U.S. patent number 3,773,240 [Application Number 05/231,843] was granted by the patent office on 1973-11-20 for automatic bonding machine.
This patent grant is currently assigned to Texas Instruments Incorporated. Invention is credited to Richard Heim.
United States Patent |
3,773,240 |
Heim |
November 20, 1973 |
AUTOMATIC BONDING MACHINE
Abstract
A machine for attaching connecting wires to connection points of
a semiconductor component and to connection points of a housing
which is to accommodate the semiconductor component is comprised of
a wire guide which is vertically adjustable with respect to the
semiconductor component and to the housing and through which a wire
is fed and a support which is adjustable in two dimensions parallel
to the plane of a semiconductor component and which carries either
the housing with the semiconductor component or the wire guide. The
machine also includes a programme carrier which may be advanced
step by step into successive detent positions and which have guide
members which cooperate with a complementary guide member on a
driver connected to an adjustable support and are so arranged that
in each detent position a guide member of the programme carrier is
disposed from a stationary reference point a distance which in
magnitude and direction is in a predetermined relationship to the
distance of a connection point from a reference point of the
housing of the semiconductor component. The guide members of the
programme carrier are conical bores, the driver is a rocker
pivotally mounted on the adjustable support and the guide member of
the driver is a guide cone. Because of the cooperation of the guide
members on the programme carrier and the guide member on the
driver, the adjustable support is automatically brought into the
positions in which the guide lies exactly above a connection point
of the housing or of the semiconductor component.
Inventors: |
Heim; Richard (Moosburg,
DT) |
Assignee: |
Texas Instruments Incorporated
(Dallas, TX)
|
Family
ID: |
22870838 |
Appl.
No.: |
05/231,843 |
Filed: |
March 6, 1972 |
Current U.S.
Class: |
228/4.5; 29/748;
228/7 |
Current CPC
Class: |
H01R
43/02 (20130101); B23K 11/0026 (20130101); H01L
24/78 (20130101); B23K 20/005 (20130101); H01L
24/85 (20130101); H01L 2224/45124 (20130101); H01L
2224/78901 (20130101); H01L 2224/85203 (20130101); H01L
2924/01079 (20130101); H01L 2224/85205 (20130101); H01L
2224/85203 (20130101); H01L 2224/85205 (20130101); H01L
2224/45144 (20130101); H01L 24/45 (20130101); H01L
2924/01006 (20130101); H01L 2224/45124 (20130101); H01L
2224/45144 (20130101); H01L 2224/78301 (20130101); Y10T
29/53213 (20150115); H01L 2224/45144 (20130101); H01L
2924/01013 (20130101); H01L 2924/00014 (20130101); H01L
2924/00014 (20130101); H01L 2924/01033 (20130101); H01L
2224/45124 (20130101); H01L 2224/85 (20130101); H01L
2924/01005 (20130101); H01L 2924/00014 (20130101); H01L
2924/00015 (20130101); H01L 2924/00014 (20130101); H01L
2924/00 (20130101); H01L 2924/00015 (20130101); H01L
2224/48 (20130101); H01L 2924/00 (20130101) |
Current International
Class: |
B23K
11/00 (20060101); B23K 20/00 (20060101); H01L
21/00 (20060101); H01R 43/02 (20060101); B23k
037/04 () |
Field of
Search: |
;228/1,3,4,6,7
;29/23B,23D,23MW,624,576S,576R,577,470.1,471.1 ;219/78 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Overholser; J. Spencer
Assistant Examiner: Craig; Robert J.
Claims
What is claimed is:
1. A machine for attaching connection wires to connection points of
a semiconductor component and to connection points of a housing
accommodating the semiconductor component comprising:
a. a wire guide member through which connection wire is fed, said
wire guide member being vertically adjustable with respect to said
semiconductor component and said housing;
b. an adjustable support member having a driver member including a
guide member fixed thereto, said adjustable support member being
adjustable in two dimensions parallel to the plane of said
semiconductor component for selectively carrying said housing with
said semiconductor component or said wire guide member; and
c. a programme carrier having a plurality of guide members
complementary to and engageable with the guide member on said
driver member, said programme carrier being advanceable
step-by-step into successive detent positions and the plurality of
guide members of said programme carrier being positioned such that
in each detent position at least one of said plurality of guide
members is disposed from a stationary reference point a distance
which in magnitude and direction is in a predetermined relationship
to the distance of a connection point from a reference point of the
housing of said semiconductor component.
2. The machine according to claim 1 wherein the guide members of
said programme carrier are conical bores and said guide member of
the driver member is a cone shaped guide member.
3. The machine according to claim 1 wherein said driver member is a
rocker member pivotally mounted on said adjustable support
member.
4. The machine according to claim 1 wherein said adjustable support
member is a compound table.
5. The machine according to claim 1 wherein said programme carrier
is a rotatably mounted rigid disc.
6. The machine according to claim 1 including a detent mechanism
for fixing the programme carrier in each detent position.
7. The machine according to claim 6 including means for imparting a
predetermined slight displacement to said programme carrier in each
detent position.
8. The machine according to claim 6 wherein said detent mechanism
comprises:
a. a leaf spring fixedly clamped at one end and having a stop
member provided with a notch at its other end;
b. a plurality of detent elements fixed to said programme carrier,
said detent elements being successively engageable in said notch to
define respective detent positions; and
c. means for selectively bending said leaf spring a predetermined
amount wherein said stop member is selectively displaced to change
the position of said notch and the detent element engaged
therein.
9. The machine according to claim 1 wherein said adjustable support
member carries said wire guide member and wherein said housing with
said semiconductor component is held immovable during the
attachment of said connection wires.
10. The machine according to claim 9 including an index strip
advanceable step-by-step, said index strip providing means for
carrying a plurality of housings with semiconductor components.
11. The machine according to claim 9 wherein said driver member
includes a further complementary guide member and said machine
includes a second adjustable support member adjustable parallel to
the plane of said semiconductor component, said second adjustable
support member being connected to a manipulator and including at
least one guide memmber which cooperates with said further
complementary guide member of said driver member.
12. The machine according to claim 11 including a brake for locking
said second adjustable support member.
13. The machine according to claim 11 wherein said second
adjustable support member is a compound table.
14. The machine according to claim 11 including a light spot
projector connected to said second adjustable support member for
directing a light spot onto said semiconductor component wherein
said guide member on said second adjustable support member is
positioned in a manner that by cooperation of the guide member on
said second adjustable support member with said further
complementary guide member of said driver member the said guide
member brings said wire guide member into coincidence with said
light spot.
15. The machine according to claim 11 including a second programme
carrier having a plurality of guide members, said second programme
carrier being advanceable step-by-step into successive detent
positions and the plurality of guide members of said second
programme carrier being positioned such that in each detent
position at least one of said plurality of guide members is
disposed from a reference point linked to the second adjustable
support member a distance which in magnitude and direction is in a
predetermined relationship to the distance of a connection point of
the semiconductor component from a reference point of said
component.
16. The machine according to claim 15 wherein said second programme
carrier is a rigid disc rotatably mounted on said second adjustable
support member.
17. The machine according to claim 11 wherein said driver member is
a rocker member pivotally mounted on said adjustable support
member.
18. The machine according to claim 17 wherein said rocker member
includes two oppositely directed guide members arranged such that
on the pivoting of said rocker member said oppositely directed
guide members come into engagement alternately with a guide member
of the programme carrier and with a guide member of said second
adjustable support member.
Description
The invention relates to a machine for attaching the connecting
wires to the connection points of a semiconductor component and of
the housing accommodating the semiconductor component, comprising a
wire guide which is vertically adjustable with respect to the
semiconductor component and to the housing and through which a wire
is fed and a support which is adjustable in two dimensions parallel
to the plane of the semiconductor component and which carries
either the housing with the semiconductor component or the wire
guide.
At the end of the fabrication process semiconductor components,
more especially integrated semiconductor circuits, are usually
enclosed in standardised housings which are provided with terminal
pins or terminal wires. After securing the semiconductor component
in the housing and before final sealing of the latter, the
electrical connection between the connection points of the
semiconductor component and the terminals of the housing must be
established. For this purpose thin connecting wires are attached at
one end to a connection point of the semiconductor component and at
the other to a connection point of the housing. Because of the very
small size of the semiconductor components the attaching of the
connecting wires, also known as "bonding" is a very difficult
operation which it has hitherto not been possible to automate and
which hitherto had to be carried out by skilled workers
manually.
For the connecting wires a thin gold or aluminum filament is
generally used which is fed from a coil through a capillary of the
wire guide. This filament is usually attached to the connection
points by welding using thermocompression or ultrasonic
methods.
By suitable vertical movement of the capillary the filament is
pressed against a connection point of the semiconductor component
and welded. The filament is then led in an arc to the corresponding
connection point of the housing by simultaneously raising the
capillary and displacing the semiconductor component and is also
welded at this connection point. By raising the capillary the
filament is then torn off or burnt off and prepared for the
attachment of the next connecting wire.
In the known machines of the type referred to at the beginning the
adjustable support is connected to a manipulator by means of which
an operator observing the operation through a stereo microscope
displaces the housing with the semiconductor component relatively
to the wire guide until the latter is positioned exactly above the
desired connection point of the housing or of the semiconductor
component. The operator then initiates a welding operation.
Thereafter the wire guide is again raised and the operator
displaces the adjustable support by means of the manipulator until
the wire guide is disposed above the corresponding connection point
of the housing. If double welding at one connection point is
necessary the same operation is repeated with a slight displacement
of the adjustable support. Thereafter the wire is torn or burnt off
and with the aid of the manipulator the operator can then locate
the next connection point on the semiconductor component, whereupon
the operation is repeated.
In these known machines, apart from the usual secondary operations
such as threading, attaching component parts, etc., the operator
has above all to carry out the difficult and tedious location and
approach of the various connection points. These operations take up
a considerable amount of time of skilled personnel and result in
poor utilisation of the machine capacity.
The invention is based on the problem of providing a machine of the
type indicated at the beginning which largely automates the
attachment of the connecting wires and substantially reduces the
necessary production time.
The machine according to the invention comprises a programme
carrier which may be advanced step-by-step into successive detent
positions and which comprises guide members which cooperate with a
complementary guide member on a driver connected to the adjustable
support and are so arranged that in each detent position a guide
member of the programme carrier is disposed from a stationary
reference point a distance which in magnitude and direction is in a
predetermined relationship to the distance of a connection point
from a reference point of the housing of the semiconductor
component.
In the machine according to the invention due to the cooperation of
the guide members on the programme carrier and of the guide member
on the driver the adjustable support is automatically brought into
the positions in which the wire guide lies exactly above a
connection point of the housing or of the semiconductor component.
Thus, for each type of semiconductor component a programme carrier
need only be made once; the connection points are indicated on said
carrier by the position of the guide members. For a given type of
semiconductor component to be fabricated the associated programme
carrier is inserted into the machine. It is then merely necessary
to bring the housings with the semiconductor components disposed
therein successively into a fixed reference position. The guide
member on the driver is then brought in succession into engagement
with the guide members of the programme carrier and as soon as the
guide members have aligned themselves with each other the
corresponding welding operation may be initiated. The connecting
wire is thus automatcally welded to the correct point.
The guide members of the programme carriers may for example be
conical bores, the guide member of the driver then being a conical
projection. When the conical projection extends into a conical bore
the driver displaces the adjustable support until the conical
projection is exactly concentric with the conical bore.
According to a preferred embodiment of the invention the programme
carrier is a rotatably mounted rigid disc which can be brought
successively into the different detent positions by simple
rotation.
A detent mechanism is preferably provided for fixing the programme
carrier in each detent position. To obviate the necessity of
providing two separate guide members on the programme carrier for
double weldings means are preferably provided with which a
predetermined slight displacement may be imparted to the programme
carrier in each detent position, said displacement corresponding
exactly to the desired distance between the two weld points of the
double welding.
According to a preferred embodiment of the invention this may be
achieved in that the detent mechanism comprises a leaf spring which
is fixedly clamped at one end and at the other end carries a stop
member engaging in notches in the programme carrier, and in that
means are provided for producing a predetermined bending of the
leaf spring.
If in a machine of the type described above the guide members were
arranged on the programme carrier in such a manner that they
corresponded alternately to the position of a connection point on
the semiconductor component and to the position of a connection
point on the housing, it would be possible with the aid of a single
programme carrier to apply all the necessary weld points completely
automatically. However, this would require that all the
semiconductor components are disposed in their housing in an
exactly defined position relatively to said housing. At the present
stage of the art this cannot be achieved in practice.
A further development of the machine according to the invention
therefore resides in that a second support is provided which is
adjustable parallel to the plane of the semiconductor component,
connected to a manipulator and carries at least one guide member
which cooperates with a further complementary guide member of the
driver.
This further development makes it possible to compensate for the
different positions of the semiconductor components relatively to
ther housings by means of the manipulator.
A brake is preferably provided for locking the second adjustable
support. This brake enables the second adjustable support to be
locked when the desired setting is reached. If the second guide
member of the driver then engages in the guide member of the second
adjustable support the cooperation of the guide members brings the
first adjustable support into the position fixed by the setting of
the second adjustable support.
A first embodiment of this further development resides in that a
light-spot projector is connected to the second adjustable supoort
and directs a light spot onto the semiconductor component, and that
on the second adjustable support a single guide member is arranged
in such a manner that by cooperation with the further complementary
guide member of the driver it brings the wire guide into
coincidence with the light spot.
In this embodiment an operator is necessary in order to bring the
light spot into coincidence with the connection points on the
semiconductor component; on the other hand, the connection points
on the housing are automatically located by the programme carrier.
This results in a substantial reduction in the operating time
compared with hitherto known machines because the location of the
next connection point with the aid of the light spot may be carried
out during the time in which the connecting wire is being welded to
the connection point of the housing. The operating time is thus
determined in practice solely by the machining time because the
location times, which have in any case been cut by half, coincide
with the machining times.
According to another embodiment it is however alternatively
possible to fully automate the operation in this case. This is
achieved in that on the second adjustable support a second
programme carrier is arranged which may be advanced step-by-step
into consecutive detent positions and on which a plurality of guide
members are so arranged that in each detent position of the second
programme carrier one of its guide members is disposed from a
reference point linked to the second adjustable support a distance
which in magnitude and direction is in a predetermined relationship
to the distance of a connection point of the semiconductor
component from a reference point of the semiconductor
component.
In this preferred embodiment of the machine two programme carriers
are provided for each production type of semiconductor component,
one of which carriers designates the position of the connection
points of the housing and the other of which designates the
position of the connection points of the semiconductor component.
For fabrication of a given type of semiconductor component the two
associated programme carriers are inserted into the machine. The
manipulator only serves the purpose of adjusting the two programme
carriers after placing a housing with the semiconductor component
contained therein in the machine in such a manner that the mutual
position of the semiconductor component and the housing is taken
into account. For this purpose the guide member of the driver is
first brought into engagement with a guide member of the second
programme carrier and using the manipulator the operator then sets
the two adjustable carriers coupled by the guide members in such a
manner that the wire guide is positioned exactly over the
corresponding connection point of the semiconductor component. The
second adjustable support is then locked by means of the brake and
the attachment of the connecting wires may then be carried out
completely automatically, the driver being brought in each case
alternately into engagement with a guide member of the one
programme carrier and a guide member of the other and the programme
carriers being further turned in the meantime in each case by one
detent position. On completion of a semiconductor component and
after introduction of the next semiconductor component into the
machine the brake is released, the position of the second
adjustable support corrected using the manipulator and the second
adjustable support then again locked with the brake.
Examples of embodiments of the invention are illustrated in the
drawings wherein:
FIG. 1 shows a schematic side view of a machine according to the
invention;
FIG. 2 is a partially sectioned front view to a somewhat larger
scale of the essential components of the machine of FIG. 1;
FIG. 3 is a plan view of the machine of FIGS. 1 and 2; and
FIG. 4 shows a plan view and a sectional view of a perforated disc
used in the machine of FIGS. 1-3.
The machine shown in the drawings comprises a frame 1 carrying the
various parts of the machine. Disposed on the frame 1 is a table 2
on which a housing with the semiconductor component disposed
therein may be fixed in a mounting 3 in an exactly defined working
position. For example, for series production the housings may be
attached to an index strip which is advanced step-by-step so that
each time one housing is brought into the working position on the
table 2. This operation can be observed in the usual manner by the
operator with the aid of a stero microscope 4.
Above the table 2 is a wire guide 5 comprising a capillary 6
through which is led a thin gold or aluminum filament which comes
from a coil 7 and from which the connecting wires between the
connection points of the housing and the connection points of the
semiconductor component are formed. The wire guide 5 is mounted on
the end of a support 8 which is mounted for pivotal movement about
a horizontal pivot axis 9. By drive means (not illustrated) the
support arm 8 may be pivoted and the wire guide 5 thus vertically
adjusted so that the capillary 6 may be raised from or lowered onto
the housing with the semiconductor component therein disposed on
the table 2.
The pivot axis 9 is mounted on a compound table 10 which is
adjustable in a horizontal plane in two mutually perpendicular
coordinate directions. By moving the compound table 10 it is
therefore possible to position the capillary 6 on any desired point
of the housing or of the semiconductor component mounted in the
housing. The compound table 10 thus performs the function of an
adjustable support for the wire guide 5.
As shown in FIG. 2 there is mounted on the frame 1 of the machine a
vertical bearing column 11 on which a hollow shaft 12 is rotatably
mounted by means of ball bearings 13, 14. At the upper end the
hollow shaft 12 comprises a shoulder 15 on which is detachably
mounted a circular perforated disc 16. Detent pins 17 are mounted
spaced uniformly along the edge of the perforated sic in such a
manner that a small portion of said pins projects from the upper
side of the disc 16 and a substantially larger portion projects
downwardly from the lower side of said disc 16. The downwardly
projecting portion of each detent pin is adapted to engage in a
notch 18 provided in a stop member 19 mounted on the free end of a
leaf spring 20 whose other end is clamped to a member of the frame
1. The perforated disc 16 can thus assume a number of defined stop
positions in each of which a detent pin 17 is in the notch 18. The
perforated disc 16 may be rotated by an indexing mechanism 21
step-by-step from one position to the next. The indexing mechanism
comprises an indexing push member 21 which carries at the front end
a resilient sheet metal strip 23 whose front edge engages the
portions of the pins 17 which project above the upper side of the
disc 16. By means of a drive mechanism 24, for example a pneumatic
or hydraulic cylinder or an electromagnet, the indexing push member
may be set in linear reciprocating movement. During the forward
movement thereof the front edge of the resilient sheet metal strip
engages the pin disposed in the notch 18, the disc 16 thereby being
rotated until the next pin 17 is engaged in the notch 18. The
indexing push member is then pulled back and the disc 16 has then
been advanced to the next stop position.
The perforated disc is provided with a plurality of guide members
in the form of conical bores 25 which are each associated with one
of the detent pins so that in each stop position one conical bore
is disposed in a predetermined working position. A rocker 26 is
mounted on the compound table 10 for pivotal movement about a
horizontal axis 27. Secured to the rocker 26 is a pneumatic or
hydraulic drive cylinder 28 whose piston rod 29 is pivotally
connected to the frame 1. The rocker 26 can thus be pivoted about
the axis 27 by actuating the drive cylinder 28.
Mounted at the front end of the rocker 26 is a downwardly
projecting guide cone 30. The arrangement is such that the guide
cone is positioned exactly above the location which is assumed by
the conical bore 25 of the disc 16 disposed in the working
position. When the rocker 26 is swung downwardly by the drive
cylijnder 28 the guide cone 30 enters said conical bore; the
inclined surfaces of the conical bore 25 and of the guide cone 30
cooperate to provide an automatic centering effect until the guide
cone 30 is finally disposed exectly centrally of the conical bore
25. This automatic alignment is made possible because the compound
table 10 is freely movable in all directions in the horizontal
plane and is therefore able together with the rocker 26 as a rigid
structure to follow the movements of the guide cone 30 and finally
assumes a position which is determined by the location of the
corresponding conical bore 25 in the perforated disc 16. Since the
compound table 10 entrains in turn the wire guide 5 the capillary 6
finally also assumes above the housing or the semiconductor
component disposed therein a position which is fixed by the
location of the conical bore 25 in the perforated disc 16.
As can be seen from FIG. 4 the conical bores 25 are at different
distances both from the center of the perforated disc 16 and from
the radii passing through the center of the detent pins 17. These
distances are dimensioned for a given semiconductor component to be
fabricated in such a manner that they correspond exactly to the
location of the connection points for the connecting wires.
Supposing for example that a predetermined reference point is
present on the housing of the semiconductor component and is
brought on the table 2 into an exactly defined position. There is
then also on the frame 1 a reference point through which the axis
of the guide cone 30 passes when the capillary 6 is set exactly to
the reference point of the housing. Each conical bore 25 is
provided in the disc 16 in such a manner that in the working
position it is spaced from said reference point of the frame a
distance which in magnitude and direction corresponds exactly to
the distance of a connection point for the connecting wire from the
reference point of the housing. When the guide cone 30 is aligned
by entering said conical bore the capillary 6 is displaced above
the housing by the corresponding distance and in a direction which
brings it to rest above the corresponding connection point.
The perforated disc 16 thus represents a programme carrier on which
the location of the connection points of the connecting wires of a
given semiconductor component is represented by the different
locations of the conical bores 25.
The connecting wires may be attached using the machine described
above in the following manner:
Before production is started the perforated disc 16 corresponding
to the semiconductor component to be provided with connections is
mounted on the hollow shaft 12. The first housing with the
semiconductor component mounted therein is placed on the table 2 in
such a manner that the reference point of the housing is disposed
at the prescribed location. By means of the drive cylinder 28 the
guide cone 30 is then introduced into the first conical bore 25 of
the disc 16. The compound table 10 and thus also the capillary 6
are thereby displaced corresponding to the location of said conical
bore. As soon as the guide cone has reached the central position in
the conical bore the wire guide 5 is moved downwardly so that the
capillary 6 is placed on the corresponding connection point. The
wire end is then welded, for example by thermocompressive or
ultrasonic methods, and if necessary, the wire is severed by
tearing or burning off.
The drive cylinder 28 is then actuated in the opposite direction so
that it pivots the rocker 26 upwardly and the guide cone 30 leaves
the conical bore 25. By means of the indexing mechanism 21 the
perforated disc 16 is rotated one step until the next detent pin 17
engages in the notch 18. The rocker 26 is thereafter again moved
downwardly so that the guide cones 30 enters the next conical bore
25. Corresponding to the different location of this conical bore
the capillary 6 is moved over the next connection point and the
next bonding may be carried out.
In many cases the connecting wire has to be connected to a
connection point of the housing by a double weld comprising two
closely adjacent weld points. For this purpose the capillary 6 must
be displaced a slight distance after the first welding. This is
done in very simple manner by utilizing the resiliency of the leaf
spring 20. For this purpose there is provided on the machine frame
a mechanism 31 comprising a push member 32 directed towards the
center of the leaf spring 19. Said push member is displaced
linearly by a drive member 33 (pneumatically, hydraulically or
magnetically). The drive member 33 is actuated after completion of
the first weld of a double weld, the guide cone 30 being held in
the same conical bore. The drive member 33 presses the push member
32 against the center of the leaf spring 20 so that the latter is
bent a predetermined amount. This bending slightly displaces the
stop member 19 which via the corresponding detent pin 17 entrains
the perforated disc 16 so that the latter is turned a slight
amount. During this turning the guide cone 30 in the conical bore
is entrained and displaces the compound table 10 and thus also the
capillary 6 a corresponding small distance. This distance is
dimensioned to correspond exactly to the spacing between the two
weld points of a double weld.
With the machine described above it would be theoretically possible
to attach the connecting wires to all the connection points of the
housing and of the semiconductor component completely
automatically. For this purpose it would merely be necessary to
associate the conical bores 25 of the disc 16 alternately with a
connection point of the housing and a connection point of the
semiconductor component. The capillary 6 would then be constantly
reciprocated alternately between these connection points.
However, at the present state of the art this is not possible in
practice because a requirement is that all the semiconductor
components are in the same exactly defined position in their
housings. Such precision cannot be obtained without excessive
costs. The machine illustrated in the drawings is therefore
provided with additional means for taking account of the different
locations of the semiconductor components with respect to their
housings.
For this purpose there is mounted on the frame 1 of the machine a
second compound table 34 which is adjustable independently of the
first compound table 10 likewise in two mutually perpendicular
coordinate directions in a horizontal plane. In the example of
embodiment illustrated the compound table 34 is disposed exactly
beneath the upper compound table 10, although this is of course not
absolutely essential. The compound table 34 is connected via a
linkage 35 to a manipulator 36 so that by actuation of the latter
said table may be brought into any desired position. Furthermore, a
brake 37 is provided with which the table 34 may be locked in any
desired position. For this purpose a brake plate 38 is mounted on
the table 34 and extends between a fixed brake shoe 38 and a
movable (for example pneumatically, hydraulically or magnetically
actuated) brake shoe 40. When the movable brake shoe 40 is pressed
against the fixed brake shoe 39 the brake plate 38 is clamped and
the lower compound table 34 thus locked.
Mounted on the lower compound table 34 is a support 41 which
comprises an arm 42 extending over the upper compound table 10 and
the members carried thereby.
Mounted at the free end of the arm 42 is a light-spot projector 43
which is arranged in such a manner that the light spot thereof may
be directed onto the semiconductor component disposed on the table
2. Also attached to the support 41 is a rigid arm 44 which projects
over the end of the rocker 26 and is provided with a conical bore
45 which widens downwardly and cooperates with an upwardly directed
second guide cone 46 of the rocker 26. The conical bore 45, the
second guide cone 46 and the light-spot projector 43 are arranged
in such a manner that the capillary 6 is disposed exactly above the
light spot projected by the projector 43 when the guide cone 46 is
centered in the conical bore 45.
In this embodiment of the machine the disc 16 comprises only the
conical bores corresponding to the connection points of the housing
and the setting of the capillary 6 to the connection points of the
semiconductor component is carried out by the operator using the
light-spot projector 43 and the stereo microscope 4 in the
following manner:
When the rocker 26 is moved downwardly and the guide cone 30
engages in the first conical bore 25 of the disc 16 the capillary 6
is located on the first connection point of the housing. The end of
the connecting wire may then be welded in the usual manner to this
point. During this operation the operator can use the manipulator
36 to adjust the second compound table 34 as desired and thereby
direct the light spot projected by the projector 43 onto the
desired next connection point of the semiconductor component,
observing this operation with the stereo microscope. As soon as the
light spot is directed to the desired connection point the operator
actuates the brake 37, thus locking the lower compound table 34.
Upon completion of the welding operation the drive cylinder 28 is
actuated in such a manner that the rocker 26 is pivoted upwardly
and the upper guide cone 46 enters the conical bore 45. The
inclined surfaces of the conical bore and of the guide cone provide
automatic centering and this correspondingly displaces the upper
compound table 10 and thus the capillary 6. When the guide cone 46
is central in the conical bore 45 the capillary 6 is exactly above
the light spot, i.e., above the desired next connection point. The
next welding operation can thus be immediately initiated. During
this operation the disc 16 is advanced one step and as soon as the
welding operation is completed the rocker 26 is again pivoted
downwardly the capillary 6 thus automatically being set to the next
connection point of the housing. The operator can now release the
brake again and set the light spot to the next connection point of
the semiconductor component. The advantage of this solution is that
firstly the operator need only carry out half the settings because
the setting to the connection points of the housing is effected
automatically by the disc 16 and secondly the settings which do
have to be made by the operator may be carried out while other
machine operations are in progress so that no machining time is
lost on these setting operations. The operating time is thus
substantially limited to the machining time necessary in any
case.
In FIGS. 2 and 3 a modification of this second embodiment is
illustrated in dot-dash line which enables the necessary manual
operations to be still further reduced and to locate the connection
points on the semiconductor component completely automatically as
well, even if the locations of the semiconductor components in
their housings differ.
In this embodiment there is no light-spot projector 43 and instead
of the arm 44 with the single conical bore 45 a holder 47 is
mounted on the support 41 and carries a bearing 48 for a second
perforated disc 49. The disc 49 is constructed in the same manner
as the disc 16; it carries at the periphery detent pins 50 which
each engage in an associated conical bore 51. Furthermore, for the
second perforated disc an indexing mechanism 52 is provided which
is constructed in the same manner as the indexing mechanism 21 of
the first disc 16. A stop member 53 cooperating with the pins 50
holds the second disc 49 in its stop positions.
In this case the first perforated disc 16 again comprises the
conical bores associated with the connection points of the housing
whereas the conical bores 51 provided in the second disc 49
represent the location of the connection points on the
semiconductor component. The second guide cone 46 is retained on
the rocker 26 and the upper disc 49 is arranged in such a manner
that in each stop position one of its conical bores 51 is disposed
in the operating position above said second guide cone 46.
Imagining again a reference point fixedly connected to the lower
compound table 34, the various conical bores 51 are disposed in the
disc 49 in such a manner that they are spaced from said imaginary
reference point in the operating position a distance which in
magnitude and direction corresponds to the distance of the
corresponding connection point on the semiconductor component from
a fixed reference point of said component.
In this embodiment the connecting wires are attached in the
following manner: When the housing with the semiconductor component
disposed therein has been mounted in the correct location on the
table 2 the rocker 26 is pivoted upwardly by means of the drive
cylinder 28 so that the upper guide cone 46 is centered in the
first bore 51 of the disc 49, said bore being disposed in the
operating position. The operator then uses the manipulator 36 with
the brake 37 released to bring the capillary 6 above the first
connection point of the semiconductor component corresponding to
said conical bore, observing this operation with the aid of the
stereo microscope 4. As soon as the capillary 6 is correctly set to
the first connection point the brake 37 is actuated to lock the
lower compound table 34. This setting of the table 34 is then
maintained for as long as the corresponding semiconductor component
is disposed in the machining position on the table 2 and the brake
35 is not released until the next semiconductor component in its
housing is brought into the machining position.
The first welding operation is then initated, the end of the
connecting wire being bonded to the connection point of the
semiconductor component which has been set by the operator.
Thereafter the rocker 26 is pivoted downwardly by means of the
drive cylinder 28 so that the lower guide cone 30 engages in the
first conical bore 25 of the lower disc 16. The capillary 6 is thus
automatically set to the first connection point of the housing.
While the connecting wire is welded to said connecting point the
uppr disc 49 is advanced one step. The rocker 26 is then again
pivoted upwardly so that the upper guide cone 46 engages in the
next conical bore 51 of the disc 49. The capillary 6 is thus
automatically set without the assistance of the operator to the
next connection point of the semiconductor component. These
operations repeat themselves completely automatically as necessary
until all the required connections have been made. Following this
the next semiconductor component is moved in its housing into the
machining position on the table 2 and the operator uses the
manipulator 36 with the brake 37 to adjust the position of the
upper disc 49 in accordance with the location of the new
semiconductor component in its housing.
Since in this embodiment of the machine the operator's attention is
required only for short periods a substantial saving of personnel
is possible because one operator can for example attend several
machines. Apart from the initial setting for each semiconductor
component the operations are completely automatic. The individual
operations are controlled via a programme switching mechanism which
controls the correct time cycle of the advancing of the perforated
discs, the rocker actuation, the upward and downward movement of
the capillary, the welding operations, the severing mechanism,
etc.
The invention is not of course limited to the examples of
embodiment described and illustrated. For example, linearly
displaceable programme carriers may be provided instead of
rotatable perforated discs. Nor is it absolutely essential for the
cooperating guide members to consist of conical bores and guide
cones. In the examples of embodiment described and illustrated
there is a rigid connection between the guide members and the
capillary and consequently the movement of the latter is exactly
identical to the movement of the guide cones. It will of course
also be possible to provide a reduction gearing in the connection
between the guide members and the capillary to make the movement of
the guide members greater by a predetermined factor than the
movement of the capillary. The conical bores on the perforated
discs would then have to be at corresponding greater distances from
the reference points. This measure would in particular provide
greater accuracy for very small adjustments.
The diameter of the conical bores 25, 45 and 51 must of course be
sufficiently great to ensure that the tip of the guide cone 30 or
46 engages in the conical bore even for the greatest displacements
occuring. The necessary dimensions may be easily calculated from
the known distances between the connection points.
Furthermore, it is not absolutely essential for the guide members
whose cooperation effects the adjustment of the capillary to
comprise conical bores and guide cones. It is basically possible to
use any guide members with which such an adjustment can be
effected.
* * * * *