Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD OF PRODUCING A LAMP
Field of the Invention
The present invention relates to a method of producing a lamp, particularly an
LED lamp,
and a lead frame for use in the lamp.
S Summary of the Invention
In accordance with the present invention, there is provided a method of
producing a lamp,
including mounting light emitting junctions on a support structure such that
the junctions
adopt a three-dimensional array.
Preferably, the method further includes locating the junctions in respective
recesses formed
in the support structure, the recesses functioning as an optical guide for
controlling a
direction of light output from the associated junction.
Preferably, the support structure includes a plurality of conductors and the
method further
includes forming the conductors in a curved configuration, which is preferably
a part
spherical configuration.
1 S Preferably, the conductors are provided in the form of a lead frame.
Preferably, the method further includes moving the lead frame relative to a
forming station
and engaging a punch and die, from opposed sides of the lead frame, to form
the recesses.
The recesses may be formed in a single action or, alternatively, formed
sequentially, with
the punch and die being moved relative to the lead frame after each recess
forming action
so that the punch and die are appropriately positioned for a subsequent recess
forming
action.
Preferably, the lead frame is supported on a Garner and the method includes
moving the
Garner so as to present each recess to a mounting station whereat the
junctions are mounted
to the conductors. The carrier is preferably rotatable about first and second
orthogonal
axes to align the respective recess with the mounting station and the
junctions are mounted
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in the respective recesses by advancing the junctions and associated
conductors relative to
each other along a third axis, which is preferably orthogonal to the first and
second axes.
Each junction is preferably electrically connected to two of the conductors
via intermediate
conductors. The intermediate conductors may be connected to allow for
independent
control of at least two of the junctions, by controlling electric current
through the
associated conductors, to which each junction is connected. The junctions may
further be
electrically coupled to the conductors in groups which are separately
controllable.
The method preferably includes application of a common phosphor over at least
two
adjacent junctions and, more preferably, encapsulation of the support
structure and
junctions, in a globe portion.
In another aspect, there is provided a lead frame including a plurality of
conductors formed
in a curved configuration, for supporting light emitting junctions in a three-
dimensional
array. The lead frame preferably includes recesses for receipt of a respective
one of the
junctions.
In another aspect, there is provided a lamp formed in accordance with the
above-described
method.
In yet another aspect, there is provided a method of operating the above
described lamp,
formed with conductors and light emitting junctions electrically connected
therebetween,
including controlling electrical current through individual ones of the
conductors so as to
independently control light output from the junctions coupled thereto.
Brief Description of the Drawings
The invention will be described in more detail with reference to the drawings
in which:
Figure 1 is a side-view of an LED lamp;
Figure 2 is a plan-view of the lamp of Figure 1;
Figure 3 is a circuit diagram for the lamp of Figures 1 and 2;
Figure 4 is a diagrammatic cross-sectional view of a second LED lamp;
Figure 5 is a circuit diagram of the lamp of Figure 4;
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Figure 6 is a cross-sectional view of the lamp of Figure 4;
Figure 7 is a plan view of the lamp of Figure 4;
Figure 8 is a representation of an illumination pattern of the lamp of Figures
4 to 7;
Figure 9 is a plan view of a third lamp;
Figure 10 is a circuit diagram for the lamp of Figure 9;
Figure 11 is a front view of the lamp of Figure 9;
Figure 12 is a side view of the lamp of Figure 9;
Figure 13 is a side view of a lens for fitting on the lamp of Figure 9;
Figure 14 is a cross-sectional view taken along the line X-X shown in Figure
11;
Figure 1 S is a cross-sectional view taken along the line Y-Y shown in Figure
12;
Figure 16 is a representation of the illumination pattern produced by the lamp
of Figures 9
to 12;
Figure 17 is a schematic flow chart illustrating steps for producing a lamp;
Figure 18 is a diagrammatic perspective view of a lead frame arranged for a
recess forming
operation;
Figure 19 is a perspective view of the lead frame on a carrier;
Figure 20 is a cross-sectional view of the lead frame;
Figure 21 a) is a plan view of the lead frame with junctions and intermediate
conductors
attached;,
Figure 21b) is a cross-sectional view of the lead frame, taken along the line
A-A, shown in
Figure 21 a).
Figure 22 is a plan view of another lead frame with junctions attached;
Figure 23 is a plan view of an alternative lead frame construction;
Figure 24 is a perspective view of a lamp, formed from the lead frame of
Figure 23; and
Figure 25 is a perspective view of another lamp.
Detailed Description of a Preferred Embodiment
The lamp 1, as shown in Figure 1, includes a globe portion 2 with a
cylindrical base 3 and
a parabolic end 4, configured to enhance illumination output in an axial
direction of the
lamp. The lamp also includes first and second terminals, which are preferably
in the form
of conductors 5,6 which are embedded within the globe portion 2. The terminal
5 has a
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support platform 7 to which is mounted an integrated circuit wafer 8. In the
example
given, the wafer includes two junctions which are arranged substantially
adjacent to each
other so that a common layer of fluorescent material, such as a phosphor
layer, may be
applied over both junctions. Intermediate conductors 9 to 12 electrically
couple the
junctions to the respective terminals 5,6 so that the LED junctions 14,15 are
arranged in
reverse polarity, as indicated in the circuit diagram Figure 3. A resistive
element 16 is
provided between a further conductor 13 (connecting the intermediate
conductors 11 and
12) and the terminal 5.
The conductors 5,6, intermediate conductors 9 to 13, and wafer 8 are all
embedded within
the globe portion 2 so that the lamp is presented as a robust unitary
structure. The reverse
polarity of the junctions allows the lamp to be connected to a power source
without
concern for polarity, as compared to the case with a conventional LED
arrangement. The
use of a single phosphor layer, common to each of the junctions, also
simplifies
manufacture and provides an aesthetic advantage in that the light from either
junction is
perceived to originate from a single source.
In a preferred form of the LED lamp, the following specifications may apply:
NOMINAL SIZE - 9.Smm diameter
LIGHT COLOUR - WHITE
GLOBE COLOUR - WATER CLEAR
LIGHT INTENSITY - SUPERBRIGHT
TYPICAL LIGHT OUTPUT > SOOmCd @ 20mA
GUARANTEED LIFE - 30,000 HOURS
FOCUS - HALF ANGLE 15 typ.
BASE STYLE - INTERCHANGEABLE WITH WEDGE TYPE LAMPS
LEAD DIMENSIONS - 6mm nom. OUTSIDE BASE WEDGE
SUPPLY VOLTAGE - 12VOLTS nom. {>11.5<14 volts AC or
DC~
FORWARD CURRENT - 20 +8/-3 mA @ l2Volts
FORWARD VOLTAGE - 3.6 min(typ) 4.Omax. @ 20mA
REVERSE VOLTAGE - SVolts min.
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POWER DISSIPATION - LED JUNCTIONS 120Mw
RESISTOR 170mW
REVERSE CURRENT - 50 x 10-3 mA max. @ 5V
INTERNAL RESISTOR - 430 ohms nom.
It should, however, be appreciated that the size configuration and operating
parameters of
any of the component parts of the lamp may vary, as required and the number of
LED
junctions may also be increased to suit illumination needs.
A second lamp 20 is now described with reference to Figures 4 to 8. The lamp
20 is
generally similar in construction to that of Figures 1 to 3, in sofar as first
and second
terminals 21 and 22 are provided, in the form of conductors 23,24 embedded in
a globe
portion 25, together with additional conductors 26,27. Each of the conductors
23,26 and
27 have a respective recess 28, to provide support structure for receiving an
associated
junction, indicated by reference numerals 29,30,31. The junctions are covered
by a
common layer of phosphor 35 and are electrically coupled between each
respective
conductors 23,26,27 to which they are mounted, and the adjacent conductor via
intermediate conductors 32,33,34. In the example shown, the junctions are
serially
connected, as represented by the circuit diagram of Figure 5.
All of the conductors 23, 24,26,27 are preferably formed in a two dimensional
lead frame
structure 40 shown in Figure 6, to allow ease of manufacture and reliability
in directly
positioning the junctions 29,30,31 before application of the phosphor layer 35
within and
before application of the globe portion 25. As can be seen from both Figures 6
and 7, the
junctions 29,30,31 are arranged in a generally linear array, with the
conductors 23,27
projecting above the conductor 26 so that the overall illumination generated
by the
junctions will be somewhat enhanced on-axis, as represented in Figure 8 by
curve A.
The lamp 20 may also be provided with a lens 41 which is fitted to the globe
portion 25
and shaped so as to modify the light generated by the lamp to produce, for
example, the
illumination pattern represented by curve B in Figure 8, whereby the output
illumination is
somewhat more evenly distributed.
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Turning now to Figures 9 to 16, a third lamp 50 is illustrated. Again, the
lamp 50 is in
general similar to the previous lamp construction insofar as a plurality of
conductors
51,52,53 and 54 are embedded within a unitary globe portion 55 and have light
emitting
junctions 56 mounted in respective recesses 57 and covered by a common layer
of
fluorescent material 59. Each junction is again electrically coupled to the
respective
conductor to which it is mounted and an adjacent conductor via intermediate
conductors 58
so as to form the circuit illustrated in Figure 10. Each of the conductors 51
to 54, in this
instance, however, carrying three junctions 56.
The conductors 51 to 54 are curved within the globe portion 55 so as to
support the
junctions on an imaginary curved surface such as a spheroid and, in that
manner, the
illumination generated by the lamp 50 will have an appearance of emanating
from a small,
generally spheroid point like source. A lens 60 may also be provided for
modifying the
output of the junctions to produce a more even distribution pattern such as
represented by
curve C in Figure 16, which is the illumination output observed from a plan
view of the
lamp 50, i.e. when the lamp is seen from the same direction as viewed in
Figure 9.
In addition to modifying the light output by using the lens 60, it is also
possible to arrange
the conductors in any desired configuration and the construction of the
recesses 57 may
also be used to assist in controlling the directional output of the light
emitted from the
various junctions. In particular, the configuration of each recess may be such
that for
example, the recess side walls act as optical guides to control the direction
and/or angle of
divergence of light emitted from each junction.
More specifically, the shape of each recess and its effect on the light output
from the
junctions will now be described in more detail with reference to Figures 14
and 15, which
show cross-sectional views of the relevant conductors taken along the lines X-
X and Y-Y
shown in Figures 11 and 12 respectively.
The recesses 57 containing the LED junctions are positioned and shaped in the
conductors
51,52,53 so that the beams of light emerging from the recesses may be combined
in free
space outside the lamp 50 in predictable patterns determined by the radius of
the imaginary
part spherical surface designated 'R', the distance from the LED junction in
the recess to
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the intersection of the imaginary extension of the sides of a recess -
designated 'r' and the
angle 'A' between the centre line 61 of the lamp 50 and a centre line 62
passing through the
perpendicular to any other LED junction.
The radius 'R' of the imaginary spherical surface is the distance from the
intersection of
those centre lines to the LED junction within the recess. The angle between
the sides of a
recess determines the value of the 'r'.
In the limiting case where 'r' is equal to or greater than 'R", the light from
each LED
junction will be shaped by the recesses into beams which do not cross,
regardless of the
value of angle 'A'. For all values of 'r' less than 'R' it will be possible to
have the light
beam from each LED junction coincide with the edges of the light beams from
adjacent
LED junctions. The exact positioning in this instance will be determined by
the ratio R/r
and the value of angle 'A'.
As may be appreciated, the above described lamps allow considerable scope for
obtaining
a light source using junction diodes, with a predetermined one of a variety of
output
illumination patterns whilst maintaining a generally simple construction. A
particular
advantage is that the various junctions are of small size and may be
configured to produce
a light output which may be perceived by the naked eye to be emanating from a
single
point source of light.
A method of producing a lamp is now described, with reference to Figures 17 to
24. The
method includes three main stages: stage 100 is the formation of a suitable
lead frame;
stage 101 is the attachment of junctions to the lead frame; and stage 102 is
the final
packaging stage.
Stage 100 includes provision of a flat lead frame, at step 103, formation of
conductors of
the lead frame into a part spherical surface, at step 104, and the formation
of recesses in the
conductors, at step 105, followed by surface treatment step 106.
Figure 18 shows a lead frame 110, between steps 104 and 105. The lead frame
110 is
provided in a generally elongate strip 111, divided into sections 112, which
will ultimately
be separated to form individual lamps. Each section 112 includes a plurality
of conductors
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113, 114, 115 formed into a curved configuration which is preferably part
spherical. The
conductors may be formed in that configuration by any suitable process such as
by
inserting the strip 111 in a press or the like.
In order to form the recesses, the part spherical portion of the lead frame is
fitted over a
correspondingly shaped tool 116, at a forming station, where a punch (not
shown) is
engaged with the conductors 113, 114, 115, from an opposite side of the lead
frame to that
of the die, to form recesses in the conductors by action of the punch
deforming the
conductors into an associated die 117 provided in the tool 116. The recesses
may be
formed sequentially and for that purpose, the tool is preferably rotatably
movable relative
to the lead frame so that the die can be rotated to any desired position where
a recess is
required. In that manner, a single punch, which is rotated in unison, and die
117 can be
used to form all of the recesses in any desired array. Alternatively, the tool
116 may have
a predefined array of die 117 and the punch configured appropriately so that
all of the
recesses are formed in a single action. The particular positioning and
configuration of~the
recesses can be selected to optimise output, as required, since the recesses
act as optical
guides, as discussed above specifically in relation to Figures 9 to 16, to
define the
directional output while the number of recesses will determine the maximum
output
intensity.
In any event, the lead frame 110, can be mounted on a carrier 119, as shown in
Figure 19,
for stage 101, where light emitting junctions are mounted in the recesses 120.
The Garner
119 is itself rotatable on a shaft 121, for pivotal movement about an x-axis,
and a shaft
122, for pivotal movement about a y-axis. As such, the lead frame can be
positioned at a
mounting station (not shown) and rotated about the x,y axes relative to the
mounting
station in order for each one of the recesses 120 to be sequentially presented
for receipt of
an associated junction. Figure 20 shows a cross-section of one of the stations
112 and, in
particular, the part spherical configuration of conductor 114. A curve 123
represents the
possible path of spherical translation of the conductor 114 which is
achievable by rotating
the lead frame 110 about axes 121,122. Line 124 represents an equivalent
rotation of the
tool 116 away from the z-axis, which in turn defines the operating angle 125
within which
recesses 120 may be formed.
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When each of the recesses is appropriately presented at the mounting station,
the
associated light emitting device or die, referred to for simplicity as
junction 130, as shown
in Figure 21, is inserted into the recess along a third axis, which is
preferably in a z-axis
direction, and bonded in place in accordance with step 107 of stage 101 of
processing. At
S that time, or subsequent thereto, intermediate conductors 131 are attached
at step 108 to
electrically connect the junctions to adjacent conductors. The junctions shown
in Figure
21 are arranged in an electrically parallel configuration, however, the
positioning and
coupling of the junctions may be in any desired configuration, such as shown
in Figure 22,
where each junction is coupled to a common central conductor 114 and a
separate radially
arranged conductor 132 to allow the light intensity from each of the junctions
to be
separately controlled by independently controlling the power supplied to the
conductors.
Another possible configuration of recesses 120 is shown in Figure 23. In any
of the
configurations, various ones of the junctions can be electrically connected in
groups so that
the light intensity from each of the groups can be independently controlled.
Once the LED junctions have been mounted in place and the intermediate
conductors
connected, a phosphor is applied over the junctions at processing step 109 of
stage 101.
The phosphor is preferably applied to at least two adjacent LED junctions.
The lead frame 110 is then transferred to a final stage 102 of processing to
form the lamp
140 shown in Figure 24. Stage 102 includes separating the sections 112,
removing excess
lead frame material and either compression moulding, at step 135 or epoxy
moulding, at
step 136, a globe portion 137 (see Figure 24) about the conductors 112, 114,
115. Free
ends of the conductors may then be bent into terminals or pins 138, to be
inserted in an
associated through hole of a typical printed circuit board (PCB)or the like.
The resultant
lamp 140 may then be tested at step 139 and packaged, if required.
Another finished lamp 150 is shown in Figure 25, with an additional moulded
body 151
formed beneath the globe portion 137. In this instance, the conductors within
the globe
portion have not been shown for simplicity, however, the conductors may have a
configuration similar to that shown in Figure 22, albeit that more junctions
and associated
recesses and conductors are provided. Specifically, 18 separately wired
junctions are
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provided, with 18 associated pins 138 and a further pin 152, for providing
electric current
to a common conductor within the globe portion 137. As such, 18 different
circuits are
formed within the lamp 150 and these can be individually addressed and
controlled via the
pins 138, which are again adapted to fit into PCB, or the like.
S As may be appreciated then, the invention provides a method for producing an
LED lamp
which optimises output of the LED junctions by positioning the junctions in a
three-
dimensional array and utilising recesses for optical guides. Further, the
construction
allows different output of individual junctions or groups of junctions to be
independently
controlled to vary the intensity of emitted light. Lastly, it is again
mentioned that the
three-dimensional array of the junctions and the configuration of the curved
conductors
themselves allow for the light from the lamp to have more of an appearance of
emanating
from a single point or small spherical source, which may be considered an
advantage over
conventional discrete junction light emitting junction devices.
The above method and LED lamps have been described by way of non-limiting
example
only, and many modifications and variations may be made thereto without
departing from
the spirit and scope of the invention as hereinbefore described.
