U.S. patent application number 11/443754 was filed with the patent office on 2006-10-05 for overmolded lens on leadframe and method for overmolding lens on lead frame.
This patent application is currently assigned to Barnes Group Inc.. Invention is credited to Timothy A. Butkus, Edward M. Flaherty.
Application Number | 20060220049 11/443754 |
Document ID | / |
Family ID | 34830546 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060220049 |
Kind Code |
A1 |
Flaherty; Edward M. ; et
al. |
October 5, 2006 |
Overmolded lens on leadframe and method for overmolding lens on
lead frame
Abstract
A light emitting diode (LED) assembly including an LED, an
optically transmissive cover and a base for supporting the LED. The
optically transmissive cover encapsulates the LED and includes a
stiffener for reinforcing a base portion of the cover. The base
includes electrical leads extending therefrom that are electrically
connected to the LED. To make the cover, at least one support frame
is formed in a strip of substantially rigid material. The at least
one support frame is connected to a processing portion of the
strip. At least one lens is overmolded on the at least one support
frame that is connected to the processing portion. The overmolded
support frame is removed from the processing portion of the
strip.
Inventors: |
Flaherty; Edward M.; (New
Milford, CT) ; Butkus; Timothy A.; (Naugatuck,
CT) |
Correspondence
Address: |
FAY, SHARPE, FAGAN, MINNICH & MCKEE, LLP
1100 SUPERIOR AVENUE, SEVENTH FLOOR
CLEVELAND
OH
44114
US
|
Assignee: |
Barnes Group Inc.
|
Family ID: |
34830546 |
Appl. No.: |
11/443754 |
Filed: |
May 31, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10852877 |
May 25, 2004 |
7081644 |
|
|
11443754 |
May 31, 2006 |
|
|
|
60542561 |
Feb 6, 2004 |
|
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|
Current U.S.
Class: |
257/98 ;
257/E33.059; 257/E33.073 |
Current CPC
Class: |
H01L 33/58 20130101;
H01L 2224/49171 20130101; H01L 33/483 20130101 |
Class at
Publication: |
257/098 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Claims
1. A leadframe strip assembly for LED lens assemblies having lenses
and rigid support frames for structurally supporting said lenses,
comprising: a leadframe strip; at least one support frame disposed
within said leadframe strip; and at least one optically
transmissive lens formed of a relatively soft material overmolded
onto said at least one support frame for structurally supporting
said lens.
2. The leadframe strip assembly of claim 1 wherein said at least
one optically transmissive lens includes a dome portion and a base
portion, said base portion being overmolded on said at least one
support frame.
3. The leadframe strip assembly of claim 2 wherein said at least
one optically transmissive lens includes a dome portion and an
annular portion, said at least one support frame is annularly
shaped and disposed with said annular base portion.
4. The leadframe strip assembly of claim 2 wherein said at least
one support frame is one of (i) positioned adjacent said base
portion and (ii) encased by said base portion.
5. The leadframe strip assembly of claim 4 wherein said at least
one support frame is entirely encased with said base portion of
said at least one optically transmissive lens.
6. The leadframe strip assembly of claim 2 wherein said at least
one support frame is a ring annularly disposed with said base
portion.
7. The leadframe strip assembly of claim 2 wherein said at least
one optically transmissive lens is formed from a liquid silicone
rubber.
8. The leadframe strip assembly of claim 2 wherein said base
portion extends radially outwardly from said dome portion.
9. The leadframe strip assembly of claim 8 wherein said at least
one support frame is annularly received around said dome portion
and against an upper surface of said radially extending base
portion.
10. The leadframe strip assembly of claim 8 wherein said at least
one support frame is encapsulated entirely by said radially
extending base portion.
11. The leadframe strip assembly of claim 1 wherein said at least
one support frame includes two support frames each having an
optically transmissive lens overmolded thereon, said two support
frames connected to a processing portion of said leadframe strip by
supports.
12. The leadframe strip assembly of claim 11 wherein said
processing portion includes recesses for aligning with pins during
overmolding of said support frames.
13. The leadframe strip assembly of claim 1 wherein said leadframe
strip and said at least one support frame are stainless steel.
14. The leadframe strip assembly of claim 1 wherein said leadframe
strip and said at least one support frame are integrally formed of
a material that is relatively harder than said at least one
optically transmissive lens for providing dimensional stability to
said at least one optically transmissive cover.
15. A leadframe strip assembly for use in manufacturing LED lens
assemblies, comprising: a leadframe strip including a plurality of
support frames; and a plurality of lens covers having a base
portion and a dome portion integrally formed with said base
portion, said dome portion being at least partially optically
transmissive to allow light from an LED to pass therethrough, each
of said plurality of support frames reinforcing said base portion
of a corresponding one of said plurality of lens covers for
providing structural integrally to said corresponding one of said
plurality of lens covers.
16. The leadframe strip assembly of claim 15 wherein each of said
plurality of lens covers is formed of a relatively soft material
and each of said plurality of support frames is formed of a
material that is relatively harder than that of said plurality of
lens covers for providing dimensional stability.
17. The leadframe strip assembly of claim 16 wherein said
relatively soft material is silicone and said material that is
relatively harder is stainless steel.
18. The leadframe assembly of claim 15 wherein said dome portion is
formed of a substantially transparent material.
19. A method of manufacturing a plurality of LED lens assemblies on
a leadframe strip for use in an LED assembly, comprising the steps
of: providing a strip of rigid material; forming at least one
support frame in said strip that is connected to a processing
portion of said strip; overmolding at least one lens on said at
least one support frame that is connected to said processing
portion; and removing the overmolded support frame from said
processing portion of said strip.
20. The method of claim 19 further including: using said overmolded
support frame to encapsulate an LED.
21. The method of claim 19 wherein said steps of removing and using
said overmolded support frame includes the sub-steps of: using a
vacuum pick and place to remove said overmolded support frame from
said processing portion of said strip; and using said vacuum pick
and place to encapsulate said LED with the removed overmolded
support frame.
Description
[0001] This application claims priority from U.S. patent
application Ser. No. 10/852,877 filed on May 25, 2004 and is
expressly incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to light emitting diode (LED)
technology and, more particularly, to a lens cover for an LED. The
present invention finds particular application as a reinforced lens
cover and a method of manufacturing said reinforced lens cover and
will be described with particular reference thereto. However, it is
to be appreciated that the present invention may relate to other
similar environments and applications.
[0004] 2. Discussion of the Art
[0005] An LED assembly generally includes a base, an LED supported
by the base and a cover over the LED. The LED is typically a piece
of semiconductor material having wire leads extending therefrom for
delivering current to the LED. The cover is typically a
substantially transparent material having a dome shape and acting
as a lens for light emitted from the LED. When assembled, the cover
and the base serve to encapsulate the LED and protect it from
adverse environmental effects. The optically transmissive cover
additionally serves to enhance light emission from the LED and
control external radiation patterns from the LED.
[0006] Several design aspects are involved in providing a suitable
cover for an LED. The cover should be sufficiently rigid to provide
a structurally sound member. Moreover, the cover should be at least
partially substantially transparent and minimize the amount of
light attenuation so as to not adversely affect the spectrum of
light which is emitted by the LED, particularly as the cover ages.
Heretofore, these design aspects often competed with one another,
i.e., an improvement in one of the aspects often corresponded to a
weakening in another of the aspects.
[0007] LED covers that attempted to balance the design aspects were
often difficult to manufacture. For example, one type of
conventional cover is formed in two parts. The two-part cover
typically includes a hard outer shell and a soft resilient inner
shell, often formed of silicone, defining a space therein for the
LED substrate. The hard outer shell of the two part cover enables
it to be structurally sound while the soft inner shell reduces the
likelihood that the LED substrate will be damaged. One drawback of
the two-part cover is that the hard outer shell often has low heat
characteristics. Thus, there is a need for an LED cover that
balances the design aspects discussed above while being relatively
easy to manufacture.
SUMMARY OF THE INVENTION
[0008] The present invention provides a new and improved lens
assembly that overcomes the foregoing difficulties and others and
provides the aforementioned and other advantageous features. More
particularly, in accordance with one aspect of the invention, a
lens cover for a light emitting diode is provided. In accordance
with this aspect of the invention, the lens cover includes a base
portion, a dome portion and a support frame reinforcing the base
portion for providing structural integrity to the lens cover.
[0009] In accordance with another aspect of the invention, a
leadframe strip assembly is provided for LED lens assemblies having
lenses and rigid support frames for structurally supporting said
lenses. More particularly, in accordance with this aspect of the
invention, the leadframe strip assembly includes a leadframe strip
and at least one support frame disposed within the leadframe strip.
At least one lens is overmolded onto the at least one support
frame.
[0010] In accordance with still another aspect of the invention, a
light emitting diode (LED) assembly is provided. More particularly,
in accordance with this aspect of the invention, the LED assembly
includes an LED, an optically transmissive cover and a base for
supporting the LED. The optically transmissive cover encapsulates
the LED and includes a stiffener for reinforcing a base portion of
the cover. The base has electrical leads extending therefrom that
are electrically connected to the LED.
[0011] In accordance with still yet another aspect of the
invention, a method of manufacturing an LED cover assembly is
provided. More particularly, in accordance with this aspect of the
invention, a strip of substantially rigid material is provided. At
least one support frame is formed in the strip that is connected to
a processing portion of the strip. At least one lens is overmolded
on the at least one support frame that is connected to the
processing portion. The overmolded support frame is removed from
the processing portion of the strip.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention may take form in various components and
arrangements of components and in various steps and arrangements of
steps. The drawings are only for purposes of illustrating one or
more preferred embodiments and are not to be construed as limiting
the invention.
[0013] FIG. 1 is a perspective view of a lens assembly having a
dome extending from a base and a support frame annularly disposed
about the dome on the base in accordance with one embodiment of the
invention.
[0014] FIG. 2 is a cross-sectional view of the lens assembly taken
at line 2-2 of FIG. 1.
[0015] FIG. 3 is a cross-sectional view of a lens assembly having a
dome extending from a base and a support ring encased in the base
in accordance with another embodiment of the invention.
[0016] FIG. 4 is a perspective view of the support frame.
[0017] FIG. 5 is a partial schematic view of a roll of leadframe
material and apparatus (a metal punch and a lens mold) for forming
a plurality of lens assemblies in accordance with an embodiment of
the invention.
[0018] FIG. 6 is a partial perspective view of the roll of
leadframe material taken along the line 6-6 of FIG. 5 showing
support frames formed therein by the metal punch.
[0019] FIG. 7 is a partial plan view of the leadframe material
taken along the line 7-7 of FIG. 5 showing the leadframe material
in the lens mold.
[0020] FIG. 8 is a partial plan view of the leadframe material
taken along the line 8-8 of FIG. 5 showing lenses overmolded on the
support frames.
[0021] FIG. 9 is a partial perspective view of the overmolded
lenses on the support frames of the leadframe material of FIG.
8.
[0022] FIG. 10 is a light emitting diode (LED) assembly including
the lens assembly of FIG. 1.
[0023] FIG. 11 is a partial cross-sectional schematic view of a
vacuum pick and place apparatus for removing a single lens assembly
from the leadframe material and encapsulating an LED with the lens
assembly by placing the lens assembly on an LED base.
[0024] FIG. 12 is a partial cross-section schematic view of an
alternate apparatus for removing a single lens assembly from the
leadframe material and encapsulating an LED with the lens
assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0025] Referring now to the drawings wherein the showings are for
purposes of illustrating one or more preferred embodiments of the
invention only and not for purposes of limiting the same, FIG. 10
shows a light emitting diode (LED) assembly generally designated by
reference numeral 10 in accordance with one preferred embodiment.
The LED assembly generally includes an LED 12 supported on a base
14 and encapsulated by a cover or lens assembly 16. The cover 16 is
optically transmissive and/or at least partially substantially
transparent for allowing light emitted by the LED to pass
therethrough. As will be discussed in more detail below, the cover
16 includes a stiffener 18, also referred to herein as a support
frame, that provides structural rigidity to the cover 16.
[0026] The base 14 includes electrical leads 20 extending therefrom
that are electrically connected to the LED 12 for providing an
electrical current thereto. More specifically, leads 20 extend
through a body 22 of the base and are electrically connected to the
LED 12 by bond wires 24. When an appropriate electrical current is
supplied through the leads 20 and the bond wires 24, the LED 12
emits a light that passes through the cover 16. The cover 16 serves
to protect the LED 12 from the environment in which the LED is
deployed.
[0027] With additional reference to FIGS. 1 and 2, the cover 16 is
formed of a soft and/or resilient material that forms an annular
base portion 30 and a dome portion 32 extending from the base
portion. The dome portion 32 acts as a lens for collimating light
from the LED 12. Within the portions 30,32, the cover 16 defines an
LED cavity 34 for receiving the LED 12. The support frame 18 is
disposed with the base portion 30 and reinforces the base portion
30 to provide structural integrity to the cover 16. In particular,
the support frame 18 has the benefit of adding dimensional
stability to the cover 16. Moreover, as will be described in more
detail below, the support frame 18 allows the cover 16 to be more
easily handled, particularly when the cover 16 is assembled as part
of an LED assembly. In the illustrated embodiment, the support
frame 18 is a ring positioned adjacent the base portion 30. More
specifically, as will be described in more detail below, the base
portion 30 is overmolded onto the support frame 18 such that the
support frame is oriented on a side 36 of the base portion 30
adjacent the dome portion 32. In the preferred embodiments
described herein, the cover 16 is formed of a silicone or like
material and the support frame 18 is formed of a stainless steel or
similar material.
[0028] With reference to FIG. 3, an alternate cover 16' is shown
including a base portion 30' and a dome portion 32' extending from
the base portion. The cover 16' is optionally used in place of the
cover 16 in the LED assembly 10. Like the dome portion 32, the dome
portion 32' acts as a lens for collimating light from the LED. An
LED cavity 34' is defined in the cover 16' to receive the LED. The
cover 16' includes the support frame 18 disposed with the base
portion 30' for reinforcing the base portion to provide structural
integrity to the cover 16'. However, the support frame 18 is
positioned within the base portion 30', i.e., the support frame 18
is encased in or by the base portion 30'. Like the cover 16, the
base portion 30' is overmolded onto the support frame 18. However,
the support frame 18 is oriented within or imbedded in the base
portion 30'. In most other respects, the cover 16' is like the
cover 16.
[0029] With reference to FIG. 4, the support frame 18 is shown as a
flat ring or washer-like structure. In the illustrated embodiments
discussed herein, the support frame 18 is a single component that
is annular-shaped and generally matches the shape of the base
portion (30 or 30') of the lens cover (16 or 16'). However, it is
to be understood by those skilled in the art that the base portion
could have an alternate shape (oval, rectangular, etc.) and the
frame 18 could be modified to match or complement such an alternate
shape. In addition, it also to be understood by those skilled in
the art that the support frame 18 could be formed of more than a
single piece and/or could have a shape that varies from that of the
base portion. The purpose of the support frame 18 is to provide
rigidity to the base portion which will improve the structural
integrity of the cover.
[0030] With reference to FIG. 5, a roll 38 of leadframe material 40
that is relatively rigid is used to form a plurality of support
frames 18 which are overmolded with a lens material to form a
plurality of covers. More particularly, the roll 38 of leadframe
material 40, which in the preferred embodiments is stainless steel
but can alternatively be formed of another metal, a plastic or
other suitable structural material or substrate, is unrolled and
fed through a metal punch apparatus 42 which functions to shear or
cut the leadframe material 40 into the partial leadframe strip 44
shown in FIG. 6. Specifically, the punch apparatus 42 removes
leadframe material from inner cavities or areas 46 to form inner
diameters of the plurality of support frames 18. Around each of the
support frames 18, the punch apparatus 42 removes leadframe
material from outer cavities or areas 48 to form outer diameters of
the support frames 18 and a plurality of supports 50. The supports
50 connect the support frames 18 to a remaining or processing
portion 52 of the leadframe material 40 and maintain the position
and orientation of the support frames 18 as the leadframe material
40 is further processed. The punch apparatus 42 also forms a
plurality of pin or guide holes 54, also referred to herein as
recesses, in the processing portion 52 which can be used for
holding and/or positioning the unrolled portion of the leadframe
material 40 during further processing thereof. In a preferred
embodiment, the leadframe material 40 can vary in type, thickness
and width pending specific applications.
[0031] Next, the punched leadframe material 40 is fed or delivered
to a lens mold apparatus 56. Although the leadframe material 40 is
shown as being directly fed from the punch apparatus 42 to the lens
mold apparatus 56, the punched material 40 could be collected and
later unrolled for feeding into the lens mold apparatus 56. With
additional reference to FIG. 7, the lens molding apparatus 56
closes on the unrolled leadframe material 40 and forms a molding
cavity 58 about each support frame 18. In the preferred embodiment,
as shown in FIG. 5, molding cavities 58 are formed around support
frames 18 in the lens molding apparatus 56. Each of the mold
cavities 58 includes a base cavity portion for forming the base
portion 30 and a dome cavity portion for forming the dome portion
32.
[0032] Through a sprue (not shown) connected to a runner section 60
that conveys material with the cavities 58, silicone material, also
referred to herein as a liquid silicone rubber (LSR), is delivered
to the molding cavities 58 and is overmolded onto or with the
support frames 18. In the illustrated embodiment, the molding
cavities 58 are positioned relative to the support frames 18 such
that the base cavity portions are adjacent the support frames 18
and overmolding causes the silicone base portion to form adjacent
the support frames 18. In an alternate embodiment, the molding
cavities are positioned relative to the support frames 18 such that
the base cavity portions are positioned around the support frames
18 and overmolding causes the silicone base portion to encase the
support frames 18 such that the support frames 18 become embedded
in their respective base portions 30. The holes 54 in the
processing portion 52 receive pins 62 of the lens mold apparatus 56
for purposes of aligning the support frames 18 with and relative to
the mold cavities 58.
[0033] After delivery, the silicone material is allowed to cure to
form the cover 16 including base portion 30 adjacent the support
frame 18 and dome portion 32 extending through the support frame 18
from the base portion 30. After sufficient curing time, the
overmolded support frames 18 and their corresponding processing
portion 52 of leadframe material 40 are removed from the lens mold
apparatus 56. With reference to FIGS. 8 and 9, the support frames
18 are overmolded with covers 16 that are connected to one another
by cured silicone material 64,66 (not shown in FIG. 9) that is
removed from the runner section 60 and the sprue. The overmolded
support frames 18 are still connected to the processing portion 52
by the supports 50. The covers or lenses 16 each include the base
portion 30 formed adjacent and below the support frames 18 and the
dome portion 32 protruding through the support frames 18.
[0034] The unrolled and overmolded leadframe material 40 can
optionally be cut into strips 44 of various lengths for purposes of
packing and/or moving thereof. Strips 44 enable sections of the
leadframe material to be stacked or otherwise maneuvered. After
separation into strips or as a continuation of the processing shown
in FIG. 5, each overmolded support frame 18 can be removed from its
processing portion 52. In accordance with one embodiment, with
reference to FIG. 11, a vacuum pick and place apparatus 70 is used
to remove each overmolded support frame 18 with its cover 16. As
illustrated, the apparatus 70 separates each cover 16 and its
support frame 18 from the supports 50. While holding the cover and
frame 16,18, the apparatus 70 then rotates the cover and frame to
an appropriate position and places the cover 16 on a base 14 with
an LED 12 to encapsulate the LED 12. The apparatus 70 can include
appropriate gripping or positioning members 72 to hold the
processing portion 52 in place while each cover 16 and its frame 18
are removed.
[0035] In accordance with another embodiment, with reference to
FIG. 12, an apparatus 70' can be used in place of the apparatus 70.
The apparatus 70' is a press-type device that uses a single motion
to sever the support frame 18 from its supports 50 and place the
cover 16 with its severed support frame 18 onto base 14 to
encapsulate LED 12. Pins 72' can be used in the recesses 54 to
position the support frame 18 relative to the apparatus 70'. With a
downward stroke, the apparatus 70' removes each cover 16 from the
strip 44 and places it on a base 14.
[0036] The invention has been described with reference to the
preferred embodiment(s). Obviously, modifications and alterations
will occur to others upon reading and understanding the preceding
detailed description. It is intended that the invention be
construed as including all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *