Device for bonding wire leads in electronic components

There is disclosed an improved device for bonding wires in electronic components, of the type comprising a member for moving the capillary to a location close to the bonding area or region and an ultrasonic transducer including an arm carrying on one end the capillary, the transducer being pivoted to the approach member and having associated therewith a linear motor controlled by a position transducer.

The invention relates to an improved device for bonding wires in electronic 
components. 
BACKGROUND OF THE INVENTION 
Currently available devices for bonding electronic component wires may be 
basically reduced to two types: a first type, which is called 
"translatory" type hereiin and is shown diagramatically in FIG. 1, and a 
second type, called "rotary" type herein and is shown diagramatically in 
FIG. 2. Both devices perform the same operations under the drive of a 
single motor, but having different layouts in principle and exhibit 
different advantages and disadvantages. 
For a given installed drive power, the translatory type device of FIG. 1 is 
slower than the rotary type device of FIG. 2, since larger reciprocating 
masses are involved therein, but, at the same time, it affords a higher 
degree of accuracy in bonding than the rotary type device. This is 
especially true where the bonding points are located at different 
elevations. In fact, with the rotary device, its capillary movement 
follows, in use, an arc of a circle which--in view of the minute extent of 
the movements involved--may be likened to a straight segment of a line. 
Where the bonding spots are located at different elevations, by contrast, 
the circular character of the path of movement becomes increasingly more 
significant as the difference between such elevations increases, and the 
capillary is positioned offset with respect to the perpendicular to the 
locus, thus effecting an incorrect soldered joint. The present invention 
reconciles speed and accuracy of operation. In accordance with the 
invention a motor is effective to bring, where required, the capillary 
rapidly as close as feasible to the bonding spot, the capillary being 
driven through the final portion of its stroke by a cam which can impart 
the capillary with the motion directly ahead of and during the bonding 
step. The latter device, having two degrees of freedom, while driving the 
capillary gently and accurately at a high rate, cannot change the motion 
in situations that may require it, unless the cam is replaced with another 
cam having a more appropriate profile to the occasion; this is specially 
true of instances where successive soldered joints are to be made at 
different elevations. 
It is an object of this invention to provide an improved device for bonding 
wires leads in electronic components, which can operate at as fast a rate 
as a device of the rotary type, as accurately as a device of the 
translatory type, and afford a degree of flexibility in operation such as 
not even modern cam devices can afford. 
This and other objects of the invention will become apparent to be skilled 
ones from the description which follows and appended claims. 
An improved device for bonding electronic components wires, according to 
the invention, is of a type which comprises a member for fast approaching 
the capillary to the solder spot, and an ultrasonic transducer including 
an arm carrying said capillary on one end, said transducer being mounted 
pivotally on said fast approach member, and is essentially characterized 
in that associated with said transducer is a linear motor having its field 
magnet rigidly attached to said fast approach member and its field coil 
associated with said transducer.

Throughout the drawing views, including those showing prior devices, like 
parts are designated with the same reference numerals. 
DETAILED DESCRIPTION 
With particular reference to FIGS. 3 and 4, this device, as generally 
indicated at 1, comprises a bearing structure 2 whereto a motor 3 is 
mounted which drives a connecting rod/crank linkage 4 acting on a first 
frame 5 through roller guides 4'. Said first frame 5 has a pivot point 6 
whereat a second frame 7 and third frame 8 are pivotally connected. Rigid 
with the frame 5 is a static winding 9 of a position transducer, generally 
indicated at 10, of the Linear Variable Differential Transformer (LVDT) 
type, as well as a pair of magnets 11 of a linear motor, generally 
indicated at 12. The moving element 13 of the position transducer 10 and a 
coil 14 of the linear motor 12 are made associated with the frame 8 which 
has, at a remote location from the linear motor 12, an arm 15 supporting 
an electromagnet 16 and related plunger rod 17, and a first portion 18 of 
a contact 19. 
More specifically, the coil 14 has a square or rectangular cross-sectional 
configuration with the turns lying on parallel planes perpendicularly to 
the plane of motion of the capillary 23. It follows that, the current and 
magnetic flux define a plane coincident with that of the capillary 23, 
thereby the resulting force will be at all times directed into said plane. 
The magnets 11 have parallelepipedal configurations and extend on parallel 
planes to said capillary plane of action, and are housed in an iron holder 
11' having a middle portion 11" around which the coil 14 is located. 
The second portion 20 of the contact 19 is carried on the frame 7 forming a 
support for an ultrasonic transducer 21 which carries, on a first end 
thereof, a coil 22, and on the second end thereof, a capillary 23 
wherethrough a wire 24 forming the material to be bonded extends. Provided 
between the frames 7 and 8 is a spring 25 whose function will be explained 
hereinafter. 
In operation, energization of the electromagnet 16 results in its plunger 
rod 17 moving forward to lock the frame 7 to the frame 8 and close the 
contacts 18 and 20. The operation of the motor 3, via the connecting rod 
and crank 4, drives the frame 5 downwards to bring the pivot point 6 level 
with the bonding spot C. That downward movement of the frame 5 results in 
a correponding displacement of the frames 7 and 8, owing to the latter 
being also pivoted at 6 and locked together package-like; such 
package-like locking is necessary in order to prevent incidental relative 
movements of the frames 7 and 8 as the capillary 23 is being approached to 
the bonding spot C and consequent sudden stop at the desired close 
distance. The electromagnet may be now de-energized to release the frames 
7 and 8 which hold, however, the contacts 18 and 20 closed on account of 
the action of spring 25. 
Energization of the linear motor 12 results in a rotation of the frame 8 
and, via the spring 25, of the frame 7 as well, thereby causing the 
capillary 23 to move through the final close up distance. On the capillary 
23 contacting the bonding spot C, the contacts 18 and 20 are opened and 
the spring 25, by resisting the opening of said contacts, provides the 
required bonding pressure for the capillary 23. 
The opening of the contacts 18 and 20 may be used as a signal to energize 
the coil 22 and effect the bonding by ultrasonic effect. The travel 
distance of the linear motor 12, and accordingly the rotation of the 
transducer 21, is controlled by the position transducer 10 which is 
controlled, in turn, by an electronic unit, of suitable design and known 
per se, which is not shown and is not pertinent to this invention. 
On completion of the bonding at the spot C, the device 1 is conventionally 
moved over to a second bonding spot C' shown in FIG. 3 at a lower 
elevation than the spot C. In order to accomodate the difference in 
elevation between the spots C and C', the motor 3 is again operated to 
bring the pivot point 6 to a position level with the spot C', and the 
above-listed sequence of operations are reiterated. 
The linear motor 12 controls the movement of the capillary 23, which takes 
sequentially place as follows: 
up to form the loop in the wire; 
down to the second bonding region; 
up, after completing the second bond, to determine the next wire length to 
form a ball known as the "tail"; 
up to pass the electrode under the tail; 
down to the following region of first bond. 
Through appropriate programming of the electronic unit, it would, of 
course, possible where necessary to combine the movements controlled by 
the motors 3 and 12 so as to increase the device rate of operation.