Union, KY) ; Wells; Rich;
(Westerville, OH) |
Correspondence
Address: |
LEXMARK INTERNATIONAL, INC.;INTELLECTUAL PROPERTY LAW DEPARTMENT
740 WEST NEW CIRCLE ROAD
BLDG. 082-1
LEXINGTON
KY
40550-0999
US
|
Family ID: |
38574771 |
Appl. No.: |
11/382876 |
Filed: |
May 11, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60743920 |
Mar 29, 2006 |
|
|
|
Current U.S.
Class: |
347/70 |
Current CPC
Class: |
B41J 2/1601 20130101;
B41J 2/1408 20130101; B41J 2/1623 20130101; B41J 2/14024
20130101 |
Class at
Publication: |
347/070 |
International
Class: |
B41J 2/045 20060101
B41J002/045 |
Claims
1. A thermally curable adhesive composition for attaching a
micro-fluid ejection head to a device, the adhesive comprising a.
from about 50.0 to about 95.0 percent by weight of at least one
cross-linkable resin selected from the group consisting of epoxy
resins, siloxane resins, urethane resins, and functionalized olefin
resins; b. from about 0.1 to about 25.0 percent by weight of at
least one thermal curative agent; and c. from about 0.0 to about
30.0 percent by weight filler, wherein the composition exhibits a
relatively low shear modulus upon curing.
2. The adhesive composition of claim 1 wherein the at least one
thermal curative agent comprises a curative agent selected from the
group consisting of imidazoles, amines, peroxides, organic
accelerators, and sulfur.
3. The adhesive composition of claim 1, further comprising from
about 0.1 to about 10.0 percent by weight silane coupling
agent.
4. The adhesive composition of claim 1, wherein the filler further
comprises a. from about 0.0 to about 20.0 percent by weight epoxy
silane; b. from about 0.0 to about 30.0 percent by weight titanium
dioxide; and c. from about 0.0 to about 30.0 percent by weight
fumed silica.
5. The adhesive composition of claim 1, wherein the adhesive
composition comprises a. from about 36.0 to about 39.0 percent by
weight multi-functional epoxy resin; b. from about 36.0 to about
39.0 percent by weight aliphatic di-functional epoxy resin; c. from
about 7.0 to about 10.0 percent by weight phenolic cross-linking
agent; and d. from about 7.0 to about 12.0 percent by weight of at
least one thermal curative agent.
6. The adhesive composition of claim 5, wherein the at least one
thennal curative agent comprises an imidazole catalyst.
7. The adhesive composition of claim 6, further comprising from
about 0.1 to about 10.0 percent by weight silane coupling
agent.
8. The adhesive composition of claim 7, further comprising a. from
about 0.0 to about 30.0 percent by weight titanium dioxide; and b.
from about 0.0 to about 30.0 percent by weight fumed silica.
9. The adhesive composition of claim 1, wherein the adhesive
composition comprises a. from about 77.0 to about 82.0 percent by
weight diphenyl siloxane resin, and b. from about 5.0 to about 10.0
percent by weight of at least one thermal curative agent.
10. The adhesive composition of claim 9, wherein the at least one
thermal curative agent comprises tetraethylenepentamine.
11. The adhesive composition of claim 10, further comprising from
about 0.1 to about 10.0 percent by weight silane coupling
agent.
12. The adhesive composition of claim 11, further comprising a.
from about 0.0 to about 30.0 percent by weight titanium dioxide;
and b. from about 0.0 to about 30.0 percent by weight fumed
silica.
13. The adhesive composition of claim 1, wherein the adhesive
composition comprises a. from about 18.0 to about 22.0 percent by
weight multi-functional epoxy resin; b. from about 18.0 to about
22.0 percent by weight epoxy siloxane resin; c. from about 38.0 to
about 42.0 percent by weight carboxyl terminated butadiene; and d.
from about 9.0 to about 13.0 percent by weight of at least one
thermal curative agent.
14. The adhesive composition of claim 13, wherein the at least one
thermal curative agent comprises amine adduct.
15. The adhesive composition of claim 14, further comprising from
about 0.1 to about 10.0 percent by weight silane coupling
agent.
16. The adhesive composition of claim 15, further comprising a.
from about 0.0 to about 30.0 percent by weight titanium dioxide;
and b. from about 0.0 to about 30.0 percent by weight fumed
silica.
17. The adhesive composition of claim 1, wherein the adhesive
composition comprises a. from about 1.0 to about 50.0 percent by
weight epoxidized butadiene resin; b. from about 1.0 to about 75.0
percent by weight anhydride functional butadiene; c. from about 0.1
to about 20.0 percent by weight anhydride cross-linking agent; and
d. from about 0.1 to about 20.0 percent by weight of at least one
thermal curative agent.
18. The adhesive composition of claim 17, wherein the at least one
thermal curative agent comprises azine imidazole.
19. The adhesive composition of claim 18, further comprising from
about 0.1 to about 10.0 percent by weight silane coupling
agent.
20. The adhesive composition of claim 19, further comprising a.
from about 0.0 to about 30.0 percent by weight titanium dioxide;
and b. from about 0.0 to about 30.0 percent by weight fumed
silica.
21. The adhesive composition of claim 1, wherein the adhesive
composition comprises a. from about 50.0 to about 95.0 percent by
weight methacrylated butadiene resin, and b. from about 0.1 to
about 15.0 percent by weight of at least one thermal curative
agent.
22. The adhesive composition of claim 21, wherein the at least one
thennal curative agent comprises peroxide catalyst.
23. The adhesive composition of claim 22, further comprising from
about 0.1 to about 10.0 percent by weight silane coupling
agent.
24. The adhesive composition of claim 23, further comprising a.
from about 0.0 to about 30.0 percent by weight titanium dioxide;
and b. from about 0.0 to about 30.0 percent by weight fumed
silica.
25. A micro-fluid ejection device comprising an ejector chip and a
thermally curable adhesive attached thereto, the adhesive having a
shear modulus of less than about 10.0 MPa at 25.degree. C.
26. The micro-fluid ejection device of claim 25, wherein the
adhesive comprises an adhesive having a shear modulus of less than
about 3.0 MPa at 25.degree. C.
27. The micro-fluid ejection device of claim 25, wherein the
adhesive comprises an adhesive having a shear modulus of less than
about 1.0 MPa at 25.degree. C.
28. A micro-fluid ejection device comprising an ejector chip and a
thermally curable adhesive attached thereto, the adhesive having a
glass transition temperature of less than about 65.degree. C.
29. The micro-fluid ejection device of claim 28, wherein the
adhesive comprises an adhesive having a glass transition
temperature of less than about 50.degree. C.
30. The micro-fluid ejection device of claim 28, wherein the
adhesive comprises an adhesive having a glass transition
temperature of less than about at 25.degree. C.
31. A method for attaching a micro-fluid ejection head to a device
comprising: a. attaching a micro-fluid ejection head to a device
with a thermally curable adhesive disposed between the ejection
head and the device, the thermally curable adhesive composition
comprising i. from about 50.0 to about 95.0 percent by weight of at
least one cross-linkable resin selected from the group consisting
of epoxy resins, siloxane resins, urethane resins, and
functionalized olefin resins, ii. from about 0.0 to about 25.0
percent by weight of at least one thermal curative agent; and iii.
from about 0.0 to about 30.0 percent by weight filler, wherein the
composition exhibits a relatively low shear modulus upon curing;
and b. curing the adhesive composition to provide a micro-fluid
ejection device.
32. The method of claim 31 wherein the adhesive composition
comprises a mixture having a shear modulus of less than 10.0 MPa at
25.degree. C.
33. The method of claim 31 wherein the adhesive composition
comprises a mixture having a shear modulus of less than 3.0 MPa at
25.degree. C.
34. The method of claim 31 wherein the adhesive composition
comprises a mixture having a shear modulus of less than 1.0 MPa at
25.degree. C.
35. The method of claim 31 wherein the adhesive composition
comprises a mixture having a glass transition temperature of less
than 65.degree. C.
36. The method of claim 31 wherein the adhesive composition
comprises a mixture having a glass transition temperature of less
than 25.degree. C.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of provisional
application Ser. No. 60/743,920, filed Mar. 29, 2006.
TECHNICAL FIELD
[0002] The disclosure relates to adhesive compositions, and in one
particular embodiment, to flexible compounds that can be cured for
use as adhesives in micro-fluid ejection devices.
BACKGROUND AND SUMMARY
[0003] Micro-fluid ejection heads are useful for ejecting a variety
of fluids including inks, cooling fluids, pharmaceuticals,
lubricants and the like. A widely used micro-fluid ejection head is
an inkjet print head used in an ink jet printer. Ink jet printers
continue to be improved as the technology for making their
micro-fluid ejection heads continues to advance.
[0004] In the production of conventional thermal ink jet print
cartridges for use in ink jet printers, one or more micro-fluid
ejection heads are typically bonded to one or more chip pockets of
an ejection device structure. A micro-fluid ejection head typically
includes a fluid-receiving opening and fluid supply channels
through which fluid travels to a plurality of bubble chambers. Each
bubble chamber includes an actuator such as a resistor which, when
addressed with an energy pulse, momentarily vaporizes the fluid and
forms a bubble which expels a fluid droplet. The micro-fluid
ejection head typically comprises an ejector chip and a nozzle
plate having a plurality of discharge orifices formed therein.
[0005] A container, which may be integral with, detachable from or
remotely connected to (such as by tubing) the ejection device
structure, serves as a reservoir for the fluid and includes a fluid
supply opening that communicates with a fluid-receiving opening of
a micro-fluid ejection head for supplying ink to the bubble
chambers in the micro-fluid ejection head.
[0006] During assembly of the micro-fluid ejection head to the
ejection device structure, an adhesive is used to bond the ejection
head to the ejection device structure. The adhesive "fixes" the
micro-fluid ejection head to the ejection device structure such
that its location relative to the ejection device structure is
substantially immovable and does not shift during processing or use
of the ejection head. The bonding and fixing step is often referred
to as a "die attach step." Further, the adhesive may provide
additional functions such as serving as a fluid gasket against
leakage of fluid and as corrosion protection for conductive
tracing. The latter function for the adhesive is referred to as
part of the adhesive's encapsulating function, thereby further
defining the adhesive as an "encapsulant" to protect electrical
components of or used with the micro-fluid ejection head, such as a
flexible circuit (e.g., a TAB circuit) attached to the micro-fluid
ejection head.
[0007] However, the micro-fluid ejection head and the ejection
device structure typically have dissimilar coefficients of thermal
expansion. For example, micro-fluid ejection heads may have silicon
or ceramic substrates that are bonded to an ejection device
structure that may be a polymeric material such as a modified
phenylene oxide. Thus, the adhesive must often accommodate both
dissimilar expansions and contractions of the micro-fluid ejection
head and the ejection device structure, and be resistant to attack
by the ejected fluid.
[0008] Conventional adhesive materials tend to be non-flexible and
brittle after curing due to high temperatures required for curing
and relatively high shear modulus of the adhesive materials upon
curing. Such properties may cause the adhesive materials to chip or
crack. It may also cause the components (e.g., micro-fluid ejection
head and/or ejection device structure) to bow, chip, crack, or
otherwise separate from one another, or to be less resilient to
external forces (e.g., chips may be more prone to crack when
dropped). For example, during a conventional thennal curing
process, the ejection device structure typically expands before a
conventional die bond adhesive material is fully cured. The diebond
material thus moves with the expanding device structure, wherein
the diebond material cures with the device structure in an expanded
state. Upon cooling the device structure, the device structure
contracts and, with a rigid, cured diebond material, induces high
stress onto the ejection head to cause the aforementioned bowing,
chipping, cracking, separating, etc. Among other problems, such
events can result in fluid leakage and poor adhesion as well as
malfunctioning of the micro-fluid ejection heads, such as
misdirected nozzles. Moreover, attempts to make adhesive materials
more flexible after curing often lead to adhesive materials that
are less resistant to chemical degradation by the fluids being
ejected.
[0009] Accordingly, a need exists for, amongst other things, a
flexible adhesive composition that is curable at relatively low
temperatures and that is suitable for use in assembling micro-fluid
ejection head components, and particularly, for attaching
micro-fluid ejection heads to ejection device structures.
[0010] With regard to the foregoing and other object and
advantages, various embodiments of the disclosure provide a
thermally curable adhesive composition for attaching a micro-fluid
ejection head to a device wherein the adhesive has a relatively low
shear modulus upon curing. Various exemplary embodiments also
provide a micro-fluid ejection head having an ejector chip and a
thermally curable adhesive attached thereto, the adhesive having a
shear modulus of less than about 10 MPa at 25.degree. C., wherein
"MPa" stands for "MegaPascals" (i.e., 1.0.times.10.sup.6
Pascals).
[0011] Additionally, embodiments provide a micro-fluid ejection
device having an ejector chip and a thermally curable adhesive
attached thereto, the adhesive having a glass transition
temperature of less than about 65.degree. C. Various other
embodiments provide a method for attaching a micro-fluid ejection
head to a device. One such method includes attaching the head to a
device with a thermally curable adhesive with a relatively low
shear modulus dispensed between the head and the device, and curing
the adhesive composition to provide the micro-fluid ejection
device.
[0012] Advantages of the exemplary embodiments may include, but are
not limited to, a reduction in ejector chip substrate bow, an
increase in ejector head durability, increased planarity of the
ejector head, and the like. Other advantages might include the
provision of adhesives having improved mechanical, adhesive, and
ink resistive properties. Reduced stresses may be present in the
ejector head substrates due to the presence of improved adhesives
according to the disclosed embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Further features and advantages of the disclosed embodiments
may become apparent by reference to the detailed description when
considered in conjunction with the figures, which are not to scale,
wherein like reference numbers indicate like elements through the
several views, and wherein:
[0014] FIG. 1 is a perspective view of a micro-fluid ejection
device according to an exemplary embodiment of the disclosure;
[0015] FIG. 2, is a perspective view, not to scale, of an ink jet
printer capable of controlling a micro-fluid ejection device
according to the disclosure;
[0016] FIG. 3 is a cross-sectional view, not to scale, of a portion
of a micro-fluid ejection device according to an embodiment of the
disclosure;
[0017] FIG. 4A is a cross-sectional view, not to scale, of a
micro-fluid ejection device incorporating one or more prior art
adhesive compositions; and
[0018] FIG. 4B is a cross-sectional cutaway side view, not to
scale, of a portion of a micro-fluid ejection device according to
an embodiment of the disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0019] In general the disclosure is directed to describing improved
compositions, structures, and methods related to thermally curable
adhesives used to assemble component parts of micro-fluid ejection
devices. More specifically, the improved adhesive compositions
discussed herein might be used to, for example, reduce residual
stresses that may result from heat-treating micro-fluid ejection
heads to cure the adhesives.
[0020] In order to more fully disclose various embodiments of the
invention, attention is directed to the following description of a
representative micro-fluid ejection device incorporating the
improved thermally curable adhesive described herein. With
reference to FIG. 1, there is shown, in perspective view, a
micro-fluid ejection device 10 including one or more micro-fluid
ejection heads 12 attached to a head portion 14 of the device 10. A
fluid reservoir 16 containing one or more fluids is fixedly (or
removably) attached to the head portion 14 for feeding fluid to the
one or more micro-fluid ejection heads 12 for ejection of fluid
toward a media or substrate from nozzles 18 on a nozzle plate 20.
Although FIG. 1 illustrates the fluid reservoir being directly
attached to a head portion 14, other embodiments might attach a
fluid reservoir indirectly to a head portion, such as by tubing,
for example. Each reservoir 16 may contain a single fluid, such as
a black, cyan, magenta or yellow ink or may contain multiple
fluids. In the illustration shown in FIG. 1, the device 10 has a
single micro-fluid ejection head 12 for ejecting a single fluid.
However, the device 10 may contain two or more ejection heads for
ejecting two or more fluids, or a single ejection head 12 may eject
multiple fluids, or other variations on the same.
[0021] In order to control the ejection of fluid from the nozzles
18, each of the micro-fluid ejection heads 12 is usually
electrically connected to a controller in an ejection control
device, such as, for example, a printer 21 (FIG. 2), to which the
device 10 is attached. In the illustrated embodiment, connections
between the controller and the device 10 are provided by contact
pads 22 which are disposed on a first portion 24 of a flexible
circuit 26. An exemplary flexible circuit 26 is formed from a
resilient polymeric film, such as a polyimide film, which has
conductive traces 28 thereon for conducting electrical signals from
a source to the ejection head 12 connected to the traces 28 of the
flexible circuit 26. A second portion 30 of the flexible circuit 26
is typically disposed on an operative side 32 of the head portion
14. The reverse side of the flexible circuit 26 typically contains
the traces 28 which provide electrical continuity between the
contact pads 22 and the micro-fluid ejection heads 12 for
controlling the ejection of fluid from the micro-fluid ejection
heads 12. TAB bond or wire bond connections, for example, are made
between the traces 28 and each individual micro-fluid ejection head
12 as described in more detail below.
[0022] Exemplary connections between a flexible circuit and a
micro-fluid ejection head are shown in detail by reference to FIG.
3. As described above, flexible circuits 26 contain traces 28 which
are electrically connected to a substrate 34. The substrate 34 may
be part of an ejector chip having resistors and/or other actuators,
such as piezoelectric devices or MEMs devices for inducing ejection
of fluid through nozzles 18 of a nozzle plate 20 toward a print
media. Connection pads 36 on the flexible circuits 26 are
operatively connected to bond pads 38 on the substrate 34, such as
by TAB bonding techniques or by use of wires 40 using a wire
bonding procedure through windows 42 and/or 44 in the circuit 26
and/or nozzle plate 20.
[0023] As shown in FIG. 3, the substrate 34 is attached to the head
portion 14, such as in a chip pocket 46. Prior to attaching the
substrate 34 to the head portion 14, a nozzle plate 20 may be
adhesively attached to the ejector chip using adhesive 48 (in
another embodiment, a nozzle plate may be attached to the ejector
chip by forming the nozzle plate on the substrate using
photoimageable techniques). The assembly provided by the nozzle
plate 20 attached to the substrate 34 is referred to herein as the
substrate/nozzle plate assembly 20/34 (FIG. 3). In some
embodiments, the assembly 20/34 encompasses the micro-fluid
ejection head itself.
[0024] The adhesive 48 may be a heat curable adhesive such a
B-stageable thermal cure resins including, but not limited to
phenolic resins resorcinol resins, epoxy resins, ethylene-urea
resins, furane resins, polyurethane resins and silicone resins. The
adhesive 48 may be cured before attaching the substrate 34 to the
head portion 14 and, in an exemplary embodiment, the adhesive 48
has a thickness ranging from about 1 to about 25 microns.
[0025] After bonding the nozzle plate 20 and substrate 34 together,
the substrate/nozzle plate assembly 20/34 may be attached to the
head portion 14 in chip pocket 46 using a die bond adhesive 50. In
various embodiments of the disclosure, the die bond adhesive 50
used to connect the substrate/nozzle plate assembly 20/34 to the
head portion 14 includes one or more adhesive components that make
up a composition having a relatively low shear modulus.
[0026] "Shear modulus" involves the relation of stress to strain
according to Hooke's Law as shown in Equation (1) as follows:
(stress)=.parallel.(strain) (1)
[0027] In Equation (1) m represents a quantity often referred to as
rigidity. When the relationship illustrated by Equation (1) is
applied to a force "F" across a given area "A," Equation (1) may be
more specifically represented by Equation (2) as follows:
F/A=.mu.(.DELTA.L/L) (2)
[0028] In Equation (2) above, the variable "L" represents original
length of an object before said object was acted upon by force F.
".DELTA.L" represents the change in length occurring after force
"F" has acted upon the object. Therefore, the rigidity (".mu.") of
the object is a proportionality constant relating the pressure
applied to an object with the ratio between the object change in
length with the objects original length.
[0029] When Equation (2) and a given rigidity value ".mu." are used
to determine elastic properties of an object, Equation (3), shown
below, is used to derive a shear modulus value from the rigidity m
value determined in Equation (2). Equation (3) is shown below as
follows: .mu.=E/2(L+v) (3) In Equation (3) above, shear modulus is
the proportional relationship between rigidity ".gamma." and the
right hand side of the equation, including the Poisson ratio "v"
and Young's modulus "E."
[0030] Applying Hooke's Law and elasticity theory to physical
properties of micro-fluid ejection heads, reliable data may be
established to correlate the elastic properties of adhesives with
the effect of said adhesives on one or more surfaces of a
micro-fluid ejection head. Shear modulus values are dependent on
temperature, therefore, a given shear modulus value for a given
adhesive will be given in pressure units at a specific temperature.
Various embodiments of the disclosure include compositions with
shear modulus values of less than 10 MPa at 25.degree. C. as
determine by a rheometer from TA Instruments of New Castle, Del.
under the trade name ARES in a dynamic parallel plate configuration
with a frequency of 1.0 rad/sec and a strain of 0.3% after the
material is cured. In certain exemplary embodiments, one or more of
the claimed compositions have shear modulus values of less than
about 1.0 MPa at 25.degree. C.
[0031] With reference now to FIG. 4A, a cross-sectional view of a
non-planar micro-fluid ejection head 12 (e.g., substrate/nozzle
plate assembly 20/34) is illustrated. The substrate/nozzle plate
assembly 20/34 is attached to a head portion 14 in a chip pocket
46. In the prior art ejection head 12, the substrate/nozzle plate
assembly 20/34 was attached to the chip pocket 46 using a prior art
die attach adhesive 58 having a shear modulus of substantially more
than 10 MPa at 25.degree. C. The non-planar characteristic of
micro-fluid ejection head 12 is caused at least in part by high
temperature curing of the die attach adhesive 58.
[0032] The example shown in FIG. 4A is provided to illustrate
certain undesirable effects of high temperature curing including
non-planar micro-fluid ejection head surfaces causing undesirable
effects such as "chip bowing," adhesive layer cracking, and
increased overall fragility of the micro-fluid ejection head 12 and
substrate/nozzle plate assembly 20/34. Chip bowing typically
results from the substrate/nozzle plate assembly 20/34 and the head
portion 14 having dissimilar coefficients of thermal expansion,
since the surface of the substrate/nozzle plate assembly 20/34
bonded to the head portion 14 most commonly is silicon or ceramic
and the portion 14 is, for example, typically a polymeric material
such as a modified phenylene oxide. Thus, the adhesive 58 should be
flexible enough to accommodate both the dissimilar expansions and
contractions of the substrate chip/nozzle plate assembly 20/34 and
the head portion 14. Chip bowing may result in nozzles being
misaligned or aligned at an undesired angle (often called
"planarity" of nozzles), which may also diminish the quality of
fluid ejected from the nozzles.
[0033] Chip fragility is believed to increase in severity because
the adhesive layer reaches its glass transition temperature
(T.sub.g) before the substrate/nozzle plate assembly 20/34 and head
portion 14 have finished cooling and contracting relative to one
another after the curing of the adhesive layer 58, imparting stress
onto the substrate/nozzle plate assembly. Accordingly, in an
exemplary embodiment of the invention, an adhesive is used that has
glass transition temperature below the temperature to which the
head portion 14 is cooled. For example, an adhesive with a glass
transition temperature of less than about 65.degree. C., such as
one having a glass transition temperature of less than about
50.degree. C. or less than about 25.degree. C. might be used in an
exemplary embodiment.
[0034] The glass transition temperature of a material with elastic
properties is the temperature at which the material transitions to
more brittle physical properties or more elastic physical
properties, depending on whether the temperature is decreasing or
increasing, respectively. After curing, as the adhesive layer 58
cools below its glass transition temperature, the adhesive 58
becomes significantly more brittle than before reaching its glass
transition temperature. If the adhesive 58 is stretched or
compressed at a temperature below its glass transition temperature,
the adhesive may crack or buckle. Therefore, using adhesives with
lower glass transition temperatures will decrease the chances of
adhesive cracking or buckling. Similarly, considering that shear
modulus values directly relate to how brittle an adhesive will be
at a given temperature, adhesives having lower shear modulus values
are more flexible at lower temperatures, thereby decreasing the
likelihood of adhesive cracking or buckling. Adhesive layer
cracking may result in a compromised fluid seal, whereby
micro-fluid ejection fluid leaks from the substrate/nozzle plate
assembly 20/34 might cause undesirable deposits of fluid, and/or
corrosion of electrical components.
[0035] High curing temperatures may also cause increased fragility.
Adhesives having lower shear modulus values and lower glass
transition temperatures may be cured with lower temperatures
thereby, decreasing the chances for micro-fluid ejection head
fragility. Increased fragility of micro-fluid ejection heads
increases the chances for micro-fluid ejection products becoming
unfit for use due to shattering of micro-fluid ejections heads and
other parts of the micro-fluid ejection device.
[0036] In contrast to FIG. 4A, the head portion 14 shown in FIG. 4B
illustrates a micro-fluid ejection head 12 comprising a
substrate/nozzle plate assembly 20/34 that is attached to the chip
pocket 46 using die attach adhesive 50 made of one or more of the
compositions described herein. Using compositions such as that
described below may result in decreased chip bowing, decreased
micro-fluid ejection head cracking, and/or decreased fragility of
micro-fluid ejection heads. Such improved characteristics may be
possible by the use of a die attach adhesive having a relatively
low shear modulus. For the purposes of certain embodiments in this
disclosure, "relatively low shear modulus" is defined as a shear
modulus at least lower than about 10 MPa at 25.degree. C.
"Relatively low shear modulus" may, however, be defined as a shear
modulus lower than about 1.0 MPa at 25.degree. C. for certain
exemplary embodiments disclosed herein.
[0037] In an exemplary embodiment, die attach adhesive 50 is a
composition including (1) from about 50.0 to about 95.0 percent by
weight of at least one cross-linkable resin selected from the group
of epoxy resins, siloxane resins, urethane resins, and
functionalized olefin resins; (2) from about 0.1 to about 25.0
percent by weight of at least one thermal curative agent selected
from the group of imidazoles, amines, peroxides, organic
accelerators, and sulfur; and (3) from about 0.0 to about 30.0
percent by weight filler, wherein the composition exhibits a
relatively low shear modulus upon curing. In some variations of
these exemplary embodiments, the adhesive 50 may include from about
0.0 to about 10.0 percent by weight silane coupling agent. In the
embodiments described above, the filler may include from about 0.0
to about 30.0 percent by weight titanium dioxide, and from about
0.0 to about 30.0 percent by weight fumed silica or another filler
component such as clay or functionalized clay, silica, talc, carbon
black, carbon fibers.
[0038] More specific exemplary embodiments of the composition of
adhesive 50 are listed in Tables 1 through Table 7 below.
TABLE-US-00001 TABLE 1 (Composition 1) Concentration Material
(percent by weight) Trade name Supplier Flexible epoxy 37.8 GE-35
CVC resin Aliphatic flexible 37.8 Epalloy 3-23 CVC epoxy resin
Bisphenol M 8.4 Bisphenol M Aldrich Imidazole catalyst 9.5
Curezol-17-Z Air Products Epoxy silane 0.2 A-187 GE Silicones
Titanium dioxide 4.2 Ti-Pure R-900 DuPont Fumed Silica 2.1 TS-720
Cabot
[0039] As shown above, composition 1 includes from about 25.0 to
about 50.0 percent by weight multi-functional epoxy resin; from
about 25.0 to about 50.0 percent by weight aliphatic di-functional
epoxy resin; and from about 0.1 to about 15.0 percent by weight
phenolic cross-linking agent. The composition also includes from
about 0.1 to about 20.0 percent by weight of an imidazole catalyst
and from about 0.0 to about 30.0 weight percent fillers. As shown
in Table 8, Composition 1 has a relatively low shear modulus value
of about 0.225 MPa at 25.degree. C. and a low glass transition
temperature of about 10.5.degree. C.
[0040] There are a number of epoxy resins, curing agents, and
fillers available for application with various embodiments of the
invention. In the first composition illustrated in Table 1, an
exemplary multi-functional epoxy resin is available from CVC
Specialty Chemicals, Inc. under the trade name ERISYS GE-35. An
exemplary aliphatic di-functional epoxy resin is available from CVC
Specialty Chemicals, Inc. under the trade name EPALLOY 3-23. A
suitable phenolic cross-linking agent is available from Signna
Aldrichl Company under the trade designation Bisphenol M. A useful
curing agent is available from Air Products and Chemicals, Inc.
under the trade name CUREZOL C17Z. A suitable epoxy silane coupling
agent is available from GE Advanced Materials, Silicones of Wilton,
Conn. under the trade name SILQUEST A-187 SILANE. Suitable fillers
such as titanium dioxide, and fumed silica are available from a
number of different suppliers. For example, titanium dioxide is
available from DuPont Titanium Technologies under the trade name
TI-PURE R-900 and fumed silica is available from Cabot Corporation
of Boston, Mass. under the trade name CAB-O-SILTS-720.
TABLE-US-00002 TABLE 2 (Composition 2) Concentration Material
(percent by weight) Trade name Supplier Diphenyl siloxane 79.5
PMS-E15 Gelest Tetraethylene- 7.7 TEPA Air Products pentamine Epoxy
Silane 0.9 A-187 GE Silicones Titanium dioxide 4.0 Ti-Pure R-900
Dupont Fumed Silica 7.9 TS-720 Cabot
[0041] In Table 2, composition 2, includes from about 50.0 to about
95.0 percent by weight diphenyl siloxane resin, from about 0.1 to
about 20.0 percent by weight of tetraethylenepentamine, and from
about 0.0 to about 10.0 percent by weight epoxy silane. The fillers
include from about 0.0 to about 30.0 percent by weight titanium
dioxide; and from about 0.0 to about 30.0 percent by weight fumed
silica. As shown in Table 8, Composition 2 has a relatively low
shear modulus value of about 1.98 MPa at 25.degree. C. and a low
glass transition temperature of about -11.2.degree. C.
[0042] In accordance with the foregoing composition, a suitable
diphenyl siloxane resin is available from Gelest, Inc. of
Morrisville, Pa. under the trade name PMS E-15. A useful
tetraethylenepentamine curing agent for this composition is
available from Air Products or Sigma Aldrich Company under the
trade designation TEPA (Tetraethylenepentamine). TABLE-US-00003
TABLE 3 (Composition 3) Concentration Material (percent by weight)
Trade name Supplier Flexible epoxy 19.9 GE-35 CVC resin Epoxy
siloxane 19.9 SIB1115.0 Gelest Carboxyl-terminated 39.7 2000X162
Noveon butadiene Amine adduct 10.7 Ancamine 2337 Air Products Epoxy
Silane 0.2 A-187 GE Silicones Titanium dioxide 4.0 Ti-Pure R-900
Dupont Fumed Silica 5.6 TS-720 Cabot
[0043] Table 3 illustrates yet another exemplary adhesive
composition. Composition 3 includes from about 0.0 to about 50.0
percent by weight multi-functional epoxy resin; from about 0.0 to
about 50.0 percent by weight epoxy siloxane resin; from about 0.0
to about 90.0 percent by weight carboxyl-terminated butadiene; and
from about 0.1 to about 20.0 percent by weight of an amine adduct
thermal curative agent. This embodiment also includes from about
0.0 to about 15.0 percent by weight epoxy silane, from about 0.0 to
about 30.0 percent by weight titanium dioxide, and from about 0.0
to about 30.0 percent by weight fumed silica. As shown in Table 8,
Composition 3 has a substantially low shear modulus value of about
0.175 MPa at 25.degree. C. and a low glass transition temperature
of about -6.7.degree. C.
[0044] In accordance with the foregoing composition, the epoxy
siloxane that may be used is available from Gelest, Inc. is under
the trade designation SIB115.0. The carboxyl-terminated butadiene
that may be used is available from Noveon Specialty Chemicals of
Cleveland, Ohio under the trade name HYCAR CTB 2000X162. A suitable
curing agent in the form of an amine adduct is available from Air
Products and Chemicals, Inc. under the trade name ANCAMINE 2337S.
TABLE-US-00004 TABLE 4 (Composition 4) Concentration Material
(percent by weight) Trade name Supplier Epoxidized 36.2 Poly BD
600E Sartomer butadiene resin Anhydride 50.7 130-MA-8 Sartomer
functional butadiene Anhydride cross 6.1 MHHPA Miller- linker
Stephenson Azine imidazole 2.3 2MZ-Azine Air Products Epoxy Silane
0.4 A-187 GE Silicones Titanium dioxide 2.0 Ti-Pure R-900 DuPont
Fumed Silica 2.3 TS-720 Cabot
As provided in Table 4, Composition 4 includes from about 0.0 to
about 50.0 percent by weight epoxidized butadiene resin; from about
0.0 to about 75.0 percent by weight anhydride functional butadiene;
from about 0.1 to about 20.0 percent by weight anhydride
cross-linking agent; and from about 0.1 to about 20.0 percent by
weight of an azine imidazole thermal curative agent. From about 0.0
to about 15.0 percent by weight epoxy silane; from about 0.0 to
about 30.0 percent by weight titanium dioxide, and from about 0.0
to about 30.0 percent by weight fumed silica are also included in
the composition. As shown in Table 8, Composition 4 has a
considerably lower shear modulus value of about 0.151 MPa at
25.degree. C. and a considerably lower glass transition temperature
of about -30.degree. C.
[0045] For composition 4, a suitable epoxidized butadiene resin is
available from Sartomer Company, Inc. of Exton, Pa. under the trade
name POLY BD 600E. A suitable anhydride functional butadiene resin
that may be used is available from Sartomer Company, Inc. of Exton,
Pa. under the trade name RICON 130MA8. The cross-linking agent that
may be used is available from Miller-Stephenson Chemical Company,
Inc. under the trade designation Anhydride MHHPA. A suitable curing
agent is an azine imidazole that is available from Air Products and
Chemicals, Inc. under the trade name CUREZOL.RTM. 2MZ Azine.
TABLE-US-00005 TABLE 5 (Composition 5) Concentration Material
(percent by weight) Trade name Supplier Methacrylated 86.0 Riacryl
3100 Sartomer butadiene resin Peroxide catalyst 2.8 Luperox LP
Aldrich Epoxy Silane 0.9 A-187 GE Silicones Titanium dioxide 4.3
Ti-Pure R-900 Dupont Fumed Silica 6.0 TS-720 Cabot
[0046] As provided in Table 5 Composition 5 includes from about
50.0 to about 95.0 percent by weight methacrylated butadiene resin,
and from about 0.1 to about 30.0 percent by weight of peroxide
catalyst thermal curative agent, A suitable methacrylated butadiene
resin is available from Sartomer Company, Inc. of Exton, Pa. under
the trade name RICACRYIL 3100. The curing agent is suitably a
peroxide catalyst available from Sigma Aldrich Company under the
trade name LUPEROX LP. As shown in Table 8, Composition 5 has a low
shear modulus value of about 0.74 MPa at 25.degree. C. and a
considerably lower glass transition temperature of less than
-60.degree. C. TABLE-US-00006 TABLE 6 (Composition 6) Concentration
Material (percent by weight) Trade name Supplier Flexible epoxy
73.6-88.0 EXA-4850 Dainippon resin Ink Bisphenol M 0-8.4 Bisphenol
M Aldrich Imidazole 9.2-11.0 CUREZOL-17-Z Air Products catalyst
Epoxy Silane 0.8-1.0 A-187 GE Silicones Amine adduct 0-4.1 ANCAMINE
2337 Air Products Fumed Silica 0-4.1 TS-720 Cabot
[0047] As provided in Table 6, Composition 6 includes from about
50.0 to about 95.0 percent by weight flexible epoxy resin, from
about 0.0 to about 30 percent by weight bisphenol-M, and from about
0.1 to about 20.0 percent by weight of imidazole catayst thennal
curative agent. A suitable flexible epoxy resin is available from
Dainippon Ink and Chemicals, Inc. of Tokyo, Japan under the trade
name EPICLON EXA-4850. As shown in Table 8, Composition 6 has a low
shear modulus value ranging from about 1.75 to about 4.4 MPa at
25.degree. C. and a glass transition temperature ranging from about
20 to about 31.degree. C. TABLE-US-00007 TABLE 7 (Composition 7)
Concentration Material (percent by weight) Trade name Supplier
Flexible epoxy 55.0-88.0 EXA-4850 Dainippon resin Ink Bisphenol-F
0-27.0 830-LVP Dainippon Ink Imidazole 7.4-11.0 CUREZOL-17-Z Air
Products catalyst Epoxy Silane 0.6-1.0 A-187 GE Silicones Amine
adduct 0-3.5 ANCAMINE 2337 Air Products Fumed Silica 0-3.5 TS-720
Cabot
[0048] As provided in Table 7, Composition 7 includes from about
50.0 to about 95.0 percent by weight flexible epoxy resin, from
about 0 to about 50 percent by weight bisphenol-F, from about 0.1
to about 20.0 percent by weight of imidazole catalyst thermal
curative agent, from about 0.1 to about 20 percent by weight epoxy
silane coupling agent, from about 0 to about 20 percent by weight
of amine adduct, and from about 0 to about 30 percent by weight
fumed silica. As shown in Table 8, Composition 7 has a low shear
modulus value ranging from about 3.9 to about 8.7 MPa at 25.degree.
C. and a glass transition temperature ranging from about 27 to
about 60.degree. C.
[0049] A comparison of the shear modulus and glass transition
temperature properties of the Compositions 1-7 compared to a
conventional die bond adhesive available from Emerson & Cuming
of Monroe Townships N.J. under the trade name ECCOBOND 3193-17 are
provided in Table 8. TABLE-US-00008 TABLE 8 Shear Modulus Sample
(MPa) (25.degree. C.) Tg (.degree. C.) Eccobond 3193-17 15.4 92.3
Composition 1 0.225 10.5 Composition 2 1.98 -11.2 Composition 3
0.175 -6.7 Composition 4 0.151 -30 Composition 5 0.74 <-60
Composition 6 1.75-4.4 20-31 Composition 7 3.9-8.72 27.7-60
[0050] As illustrated in Table 8, the ECCOBOND 3193-17 adhesive has
a relatively high shear modulus value of 15.4 MPa at 25.degree. C.
as compared to the shear modulus values of the Compositions 1-7
which are all less than 10 MPa at 25.degree. C. Similarly, the
ECCOBOND 3193-17 has a relatively high glass transition temperature
of 92.3.degree. C. compared to the much lower values of the
compositions 1-7 which are all less than 65.degree. C. In other
words, ECCOBOND 3193-17 becomes significantly more rigid when it
cools to about 92.degree. C., whereas Compositions 1-7 do not
become significantly more rigid until cooling to at least about
65.degree. C.
[0051] Various embodiments of the invention are also directed to a
micro-fluid ejection device including a substrate/nozzle plate
assembly and a thermally curable adhesive attached thereto, the
adhesive having a shear modulus of less than about 10.0 MPa at
25.degree. C. In one particular embodiment, shown in FIG. 4B, a
substrate/nozzle plate assembly 20/34 is attached to head portion
14 by a die attach adhesive 50 made according to Composition 1
above. In a related embodiment, a substrate chip/nozzle plate
assembly 20/34 is attached to a head portion by a die attach
adhesive made according to Composition 2 above. In yet other
embodiments, micro-fluid ejection heads are attached to head
portions by die attach adhesives made according to Compositions 3,
4 and 5 above having a relatively low shear modulus values at
25.degree. C. and having glass transition temperatures of less than
about 65.degree. C.
[0052] It is contemplated, and will be apparent to those skilled in
the art from the preceding description and the accompanying
drawings that modifications and/or changes may be made to the
embodiments of the disclosure. Accordingly, it is expressly
intended that the foregoing description and the accompanying
drawings are illustrative of exemplary embodiments only, not
limiting thereto, and that the true spirit and scope of the present
disclosure be determined by reference to the appended claims.
* * * * *