U.S. patent application number 10/021105 was filed with the patent office on 2002-08-29 for reworkable encapsulant.
This patent application is currently assigned to Teravicta Technologies, Inc.. Invention is credited to Lunceford, Brent D..
Application Number | 20020119605 10/021105 |
Document ID | / |
Family ID | 26829647 |
Filed Date | 2002-08-29 |
United States Patent
Application |
20020119605 |
Kind Code |
A1 |
Lunceford, Brent D. |
August 29, 2002 |
Reworkable encapsulant
Abstract
The present invention provides an improved fluorinated polymer
encapsulant for protectively coating electronic devices in an
electronic device module. Also provided is a method for applying
and reworkably removing the same to and from the electronic device
module. In one embodiment, a coating of a fluorinated polymer
solution is applied to at least a portion of an electronic device
module. The module is then baked to operably fix to it the
fluorinated polymer coating.
Inventors: |
Lunceford, Brent D.;
(Austin, TX) |
Correspondence
Address: |
Erik R. Nordstrom
FULBRIGHT & JAWORSKI L.L.P.
Suite 2400
600 Congress Avenue
Austin
TX
78701
US
|
Assignee: |
Teravicta Technologies,
Inc.
|
Family ID: |
26829647 |
Appl. No.: |
10/021105 |
Filed: |
October 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10021105 |
Oct 22, 2001 |
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09351750 |
Jul 8, 1999 |
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6306688 |
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60131617 |
Apr 28, 1999 |
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Current U.S.
Class: |
438/127 ;
257/787; 257/788; 257/E21.502; 257/E21.503; 257/E23.119;
257/E23.125; 438/125; 438/126 |
Current CPC
Class: |
H01L 2224/48227
20130101; Y10T 29/49721 20150115; H01L 2224/85399 20130101; H01L
2224/73203 20130101; H01L 2224/73204 20130101; H01L 2224/8592
20130101; H05K 3/288 20130101; H01L 2224/16225 20130101; H01L
2924/00014 20130101; H01L 2224/48465 20130101; H01L 2224/48465
20130101; H01L 2224/48091 20130101; H01L 2224/48465 20130101; H01L
2224/05599 20130101; H01L 24/48 20130101; H01L 2224/32225 20130101;
H01L 23/3121 20130101; H01L 21/563 20130101; H01L 2924/00 20130101;
H01L 2924/00012 20130101; H01L 2224/48227 20130101; H01L 2924/00
20130101; H01L 2224/45015 20130101; H01L 2224/48227 20130101; H01L
2224/16225 20130101; H01L 2924/00 20130101; H01L 2924/207 20130101;
H01L 2224/32225 20130101; H01L 2224/32225 20130101; H01L 2224/48091
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2924/00014 20130101; H01L 2224/48091 20130101; H01L 2224/48227
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2224/45099 20130101; H01L 21/56 20130101; H01L 2924/00 20130101;
H01L 2924/14 20130101; H01L 23/293 20130101; H01L 2924/181
20130101; H01L 2924/1815 20130101; H01L 2224/85399 20130101; H01L
2924/00014 20130101; H01L 2224/48465 20130101; H01L 2924/14
20130101; H01L 2224/73265 20130101; H01L 2224/73204 20130101; H01L
2924/00014 20130101; H01L 2924/181 20130101; H01L 2924/01039
20130101; H01L 2224/05599 20130101; H01L 2224/73265 20130101; H01L
2924/19041 20130101; H01L 2224/48091 20130101; H01L 2224/48465
20130101 |
Class at
Publication: |
438/127 ;
438/125; 438/126; 257/788; 257/787 |
International
Class: |
H01L 021/44; H01L
021/48; H01L 021/50; H01L 023/29; H01L 023/28 |
Claims
I claim as follows:
1. A method for encapsulating an electronic device module, the
method comprising: (a) applying a coating of fluorinated polymer
solution to at least a portion of an electronic device module; and
(b) baking the module to operably fix to it the fluorinated
polymer, which serves as a protective coating.
2. The method of claim 1, wherein the act of applying a coating of
fluorinated polymer solution includes applying a coating of HFIP
fluorinated polymer solution.
3. The method of claim 2, wherein the act of applying a coating of
HFIP fluorinated polymer solution includes applying a coating of
12F-PEK polymer.
4. The method of claim 1, wherein the fluorinated polymer solution
includes a solvent, and the act of baking the device includes the
acts of pre-baking within a first temperature range the device to
drive off solvent from the solution prior to baking the device
within a second temperature range that is higher than the first
temperature range.
5. The method of claim 4, wherein the act of baking further
includes ramping the baking temperature from within the first
temperature range to within the second temperature range.
6. The method of claim 5, wherein pre-baking within the first
temperature range includes baking within a temperature range of
90.degree. C. to 120.degree. C.
7. The method of claim 6, wherein baking the device within the
second temperature range includes baking the device within a range
of 180.degree. C. to 220.degree. C.
8. The method of claim 7, wherein ramping from within the first
temperature range to within the second temperature range includes
ramping the temperature within a rate range of 5.degree. C. to
10.degree. C. per minute.
9. The method of claim 4, further comprising the acts of (1)
applying to the device a second coating of the fluorinated polymer
solvent solution after pre-baking the device, and (2) again
pre-baking the device to drive off solvent from the second
coating.
10. The method of claim 9, wherein the acts of applying a second
coating and again pre-baking are performed prior to baking the
device within the second temperature range.
11. The method of claim 1, wherein the act of applying the coating
includes the act of spraying the coating onto the electronic device
module.
12. The method of claim 11, wherein the act of spraying the coating
onto the module includes the act of spraying the coating onto a
chip-on-board module.
13. An electronic device module that is encapsulated according to
the method of claim 1.
14. A method for reworkably removing fixed fluorinated polymer
coating from an electronic device module, the method comprising:
(a) dissolving the fluorinated polymer with a solvent; and (b)
sufficiently removing the dissolved fluorinated polymer coating
from the module in order to rework it.
15. The method of claim 14, further comprising the act of drying
the module.
16. The method of claim 15, wherein the act of drying includes
drying the module with compressed nitrogen gas.
17. The method of claim 14, wherein the dissolved fluorinated
polymer is removed by rinsing the module with a solvent rinse.
18. The method of claim 17, wherein the act of rinsing includes
rinsing with isopropanol.
19. The method of claim 14, wherein the act of dissolving the
fluorinated polymer includes immersing the coated device in the
solvent.
20. The method of claim 19, wherein the act of dissolving the
fluorinated polymer includes dissolving the fluorinated polymer in
xylene.
21. An electronic device module having an improved protective
coating, comprising: (a) a substrate; (b) at least one electronic
device operably connected to the substrate; and (c) a fluorinated
polymer encapsulant protectively adhered about at least a portion
of the at least one electronic device.
22. The module of claim 21, wherein the substrate is a printed
circuit board.
23. The module of claim 21, wherein the substrate and the at least
one electronic device comprise a chip scale package.
24. The module of claim 21, wherein the substrate and the at least
one electronic device comprise an opto-electronic device
module.
25. The module of claim 21, wherein the electronic device is a
flip-chip having an interconnect side facing the substrate.
26. The module of claim 25, wherein fluorinated polymer is used as
underfill between the substrate and the interconnect side of the at
least one flip chip.
27. The module of claim 21, wherein the fluorinated polymer
includes an HFIP bearing thermoplastic.
28. The module of claim 27, wherein the fluorinated polymer
encapsulant comprises two or more layers of the HFIP
thermoplastic.
29. The module of claim 21, further comprising an epoxy encapsulant
sandwiched between the at least one electronic device and the
fluorinated polymer encapsulant.
30. The module of claim 21, wherein the fluorinated polymer
encapsulant includes microscopic inorganic particles for making the
thermal expansion characteristics of the encapsulant closer to
those of the at least one electronic device.
31. The module of claim 30, wherein the inorganic microscopic
particles comprise silica.
Description
[0001] This specification relies upon and hereby incorporates by
reference provisional application No. 60/131,617 entitled
"Reworkable Conformal Coating Methods" filed Apr. 28, 1999.
TECHNICAL FIELD
[0002] The present invention relates to protective coatings for
electronic devices and, in particular, to a protective fluorinated
polymer coating.
BACKGROUND
[0003] Protective device encapsulants, e.g., conformal coatings
were originally developed to protect sensitive electronic
assemblies from the harsh environments experienced in military,
aerospace and marine domains. However, as the level of integration
has increased in the electronic industry, e.g., with SMT and finer
lead pitches associated with VLSI circuitry, the use of and need
for adequate protective coatings has spread into a variety of
commercial (as well as military) applications.
[0004] The continuing miniaturization of electronic systems has
resulted in the integration of direct-chip-attach (or DCA) and
chip-scale-package (or CSP) technologies. These technologies allow
for the miniaturization of electronic systems by means of
eliminating large chip packages. However, improved protective
coatings and associated application and/or removal techniques are
needed to provide such modules with the reliability and field
performance of packaged ICs.
[0005] The ideal encapsulant should have properties that allow for
easy application and removal, low cure temperature, temperature
resistance, humidity resistance, and long potlife. Of the presently
used materials (e.g., acrylics, polyurethanes, epoxies, silicones,
polyimides, and polyparaxylylene) none exhibits all of the ideal
properties for a suitable encapsulant. The tradeoff is typically
between the ease of application and processing on the one hand
versus protective capability and environmental stability on the
other hand. For example, acrylics are generally easy to apply and
remove but typically exhibit low temperature and humidity
resistance. Conversely, polyimides, generally have high temperature
and humidity resistance but are difficult to apply, require a high
cure temperature, and have short pot life. Another example is a
material known as RTV, which has been used to coat chip-on-board
systems. Unfortunately, however, RTV is reactive and cannot be
directly applied without extensive board preparation. Epoxy
coatings may be applied as glob-top encapsulants, but because epoxy
has a significantly different thermal expansion coefficient than
most printed circuit board materials, the curing process and
environmental thermal cycling can result in unacceptable mechanical
stress and failure at the component or board level. In addition,
epoxies are not generally acceptably removable for rework.
Polyurethane has also been used for such coatings, but is unstable
under high temperature and humidity. Significantly, most of these
currently employed coatings are difficult to remove, making repair
problematic and, in some cases, practically impossible.
[0006] Accordingly, what is needed is an improved encapsulant for
protectively coating an electronic device. Moreover, what is needed
is a solution for reworkably encapsulating an electronic device
module.
SUMMARY OF THE INVENTION
[0007] The present invention provides an improved fluorinated
polymer encapsulant for protectively coating electronic devices in
an electronic device module. Also provided is a method for applying
and reworkably removing the same to and from the electronic device
module. In one embodiment, a coating of a fluorinated polymer
solution is applied to at least a portion of an electronic device
module. The module is then baked to operably fix to it the
fluorinated polymer coating.
[0008] In another embodiment of the present invention, a method for
reworkably removing a fixed fluorinated polymer coating from an
electronic device module is provided. The method includes the acts
of dissolving the fluorinated polymer with a solvent and
sufficiently removing the dissolved fluorinated polymer coating
from the module in order to rework it.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A schematically depicts an electronic device module
without any coating.
[0010] FIG. 1B shows the module of FIG. 1A with a coating of
fluorinated polymer solution.
[0011] FIG. 1C shows the module of FIGS. 1A and 1B with a fixed
fluorinated polymer coating.
[0012] FIG. 2A shows an electronic device module prior to being
reworked with its fixed coating in tact.
[0013] FIG. 2B shows the module of FIG. 2A with the fluorinated
polymer coating in a "wet" and at least partially dissolved
state.
[0014] FIG. 2C shows the module of FIGS. 2A and 2B after the
fluorinated polymer coating has been removed.
[0015] FIG. 3 shows a top view of a different electronic device
module.
[0016] FIG. 4 shows a sectional view of an electronic device module
with a device that has a pre-existing epoxy undercoat that is
encapsulated with the present invention.
[0017] FIG. 5 shows an electronic device module with a flip-chip
device that is encapsulated with the present invention.
[0018] FIG. 6 shows an electronic device module 500 with
cooperating opto-electronic devices encapsulated with a fluorinated
polymer coating.
[0019] FIG. 7 shows an electronic device module with a micro opto
electro mechanical system having a lens that is encapsulated with a
fluorinated polymer.
DETAILED DESCRIPTION
[0020] The present invention provides a protective encapsulant and
a method for applying and reworkably removing the same for an
electronic device module.
a. First Embodiment
[0021] FIGS. 1A, 1B, and 1C schematically depict various stages of
encapsulating one embodiment of an electronic device module 100
with the present invention. Conversely, FIGS. 2A, 2B, and 2C show
various stages of removing the coating from the module in order to
rework it.
[0022] Electronic device module 100 includes electronic devices
such as bare integrated circuit chips 110 operably mounted to a
printed circuit board ("PCB") 105 through adhesive 130. The
electronic devices 110 are electrically connected to the PCB 105
through conductors 120. In the depicted embodiment, conductors 120
are wire bonded at one end 122 to the electronic device 110 and at
the other end to the PCB metallization 107. FIG. 1A shows
electronic device module 100 prior to being coated with a
fluorinated polymer of the present invention. FIG. 1B shows the
module 100 after fluorinated polymer solution 140A has been
applied. At this point, the coating is "wet" and not yet fixed to
the module. Finally, FIG. 1C shows module 100 with the fixed (dry)
fluorinated polymer coating 140B. (Note that reference 140A
connotes the fluorinated polymer coating in a wet state, and 140B
identifies the coating in a fixed, dry state.)
[0023] FIG. 2A shows module 100 with a fixed fluorinated polymer
coating 140B; FIG. 2B shows the module 100 having a wet coating
140A as it is being dissolved for removal; and FIG. 2C shows the
module 100 with the coating removed and the module ready to be
reworked.
[0024] Electronic device module 100 and in turn, electronic devices
110 may comprise any electronic components, assemblies, or other
peripheral materials, which require or benefit from the
environmentally-protective coating of the present invention. Such
devices could include but are not limited to bare chips,
flip-chips, opto-electronic devices, and micro-electro-mechanical
system (MEMS) devices. Moreover, an electronic device module may
comprise any combination of devices such as a multi-chip module
(MCM), multi-chip package (MCP), ball grid array ("BGA") package,
plastic encapsulated microcircuit (PEM), a single chip package
(SCP), and even flexible substrate materials. However, the coating
methods of the present invention are particularly well-suited for
direct chip attach ("DCA") and other reworkable applications.
[0025] Within the context of the present invention, a "fluorinated
polymer" can include any suitable hexafluoroisopropylidene
("HFIP")-containing polymer (including both thermosets and
thermoplastics) that provides a suitably protective coating for an
electronic device module with the methods of the present invention.
(Incorporation of the HFIP into a polymer backbone generally
improves a number of its properties, including: increased thermal
stability, increased environmental resistance, increased oxidative
resistance, increased flame resistance, decreased dielectric
constant, and lowered glass transition temperature.) One such
fluorinated polymer is 12F-PEK fluorinated ploy(phenylene ether
ketone), which is disclosed in U.S. Pat. No. 4,902,769 to Cassidy
et al. and is hereby incorporated by reference into this
specification.
[0026] Fluorinated polymers such as thermoplastic polymers bearing
the HFIP group are generally soluble in common organic solvents
such as xylene. The use of a solvent to form a fluorinated polymer
solution generally improves and makes easier application of the
fluorinated polymer onto an electronic device module 100. In one
embodiment, a 5 to 10 percent solution of 12F-PEK fluorinated
polymer in solvent (e.g., xylene) with an inherent viscosity above
0.3 is used. In a more particular embodiment, a solution of 6.4%
12F-PEK in xylene with an inherent viscosity of about 0.8 is used.
This consistency is well-suited for applying (e.g., spraying) the
fluorinated polymer onto the electronic device module 100.
b. Coating Application
[0027] With reference to FIGS. 1A through 1C, a process for
applying a fluorinated polymer coating to device module 100 will be
described.
[0028] In general, the fluorinated polymer solution is initially
applied to the device module 100. It may be applied in a variety of
ways including extrusion, spray coat, brush coat, spin coat, or any
other suitable application method. For example, it may be sprayed
using a conventional sprayer such as a Preval.TM.0 sprayer
available from Shetwin Williams Mfg. and Precision Valve Corp. of
Yonkers, N.Y. After the coating has been adequately applied, the
module 100 with a wet fluorinated polymer coat 140A is fixed
through baking.
[0029] In one embodiment, a first coating of fluorinated polymer
solution is applied via spraying to device module 100. FIG. 1B
shows module 100 after a "wet" coating 140A has been applied. The
module 100 is then baked (or prebaked) within a temperature range
of 90.degree. C. to 120.degree. C. for a time ranging between 30
and 60 minutes to drive off the solvents (e.g., xylene). A second
coating is then applied to the module 100. Again, the module 100 is
prebaked within a range of 90.degree. C. to 120.degree. C. for from
30 to 60 minutes to drive off solvents from the second coating.
Finally, module 100 is subjected to a fixed baking. In one
preferred embodiment, its temperature is ramped to a baking
temperature within a range of between 180.degree. C. to 220.degree.
C. The module is baked within this range for a time of between 60
to 120 minutes. The temperature is preferably ramped from the
prebake to the fixing bake at 5.degree. C. to 10.degree. C. per
minute. A cool down next follows, which preferably is done at
natural rates (e.g., leaving the module within the oven after it
has been turned off). FIG. 1C shows module 100 coated with a fixed
(dry) coating 140B of the fluorinated polymer.
[0030] In one more particular, embodiment, a first coating is spray
applied onto module 100. This is followed by a prebake within a
range of 100.degree. C. to 120.degree. C. for from 45 to 60
minutes. A second coating is applied followed by a prebake at a
range of between 100.degree. C. to 120.degree. C. followed by a
thermal ramp to a range of between 200.degree. C. to 220.degree. C.
held for from 90 to 120 minutes.
[0031] In another more particular embodiment, a first coating is
spray applied. This is followed by a prebake within a range of
110.degree. C. to 120.degree. C. for from 50 to 60 minutes for
driving off solvent. This is then followed with a second applied
coating and prebake at a range of from 110.degree. C. to
120.degree. C. for from 50 to 60 minutes. Finally, the module 100
is ramped to a temperature within a range of 210.degree. C. to
220.degree. C. and held there for from 105 to 120 minutes to fix
the coating. The module is then cooled to room temperature within
the baking oven.
[0032] In a further embodiment of this concept, the fluorinated
polymer would be "filled" with microscopic (1-10 microns) particles
of inorganic material (i.e. silica or alumina) to modify,
especially lower, the coefficient of thermal expansion (or CTE) of
the fluoropolymer matrix. By modifying the coefficient of thermal
expansion of an organic polymer material, the CTE of the polymer
material can be closely matched to that of the electronic
components and/or substrate material therefore leading to increased
reliability of the assembly.
c. Coating Removal
[0033] Reworkability of the module 100 is provided through the
removal of the coating 140B. FIG. 2A shows module 100 prior to
having its coating 140B removed. A fluorinated polymer coating may
generally be removed by dissolving the fluorinated polymer coating
with a solvent (e.g., organic solvent) and sufficiently removing
the dissolved fluorinated polymer coating from the module in order
to appropriately rework it.
[0034] Any suitable solvent that is not reactive with the module
100 may be used. Such a solvent could include but is not limited to
xylene, chloroform, tetrahydrofuran, dimethylacetamide, and
N-methylpyrrolidone, and acetate-based solvents. The solvent used
to apply the fluorinated polymer will normally suffice. In one
embodiment, xylene, which may also be used in the fluorinated
polymer solution, is used to dissolve the fixed coating in order to
remove it. Moreover, the coating 140B may be dissolved by applying
the solvent in any suitable manner. For example, in one embodiment,
the entire module 100 is immersed and soaked in a solvent (e.g.,
xylene) bath. FIG. 2B shows module 100 with a "wet" dissolved
coating 140A.
[0035] After the fluorinated polymer coating is sufficiently
dissolved, it can be removed from the module 100. The dissolved
coating may be removed by any suitable means including rinsing,
blowing, or scraping. In one embodiment, the dissolved fluorinated
polymer is removed by rinsing the module with a solvent rinse,
which may be any suitable material for rinsably removing the
dissolved fluorinated polymer coating. Preferably, this rinse is
relatively volatile and reasonably capable of dissolving the
solvent. Such a rinse could include but is not limited to xylene,
isopropanol and acetone. After the dissolved coating has been
removed, the module may then be dried, e.g., at atmospheric
conditions or with compressed nitrogen. FIG. 2C shows module 100
after the fluorinated polymer coating has been removed. At this
stage the module is ready to be reworked. For example, the active
and/or passive electronic components (e.g., wire bond ICs, flip
chip ICs, or SMF components) would be removed along with their
respective inter connects. The electronic components could then be
replaced with interconnections from the electronic components to
the module or substrate.
d. Other Embodiments
[0036] It will be seen by those skilled in the art that various
changes may be made without departing from the spirit and scope of
the invention. For example, the fluorinated polymer coating is
effective with both silicon and gallium arsenide semiconductor
devices. In addition, while the invention has primarily been
described with the use of two coats of fluorinated polymer, any
number including one or more coats may be used. Moreover, the
fluoropolymer encapsulant of the present invention can be applied
at the board, package, or even wafer level. For example, it can be
applied to a wafer of ICs after fabrication. After applying the
coating, an interconnect metallization layer could be fabricated
and redistributed from IC connecting pads to the substrate
connecting pads. With such an encapsulating process, wafer level
chip-scale-packages with excellent resistance to both heat and
humidity can be manufactured.
[0037] Furthermore, while the invention has primarily been
described as a coating for COB modules, it may be used with various
other electronic devices and electronic device modules.
[0038] FIG. 3 shows a top view of an electronic device module 200.
This module illustrates just some of the many ways the fluorinated
polymer coating of the present invention may be used to protect
electronic devices. Module 200 includes wire-bonded chips 210A,
flip-chips 210 B, opto-electronic devices 210C, and MEMS devices
210D. Other devices that may be used include SMT components (i.e.
decoupling capacitors). Some of the wire-bonded chips 210A are
encapsulated with a conventional epoxy coating 242. The entire (at
least top surface) of the module 200 is encapsulated with a
fluorinated polymer coating 240B. With this embodiment, not only
does the fluorinated coating 240B protect the non-coated devices
(e.g., 210B), but also, it benefits the devices (210A) that are
coated with the conventional epoxy coating because it has a
generally better resistance to humidity. FIG. 4 shows a sectional
view of a module 300 with a device 310A that has a pre-existing
epoxy overcoat or coating. Module 300 includes wire-bonded device
310A mounted to PCB 305 via wire-bond conductors 320. Device 310A
has been originally coated with an epoxy encapsulant 342. For
improved protection from water absorption and/or penetration, a
coat of fluorinated polymer 340B is applied to encapsulate the
epoxy coat 342.
[0039] FIG. 5 shows an electronic device module 400 with a
flip-chip device. Module 400 includes flip-chip 210B electrically
connected to PCB 405 through metal contact balls (or bumps) 414. In
the depicted embodiment, a conventional material (e.g., epoxy) is
used as an underfill 442, and fluorinated polymer 440B is used to
encapsulate the device 410B within module 400. However, fluorinated
polymer could also be used as the underfill.
[0040] FIG. 6 shows an electronic device module 500 with
cooperating opto-electronic devices 510C and 510C' mounted to
substrate 505. Device 510C includes emitter 512 (e.g. vertical
cavity surface emitting lasers or VC SEC) for photonically
communicating or lining it with device 510C' through receiver or
detector 514. FIG. 6 depicts horizontal communication between
devices 510C and 510C', however, the communication between device
510C and 510C' may be vertical in nature. Each device is coated or
encapsulated with fluoropolymer 540B to provide environmental
protection. Because of its translucent nature (or optical clarity),
fluorinated polymer 540B is ideally suited for protectively
encapsulating opto-electronic devices.
[0041] In this embodiment, opto-electric communication is depicted
to occur between opto-electric devices 510C and 510C' which exist
on the same module or substrate. A further embodiment includes
optoelectronic communication between opto-electronic devices on
separate modules (module to module communication).
[0042] FIG. 7 shows an electronic device module 600 with a micro
opto electro mechanical actuator system that incorporates a
fluorinated polymer encapsulant of the present invention. The
system includes a metallic source 611, metallic gate 613, and a
metallic drain 615 mounted atop a transparent substrate 605. An
overhang beam 617 is mounted at one end to the metallic source 611.
The overhanging beam 617 in connection with substrate 605, source
611, gate 613, and drain 615 define a gap region that is created
from a removed sacrificial layer. Beam 617 includes an opening (not
shown) 618 in alignment with an underlying light source. A lens
640B is mounted to beam 617 in alignment with opening 618. The lens
640B is composed of a fluorinated polymer of the present invention.
In one embodiment, the lens is spin-coated and defined until it has
an acceptable convexity. The system also includes a detector 619
for receiving bit light from the light source through lens 640B.
The fluorinated polymer, with its translucent nature and resistance
to heat and humidity, works well as a lens material. In another
embodiment, a conventional lens coated with a fluorinated polymer
could also be used. In yet another embodiment, a fluorinated
polymer is also used as the sacrificial layer during device
fabrication. It is well-suited for this purpose because it may be
easily removed with a suitable solvent and it can withstand the
high temperatures that are associated with device fabrication (e.g.
sputter deposition).
[0043] Accordingly, the invention, as defined in the claims, is not
limited to what is expressly described in the specification and
drawings.
e. REMARKS
[0044] The present invention provides a method for coating
electronic components with a high temperature stable and readily
applicable protective encapsulant. It provides simple coating
application and removal of corrosion resistant, substantially
hermetic encapsulation for rework of the coated module the
fluorinated polymer encapsulant of the present invention is an
improvement over conventional coatings such as silicon nitride.
Among other things, it provides long term environmental resistance,
thermal stability, and optical clarity even in harsh environments.
the coated module the fluorinated polymer encapsulant of the
present invention is an improvement over conventional coatings such
as silicon nitride. Among other things, it provides long term
environmental resistance, thermal stability, and optical clarity
even in harsh environments.
* * * * *