Note: Descriptions are shown in the official language in which they were submitted.
1199~
METHOD AND APPARATUS FOR MOUNTING MULTILEAD
CO~PONENTS ON A CIRCUIT BOARD
Technical Field
The present invention relates to the mass
production of circuit boards, and more particularly to a
method and an apparatus for simultaneously mounting one or
a plurality of multilead components on circuit boards.
Background of the Invention
~he production of electrical and electronic
circuit boards often requires the mounting of several
multilead electrical components on each board. Usually,
such mounting techniques involve manual insertion of the
leads of the multilead components, one component at a time,
in corresponding holes of a circuit board. Clearly, such
techniques result in small throughput, are time consuming,
and labor intensive. Moreover, with electrical component
packages oecoming smaller in size, and with the number of
leads on each package substantially increasing to achieve
higher packaging densities, the problem of operator fatigue
becomes a major one.
Several attempts were made to avoid the foregoing
hindrances of manual insertion of a multilead component by
resorting to automation. In the area of automatically
mounting a multilead component or an I.C. package on a
printed wiring board (PWB), the emphasis has been on
achieving a high degree of accuracy in the positioning of
the component held by a robotic hand or an automatic
manipulator with respect to the holes of the PWB. Such
high accuracies and close tolerances in the design and
control of the robotic hand result in a complex and
expensive automatic apparatus for accurately positioning
the leads or terminals of the component with respect to
their corresponding holes. Such an automatic apparatus is
capable of mounting or inserting only one multilead
component at a time into the PWB r Furthermore, the
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39'~
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foregoing strict hand positioning requirements do not and
cannot compensate for any dimensional deviations existing
between the outer housing of the component and its leads.
A technique for automatically mounting a multi
lead component on a board is known. Such a known technique
comprises the steps o~ placing the multilead component on
the board such that each one of its leads is proximate to
its corresponding hole in the board, and vibrating the
board to cause the leads to fall into the holes. This
technique clearly overcomes the above-mentioned strict
design requirements on the robotic hand, as well as the
component dimensional deviations problem. Although this
technique operates satisfactorily for its intended
purpose, it is capable of mounting only one multilead
component at a time on the board.
Summary of the Invention
The foregoing problems are solved in accordance
with one illustrative embodiment of the present invention
wherein a method for simultaneously mounting a plurality
of multilead components on a board comprises the steps of
holding the plurality of components proximate to the
board, simultaneously placing ~he plurality of components
on the board such that each lead of each component is
proximate to its corresponding aperture in the board, and
imparting a vibratory motion to the board thereby inserting
each lead of the components into it corresponding aperture
in the board.
In a further embodiment of the invention, the
holding step comprises the steps of loading a releasable
template, having a plurality of openings substantially
matching the dimensions of the components, with the
plurality of components to be mounted; and positioning
the loaded releasable template proximate to the board in
a direction substantially parallel thereto. In another
embodiment of the invention, the holding step comprises the
:
1~9~
steps of positioning a releasable template, having a
plurality of openings substantially matching the dimensions
of the components, proximate to the board in a direction
substantially parallel thereto, and loading the openings of
the releasable template with corresponding components to be
mounted. In either one of these two embodiments, the
positioninq step may comprise the step of controlling a
programmable manipulator (e.g., a robotic arm) for holding
the releasable template at a preselected coordinate
lQ position with respect to the board.
In accordance with another illustrative
embodiment, the above-mentioned releasable template and
programmable robotic arm are used to mount a multilead
electrical component on a printed wiring board (PWB). The
method for achieving such a mounting comprises the steps of
holding the multilead electrical component in an opening of
the releasable template, holding the releasable template at
a preselected coordinate position with respect to the PWB
such that each lead of the component is proximate to its
corresponding aperture in the PWB, releasing the component
out of the opening of the template onto the PWB, and
vibrating the PWB in directions substantially parallel to
its plane thereby causing each lead of the multilead
electrical component to be inserted in its corresponding
aperture in the PWB.
One advantage of the present invention is the
ability to automatically mount a plurality of multilead
components on boards regardless of reasonable dimensional
deviations in the position of the outer housing of the
components relative to their leads.
Another advantage of the present invention is the
ability to simultaneously mount several types of multilead
components having diverse geometries on the same board
without requiring operator assistance.
A further advantage of the present invention is
the capability of mounting a plurality of multilead
components using a single programmable robotic arm.
A still further advantage of the present
invention is the ability to maximize circuit board
throughout by ~.inimizing the robotic arm motions.
These and other advantages of this invention will
appear more fully upon considera~ion of the illustrative
embodiments now to be described in detail in connection
with the accompanying drawings.
Brief Description of the Drawings
. _
FIG. l is a perspective view of a typical
multilead component to be mounted on a board using an
embodiment of the method and apparatus of the present
invention;
FIG. 2 is a perspective view of an apparatus in
accordance with one illustrative embodiment of the present
invention;
FIG. 3 is a flow chart representation of the
steps involved in the operation of the illustrative
embodiment of FIG. 2;
FIG. 4 is a perspective view of an apparatus in
accordance with another illustrative embodiment of the
present invention;
FIG. 5 is a flow chart representation of the
steps involved in the operation of the illustrative
embodiment of FIG. 4;
FIG. 6 illustrates a releasable template in
accordance with an embodiment of the present invention; and
FIG. 7 is a cross-sectional view along line 7-7
of the releasable template of FIG. 6.
Detailed Description~
Illustratively shown in FIG. l is a component lO
having a plurality of leads 11 arranged or aligned in
accordance with a pattern 12 on one side or surface 13 of
such component. The component lO, as shown, has an outer
oody housing 14 generally shaped as a parallelepiped.
However, the hereafter described inventive concepts are
also applicable to components having cylindrical, cubical
or any other outer body shape. Also, the leads 11 may be
1~99~
arranged in any type of pattern 12, such as circular~
rectangular, square, or other geometric configurations~
Moreover, the present inventive concepts and teachings are
applicable to the mounting of multilead components on
5 boards~ such multilead components containing electrical
devices, electronic circuits, other type of objects or
articles, or any combination thereof.
Shown in FIG. 2 is an apparatus for mounting
components in accordance with one embodiment of the present
invention. A board 20 having a plurality of holes or
apertures 21 arranged in various patterns, e.g., 24, is
mounted on a base 22 by means of a plurality of mounting
bodies 23. A plurality of multilead components of various
shapes 25, 2~, 27, 28 are to be mounted on board 20. The
leads of each one of the multilead components are to be
inserted in predetermined apertures, such as pattern 24, of
the board. The apertures 21 on the board 20 are arranged
in patterns corresponding to those of the leads of the
co~ponents 25 to 28 to be mounted thereon. As
schematically shown in FIG. 2, the board 20 is further
coupled to the base 22 by means of a mechanism 29 capable
of imparting a vibratory motion of controlled frequency and
amplitude to the board. One way of accomplishing the
vibratory motion of the board 20 is to use somewhat
compliant mounting bodies 23 attached to the board. One
such compliant coupling may be achieved by means of spring
mounted legs having one end thereof secured to the base 22
and the other end coupled to the board 20. Alternatively,
mounting bodies 23 may include suspension springs ~not
shown~ having one end coupled to the board 20 and the other
end secured to a fixed portion of the base 22.
Such vibratory motion, which is preferably in the
plane of the board 20, may be accomplished, for example, by
means of a motor 30 having an eccentrically mounted shaft
31 thereon, which is attached to the board. However, other
types of vibrating mechanisms, as well as vibratory motions
in a direction substantially perpendicular to the plane of
1~3t3~'Z'~
~ 6 -
the board, are also within the spirit and scope of the
present invention.
In order to simultaneously mount the components
25 to 28 on the board 20, they are all initially held
proximate to the surface of board 20. Next, these
components 25 to 28 are simultaneously placed on the
surface of the board 20 such that each component has its
leads proximate to a corresponding aperture 21 in the
board. The holding of the components 25 to 28 prior to
placing them on the board 20 is achieved by means of a
releasable template 32 having a plurality of openings 34 to
37 adapted to receive the outer bodies of components 25 to
28, respectively. The dimensions of each opening 34 to 37
of the template 32 are selected to substantially match the
outer dimensions of the components to be mounted. Also,
each opening 34 to 37 of the template 32 is located therein
to substantially match the position and orientation of its
corresponding component aperture pattern 24 on the board
20. Furthermore, each opening 34 to 37 of the template 32,
such as opening 35, may comprise a pair of retaining
protrusions or lips, e.g., 33, adapted to hold a
corresponding component therein. As shown, the releasable
template 32 comprises a central portion 38 releasably
coupled to two outer portions 39 and 40 along its two edges
41 and ~2. The perspective view of the apparatus of FIG. 2
shows only one of the retaining protrusions of openings 34,
35 and 37, the other protrusion of each opening being
opposite to the one shown. In other words, template
opening 35, for example, has one retaining protrusion or
lip 33 located in the template outer portion 40 and the
other retaining protrusion or lip located in the template
central portion 38. Further structural and operational
details of the "opening" and "clGsing" of a releasable
template in accordance with an embodiment of the invention
will be described in connection with FIGS. 6 and 7.
In operation of the illustrative embodiment of
FIG. 2, the releasable template 32 is closed and the
multilead components 25 to 28 are loaded in their corres-
ponding openings 34 to 37 of the template. As shown in FIG.
2, edge 41 of the central portion 38 "cuts across" openings
36 and 37, while the other edge 42 of the central portion 38
"cuts across" openings 3~ and 35. The template 32 with the
components loaded therein is positioned proximate to the
board 20 in a direction substantially parallel thereto by
means of a programmable manipulator 43, e.g. a robotic arm,
operating under a computer control terminal 44. The
programmable manipulator 43 is of a type capable of lifting
a predetermined load comprising the releasable template 32
and the various components loaded therein, and of locating
the template with sufficient accuracy proximate to the board
such that each component is positioned near its corresponding
location on the board. A commercially available programmable
manipulator of the foregoing type is, for examp]e, the PUMA
(trade mark) Model 560 robotic arm manufactured by Unimation
Inc. of Danbury, Connecticut.
Once the loaded template 32, which is held by
manipulator 43 at its wrist 45, is positioned proximate to
the board 20, the template portions 38, 39 and 40 are
separated from each other. This is achieved by laterally
displacing portions 39 and 40 away from the central portion
38, as schematically shown by the directional arrows on the
template portions 39 and 40. This results in the enlargement
of openings 34 to 37, and in a simultaneous release o~ the
components 25 to 28 out of their respective openings 34 to
37 onto the surface of the board 20. The releasable template
32 is maintained in its parallel position proximate to the
board 20 for a delay period. During a portion of such delay
period, each component which is placed on the surface of the
board 20 is confined within its corresponding opening in the
template 32. In other words, the template openings prevent
each component from moving away from its corresponding
aperture pattern on the vibrating board. At the end of the
delay period, the template is withdrawn above the highest
component inserted
119~:~3'12~
on the board, and is thus ready for anew loading cycle on a
new empty board.
The foregoing operational steps of the embodiment
of FIG. 2 are illustrated in a flow chart configuration
shown in FIG. 3. This flow chart diagram is given herein
as one example for controlling and programming the
programmable manipulator 43 to achieve the components
mounting process in accordance with an embodiment of the
invention. It is considered that those skilled in the art
would be capable of programming the manipulator to interact
with the various hardware elements of this illustrative
embodiment.
At the outset, the system is started with the
START instruction of block 50. Next, an empty board 20 is
mounted on the base 22 as shown by the ACQUIRE EMPTY
BOARD 20 instruction in block 51. The vibration mechanism
29 is turned on thus imparting a vibratory motion to board
20 as per block 52. Next, the template 32 which is held by
the manipulator 43 at its wrist 45, is "closed" by means of
a control instruction given to the manipulator from its
control terminal 44. Such control instruction of block 53
is of the type of a close hand, close grippers, or close
fingers instruction available on most commercially
available robotic arms. Subsequent to instruction block
53, the empty template 32 is closed, i.e., central portion
38 is brought in intimate contact with the two coplanar
outer portions 39 and 40, and the template openings 34 to
37 are now reduced or smaller than in their "open"
position.
The loading of the template 32 with the
respective components 25 to 28 to be mounted may be
achieved manually or automatically by means of an
appropriate component feeding mechanism. Subsequent to the
loading step of block 54, the template 32 is positioned
proximate and parallel to the board 20 by directing the
wrist 45 of the manipulator 43 to a predetermined
coordinate space position relative to the base 22. This is
~199~
g
achieved in block 55 by feeding the programmable
manipulator 43, via the control terminal 44, with-a desired
location in space for its wrist 45. Nex~, the template 32
is opened by means of a control instruction such as open
hand, open grippers or open fingers instruction thereby
releasing the components 25 to 28 to be mounted out of
their now enlarged openings 34 to 37 onto the surface of
the vibrating board 20. Subsequent to the opening of the
template 32 as per block 56, the template is maintained in
its parallel position proximate to the board 20 for a
period of time until the components are inserted, as shown
by block 57. During the latter, the components to be
mounted on the board 20 are confined within their
respective template openings until their leads are inserted
in their corresponding apertures 21 on the board. The
foregoing`period of time may be fixed, or may be responsive
to sensing means indicative of the insertion state of the
respective components.
Shown in block 58 is the next step in the process
which consists of withdrawing the open template 32 above
the highest inserted component on the board 20 in order not
to disengage any of the mounted components. The remaining
blocks 59, 60 and 61 of the process are self explanatory in
that the loaded board 20 is now to be removed and any new
empty board is to be mounted on the base 22 prior to
repeating the foregoing series of steps.
Another embodiment of the invention is
schematically shown in FIG. 4 wherein the programmable
robotic arm 43 of FIG. 2 is used to simultaneously mount a
plurality of multilead components on a board 70. The
latter is transported to a work station 71 by means of a
conveyor 72. Work station 71 is illustratively of a
vibratory type. Such a vibratory station 71 is capable of
oscillating in a first direction 73, a second direction 74,
or in any other direction resulting from any combination of
the first and second directions 73 and 74. The board 70 is
temporarily secured to the vibratory work station 71, and a
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-- 10 --
vibratory motion is thus imparted to the board in
accordance with an embodiment of the invention. A
releasable template 75 comprising two coplanar portions 76
and 77 has a plurality of openings 78, 79, 80 and 81
adapted to receive a corresponding plurality of components
(not shown) to be mounted on board 70. As shown, the
template 75 is held at the wrist 45 of the programmable
robotic arm 43. In order not to obstruct the drawings,
further structural details of the releasable template 75,
such as its opening and closing mechanisms, are not shown
in FIG. 4 but will be described in connection with FIG. 5.
Illustratively shown in FIG. 4 is a components feeding
arrangement 82 comprising a plurality of differently shaped
feeding tubes 83, 8~ and 85. Each one of the feeding tubes
83 to 85, which acts as a source of multilead components to
be mounted, must be of a type capable of delivering one
component at a time at a preselected speed or rate
depending upon the overall speed requirements of the
components mounting process.
In accordance with an embodiment of the
invention, the releasable template 75 is loaded with the
component or components to be mounted by locating one of
its openings, e.g., 78, adjacent to the feeding tube 83,
and by transferring a component out of tube 83 into opening
78 of template 75. During such an operation, template
portions 76 and 77 are held together such that the
component transferred into opening 78 is held within such
opening by means of a pair of retaining protrusions or lips
(not shown) similar to the one described above in
connection with FIG. 2. In order to transfer a component
out of the template 75, template portions 76 and 77 are
"separated" from each other thereby enlarging opening 78
and releasing the component out of its corresponding
openingO
The loading of the releasable template 75 with
the plurality of components to be mounted on board 70 is
illustratively accomplished by first locating each opening
il~.'3'~'h~
11 -
78 to 81 underneath its corresponding feeding tube 83, 84
or 85. Next, the components to be mounted are transferred
from their respective feeding tubes to their corresponding
matching openings of the template 75. Preferably, the
loading of the releasable template 75 is achieved by
sequentially locating each one of its openings underneath
the appropriate feeding tube and by sequentially
transferring the components out of the feeding tubes. The
placing of the components on the board 70 is achieved by
positioning the components-loaded-template 75 in
substantially parallel spaced relation to the board 70 at
predetermined coordinate positions with respect thereto,
and by simultaneously releasing the components out of their
respective openings 78 to 81 of the template onto the
board. The positioning of the template 75 by means of the
programmable robotic arm 43 may be substantially aided by
using a set of auxiliary~locating devices, e.g., tapered
pins 86 and 87, attached to a non-vibrating portion 88 of
the work station 71 and adapted to be inserted in mating
apertures 89 and 90 of one portion (e.g., 77) of the
releasable template 75.
The various operational steps of the embodiment
of FIG. 4 are illustrated in a flow chart configuration
shown in FIG. 5. This flow chart diagram is given herein
as one example for controlling and programming the
programmable manipulator 43 to achieve the components
mounting process in accordance with this embodiment of the
invention. It is considered that those skilled in the art
would be capable of programming the manipulator to interact
with the various hardware elements of this illustrative
embodiment. The flow chart of FIG. 5 is similar to the one
described in FIG. 3, and comparable functional and
programming steps in the former have the same reference
numerals as their counterpart in the latter. In accordance
with the embodiment of FIG. 4, the loading of the template
75 is achieved by locating an unfilled template opening
beneath the feeder (block 91), transferring a component
~:~9942~
- 12 -
from the feeder onto the template opening (block 92), and
repeating the foregoing two steps (block 93) until the
template is fully loaded. The remaining operational steps
of this flow chart, i.e., steps 50 to 53 and 55 to 61, are
similar to the corresponding steps described above in
connection with FIG. 3.
FIG. 6 illustratively shows a releasable template
100 in its "open" or released position in accordance with a
further illustrative embodiment in the invention. The
releasable template 100 may be used in the above
embodiments of FIGS. 2 and 4 as a substitute for templates
32 and 75, respectively. For purpose of illustration only,
releasable template 100 is shown as having two coplanar
portions 101 and 102. However, releasable templates having
more than two portions, such as template 32 of FIG. 2, are
well within the spirit and scope of the present invention.
As shown in ~IG. 6~ template portion 101 has a plurality of
indentations 103', 104', 105' and 106' along an edge 107
thereof. Similarly, template portion 102 has also a
plurality of indentations 103" , 104'', 105'', and 106 "
along an edge 108. The two coplanar template portions 101
and 102 are positioned with respect to each other to form a
plurality of resulting openings 103, 104, 105 and 106
respectively comprising the combination of indentations
103' and 103'', 104' and 134'', 105' and 105'', and 106'
and 106':. Opening 105, adapted to receive a circular
component, comprises a reference notch 109. The latter
enables a proper positioning of a circular co~ponent (not
shown) within the template by aligning the notch with a
corresponding reference key located on the housing of the
component.
The overall dimensions of these openings 103 to
106 in their "closed" position are selected to be somewhat
larger than the dimensions of the outer bodies of the
components to be mounted. Each opening, e.g., 103,
comprises a pair of retaining protrusions or lips 110 and
111, adapted to hold a corresponding component within such
il~g'~
- 13 -
opening. These retaining lips 110 and 111 are best shown
in the cross sectional view of FIGo 7. Also, the
respective locations of the openings 103 to 106 within
template 100 are selected to substantially correspond to
the intended locations of the components on the board on
which they are to be inserted.
As mentioned above in connection with the
embodiment of FIG. 4, in order to faci]itaté the
positioning of the template 100 with respect to a board,
portion 101 of the template 100 comprises a pair of
locating apertures 112 and 113. The positions and shapes
of these apertures 112 and 113 are selected to match those
of a pair of mating locating pins (such as 86 and 87 in
FIG~ 4) attached to a non-vibrating portion of the work
station. In a preferred embodiment of the invention, both
the locat-ing pins (not shown) and their mating apertures
112 and 113 are tapered, thereby substantially aiding the
positioning step of the template.
One arrangement for coupling template portion 101
to template portion 102 may comprise two pairs of permanent
magnets of which only one pair of magnets 114 and 115,
respectively embedded in opposite cavities 116 and 117
within template portions 101 and 102, is shown. The
magnets 114 and 115 are poled to repel each other thereby
causing a repulsion force between template portions 101 and
102. In other words, the repulsion force generated by the
two magnets 114 and 115 causes the edges 107 and 108 to
normally separate from each other resulting in the somewhat
enlarged openings 103 to 106 when the template is in its
"open" position. ~ther means for generating a repulsion
force between portions 101 and 102 may be used, e.g., a
spring arrangement or dual acting air cylinders inserted in
cavities 116 and 117 of template portions 101 and 102 may
be used to repel portions 101 and 102 from each other.
The coupling arrangement further comprises a pair
of fastening bolts 118 and 119 attached to a coupling bar
o~
- 14 -
120 by means of a pair of nuts 121 and 122, respectively.
Fastening bolts 118 and 119 are slidably engaged with at
least one of the two template portions 101 and 102 in order
to permit their coplanar relative movement when the
template is to be opened or closed. Fastening bolt 119 is
engaged in passages 123 and 124 of template portions 101
and 102, respectively. Similarly, fastening bolt 118 is
also engaged with the two template portions. Since the
coupling bar 120 is held against the template portion 102
the tightening or loosening of the nuts 121 and 122 will
control the maximum distance or gap between edges 107 and
108, and in turn will control the dimensions of the
openings 103 to 106 when the releasable template is in its
"open" or released position. As mentioned above, th~
repulsive permanent magnets 114 and 115 will insure that
the foregoing distance or gap between the edges 107 and 108
is maintained. The releasable template 100 may be held
from a portion 125 thereof, the latter being dimensioned
and adapted to be coupled to the wrist of the programmable
robotic arm of the type described above in connection with
FIGS. 2 and 4. However, holding the releasable template
from any other part or portion thereof will not affect its
operation provided that the two coplanar template portions
101 and 102 are not simultaneously held by the robotic arm.
The closing of releasable template 100 is
achieved by coupling an actuator 126 to the bar 120 such
that a displacement output cylinder 127 of the actuator is
positioned against the template portion 102. Actuator 126
may be an electrical solenoid, an air cylinder, or any
other well known device capable of displacing a cylinder or
small shaft in response to a control signal. The template
close/open control signal corresponds to the close/open
hand or grippers signal usually available on programmable
robotic arms. The close template control signal causes the
actuator 126 to push its output cylinder 127 against
template portion 102 and to close the template 100 by
forcing the edge 108 of portion 102 against the edge 107 of
3'~
- 15 -
portion 101. In other words, since the template portion
101, the bolts 118 and 119, and the coupling bar 120 are
coupled together, template portion 102 is the only part of
the template coupling arrangement capable of moving in
response to the force exerted by cylinder 127. Opening or
releasing of the template 100 is achieved by removing the
control signal applied to the actuator 126 thus retracting
its cylinder 127 and returning the template portion 102 to
its initial position away from template portion 101 due to
the repulsive force generated by permanent magnets 114 and
115.
Shown in FIG. 7 is an end cross-sectional view of
template 100 of FIG. 6 along line 7-7 thereof. The
retaining protrusions or lips 110 and 111 are dimensioned
such that a multilead component to be mounted is retained
within its corresponding template opening 103 when the
template 110 is in its "closed" position. In the "open"
position of the template 100, as shown in FIG. 7, the lips
110 and 111 are separated from each other thereby enabling
the multilead component to be released out of its opening
onto a board.
The above-described coupling principles are
readily applicable to releasable templates comprising more
than two coplanar template portions. For example, in the
embodiment of FIG. 2, the releasable template 32 comprises
the central template portion 38 and the two outer template
portions 39 and 40. The coupling between the central
portion 38 and the outer portion 3g may be achieved by
positioning in each one of these two template portions,
along their common edge 41, a pair of permanent magnets.
The magnets in the central portion 38 are poled to repel
those in the outer portion 39. Similarly, the coupling
between the central portion 38 and the outer portion 40 may
be achieved by positioning in each one of these portions 38
and 40, along their common edge 42, a pair of permanent
magnets. The latter in central portion 38 are poled to
repel the magnets in outer portion 40. Thus, due to the
119~
- 16 -
presence of these repelling magnets, a gap is formed on
each side of the central portion 38 along its edges 41 and
42. Furthermore, a pair of fastening bolts, a coupling bar
and a selectively energizable actuator of the type
described above, would enable the "opening" and "closing"
of the three portion releasable template 32 in a similar
way as the one described above in connection with the two-
portion releasable template 100.
The foregoing illustrative embodiments have been
presented merely to illustrate the pertinent inventive
concepts of the present invention~ Numerous modifications
can be made by those skilled in the art without departing
from the spirit and scope of the invention~
